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Formation conditions and exploration direction of large-scale lithologic reservoirs of Cenozoic in Bohai Sea
NIU Chengmin, DU Xiaofeng, WANG Qiming, ZHANG Can, DING Yiran
2022, Vol.34(3): 1–14
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395 )
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274
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Genesis and distribution prediction of sweet spots of Permian Lucaogou Formation in Jimsar Sag
LIU Zhongquan, ZENG Zhiping, TIAN Jijun, LI Yanli, LI Wan'an, ZHANG Wenwen, ZHANG Zhiheng
2022, Vol.34(3): 15–28
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320 )
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275
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Main controlling factors and prediction of fractures in deep metamorphic buried hill reservoirs in Bohai Sea
ZHENG Hua, KANG Kai, LIU Weilin, GONG Min, CHEN Shanbin
2022, Vol.34(3): 29–38
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308 )
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(5528 KB)
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244
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Diagenesis and pore evolution of dolomite reservoirs of Cambrian Xixiangchi Formation in central Sichuan Basin
LI Luping, LIANG Jintong, LIU Sibing, GUO Yanbo, LI Kunyu, HE Yuan, JIN Jiuxiang
2022, Vol.34(3): 39–48
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320 )
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(12723 KB)
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205
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Characteristics of pore-fracture filling and fluid source of Cretaceous Bashijiqike Formation in Keshen well block，Kuqa Depression
WANG Linbo, HAN Denglin, WANG Chenchen, YUAN Rui, LIN Wei, ZHANG Juan
2022, Vol.34(3): 49–59
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266 )
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(8282 KB)
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165
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Genesis and logging response characteristics of formation overpressure of Paleogene in Bozhong Sag，Bohai Bay Basin
HE Yu, ZHOU Xing, LI Shaoxuan, DING Hongbo
2022, Vol.34(3): 60–69
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367 )
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(4660 KB)
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264
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Shale oil reservoir characteristics and significance of the first member of Paleogene Shahejie Formation in Nanpu Sag，Huanghua Depression
CHENG Danhua, JIAO Xiarong, WANG Jianwei, ZHUANG Dongzhi, WANG Zhengjun, JIANG Shan
2022, Vol.34(3): 70–81
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304 )
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(12136 KB)
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187
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Hydrocarbon accumulation conditions and main controlling factors of Paleogene in Chenghai slope，Huanghua Depression
GUO Meijie, SHI Baohong, DONG Xiongying, LI Haodong, HE Chuan
2022, Vol.34(3): 82–92
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249 )
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(7530 KB)
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214
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Sedimentary characteristics of braided-meandering transitional river of Neogene Guantao Formation in northeastern Liaodong Bay Depression
LI Xiaohui, DU Xiaofeng, GUAN Dayong, WANG Zhiping, WANG Qiming
2022, Vol.34(3): 93–103
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249 )
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(9843 KB)
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207
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Discrete fracture characterization and modeling of Paleogene in Dina-2 gas field， Tarim Basin
CHEN Yuan, LIAO Faming, LYU Bo, JIA Wei, SONG Qiuqiang, WU Yan, KANG Ju, XIAN Rangzhi
2022, Vol.34(3): 104–116
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284 )
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Sedimentary microfacies division and logging identification of Ordovician Wufeng-Silurian Longmaxi shale in Luzhou area，Sichuan Basin
