2009 Vol. 27, No. 4
Display Method:
2009, 27(4): 573-582.
Abstract:
The trace fossils in the Heshanggou Formation consist of at least 9 ichnogenus and 10 ichnospecies, namely, Arenicolites isp., Beaconites coronus, Cylindricum isp., Palaeophycus heberti, Palaeophycus tubularis, Planolites isp., Psilonichnus isp., Scoyenia gracilis, Skolithos linearis and Taenidium barretti. Based on the distribution of trace fossils and analysis of palaeoenvironment, three ichnofabrics are recognized: 1) Scoyenia ichnofabric, which represents shore lacustrine depositional environment under arid climate; 2) PlanolitesTaenidium ichnofabric, which formed in a shallow lacustrine sedimentary environment, and the substrate did not expose to the surface; 3) Psilonichnus ichnofabric, which generated in a lacustrine delta sedimentary environment and shows the hydrodynamic becoming more and more strongly in sequence.
The trace fossils in the Heshanggou Formation consist of at least 9 ichnogenus and 10 ichnospecies, namely, Arenicolites isp., Beaconites coronus, Cylindricum isp., Palaeophycus heberti, Palaeophycus tubularis, Planolites isp., Psilonichnus isp., Scoyenia gracilis, Skolithos linearis and Taenidium barretti. Based on the distribution of trace fossils and analysis of palaeoenvironment, three ichnofabrics are recognized: 1) Scoyenia ichnofabric, which represents shore lacustrine depositional environment under arid climate; 2) PlanolitesTaenidium ichnofabric, which formed in a shallow lacustrine sedimentary environment, and the substrate did not expose to the surface; 3) Psilonichnus ichnofabric, which generated in a lacustrine delta sedimentary environment and shows the hydrodynamic becoming more and more strongly in sequence.
2009, 27(4): 592-605.
Abstract:
Three sedimentary layers including Shahezi Formation, Yingcheng Formation, Denglouku Formation and four faultdepressed blocks developed in lower Cretaceous layers of BinxianSuihua area in the north of Songliao Basin. Six seismic facies developed in the area through the characteristic analysis on the amplitude, continuance, inner structure and formalness of the seismic reflection stratum. Through the data of multidisciplinary analysis with the outcrop, core observation and description, drillingwell logging, laboratory test and especially the seismic facies interpretation, six styles of sedimentary facies formed in lower Cretaceous layers are alluvial fan facies, fluvial facies, fandelta facies, braided streamdelta facies, lacustrine facies, and volcanite facies, respectively. Through analyzed the plane distributed and developed character of the sedimentary facies in different layers, it was concluded that the lower Cretaceous layers were made up of coarse sediments mainly in the fault subsidence period. The sedimentary provenance which was controlled by the major fault came from the arctic region near the major fault in each fault depression. The fine grained sediments were favorable for the source rock and the coarse sediments of the overlying were favorable reservoir. The result was that Binxian and Beian fault depression maybe the priority area for the oil and gas exploration in the future.
Three sedimentary layers including Shahezi Formation, Yingcheng Formation, Denglouku Formation and four faultdepressed blocks developed in lower Cretaceous layers of BinxianSuihua area in the north of Songliao Basin. Six seismic facies developed in the area through the characteristic analysis on the amplitude, continuance, inner structure and formalness of the seismic reflection stratum. Through the data of multidisciplinary analysis with the outcrop, core observation and description, drillingwell logging, laboratory test and especially the seismic facies interpretation, six styles of sedimentary facies formed in lower Cretaceous layers are alluvial fan facies, fluvial facies, fandelta facies, braided streamdelta facies, lacustrine facies, and volcanite facies, respectively. Through analyzed the plane distributed and developed character of the sedimentary facies in different layers, it was concluded that the lower Cretaceous layers were made up of coarse sediments mainly in the fault subsidence period. The sedimentary provenance which was controlled by the major fault came from the arctic region near the major fault in each fault depression. The fine grained sediments were favorable for the source rock and the coarse sediments of the overlying were favorable reservoir. The result was that Binxian and Beian fault depression maybe the priority area for the oil and gas exploration in the future.
2009, 27(4): 614-621.
Abstract:
Based on the sedimentology, palaeontology and geochemistry, the sedimentary system of tidal flatlagoon were developed in the Carboniferous Kalashayi Formation in the south of Tahe oilfield from the studies of cores, well logs, palaeontology and geochemistry. The upper sandshale section of the Kalashayi Formation developed feathering crossbedding, wave bedding, lensing bedding, thin sand and mudstone interaction layers, low ration of sand to strata ,brackish water or vastsalinity creatures, all of them reflect an environment of tidal flat. In plane, the sand of the north of region of interest is coarser and contains gravels, that reflects there are rivers filling in. So this is a sedimentary system of tidal flat which has a nature of estuary. The Kalashayi Formation sandshale section was in intertidal zone, including tidal channel, sand flat, sandmud mixed flat, mouth bar microfacies. Upmudstone section includes darkgrey, greybrown and brown mudstone which occasionally contains thin pelitic siltstone，calcareous mudstone belt, developed parallel bedding, it is lagoonal facies. Finally, the sedimentary model of tidal flat with estuary has been established.
Based on the sedimentology, palaeontology and geochemistry, the sedimentary system of tidal flatlagoon were developed in the Carboniferous Kalashayi Formation in the south of Tahe oilfield from the studies of cores, well logs, palaeontology and geochemistry. The upper sandshale section of the Kalashayi Formation developed feathering crossbedding, wave bedding, lensing bedding, thin sand and mudstone interaction layers, low ration of sand to strata ,brackish water or vastsalinity creatures, all of them reflect an environment of tidal flat. In plane, the sand of the north of region of interest is coarser and contains gravels, that reflects there are rivers filling in. So this is a sedimentary system of tidal flat which has a nature of estuary. The Kalashayi Formation sandshale section was in intertidal zone, including tidal channel, sand flat, sandmud mixed flat, mouth bar microfacies. Upmudstone section includes darkgrey, greybrown and brown mudstone which occasionally contains thin pelitic siltstone，calcareous mudstone belt, developed parallel bedding, it is lagoonal facies. Finally, the sedimentary model of tidal flat with estuary has been established.
2009, 27(4): 632-641.
