2011 Vol. 29, No. 6
Display Method:
2011, 29(6): 1023-1030.
Abstract:
To predict the quality of the low permeability reservoir of the Member 3 and Member 4 of the Quantou Formation in the Northern Songliao Basin, the diageneses of the clastic rocks were divided into early diagenetic stage A, early diagenetic stage B, middle diagenetic stage A1, middle diagenetic stage A21, middle diagenetic stage A22 and middle diagenetic stage B . The results of the statistical data show that diageneses have apparent controls on the physical property and oil saturation of the reservoirs, and the sand bodies of any sedimentary facies can not produce commercial oil and gas flows in middle diagenetic stage B, and only the porosity of main river channel sand bodies is higher than the porosity cutoff of commercial oil and gas reservoir. The diagenetic stages of the Member 3 and Member 4 of the Quantou Formation in the northern Songliao Basin were predicted using diagenetic numerical modeling technology. The reservoir quality of the Member 3 and Member 4 of the Quantou Formation is the result of integrated effects of sedimentary facies and diageneses. The reservoir types and quality distribution of the Member 4 of the Quantou Formation laterally were predicted by overlap the sedimentary facies map on the diagenetic stage prediction map. The commercial oil and gas well mainly located in the reservoirs of type Ⅲ3, Ⅲ4 and Ⅲ5 in Central Depression of the northern Songliao Basin, where will be the potential exploration area of the Member 4 of the Quantou Formation in the basin.
To predict the quality of the low permeability reservoir of the Member 3 and Member 4 of the Quantou Formation in the Northern Songliao Basin, the diageneses of the clastic rocks were divided into early diagenetic stage A, early diagenetic stage B, middle diagenetic stage A1, middle diagenetic stage A21, middle diagenetic stage A22 and middle diagenetic stage B . The results of the statistical data show that diageneses have apparent controls on the physical property and oil saturation of the reservoirs, and the sand bodies of any sedimentary facies can not produce commercial oil and gas flows in middle diagenetic stage B, and only the porosity of main river channel sand bodies is higher than the porosity cutoff of commercial oil and gas reservoir. The diagenetic stages of the Member 3 and Member 4 of the Quantou Formation in the northern Songliao Basin were predicted using diagenetic numerical modeling technology. The reservoir quality of the Member 3 and Member 4 of the Quantou Formation is the result of integrated effects of sedimentary facies and diageneses. The reservoir types and quality distribution of the Member 4 of the Quantou Formation laterally were predicted by overlap the sedimentary facies map on the diagenetic stage prediction map. The commercial oil and gas well mainly located in the reservoirs of type Ⅲ3, Ⅲ4 and Ⅲ5 in Central Depression of the northern Songliao Basin, where will be the potential exploration area of the Member 4 of the Quantou Formation in the basin.
2011, 29(6): 1031-1040.
Abstract:
The standstone reservoir in the Upper Paleozoic Shan23 of YuxingzhuangZizhou area is domoninated by quartz sandstone lithoclastic quartz sandstone and lithic sandstone. Currently, the reservoir is in the late diagenetic stage B or C period. The diagenesis includes burial compaction, pressolution,silica cementation,carbonate cementation and replacement, kaolinite cementation, and dissolution. Through the core observations and thin section analyses, combining with cathodoluminescence Xray diffraction and scanning electronmicroprobe studies, six types of diagenetic facies are identified in the Shan23 Formation in the eastern Ordos Basin. They are weak compactionsiliceous cementation facies, weak compaction kaolinite cementation facies,weak compactionstrong siliceous cementation facies, matrix filling facies severe compaction facies, carbonate cementation and replacement facies. Furthermore the planar superimposition was made and the favorable diagenetic facies for reservoir development was determined. Matrix filling facies,severe compaction facies, carbonate cementation and replacement facies is the worst,weak compaction kaolinite cementation facies,weak compactionstrong siliceous cementation facies ,the porosity and permeability generally lower ,weak compactionsiliceous cementation facies has the best physical property, intergranular pore types, intergranular dissolution pores, intragranular dissolved pore. The weak compactionsiliceous cementation facies determined the favorable diagenetic facies belt of the Shan23 Formation. Highquality reservoirs in the Shan23 Formation are distributed in Zizhou area.
The standstone reservoir in the Upper Paleozoic Shan23 of YuxingzhuangZizhou area is domoninated by quartz sandstone lithoclastic quartz sandstone and lithic sandstone. Currently, the reservoir is in the late diagenetic stage B or C period. The diagenesis includes burial compaction, pressolution,silica cementation,carbonate cementation and replacement, kaolinite cementation, and dissolution. Through the core observations and thin section analyses, combining with cathodoluminescence Xray diffraction and scanning electronmicroprobe studies, six types of diagenetic facies are identified in the Shan23 Formation in the eastern Ordos Basin. They are weak compactionsiliceous cementation facies, weak compaction kaolinite cementation facies,weak compactionstrong siliceous cementation facies, matrix filling facies severe compaction facies, carbonate cementation and replacement facies. Furthermore the planar superimposition was made and the favorable diagenetic facies for reservoir development was determined. Matrix filling facies,severe compaction facies, carbonate cementation and replacement facies is the worst,weak compaction kaolinite cementation facies,weak compactionstrong siliceous cementation facies ,the porosity and permeability generally lower ,weak compactionsiliceous cementation facies has the best physical property, intergranular pore types, intergranular dissolution pores, intragranular dissolved pore. The weak compactionsiliceous cementation facies determined the favorable diagenetic facies belt of the Shan23 Formation. Highquality reservoirs in the Shan23 Formation are distributed in Zizhou area.
2011, 29(6): 1041-1047.
Abstract:
In the Cambrian formation of basin facies in the eastern Tarim Basin, thin bedded dolomicrites, argillaceous dolomicrites and siliceous dolomicrites are distributed in thick formations of silty mudstone, siliceous mudstone and silicalite. There is no obvious evidence of tideflat where evaporative pumping dolomicrites can be formed, like bird's eye structure, pores formed by gypsum disolution, cryptalgalaminite and mudcracks, while there are many evidence of deepwater environments, such as Radiolaria, colour of strong oxygenfree environment. As a result, the mechanism forming these dolomicrites can not be interpreted by evaporative pumping. Studies are carried on by petrologic characteristics, degree of order, isotope ratio of 13C ,18O and 87Sr/86Sr. Dolomicrites studied in this article appear in basin facies, composed by micrite dolomites, with mud intervals and siliceous metasomatism. In basin facies, the thickness of dolomicrites is small, while in ramp, they are distributed in dolomite with saccharoidal texture. Colour of cathodoluminescence of dolomicrites is maroon, which is characteristic of high quantity of Mn2+ and Fe2+, indicating that dolomicrites were formed in strong oxygenfree environment. Distribution range and average of degree of order of dolomite show that dolomicrites have lower value of degree of order than other dolomites. The average value of degree of order of dolomicrites is 0.749 8, with 48 samples, while that is 0.948 8(17 samples) of other dolomites, which means that dolomicrites were formed in relative short time. In deepwater environments, dolomicrites formed rapidly, there was no time to form big and euhedralgranular texture. Distribution range and average of δ13C and δ18O of dolomite shows that dolomicrites have higher value than other dolomites. The average value of δ13C of dolomicrites is 1.2, while that of finely crystalline dolomite is 0.4‰ and that of medium macrocrystalline dolomite is 0.6‰. The average value of δ18O of dolomicrites is 5.8‰, while that of finely crystalline dolomite is 8.8‰ and that of Medium macrocrystalline dolomite is 12.1‰. The characteristics of δ13C and δ18O show that dolomicrites were formed in circumstance with high salinity. The average value of 87Sr/86Sr of dolomicrites is 0.710 64, while that of finely crystalline and Medium macrocrystalline dolomite is 0.709 34, which is another evidence of circumstance with high salinity. Mechanism of dolomitization was proposed based on above evidences. Dolomicrites was formed in the period of restricted sea basin. When there was not sufficient supplement of freshwater into the sea and with strong evaporation, The salinity of seawater went high, with Mg2+ and Ca2+ concentrated. As a result, there is enough Mg2+ for dolomitization. For there were enough interspaces in the fluffy calcium carbonate sediments and seawater with high salinity can flows and stays sufficiently so that dolomitization occurred in penecontemporaneous diagenetic stage.
