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Reservoir forming conditions and exploration prospect of Middle-Lower Jurassic Shuixigou group in northern piedmont belt of Turpan-Hami Basin
WU Qingpeng, YANG Zhanlong, YAO Jun, YUAN Cheng, ZHANG Jing
2021, Vol.33(6): 1–11
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Characteristics of tight sandstone reservoirs of the second member of Shanxi Formation in eastern Ordos Basin
WANG Yongxiao, FU Siyi, ZHANG Chenggong, FAN Ping
2021, Vol.33(6): 12–20
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Hydrocarbon accumulation phases of Yanchang Formation in Wuqi area, Yishan slope
LI Bo, CUI Junping, LI Ying, LI Jinsen, ZHAO Jin, CHEN Yanwu
2021, Vol.33(6): 21–28
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Diagenesis and pore evolution of Chang 6 tight sandstone reservoir in southeastern Ordos Basin
ZHANG Yuye, GAO Jianwu, ZHAO Jingzhou, ZHANG Heng, WU Heyuan, HAN Zaihua, MAO Zhaorui, YANG Xiao
2021, Vol.33(6): 29–38
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Characteristics and indication of fluid inclusions of Jurassic Zhiluo Formation in south-central Ordos Basin
YANG Shuisheng, WANG Huizhi, YAN Xiaolong, FU Guomin
2021, Vol.33(6): 39–47
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(5234 KB)
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Characteristics of delta front progradation structure of Yanchang Formation in Longdong area,Ordos Basin
FENG Xue, GAO Shengli, LIU Yongtao, WANG Xiuzhen
2021, Vol.33(6): 48–58
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Characteristics and main controlling factors of Chang 8 reservoir in northern Pingliang area,Ordos Basin
SHAO Xiaozhou, WANG Miaomiao, QI Yalin, HE Tongtong, ZHANG Xiaolei, PANG Jinlian, GUO Yixuan
2021, Vol.33(6): 59–69
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Sedimentary facies characteristics and favorable reservoirs distribution of Lower Triassic Feixianguan Formation in Fuling area
REN Jie, HU Zhonggui, HU Mingyi, LI Xiong, PANG Yanrong, ZUO Mingtao, HUANG Yufei
2021, Vol.33(6): 70–80
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Paleoenvironment and development model of source rocks of Dongying Formation in Bozhong Sag
YANG Hong, LIU Chenglin, WANG Feilong, TANG Guomin, LI Guoxiong, ZENG Xiaoxiang, WU Yuping
2021, Vol.33(6): 81–92
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275 )
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(6212 KB)
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453
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Karst model of Paleozoic carbonate buried hill in No. 2 fault zone of Nanpu Sag
TIAN Xiaoping, ZHANG Wen, ZHOU Liande, SHEN Xiaoxiu, GUO Wei
2021, Vol.33(6): 93–101
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224 )
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Depositional system and sequence stratigraphy of the third member of Paleo-gene Shahejie Formation in Leijia area, Western Liaohe Depression
WANG Qiao, SONG Lixin, HAN Yajie, ZHAO Huimin, LIU Ying
2021, Vol.33(6): 102–113
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277 )
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(6888 KB)
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Characteristics of Cretaceous source rocks in northern Guaizihu Sag, Yingen-Ejinaqi Basin
PAN Binfeng, GAO Yuequan, PAN Tao, LI Zongxian, WANG Zhiwei, QIU Wenbo, FENG Rong
2021, Vol.33(6): 114–123
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261 )
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Reservoir characteristics and main controlling factors of Yan 10 sandy braided fluvial facies in Anbian area,Ordos Basin
ZHAO Xiaomeng, GUO Feng, PENG Xiaoxia, ZHANG Cuiping, GUO Ling, SHI Yuxiang
2021, Vol.33(6): 124–134
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256 )
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Multi-stage fluid activity characteristics of Wufeng-Longmaxi Formation in Ningxi area, southern Sichuan Basin
LI Xiaojia, DENG Bin, LIU Shugen, WU Juan, ZHOU Zheng, JIAO Kun
2021, Vol.33(6): 135–144
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Dolomitic reservoir prediction technology based on OVT domain migration data and its application: A case study of Feng 3 member in Wuxia area,Mahu Sag
CHEN Yongbo, ZHANG Huquan, ZHANG Han, ZENG Huahui, WANG Bin, WANG Hongqiu, XU Duonian, MA Yongping, ZONG Zhaoyun
2021, Vol.33(6): 145–155