Abstract:
Three sedimentary sequences have been divided in the deep water area from the Paleogene system of ZhujiangkouQiongdongnan basin, i.e. Eocene Wenchang, EnpingYacheng and ZhuhaiLingshui sequences. In combination with the data from well facies, strata isopach, seismic facies and seismic sandstone index maps, together with depositional characteristics of faulted basin and tectonic background, the integrated sedimentary facies maps have been figured out for each systems tract in the study area. Three large lacustrine area were developed in the deep water area around the northern part of South China Sea, including the Baiyun depression in the east, SongnanBaodao depression and Lingshui Ledong depression in the west. During this period, the segment features were obvious,i.e. five or six smallscaled lakes were also developed apart from the three large lake basins. During the early Eocene, the sea transgression area was mainly in Qiongdongnan basin, and sea water was probably flushed into the basin from both the west and east directions to form two shallow sea areas divided by the erosion area while the Baiyun depression was not influenced by sea transgression to keep lacustrine environment. At the same time, ShundeKaiping depression also maintained the lacustrine environment which was gradually enlarged from small lakes into the united giant lake. During the late period, the overall sea transgression took place in the study area, but there existed the difference of transgression directions, e.g. the sea water emplaced from the east in the BaiyunShundeKaiping depression, and there might exist two sea mouths in the Qiongdongnan basin for sea transgression which inherited the sea flushing direction of Yachengnian.
Three sedimentary sequences have been divided in the deep water area from the Paleogene system of ZhujiangkouQiongdongnan basin, i.e. Eocene Wenchang, EnpingYacheng and ZhuhaiLingshui sequences. In combination with the data from well facies, strata isopach, seismic facies and seismic sandstone index maps, together with depositional characteristics of faulted basin and tectonic background, the integrated sedimentary facies maps have been figured out for each systems tract in the study area. Three large lacustrine area were developed in the deep water area around the northern part of South China Sea, including the Baiyun depression in the east, SongnanBaodao depression and Lingshui Ledong depression in the west. During this period, the segment features were obvious,i.e. five or six smallscaled lakes were also developed apart from the three large lake basins. During the early Eocene, the sea transgression area was mainly in Qiongdongnan basin, and sea water was probably flushed into the basin from both the west and east directions to form two shallow sea areas divided by the erosion area while the Baiyun depression was not influenced by sea transgression to keep lacustrine environment. At the same time, ShundeKaiping depression also maintained the lacustrine environment which was gradually enlarged from small lakes into the united giant lake. During the late period, the overall sea transgression took place in the study area, but there existed the difference of transgression directions, e.g. the sea water emplaced from the east in the BaiyunShundeKaiping depression, and there might exist two sea mouths in the Qiongdongnan basin for sea transgression which inherited the sea flushing direction of Yachengnian.
2009, 27(4): 650-656.
Abstract:
As the important source rock layers in SunwuJiayin basin, Taipinglinchang Formation can be compared with Nenjiang Formation well that suffered the transgression. The analysis of major element, microelement and isotope indicate that the characters of high salinity and strong reduction at the bottom of Taipinglinchang Formation are in consistence with the characters of Nenjiang Formation. There is the upwardsdecreasing trend in salinity and reduction. In addition to the palaeoclimate and palaeobiology, it is believed that SunwuJiayin basin was the part of big Songliao basin in the early Cretaceous. Taipinglinchang Formation and Nenjiang Formation deposited in the same lake and suffered the transgression. The sedimentary circumstance of Taipinglinchang Formation is ideal for the organic matter accumulation and transferring to hydrocarbon in the source rock, which provide the material foundation of oil and gas generation.
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As the important source rock layers in SunwuJiayin basin, Taipinglinchang Formation can be compared with Nenjiang Formation well that suffered the transgression. The analysis of major element, microelement and isotope indicate that the characters of high salinity and strong reduction at the bottom of Taipinglinchang Formation are in consistence with the characters of Nenjiang Formation. There is the upwardsdecreasing trend in salinity and reduction. In addition to the palaeoclimate and palaeobiology, it is believed that SunwuJiayin basin was the part of big Songliao basin in the early Cretaceous. Taipinglinchang Formation and Nenjiang Formation deposited in the same lake and suffered the transgression. The sedimentary circumstance of Taipinglinchang Formation is ideal for the organic matter accumulation and transferring to hydrocarbon in the source rock, which provide the material foundation of oil and gas generation.
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2009, 27(4): 667-673.
Abstract:
Commonly used methods to quantify or semiquantify rock textures are estimating through naked eyes, or through visual comparison charts, dotcounting, and image analyses. However, using Adobe Photoshop is better than any other methods. Based on its strong ability of selecting, Photoshop can tell the pixels of each interested texture constituents, and the ratios of them to the total pixel of each whole image equal to the area percents of those constituents. Therefore, using Adobe Photoshop, we can get most of the rock texture data so that the diageneses and porosity evolution history could possibly be recovered. An example from Northeastern Sichuan Basin is studied, which proves the applicability and the accuracy of this method.
Commonly used methods to quantify or semiquantify rock textures are estimating through naked eyes, or through visual comparison charts, dotcounting, and image analyses. However, using Adobe Photoshop is better than any other methods. Based on its strong ability of selecting, Photoshop can tell the pixels of each interested texture constituents, and the ratios of them to the total pixel of each whole image equal to the area percents of those constituents. Therefore, using Adobe Photoshop, we can get most of the rock texture data so that the diageneses and porosity evolution history could possibly be recovered. An example from Northeastern Sichuan Basin is studied, which proves the applicability and the accuracy of this method.
2009, 27(4): 674-683.
Abstract:
On the basis of grain size analysis of the samples from three boreholes in Changjiang Estuary, the present study discusses the sedimentary and morphologic environmental evolution throughout the late Cenozoic era. Results demonstrate that, thick layers of sand and gravelly sand dominate in the borehole sediments of Core SG6 and J18A in Pliocene, indicating quick deposition of alluvial fan system. The lack of Pliocene sedimentation in the borehole of Core SG13 indicates higher topography. Therefore obvious relief occurred in the study area with both depositional and erosion areas during Pliocene. In early Pleistocene the sedimentary environment remained as alluvial fans. But the sedimentary basin extended westward and southward due to tectonic subsidence, as evidenced by the thick layers of gravelly sand in Core J18A and initiation of deposition in Core SG13. In middle Pleistocene fine sediments accumulated generally, revealing the sedimentary environment of alluvial plain dominated by meandering river. In early late Pleistocene thick layers of sand and gravelly sand dominate in the region again, but the grain size become finer as compared with Pliocene and early Pleistocene. It reveals that rivers developed again in the region because of local tectonic subsidence. In late Pleistocene and Holocene silt and clay accumulated from still water dominate in the boreholes sediments, indicating the sedimentary environment of coastal plain and shallow sea. Hence two processes of peneplaintion occurred in the region due to the tectonic subsidence, deposition and erosion since Pliocene to middle Pleistocene and late Pleistocene to Holocene.