QIU Chen, YAN Jianping, ZHONG Guanghai, LI Zhipeng, FAN Cunhui, ZHANG Yue, HU Qinhong, HUANG Yi
2022, Vol.34(3): 117–130
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394 )
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(9596 KB)
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277
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A/S control on spatiotemporal evolution of deltas in rifted lacustrine basin and its numerical simulation： A case study of Paleogene Wenchang Formation in Lufeng 22 subsag，Pearl River Mouth Basin
ZHANG Wei, LI Lei, QIU Xinwei, GONG Guangchuan, CHENG Linyan, GAO Yifan, YANG Zhipeng, YANG Lei
2022, Vol.34(3): 131–141
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270 )
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195
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Pore structure and classification evaluation of shale oil reservoirs of Permian Fengcheng Formation in Mahu Sag
LEI Haiyan, GUO Pei, MENG Ying, QI Jing, LIU Jin, ZHANG Juan, LIU Miao, ZHENG Yu
2022, Vol.34(3): 142–153
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298 )
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Sedimentary characteristics and petroleum geological significance of the third member of Triassic Feixianguan Formation in northeastern Sichuan Basin
ZHANG Benjian, XU Chang, XU Liang, ZHOU Gang, DING Xiong
2022, Vol.34(3): 154–163
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Pressure transient of polymer flooding considering induced fractures based on PEBI grid
ZHONG Huiying, SHEN Wenxia, ZANG Qiuyuan, XU Yanrui
2022, Vol.34(3): 164–170
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Formation conditions and exploration direction of large-scale lithologic reservoirs of Cenozoic in Bohai Sea
NIU Chengmin, DU Xiaofeng, WANG Qiming, ZHANG Can, DING Yiran
2022, Vol.34(3): 1–14
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395 )
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doi: https://doi.org/10.12108/yxyqc.20220301
Based on the systematic analysis of structural evolution， sedimentary filling evolution characteristics under sequence framework and the characteristics of the main source rocks in Cenozoic basin in Bohai Sea， the formation conditions and development characteristics of large-scale lithologic reservoirs in Bohai Sea were analyzed， and the favorable exploration fields and next research directions were clarified. The results show that： （1）Paleogene Shahejie Formation，Dongying Formation and the lower member of Neogene Minghuazhen Formation are the key strata for forming large lithologic reservoirs in Bohai Sea. The lower member of Minghuazhen Formation was in the lacustrine shrinking period，forming three types of large-scale lithologic reservoirs，such as river channel， very shallow delta and river-lake interaction system. Dongying Formation was in the depression period，and two types of large-scale sublacustrine fan lithologic reservoirs，slump turbidite fans and slope-sliding fans，were formed due to the supply of water system outside the basin. Shahejie Formation was in the fault depression period， affected by local provenance in the basin，it formed three types of large-scale lithologic reservoirs，including near-source fan delta lateral pinch out type，strike slope stratigraphic overlap type and updip pinch-out type. Among them，the river-lake interaction system of the lower member of Minghuazhen Formation and the nearsource fan bodies of Shahejie Formation are the most favorable areas.（2）The lower member of Minghuazhen Formation in western Huanghekou Sag and slope area surrounding Bozhong Sag has great exploration potential， which is the most realistic exploration field for increasing reserves in Bohai Sea. The near-source fan bodies of Shahejie Formation in the steep slope zones of western Shijiutuo uplift，Bonan low uplift and Chengbei low uplift are the key breakthrough directions for next exploration. The sublacustrine fans of Dongying Formation have good exploration prospect in the surrounding areas of Bozhong Sag，and the central and northern Liaozhong Sag. The large-scale progradational delta of the third member of Shahejie Formation in northern Laizhouwan Sag and the beach bar of the first and second members of Shahejie Formation in the surrounding areas of Bozhong Sag are potential favorable exploration fields.
