2013 Vol. 31, No. 04
Display Method:
2013, 31(04): 563-570.
Abstract:
The karst reservoir rock of Ordovician weathering crust is developed on the top of Majiagou Formation, Ordovician system, in Yan′an area, southeastern Ordos Basin. Because of the palaeogeomorphology stand for background of sedimentation and diagenesis in formations, so it is important in formation and evolutionary process of reservoir rocks. On the basis of regional tectonic setting and formation distribution, utilizing comprehensively "methods of residual thickness" and "methods of moulage", combining with thickness distribution of bauxite and identifing results of ancient erosion grooves, the spatial pattern of palaeogeomorphic features from Ordovician weathering crust in Yan'an area is restored correctly. It is showed from the results that it displays for karst highland in southwest, mostly of karst slope in middle parts, and intermediate zone between karst slope and karst basin in east of Yan'an area.The formation and development of reservoir rocks and accumulation of gas are influenced by the spatial pattern of palaeogeomorphic features and distribution of ancient erosion grooves. There are better gas display in karst paleo-highland, as well as in slope adjacent to eroded ancient erosion grooves, responsible for development degree of reservoir rock, physical property and sealing nature of caprock upon unconformity surface, caused probably by learching of meteoric water.
The karst reservoir rock of Ordovician weathering crust is developed on the top of Majiagou Formation, Ordovician system, in Yan′an area, southeastern Ordos Basin. Because of the palaeogeomorphology stand for background of sedimentation and diagenesis in formations, so it is important in formation and evolutionary process of reservoir rocks. On the basis of regional tectonic setting and formation distribution, utilizing comprehensively "methods of residual thickness" and "methods of moulage", combining with thickness distribution of bauxite and identifing results of ancient erosion grooves, the spatial pattern of palaeogeomorphic features from Ordovician weathering crust in Yan'an area is restored correctly. It is showed from the results that it displays for karst highland in southwest, mostly of karst slope in middle parts, and intermediate zone between karst slope and karst basin in east of Yan'an area.The formation and development of reservoir rocks and accumulation of gas are influenced by the spatial pattern of palaeogeomorphic features and distribution of ancient erosion grooves. There are better gas display in karst paleo-highland, as well as in slope adjacent to eroded ancient erosion grooves, responsible for development degree of reservoir rock, physical property and sealing nature of caprock upon unconformity surface, caused probably by learching of meteoric water.
2013, 31(04): 580-589.
Abstract:
The lithofacies features and carbon and oxygen stable isotopes composition of Lower Paleozoic limestones in Ordos Basin change in a wide range. Based on the identification of rock thin section and cathode luminescent image, the measurement of carbon, oxygen stable isotopes of rocks and micro area of minerals, the analysis of liquid inclusion and its homogenous temperature testing, it is found that δ18O and δ13C values of micrite, grain limestone formed in normal sea water are the highest, δ18O values of grain limestone, breccia micrite, porphyritic dolomite-containing limestone or dolomitic limestone leached by meteoric water as well as freashwater calcite cements changes in a narrow range, and δ13C values of them obviously decreased with increasing of freashwater leaching degree. δ18O and δ13C values of megacryst limestone formed in de-gypsum reaction are low, which commonly exhibit zonal structure in cathodoluminescence thin section. δ18O and δ13C values of Middle-fine crystalline limestones are higher than that of megacryst limestone, which were formed in the dedolomitization reaction going with sulphate dissolution and commonly exhibit pupa structure. δ18O and δ13C values of late hydrothermal calcite cements are the lowest, in which liquid inclusion homogenous temperature varies from 100 to 150℃. Late calcite cements contain more Mn2+ and show brighter aurantium cathodoluminescence than freashwater calcite cements. The results indicate that the petrographic characteristics of limestone, carbon and oxygen stable isotope composition, and liquid inclusion homogenous temperature are important indexes to identify diagenetic environment and facies of limestone.
The lithofacies features and carbon and oxygen stable isotopes composition of Lower Paleozoic limestones in Ordos Basin change in a wide range. Based on the identification of rock thin section and cathode luminescent image, the measurement of carbon, oxygen stable isotopes of rocks and micro area of minerals, the analysis of liquid inclusion and its homogenous temperature testing, it is found that δ18O and δ13C values of micrite, grain limestone formed in normal sea water are the highest, δ18O values of grain limestone, breccia micrite, porphyritic dolomite-containing limestone or dolomitic limestone leached by meteoric water as well as freashwater calcite cements changes in a narrow range, and δ13C values of them obviously decreased with increasing of freashwater leaching degree. δ18O and δ13C values of megacryst limestone formed in de-gypsum reaction are low, which commonly exhibit zonal structure in cathodoluminescence thin section. δ18O and δ13C values of Middle-fine crystalline limestones are higher than that of megacryst limestone, which were formed in the dedolomitization reaction going with sulphate dissolution and commonly exhibit pupa structure. δ18O and δ13C values of late hydrothermal calcite cements are the lowest, in which liquid inclusion homogenous temperature varies from 100 to 150℃. Late calcite cements contain more Mn2+ and show brighter aurantium cathodoluminescence than freashwater calcite cements. The results indicate that the petrographic characteristics of limestone, carbon and oxygen stable isotope composition, and liquid inclusion homogenous temperature are important indexes to identify diagenetic environment and facies of limestone.
2013, 31(04): 600-607.
Abstract:
Fluvial sandbody is one of the most important hydrocarbon reservoirs in China. Using of high-resolution sequence stratigraphy in fluvial facies in development of oilfield is very important to the Guidance of fluvail sandbod Subdivision and Correlation. There are complex factors, including fluvial facies autocyclicity sediment, the effect of sedimentary surface, channel pattern and sandbody architecture, and the orders of base-level cycles, which resulted in the difficulty to define subdivision and correlation. According to the theory and approach of high-resolution sequence stratigraphy, combining with fluvial facies model, lithofacies and facies sequence and association, and key surface correlation, reservoir fluid correlation and channel erosion and fill, fluvial reservoir subdivision and comparison have been carried out. Provided a clue and methods on the fluvial facies subdivision and correlation in development of oilfield of intermediary and later stage, in order to be helpful to product and develop of oilfield. In Minghuazhen Formation Bohai Q Oilfield, It has achieved good results in the practical application.
Fluvial sandbody is one of the most important hydrocarbon reservoirs in China. Using of high-resolution sequence stratigraphy in fluvial facies in development of oilfield is very important to the Guidance of fluvail sandbod Subdivision and Correlation. There are complex factors, including fluvial facies autocyclicity sediment, the effect of sedimentary surface, channel pattern and sandbody architecture, and the orders of base-level cycles, which resulted in the difficulty to define subdivision and correlation. According to the theory and approach of high-resolution sequence stratigraphy, combining with fluvial facies model, lithofacies and facies sequence and association, and key surface correlation, reservoir fluid correlation and channel erosion and fill, fluvial reservoir subdivision and comparison have been carried out. Provided a clue and methods on the fluvial facies subdivision and correlation in development of oilfield of intermediary and later stage, in order to be helpful to product and develop of oilfield. In Minghuazhen Formation Bohai Q Oilfield, It has achieved good results in the practical application.
2013, 31(04): 616-620.