On the basis of grain size analysis of the samples from three boreholes in Changjiang Estuary, the present study discusses the sedimentary and morphologic environmental evolution throughout the late Cenozoic era. Results demonstrate that, thick layers of sand and gravelly sand dominate in the borehole sediments of Core SG6 and J18A in Pliocene, indicating quick deposition of alluvial fan system. The lack of Pliocene sedimentation in the borehole of Core SG13 indicates higher topography. Therefore obvious relief occurred in the study area with both depositional and erosion areas during Pliocene. In early Pleistocene the sedimentary environment remained as alluvial fans. But the sedimentary basin extended westward and southward due to tectonic subsidence, as evidenced by the thick layers of gravelly sand in Core J18A and initiation of deposition in Core SG13. In middle Pleistocene fine sediments accumulated generally, revealing the sedimentary environment of alluvial plain dominated by meandering river. In early late Pleistocene thick layers of sand and gravelly sand dominate in the region again, but the grain size become finer as compared with Pliocene and early Pleistocene. It reveals that rivers developed again in the region because of local tectonic subsidence. In late Pleistocene and Holocene silt and clay accumulated from still water dominate in the boreholes sediments, indicating the sedimentary environment of coastal plain and shallow sea. Hence two processes of peneplaintion occurred in the region due to the tectonic subsidence, deposition and erosion since Pliocene to middle Pleistocene and late Pleistocene to Holocene.
2009, 27(4): 691-696.
Abstract:
Based on the analyses of grainsize characteristics for lacustrine sediments in Kusai lake, compared with grainsize characteristics of trapped aeolian dust, the results indicate that the coarse grain component(>64 μm) are carried by wind action, recording the duststorm history of this area. The reconstructed duststorm sequence show: 2 500～800 cal aBP was the period with the highest frequency for duststorm events, while during 4 000～2 500 cal aBP and 800～0 cal aBP the frequency were lower correspondingly; and the duststorm events in the past 1 000 years were concentrated in the three cooling events stages of LIA. Comparative analysis with oxygen isotope records from Dongge Cave reveals that the climatic evolution of Kusai Lake area can be effected by the Asian Monsoon during the past 4 000 years, and the duststorm events occurred frequently during the colddry climate due to the decreased Summer Asian Monsoon.
Based on the analyses of grainsize characteristics for lacustrine sediments in Kusai lake, compared with grainsize characteristics of trapped aeolian dust, the results indicate that the coarse grain component(>64 μm) are carried by wind action, recording the duststorm history of this area. The reconstructed duststorm sequence show: 2 500～800 cal aBP was the period with the highest frequency for duststorm events, while during 4 000～2 500 cal aBP and 800～0 cal aBP the frequency were lower correspondingly; and the duststorm events in the past 1 000 years were concentrated in the three cooling events stages of LIA. Comparative analysis with oxygen isotope records from Dongge Cave reveals that the climatic evolution of Kusai Lake area can be effected by the Asian Monsoon during the past 4 000 years, and the duststorm events occurred frequently during the colddry climate due to the decreased Summer Asian Monsoon.
2009, 27(4): 704-713.
Abstract:
The 10 sediment cores were collected from subaqueous delta of Changjiang estuary in April 2006, using the gravity coring equipment. The length of the cores varied from 100 to 160cm. Following visual inspection for geological parameters and photography of the cores, they were subsampled at 2 cm intervals for the entire length of the cores. Profiles of 210Pb measured in 10 sediment cores were analyzed to elucidate the sediment rates as well as the characteristics of 210Pb. 210Pb (via 210Po) was determined by αspectrometry. Distribution of sedimentation rates reveals that during the last 100 years, the derived sedimentation rates vary from 1.36 to 4.11 cm·yr1, and generally increase seaward the 20m isobaths. In addition, the region from 122°15′E to 122°30′E, i.e. from cores SC05 to SC11, is considered as the mud depocenter in Changjiang estuary, with the mean sediment rates of 3.51cm·yr1. This pattern could coincide with the dispersal of Changjiang Riverderived sediments, with influence by the current and tidal systems. The 210Pb activities of the surfacial sediment vary from 2.15 to 4.22dpm·g1, and 210Pb deposition fluxes from 1.50 to 11.21dpm·cm2·yr1, as well as excess 210Pb inventories between >48.29 and >361.68dpm·cm2, respectively. The excess 210Pb inventories appear to be higher than the theoretical inventory at the subaqueous delta of Changjiang estuary. It is indicated that besides the atmospheric 210Pb fallout, the fluvial inputs could play an important role, whilst the much riverine sediment discharges may be scavenged and deposited at the subaqueous delta of Changjiang estuary.
The 10 sediment cores were collected from subaqueous delta of Changjiang estuary in April 2006, using the gravity coring equipment. The length of the cores varied from 100 to 160cm. Following visual inspection for geological parameters and photography of the cores, they were subsampled at 2 cm intervals for the entire length of the cores. Profiles of 210Pb measured in 10 sediment cores were analyzed to elucidate the sediment rates as well as the characteristics of 210Pb. 210Pb (via 210Po) was determined by αspectrometry. Distribution of sedimentation rates reveals that during the last 100 years, the derived sedimentation rates vary from 1.36 to 4.11 cm·yr1, and generally increase seaward the 20m isobaths. In addition, the region from 122°15′E to 122°30′E, i.e. from cores SC05 to SC11, is considered as the mud depocenter in Changjiang estuary, with the mean sediment rates of 3.51cm·yr1. This pattern could coincide with the dispersal of Changjiang Riverderived sediments, with influence by the current and tidal systems. The 210Pb activities of the surfacial sediment vary from 2.15 to 4.22dpm·g1, and 210Pb deposition fluxes from 1.50 to 11.21dpm·cm2·yr1, as well as excess 210Pb inventories between >48.29 and >361.68dpm·cm2, respectively. The excess 210Pb inventories appear to be higher than the theoretical inventory at the subaqueous delta of Changjiang estuary. It is indicated that besides the atmospheric 210Pb fallout, the fluvial inputs could play an important role, whilst the much riverine sediment discharges may be scavenged and deposited at the subaqueous delta of Changjiang estuary.
2009, 27(4): 723-731.