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Genesis and distribution prediction of sweet spots of Permian Lucaogou Formation in Jimsar Sag
LIU Zhongquan, ZENG Zhiping, TIAN Jijun, LI Yanli, LI Wan'an, ZHANG Wenwen, ZHANG Zhiheng
2022, Vol.34(3): 15–28
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320 )
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doi: https://doi.org/10.12108/yxyqc.20220302
Based on the data of rock types，mineral components，physical properties，sedimentary environment and diagenesis，the genesis and distribution of shale oil sweet spots of Permian Lucaogou Formation in Jimsar Sag were studied. The results show that： （1）The upper sweet spots in the study area are mainly composed of sandy dolomite，argillaceous dolomite and dolomitic siltstone，and the lower sweet spots are mainly composed of argillaceous dolomite，dolomitic siltstone，siltstone and dolomitic mudstone. The upper sweet spots have an average poro-sity of 9.4% and an average permeability of 0.063 7 mD， while the lower sweet spots have an average porosity of 9.3% and an average permeability of 0.023 1 mD，all of them belong to medium-low porosity and ultra-low permeability reservoirs. （2）The pores in the sweet spot reservoirs are mainly intragranular dissolved pores and intergranular dissolved pores. The difference between the upper and lower sweet spots is influenced by depositional environment and diagenesis. The physical properties of inshore shoals and far-shore shoals are better，followed by far-shore dam and dolomitic flat. Compaction and cementation are the two major factors to reduce the reservoir capacity，and dissolution can improve their physical properties.（3）The upper sweet spots have the characteristics of high natural gamma and high resistivity，with peak-shaped logging curve，while the lower sweet spots have the characteristics of medium natural gamma and high resistivity. NMR porosity greater than 5.5% can be used as a sensitive parameter to identify sweet spots. The sweet spots on the seismic inversion section have the characteristics of medium and high impedance.（4）Compared with the upper sweet spots，the lower sweet spots are more widely distributed in the sag and has better reservoir physical properties.
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Main controlling factors and prediction of fractures in deep metamorphic buried hill reservoirs in Bohai Sea
ZHENG Hua, KANG Kai, LIU Weilin, GONG Min, CHEN Shanbin
2022, Vol.34(3): 29–38
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doi: https://doi.org/10.12108/yxyqc.20220303
Bozhong 13-2 area is the first deep metamorphic buried hill reservoir with 100 million-ton reserves discovered in Bohai Sea. Based on the data of drilled cores，thin sections, test and logging, the buried hill reservoir space，main controlling factors and distribution of fractures in the study area were expounded from the aspects of structural evolution，diagenesis and paleogeomorphic characteristics，which lays a foundation for the efficient development of the study area. The results show that： （1）Multi-stage tectonic movements are the main controlling factors of fracture formation，weathering， leaching and fracture filling are the main reasons for the vertical difference of reservoirs.（2）The coupling properties of structure tensor field and diffraction wave can effectively guide the prediction of reservoir on the plane in the study area， and the maximum likelihood attributes can be used to effectively predict the fracture trend in buried hills.（3）The fractures are well developed near the large faults on the plane， and the fractures developed in the weathered zone are better than those in the inner zone in the vertical direction. The reservoirs in the weathered zone of Bozhong 13-2 area can be divided into four types. The type Ⅰ reservoirs are the best and mainly located in the high parts of the structure，type Ⅱ reservoirs are mainly located at the waist of the structure，type Ⅲ reservoirs are mainly located in the structural wings near the faults, and type Ⅳreservoirs are the poorest and mainly located far away from the large faults.
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Diagenesis and pore evolution of dolomite reservoirs of Cambrian Xixiangchi Formation in central Sichuan Basin
LI Luping, LIANG Jintong, LIU Sibing, GUO Yanbo, LI Kunyu, HE Yuan, JIN Jiuxiang
2022, Vol.34(3): 39–48
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doi: https://doi.org/10.12108/yxyqc.20220304
The Cambrian Xixiangchi Formation in central Sichuan Basin is an important succeeding layer for oil and gas exploration in the basin. Based on the observation of typical drilling cores and thin sections in central Sichuan Basin and its adjacent areas，combined with physical property analysis，the dolomite reservoir characteristics and diagenetic evolution of Xixiangchi Formation in central Sichuan Basin were studied，and the relationship between reservoir pore evolution model and diagenesis was discussed. The results show that： （1）The favorable reservoir lithologies of Xixiangchi Formation in central Sichuan Basin are mainly（residual）granular dolomite， followed by coarse powder-fine crystal dolomite. The reservoir space mainly consists of dissolved pores，including intergranular dissolved pores and intercrystalline dissolved pores and vugs，and the reservoir is mainly fracturepore type.（2）The carbonate rocks of Xixiangchi Formation experienced seawater，atmospheric fresh water and burial diagenesis，including four diagenetic stages：syngenetic-penecontemporaneous stage，early diagenetic stage，epidiagenetic stage and late diagenetic stage.（3）Diagenesis controls the reservoir pore evolution of Xixiangchi Formation，dolomitization and dissolution are the main constructive diagenesis，especially supergenetic dissolution（karstification）and burial dissolution are of great significance to pore development，while multi-stage cementation and filling are the main destructive diagenesis.