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Identification of metamorphite lithology in paleo buried hill by compositionstructure classification: A case study from Archean in Bohai Sea
YE Tao, NIU Chengmin, WANG Qingbin, GAO Kunshun, SUN Zhe, CHEN Anqing
2021, Vol.33(6): 156–164
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Prediction of fracture-pore reservoirs in metamorphic clastic rocks using logging reservoir factors: A case study of basement in Beier Sag,Hailar Basin
LI Juan, ZHENG Xi, SUN Songling, ZHANG Bin, CHEN Guangpo, HE Weiwei, HAN Qianfeng
2021, Vol.33(6): 165–176
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Reservoir architecture and fine characterization of remaining oil of Chang 3 reservoir in Zhenbei oilfield,Ordos Basin
ZHANG Haoyu, LI Mao, KANG Yongmei, WU Zemin, WANG Guang
2021, Vol.33(6): 177–188
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Reservoir forming conditions and exploration prospect of Middle-Lower Jurassic Shuixigou group in northern piedmont belt of Turpan-Hami Basin
WU Qingpeng, YANG Zhanlong, YAO Jun, YUAN Cheng, ZHANG Jing
2021, Vol.33(6): 1–11
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doi: https://doi.org/10.12108/yxyqc.20210601
A series of studies, such as source analysis of both the light and heave materials, tectonic modelling and hydrocarbon source rock evaluation, have been carried out to investigate the forming conditions and exploration prospect of Shuixigou group in northern piedmont belt of Turpan-Hami Basin. The research results suggest that: (1) Shuixigou group in north piedmont belt was once dominated by the south source system before the sedimentation of Xishanyao formation. Sand-bodies generated by braid delta are well developed. (2) North piedmont belt of Turpan-Hami basin can be divided into three parts: thrust belt, anticline belt, and slope belt. The thrust belt can also be further divided as a thrust-superimposed body in hanging wall and underlying belt in footwall. Underlying anticlines are developed in the thrust fault zone of footwall, distributed in both rows and belts. Piedmont belt in this area goes through multiple tectonic evolution stages, including three sliding and two thrusting phases. (3) Source rocks in Yierxitu, Taodonggou, and Sangonghe formations show the ability of hydrocarbon generation, indicating a potential in the tectonic traps such as anticlines beneath the underlying belts, faulted anticlines and et al. We finally conclude that the tectonic group of underlying anticlines in the piedmont belt can be a promising target for oil&gas exploration in Turpan-Hami Basin.
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Characteristics of tight sandstone reservoirs of the second member of Shanxi Formation in eastern Ordos Basin
WANG Yongxiao, FU Siyi, ZHANG Chenggong, FAN Ping
2021, Vol.33(6): 12–20
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doi: https://doi.org/10.12108/yxyqc.20210602
The second member of Shanxi Formation in eastern Ordos Basin is a key gas producing zone, with shallow buried depth but poor physical properties. In order to clarify the genesis of low porosity and low permeability and predict the favorable areas of reservoirs, based on the drilling core observations, the experimental methods such as identification under thin slice microscope, scanning electron microscope, mercury intrusion were used. The results show that the tight sandstone reservoirs of the second member of Shanxi Formation are mainly mediumfine-grained lithic quartz sandstone and quartz sandstone, and the reservoir space is dominated by intergranular pores. The main causes of low porosity and low permeability: (1) There are some plastic particles and debris in the sedimentary strata, which are easy to deform under pressure and reduce physical properties. (2) Multiple cementation produces many types of cements, filling a large number of pores and aggravating the deterioration of physical properties. (3) The acidic sedimentary environment containing coal is not conducive to the preservation of primary pores. (4) The weak dissolution in later stage cannot improve the physical properties of the reservoir. Combined with the analysis of the plane distribution characteristics of diagenetic facies, it is considered that the Wulamiao-Yulin-Qingjiandi and Fugu-Jiaxian-Wubao areas are relatively favorable reservoir areas. The research results can provide reference for the exploration and deployment of tight sandstone gas in eastern Ordos Basin.