Abstract:
This paper has introduced an approach which is based on the kinitics method and the software GOREvaluation for quantitative assessment of petroleum generation and expulsion of source rocks through a case study of Sahejie Formation of Linnan sag, Huimin Depression. The key points of the present approach include: an investigation of petroleum generation kinetics parameters of typical source rocks based on their thermal pyrolysis data carried out in a gold tubeautoclave; an investigation of the petroleum generation amount (Hpm) when oil begins to be expulsed from its source rock by combining the modeling results with the plot of EOM/TOCdepth of the source rocks from the Linnan sag; and an establishment of representative geochemical parameters of different types of source rocks by analyzing the available geochemical data. The petroleum generation and expulsion history of the three sets of source rocks from the Linnan Sag (Es13 dark mudstone, Es233 dark mudstone and Es233 dark shale) were investigated by this approach. The results have shown that the Hpm values of the Es233 dark shale and the Es233 dark mudstone are 150 mg/g 与170 mg/g, respectively. The oil threshed and oil expulsion threshed of the Es233 dark shale from the Well X101 occurred at 20 Ma and 13Ma; the Es233 dark mudstone at 19 Ma and 10 Ma; and the Es13 dark mudstone at 8 M and 2 Ma, respectively. The oil generation threshed of the three types of source rocks all occurs at about 0.55% of Easy Ro, but their oil expulsion threshed varies extensively, from 0.61% to 0.69% of EasyRo. It is believed that the merits of the present approach lie in that it avoids enactment of complicated oil expulsion parameters and explanation for oil expulsion mechanism and the results can be applied to quantitative assessment of petroleum generation and expulsion of source rocks, determination of effective source rocks and prediction of petroleum resources.
This paper has introduced an approach which is based on the kinitics method and the software GOREvaluation for quantitative assessment of petroleum generation and expulsion of source rocks through a case study of Sahejie Formation of Linnan sag, Huimin Depression. The key points of the present approach include: an investigation of petroleum generation kinetics parameters of typical source rocks based on their thermal pyrolysis data carried out in a gold tubeautoclave; an investigation of the petroleum generation amount (Hpm) when oil begins to be expulsed from its source rock by combining the modeling results with the plot of EOM/TOCdepth of the source rocks from the Linnan sag; and an establishment of representative geochemical parameters of different types of source rocks by analyzing the available geochemical data. The petroleum generation and expulsion history of the three sets of source rocks from the Linnan Sag (Es13 dark mudstone, Es233 dark mudstone and Es233 dark shale) were investigated by this approach. The results have shown that the Hpm values of the Es233 dark shale and the Es233 dark mudstone are 150 mg/g 与170 mg/g, respectively. The oil threshed and oil expulsion threshed of the Es233 dark shale from the Well X101 occurred at 20 Ma and 13Ma; the Es233 dark mudstone at 19 Ma and 10 Ma; and the Es13 dark mudstone at 8 M and 2 Ma, respectively. The oil generation threshed of the three types of source rocks all occurs at about 0.55% of Easy Ro, but their oil expulsion threshed varies extensively, from 0.61% to 0.69% of EasyRo. It is believed that the merits of the present approach lie in that it avoids enactment of complicated oil expulsion parameters and explanation for oil expulsion mechanism and the results can be applied to quantitative assessment of petroleum generation and expulsion of source rocks, determination of effective source rocks and prediction of petroleum resources.
2009, 27(4): 740-751.
Abstract:
Heshituoluogai basin is located on the northwestern of Jungar basin, and the distribution of the dark mudstone is extensive. According to the geochemical analysis of the Jurassic mudstones form the four infield sections in Hebukehe and Baiyanghe depression, the generated hydrocarbon conditions have been described. The results indicate that the organic richness is high including TOC, chloroform bitumen “A”, total hydrocarbon, (S1+S2). Through the analysis of the vitrinite reflectance of the source rock, Ro is less than 0.65 showing the immature of the source rock, but the results of the basin mod indicate that the maturity of the depression extend the threshold the generated hydrocarbon. In the organic components of Jurassic source rock, the vitrinite is concentrated and especially in the coal, but devoid of intertinite. The relative abundance of richhydrogen exinite is about 20%, including sporophyte, cutinite, resinite, and suberinite commonly, and alginate is accumulated in mudstone, which reflect the strong fluorescent characteristics. So the organic type of mudstone is Ⅱ2, partially Ⅲ. From the analysis of the carbon isotopes of the chloroform bitumen “A” and group compositions, the carbon isotope of coal is heavier than mudstone. The isotope value of nonhydrocarbon in group compositions is lighter, but the aromatic hydrocarbon′s is heavier, which is controlled by the extensive distribution of polycyclic aromatic hydrocarbons in Jurassic source rocks, especially in immature source rocks, suggesting that 12C is accumulated in nonhydrocarbon containing NSO compounds, but 13C is aggregated in polycyclic aromatic hydrocarbons. Also the distribution of molecular biomarkers from the extracts of immature source rocks is particular. In total ion currency profile, nalkanes are distributed by high carbon numbers mainly and hopanoid compounds exit. A Pr/Ph ratio of coal is higher than mudstone. Correlated with the characteristics of the devoid of βcarotene, pregnanes and low gammacerane index, Jurassic source rock is mainly deposited in oxygenated and lacustrine conditions, but xishanyao Formation mudstone is deposited in poor oxic or reductive conditions. Additionally sesquiterpenoid, bicyclic sesquiterpenes and tricyclic terpanes are not exiting in the terpanoids. The regular C27, C28, C29 steranes of coal occur as opposite “L” pattern indicating that the organic matter of Jurassic source rock is originated from the lacustrine high plants, but in Xishanyao formation mudstone, the sterane is distributed by “V” pattern showing the algae input, which is correlated with the distribution of the organic maceral, suggesting the better generation conditions.
Heshituoluogai basin is located on the northwestern of Jungar basin, and the distribution of the dark mudstone is extensive. According to the geochemical analysis of the Jurassic mudstones form the four infield sections in Hebukehe and Baiyanghe depression, the generated hydrocarbon conditions have been described. The results indicate that the organic richness is high including TOC, chloroform bitumen “A”, total hydrocarbon, (S1+S2). Through the analysis of the vitrinite reflectance of the source rock, Ro is less than 0.65 showing the immature of the source rock, but the results of the basin mod indicate that the maturity of the depression extend the threshold the generated hydrocarbon. In the organic components of Jurassic source rock, the vitrinite is concentrated and especially in the coal, but devoid of intertinite. The relative abundance of richhydrogen exinite is about 20%, including sporophyte, cutinite, resinite, and suberinite commonly, and alginate is accumulated in mudstone, which reflect the strong fluorescent characteristics. So the organic type of mudstone is Ⅱ2, partially Ⅲ. From the analysis of the carbon isotopes of the chloroform bitumen “A” and group compositions, the carbon isotope of coal is heavier than mudstone. The isotope value of nonhydrocarbon in group compositions is lighter, but the aromatic hydrocarbon′s is heavier, which is controlled by the extensive distribution of polycyclic aromatic hydrocarbons in Jurassic source rocks, especially in immature source rocks, suggesting that 12C is accumulated in nonhydrocarbon containing NSO compounds, but 13C is aggregated in polycyclic aromatic hydrocarbons. Also the distribution of molecular biomarkers from the extracts of immature source rocks is particular. In total ion currency profile, nalkanes are distributed by high carbon numbers mainly and hopanoid compounds exit. A Pr/Ph ratio of coal is higher than mudstone. Correlated with the characteristics of the devoid of βcarotene, pregnanes and low gammacerane index, Jurassic source rock is mainly deposited in oxygenated and lacustrine conditions, but xishanyao Formation mudstone is deposited in poor oxic or reductive conditions. Additionally sesquiterpenoid, bicyclic sesquiterpenes and tricyclic terpanes are not exiting in the terpanoids. The regular C27, C28, C29 steranes of coal occur as opposite “L” pattern indicating that the organic matter of Jurassic source rock is originated from the lacustrine high plants, but in Xishanyao formation mudstone, the sterane is distributed by “V” pattern showing the algae input, which is correlated with the distribution of the organic maceral, suggesting the better generation conditions.