In the Cambrian formation of basin facies in the eastern Tarim Basin, thin bedded dolomicrites, argillaceous dolomicrites and siliceous dolomicrites are distributed in thick formations of silty mudstone, siliceous mudstone and silicalite. There is no obvious evidence of tideflat where evaporative pumping dolomicrites can be formed, like bird's eye structure, pores formed by gypsum disolution, cryptalgalaminite and mudcracks, while there are many evidence of deepwater environments, such as Radiolaria, colour of strong oxygenfree environment. As a result, the mechanism forming these dolomicrites can not be interpreted by evaporative pumping. Studies are carried on by petrologic characteristics, degree of order, isotope ratio of 13C ,18O and 87Sr/86Sr. Dolomicrites studied in this article appear in basin facies, composed by micrite dolomites, with mud intervals and siliceous metasomatism. In basin facies, the thickness of dolomicrites is small, while in ramp, they are distributed in dolomite with saccharoidal texture. Colour of cathodoluminescence of dolomicrites is maroon, which is characteristic of high quantity of Mn2+ and Fe2+, indicating that dolomicrites were formed in strong oxygenfree environment. Distribution range and average of degree of order of dolomite show that dolomicrites have lower value of degree of order than other dolomites. The average value of degree of order of dolomicrites is 0.749 8, with 48 samples, while that is 0.948 8(17 samples) of other dolomites, which means that dolomicrites were formed in relative short time. In deepwater environments, dolomicrites formed rapidly, there was no time to form big and euhedralgranular texture. Distribution range and average of δ13C and δ18O of dolomite shows that dolomicrites have higher value than other dolomites. The average value of δ13C of dolomicrites is 1.2, while that of finely crystalline dolomite is 0.4‰ and that of medium macrocrystalline dolomite is 0.6‰. The average value of δ18O of dolomicrites is 5.8‰, while that of finely crystalline dolomite is 8.8‰ and that of Medium macrocrystalline dolomite is 12.1‰. The characteristics of δ13C and δ18O show that dolomicrites were formed in circumstance with high salinity. The average value of 87Sr/86Sr of dolomicrites is 0.710 64, while that of finely crystalline and Medium macrocrystalline dolomite is 0.709 34, which is another evidence of circumstance with high salinity. Mechanism of dolomitization was proposed based on above evidences. Dolomicrites was formed in the period of restricted sea basin. When there was not sufficient supplement of freshwater into the sea and with strong evaporation, The salinity of seawater went high, with Mg2+ and Ca2+ concentrated. As a result, there is enough Mg2+ for dolomitization. For there were enough interspaces in the fluffy calcium carbonate sediments and seawater with high salinity can flows and stays sufficiently so that dolomitization occurred in penecontemporaneous diagenetic stage.
2011, 29(6): 1048-1057.
Abstract:
Based on the analysis of regional geology, and the discontinuity of stratum and lithology, the change of sedimentary facies, and the development of palaeouplifts, the transform stage of the regional depositiontectonics cycles changed from extension to compression began at the end of the early Ordovician in Tarim basin. The earlymiddle Ordovician Yingshan Formation platform margin began bending and downwelling which caused the deepening upward depositional cycles with middlelow energy reefbank complex along the margin. And it is favorable for the intraplatform beach development of Yingshan Formation in the western platform in Tarim basin, when the intraplatform ascending with morphologic prominence and lacking of platform margin barriers. Based on the well data, mediumhigh energy arene beaches are well developed with some of grit and oolitic beaches in intraplatform in Yingshan Formation, with 3~8 layers of multicycles deposition aggraded vertically, and lenticular or sheetlike pinchout and changed quickly laterally. The seismic response of intraplatform beaches of Yingshan Formation is different from the adjacent formation by wellseismic calibration. It displayed various mound and lenticular external shapes with lightly upper convex of the cap face and relatively even basal plane. The seismic wave of the most intraplatform beaches can be distinguished from the adjacent formation with weak reflection or chaotic reflection of top surface, but with discontinuous and strong reflection in case of thick mudstone cap formation, and with weak amplitude, discontinuous minor axis shape or chaotic reflection or disconnection strong wave. There are overlap and oblique reflection on the flank and thinning phenomenon of the overburden layer in the seismic section. The internal of most beaches have high frequency chaotic reflection, abnormaly strong and weak amplitude alternation, and some of them have multilayer crossing or progradation reflection which indicated multicycle beaches aggradation. On the basis of the characteristics of seismic facies, the formation thickness and seismic attributions, prediction and identification of Yingshan Formation intraplatform can be carried out in the western Tarim basin. By the regional seismic tracing and identification, there developed many large areas of intraplatform beaches in Yingshan Formation with blocklike shape horizontally and different size, most of the scales between 100 km2 and 300 km2, and the total area up to 12 000 km2. The intraplatform beaches mainly distributed in the southern slope of Tabei uplift, the northern slope of Tazhong uplift and the periphery of Hetihe gas field, most of which distributed along the slope of paleouplift. The Ordovician Yingshan Formation intraplatform beach, had better reservoirs with many types and wide distribution and great superimposd thickness, is favorable research aspect of potential exploration region of carbonate after the platform margin reefbank field found in Tarim basin. And more important discovery can be obtained in intraplatform beaches along the favorable accumulation slopes of palaeouplift by means of reservoirs seismic prediction to choose pay targets.
Based on the analysis of regional geology, and the discontinuity of stratum and lithology, the change of sedimentary facies, and the development of palaeouplifts, the transform stage of the regional depositiontectonics cycles changed from extension to compression began at the end of the early Ordovician in Tarim basin. The earlymiddle Ordovician Yingshan Formation platform margin began bending and downwelling which caused the deepening upward depositional cycles with middlelow energy reefbank complex along the margin. And it is favorable for the intraplatform beach development of Yingshan Formation in the western platform in Tarim basin, when the intraplatform ascending with morphologic prominence and lacking of platform margin barriers. Based on the well data, mediumhigh energy arene beaches are well developed with some of grit and oolitic beaches in intraplatform in Yingshan Formation, with 3~8 layers of multicycles deposition aggraded vertically, and lenticular or sheetlike pinchout and changed quickly laterally. The seismic response of intraplatform beaches of Yingshan Formation is different from the adjacent formation by wellseismic calibration. It displayed various mound and lenticular external shapes with lightly upper convex of the cap face and relatively even basal plane. The seismic wave of the most intraplatform beaches can be distinguished from the adjacent formation with weak reflection or chaotic reflection of top surface, but with discontinuous and strong reflection in case of thick mudstone cap formation, and with weak amplitude, discontinuous minor axis shape or chaotic reflection or disconnection strong wave. There are overlap and oblique reflection on the flank and thinning phenomenon of the overburden layer in the seismic section. The internal of most beaches have high frequency chaotic reflection, abnormaly strong and weak amplitude alternation, and some of them have multilayer crossing or progradation reflection which indicated multicycle beaches aggradation. On the basis of the characteristics of seismic facies, the formation thickness and seismic attributions, prediction and identification of Yingshan Formation intraplatform can be carried out in the western Tarim basin. By the regional seismic tracing and identification, there developed many large areas of intraplatform beaches in Yingshan Formation with blocklike shape horizontally and different size, most of the scales between 100 km2 and 300 km2, and the total area up to 12 000 km2. The intraplatform beaches mainly distributed in the southern slope of Tabei uplift, the northern slope of Tazhong uplift and the periphery of Hetihe gas field, most of which distributed along the slope of paleouplift. The Ordovician Yingshan Formation intraplatform beach, had better reservoirs with many types and wide distribution and great superimposd thickness, is favorable research aspect of potential exploration region of carbonate after the platform margin reefbank field found in Tarim basin. And more important discovery can be obtained in intraplatform beaches along the favorable accumulation slopes of palaeouplift by means of reservoirs seismic prediction to choose pay targets.
2011, 29(6): 1058-1068.
Abstract:
the second, fourth and sixth members of the Upper Triassic (Xujiahe) Formation in Sichuan basin are controlled by sandy sediments, with sand body characterized by large thickness and widespread distribution. To elucidate genesis of large area distribution of sand body brings great practical significance for the prediction of highquality reservoir distribution. Based on systematic work regarding sequence stratigraphic division, analysis of provenances, analysis of sand body distribution and workout of sedimentary facies maps, combined with study results of flume experiment and geological investigation, it is considered that Sichuan Basin was characterized by flat ancient landform, the development of multiple provenances and four dominant sedimentary systems (alluvial fan, fluvial system, deltaic system and lacustrine system) during Late Triassic. Of the four sedimentary facies, the fluvial deltaic sedimentary system has widespread distribution, relatively stable facies belts and uniform thickness; and lacustrine sedimentary system develops mainly in South Sichuan, with shallow lacustrine microfacies dominant and water outlet toward Southwest Sichuan Basin. The Upper Triassic of Sichuan Basin can be divided into 4 thirdorder sedimentary sequences, in which the second, fourth and sixth members of Xujiahe Formation are all located in the low stand tract system of each thirdorder sedimentary sequence, with the rate of sediment supply more than and equal to the rate of base level rising, and sufficient source supply as well. In addition, the three members can be subdivided into multiperiod fourthorder sedimentary sequences according to frequent transgression and regression of lake level. Distribution area of the Upper Triassic sand body in Sichuan Basin is controlled by three main factors: topographic slope, source supply and frequent transgression and regression of water body. By providing geological background, small topographic slopes not only cause widespread development of shallow water area, but also bring many changes of water flow (e.g. lateral erosion and flow pattern, etc.). Material guarantee can be assured by sufficient source supply. The existence of multipleprovenance system allows sand body entering into from various directions, and finally superimposing and connecting one another horizontally possible, and the increase of sandy sediment content, associated by transportation mechanism and lateral erosion difference of water flows, is very favorable for extending forward of sand body. Frequent transgression and regression of water body plays an important role in widespread development of sand body. During frequent transgression and regression of water body, owing to longterm strong reformation process of river, wave and coastal current, delta front experienced strong blanket deposition and expansion of development area.