Abstract:
The mineral components and frangibilities of the shales of Es4sand Es3xof Shahejie Formation in Dongying depression were researched, and were compared with those of North America shales. The results show that those main mineral components include detrital minerals (feldspar and quartz) from land, clay minerals and non-clay minerals (carbonate rocks and pyrite) self-engendered. The average content of clay minerals is only 25%, much lower than marine shale and conventional viewpoint (over 50%). The average content of feldspar is average about 5%, higher than general marine shale. Self-engendered carbonate rocks content is rich, with average value about 37%, and changing dramatically. Short distance from origin deposition and frequently changing sedimentary facies is genesis of above shale mineral component characters. In addition, the enumerated quartz frangibility, Carbonate frangibility and total frangibility was formulated for continental basin shale, and the enumerated quartz frangibilities, carbonate frangibilities and total frangibilities of shales of the Dongying depression were calculated, it was founded that the content of carbonate is mainly affection factor for frangibility of the shales. The results indicate that the shale of the Dongying depression are easily to form natural fractures or easily to be crushed, and are potential reservoirs for shale gas.
The mineral components and frangibilities of the shales of Es4sand Es3xof Shahejie Formation in Dongying depression were researched, and were compared with those of North America shales. The results show that those main mineral components include detrital minerals (feldspar and quartz) from land, clay minerals and non-clay minerals (carbonate rocks and pyrite) self-engendered. The average content of clay minerals is only 25%, much lower than marine shale and conventional viewpoint (over 50%). The average content of feldspar is average about 5%, higher than general marine shale. Self-engendered carbonate rocks content is rich, with average value about 37%, and changing dramatically. Short distance from origin deposition and frequently changing sedimentary facies is genesis of above shale mineral component characters. In addition, the enumerated quartz frangibility, Carbonate frangibility and total frangibility was formulated for continental basin shale, and the enumerated quartz frangibilities, carbonate frangibilities and total frangibilities of shales of the Dongying depression were calculated, it was founded that the content of carbonate is mainly affection factor for frangibility of the shales. The results indicate that the shale of the Dongying depression are easily to form natural fractures or easily to be crushed, and are potential reservoirs for shale gas.
2013, 31(04): 630-638.
Abstract:
The study of aluminum clay rock of Dafoyan mining area proves that the scandium does not exist in the form of independent minerals and ion adsorption. There is nearly no organic matter in bauxite ore-bearing horizon and we can also ruled out the possibility of the scandium integrate with organic matter. We find the scandium is rich in detrital zircon, base on the results of the SEM and the analysis of spectrum. The scandium widespread distribute on the surface of detrital zircons, and there are different percentage composition of scandium in different parts of the detrital zircon, the maximum is 2.75%, and the minimum is not detected scandium, moreover the percentage composition of scandium in the pits or cracks are higher frequently. So, we consider that there are likely three forms of scandium in detrital zircons: isomorphism, ion-adsorption and the microscopic structure of the mixed in with content. These researches will provide a theoretical basis for the development and utilization of the bauxite in southern Chongqing in future.
The study of aluminum clay rock of Dafoyan mining area proves that the scandium does not exist in the form of independent minerals and ion adsorption. There is nearly no organic matter in bauxite ore-bearing horizon and we can also ruled out the possibility of the scandium integrate with organic matter. We find the scandium is rich in detrital zircon, base on the results of the SEM and the analysis of spectrum. The scandium widespread distribute on the surface of detrital zircons, and there are different percentage composition of scandium in different parts of the detrital zircon, the maximum is 2.75%, and the minimum is not detected scandium, moreover the percentage composition of scandium in the pits or cracks are higher frequently. So, we consider that there are likely three forms of scandium in detrital zircons: isomorphism, ion-adsorption and the microscopic structure of the mixed in with content. These researches will provide a theoretical basis for the development and utilization of the bauxite in southern Chongqing in future.
2013, 31(04): 639-645.
Abstract:
Situated at the junction of land and sea, tidal flat is very sensitive to typhoon event and anthropogenic influence. In order to reveal the histories of regional typhoon events and strong anthropogenic influences, two sediment cores were collected in inner Spartina alterniflora marsh and middle-upper intertidal flat in the Luoyuan Bay for sedimentary records extraction. The sediment cores were cut with 1 cm interval for grain size and radio isotope dating. The results of grain size analysis indicate that the sediment on tidal flat of Luoyuan Bay is mainly composed by fine fractions. The mean grain sizes of core sediments in inner Spartina alterniflora marsh and middle-upper intertidal flat are 5.41 μm~45.00 μm and 5.4 μm~68.82 μm, respectively; however, there are several interfaces where sediment characteristics vary obviously. The mean sedimentation rates in inner Spartina alterniflora marsh and middle-upper intertidal flat calculated from 210Pb are 1.96 cm/a and 1.23 cm/a, respectively. However, the mean sedimentation rates increased from 0.56 cm/a during 1909~1946 to 2.36 cm/a during 1946~1966 at upper intertidal flat due to strong reclamations, and the introduction of Spartina alterniflora led to the mean sedimentation rate increased to 5.10 cm/a during the early marsh formation, and with increasing of the marsh age, the mean sedimentation rate decreased to 2.83 cm/a. The sedimentary records of core sediments collected from inner Spartina alterniflora marsh and middle-upper intertidal flat not only recorded the typhoon events which brought the strong effects on the Luoyuan Bay in recent 170 years, and but also recorded the several large scale reclamation from 1950's.
Situated at the junction of land and sea, tidal flat is very sensitive to typhoon event and anthropogenic influence. In order to reveal the histories of regional typhoon events and strong anthropogenic influences, two sediment cores were collected in inner Spartina alterniflora marsh and middle-upper intertidal flat in the Luoyuan Bay for sedimentary records extraction. The sediment cores were cut with 1 cm interval for grain size and radio isotope dating. The results of grain size analysis indicate that the sediment on tidal flat of Luoyuan Bay is mainly composed by fine fractions. The mean grain sizes of core sediments in inner Spartina alterniflora marsh and middle-upper intertidal flat are 5.41 μm~45.00 μm and 5.4 μm~68.82 μm, respectively; however, there are several interfaces where sediment characteristics vary obviously. The mean sedimentation rates in inner Spartina alterniflora marsh and middle-upper intertidal flat calculated from 210Pb are 1.96 cm/a and 1.23 cm/a, respectively. However, the mean sedimentation rates increased from 0.56 cm/a during 1909~1946 to 2.36 cm/a during 1946~1966 at upper intertidal flat due to strong reclamations, and the introduction of Spartina alterniflora led to the mean sedimentation rate increased to 5.10 cm/a during the early marsh formation, and with increasing of the marsh age, the mean sedimentation rate decreased to 2.83 cm/a. The sedimentary records of core sediments collected from inner Spartina alterniflora marsh and middle-upper intertidal flat not only recorded the typhoon events which brought the strong effects on the Luoyuan Bay in recent 170 years, and but also recorded the several large scale reclamation from 1950's.
2013, 31(04): 653-662.