2009, 27(4): 760-768.
Abstract:
Through study on types and characteristics of lithologic reservoirs of Fuyu oil layer in the northern Honggang, Songliao Basin, four main controlling factors for lithologic reservoirs are: (1) Fault is the most important predominant transporting pathway of overpressure fluid. (2) Overpressure is power of petroleum migrating down. (3) Longterm inherited noselike structure is predominant direction of petroleum lateral migration. (4) Genetic monosandbody traps are minim oilcontrolling units and oilaccumulating units which are controlled by vertical layer and planar sedimentary microfacies. Spatially complicated superposition of vertical multilayer and planar multibranch monosandbody traps and mistraps is essential reason of the complicated distribution of oil and water. It provides a vital foundation for prediction of lithologic traps, analysis of lithologic reservoir forming and study on complicated distribution of oil and water. The model is of great significance to complex exploration and development of lithologic reservoirs.
Through study on types and characteristics of lithologic reservoirs of Fuyu oil layer in the northern Honggang, Songliao Basin, four main controlling factors for lithologic reservoirs are: (1) Fault is the most important predominant transporting pathway of overpressure fluid. (2) Overpressure is power of petroleum migrating down. (3) Longterm inherited noselike structure is predominant direction of petroleum lateral migration. (4) Genetic monosandbody traps are minim oilcontrolling units and oilaccumulating units which are controlled by vertical layer and planar sedimentary microfacies. Spatially complicated superposition of vertical multilayer and planar multibranch monosandbody traps and mistraps is essential reason of the complicated distribution of oil and water. It provides a vital foundation for prediction of lithologic traps, analysis of lithologic reservoir forming and study on complicated distribution of oil and water. The model is of great significance to complex exploration and development of lithologic reservoirs.
2009, 27(4): 583-591.
Abstract:
Jianchang basin is one of the typical basins in Western Liaoning and Northern Hebei region, which contains welldeveloped early Cretaceous and produced numerous fossils of Jehol biota. The early Cretaceous includes Yixan Fromation, Jiufotang Fromation and Shahai Formation. The lower and upper parts of Yixan Formaion are volcanic rocks, the middle part is sedimentary rock, which is composed of pale purple, pale yellow conglomerate, pebbled sandstone, sandstone and pale green mudstone. The depositional environment of Yixan Fromation comprises alluvial fan, braided river and lake. The paleocurrent data shows that provenace areas located in NW and SE to the basin during early stage and in NE during late stage. Alluvial fans perpendicular to the strike of the basin indicate a strong tectonism during early stage of Yixan Formation, whereas braided rivers along the strike indicate a relative stable geological setting during late stage.
Jianchang basin is one of the typical basins in Western Liaoning and Northern Hebei region, which contains welldeveloped early Cretaceous and produced numerous fossils of Jehol biota. The early Cretaceous includes Yixan Fromation, Jiufotang Fromation and Shahai Formation. The lower and upper parts of Yixan Formaion are volcanic rocks, the middle part is sedimentary rock, which is composed of pale purple, pale yellow conglomerate, pebbled sandstone, sandstone and pale green mudstone. The depositional environment of Yixan Fromation comprises alluvial fan, braided river and lake. The paleocurrent data shows that provenace areas located in NW and SE to the basin during early stage and in NE during late stage. Alluvial fans perpendicular to the strike of the basin indicate a strong tectonism during early stage of Yixan Formation, whereas braided rivers along the strike indicate a relative stable geological setting during late stage.
2009, 27(4): 606-613.
Abstract:
Based on the data of petrology, mineralogy and paleontology, this paper uses the theory and ways of modern sedimentology, analyzes the test result of microelement, paleosalinity and isotope to research lithofacies paleogeography of Datangian age. The result shows that the clay stone is marine facies deposit in the lower part of aluminum bearing formation; in the upper part, aluminous rock is transitional facies deposit, and the top is continent lakes and marshes facies deposit. It suggests that sedimentary environment of Datangian Age be the base of epicontinental sea which occur during early transgression period and work up to the lagoon and form clay stone deposit, with the aggrandizement of desalination, the lagoon become small, the salinity is reduced to form aluminous rock, at last, it is end with lakes and marshes deposit. Therefore, tracing deposit sequence of aluminum bearing formation, the author believes that aluminum ore is the sediment of marine regression.
Based on the data of petrology, mineralogy and paleontology, this paper uses the theory and ways of modern sedimentology, analyzes the test result of microelement, paleosalinity and isotope to research lithofacies paleogeography of Datangian age. The result shows that the clay stone is marine facies deposit in the lower part of aluminum bearing formation; in the upper part, aluminous rock is transitional facies deposit, and the top is continent lakes and marshes facies deposit. It suggests that sedimentary environment of Datangian Age be the base of epicontinental sea which occur during early transgression period and work up to the lagoon and form clay stone deposit, with the aggrandizement of desalination, the lagoon become small, the salinity is reduced to form aluminous rock, at last, it is end with lakes and marshes deposit. Therefore, tracing deposit sequence of aluminum bearing formation, the author believes that aluminum ore is the sediment of marine regression.
2009, 27(4): 622-631.
Abstract:
BaojishanHonghui Basin is a typical small scale Jurassic coalforming basin located in the east part of the Qilianshan Mountains. The sequence of the Lower to Middle Jurassic strata is deposited in the sedimentary cycle from the alluvial fan and/or fluvial, to lake delta and lacustrine depositional systems, and fill in the half graben type basin formed by extension of postIndosinian Movement .The complex of the alluvial fanbodies are developed in the vicinity of active fault, from where to another side of nonactive sedimentary boundary, there are gradually replaced by fluvial and wetland swamp system. Peat accumulated directly on the wetland in front of alluvial fans, in where the main coal seams with the features of large thickness and simple fingerlike shape are formed. There are eutrophic or low moor peats in the front swamp of alluvial fans, so that the coal beds with high ash content and sulfur content zonation are formed, as the case may be the space relationship between peat swamps and alluvial fan bodies.