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Hydrocarbon accumulation phases of Yanchang Formation in Wuqi area, Yishan slope
LI Bo, CUI Junping, LI Ying, LI Jinsen, ZHAO Jin, CHEN Yanwu
2021, Vol.33(6): 21–28
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doi: https://doi.org/10.12108/yxyqc.20210603
Yishan slope is an important oil and gas producing area in Ordos Basin. The study of hydrocarbon accumulation phases is helpful to judge the accumulation process and distribution of Triassic reservoirs. To clarify the hydrocarbon accumulation phases of Chang 4+5 and Chang 6 reservoirs of Triassic Yanchang Formation, a systematic analysis of reservoir fluid inclusion characteristics was carried out based on homogenization temperature and authigenic mineral(illite) K-Ar isotopic dating of the inclusions-burial history indirect projection dating method. The results show that: (1) The Chang 4+5 and Chang 6 reservoirs of Triassic Yanchang Formation in Wuqi area of Yishan slope are mainly composed of brine inclusions and liquid hydrocarbon inclusions, and the shape is mainly ellipsoid-spheroid. (2) Homogenization temperature analysis shows that the reservoir inclusions can be divided into two phases: the main homogenization temperature peaks of the brine inclusions in the first and second phases are 90-110 ℃ and 120-140 ℃ respectively. (3) Based on the analyses of salinity and composition of the inclusions, thermal evolution history of the basin and K-Ar isotopic dating of reservoir illite, there are two stages of hydrocarbon charging in Chang 4+5 and Chang 6 reservoirs: the first stage is the middle Early Cretaceous(130-115 Ma); the second stage is the late Early Cretaceous(108-96 Ma). The two stages of hydrocarbon charging indicate that the hydrocarbon accumulation phase of Yanchang Formation in Yishan slope is Early Cretaceous(130-96 Ma). This understanding provides a basis for the exploration and development of Triassic oil and gas in Wuqi and its adjacent areas.
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Diagenesis and pore evolution of Chang 6 tight sandstone reservoir in southeastern Ordos Basin
ZHANG Yuye, GAO Jianwu, ZHAO Jingzhou, ZHANG Heng, WU Heyuan, HAN Zaihua, MAO Zhaorui, YANG Xiao
2021, Vol.33(6): 29–38
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doi: https://doi.org/10.12108/yxyqc.20210604
There are abundant tight oil reserves in Chang 6 reservoir of Yanchang Formation in Foguyuan area of Ordos Basin, but the tight reservoir and strong heterogeneity lead to low degree of oil and gas exploration. Based on core observation and thin section analysis, the petrological characteristics and diagenesis of Chang 6 reservoir in the study area were studied by means of scanning electron microscopy, cathodoluminescence and X-ray diffraction, and quantitative reconstruction of porosity was carried out. The results show that Chang 6 reservoir is mainly composed of grayish white feldspar fine sandstone, and the reservoir space is mainly dissolved secondary pores and residual intergranular pores, which belongs to ultra-low porosity and ultra-low permeability tight sandstone reservoir. Chang 6 reservoir has entered the middle diagenetic stage A, and has undergone diagenesis such as compaction, cementation, dissolution and metasomatism, and different diagenesis has affected the pore development of the reservoir with varying degrees. Compaction destroys a large number of primary intergranular pores, which is the main factor leading to the reservoir densification in the study area. The compaction causes an average reduction in porosity of 22.76% and a porosity reduction rate of 58.40%. The cementation causes the porosity to decrease by an average of 13.57%, with a porosity reduction rate of 34.93%, of which late cementation is the key factor for reservoir compaction. Dissolution and metasomatism produce a large number of secondary pores, thereby improving the physical properties of the reservoir, and the increased porosity is 12.39% on average. The research results can provide reference for the further exploration and development of similar oilfields.
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Characteristics and indication of fluid inclusions of Jurassic Zhiluo Formation in south-central Ordos Basin
YANG Shuisheng, WANG Huizhi, YAN Xiaolong, FU Guomin
2021, Vol.33(6): 39–47
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doi: https://doi.org/10.12108/yxyqc.20210605
In order to clarify the characteristics of fluid inclusions and their indication of Jurassic Zhiluo Formation in south-central Ordos Basin, micro thermometry, micro fluorescence, burial history and thermal history simulation of inclusions were applied to carry out the analysis. The results show that there are mainly two stages of oil and gas inclusions in Zhiluo Formation in the study area. The early stage of oil and gas inclusions are mainly distributed in dissolved pores on the surface of quartz particles and the early fractures of quartz, with low maturity and orange-yellow-green fluorescence. The homogenization temperature of brine inclusions in the same period ranges from 250 ℃ to 320 ℃. The late stage of oil and gas inclusions are mainly distributed in the late quartz fractures, with high maturity and dark green fluorescence. The homogenization temperature of brine inclusions in the same period is 120-180 ℃. Combined with the study of burial history and thermal history, the homogenization temperature of inclusions is higher than the formation temperature, the distribution range is large, and the temperature discontinuity is obvious in the two stages. It is speculated that the oil and gas migration and accumulation in Zhiluo Formation are affected by tectonic thermal events, which is a relatively long and discontinuous process. The research results are of great significance to the study of reservoir forming mechanism of Zhiluo Formation and are important to the further breakthroughs of oil and gas exploration in the study area.