Abstract:
Reservoir in Daqing Oilfield, the largest oil field in china, is mainly formed in the huge fluvial-delta system, with hign heterogeneities. Distributary channel and channel sandstone are key sandbodies for hydrocarbon accumulation. After more than 40 years of high speed development, it is now in matural stage with a very high water cut. A good understanding of remaining oil and bypassed oil, which are governed by the baffles and barriers, will be a key work for improving the recovery, while reservoir architectures will give a clue for the barriers and baffles prediction and the oil compartment identification. Architecture analysis method, widely used for the outcrop analysis, is a good method to understanding the architecture of fluvial deposit. Although some attempts have been tried for the subsurface reservoir analysis and resulting some progress of this method, there are still many difficulties in the subsurface architecture description. Especially it is hard to give a good explanation for the deposition process of the reservoir for this method focusing on the reorganization and distribution of the elements and not enough attention were paid for the process, which made it a little difficult for geologist to understand the architecture result. Here a new method for meandering channel sandstone architecture analysis was provided in the density well spacing area. It is hard to reconstruct the process of the highly cut super-complex sandstone, but it is possible to reconstruct the depositing process of moderately cut sandstone and a good explanation can be made for the relationship of the sandbodies in the channel framework. If the process is correct then the architecture will be more reliable. There is four hierarchies of architecture were reconstructed in this method, including composite channel belts, single channel belt, point bar and lateral accretion. The composite channel belt was reconstructed based on the widely spread flooding plain deposit between channel belts in the vertical profile. The flooding deposit maybe eroded by the later channel. The main work is to separate the deposit in vertical dimension and to reconstruct a detailed framefork. Single channel belt will bounded based on the flooding plain deposit between channel belts on the areal dimension. Sometimes the distributary channel had to be separated by the sand distribution. Point bar can be recognized on well logging, but it is difficult to make a correlation to get the 3 dimension of it. So it will be reconstructed based on the swing process of the channel. First the final abandoned position for the channel was inferred and abandoned cannels during the swing process were recognized based on the sand thickness and the well logging shape of each well and their areal combination. Then the channel swing direction and part of the channel shape can be guessed. Finally the original place for the channel would be induced based on the swing direction and the sand thickness before the first abandoned channel. After all of these works, the channel belt could be separated to several stage and in each stage there were several point bars. Lateral accretion architecture is reconstructed based on distribution of the areal density of accretion shale which can be quantified through its relation to its density and the dip in vertical profile. It is easy to get vertical accretion shale in core or well logging. The dip can be calculated based on the core or very densely spaced well which were drilled on the same well site. Two typical layer formed in the delta plain in North S3 block were select to reconstruct the process of the deposit and the detailed reservoir architecture. There are 38 and 23 point bars were recognized in the two layers each. And the dip of the accretion shale is between 4~10 degree and the areal space among shales is 16~20 meters. Combining these data and the shale distribution in the well, the architecture of the lateral accretion were constructed which gives a good understanding of the detailed architecture of the reservoir channel sandstone in the delta plain.
Reservoir in Daqing Oilfield, the largest oil field in china, is mainly formed in the huge fluvial-delta system, with hign heterogeneities. Distributary channel and channel sandstone are key sandbodies for hydrocarbon accumulation. After more than 40 years of high speed development, it is now in matural stage with a very high water cut. A good understanding of remaining oil and bypassed oil, which are governed by the baffles and barriers, will be a key work for improving the recovery, while reservoir architectures will give a clue for the barriers and baffles prediction and the oil compartment identification. Architecture analysis method, widely used for the outcrop analysis, is a good method to understanding the architecture of fluvial deposit. Although some attempts have been tried for the subsurface reservoir analysis and resulting some progress of this method, there are still many difficulties in the subsurface architecture description. Especially it is hard to give a good explanation for the deposition process of the reservoir for this method focusing on the reorganization and distribution of the elements and not enough attention were paid for the process, which made it a little difficult for geologist to understand the architecture result. Here a new method for meandering channel sandstone architecture analysis was provided in the density well spacing area. It is hard to reconstruct the process of the highly cut super-complex sandstone, but it is possible to reconstruct the depositing process of moderately cut sandstone and a good explanation can be made for the relationship of the sandbodies in the channel framework. If the process is correct then the architecture will be more reliable. There is four hierarchies of architecture were reconstructed in this method, including composite channel belts, single channel belt, point bar and lateral accretion. The composite channel belt was reconstructed based on the widely spread flooding plain deposit between channel belts in the vertical profile. The flooding deposit maybe eroded by the later channel. The main work is to separate the deposit in vertical dimension and to reconstruct a detailed framefork. Single channel belt will bounded based on the flooding plain deposit between channel belts on the areal dimension. Sometimes the distributary channel had to be separated by the sand distribution. Point bar can be recognized on well logging, but it is difficult to make a correlation to get the 3 dimension of it. So it will be reconstructed based on the swing process of the channel. First the final abandoned position for the channel was inferred and abandoned cannels during the swing process were recognized based on the sand thickness and the well logging shape of each well and their areal combination. Then the channel swing direction and part of the channel shape can be guessed. Finally the original place for the channel would be induced based on the swing direction and the sand thickness before the first abandoned channel. After all of these works, the channel belt could be separated to several stage and in each stage there were several point bars. Lateral accretion architecture is reconstructed based on distribution of the areal density of accretion shale which can be quantified through its relation to its density and the dip in vertical profile. It is easy to get vertical accretion shale in core or well logging. The dip can be calculated based on the core or very densely spaced well which were drilled on the same well site. Two typical layer formed in the delta plain in North S3 block were select to reconstruct the process of the deposit and the detailed reservoir architecture. There are 38 and 23 point bars were recognized in the two layers each. And the dip of the accretion shale is between 4~10 degree and the areal space among shales is 16~20 meters. Combining these data and the shale distribution in the well, the architecture of the lateral accretion were constructed which gives a good understanding of the detailed architecture of the reservoir channel sandstone in the delta plain.
2013, 31(04): 672-682.
Abstract:
There are geological conditions for the formation of tight oil in the Qaidam basin. The Middle and Lower Jurrasic semi-deep lacustrine facies mudstone and the Tertiary semi-deep lake facies to deep lake facies mudstone are widely distributed in the Qaidam basin, which constitutes a favorable relationship of source and reservoir coexistence for the formation of tight oil with bank to shallow lake facies sand body or carbonate rock which is interbeded with or situated near the source rocks. The Jurassic source rocks in the northern margin of the Qaidam basin have an average organic carbon value of 1.85, Ⅰ-Ⅱ2organic types and a maturity range from mature stage to over mature stage with better oil generation potential. The Tertiary source rocks in the west of the Qaidam basin have a range of organic carbon from 0.4%to 1.2%Ⅰ-Ⅱ1 organic types and a Ro value from 0.4% to 1.2% within an oil generation window. Compared to other Chinese basins, the degree of hydrocarbon inversion of the Tertiary source rocks is high. The clastic reservoir space is dominated by remained intergranular pores and corroded pores with porosity from 3.8% to 10.2% and permeability from 0.1×103 μm2 to 2×103 μm2. The reservoir rocks have characteristics of thinner single beds, vertical multilayer’s superimposition, thicker accumulated thickness and many horizontal oil beds overlayed. The reservoir space of the carbonate rock is predominated by corroded pores and interbeded contracted cracks with porosity from 5% to 7% and permeability from 0.2×103 μm2 to 0.7 ×103 μm2. The reservoir rock is characterized by more single beds, thinner single beds, more sedimentary facies controlled and horizontal widely continuous oil beds. The groups of oil reservoir formation include four types, that is, inner source included group, upper source widely distributed model, lower source layered group, and beside source covered group, which are mainly controlled by source depressions. The tight oil in the Qaidam basin is enriched and has a great potential, being estimated the resource yield ranges from 8.16 to 10.46×108 Tons. After the analysis of reservoir forming conditions, we think that four favorable exploration areas, i.e., Zhahaquan-Wunan, Xiaoliangshan-Nanyishan and Qigequan-Yaojin in the western Qaidam basin and Lenghu in the northern Qaidam basin, can be served as current exploration targets.