BaojishanHonghui Basin is a typical small scale Jurassic coalforming basin located in the east part of the Qilianshan Mountains. The sequence of the Lower to Middle Jurassic strata is deposited in the sedimentary cycle from the alluvial fan and/or fluvial, to lake delta and lacustrine depositional systems, and fill in the half graben type basin formed by extension of postIndosinian Movement .The complex of the alluvial fanbodies are developed in the vicinity of active fault, from where to another side of nonactive sedimentary boundary, there are gradually replaced by fluvial and wetland swamp system. Peat accumulated directly on the wetland in front of alluvial fans, in where the main coal seams with the features of large thickness and simple fingerlike shape are formed. There are eutrophic or low moor peats in the front swamp of alluvial fans, so that the coal beds with high ash content and sulfur content zonation are formed, as the case may be the space relationship between peat swamps and alluvial fan bodies.
2009, 27(4): 642-649.
Abstract:
Based on the analysis of geologic background, hydrothermal material components and rock fabric, we carry out the study of Sr isotopic geochemistry on the lacustrine hydrothermal sedimentary albiteankerite rock of Xiagou Formation, Lower Cretaceous in Qingxi Sag, Jiuquan Basin. The 87Sr／86Sr ratio of hydrothermal sedimentary rock in the study area is 0.712 25～0.717 81 and the average value
0.715 61 is much higher than the 87Sr／86Sr ratio of seawater and basalt of corresponding period and a little higher than the 87Sr／86Sr ratio of the algal limestone, which represents the strontium isotopes composition of lake water in early cretaceous, but lower than the 87Sr／86Sr ratio of underlying siliconaluminum rock. It shows that the thermal fluid is not simplex lake water or mantle magmatic water. The laminated mudmicrocrystallite hydrothermal sedimentary rock is the product of hydrothermal mineral chemical precipitation and the variation range of its 87Sr／86Sr ratio is less, which represent the composition of Srisotope of thermal fluid in homogeneous hot brine pool. The composition of Srisotope of "water bursting breccia rock" which indicates different jet orifice location has major variation, but the composition of Srisotope of hydrothermal breccia and cementation are almost consistent in the same jet orifice, which shows that both of them are the same period and the same resource eruptive flow sediments. From strontium isotope geochemistry characteristics of hydrothermal sedimentary rock in Qingxi sag, Jiuquan Basin, it is primarily speculated that early Cretaceous sublacustrine hydrothermal fluid in the area is the mixed hydrothermal fluid which is constituted of deep circulating lake water and a little of mantlederived magmatic water and full of high radiogenic Sr of underlying siliconaluminum basement rock. The preliminary report and study of strontium isotope composition of lacustrine hydrothermal sedimentary rock will lay foundation for the further research of the early Cretaceous sublacustrine hydrothermal fluid nature, circulatory geodynamic model of the hydrothermal fluid and hydrothermal sedimentary mode.
Based on the analysis of geologic background, hydrothermal material components and rock fabric, we carry out the study of Sr isotopic geochemistry on the lacustrine hydrothermal sedimentary albiteankerite rock of Xiagou Formation, Lower Cretaceous in Qingxi Sag, Jiuquan Basin. The 87Sr／86Sr ratio of hydrothermal sedimentary rock in the study area is 0.712 25～0.717 81 and the average value
0.715 61 is much higher than the 87Sr／86Sr ratio of seawater and basalt of corresponding period and a little higher than the 87Sr／86Sr ratio of the algal limestone, which represents the strontium isotopes composition of lake water in early cretaceous, but lower than the 87Sr／86Sr ratio of underlying siliconaluminum rock. It shows that the thermal fluid is not simplex lake water or mantle magmatic water. The laminated mudmicrocrystallite hydrothermal sedimentary rock is the product of hydrothermal mineral chemical precipitation and the variation range of its 87Sr／86Sr ratio is less, which represent the composition of Srisotope of thermal fluid in homogeneous hot brine pool. The composition of Srisotope of "water bursting breccia rock" which indicates different jet orifice location has major variation, but the composition of Srisotope of hydrothermal breccia and cementation are almost consistent in the same jet orifice, which shows that both of them are the same period and the same resource eruptive flow sediments. From strontium isotope geochemistry characteristics of hydrothermal sedimentary rock in Qingxi sag, Jiuquan Basin, it is primarily speculated that early Cretaceous sublacustrine hydrothermal fluid in the area is the mixed hydrothermal fluid which is constituted of deep circulating lake water and a little of mantlederived magmatic water and full of high radiogenic Sr of underlying siliconaluminum basement rock. The preliminary report and study of strontium isotope composition of lacustrine hydrothermal sedimentary rock will lay foundation for the further research of the early Cretaceous sublacustrine hydrothermal fluid nature, circulatory geodynamic model of the hydrothermal fluid and hydrothermal sedimentary mode.
2009, 27(4): 657-666.
Abstract:
Wunan Oilfield is one of the most important oil and gas fields in Qaidam basin. Its exploration since the beginning of 1957. The Nancan2 Well found industrial oil flow after the oil test in 1979. In recent years, in the Lv6 Well, Lv2 Well, Wu3 Well and Wu4 Well and many much wells were found industrial oil flow in the stratum of N12 and N22. This article aims at clastic reservoir characteristics, diagenesis and the factors influencing on the stratum of N12 and N22. Through analyse the data of at least 30 wells, use the sections, scanning electron microscope , element analysis, mercury porosimetry and many other means studies, the result shows that the sandstone reservoir rocktype are feldspar debris sandstone and debris feldspar sandstone in stratum of N12 and N22 Wunan Oilfield. The main diagenesis types include of clay film (ClayCentral)，the machinemade compaction, cementation，displacement and dissolution. Thereinto cementation and dissolution is the most important diagenesis in the stratum of N12 and N22 in Wunan Oilfield. Porosity mainly distributed in 8% to 18%, the permeability are mainly distributed in the 0.5×103μm210×103μm2, as the lowporosity and permeability reservoir. The main effect factors of reservoir porosity and permeability include sedimentary facies, diagenesis and structure of reservoir, thereinto, the favorable sedimentary facies are distributary channel and estuary (sandstone and siltite facies), secondly, siltstone facies of distal bar, at last, the reservoir quality of thin sand of the bay is poor.