the second, fourth and sixth members of the Upper Triassic (Xujiahe) Formation in Sichuan basin are controlled by sandy sediments, with sand body characterized by large thickness and widespread distribution. To elucidate genesis of large area distribution of sand body brings great practical significance for the prediction of highquality reservoir distribution. Based on systematic work regarding sequence stratigraphic division, analysis of provenances, analysis of sand body distribution and workout of sedimentary facies maps, combined with study results of flume experiment and geological investigation, it is considered that Sichuan Basin was characterized by flat ancient landform, the development of multiple provenances and four dominant sedimentary systems (alluvial fan, fluvial system, deltaic system and lacustrine system) during Late Triassic. Of the four sedimentary facies, the fluvial deltaic sedimentary system has widespread distribution, relatively stable facies belts and uniform thickness; and lacustrine sedimentary system develops mainly in South Sichuan, with shallow lacustrine microfacies dominant and water outlet toward Southwest Sichuan Basin. The Upper Triassic of Sichuan Basin can be divided into 4 thirdorder sedimentary sequences, in which the second, fourth and sixth members of Xujiahe Formation are all located in the low stand tract system of each thirdorder sedimentary sequence, with the rate of sediment supply more than and equal to the rate of base level rising, and sufficient source supply as well. In addition, the three members can be subdivided into multiperiod fourthorder sedimentary sequences according to frequent transgression and regression of lake level. Distribution area of the Upper Triassic sand body in Sichuan Basin is controlled by three main factors: topographic slope, source supply and frequent transgression and regression of water body. By providing geological background, small topographic slopes not only cause widespread development of shallow water area, but also bring many changes of water flow (e.g. lateral erosion and flow pattern, etc.). Material guarantee can be assured by sufficient source supply. The existence of multipleprovenance system allows sand body entering into from various directions, and finally superimposing and connecting one another horizontally possible, and the increase of sandy sediment content, associated by transportation mechanism and lateral erosion difference of water flows, is very favorable for extending forward of sand body. Frequent transgression and regression of water body plays an important role in widespread development of sand body. During frequent transgression and regression of water body, owing to longterm strong reformation process of river, wave and coastal current, delta front experienced strong blanket deposition and expansion of development area.
2011, 29(6): 1069-1078.
Abstract:
The Permian sandy conglomerates in Kebai area is one of the most important petroleum reservoir rocks in Junggar Basin. According to the result of the polarized microscope analysis of the diagenesis, authigenic mineral assemblage, pore characteristics of the clastic reservoir, and the study of scanning electron microscope(SEM), test of porosity and permeability, mud logging and well logging data, the type of rock and the diagenesis of Permian sandy conglomerates in the study area is studied. It suggests that the factors of influencing reservoir property in the study area are compaction, cementation and dissolution. In terms of the research on stage and characteristics of diagenesis, the Permian sandy conglomerate reservoirs in the study area are divided into seven diagenetic facies: 1) high maturestrong dissolution facies, 2) high maturestrong cementation facies, 3) high maturemiddle cementationmiddle dissolution facies, 4) high matureweak compression facies, 5) high maturestrong compression facies, 6) low matureweak compression facies,7) low maturestrong compression facies. Then, the conditions of diagenesis facies, the feature of diagenesis, the environment of diagenesis, model of diagenesis and evolutionary sequence of diagenesis are concluded and summarized. Furthermore, the reservoir properties of sandy conglomerate of different diagenesis facies is summarized. The main lithofacies belt and sedimentary facies zone of high quality reservoir development zones is predicted and described .
The Permian sandy conglomerates in Kebai area is one of the most important petroleum reservoir rocks in Junggar Basin. According to the result of the polarized microscope analysis of the diagenesis, authigenic mineral assemblage, pore characteristics of the clastic reservoir, and the study of scanning electron microscope(SEM), test of porosity and permeability, mud logging and well logging data, the type of rock and the diagenesis of Permian sandy conglomerates in the study area is studied. It suggests that the factors of influencing reservoir property in the study area are compaction, cementation and dissolution. In terms of the research on stage and characteristics of diagenesis, the Permian sandy conglomerate reservoirs in the study area are divided into seven diagenetic facies: 1) high maturestrong dissolution facies, 2) high maturestrong cementation facies, 3) high maturemiddle cementationmiddle dissolution facies, 4) high matureweak compression facies, 5) high maturestrong compression facies, 6) low matureweak compression facies,7) low maturestrong compression facies. Then, the conditions of diagenesis facies, the feature of diagenesis, the environment of diagenesis, model of diagenesis and evolutionary sequence of diagenesis are concluded and summarized. Furthermore, the reservoir properties of sandy conglomerate of different diagenesis facies is summarized. The main lithofacies belt and sedimentary facies zone of high quality reservoir development zones is predicted and described .
2011, 29(6): 1079-1085.
Abstract:
Block 12 Ordovician reservoir is one of the most important exploration and production area of Tahe oilfield in Tarim basin, however, it is a representative extralowporosity and extralow permeability reservoir and, results in much errors in delineating hydrocarbon zones, and so, it is very difficult to identify the reservoir by using conventional well logging data. Investigations of outcrops, cores and scanning electron microscope(SEM) images and well logging images data show that matrix rocks exist lots of fractures and caves. Furthermore, the fracture is a vital important element in Yijianfang and Yingshan groups, which has two primary effects, i.e. one is reserving space for formation liquid, the other is tunnel for hydrocarbon or water migration. The pore morphology, different size and uneven distribution of reserving spaces subsequently result in very strongly heterogeneous property, so it is vital to study the distribution law of fracture. This paper discussed the characteristics of the fractures, and analyzied the reason of fracture occurring, and the distribution law of fractures. This paper used sequence Gaussian randomizing methods to simulate the fracture parameters, such as porosity, permeability and opening. The threedimensional images of fracture parameters model shows heterogeneous of this reservoir. The simulation result shows that the fractures dramaticlly modify the permeability of the Ordovician reservoir, for the Block 12, the maximum fracture permeability up to 3008.781×103 μm2, and average value, 125.788×103 μm2, The result is in agreement with production data.
Block 12 Ordovician reservoir is one of the most important exploration and production area of Tahe oilfield in Tarim basin, however, it is a representative extralowporosity and extralow permeability reservoir and, results in much errors in delineating hydrocarbon zones, and so, it is very difficult to identify the reservoir by using conventional well logging data. Investigations of outcrops, cores and scanning electron microscope(SEM) images and well logging images data show that matrix rocks exist lots of fractures and caves. Furthermore, the fracture is a vital important element in Yijianfang and Yingshan groups, which has two primary effects, i.e. one is reserving space for formation liquid, the other is tunnel for hydrocarbon or water migration. The pore morphology, different size and uneven distribution of reserving spaces subsequently result in very strongly heterogeneous property, so it is vital to study the distribution law of fracture. This paper discussed the characteristics of the fractures, and analyzied the reason of fracture occurring, and the distribution law of fractures. This paper used sequence Gaussian randomizing methods to simulate the fracture parameters, such as porosity, permeability and opening. The threedimensional images of fracture parameters model shows heterogeneous of this reservoir. The simulation result shows that the fractures dramaticlly modify the permeability of the Ordovician reservoir, for the Block 12, the maximum fracture permeability up to 3008.781×103 μm2, and average value, 125.788×103 μm2, The result is in agreement with production data.
2011, 29(6): 1086-1097.
Abstract:
Data of seismic and bore hole show that the palaeotopography of the Triassic Chang 8 , in the lower part of the Yanchang Formation, Ordos basin, was possibly not "steep to the south while gentle to the north" style as the previous studies suggested, and large areas of bathyal or abyssal areas were also impossible in this age. The bed form of the lake was very gentle on the basin scale with the slope angle no more than 0.1° , or 2 m/km. The climate was possibly a little dry and the mildly brackish water with depth no more than 10m was the dominant media of the sediments. Vertical or high angel burrows and root systems, coal seams or coaly mudstones and plant fossils of Neocalamites are commonly inclusions either at the edge or in the center of the basin. Shallow lacustrine delta with the following characters were well developed in this basin at that time: 1) detrital components mostly mediumfine graded lithic arkose and feldspathic litharenite, 2）wide delta front with 80~100 km in length and uncovered frequently to the air, 3) sandstones mainly the subaqueous distributary channel deposits, 4) mouthbar and the gravity flow deposits being infrequent, 5) topsets, foresets and bottomsets of the Gilbert Delta not developed. Obvious difference of the slopes of the southern part and the northern part of the basin emerged in the early Chang 7, tightly following the Chang 8 in age. Triggered by the early Indosinian movement and the uplift of the west Qinling Mountains at the southwestern margin of the Ordos basin, the base of this basin was bended over unsymmetrically and the palaeotopography of the "steep to the south while gentle to the north" was generated. And from this time (Chang 7) to the end of the late Triassic slopebreaks and deltas with three elements of topsets, foresets and bottomsets were well developed in the basin.