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Characteristics of delta front progradation structure of Yanchang Formation in Longdong area,Ordos Basin
FENG Xue, GAO Shengli, LIU Yongtao, WANG Xiuzhen
2021, Vol.33(6): 48–58
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doi: https://doi.org/10.12108/yxyqc.20210606
In order to overcome the multiplicity of 2D seismic data in complex structures and the uncertainty of sand body prediction, based on the division of sedimentary facies zones, the 2D and 3D seismic data were interpreted in detail by using the method of migration trajectory and progradational configuration, and the sand body distribution of Yanchang Formation in Longdong area was predicted. The results show that there are four types of progradational configuration of Yanchang Formation in the study area. (1) S-type lenticular progradation has a flat or slightly upward migration path, with top deposit, delta front subfacies and mudstone at the bottom of the lake. (2) S-type wedge-shaped progradation has a flat to descending migration path, with thick basement, and delta sandstone and turbidite are developed. (3) Tangential oblique plate-shaped progradation has a descending migration path, with top and bottom layers, and delta front and turbidite fan are developed. (4) Parallel oblique wedge-shaped progradation has a flat migration path, without top and bottom beds, and delta sandstone and sandy clastic rocks are developed. S-type wedge-shaped progradation and tangential oblique plate-shaped progradation are delta turbidite fan systems, which are favorable directions for lithologic reservoir exploration.
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Characteristics and main controlling factors of Chang 8 reservoir in northern Pingliang area,Ordos Basin
SHAO Xiaozhou, WANG Miaomiao, QI Yalin, HE Tongtong, ZHANG Xiaolei, PANG Jinlian, GUO Yixuan
2021, Vol.33(6): 59–69
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doi: https://doi.org/10.12108/yxyqc.20210607
The Chang 8 reservoir of Yanchang Formation is an important stratum for increasing reserves and production in northern Pingliang area, Ordos Basin, and the oil-water relationship is complex, meanwhile the controlling factors of reservoir accumulation are diverse. Based on the data of crude oil characteristics, formation water properties, reservoir thin section, mercury injection experiment and seismic interpretation, combined with the testing technologies of source rock geochemistry, fluid inclusion and nano CT, the characteristics and controlling factors of Chang 8 reservoir in the study area were studied. The results show Chang 8 crude oil has high density and viscosity, poor overall fluidity and good maturity, and the formation water is mainly type CaCl2, with an average salinity of 37.45 g/L and good preservation conditions. The average TOC content of Chang 7 shale is 4.89%, average chloroform asphalt “A” is 0.51%, and average w (S1+S2) is 17.11 mg/g, with good hydrocarbon generation capacity. Chang 8 reservoir is mainly composed of intergranular pores and feldspar dissolved pores, with good physical properties and strong heterogeneity. Under the influence of regional multi-stage tectonic movement, a structural pattern of alternating concave and uplifts was formed, with saddle-shaped structure and low amplitude nose uplift structure. The Chang 8 reservoir in northern Pingliang area belongs to “near source accu-mulation”. The oil and gas generated by Chang 7 source rocks migrated to Chang 8 favorable traps through sandbodies, fractures and faults, forming lithologic, structural-lithologic and lithologic-structural reservoirs of different scales. The quality of source rocks, reservoir physical properties and low amplitude traps are the main factors controlling the distribution of Chang 8 reservoir in the study area.
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Sedimentary facies characteristics and favorable reservoirs distribution of Lower Triassic Feixianguan Formation in Fuling area
REN Jie, HU Zhonggui, HU Mingyi, LI Xiong, PANG Yanrong, ZUO Mingtao, HUANG Yufei
2021, Vol.33(6): 70–80
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doi: https://doi.org/10.12108/yxyqc.20210608
In recent years, major breakthroughs have been made in oil and gas exploration of Feixianguan Formation in Kaijiang-Liangping trough of Sichuan Basin, showing good prospects for oil and gas discovery. In order to study the sedimentary facies characteristics and the distribution of favorable reservoirs of Lower Triassic Feixianguan Formation, research work such as core observation, seismic interpretation, and comprehensive analysis of drilling and logging data were carried out. Based on high-frequency sequence division and identification of sedimentary facies markers, the sedimentary facies characteristics of Feixianguan Formation were clarified. The results show that: (1) Gentle slope platforms developed in the early stage of Feixianguan Formation, and fringed platforms developed in the middle to late stage in the study area; the platform margin beach bodies in the upper fourth-order sequence framework of the region have a progradation type migration pattern, the platform margin beach bodies in the northern part of Fuling area mainly developed during the sq3-HST period, forming a twostage combination of beach bodies and distributed stably in the region. (2) Reservoirs of Feixianguan Formation in the study area are mainly developed in northern Fuling area, with platform margin beach facies(oolitic beaches, bioclastic beaches) as the main reservoirs, and the reservoir rocks are sprite oolitic limestone, sandy limestone, residual grain dolomite and crystal grain dolomite. (3) The well areas of Xinglong 1, Xinglong 2, Xinglong 3, Fushi 1, Fushi 2 and Baxiang 1 in northern Fuling area are favorable for reservoir development. The research results can provide a reference for the next exploration of Lower Triassic Feixianguan Formation in Fuling area.