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Characteristics of pore-fracture filling and fluid source of Cretaceous Bashijiqike Formation in Keshen well block，Kuqa Depression
WANG Linbo, HAN Denglin, WANG Chenchen, YUAN Rui, LIN Wei, ZHANG Juan
2022, Vol.34(3): 49–59
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doi: https://doi.org/10.12108/yxyqc.20220305
The Cretaceous Bashijiqike Formation in Kuqa Depression of Tarim Basin is a typical ultra-deep fracture-pore sandstone reservoir. The properties，stages and sources of pore-fracture carbonate fluid in Cretaceous Bashijiqike Formation in Keshen well block of Kuqa Depression were comparatively analyzed by means of observation of thin sections and cathode-luminescence analysis of carbonate veins and carbonate cements in pores. The results show that：（1）There were two-stage calcite cements and two-stage dolomite cements in the pores of Cretaceous Bashijiqike Formation in Keshen well block，Kuqa Depression. The fractures were filled with two-stage calcite veins and one-stage dolomite veins.（2）The phase Ⅱ calcite cements existed in the pores and the phase Ⅰ calcite veins filled in the fractures of Cretaceous Bashijiqike Formation in the study area are orange-yellow in cathodoluminescence，and they have similar REE distribution patterns（LREE enrichment, HREE loss， weak negative δCe anomaly，positive δEu anomaly），indicating that there are simultaneous homologous fluids in the pores and fractures. The fluid cementation at that stage tends to occur in fractures，which plays a constructive role in the preservation of pores around the fractures.
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Genesis and logging response characteristics of formation overpressure of Paleogene in Bozhong Sag，Bohai Bay Basin
HE Yu, ZHOU Xing, LI Shaoxuan, DING Hongbo
2022, Vol.34(3): 60–69
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doi: https://doi.org/10.12108/yxyqc.20220306
Based on pressure measurement and logging data of Paleogene in Bozhong Sag，Bohai Bay Basin， the formation pressure curves of the whole well section were established，and the vertical overpressure zones were divided. The genesis and types of overpressure were analyzed by the consideration of vertical effective stress-velocity cross plot，source rock development and vitrinite reflectance，and the method for identifying overpressure was improved. The results show that： （1）Abnormal overpressure developed in the lower second member of Dongying Formation and the third member of Shahejie Formation of Paleogene in Bozhong Sag. The genesis of overpressure is mainly undercompaction，hydrocarbon generation of organic matter and fluid conduction， with the aging of the strata，the overpressure genesis changes from undercompaction to non-undercompaction such as hydrocarbon generation of organic matter and fluid conduction.（2）The overpressure caused by undercompaction generally corresponds to thick mudstone section，with little change of acoustic velocity，low rock density and stable vertical effective stress. The overpressure caused by hydrocarbon generation of organic matter corresponds to the strata with acoustic velocity being lower than that of normal compacted strata，but it increases slightly with the increase of depth，and the vertical effective stress is low. The overpressure caused by fluid conduction generally occurs in overpressure fluid compartments without the conditions for self-source overpressure generation，the acoustic velocity and rock density show normal compaction trend，and the measured pressure increases linearly with depth in the longitudinal direction， showing the same pressure system.