There are geological conditions for the formation of tight oil in the Qaidam basin. The Middle and Lower Jurrasic semi-deep lacustrine facies mudstone and the Tertiary semi-deep lake facies to deep lake facies mudstone are widely distributed in the Qaidam basin, which constitutes a favorable relationship of source and reservoir coexistence for the formation of tight oil with bank to shallow lake facies sand body or carbonate rock which is interbeded with or situated near the source rocks. The Jurassic source rocks in the northern margin of the Qaidam basin have an average organic carbon value of 1.85, Ⅰ-Ⅱ2organic types and a maturity range from mature stage to over mature stage with better oil generation potential. The Tertiary source rocks in the west of the Qaidam basin have a range of organic carbon from 0.4%to 1.2%Ⅰ-Ⅱ1 organic types and a Ro value from 0.4% to 1.2% within an oil generation window. Compared to other Chinese basins, the degree of hydrocarbon inversion of the Tertiary source rocks is high. The clastic reservoir space is dominated by remained intergranular pores and corroded pores with porosity from 3.8% to 10.2% and permeability from 0.1×103 μm2 to 2×103 μm2. The reservoir rocks have characteristics of thinner single beds, vertical multilayer’s superimposition, thicker accumulated thickness and many horizontal oil beds overlayed. The reservoir space of the carbonate rock is predominated by corroded pores and interbeded contracted cracks with porosity from 5% to 7% and permeability from 0.2×103 μm2 to 0.7 ×103 μm2. The reservoir rock is characterized by more single beds, thinner single beds, more sedimentary facies controlled and horizontal widely continuous oil beds. The groups of oil reservoir formation include four types, that is, inner source included group, upper source widely distributed model, lower source layered group, and beside source covered group, which are mainly controlled by source depressions. The tight oil in the Qaidam basin is enriched and has a great potential, being estimated the resource yield ranges from 8.16 to 10.46×108 Tons. After the analysis of reservoir forming conditions, we think that four favorable exploration areas, i.e., Zhahaquan-Wunan, Xiaoliangshan-Nanyishan and Qigequan-Yaojin in the western Qaidam basin and Lenghu in the northern Qaidam basin, can be served as current exploration targets.
2013, 31(04): 693-698.
Abstract:
In the southeast of the Ordos Basin, the Upper Paleozoic gas reservoir maily includes Taiyuan Formation, Shanxi Formation, the lower Shihezi Formation and the upper Shihezi Formation and lithology is mainly quartz sandstone. Based on microscope petrographic study, the main diagenetic types of the reservoir are compaction, pressure dissolution, cementation and metasomatism, fracture and dissolution, and four major diagenetic stages can be identified in study reservoir. The first stage is precocious rock early stage and shallow burial diagenesis, whose performances are that the clastic particles present a point -line contact relation and a large number of siliceous cement forms. The second stage is fracture and dissolution, which is the strongest diagenesis in this area and quartz and feldspar are generally affected then a great many crack forms, meanwhile a lot of pores appear. The third stage is the late deep burial diagenesis, whose performances are that the quartz clastic particle dissolves and early crack forms then the recrystallization happens, making the dissolution pore and fracture heal, and multiple growing increased edges form as well as a lot of siliceous cement. The fourth stage is the formation of late tectonic stress fracture, late carbonate and gypsum mineral salts. Two phases of gas inclusions are identified. The first phase of gas inclusions was formed in the late stage of early diagenesis. This period of inclusion hasa higher gas/liquid, which is generally about 20 percent, and fluoresce inclusions are seen. The formation temperatures of inclusions are between 130℃ and 140℃ and the salinity is between 1.0 wt%and 2.0 wt%. The second phase of the natural gas inclusions forming in late diagenetic later period are distributed in late fractures and the late sparry calcite and quartz cement. The organic inclusions in later sparry calcite and quartz cement are more, and the planar distribution, distributed in calcite or plagioclase cleavage plane, which are maily gaseous hydrocarbon inclusions. This inclusion’s gas/liquid ratio is small, generally less than 10% while most of them are the organic gaseous and brine forming the gas and liquid these two phase inclusion with the parcel body wall is thin and the color is shallow. Inclusion’s formation temperature is between 160℃ and 170℃ and its salinities are between 3.0 wt% and 4.0wt %. Studies suggest that the first stage represents the early gas’s primary migration and reservoir injection events, while the second stage represents the natural gas’s massive secondary migration and gas accumulation event.
In the southeast of the Ordos Basin, the Upper Paleozoic gas reservoir maily includes Taiyuan Formation, Shanxi Formation, the lower Shihezi Formation and the upper Shihezi Formation and lithology is mainly quartz sandstone. Based on microscope petrographic study, the main diagenetic types of the reservoir are compaction, pressure dissolution, cementation and metasomatism, fracture and dissolution, and four major diagenetic stages can be identified in study reservoir. The first stage is precocious rock early stage and shallow burial diagenesis, whose performances are that the clastic particles present a point -line contact relation and a large number of siliceous cement forms. The second stage is fracture and dissolution, which is the strongest diagenesis in this area and quartz and feldspar are generally affected then a great many crack forms, meanwhile a lot of pores appear. The third stage is the late deep burial diagenesis, whose performances are that the quartz clastic particle dissolves and early crack forms then the recrystallization happens, making the dissolution pore and fracture heal, and multiple growing increased edges form as well as a lot of siliceous cement. The fourth stage is the formation of late tectonic stress fracture, late carbonate and gypsum mineral salts. Two phases of gas inclusions are identified. The first phase of gas inclusions was formed in the late stage of early diagenesis. This period of inclusion hasa higher gas/liquid, which is generally about 20 percent, and fluoresce inclusions are seen. The formation temperatures of inclusions are between 130℃ and 140℃ and the salinity is between 1.0 wt%and 2.0 wt%. The second phase of the natural gas inclusions forming in late diagenetic later period are distributed in late fractures and the late sparry calcite and quartz cement. The organic inclusions in later sparry calcite and quartz cement are more, and the planar distribution, distributed in calcite or plagioclase cleavage plane, which are maily gaseous hydrocarbon inclusions. This inclusion’s gas/liquid ratio is small, generally less than 10% while most of them are the organic gaseous and brine forming the gas and liquid these two phase inclusion with the parcel body wall is thin and the color is shallow. Inclusion’s formation temperature is between 160℃ and 170℃ and its salinities are between 3.0 wt% and 4.0wt %. Studies suggest that the first stage represents the early gas’s primary migration and reservoir injection events, while the second stage represents the natural gas’s massive secondary migration and gas accumulation event.
2013, 31(04): 706-717.
Abstract:
Based on the existing high-resolution 2D seismic data, we identified a large deep-water fan system in the Northwest sub-basin, the abyssal plain of northern South China Sea. The results show a canyon-channel transition zone with channel avulsions in the upper fan, channel-levee systems in the middle fan and channel-lobe systems in the lower fan. The Qiongdongnan Center canyon-channel is considered as the main sediment supply system, with sediments mainly from the Red River and Indochina, northern shelf and slope, and Zhongsha and Xisha uplift regions. A combination of the pre-existing topography and sediment supply strength appears to have a control on the temperospatial distribution of the deep-water fan system. Geographically the fan system is divided into north and south parts by the Shuangfeng seamount, and geologically I to V sub-fans can be identified, respectively corresponding to the late Miocene (I), Pliocene (II and III), and Quaternary (IV and V).The early-deposited sub-fans altered the topography, while strong sediment supplies improved the overflow frequency, with obvious lateral migration in individual fans. The "three step" continental slope of northern South China Sea affected the development and evolution of deepwater fan systems.
Based on the existing high-resolution 2D seismic data, we identified a large deep-water fan system in the Northwest sub-basin, the abyssal plain of northern South China Sea. The results show a canyon-channel transition zone with channel avulsions in the upper fan, channel-levee systems in the middle fan and channel-lobe systems in the lower fan. The Qiongdongnan Center canyon-channel is considered as the main sediment supply system, with sediments mainly from the Red River and Indochina, northern shelf and slope, and Zhongsha and Xisha uplift regions. A combination of the pre-existing topography and sediment supply strength appears to have a control on the temperospatial distribution of the deep-water fan system. Geographically the fan system is divided into north and south parts by the Shuangfeng seamount, and geologically I to V sub-fans can be identified, respectively corresponding to the late Miocene (I), Pliocene (II and III), and Quaternary (IV and V).The early-deposited sub-fans altered the topography, while strong sediment supplies improved the overflow frequency, with obvious lateral migration in individual fans. The "three step" continental slope of northern South China Sea affected the development and evolution of deepwater fan systems.