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Paleoenvironment and development model of source rocks of Dongying Formation in Bozhong Sag
YANG Hong, LIU Chenglin, WANG Feilong, TANG Guomin, LI Guoxiong, ZENG Xiaoxiang, WU Yuping
2021, Vol.33(6): 81–92
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doi: https://doi.org/10.12108/yxyqc.20210609
The source rocks of Dongying Formation are relatively thick in Bozhong Sag. It is of great significance to clarify the characteristics and development model of this set of source rocks for promoting three-dimensional conventional and unconventional hydrocarbon exploration in deep and shallow layers of Bozhong Sag. Organicinorganic geochemical experiments, whole rock-clay and sporo-pollen analysis tests were carried out on the source rock samples to evaluate the quality of the source rock of Dongying Formation in Bozhong Sag. Combined the ratios of Sr/Cu, Mn/Fe and Pr/Ph, Gammacerane index, cycloterpane ratio, carbon isotope and low algal pollen content, the paleoenvironment and paleo-productivity during the formation of Dongying Formation were analyzed, and a unique source rock development model of Dongying Formation was established. The results show that: (1) The mudstone of Dongying Formation is mainly composed of quartz and feldspar, with low content of carbonate minerals and high content of clay minerals(with a mass fraction of 30%). (2) The organic matter abundance in the lower part of the third and second members of Dongying Formation is high, reaching the maturehigh maturity stage, and the organic matter is mainly Ⅱ1-Ⅱ2 type. (3) The paleoclimate of Dongying Formation is warm and humid, the water salinity gradually becomes lighter, and the water depth gradually becomes shallower, from the high water depth of E3d3(70.1 m) to the low water depth of E3d1(26.7 m). The terrestrial intrusion and water oxidation conditions gradually increase, and the paleo-productivity successively is E3d3(high) > E3d2(middle) > E3d1(low). (4) High productivity and reductive preservation conditions dominate the enrichment of organic matter in Dongying Formation, while paleoclimate, water depth, salinity and terrigenous input have indirect effects on the enrichment of organic matters.
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Karst model of Paleozoic carbonate buried hill in No. 2 fault zone of Nanpu Sag
TIAN Xiaoping, ZHANG Wen, ZHOU Liande, SHEN Xiaoxiu, GUO Wei
2021, Vol.33(6): 93–101
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doi: https://doi.org/10.12108/yxyqc.20210610
The Paleozoic buried hill in Nanpu Sag is an important target for oil and gas exploration and evaluation in Bohai Sea. In order to study the karst model of Paleozoic carbonate buried hill in No.2 fault zone of Nanpu Sag, based on core observation, thin section identification, logging analysis, structural evolution, karst evolution model, combined with paleogeomorphology characteristics, the differences of karst models in each block were comprehensively analyzed. The results show that: (1) the lithology of karst reservoir is limestone and dolomite, with the characteristics of dual pore medium. The connectivity of matrix pores is poor, and fractures play a key role in the reservoir space. They can communicate and dredge the micropores and dissolved pores developed along the fractures are important reservoir spaces. (2) The buried hill karst reservoir mainly experienced supergene karstification and burial cementation. The supergene karstification was affected by the Indosinian-Early Yanshanian thrust folding, forming the current structural pattern and fault system, controlling the development and distribution of karst reservoir. On the other hand, the burial cementation in the Middle-Late Yanshanian-Himalayan period is mainly manifested as the filling of the fracture cavity reservoir space formed earlier by surface water and formation water, which is the destructive effect in the process of karst reservoir formation. The intensity of karstification is controlled by paleogeomorphology and faults. According to the paleogeomorphic morphology and karstification intensity, karst Highlands, karst slope areas and karst depressions are divided. The differences in the development degree of karst reservoirs between different blocks and within the same block are mainly caused by the distance to the fault, the position of paleogeomorphology and the steep and gentle slope. (3) The intensity of karstification is controlled by paleogeomorphology and faults. According to the morphology of paleogeomorphology and the intensity of karstification, karst highlands, karst slope areas and karst depressions are divided. The differences in the development degree of karst reservoirs among the blocks are mainly caused by the location of paleogeomorphology and the steep and gentle slope. The gentle slope zone of paleogeomorphology near the faults has the strongest karstification, the best preservation conditions and the most developed karst reservoir, which is a favorable target for oil and gas exploration in the study area. The research results can provide reference for oil and gas exploration in carbonate buried hill.