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Shale oil reservoir characteristics and significance of the first member of Paleogene Shahejie Formation in Nanpu Sag，Huanghua Depression
CHENG Danhua, JIAO Xiarong, WANG Jianwei, ZHUANG Dongzhi, WANG Zhengjun, JIANG Shan
2022, Vol.34(3): 70–81
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doi: https://doi.org/10.12108/yxyqc.20220307
The shale oil reservoir of the first member of Paleogene Shahejie Formation（Es1）is the focus of future exploration in the Nanpu Sag of Huanghua Depression. The petrological characteristics，reservoir space types and pore structure characteristics of shale reservoir of Es1 in Nanpu Sag were studied by means of core and thin section observation，scanning electron microscope，nuclear magnetic resonance and X-ray diffraction. The results show that： （1）Four lithofacies are developed in the shale of this area，including gray and dark alternating horizontal laminar felsic shale，dark gray massive mixed shale，gray graded laminated mixed shale，black gray horizontal laminar mixed shale. Shale oil is mainly stored in dark gray massive mixed shale，gray graded laminated mixed shale，black gray horizontal laminar mixed shale.（2）The black gray horizontal laminar mixed shale has the most developed fractures and the largest porosity，and the gray graded laminated mixed shale has higher porosity and less fractures than the dark gray massive mixed shale. The reservoir space includes fractures，residual intergranular pores，mineral intercrystalline pores and dissolved pores. The pore throat is characterized by large pores and tiny throats，the pore radius ranges from 125.369 μm to 156.048 μm with an average of 133.209 μm，and the throat radius ranges from 0.377 μm to 0.860 μm，with an average of 0.622 μm.（3）The mixed shale of Es1 in Nanpu Sag has a large thickness，good oil-bearing properties，developed fractures and good reservoir performance. It has good shale oil formation conditions and great shale oil exploration potential.
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Hydrocarbon accumulation conditions and main controlling factors of Paleogene in Chenghai slope，Huanghua Depression
GUO Meijie, SHI Baohong, DONG Xiongying, LI Haodong, HE Chuan
2022, Vol.34(3): 82–92
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doi: https://doi.org/10.12108/yxyqc.20220308
Based on the data of crude oil characteristics，thin section identification，scanning electron microscope and reservoir physical properties，the hydrocarbon accumulation law and main controlling factors of Paleogene in Chenghai slope of Huanghua Depression were studied. The results show that： （1）Two sets of main source rocks are developed in the first and third members of Paleogene in Chenghai slope，the organic matters are mainly typeⅡ1 and type Ⅱ2，with sufficient oil sources. The reservoir pores are mainly intergranular dissolved pores， intragranular dissolved pores and moldic pores. Three high-quality pore zones are developed vertically. Differential pressure hydrocarbon expulsion provides power for oil and gas migration，and different combinations of faults and reservoirs form a variety of fault lithologic traps.（2）The main controlling factors of hydrocarbon accumulation in the high part of the slope are sand bodies and unconformity surface as oil and gas migration channel， and the main controlling factor of hydrocarbon accumulation in the middle part of the slope is fault. The low part of the slope is close to the oil source and has sufficient hydrocarbon supply，so the reservoir has become the key factor for its accumulation.（3）The low part of the slope is the main controlling factor for hydrocarbon enrichment. The reservoir conditions in the high part of the slope are the best，but the hydrocarbon supply is insufficient. There are many faults in the middle part of the slope，and the fault activity can provide good migration and preservation conditions for hydrocarbon accumulation. The low part of the slope has sufficient hydrocarbon supply， but the reservoir conditions are poor，so the middle part of the slope is the block with the most abundant oil and gas resources.
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Sedimentary characteristics of braided-meandering transitional river of Neogene Guantao Formation in northeastern Liaodong Bay Depression
LI Xiaohui, DU Xiaofeng, GUAN Dayong, WANG Zhiping, WANG Qiming
2022, Vol.34(3): 93–103
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doi: https://doi.org/10.12108/yxyqc.20220309
Braided-meandering transitional river is a type of river developed in the process of braided river transforming to meandering river. Based on modern sedimentary analogy，tectonic evolution analysis，core analysis and seismic forward modeling analysis，the sedimentary system types and sedimentary evolution law of Neogene Guantao Formation in northeastern Liaodong Bay Depression of Bohai Bay Basin were studied. Under the control of sequence strata，the macro and micro sedimentary characteristics and reservoir accumulation conditions of three sedimentary systems of Guantao Formation，including braided river，meandering river and braided-meandering transitional river，were compared. The results show that： （1）During the sedimentary period of Guantao Formation in northeastern Liaodong Bay Depression，the sedimentary system gradually transited from braided river to meandering river，and braided-meandering transitional river developed in the middle Guantao Formation.（2）The braided-meandering transitional river are characterized by strong hydrodynamic force，combined vertical accretion and lateral accretion，moderate reservoir development and maturity，low-frequency interbedded sandstone and mudstone，and superposition of box-shaped and bell-shaped logging curves.（3）Compared with the reservoirs of braided river and meandering river，the braided-meandering transitional river reservoirs have better lateral connectivity，large-scale mudstone interlayers developed at vertical intervals，and better reservoir-cap assemblage conditions，which determines that they are more conducive to large-scale hydrocarbon accumulation.