Data of seismic and bore hole show that the palaeotopography of the Triassic Chang 8 , in the lower part of the Yanchang Formation, Ordos basin, was possibly not "steep to the south while gentle to the north" style as the previous studies suggested, and large areas of bathyal or abyssal areas were also impossible in this age. The bed form of the lake was very gentle on the basin scale with the slope angle no more than 0.1° , or 2 m/km. The climate was possibly a little dry and the mildly brackish water with depth no more than 10m was the dominant media of the sediments. Vertical or high angel burrows and root systems, coal seams or coaly mudstones and plant fossils of Neocalamites are commonly inclusions either at the edge or in the center of the basin. Shallow lacustrine delta with the following characters were well developed in this basin at that time: 1) detrital components mostly mediumfine graded lithic arkose and feldspathic litharenite, 2）wide delta front with 80~100 km in length and uncovered frequently to the air, 3) sandstones mainly the subaqueous distributary channel deposits, 4) mouthbar and the gravity flow deposits being infrequent, 5) topsets, foresets and bottomsets of the Gilbert Delta not developed. Obvious difference of the slopes of the southern part and the northern part of the basin emerged in the early Chang 7, tightly following the Chang 8 in age. Triggered by the early Indosinian movement and the uplift of the west Qinling Mountains at the southwestern margin of the Ordos basin, the base of this basin was bended over unsymmetrically and the palaeotopography of the "steep to the south while gentle to the north" was generated. And from this time (Chang 7) to the end of the late Triassic slopebreaks and deltas with three elements of topsets, foresets and bottomsets were well developed in the basin.
2011, 29(6): 1096-1104.
Abstract:
Several provenances deposition is the result of mixed deposition of detrital materials that came from different provenances and different types of parent rocks.We may neglect the diversity of different provenances if we simply analyse the indexes that can indicate the characteristic of mother rock by calculating the average value. So we should classify the samples which belong to the same provenance at first, then analyze the direction and characteristics of every provenance. This article discussed the provenance system characteristics of Yingcheng Formation in Shiwu fault depression by comprehensive analysis of clastic grain combination, heavy minerals combination, sandy conglomerate distribution, dip logging and other materials. Clastic grain combination can indicate parent rock characteristics of the provenance area, and clastic grain maturation can help to distinguish the transportation direction of fragmentary material. The authors determined three kinds of provenances by classification of the same provenance for clastic grain combination materials of all wells in the study area. The samples of the first kind provenance have the characteristics of " low quartz content, high feldspar and cuttings content, and magmatite is the main cuttings type"; the samples of the second kind provenance have the characteristics of " high quartz content, low cuttings content, and magmatite and metamorphic are the main cuttings types"; the samples of the third kind provenance have the characteristics of "quartz, feldspar, and cuttings' contents are nealy the same, and sedimentary and magmatite rock are the main cuttings types".Then the three provenance directions above have been determined, and the result are northern provenance, eastern provenance, and northwest provenance respectively. Heavy minerals analysis is also one of the methods of study provenance direction and parent rock characteristics. Three heavy minerals combination areas have been identified by heavy minerals content statistics and combination classification of study area. There are "high zircon content area" in the north, "zircon, garnet, and green shade stone combination area" in the east, and "zircon and garnet combination area" in the westnorth. They stand for the three provenance systems, respectively.These areas indicated that there were three provenance systems exist in Yingcheng Formation of Lishu area. The transport direction and path of detrital material that derived from provenance can be pointed out by analyzing sand bodies distribution characters, and the palaeocurrent can be indicated by dipmeter. It were found that there were high content regions of sandy conglomerate in the north, the east and the northwest of the research area, and the direction of sandy conglomerate content declining was the same as the direction of palaeocurrent that indicated by dipmeter. The results confirm three provenances which have been identified by analysis all above After analyzing all above, three provenance systems were identified in Shiwu area of Yingcheng Formation.The mother rock in the northwest provenance system are sedimentary rocks and magmatic rocks, mother rock in northern slope provenance is magmatic rocks and mother rock in eastern slope are magmatic rocks and metamorphic rocks. The forming and distribution of sand bodies in Yingcheng Formation of Shiwu area were jointly controlled by the three provenances all above. Consequently, hybrid sedimentation were formed under the control of "multiprovenance, differences existed between each other provenance, and the characteristics of every provenance were inherited between each phase” in Shiwu area.
Several provenances deposition is the result of mixed deposition of detrital materials that came from different provenances and different types of parent rocks.We may neglect the diversity of different provenances if we simply analyse the indexes that can indicate the characteristic of mother rock by calculating the average value. So we should classify the samples which belong to the same provenance at first, then analyze the direction and characteristics of every provenance. This article discussed the provenance system characteristics of Yingcheng Formation in Shiwu fault depression by comprehensive analysis of clastic grain combination, heavy minerals combination, sandy conglomerate distribution, dip logging and other materials. Clastic grain combination can indicate parent rock characteristics of the provenance area, and clastic grain maturation can help to distinguish the transportation direction of fragmentary material. The authors determined three kinds of provenances by classification of the same provenance for clastic grain combination materials of all wells in the study area. The samples of the first kind provenance have the characteristics of " low quartz content, high feldspar and cuttings content, and magmatite is the main cuttings type"; the samples of the second kind provenance have the characteristics of " high quartz content, low cuttings content, and magmatite and metamorphic are the main cuttings types"; the samples of the third kind provenance have the characteristics of "quartz, feldspar, and cuttings' contents are nealy the same, and sedimentary and magmatite rock are the main cuttings types".Then the three provenance directions above have been determined, and the result are northern provenance, eastern provenance, and northwest provenance respectively. Heavy minerals analysis is also one of the methods of study provenance direction and parent rock characteristics. Three heavy minerals combination areas have been identified by heavy minerals content statistics and combination classification of study area. There are "high zircon content area" in the north, "zircon, garnet, and green shade stone combination area" in the east, and "zircon and garnet combination area" in the westnorth. They stand for the three provenance systems, respectively.These areas indicated that there were three provenance systems exist in Yingcheng Formation of Lishu area. The transport direction and path of detrital material that derived from provenance can be pointed out by analyzing sand bodies distribution characters, and the palaeocurrent can be indicated by dipmeter. It were found that there were high content regions of sandy conglomerate in the north, the east and the northwest of the research area, and the direction of sandy conglomerate content declining was the same as the direction of palaeocurrent that indicated by dipmeter. The results confirm three provenances which have been identified by analysis all above After analyzing all above, three provenance systems were identified in Shiwu area of Yingcheng Formation.The mother rock in the northwest provenance system are sedimentary rocks and magmatic rocks, mother rock in northern slope provenance is magmatic rocks and mother rock in eastern slope are magmatic rocks and metamorphic rocks. The forming and distribution of sand bodies in Yingcheng Formation of Shiwu area were jointly controlled by the three provenances all above. Consequently, hybrid sedimentation were formed under the control of "multiprovenance, differences existed between each other provenance, and the characteristics of every provenance were inherited between each phase” in Shiwu area.
2011, 29(6): 1105-1114.
Abstract:
Triassic Yanchang Formation was the main oil bearing formation in the Ordos Basin, and Chang 10 oil layer was new layer for oil and gas exploration in the basin. According to data of outcrop, core observation, grain size analysis, and palaeogeomorphologic reconstruction, etc., the paper systematically investigated characteristics of sedimentary facies, depositional environment and sedimentary system in the lower Yanchang 10 interval. The result indicated that ①Chang 10 oil layer mainly developed alluvial fan and fluvial,and fluvial was chief types of sedimentary facies ; ②During Chang 10 stage, fluvial sedimentary system was typically controlled by the western and northern material source system, but was affected weakly by the southern material source system ; ③In Chang 10 period, Ordos region developed two types of meandering and braided rivers, and braided river sedimentary system mainly distributed in the middlewestern basin, meandering river sedimentary system was chiefly in the south of basin. ④ During Chang 10 stage, the Ordos area today was "discharge zone", then " collection area" may be located in the western Henan provincethe East Qinling, and its ancient geographical environment may be similar to the present Mississippi River; ⑤ Channel sands of Chang 10 were matched with lacustrine oil shales of Chang 9, which may form "the source rock on the reservoir" hydrocarbon accumulation assemblage in the longitudinal direction.