2013, 31(04): 724-729.
Abstract:
The lower part of Xiaganchaigou Formation is an important prospecting object in the central areas of northern Qaidam basin. To find out the factors controlling the reservoir property is the basis of prospecting. Based on the normal thin sections, cast thin sections and drilling data, the rocks characteristics between Lenghuqihao and Nanbaxian were correlated. The mixed deposits were found very common in the central part of northern Qaidam basin，but the cementaion type and the cement composition vary obviously in different sedimentary facies. Because of the high salinity of Lenghuqihao area which located in littoral facies，the cements contains a lot of anhydrite and the sandstones are mainly basal cemented. The salinity of Nanbaxian located in delta front facies is lower because of the great mounts of water input by the rivers, so there is little anhydrite in the sandstones which are porous cemented to basal cemented. The initial porosity in Nanbaxian is much higher than Lenghuqihao, and the sandstones were much more easily dissolved. The abundance of petroleum in two aeras is very different as the great difference in initial porosity and porosity evolution model.
The lower part of Xiaganchaigou Formation is an important prospecting object in the central areas of northern Qaidam basin. To find out the factors controlling the reservoir property is the basis of prospecting. Based on the normal thin sections, cast thin sections and drilling data, the rocks characteristics between Lenghuqihao and Nanbaxian were correlated. The mixed deposits were found very common in the central part of northern Qaidam basin，but the cementaion type and the cement composition vary obviously in different sedimentary facies. Because of the high salinity of Lenghuqihao area which located in littoral facies，the cements contains a lot of anhydrite and the sandstones are mainly basal cemented. The salinity of Nanbaxian located in delta front facies is lower because of the great mounts of water input by the rivers, so there is little anhydrite in the sandstones which are porous cemented to basal cemented. The initial porosity in Nanbaxian is much higher than Lenghuqihao, and the sandstones were much more easily dissolved. The abundance of petroleum in two aeras is very different as the great difference in initial porosity and porosity evolution model.
2013, 31(04): 738-746.
Abstract:
In central and southern Junggar basin, Jurassic source rock is characterized by the large thickness, widespread, whose partial interval have well potential hydrocarbon and exploration. Based on the former study, according to the organic geochemistry and organic petrology experiment analysis method, the distribution characteristics, hydrocarbon potential, biomarker geochemistry and sedimentary environment have been investigated. The results indicate that in western Well Pen 1 depression, the Jurassic formation source rock has worse hydrocarbon potential, in Shawan depression, the Badaowan Formation and Xishanyao Formation have better hydrocarbon potential, but Sangonghe Formation source rock is worse. In Sikeshu depression, Badaowan Formation source rock has better hydrocarbon potential. Additionally, in earlier sedimentary period of Badaowan Formation, the research area developed delta front sub-facies and shore shallow lake facies. In Shawan depression, the formation developed shore shallow facies and limnetic facies with much organic matter input. The source rock is formed in weak oxidation-strong weak sedimentary environment with high plant input. In Sangonghe Formation sedimentary period, the study area distributed shore shallow lake faices, whose source rock is formed in strong oxidation environment with lacustrine high plant input. In Xishanyao Formation sedimentary period, in Mahu depression, Luliang uplift, and Western Well Pen 1 depression distributed delta plain facies and front plain facies. The sedimentary centre moved to eastern and southern depression with sub-deep lake facies, whose source rock is formed in weak oxidation-strong oxidation environment with high lacustrine plant input.
In central and southern Junggar basin, Jurassic source rock is characterized by the large thickness, widespread, whose partial interval have well potential hydrocarbon and exploration. Based on the former study, according to the organic geochemistry and organic petrology experiment analysis method, the distribution characteristics, hydrocarbon potential, biomarker geochemistry and sedimentary environment have been investigated. The results indicate that in western Well Pen 1 depression, the Jurassic formation source rock has worse hydrocarbon potential, in Shawan depression, the Badaowan Formation and Xishanyao Formation have better hydrocarbon potential, but Sangonghe Formation source rock is worse. In Sikeshu depression, Badaowan Formation source rock has better hydrocarbon potential. Additionally, in earlier sedimentary period of Badaowan Formation, the research area developed delta front sub-facies and shore shallow lake facies. In Shawan depression, the formation developed shore shallow facies and limnetic facies with much organic matter input. The source rock is formed in weak oxidation-strong weak sedimentary environment with high plant input. In Sangonghe Formation sedimentary period, the study area distributed shore shallow lake faices, whose source rock is formed in strong oxidation environment with lacustrine high plant input. In Xishanyao Formation sedimentary period, in Mahu depression, Luliang uplift, and Western Well Pen 1 depression distributed delta plain facies and front plain facies. The sedimentary centre moved to eastern and southern depression with sub-deep lake facies, whose source rock is formed in weak oxidation-strong oxidation environment with high lacustrine plant input.
2013, 31(04): 571-579.
Abstract:
The Carboniferous lithofacies paleogeography in Northern Xinjiang was discussed by the combination of analysis on the outcrop and well profiles of volcanic rocks. The comprehensive study of borehole data, sedimentary facies, sedimentary construction, and Paleontology combination indicates that the overall characteristic of Carboniferous paleogeography in northern Xinjiang evolved from deep sea-half deep sea facies and shallow sea facies in the Early Carboniferous to the shallow sea facies, sea-land transition facies and continental facies in the Late Carboniferous. Rock association types transited from active epicontinental island-arc volcanic rock, abysmal flysch and marine carbonate rock in the Early Carboniferous to riftogenic volcanics, terrestrial clastic, marine clastics and marine carbonate rock in the Late Carboniferous. The tectonic lithofacies paleogeography and rock associations have distinct difference in different regions between Early and Late Carboniferous.
The Carboniferous lithofacies paleogeography in Northern Xinjiang was discussed by the combination of analysis on the outcrop and well profiles of volcanic rocks. The comprehensive study of borehole data, sedimentary facies, sedimentary construction, and Paleontology combination indicates that the overall characteristic of Carboniferous paleogeography in northern Xinjiang evolved from deep sea-half deep sea facies and shallow sea facies in the Early Carboniferous to the shallow sea facies, sea-land transition facies and continental facies in the Late Carboniferous. Rock association types transited from active epicontinental island-arc volcanic rock, abysmal flysch and marine carbonate rock in the Early Carboniferous to riftogenic volcanics, terrestrial clastic, marine clastics and marine carbonate rock in the Late Carboniferous. The tectonic lithofacies paleogeography and rock associations have distinct difference in different regions between Early and Late Carboniferous.
2013, 31(04): 590-599.
Abstract:
The Upper Permian siliceous rocks of Wujiaping Formation develop in Lichuan, southwestern Hubei. Containing radiolarian and sponge, the siliceous rocks appear with stone coal and volcanic claystone. The radiolarian assemblage is dominated by Spumellaria, followed by Entactinaria and rarely Latentifistularia, which represents the outer shelf environment. The siliceous rocks are rich in terrestrial elements (for example Al, Ti), poor in hydrothermal elements (such as Fe, Mn). Their Al/(Al+Fe+Mn) values are 0.64~0.83, with an average of 0.73. In the Al-Fe-Mn ternary, chert samples locate in or close to Non-Hydrothermal siliceous rocks region. In SiO2- (K2O+Na2O), SiO2-Al2O3, (K2O+Na2O)-Al2O3 binary discrimination diagram, samples plot in or near volcano-sedimentary region. Comparing with abundance of trace elements in sedimentary rocks, life elements: Mo and V assemble, hydrothermal elements: Ba, As, Sc deplete. ∑REE is lower and average ΣLREE/ΣHREE is 3.02, with Ce (δCe:0.75~0.83, average 0.79) and Eu (δEu: 0.61~0.95, average 0.84) slight negative anomaly. Their NASC-normalized REE distribution patterns are nearly horizontal. These geochemical characteristics prove that siliceous rocks are formed by volcano sedimentation with biological effect. Redox indexes: U/Th, V/(V+Ni) and Ceanom, sedimentary environment indicators: MnO/TiO2, LaN/YbN and discrimination diagrams: 100×TFe2O3/SiO2-100 Al2O3/SiO2, TFe2O3/(100-SiO2)-Al2O3/(100-SiO2), TFe2O3/TiO2-Al2O3/(Al2O3+TFe2O3), LaN/CeN-Al2O3/(Al2O3+TFe2O3) and ΣLREE/ΣHREE-100×Eu/ΣREE comprehensively make sure that the siliceous rocks deposited in continental shelf under anoxic condition.