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Discrete fracture characterization and modeling of Paleogene in Dina-2 gas field， Tarim Basin
CHEN Yuan, LIAO Faming, LYU Bo, JIA Wei, SONG Qiuqiang, WU Yan, KANG Ju, XIAN Rangzhi
2022, Vol.34(3): 104–116
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doi: https://doi.org/10.12108/yxyqc.20220310
Based on the data of core analysis，imaging logging， geophysics，reservoir geology and reservoir performance，the basic parameters of fractures of Paleogene in Dina-2 gas field of Tarim Basin were described. The joint technologies such as structural smoothing，three-dimensional boundary detecting and boundary strengthening were used to identify the multi-scale fracture distribution，and then a three-dimensional geological model of fracture distribution was established by using multi-scale fracture modeling technology. The results show that： （1）The Paleogene fractures in Dina area are mainly high angle oblique fractures and vertical fractures in near EW direction. The true opening of macro fractures is generally less than 0.460 mm，the average linear density is 0.730 pieces per meter，the filling degree is high. The true opening of micro fractures is less than 0.037 mm， the average surface density is 0.031 pieces per square meter，and the filling degree is low. Most of the fractures are shear fractures related to structural deformation and faulting.（2）The three-dimensional minimum curvature seismic attribute is sensitive to faults and fractures. The ant-tracking attribute volumes identified by boundary detecting and three-dimensional boundary strengthening technology has significantly improved the recognition degree of faults and fractures. The sedimentary reservoir and production performance characteristics can be used to predict the distribution of small-scale fractures between wells.（3）The sequential Gaussian random simulation under facies-controlled conditions was adopted for reservoir simulation. The porosity and permeability before and after simulation are basically consistent. The error between the calculated geological reserves and real reserves is small. On the whole，the geological model can objectively reflect the underground geological characteristics of gas reservoir.（4）The weights were analyzed with different attribute volumes of the four groups of fractures in the study area. The attribute volumes were fused with different weight coefficients to establish the fracture density attribute field. By optimizing the fracture modeling method，the corresponding model parameters were set for different fracture groups to complete the three-dimensional geological model of discrete fractures. Through dynamic verification，the overall error of formation coefficient is less than 5%.
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Sedimentary microfacies division and logging identification of Ordovician Wufeng-Silurian Longmaxi shale in Luzhou area，Sichuan Basin
QIU Chen, YAN Jianping, ZHONG Guanghai, LI Zhipeng, FAN Cunhui, ZHANG Yue, HU Qinhong, HUANG Yi
2022, Vol.34(3): 117–130
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doi: https://doi.org/10.12108/yxyqc.20220311
Based on the data of XRD，physical properties，thin section， geochemistry and well logging，the microfacies subdivision of Ordovician Wufeng-Silurian Longmaxi shale in Luzhou area of southern Sichuan Basin was carried out，and the logging response characteristics and identification methods were defined. The results show that： （1）The microfacies of shale in Luzhou area can be subdivided into five categories and eight sub categories. Among them，the strong reduction rich organic matter and silicon-rich deep-water shelf facies is the best microfacies subdivision type with the characteristics of good physical properties and high contents of gas，TOC and brittle minerals，which is mainly distributed in the lower sublayer of Long-11 submember.（2）Using seven sensitive curves such as KTH，GR，Th， AC，CNL，DTS and Th/U，the microfacies subdivision types divided by the Bayesian discrimination method based on K-means are consistent with coring results with a coincidence rate greater than 90.0%.