Triassic Yanchang Formation was the main oil bearing formation in the Ordos Basin, and Chang 10 oil layer was new layer for oil and gas exploration in the basin. According to data of outcrop, core observation, grain size analysis, and palaeogeomorphologic reconstruction, etc., the paper systematically investigated characteristics of sedimentary facies, depositional environment and sedimentary system in the lower Yanchang 10 interval. The result indicated that ①Chang 10 oil layer mainly developed alluvial fan and fluvial,and fluvial was chief types of sedimentary facies ; ②During Chang 10 stage, fluvial sedimentary system was typically controlled by the western and northern material source system, but was affected weakly by the southern material source system ; ③In Chang 10 period, Ordos region developed two types of meandering and braided rivers, and braided river sedimentary system mainly distributed in the middlewestern basin, meandering river sedimentary system was chiefly in the south of basin. ④ During Chang 10 stage, the Ordos area today was "discharge zone", then " collection area" may be located in the western Henan provincethe East Qinling, and its ancient geographical environment may be similar to the present Mississippi River; ⑤ Channel sands of Chang 10 were matched with lacustrine oil shales of Chang 9, which may form "the source rock on the reservoir" hydrocarbon accumulation assemblage in the longitudinal direction.
2011, 29(6): 1115-1121.
Abstract:
Standard sequence involve HST, TST, FSST and LST. Through analyzing the features of onlap points in the systems of standard thirdorder sequences, the onlap points of a standard sequence can be divided into five kinds,which are onlap points of LST, onlap points of TST, onlap points of early HST, onlap points of late HST and onlap points of FSST ；and bring forward the way of inverting lake level change history by counting onlap points in the sequence. Use this method, which can be used in conjunction with the features of stratigraphic section in Liaozhong depression,the Bohai Bay Basin;on the basis of dividing thirdorder sequences,count the onlap points and plot a coastal process curve and a lake level eustasy extent curve,and divide Oligocene into four lake level eustasy cycle, then, through contrasting the vertical variation of drilling sediment, we find that the lake level is highly confident curve, it also proves that the way of inverting lake level change by counting onlap points is practicable in the study of continental paleolimnology.
Standard sequence involve HST, TST, FSST and LST. Through analyzing the features of onlap points in the systems of standard thirdorder sequences, the onlap points of a standard sequence can be divided into five kinds,which are onlap points of LST, onlap points of TST, onlap points of early HST, onlap points of late HST and onlap points of FSST ；and bring forward the way of inverting lake level change history by counting onlap points in the sequence. Use this method, which can be used in conjunction with the features of stratigraphic section in Liaozhong depression,the Bohai Bay Basin;on the basis of dividing thirdorder sequences,count the onlap points and plot a coastal process curve and a lake level eustasy extent curve,and divide Oligocene into four lake level eustasy cycle, then, through contrasting the vertical variation of drilling sediment, we find that the lake level is highly confident curve, it also proves that the way of inverting lake level change by counting onlap points is practicable in the study of continental paleolimnology.
2011, 29(6): 1122-1129.
Abstract:
Through the comprehensive analysis of cores, well logs and seismic interpretation data, and under the guidance of the theory and technology of the highresolution sequence stratigraphy, the characteristics of the different grade sequence interface and marine flooding surface in the Lower Zhujiang Formation Miocene in Liwan31 Block are studied.In this paper, the sequence structure and distribution of the short sequence of deep water fan are discussed, and the sequence and time stratigraphic framework of main reservoir is established. The small sand body layers in stratigraphic framework of the Zhujiang Formation in the study area are isochronously correlated and wedged, and the reservoir developmental features of different baselevel cycles are discussed. It indicates that the canyon on the continental slope is an activity location of sedimentary process. The canyon was filled by sandy silt quickly in baselevel ascending phase. A majority of sediment was carried to much deeper sea area than the study area, and only little sediment preserved or even caused stratigraphic lacuna in the study area. The A/S value (the change of the accommodation space to sediment supply ratios) of short sequence increasing in a vertical direction, and it indicates that deepwater fan was moving towards to shore land. The moving of the main channel of deepwater fan is an important reason for the stratigraphic lacuna under the channel. The deposit in the deepwater fan channel is most active in baselevel initial ascending phase, characteristics as active progradation sequence that have downlap and onlap, and it will be beneficial to develop reservoir sand bodies. Effective accommodation space and deepwater fan moving towards to the source area accompany with sea level rising to the maximum flooding surface. It developed retrogradation sequence in this period and argillic layers grow in number because of the channel moving frequently. Variation of the accommodation space corresponding to baselevel ascending or descending is the major factor that control short baselevel cycle types and reservoir distribution in deep water fan system. Accompanying with sea level descending and effective accommodation space moving towards to the deepsea plain, sediment in the deepwater fan channel in the study area was carried to deeper sea area by gravity current, and it would be more beneficial to develop reservoir sand bodies to the south of Liwan 31 area. The results of GR inversion indicate that sandstone characteristics as strong wave trough amplitude and low wave impedance attribute. The sandbodys stretch in NS or NWSE directions. The channel sandbody developed in the northland of the study area while the mudstone of continental slope developed in the southland. The sand body distribution of deep water fan in different stage is described by sequencelithofacies paleogeographic mapping and GR inversion, and the temporal and spatial distribution model of channel sand body of deep water fan have been established. The results are useful in predicting sand body of deep water fan reservoir.
Through the comprehensive analysis of cores, well logs and seismic interpretation data, and under the guidance of the theory and technology of the highresolution sequence stratigraphy, the characteristics of the different grade sequence interface and marine flooding surface in the Lower Zhujiang Formation Miocene in Liwan31 Block are studied.In this paper, the sequence structure and distribution of the short sequence of deep water fan are discussed, and the sequence and time stratigraphic framework of main reservoir is established. The small sand body layers in stratigraphic framework of the Zhujiang Formation in the study area are isochronously correlated and wedged, and the reservoir developmental features of different baselevel cycles are discussed. It indicates that the canyon on the continental slope is an activity location of sedimentary process. The canyon was filled by sandy silt quickly in baselevel ascending phase. A majority of sediment was carried to much deeper sea area than the study area, and only little sediment preserved or even caused stratigraphic lacuna in the study area. The A/S value (the change of the accommodation space to sediment supply ratios) of short sequence increasing in a vertical direction, and it indicates that deepwater fan was moving towards to shore land. The moving of the main channel of deepwater fan is an important reason for the stratigraphic lacuna under the channel. The deposit in the deepwater fan channel is most active in baselevel initial ascending phase, characteristics as active progradation sequence that have downlap and onlap, and it will be beneficial to develop reservoir sand bodies. Effective accommodation space and deepwater fan moving towards to the source area accompany with sea level rising to the maximum flooding surface. It developed retrogradation sequence in this period and argillic layers grow in number because of the channel moving frequently. Variation of the accommodation space corresponding to baselevel ascending or descending is the major factor that control short baselevel cycle types and reservoir distribution in deep water fan system. Accompanying with sea level descending and effective accommodation space moving towards to the deepsea plain, sediment in the deepwater fan channel in the study area was carried to deeper sea area by gravity current, and it would be more beneficial to develop reservoir sand bodies to the south of Liwan 31 area. The results of GR inversion indicate that sandstone characteristics as strong wave trough amplitude and low wave impedance attribute. The sandbodys stretch in NS or NWSE directions. The channel sandbody developed in the northland of the study area while the mudstone of continental slope developed in the southland. The sand body distribution of deep water fan in different stage is described by sequencelithofacies paleogeographic mapping and GR inversion, and the temporal and spatial distribution model of channel sand body of deep water fan have been established. The results are useful in predicting sand body of deep water fan reservoir.
2011, 29(6): 1130-1137.
Abstract:
Taking the structural sequence stratigraphic analysis as the thread, through the study of architecture of faulted basin and regional paleogeomorphology change analysis, based on the geological and geophysical data, this paper analyses sequence stratigraphy of the main oil formation K1t, K1n and K1d1 of Low Cretaceous in Wuerxun Depression. Five isochronous sequence boundaries are identified by which regional well profiles are correlated, then the purpose layer sequence stratigraphic framework has been established. This study suggests that the sedimentary history of Wuerxun Depression includes a few stages corresponding with structural evolution. The pattern of strata filling and the structural of sequence are controlled by sag structure. Western steep slope of the depression, alluvial fan and fan delta are developed. But fine depositional system of fluvial delta and coastal shallow lake are developed in the eastern gentle slope of the depression. Among them, single fault bench type is developed as aggradational sequence sets pattern, single fault trough type is developed as aggradational or progradational sequence sets pattern, and single fault overlap type is similar developed as passive continental margin slope type sequences. Based on the tectonic paleogeomorphology and the sequence constitute analysis. Slump turbidities rock located in lowstand system tract of SQd1 is the main reservoir of northern Wuerxun Depression. It is lithologicstructural oil reservoir, rather than structural oil reservoir which at the top of K1n2 of predecessors.