The Upper Permian siliceous rocks of Wujiaping Formation develop in Lichuan, southwestern Hubei. Containing radiolarian and sponge, the siliceous rocks appear with stone coal and volcanic claystone. The radiolarian assemblage is dominated by Spumellaria, followed by Entactinaria and rarely Latentifistularia, which represents the outer shelf environment. The siliceous rocks are rich in terrestrial elements (for example Al, Ti), poor in hydrothermal elements (such as Fe, Mn). Their Al/(Al+Fe+Mn) values are 0.64~0.83, with an average of 0.73. In the Al-Fe-Mn ternary, chert samples locate in or close to Non-Hydrothermal siliceous rocks region. In SiO2- (K2O+Na2O), SiO2-Al2O3, (K2O+Na2O)-Al2O3 binary discrimination diagram, samples plot in or near volcano-sedimentary region. Comparing with abundance of trace elements in sedimentary rocks, life elements: Mo and V assemble, hydrothermal elements: Ba, As, Sc deplete. ∑REE is lower and average ΣLREE/ΣHREE is 3.02, with Ce (δCe:0.75~0.83, average 0.79) and Eu (δEu: 0.61~0.95, average 0.84) slight negative anomaly. Their NASC-normalized REE distribution patterns are nearly horizontal. These geochemical characteristics prove that siliceous rocks are formed by volcano sedimentation with biological effect. Redox indexes: U/Th, V/(V+Ni) and Ceanom, sedimentary environment indicators: MnO/TiO2, LaN/YbN and discrimination diagrams: 100×TFe2O3/SiO2-100 Al2O3/SiO2, TFe2O3/(100-SiO2)-Al2O3/(100-SiO2), TFe2O3/TiO2-Al2O3/(Al2O3+TFe2O3), LaN/CeN-Al2O3/(Al2O3+TFe2O3) and ΣLREE/ΣHREE-100×Eu/ΣREE comprehensively make sure that the siliceous rocks deposited in continental shelf under anoxic condition.
2013, 31(04): 608-615.
Abstract:
KT-I is one of the most important oil bearing series in M block of Pre-Caspian basin. The reservoir spreading is not clear understanding with varied types of facies belts, severe heterogeneity and limestone interbedded with mudstone. In terms of high-frequency sequence stratigraphy, the feasibility and thought of tract system division in high-frequency sequence and super sequence is put forward. And the drowning unconformity plays an important part as carbonate sequence boundary. On this basis, by the recognition of sequence boundary, such as drowning unconformity and exposed punctuated surface, KT-I member has been for the first time divided into 3 fourth level sequence and 9 fifth level sequence and the system tract of high-frequency sequence has also been done. The system tract model of high-frequency sequence on rapid transgression (equivalent to drowning unconformity) and slow transgression condition has been established. Then, the developing features of strata and the reservoir spreading in study area have been clear. The application of drowning unconformity and the system tracts of high-frequency sequence in carbonate petroleum exploration has been summarized at last.
KT-I is one of the most important oil bearing series in M block of Pre-Caspian basin. The reservoir spreading is not clear understanding with varied types of facies belts, severe heterogeneity and limestone interbedded with mudstone. In terms of high-frequency sequence stratigraphy, the feasibility and thought of tract system division in high-frequency sequence and super sequence is put forward. And the drowning unconformity plays an important part as carbonate sequence boundary. On this basis, by the recognition of sequence boundary, such as drowning unconformity and exposed punctuated surface, KT-I member has been for the first time divided into 3 fourth level sequence and 9 fifth level sequence and the system tract of high-frequency sequence has also been done. The system tract model of high-frequency sequence on rapid transgression (equivalent to drowning unconformity) and slow transgression condition has been established. Then, the developing features of strata and the reservoir spreading in study area have been clear. The application of drowning unconformity and the system tracts of high-frequency sequence in carbonate petroleum exploration has been summarized at last.
2013, 31(04): 621-629.
Abstract:
Cherts of the Late Permian occurred extensively in the Dian-Qian-Gui region, which provide critical information with respect to the study of tectonic setting and the formation of sedimentary basins. At present most attention has been focused on Guangxi and Southwestern Guizhou, however , few relevant research has been carried out in Southeast Yunnan. Based on petrogeology and geochemistry , the Wuchiapingian cherts of Upper Permian of Qiubei region，Southeast Yunnan have been systematically studied. The results show that all samples except P29 have much higher SiO2/Al2O3 ratios (>80),Al/（Al+Fe+Mn） ratio between 0.46 and 0.76;Ce/Ce* andLaN/CeNratios are 0.517~0.858 and 1.12~1.80, respectively; Chondrite-normalized REE patterns of the cherts characterized by significant negative Eu anomalies and LREE enrichment; Besides, the NASC-normalized Eu/Eu* ratio of P29 is 1.129. Combining with the published geochemical data of cherts from the equivalent horizons of Dongpan and Laibin region, we draw a conclusion that (1) The cherts of Qiubei and Dongpan region developed in a setting of continental marginal in the late Permian , and terrestrial debris is the main material source of the cherts of Dongpan. Meanwhile, the cherts of Qiubei are characteristic of biogenesis, and received little terrigenous input, and those of Laibin were deposited in an ocean basin with influence of submarine hydrothermal fluid and no input of terrigenous materials; the Eu/Eu*ratio of P29 is 1.129, which reflects its hydrothermal influence and implies the movement from both（either）Emeishan Mantle and（or）regional fault; During the late Permian, the water depth of Qiubei region deepen gradually from west to east with low water energy.
Cherts of the Late Permian occurred extensively in the Dian-Qian-Gui region, which provide critical information with respect to the study of tectonic setting and the formation of sedimentary basins. At present most attention has been focused on Guangxi and Southwestern Guizhou, however , few relevant research has been carried out in Southeast Yunnan. Based on petrogeology and geochemistry , the Wuchiapingian cherts of Upper Permian of Qiubei region，Southeast Yunnan have been systematically studied. The results show that all samples except P29 have much higher SiO2/Al2O3 ratios (>80),Al/（Al+Fe+Mn） ratio between 0.46 and 0.76;Ce/Ce* andLaN/CeNratios are 0.517~0.858 and 1.12~1.80, respectively; Chondrite-normalized REE patterns of the cherts characterized by significant negative Eu anomalies and LREE enrichment; Besides, the NASC-normalized Eu/Eu* ratio of P29 is 1.129. Combining with the published geochemical data of cherts from the equivalent horizons of Dongpan and Laibin region, we draw a conclusion that (1) The cherts of Qiubei and Dongpan region developed in a setting of continental marginal in the late Permian , and terrestrial debris is the main material source of the cherts of Dongpan. Meanwhile, the cherts of Qiubei are characteristic of biogenesis, and received little terrigenous input, and those of Laibin were deposited in an ocean basin with influence of submarine hydrothermal fluid and no input of terrigenous materials; the Eu/Eu*ratio of P29 is 1.129, which reflects its hydrothermal influence and implies the movement from both（either）Emeishan Mantle and（or）regional fault; During the late Permian, the water depth of Qiubei region deepen gradually from west to east with low water energy.