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Depositional system and sequence stratigraphy of the third member of Paleo-gene Shahejie Formation in Leijia area, Western Liaohe Depression
WANG Qiao, SONG Lixin, HAN Yajie, ZHAO Huimin, LIU Ying
2021, Vol.33(6): 102–113
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doi: https://doi.org/10.12108/yxyqc.20210611
The third member of Paleogene Shahejie Formation is one of the main oil-bearing series in Leijia area of Western Sag, Liaohe Depression. In order to clarify the sedimentary characteristics and distribution regularity of the reservoir, based on the theory of sedimentology and sequence stratigraphy, the sedimentary facies types and distribution characteristics under sequence framework were summarized by using core, drilling, logging and seismic data. According to sequence boundary markers, such as lithological mutation, logging changes, seismic reflection and paleontology data, Es3 in Leijia area can be divided into three third-order sequences: SQ1, SQ2 and SQ3, which were composed of lowstand systems tract(LST), transgressive systems tract(TST) and highstand systems tract(HST) respectively. Fan delta facies and lacustrine facies are mainly developed in this area. The fan delta facies includes three subfacies: fan delta plain, fan delta front and pro-fan delta, which can be further divided into several microfacies: braided channel, underwater distributary channel, underwater distributary interchannel and mouth bar. The lacustrine facies includes two subfacies: shore-shallow lacustrine and semideep to deep lacustrine. The sedimentary characteristics of fan delta sand bodies of SQ1 are confined by fault activities, palaeogeomorphology and sedimentary source recharge. The above-generation and below-storage assemblage formed by fan delta front sand bodies of the LST of SQ1 and the mudstone of the TST and HST of SQ1 and SQ2 in the east steep slope is the favorable exploration target for lithologic reservoirs. The research results have guiding significance for further exploration of lithologic reservoirs in Leijia area.
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Characteristics of Cretaceous source rocks in northern Guaizihu Sag, Yingen-Ejinaqi Basin
PAN Binfeng, GAO Yuequan, PAN Tao, LI Zongxian, WANG Zhiwei, QIU Wenbo, FENG Rong
2021, Vol.33(6): 114–123
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doi: https://doi.org/10.12108/yxyqc.20210612
In order to study the characteristics of source rocks and evaluate their hydrocarbon generating potential in northern Guaizihu Sag, geochemical tests of mudstone in the whole section of exploration wells were carried out to explore the differential genesis of source rocks in the northern and central parts, and oil source conditions for hydrocarbon accumulation in the study area were evaluated. The results show that: (1) the potential source rocks in the study area are mainly developed in Cretaceous Suhongtu Formation, the third and second members of Bayingebi Formation. The abundance of organic matter in mudstone is generally low, but there are “sweet spots” in some well sections. The type of organic matter is mainly type Ⅲ, and the source rocks have reached mature to over-mature thermal evolution stage. (2) Compared with the central part of Guaizihu Sag, the conditions of source rocks in the northern part are obviously worse, which may be controlled by the differences in the formation environment and source input caused by the differences in boundary fault activity and sag structure. (3) The lower limit of TOC content of effective source rocks in the study area is greater than 1.35%. The effective source rock area in well area W1-W2 is relatively large, and the area of source rocks with thickness greater than 20 m is about 133 km2. The discovery of gas-bearing layer and reservoir bitumen in well W2 shows that the source rocks in the study area have certain hydrocarbon generation potential and has a history of hydrocarbon accumulation. The research results can provide a basis for the next exploration decision-making in Guaizihu Sag.
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Reservoir characteristics and main controlling factors of Yan 10 sandy braided fluvial facies in Anbian area,Ordos Basin
ZHAO Xiaomeng, GUO Feng, PENG Xiaoxia, ZHANG Cuiping, GUO Ling, SHI Yuxiang
2021, Vol.33(6): 124–134
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doi: https://doi.org/10.12108/yxyqc.20210613
To clarify the characteristics and main controlling factors of sandy braided fluvial reservoir, Yan 10 reservoir in Anbian area of Ordos Basin was comprehensively verified by grain size analysis, cast thin section, scanning electron microscope, mercury injection method and conventional physical property analysis, combined with core and logging data. The results show that sandy braided fluvial facies are developed in Yan 10 reservoir in Anbian area, including channel, central bar and flood plain microfacies. The reservoir lithology is mainly feldspathic quartz sandstone and lithic quartz sandstone, and the reservoir space is mainly composed of residual intergranular pores and feldspar dissolved pores. Three main types of throats can be identified, including meso fine throat, micro fine throat and micro throat. The porosity ranges from 11.23% to 17.95%, and the permeability is generally 5.35-56.57 mD, which belongs to medium-low porosity and low-ultra low permeability fine throat reservoir. Sedimentary microfacies are the material factors that affect the physical properties of Yan 10 reservoir. Compaction and cementation of clay minerals, siliceous and calcareous are destructive diagenesis, among which compaction is the main factor. The dissolution of feldspar particles and some cements and the inhibition of chlorite film on compaction and cementation are constructive diagenesis. The research results are of great significance for the prediction of favorable reservoirs in braided river facies.