Taking the structural sequence stratigraphic analysis as the thread, through the study of architecture of faulted basin and regional paleogeomorphology change analysis, based on the geological and geophysical data, this paper analyses sequence stratigraphy of the main oil formation K1t, K1n and K1d1 of Low Cretaceous in Wuerxun Depression. Five isochronous sequence boundaries are identified by which regional well profiles are correlated, then the purpose layer sequence stratigraphic framework has been established. This study suggests that the sedimentary history of Wuerxun Depression includes a few stages corresponding with structural evolution. The pattern of strata filling and the structural of sequence are controlled by sag structure. Western steep slope of the depression, alluvial fan and fan delta are developed. But fine depositional system of fluvial delta and coastal shallow lake are developed in the eastern gentle slope of the depression. Among them, single fault bench type is developed as aggradational sequence sets pattern, single fault trough type is developed as aggradational or progradational sequence sets pattern, and single fault overlap type is similar developed as passive continental margin slope type sequences. Based on the tectonic paleogeomorphology and the sequence constitute analysis. Slump turbidities rock located in lowstand system tract of SQd1 is the main reservoir of northern Wuerxun Depression. It is lithologicstructural oil reservoir, rather than structural oil reservoir which at the top of K1n2 of predecessors.
2011, 29(6): 1138-1144.
Abstract:
The deep burial sandstone reservoir quality is seriously affected by the carbonate cements which is an essential autogenic mineral in the Lower Crataceous formation in Jiudong sag. The thin sections and scanning electron microscope are analyzed, the energy spectroscopy ,carbon and oxygen isotopes of carbonate cements are tested. The study results indicate that the carbonate cements of Lower Crataceous sandstone from the Jiudong sag are mainly ferrous dolomite, ferrous calcite and dolomite with heterogeneous distribution and apparent zonation. They were formed in the late stage of diagenesis and the source are mainly derived from clay minerals transformation, thermal evolution of organic matter in the mudstone and the part of the calcium from the alteration of plagioclase. The key reason for development of the highquality reservoir in the deep burial lowpermeability reservoirs is the dissolution of carbonate cements. In addition, the content of carbonate cement also have an impact on reservoir quality, if the content is greater than 5%, with the increase of the content of carbonate cements the porosity decreases, while it's less than 5%, there is no obvious correlation between porosity and carbonate cement content.
The deep burial sandstone reservoir quality is seriously affected by the carbonate cements which is an essential autogenic mineral in the Lower Crataceous formation in Jiudong sag. The thin sections and scanning electron microscope are analyzed, the energy spectroscopy ,carbon and oxygen isotopes of carbonate cements are tested. The study results indicate that the carbonate cements of Lower Crataceous sandstone from the Jiudong sag are mainly ferrous dolomite, ferrous calcite and dolomite with heterogeneous distribution and apparent zonation. They were formed in the late stage of diagenesis and the source are mainly derived from clay minerals transformation, thermal evolution of organic matter in the mudstone and the part of the calcium from the alteration of plagioclase. The key reason for development of the highquality reservoir in the deep burial lowpermeability reservoirs is the dissolution of carbonate cements. In addition, the content of carbonate cement also have an impact on reservoir quality, if the content is greater than 5%, with the increase of the content of carbonate cements the porosity decreases, while it's less than 5%, there is no obvious correlation between porosity and carbonate cement content.
2011, 29(6): 1145-1155.
Abstract:
The Qinhuangdao area is located in the northeastern margin of the North China Block. The Liangjiashan and Majiagou Formation in this area are mainly composed of finegrained dolomitic limestone, finegrained dolomite, leopardlike limestone and calcirudite, which generally contain nodular, striped and lump cherts. XRD analyses show that the major minerals of the silicalite are quartz, calcite and some dolomite. The silicalite samples are wormlike, spherical and needlelike chalcedony aggregates with metasomatic structure in some of them under the microscope. The silicalites are poor in Mn and Fe, with Si / (Si + Al + Fe) ratios of 0.98 0.99, low ∑REE, and very weak negative Ce anomalies in the NASCnormalized flat REE patterns. The characteristics of Mn / TiO2 (< 0.5), U / Th (0.422 1.225), Ce / Ce* (0.92 1.02), (La / Ce)N (0.98 1.23), and (La/Yb)N (0.8 1.78) reflects a biochemical origin rather than hydrothermal origin formed in a setting of continental margin.
The Qinhuangdao area is located in the northeastern margin of the North China Block. The Liangjiashan and Majiagou Formation in this area are mainly composed of finegrained dolomitic limestone, finegrained dolomite, leopardlike limestone and calcirudite, which generally contain nodular, striped and lump cherts. XRD analyses show that the major minerals of the silicalite are quartz, calcite and some dolomite. The silicalite samples are wormlike, spherical and needlelike chalcedony aggregates with metasomatic structure in some of them under the microscope. The silicalites are poor in Mn and Fe, with Si / (Si + Al + Fe) ratios of 0.98 0.99, low ∑REE, and very weak negative Ce anomalies in the NASCnormalized flat REE patterns. The characteristics of Mn / TiO2 (< 0.5), U / Th (0.422 1.225), Ce / Ce* (0.92 1.02), (La / Ce)N (0.98 1.23), and (La/Yb)N (0.8 1.78) reflects a biochemical origin rather than hydrothermal origin formed in a setting of continental margin.
2011, 29(6): 1156-1163.
Abstract:
Comparison and classification of volcanic rocks are the premise and foundation of their lithology research, lithofacies and variation. According to log data, seismic data and pollen analysis, we found that the Kalagang volcanic rocks of Malang depression in Santanghu Basin were thick in the north and east, thin in the south and westareas. The pollen assemblage showed that Gymnosperm pollen had a clear advantage in fern spores and comprised of Genus Cordaitina(Samoilovichi) Hart,Genus Florinites Sehof, WilSonet Bentall, Genus Protohaploxypinus(Samoilovichi) Hart, Genus Striatoabieites(Sedova) Hartpollen. The content of Genus Cordaitina(Samoilovichi) Hart was up to 25.3~54.3%. Compared the log response of Kalagang volcanic rocks and Sedimentary rocks, there performed low natural gamma, low acoustic time, low compensation neutrons, high density and high resistance. The natural gamma value of Kalagang volcanic rocks was lower than Harjiawu Formation, while the resistance was higher. The lithology was mainly maficneutral basalt and andesite, and minor of the tuff, tuffite, volcanic breccia, and so on. Kalagang volcanic rocks of Malang depression can be divided into outbreak phase, overflow phase and volcanic sediment facies. The volcanic activity mainly occurred as a relatively quiet overflow phase, followed by strong eruption phase, and locally developed volcanic sediment facies.
Comparison and classification of volcanic rocks are the premise and foundation of their lithology research, lithofacies and variation. According to log data, seismic data and pollen analysis, we found that the Kalagang volcanic rocks of Malang depression in Santanghu Basin were thick in the north and east, thin in the south and westareas. The pollen assemblage showed that Gymnosperm pollen had a clear advantage in fern spores and comprised of Genus Cordaitina(Samoilovichi) Hart,Genus Florinites Sehof, WilSonet Bentall, Genus Protohaploxypinus(Samoilovichi) Hart, Genus Striatoabieites(Sedova) Hartpollen. The content of Genus Cordaitina(Samoilovichi) Hart was up to 25.3~54.3%. Compared the log response of Kalagang volcanic rocks and Sedimentary rocks, there performed low natural gamma, low acoustic time, low compensation neutrons, high density and high resistance. The natural gamma value of Kalagang volcanic rocks was lower than Harjiawu Formation, while the resistance was higher. The lithology was mainly maficneutral basalt and andesite, and minor of the tuff, tuffite, volcanic breccia, and so on. Kalagang volcanic rocks of Malang depression can be divided into outbreak phase, overflow phase and volcanic sediment facies. The volcanic activity mainly occurred as a relatively quiet overflow phase, followed by strong eruption phase, and locally developed volcanic sediment facies.
2011, 29(6): 1164-1169.
Abstract:
This paper presents a databased study of water level, tide level, tidal currents, sediment type and sediment grain size, winds, runoff, subaqueous bedforms and so on including the application of ECOMSED model to analyze related sediment transporting parameters and forecast hydrodynamic condition and sedimentary processes in the study area. The results showed that sedimentary processes decreased from a rate of 2~5cm/a in northeast to 0.2~0.5cm/a in southwest. In particular, the sedimentation rate got to 5~10cm each year at the northeast of the study area because it is closed to the Pearl River Mouth and easy to get sediment supply from the river mouth. However, the depositional depth was only 0.2~0.5 cm each year at southeast and southwest of the area because tidal currents played a great role in sediment transport in this area. Suspended sediment concentration increased 42.5 mg/L at most in one tidal period. Along coasts, suspended sediment of 10mg/L could be transported to 3.0 km away at EW and 2.2 km away at SN. Around offshore area, suspended sediment of 10 mg/L could be taken to 1.7 km away at EW and 1.6 km away at SN. The largest erosional rate was 10 cm/a and the largest depositional rate was 13 cm/a at the Pearl River Mouth. Furthermore, the exploitation of sea sand has affected the deposition and erosion near the sea area of engineering and had no obvious influence in the Pearl River mouth and coastal area. According to calculation, if a 10m deep pit was excavated at the water area with the depth of 30~60 m, the exploitation area would need 200 years or longer to restore original topography at a sedimentation rate of 0.2~5 cm/a.