Wunan Oilfield is one of the most important oil and gas fields in Qaidam basin. Its exploration since the beginning of 1957. The Nancan2 Well found industrial oil flow after the oil test in 1979. In recent years, in the Lv6 Well, Lv2 Well, Wu3 Well and Wu4 Well and many much wells were found industrial oil flow in the stratum of N12 and N22. This article aims at clastic reservoir characteristics, diagenesis and the factors influencing on the stratum of N12 and N22. Through analyse the data of at least 30 wells, use the sections, scanning electron microscope , element analysis, mercury porosimetry and many other means studies, the result shows that the sandstone reservoir rocktype are feldspar debris sandstone and debris feldspar sandstone in stratum of N12 and N22 Wunan Oilfield. The main diagenesis types include of clay film (ClayCentral)，the machinemade compaction, cementation，displacement and dissolution. Thereinto cementation and dissolution is the most important diagenesis in the stratum of N12 and N22 in Wunan Oilfield. Porosity mainly distributed in 8% to 18%, the permeability are mainly distributed in the 0.5×103μm210×103μm2, as the lowporosity and permeability reservoir. The main effect factors of reservoir porosity and permeability include sedimentary facies, diagenesis and structure of reservoir, thereinto, the favorable sedimentary facies are distributary channel and estuary (sandstone and siltite facies), secondly, siltstone facies of distal bar, at last, the reservoir quality of thin sand of the bay is poor.
2009, 27(4): 684-690.
Abstract:
Four monitoring sites were selected in Furong Cave, Wulong county of Chongqing China, including two drip water sites and two pool sites, respectively. The pH, temperature and concentration of HCO-3 in water for the four sites were tested in the cave, other water samples are analyzed in the laboratory for the concentration of some main ions (e.g. Mg2+, Ca2+, K+, Na+, SO2+4, etc.). Then the PCO2(Pressure of CO2) and the SIC (Saturation Index of calcite) were calculated with the WATSPEC software, the sediment of carbonate and the relationship between SIc and precipitation in Furong Cave were discussed. Some conclusions were drawn as follows: in most months of monitoring year, the water of the four sites is oversaturated to calcite, which reflected the stalagmites beneath them are in depositing. Activing sediments on a piece of glass which placed under one drip water in Furong Cave confirmed the results of the calculation of SIC. Furthermore, the SIC of drip water was usually higher than that of pool water in the same season. So the temperature and precipitation was well for the deposition in Furong Cave. And the unsaturated period also after the highrainfall month shows that the precipitation had a big effect on the SIC, so the highrainfall is the key factor for the deposition and lead to the alternate over saturation and unsaturation.
Four monitoring sites were selected in Furong Cave, Wulong county of Chongqing China, including two drip water sites and two pool sites, respectively. The pH, temperature and concentration of HCO-3 in water for the four sites were tested in the cave, other water samples are analyzed in the laboratory for the concentration of some main ions (e.g. Mg2+, Ca2+, K+, Na+, SO2+4, etc.). Then the PCO2(Pressure of CO2) and the SIC (Saturation Index of calcite) were calculated with the WATSPEC software, the sediment of carbonate and the relationship between SIc and precipitation in Furong Cave were discussed. Some conclusions were drawn as follows: in most months of monitoring year, the water of the four sites is oversaturated to calcite, which reflected the stalagmites beneath them are in depositing. Activing sediments on a piece of glass which placed under one drip water in Furong Cave confirmed the results of the calculation of SIC. Furthermore, the SIC of drip water was usually higher than that of pool water in the same season. So the temperature and precipitation was well for the deposition in Furong Cave. And the unsaturated period also after the highrainfall month shows that the precipitation had a big effect on the SIC, so the highrainfall is the key factor for the deposition and lead to the alternate over saturation and unsaturation.
2009, 27(4): 697-703.
Abstract:
Magnetic susceptibility of 228 surface sediments, sampled from the offshore between Pingtan to Shantou, were measured with an attempt to understand the distribution characteristics and their dominative factors of magnetic susceptibility in the western Taiwan Strait.The results showed that the values of low frequency mass specific susceptibility(χlf) and frequency dependent susceptibility(χfd%) decreased gradually from shore to offshore, and the values of χlf were apparently higher in area north to the Xiamen Bay than those from the south. Our study also showed that χfd% at the east of Pingtan Island and the coastal areas of Shantou were relatively high Furthermore, it was obvious that the values decline from Pingtan Island to the south. In comparison with previous studies related to sedimentary types and heavy mineral distribution of the western Taiwan Strait, we discovered susceptibility the values were higher in the fine grained sediments nearshore while lower in the coarse grained sediments offshore in the western Taiwan Strait. The values of magnetic susceptibility correlated well with the content of magnetite, suggesting magnetic susceptibility and frequency dependent susceptibility were dominated by sedimentation process and the source of sediments.
Magnetic susceptibility of 228 surface sediments, sampled from the offshore between Pingtan to Shantou, were measured with an attempt to understand the distribution characteristics and their dominative factors of magnetic susceptibility in the western Taiwan Strait.The results showed that the values of low frequency mass specific susceptibility(χlf) and frequency dependent susceptibility(χfd%) decreased gradually from shore to offshore, and the values of χlf were apparently higher in area north to the Xiamen Bay than those from the south. Our study also showed that χfd% at the east of Pingtan Island and the coastal areas of Shantou were relatively high Furthermore, it was obvious that the values decline from Pingtan Island to the south. In comparison with previous studies related to sedimentary types and heavy mineral distribution of the western Taiwan Strait, we discovered susceptibility the values were higher in the fine grained sediments nearshore while lower in the coarse grained sediments offshore in the western Taiwan Strait. The values of magnetic susceptibility correlated well with the content of magnetite, suggesting magnetic susceptibility and frequency dependent susceptibility were dominated by sedimentation process and the source of sediments.
2009, 27(4): 714-722.
Abstract:
Surface sediment samples were collected in the northwestern Shenzhen Bay, China, and then analyzed using by Mastersize 2000 and sieving to obtain grain size data. The results indicate that the silt sediment covers the North Bay with little poorly sorting and poorly sorted coarse sand and gravel in some areas. In order to use the grain size trends analysis model, the geostatistic method is used for the determination of characteristic distance. The geostatistic results are associated with the some “normal” or “abnormal” grainsize parameters in the study area. A variation range is remarkably determined after eliminating some “abnormal” values, which could be considered as the characteristic distance. The grain size trends analysis shows that sediment transport northeastwards in the west bay, and westwards in the Shenzhen River estuary area. Thus, the near shore area adjoining the north coast becomes a net sediment transport converge area. This pattern is highly consistent with the local hydrodynamics. Furthermore, 210Pb dating result suggests that the sedimentation rate in this area is much higher than other area in the bay, which is consistent with the results of grain size trends analysis.
Surface sediment samples were collected in the northwestern Shenzhen Bay, China, and then analyzed using by Mastersize 2000 and sieving to obtain grain size data. The results indicate that the silt sediment covers the North Bay with little poorly sorting and poorly sorted coarse sand and gravel in some areas. In order to use the grain size trends analysis model, the geostatistic method is used for the determination of characteristic distance. The geostatistic results are associated with the some “normal” or “abnormal” grainsize parameters in the study area. A variation range is remarkably determined after eliminating some “abnormal” values, which could be considered as the characteristic distance. The grain size trends analysis shows that sediment transport northeastwards in the west bay, and westwards in the Shenzhen River estuary area. Thus, the near shore area adjoining the north coast becomes a net sediment transport converge area. This pattern is highly consistent with the local hydrodynamics. Furthermore, 210Pb dating result suggests that the sedimentation rate in this area is much higher than other area in the bay, which is consistent with the results of grain size trends analysis.