2013, 31(04): 646-652.
Abstract:
Based on radiocarbon dating of 210Pb, the grain size of lacustrine sediment in Wuliangsu Lake was analyzed. Comparing with historical documents, the environmental evolution under the combined effects of natural and human activities was studied in Wuliangsu Lake region, Inner Mongolia. The average content for clay (<4 μm), fine silt (4~16 μm), medium silt (16~32μm), coarse silt (32~64 μm), fine sand (>64 μm), is 28.7%, 34.4%, 17.3%, 14.1%, 5.5%, respectively. Through the correlation analysis of different grain size contents, the grain size characteristic changed significantly around 1965 AD in Wuliangsu Lake. Based on this result, with the method of grain size vs. standard deviation, the sediment sources were extracted in the two stages before and after 1965AD. The results show that: the sources of lake sediment are composed of materials from Yellow River and topsoil erosion in Hetao irrigation. But in the tow stages, the grain size characteristics of different populations in lake sediment have obvious differences. Before 1965 AD, the fine grainsize populations (<19.95 μm) are from the topsoil erosion in Hetao irrigation, and the other coarse grain-size populations (19.95~181.97 μm) are carried by Yellow River, which dominated grain size characteristic of the whole Wuliangsu lake sediment. After 1965 AD, the gain size of the fine and coarse population are <5.71 μm and 5.71~60.56 μm, respectively, but the fine grain-size one dominated the lake sediment characteristic, which are consistent with runoff of the main drainage canal in Hetao Plain. Overall, since the 1960s, lake sediments in Wuliangsu were mostly imposed by human influence, which has exceeded the natural role.
Based on radiocarbon dating of 210Pb, the grain size of lacustrine sediment in Wuliangsu Lake was analyzed. Comparing with historical documents, the environmental evolution under the combined effects of natural and human activities was studied in Wuliangsu Lake region, Inner Mongolia. The average content for clay (<4 μm), fine silt (4~16 μm), medium silt (16~32μm), coarse silt (32~64 μm), fine sand (>64 μm), is 28.7%, 34.4%, 17.3%, 14.1%, 5.5%, respectively. Through the correlation analysis of different grain size contents, the grain size characteristic changed significantly around 1965 AD in Wuliangsu Lake. Based on this result, with the method of grain size vs. standard deviation, the sediment sources were extracted in the two stages before and after 1965AD. The results show that: the sources of lake sediment are composed of materials from Yellow River and topsoil erosion in Hetao irrigation. But in the tow stages, the grain size characteristics of different populations in lake sediment have obvious differences. Before 1965 AD, the fine grainsize populations (<19.95 μm) are from the topsoil erosion in Hetao irrigation, and the other coarse grain-size populations (19.95~181.97 μm) are carried by Yellow River, which dominated grain size characteristic of the whole Wuliangsu lake sediment. After 1965 AD, the gain size of the fine and coarse population are <5.71 μm and 5.71~60.56 μm, respectively, but the fine grain-size one dominated the lake sediment characteristic, which are consistent with runoff of the main drainage canal in Hetao Plain. Overall, since the 1960s, lake sediments in Wuliangsu were mostly imposed by human influence, which has exceeded the natural role.
2013, 31(04): 663-671.
Abstract:
According to the characteristics of detrital minerals in downstream floodplain sediments from seven rivers around Liaodong Bay, detrital mineral assemblages among the rivers, and impacts of rocks in drainage basin and sediment grain size on detrital mineral assemblages were analyzed. Light mineral assemblages are mainly Quartz, Plagioclase and Potassium Feldspar. Because rivers flowing in western Liaodong Bay (Liuguhe, Xiaolinhe, Dalinghe) and rivers flowing in eastern Liaodong Bay (Shuangtaizihe, Daliaohe, Fuzhouhe) are located on two tectonic blocks separately, different rock types in drainage basin lead to prominent discrepancies of heavy mineral assemblage in river sediments. The western rivers are characterized by low hornblende and high metal minerals, but the eastern rivers are reverse, so that these two compositions can identify rivers flowing in western and eastern Liaodong Bay effectively, and they can also separate Luanhe sediment from rivers in Liaoning. The garnet and augite can distinguish the three rivers flowing in western Liaodong Bay, because content of the garnet is high in Dalinghe, the augite is high in Xiaolinghe, and both are low in Liuguhe. The epidote and actinolite can differentiate the three rivers flowing in eastern Liaodong Bay, because content of the epidote is high in Shuangtaizihe, the actinolite is high in Daliaohe, and both are low in Fuzhouhe. Low contents characteristics of schistose minerals and carbonate minerals of these seven rivers are different from Huanghe sediments.
According to the characteristics of detrital minerals in downstream floodplain sediments from seven rivers around Liaodong Bay, detrital mineral assemblages among the rivers, and impacts of rocks in drainage basin and sediment grain size on detrital mineral assemblages were analyzed. Light mineral assemblages are mainly Quartz, Plagioclase and Potassium Feldspar. Because rivers flowing in western Liaodong Bay (Liuguhe, Xiaolinhe, Dalinghe) and rivers flowing in eastern Liaodong Bay (Shuangtaizihe, Daliaohe, Fuzhouhe) are located on two tectonic blocks separately, different rock types in drainage basin lead to prominent discrepancies of heavy mineral assemblage in river sediments. The western rivers are characterized by low hornblende and high metal minerals, but the eastern rivers are reverse, so that these two compositions can identify rivers flowing in western and eastern Liaodong Bay effectively, and they can also separate Luanhe sediment from rivers in Liaoning. The garnet and augite can distinguish the three rivers flowing in western Liaodong Bay, because content of the garnet is high in Dalinghe, the augite is high in Xiaolinghe, and both are low in Liuguhe. The epidote and actinolite can differentiate the three rivers flowing in eastern Liaodong Bay, because content of the epidote is high in Shuangtaizihe, the actinolite is high in Daliaohe, and both are low in Fuzhouhe. Low contents characteristics of schistose minerals and carbonate minerals of these seven rivers are different from Huanghe sediments.
Accumulation Mechanisms and Modes of Yanchang Formation Chang 8 Interval Hydrocarbons in Ordos Basin
2013, 31(04): 683-692.
Abstract:
The exploration and reservoir scale are of differences in different regions of Chang8 interval of Yanchang Formation in Ordos Basin Ordos, in order to clarify the difference reason, oil source, reservoir characteristics, the capillary force, buoyancy and the excess pressure are studied on Chang 8 reservoir. The excess pressure is much greater than the capillary force, source and reservoir pressure can overcome the corresponding reservoir capillary force and migration and accumulation. On this basis, according to the Jiyuan area, Longdong area and Shanbei area of hydrocarbon source rock and reservoir development characteristics, physical properties and migration channel characteristic, built three kinds of different reservoir forming pattern. Jiyuan area is two-way expulsion, composite reservoir model: Chang 7 source rocks of abnormal development, pressurization action of hydrocarbon generation is strong, which makes the generated hydrocarbon fluid in excess pressure driven to overlying the Chang 6 and Chang 4+5 formation and the underlying Chang 8 strata in bidirectional expulsion, in multi-layer accumulation; Longdong area is the upper source and below-storage reservoir，the lower reservoir model: Chang 7 source rocks, higher in the presence of excess pressure, underlying Chang 8 reservoir was superior to the overlying the Chang 6 reservoir, favorable hydrocarbon mass downward migration, accumulation in Chang 8; Shanbei area is the upper lateral migration, the upper reservoir model: Chang 7 hydrocarbon source rocks are not developed in this area, and overlying Chang 6 reservoir is far superior to that of the underlying Chang 8 reservoir, hydrocarbon priority in Chang 6 reservoir, due to the limited size of Chang 8 reservoir. The three accumulation models represented with Chang 7 as the main hydrocarbon source rock reservoir are the main reservoir forming mechanism; the three models have obvious difference in the distribution of oil and gas.