This paper presents a databased study of water level, tide level, tidal currents, sediment type and sediment grain size, winds, runoff, subaqueous bedforms and so on including the application of ECOMSED model to analyze related sediment transporting parameters and forecast hydrodynamic condition and sedimentary processes in the study area. The results showed that sedimentary processes decreased from a rate of 2~5cm/a in northeast to 0.2~0.5cm/a in southwest. In particular, the sedimentation rate got to 5~10cm each year at the northeast of the study area because it is closed to the Pearl River Mouth and easy to get sediment supply from the river mouth. However, the depositional depth was only 0.2~0.5 cm each year at southeast and southwest of the area because tidal currents played a great role in sediment transport in this area. Suspended sediment concentration increased 42.5 mg/L at most in one tidal period. Along coasts, suspended sediment of 10mg/L could be transported to 3.0 km away at EW and 2.2 km away at SN. Around offshore area, suspended sediment of 10 mg/L could be taken to 1.7 km away at EW and 1.6 km away at SN. The largest erosional rate was 10 cm/a and the largest depositional rate was 13 cm/a at the Pearl River Mouth. Furthermore, the exploitation of sea sand has affected the deposition and erosion near the sea area of engineering and had no obvious influence in the Pearl River mouth and coastal area. According to calculation, if a 10m deep pit was excavated at the water area with the depth of 30~60 m, the exploitation area would need 200 years or longer to restore original topography at a sedimentation rate of 0.2~5 cm/a.
2011, 29(6): 1170-1179.
Abstract:
The Ili region is located in the northeastern part of Central Asian region, dominated by the westerlies all the year round, loess sediments are widely distributed in the piedmonts of Tianshan Mountains and river terraces, which enables the Ili region to be one of the ideal places for the studies on Asian interior aridification, dust sources of the Northern Hemisphere, past atmospheric circulation, and past global climate change. In this paper, we reconstruct the history of climate change since the last glaciation by analyzing the grain size of Zhaosu section loess. The result shows that the content of grain size＞63 μm can be well compared with the records of Greenland ice core that the climate fluctuations of the global significance such as Heinrich events and the Younger Dryas cold event as well as D-O cycles, reveals the Central Asian's climate changes with the global features of millennial scale and high frequency oscillation since the last glaciation. The analysis of grain size indicates that the loess grain size distribution of the Ili region is similar to that of the Chinese Loess Plateau, dominated mainly by silt, but the contents of sand in the Ili loess is lower and fine clay higher, which is different from those of the Chinese Loess Plateau. However, compared with the Chinese Loess Plateau, the overall integrated condition of water and heat in the Ili region is poorer than that of the Loess Plateau, which basically can be concluded that＜4 μm grain size fraction in the Ili loess may be mainly derived from the Central Desert region, only very small part of the clay results from the role of weathering and pedogenesis or debris. Therefore, given the regional topography and circulation conditions, the dust sources may be mainly from its western desert region of Central Asia, the annually prevalent westerlies and distal dust may play an important role in the formation of the Ili loess. According to the variations of the content of the loess grain size, the Ili region's climate change can be divided into four stages since the last glaciation：(74 ~ 60.2 ka) cold period, (60.2 ~ 30.4 ka) warm period, (30.4 ~ 11 ka) cold period and <11 ka warm and dry period. The abrupt climate events reflected from changes in atmospheric circulation revealed by loess grain size at the Zhaosu section loess can be well compared with the Heinrich events and the Younger Dryas cold event as well as D-O cycles revealed by the oxygen isotope records from GISP2 since the last glaciation, suggesting that the Ili region dominated westerlies is likely to be a simultaneous change with the high latitude climate of the Northern Hemisphere since the last glacial period.
The Ili region is located in the northeastern part of Central Asian region, dominated by the westerlies all the year round, loess sediments are widely distributed in the piedmonts of Tianshan Mountains and river terraces, which enables the Ili region to be one of the ideal places for the studies on Asian interior aridification, dust sources of the Northern Hemisphere, past atmospheric circulation, and past global climate change. In this paper, we reconstruct the history of climate change since the last glaciation by analyzing the grain size of Zhaosu section loess. The result shows that the content of grain size＞63 μm can be well compared with the records of Greenland ice core that the climate fluctuations of the global significance such as Heinrich events and the Younger Dryas cold event as well as D-O cycles, reveals the Central Asian's climate changes with the global features of millennial scale and high frequency oscillation since the last glaciation. The analysis of grain size indicates that the loess grain size distribution of the Ili region is similar to that of the Chinese Loess Plateau, dominated mainly by silt, but the contents of sand in the Ili loess is lower and fine clay higher, which is different from those of the Chinese Loess Plateau. However, compared with the Chinese Loess Plateau, the overall integrated condition of water and heat in the Ili region is poorer than that of the Loess Plateau, which basically can be concluded that＜4 μm grain size fraction in the Ili loess may be mainly derived from the Central Desert region, only very small part of the clay results from the role of weathering and pedogenesis or debris. Therefore, given the regional topography and circulation conditions, the dust sources may be mainly from its western desert region of Central Asia, the annually prevalent westerlies and distal dust may play an important role in the formation of the Ili loess. According to the variations of the content of the loess grain size, the Ili region's climate change can be divided into four stages since the last glaciation：(74 ~ 60.2 ka) cold period, (60.2 ~ 30.4 ka) warm period, (30.4 ~ 11 ka) cold period and <11 ka warm and dry period. The abrupt climate events reflected from changes in atmospheric circulation revealed by loess grain size at the Zhaosu section loess can be well compared with the Heinrich events and the Younger Dryas cold event as well as D-O cycles revealed by the oxygen isotope records from GISP2 since the last glaciation, suggesting that the Ili region dominated westerlies is likely to be a simultaneous change with the high latitude climate of the Northern Hemisphere since the last glacial period.
2011, 29(6): 1180-1189.
Abstract:
The preservation of pyrrolic nitrogen compounds in deepburied carbonate reservoirs are most likely influenced by water and metallic oxides. In this paper, thermal simulation experiments on the pyrroleH2OAl2O3 system were carried out using an autoclave at definite temperature and pressure. The properties of the products were characterized by gaschromatography and Fourier transforminfrared spectrometry methods to investigate the reaction pathway. On the basis of the experimental data, the reaction mechanism and kinetics of the pyrroleH2OAl2O3 system were discussed tentatively. It is found that furan and ammonia were the main products during the reaction, and increasing temperature is favored. Thermochemical exchange effect between organic nitrogen and inorganic oxygen were obviously catalyzed by Al2O3, but inhibited by the increasing volume of water. In the presence of Al2O3, the calculated activation energy of the reaction is 109.35 kJ/mol.
The preservation of pyrrolic nitrogen compounds in deepburied carbonate reservoirs are most likely influenced by water and metallic oxides. In this paper, thermal simulation experiments on the pyrroleH2OAl2O3 system were carried out using an autoclave at definite temperature and pressure. The properties of the products were characterized by gaschromatography and Fourier transforminfrared spectrometry methods to investigate the reaction pathway. On the basis of the experimental data, the reaction mechanism and kinetics of the pyrroleH2OAl2O3 system were discussed tentatively. It is found that furan and ammonia were the main products during the reaction, and increasing temperature is favored. Thermochemical exchange effect between organic nitrogen and inorganic oxygen were obviously catalyzed by Al2O3, but inhibited by the increasing volume of water. In the presence of Al2O3, the calculated activation energy of the reaction is 109.35 kJ/mol.
2011, 29(6): 1190-1198.
Abstract:
The product yields and kinetic characteristics from coal and mudstone through thermal simulation experiments in a closed system are investigated, and the results show that, besides the cracking of heavy hydrocarbon gases, the direct decomposition of organic matter is another methane source during the hightemperature phase. Organic matter of mudstone contains a few components which are prone to generate methane in the primary thermal decomposition stage and has a high thermal stability. However, the organic matter of coal contains more components which are prone to generate methane at the same decomposition stage and has a low thermal stability. It may be caused by the recombined reaction of Nalkanes in C6+ liquid hydrocarbons with kerogen or bitumen under closed environment through cyclisation or aromatizatian effect, which will form new products with high thermal stability and the newly formed products will generate methane at higher maturity stage. At the same time, as extreme value of gas yield increasing, the activation energy and preexponential factor increase gradually, and the gas generation potential with low activation energy reduces. In contrast, the gas generation potential with high activation energy increases gradually. The geological extrapolation result indicates that the gas production rates are basically the same, which are calculated with different extreme gas yields. However, it will draw a wrong conclusion that the higher of extreme gas yield is, the deeper the gas generation threshold is, if the gas generation threshold was divided on the gas transformation ratio. The gas generation history of deep layer in Xujiaweizi fault depression calculated by kinetic model indicates that gas starts to generate in the late of Quantou Formation (105 Ma) and has a long gas generation period.