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Multi-stage fluid activity characteristics of Wufeng-Longmaxi Formation in Ningxi area, southern Sichuan Basin
LI Xiaojia, DENG Bin, LIU Shugen, WU Juan, ZHOU Zheng, JIAO Kun
2021, Vol.33(6): 135–144
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doi: https://doi.org/10.12108/yxyqc.20210614
Calcite veins are commonly developed in organic-rich shale, and their formation process and mechanism have important indications for hydrocarbon-generating reservoirs and accumulations. In order to clarify the correlation between multi-stage fluid activity characteristics of the target strata and the regional tectonic movement process, oil and gas accumulation, based on the hydrocarbon-bearing system accumulation dynamics, through core-slice observation, carbon and oxygen isotope analysis, fluid inclusion temperature measurement, combined with the sedimentary and structural evolution characteristics of Sichuan Basin and the surrounding areas, multi-phase fluid activity characteristics, recovery burial history and thermal history in Ningxi area were analyzed. The results show the carbon and oxygen isotopes are different in depth, they are controlled by fluid sources, depositional environment, temperature, etc., and they can be divided into two stages of fluids based on isotope characteristics. The first stage of fluid is mainly active in the Long-11 sub-member, which is a liquid hydrocarbon fluid with a depth of 3 870-3 950 m, the range of δ13C in the vein is -6.56‰—-1.58‰, with an average value of -3.45‰, and the range of δ18O is -13.72‰—-11.06‰, with an average value of -13.32‰. The carbon isotope is depleted, and the homogenization temperature of the fluid inclusion in the veins is concentrated at 120-140 ℃, corresponding to the oil-generating stage of the Early Triassic. The second stage of fluid is mainly active in the Long-12 submember, which is a high-temperature methane-rich organic fluid, with a depth of 3 830-38 90 m. The δ13C ranges from- 13.27‰ to -12.16‰, with an average value of -12.72‰, the range of δ18O is -9.06‰—-6.61‰, with an average value of -7.84‰. The carbon isotope is severely depleted, and the homogenization temperature of the fluid inclusions in the veins is concentrated at 160-180 ℃, 200-220 ℃, corresponding to the oil pyrolysis gas generation stage in Late Jurassic. The shale gas reservoir was in a high-overpressure state during the two stages of fluid activity, and the depositional environment affected the preservation conditions. The research results can provide certain theoretical support for the study of shale gas accumulation and preservation conditions in southern Sichuan Bain.
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Dolomitic reservoir prediction technology based on OVT domain migration data and its application: A case study of Feng 3 member in Wuxia area,Mahu Sag
CHEN Yongbo, ZHANG Huquan, ZHANG Han, ZENG Huahui, WANG Bin, WANG Hongqiu, XU Duonian, MA Yongping, ZONG Zhaoyun
2021, Vol.33(6): 145–155
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doi: https://doi.org/10.12108/yxyqc.20210615
The lacustrine dolomitic reservoir “sweet spots” of Feng 3 member of Permian Fengcheng Formation in Wuxia area have the characteristics of single thin layer, rapid lateral change and small impedance differences from surrounding rocks, so it is difficult to predict the “sweet spots” reservoir by using conventional 3D seismic data. Based on the analysis of main controlling factors of oil enrichment in the dolomitic reservoir “sweet spots” in high yield wells, it is found that the “sweet spots” are mostly in places where the reservoirs have large thickness, high brittleness(fractures) and high pressure. Based on the main controlling factors of oil accumulation, trace gather dynamic analysis and stacking method based on offset-azimuth stacking template under geologic target was worked out to get prestack seismic data of different azimuths to predict the thickness of dolomitic reservoir. On the basis of elastic parameter cross-plot analysis template, Young's modulus(E) and Poisson's ratio(σ) were used to predict the brittle part of dolomitic reservoir in the slope area. Based on wave equation, Hooke's law and elastic parameter, the relationships of effective stress with P-wave and S-wave velocity were derived, and a formation pressure prediction method combining Young's modulus(E) and volume modulus(K) was developed to predict the area with abnormal pressure to enhance the prediction accuracy of “sweet spots”. After the application of this result, three wells have obtained high yield oil flows in Feng 3 member, and hundred million tons geologic oil reserves are evaluated.