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A/S control on spatiotemporal evolution of deltas in rifted lacustrine basin and its numerical simulation： A case study of Paleogene Wenchang Formation in Lufeng 22 subsag，Pearl River Mouth Basin
ZHANG Wei, LI Lei, QIU Xinwei, GONG Guangchuan, CHENG Linyan, GAO Yifan, YANG Zhipeng, YANG Lei
2022, Vol.34(3): 131–141
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doi: https://doi.org/10.12108/yxyqc.20220312
The ratio of accommodation to sediment supply（A/S）of lacustrine basin shows a strong correlation with sequence structure and the stacking pattern of deltas on profile. By using high-resolution 3D seismic data and logging data，based on sequence stratigraphy，sedimentology theory and sedimentary numerical simulation technology，the isochronous stratigraphic framework of Paleogene Wenchang Formation in Lufeng 22 subsag of Pearl River Mouth Basin was established. Combined with sedimentary numerical simulation technology，the control effects of A/S on the spatiotemporal evolution of deltas in rifted lacustrine basin were explored. The results show that： （1）Wenchang Formation in Lufeng 22 subsag can be divided into six third-order sequences，including SQ1，SQ2，SQ3，SQ4 and SQ5+6 from bottom to top. Four types of delta systems are identified in Wenchang Formation in the study area，including chaotic foreset，downlap foreset，oblique foreset and imbricated foreset. （2）There are obvious differences between SQ3 and SQ4 sequence sedimentary systems of Wenchang Formation. During the SQ3 period，the A/S was greater than 1，sediments deposited in the lacustrine basin deltas mostly came from near-source，and large area of semi-deep to deep lacustrine deposits were developed in the subsag. During the SQ4 period，the A/S was less than or equal to 1，the delta advanced into the center of the lacustrine basin， and shore shallow lacustrine deposits were widely developed in the subsag.（3）The SQ3 and SQ4 sequences of Wenchang Formation in the study area were selected to carry out numerical simulation of delta sedimentary system. During the simulation，three main parameters such as accommodation，sediment supply and transportation patterns were set in the software. The simulation results are consistent with the actual geological understanding，and the spatial distribution of sand bodies in the study area was determined.
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Pore structure and classification evaluation of shale oil reservoirs of Permian Fengcheng Formation in Mahu Sag
LEI Haiyan, GUO Pei, MENG Ying, QI Jing, LIU Jin, ZHANG Juan, LIU Miao, ZHENG Yu
2022, Vol.34(3): 142–153
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doi: https://doi.org/10.12108/yxyqc.20220313
The Lower Permian Fengcheng Formation in Mahu Sag is the major source rock in the NW Junggar Basin，with great prospects for shale oil exploration. The pore structure of shale oil reservoirs of Fengcheng Formation in well Maye 1 in the study area was studied and classified by means of field emission electron scanning microscope and high-pressure mercury injection. The results show that： （1）The shale oil reservoir of Fengcheng Formation in Mahu Sag is dominated by thin-layer or massive dolomitic，silty，calcareous or siliceous mudstone， and a large amount of dolomite，calcite and siliceous bands，lumps or patches are often developed in the mudstone. （2）The pore types of shale oil reservoirs of Fengcheng Formation in the study area are mainly intergranular pores， matrix dissolved pores，intragranular dissolved pores，intercrystalline pores，intracrystalline dissolved pores and microfractures，among which matrix dissolved pores and intercrystalline pores are the most developed. The physical properties of the shale oil reservoirs are poor，the porosity values range from 0.4% to 17.7% and are mostly less than 3.0%，and the permeability value are mostly less than 0.03 mD，with the maximum of 2.90 mD，belonging to low porosity and extra-low permeability reservoirs.（3）The pore volume of samples in the study area is generally small，with an average of 0.25 cm3. The average values of average coefficient，sorting coefficient，skewness， peakedness and coefficient of variation is 13.95，2.44，0.97，1.25 and 0.17，respectively. The maximum mercury saturation is low，with an average of37.23%，and the efficiency of mercury-ejection is low，with an average of only 25.73%.（4）The shale oil reservoirs in the study area can be divided into three types： Ⅰ， Ⅱ and Ⅲ. Among them，type Ⅰ shale oil reservoirs with good physical properties and good internal pore connectivity have good prospects for oil and gas exploration and development.