2009, 27(4): 732-739.
Abstract:
Ordovician of Tazhong Uplift had abundant petroleum resources, and was main exploration Formation in the Tarim Basin. However, the origin of oils was the probleum which bothered the oil explorers all along. By systematic geochemical analysis of Ordovician oils in Tazhong Uplift, the paper discriminated oils into populations and determined their origins. Most of oils belong to light oils, light hydrocarbon shows that oils were generated in oil generating window and oils were not cracked in large amount. According to biomarker, the oil can be discriminated into three populations, one population originated from MiddleUpper Ordovician source rocks, the other population originated from Cambrian source rocks, and the third population had mixed origin. All the oils had higher content of dibenzothiophene and lower content of dibenzofuran in relative composition of Fluorinedibenzofurandibenzothiophene. Carbon isotope of saturate and aromatics in oils were lighter than -31.2‰ and -30.4‰, separately, which were apparently lighter than Cambrian oils from wells of Tadong2 and Tashen1. It shows that oils with heavier carbon isotope came from Cambrian source rocks, but oils with lighter carbon isotope came from Cambrian source rocks or MiddleUpper Ordovician source rocks.
Ordovician of Tazhong Uplift had abundant petroleum resources, and was main exploration Formation in the Tarim Basin. However, the origin of oils was the probleum which bothered the oil explorers all along. By systematic geochemical analysis of Ordovician oils in Tazhong Uplift, the paper discriminated oils into populations and determined their origins. Most of oils belong to light oils, light hydrocarbon shows that oils were generated in oil generating window and oils were not cracked in large amount. According to biomarker, the oil can be discriminated into three populations, one population originated from MiddleUpper Ordovician source rocks, the other population originated from Cambrian source rocks, and the third population had mixed origin. All the oils had higher content of dibenzothiophene and lower content of dibenzofuran in relative composition of Fluorinedibenzofurandibenzothiophene. Carbon isotope of saturate and aromatics in oils were lighter than -31.2‰ and -30.4‰, separately, which were apparently lighter than Cambrian oils from wells of Tadong2 and Tashen1. It shows that oils with heavier carbon isotope came from Cambrian source rocks, but oils with lighter carbon isotope came from Cambrian source rocks or MiddleUpper Ordovician source rocks.
2009, 27(4): 752-759.
Abstract:
The study on the oil reservoir formation and its conditions matching in space revealed that the oil in F,Y oil layers in south Songzhan region, Songliao basin was derived from K1qn1 source rock in Sanzhao depression and two mechanisms of oil migration and accumulation in F,Y oil layers existed. Within the sourcerock area, oil from the K1qn1 source rock migrated downward into F,Y layers through the passageway of the T2 faults connecting sourcerock and reservoir and the driving force of overpressured K1qn1 source rock, and then the oil in F,Y layers migrated short distance along the faults and accumulated in the high fault blocks with the buoyancy force. Outside the sourcerock area, the oil in F,Y layers, Sanzhao depression migrated laterally to south Songzhan along the sandbody connected by faults with the buoyancy force and then accumulated in the upper walls of the faults. Different model of the reservoir formation has different controlling factors. Within the sourcerock area, there are 3 factors, one is that the area of oil from the K1qn1 source rock migrated downward controlled the oil pool formation and its distribution; the second is that the T2 faults connecting the sourcerock and reservoir controlled the place of oil accumulation and the third is that the upper walls of the faults are the main area of oil accumulation. Outside the sourcerock area, there are 2 factors, one is that the traps located in and near the pathways of oil migration can form reservoirs in them; the second is that the upper walls of the faults are favor of oil reservoir formation. From the above comprehensive study, the areas near the T2 faults connecting source and reservoir within the sourcerock area and the upper side of the fault near the path of oil migration outside the sourcerock area should be the favorable objects oil exploration.
The study on the oil reservoir formation and its conditions matching in space revealed that the oil in F,Y oil layers in south Songzhan region, Songliao basin was derived from K1qn1 source rock in Sanzhao depression and two mechanisms of oil migration and accumulation in F,Y oil layers existed. Within the sourcerock area, oil from the K1qn1 source rock migrated downward into F,Y layers through the passageway of the T2 faults connecting sourcerock and reservoir and the driving force of overpressured K1qn1 source rock, and then the oil in F,Y layers migrated short distance along the faults and accumulated in the high fault blocks with the buoyancy force. Outside the sourcerock area, the oil in F,Y layers, Sanzhao depression migrated laterally to south Songzhan along the sandbody connected by faults with the buoyancy force and then accumulated in the upper walls of the faults. Different model of the reservoir formation has different controlling factors. Within the sourcerock area, there are 3 factors, one is that the area of oil from the K1qn1 source rock migrated downward controlled the oil pool formation and its distribution; the second is that the T2 faults connecting the sourcerock and reservoir controlled the place of oil accumulation and the third is that the upper walls of the faults are the main area of oil accumulation. Outside the sourcerock area, there are 2 factors, one is that the traps located in and near the pathways of oil migration can form reservoirs in them; the second is that the upper walls of the faults are favor of oil reservoir formation. From the above comprehensive study, the areas near the T2 faults connecting source and reservoir within the sourcerock area and the upper side of the fault near the path of oil migration outside the sourcerock area should be the favorable objects oil exploration.
2009, 27(4): 769-776.
Abstract:
In order to make sure the hydrocarbon source and migration path of N22 in the Nanyishan oilfield, we use the technique of reservoir geochemistry and the correlation principle of statistics to filter and analyze the migration indexes, by combing several kinds of indexes we make a conclusion that there are two oil and gas inject directions (northwest and northnorthwest) in the research area, indicating that the oil and gas are from Xiaoliangshan depression, which is consistent with the result of the oil sources comparative study. And the research find that nitrogen compounds, which serve as the tracers for oil and gas migration, have feasibility and advantage to some extent.
In order to make sure the hydrocarbon source and migration path of N22 in the Nanyishan oilfield, we use the technique of reservoir geochemistry and the correlation principle of statistics to filter and analyze the migration indexes, by combing several kinds of indexes we make a conclusion that there are two oil and gas inject directions (northwest and northnorthwest) in the research area, indicating that the oil and gas are from Xiaoliangshan depression, which is consistent with the result of the oil sources comparative study. And the research find that nitrogen compounds, which serve as the tracers for oil and gas migration, have feasibility and advantage to some extent.