The product yields and kinetic characteristics from coal and mudstone through thermal simulation experiments in a closed system are investigated, and the results show that, besides the cracking of heavy hydrocarbon gases, the direct decomposition of organic matter is another methane source during the hightemperature phase. Organic matter of mudstone contains a few components which are prone to generate methane in the primary thermal decomposition stage and has a high thermal stability. However, the organic matter of coal contains more components which are prone to generate methane at the same decomposition stage and has a low thermal stability. It may be caused by the recombined reaction of Nalkanes in C6+ liquid hydrocarbons with kerogen or bitumen under closed environment through cyclisation or aromatizatian effect, which will form new products with high thermal stability and the newly formed products will generate methane at higher maturity stage. At the same time, as extreme value of gas yield increasing, the activation energy and preexponential factor increase gradually, and the gas generation potential with low activation energy reduces. In contrast, the gas generation potential with high activation energy increases gradually. The geological extrapolation result indicates that the gas production rates are basically the same, which are calculated with different extreme gas yields. However, it will draw a wrong conclusion that the higher of extreme gas yield is, the deeper the gas generation threshold is, if the gas generation threshold was divided on the gas transformation ratio. The gas generation history of deep layer in Xujiaweizi fault depression calculated by kinetic model indicates that gas starts to generate in the late of Quantou Formation (105 Ma) and has a long gas generation period.
2011, 29(6): 1199-1205.
Abstract:
Δlog R model is widely used in calculating organic carbon content in the past with the stepwise regression model which seldom selected. Stepwise regression model is superior to other models,the paper has proved it from both theory and practice and provided guidance for the further use of the model. So the paper can be divided into three parts. Part of model analysis and comparison: In the paper, Δlog R model, improved Δlog R model and stepwise regression model are analyzed. The article is arranged as follows: firstly, introduce Δlog R model briefly; secondly, bring in improved Δlog R model on the basis of deficiencies of Δlog R model; Finally, present stepwise regression model make up the shortages which improvedΔlog R faced. The paper begins with Δlog R model，pointing out its deficiencies on convenience、 objectivity and applicability from the aspects of baseline value, background value of TOC, composite coefficient K, maturity parameter； Improved Δlog R model is achieved under the principle of Δlog R model, it is more concise and objective by establishing functional relation between organic carbon content and logging data. But improved Δlog R model use only two curves(acoustic transit time and resistivity) to calculate TOC , the calculating results sometimes are not satisfactory . This paper attempts to calculate organic carbon content from a variety of log curves and stepwise regression model is presented. Stepwise regression model is more flexible and objective because it filters logging curves which are closely related to organic carbon content based on actual situation. Part of examples and analyses: In this part, we compare three models with examples and demonstrate the superiority of the stepwise regression model from both theoretic and practice. It is easy to know from the model analysis part that improved Δlog R model is superior to Δlog R model on convenience, objectivity and applicability. From the form of equation we can see that Δlog R model is a special form of stepwise regression model. So, stepwise regression model is better than other two models theoretically; Examples in the paper also show that calculating results of stepwise regression model are more accurate because of its advantage in logging variables selection and combination. Part of suggestions and precautions: we suggest using stepwise regression model to calculate TOC from logging curves. The method which divided large blocks into several small blocks based on sedimentary data is recommended. Log response of TOC is susceptible to interfering factors underground, some interfering factors can made certain logging curves unable to reflect organic carbon content and are excluded from the function. It is difficult to establish a universal formula for the whole block because the interfering factors vary from place to place.It is reasonable to divide large blocks into several small blocks because the factors which impact the logging response of organic carbon are similar in the same small blocks and these factors cancel each other to some extent. At last, we point out some precautions including incompact sediments, poor borehole, low porosity (tight) intervals, depth and lithology and so on.
Δlog R model is widely used in calculating organic carbon content in the past with the stepwise regression model which seldom selected. Stepwise regression model is superior to other models,the paper has proved it from both theory and practice and provided guidance for the further use of the model. So the paper can be divided into three parts. Part of model analysis and comparison: In the paper, Δlog R model, improved Δlog R model and stepwise regression model are analyzed. The article is arranged as follows: firstly, introduce Δlog R model briefly; secondly, bring in improved Δlog R model on the basis of deficiencies of Δlog R model; Finally, present stepwise regression model make up the shortages which improvedΔlog R faced. The paper begins with Δlog R model，pointing out its deficiencies on convenience、 objectivity and applicability from the aspects of baseline value, background value of TOC, composite coefficient K, maturity parameter； Improved Δlog R model is achieved under the principle of Δlog R model, it is more concise and objective by establishing functional relation between organic carbon content and logging data. But improved Δlog R model use only two curves(acoustic transit time and resistivity) to calculate TOC , the calculating results sometimes are not satisfactory . This paper attempts to calculate organic carbon content from a variety of log curves and stepwise regression model is presented. Stepwise regression model is more flexible and objective because it filters logging curves which are closely related to organic carbon content based on actual situation. Part of examples and analyses: In this part, we compare three models with examples and demonstrate the superiority of the stepwise regression model from both theoretic and practice. It is easy to know from the model analysis part that improved Δlog R model is superior to Δlog R model on convenience, objectivity and applicability. From the form of equation we can see that Δlog R model is a special form of stepwise regression model. So, stepwise regression model is better than other two models theoretically; Examples in the paper also show that calculating results of stepwise regression model are more accurate because of its advantage in logging variables selection and combination. Part of suggestions and precautions: we suggest using stepwise regression model to calculate TOC from logging curves. The method which divided large blocks into several small blocks based on sedimentary data is recommended. Log response of TOC is susceptible to interfering factors underground, some interfering factors can made certain logging curves unable to reflect organic carbon content and are excluded from the function. It is difficult to establish a universal formula for the whole block because the interfering factors vary from place to place.It is reasonable to divide large blocks into several small blocks because the factors which impact the logging response of organic carbon are similar in the same small blocks and these factors cancel each other to some extent. At last, we point out some precautions including incompact sediments, poor borehole, low porosity (tight) intervals, depth and lithology and so on.
2011, 29(6): 1206-1212.
Abstract:
By using the principles and research methods of sedimentology, the observation and description of core, integrated with the use of logging data, and so on. This paper investigates the characteristics of various kinds of sand bodies from the aspects of lithology, logging property and sedimentary structures and so on. Through the reservoir study of the Chang 8 oil pools, the sand bodies in Chang 8 oil pools are divided into mouth bars and channels, among which channels can be further Subdivided into 3 types, including subaqueous distributary channels, subaqueous deepincised channels and waterways in fans. The time and space distribution of sand bodies are regular. With the organic coordination of other oil accumulation conditions, such as the favorable reservoir forming conditions which extensively developed reservoir sandstone, adjacent to chang7 source rock formation, shielded by mudstone, and influenced by the sedimentary modes of sand bodies, the oil pools in which multilayer oil reservoir overlays each other and distributes continuously are formed by the above 4 types of sand bodies. The characteristics of the oil pools are as follow: Firstly, the oil pools are in the sedimentary system in which sand bodies overlay each other and distribute continuously in slope zones and center of lakes. Toward the lake center, there are subaqueous distributary channel zone, the mixing zone of subaqueous deepincised channels and waterways in fans, and the mixing zone of waterways and mouth bar. Secondly, the 4 types of sand bodies overlay each other randomly in space. The overlaying patterns are both of tabular and staggered. However, they have different stratigraphic attributes. Thirdly, multilayer sand bodies contribute to continuous reservoir, but they have respective oilwater systems. Oil reservoir, gas reservoir, water layer and dry layer are concomitant with each other. On the basis of above, this paper finds the reservoir forming mode of "multilayer oil reservoir overlays each other” of Chang 8 Formation.
By using the principles and research methods of sedimentology, the observation and description of core, integrated with the use of logging data, and so on. This paper investigates the characteristics of various kinds of sand bodies from the aspects of lithology, logging property and sedimentary structures and so on. Through the reservoir study of the Chang 8 oil pools, the sand bodies in Chang 8 oil pools are divided into mouth bars and channels, among which channels can be further Subdivided into 3 types, including subaqueous distributary channels, subaqueous deepincised channels and waterways in fans. The time and space distribution of sand bodies are regular. With the organic coordination of other oil accumulation conditions, such as the favorable reservoir forming conditions which extensively developed reservoir sandstone, adjacent to chang7 source rock formation, shielded by mudstone, and influenced by the sedimentary modes of sand bodies, the oil pools in which multilayer oil reservoir overlays each other and distributes continuously are formed by the above 4 types of sand bodies. The characteristics of the oil pools are as follow: Firstly, the oil pools are in the sedimentary system in which sand bodies overlay each other and distribute continuously in slope zones and center of lakes. Toward the lake center, there are subaqueous distributary channel zone, the mixing zone of subaqueous deepincised channels and waterways in fans, and the mixing zone of waterways and mouth bar. Secondly, the 4 types of sand bodies overlay each other randomly in space. The overlaying patterns are both of tabular and staggered. However, they have different stratigraphic attributes. Thirdly, multilayer sand bodies contribute to continuous reservoir, but they have respective oilwater systems. Oil reservoir, gas reservoir, water layer and dry layer are concomitant with each other. On the basis of above, this paper finds the reservoir forming mode of "multilayer oil reservoir overlays each other” of Chang 8 Formation.