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Sedimentary characteristics and petroleum geological significance of the third member of Triassic Feixianguan Formation in northeastern Sichuan Basin
ZHANG Benjian, XU Chang, XU Liang, ZHOU Gang, DING Xiong
2022, Vol.34(3): 154–163
Abstract
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330 )
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doi: https://doi.org/10.12108/yxyqc.20220314
In recent years， new discoveries have been made in natural gas exploration of the third member of Triassic Feixianguan Formation（T1f3）in northeastern Sichuan Basin. The sedimentary characteristics and petroleum geological significance of T1f3 in northeastern Sichuan Basin were studied through drilling core observation，logging interpretation，facies marker identification and analysis of dominant facies of granular rock. The results show that： （1）The T1f3 in the study area is dominated by open platforms and restricted-evaporate platforms，and four sedimentary subfacies can be identified，including intra-platform shoal，interbank sea，tidal flat and lagoon.（2）The intra-platform shoals are mainly composed of granular rock deposits，which can be further divided into oolitic shoal microfacies and bioclastic shoal microfacies. Oolitic shoals formed in micro-topographic highlands of open platforms or restricted-evaporate platforms，and bioclastic shoals formed in open platforms，both of which had high energy sedimentary water，with upward coarsening reverse grain sequence.（3）The interbank seas and lagoons were mainly developed in the low-lying areas inside the platform，with low depositional environment energy. They can be further divided into calcite interbank seas（calcite lagoons）and dolomitic lagoon microfacies， which belong to semi-restricted to restricted interbank seas（lagoons） . The tidal flats were developed near the mean sea level inside the platform in the late stage of multi-level sea level decline，corresponding to the sedimentary response of sedimentary water shallowing and hydrodynamic weakening，and they can be further divided into gypsum flat microfacies and dolomitic flat microfacies.（4）The thickness of granular rocks is greater than 15 m and the thickness of gypsum rocks is 15-20 m in the northeastern P6-L1-L5 well areas in the study area， and this area can be a key area for exploration of natural gas reservoirs of T1f3.
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Pressure transient of polymer flooding considering induced fractures based on PEBI grid
ZHONG Huiying, SHEN Wenxia, ZANG Qiuyuan, XU Yanrui
2022, Vol.34(3): 164–170
Abstract
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256 )
PDF (2430 KB) (
234
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doi: https://doi.org/10.12108/yxyqc.20220315
Based on PEBI grid method，by considering the situation that the polymer injection well will produce induced fractures during the injection process，and taking into account the rheology of polymer solution，shear thinning，permeability reduction and adsorption mechanism，a mathematical model of polymer flooding considering vertical induced fractures was established. The finite volume method was used to discrete the mathematical model， and then the numerical solution of bottom hole pressure was obtained. The double logarithmic curve of pressure and pressure derivative was plotted and the influencing factors were analyzed. The results show that： （1）The well test curve of polymer flooding for vertically fractured well can be divided into five flow stages：pure wellbore storage stage，bilinear flow stage，linear flow stage，elliptical flow stage and radial flow stage. Polymer concentration mainly affects the later stage of well test curve. The higher the concentration，the more upward the curves at the bilinear flow stage and non-Newtonian radial flow stage.（2）The shorter the half-length of induced fractures，the more obvious the upward curve of pressure and pressure derivative. Compared with the pressure dynamic curves considering induced fracture closure in water drive，the numerical calculation method of polymer flooding considering induced fracture based on hybrid PEBI grid can accurately describe the pressure transient after induced fracture closure.（3）When the value of the fracture closure velocity factor（delpat）is 0，the fracture closes instantaneously and the pressure change suddenly，it is shown as an obvious peak in the pressure derivative diagram. The larger the delpat is，the slower the closure velocity is，the lower the derivative peak is，and the more the curve shifts to the right.