The exploration and reservoir scale are of differences in different regions of Chang8 interval of Yanchang Formation in Ordos Basin Ordos, in order to clarify the difference reason, oil source, reservoir characteristics, the capillary force, buoyancy and the excess pressure are studied on Chang 8 reservoir. The excess pressure is much greater than the capillary force, source and reservoir pressure can overcome the corresponding reservoir capillary force and migration and accumulation. On this basis, according to the Jiyuan area, Longdong area and Shanbei area of hydrocarbon source rock and reservoir development characteristics, physical properties and migration channel characteristic, built three kinds of different reservoir forming pattern. Jiyuan area is two-way expulsion, composite reservoir model: Chang 7 source rocks of abnormal development, pressurization action of hydrocarbon generation is strong, which makes the generated hydrocarbon fluid in excess pressure driven to overlying the Chang 6 and Chang 4+5 formation and the underlying Chang 8 strata in bidirectional expulsion, in multi-layer accumulation; Longdong area is the upper source and below-storage reservoir，the lower reservoir model: Chang 7 source rocks, higher in the presence of excess pressure, underlying Chang 8 reservoir was superior to the overlying the Chang 6 reservoir, favorable hydrocarbon mass downward migration, accumulation in Chang 8; Shanbei area is the upper lateral migration, the upper reservoir model: Chang 7 hydrocarbon source rocks are not developed in this area, and overlying Chang 6 reservoir is far superior to that of the underlying Chang 8 reservoir, hydrocarbon priority in Chang 6 reservoir, due to the limited size of Chang 8 reservoir. The three accumulation models represented with Chang 7 as the main hydrocarbon source rock reservoir are the main reservoir forming mechanism; the three models have obvious difference in the distribution of oil and gas.
2013, 31(04): 699-705.
Abstract:
The new method was created to solve the two concealing and key problems about reservoir prediction in deep water area, which are electricity log defect in recognizing deep water gravity flow sediments(DW fan),especially claystone, and seismic data hard to be used to delineate the thin interbedded sandstone and claystone within DW fan. Firstly, according to obvious seismic reflective characteristics, put forward plane-line-point study method for DW fan. First step, based on the seismic attributes, build DW fan deposition model; second step, create reversed seismic to well tie to identify the top and bottom of DW fan on the well log section, research sedimentary micro-face, classify DW fan into five kind of sedimentary units, accurately calculate the net to gross (NTG) of five kind of units of DW fan. Then choose the appropriate seismic attributes to build their correlation with NTG, and transfer the seismic attribute map into the NTG map and sandstone thickness map with different sedimentary unit seismic attribute and NTG correlation formula.
The new method was created to solve the two concealing and key problems about reservoir prediction in deep water area, which are electricity log defect in recognizing deep water gravity flow sediments(DW fan),especially claystone, and seismic data hard to be used to delineate the thin interbedded sandstone and claystone within DW fan. Firstly, according to obvious seismic reflective characteristics, put forward plane-line-point study method for DW fan. First step, based on the seismic attributes, build DW fan deposition model; second step, create reversed seismic to well tie to identify the top and bottom of DW fan on the well log section, research sedimentary micro-face, classify DW fan into five kind of sedimentary units, accurately calculate the net to gross (NTG) of five kind of units of DW fan. Then choose the appropriate seismic attributes to build their correlation with NTG, and transfer the seismic attribute map into the NTG map and sandstone thickness map with different sedimentary unit seismic attribute and NTG correlation formula.
2013, 31(04): 717-723.
Abstract:
The analysis of Cretaceous Bashijiqike Formation 3rd member reservoir finds the similarities and differences between Suohan outcrop and Dabei gas field in Kuqa depression of Tarim Basin. They both have the similar depositional environment and characteristics: both of them mainly deposited fan delta frontal surfaces. Their petrological characteristics are of slightly different. But obvious difference exists in the reservoir property and reservoir space. The physical properties of outcrop are much better with the porosity of 13%~18% and the permeability of 1×103~100×103 m2while the data of Dabei gas field are 2%~7% and 0.01×103~1×103 m2. Meanwhile the reservoir space types are drastically disparate. The reasons of the differences lay in that Bashijiqike formation 3rd member of Suohan outcrop has ever experienced from shallow burial, low compaction, weak exposure and modern weathering and leaching reformation which Dabei gas field has not. It has important significance to realize reservoir property and reservoir evaluation on tight sandstone and fractured reservoir in Kuqa depression.
The analysis of Cretaceous Bashijiqike Formation 3rd member reservoir finds the similarities and differences between Suohan outcrop and Dabei gas field in Kuqa depression of Tarim Basin. They both have the similar depositional environment and characteristics: both of them mainly deposited fan delta frontal surfaces. Their petrological characteristics are of slightly different. But obvious difference exists in the reservoir property and reservoir space. The physical properties of outcrop are much better with the porosity of 13%~18% and the permeability of 1×103~100×103 m2while the data of Dabei gas field are 2%~7% and 0.01×103~1×103 m2. Meanwhile the reservoir space types are drastically disparate. The reasons of the differences lay in that Bashijiqike formation 3rd member of Suohan outcrop has ever experienced from shallow burial, low compaction, weak exposure and modern weathering and leaching reformation which Dabei gas field has not. It has important significance to realize reservoir property and reservoir evaluation on tight sandstone and fractured reservoir in Kuqa depression.
2013, 31(04): 730-737.
Abstract:
Salt lake source rock rich in gypsum and salt, these compounds makes the logging response of source rock change significantly. Based on the experimental data, the relationships between TOC and log information of gypsum (salt)-bearing mudstone, gypsum (salt) mudstone and mudstone have been studied. Research shows that: TOC of mudstone and gypsum-bearing mudstone is proportional to AC and LogRt, inversely proportional to DEN. TOC of gypsum(salt) mudstone is proportional to DEN and inversely proportional to LogRt. Based on the results of this research, the evaluation method of salt lake source rocks by logging information has been established. First, distinguish the types of source rocks by ΔGR, then TOC evaluation model of different kinds of lithology is established on the basis of experiment data. finally, the correlation between the experimentally measured S1+S2and TOC has been studied, so that the TOC and hydrocarbon potential of source rocks can be calculated by log data. The characteristics and distribution of lower submember of 4th member of Shahejie formation source rock are studied in this way. The study found that a high degree of agreement between the predicted TOC and experimented TOC which proves the method has some promotional value.
Salt lake source rock rich in gypsum and salt, these compounds makes the logging response of source rock change significantly. Based on the experimental data, the relationships between TOC and log information of gypsum (salt)-bearing mudstone, gypsum (salt) mudstone and mudstone have been studied. Research shows that: TOC of mudstone and gypsum-bearing mudstone is proportional to AC and LogRt, inversely proportional to DEN. TOC of gypsum(salt) mudstone is proportional to DEN and inversely proportional to LogRt. Based on the results of this research, the evaluation method of salt lake source rocks by logging information has been established. First, distinguish the types of source rocks by ΔGR, then TOC evaluation model of different kinds of lithology is established on the basis of experiment data. finally, the correlation between the experimentally measured S1+S2and TOC has been studied, so that the TOC and hydrocarbon potential of source rocks can be calculated by log data. The characteristics and distribution of lower submember of 4th member of Shahejie formation source rock are studied in this way. The study found that a high degree of agreement between the predicted TOC and experimented TOC which proves the method has some promotional value.