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Identification of metamorphite lithology in paleo buried hill by compositionstructure classification: A case study from Archean in Bohai Sea
YE Tao, NIU Chengmin, WANG Qingbin, GAO Kunshun, SUN Zhe, CHEN Anqing
2021, Vol.33(6): 156–164
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doi: https://doi.org/10.12108/yxyqc.20210616
The lithology of metamorphic buried hill plays an important role in controlling reservoir development. In order to identify lithology of metamorphic buried hill effectively, the well-logging identification methods based on component-structure classification of metamorphite were studied with the data of boreholes in Bohai Sea. The results show that migmatization and intrusion of intermediate basic magma are the main controlling factors for the complex lithologic association of Archean, which control the formation of femic intrusion and the felsic metamorphite, and the migmatization makes the metamorphic granite more complex. Based on mineral and element analysis and core observation, the division scheme of four components and three structures was established, and the classification scheme of Archean well logging geology in Bohai Sea area was established. Based on this scheme, the identification chart of logging intersection for different lithologies were constructed, and the conventional logging and imaging logging identification methods for rock structure were established. The identification result is consistent with the geological understanding through the back judgment of coring well. This method provides a new thinking for identification of metamorphite.
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Prediction of fracture-pore reservoirs in metamorphic clastic rocks using logging reservoir factors: A case study of basement in Beier Sag,Hailar Basin
LI Juan, ZHENG Xi, SUN Songling, ZHANG Bin, CHEN Guangpo, HE Weiwei, HAN Qianfeng
2021, Vol.33(6): 165–176
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doi: https://doi.org/10.12108/yxyqc.20210617
Taking the basement reservoir of metamorphic clastic rock in Beier Sag, Hailar Basin as an example, considering the characteristics of lithology controlling reservoir and vertical zonation structure, based on well logging, seismic data and production test data, comprehensive probability method was used to obtain logging reservoir factors to quantitatively characterize fracture-pore reservoirs, and to predict the distribution of the reservoirs by combining seismic motion inversion. The results show that the logging reservoir factor can better reflect the reservoir development than the single well logging resistivity model. The combination of the seismic motion inversion based on phase controlling theory and logging reservoir factor is effective to predict the fracture-pore reservoir quantitatively. If the predicted value is greater than the threshold value, the reservoir develops. The larger the predicted value is, the more developed the fractured reservoir is. The lithology and original sedimentary laminar formation result in the effective reservoirs in the form of quasi-continuously layer as the shape of short mounds or beans in section. The high-quality reservoirs are controlled by vertical zonation, fault system and structural location. The good reservoirs overall distribute near faults zone, anticline, faulted anticline, fault block or other structural high position. The reservoir properties in the moderately-weakly weathered facies are the best, the strongly weathered facies is medium, and the reservoirs in the unweathered facies are only locally developed. The research results have great application and popularization value for the prediction of fracture-pore reservoir in basement with metamorphic clastic rock.
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Reservoir architecture and fine characterization of remaining oil of Chang 3 reservoir in Zhenbei oilfield,Ordos Basin
ZHANG Haoyu, LI Mao, KANG Yongmei, WU Zemin, WANG Guang
2021, Vol.33(6): 177–188
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doi: https://doi.org/10.12108/yxyqc.20210618
Chang 3 reservoir in well area Zhen 300 in Zhenbei oilfield has entered ultra-high water cut stage, with strong interlayer heterogeneity, and the wells with uneven water absorption accounted for 48% of the total number of tested wells. In order to provide direction for production, it is urgent to further characterize the remaining oil distribution. By using classic architecture analysis methods, combined with rhythm characteristics and seepage laws of composite sand bodies being with dual characteristics of sedimentary unit and seepage unit, four vertical superimposed styles and five plane contact relationships of Chang 3 reservoir in the study area were summarized, and logging identification marks were clearly defined. Two remaining oil controlling factors were clearly pointed out by using the combination of reservoir numerical simulation and production performance. The results show that the imperfect injection-production well pattern is the main factor causing the remaining oil in the isolated and separated superimposed single sand body. The remaining oil in the cutting and stacked single sand body is mainly concentrated at the top of the sand body. The single sand body contacted with the bay are likely to cause the enrichment of remaining oil in the flanks of the river channel. Due to the good connectivity and high water drive efficiency, the alternative and side-cut contact sand bodies are not enriched with remaining oil. The connection relationship of butt-joint single sand body is complex, and a single discriminant method is easy to cause mismatch between injection and production, and then form local remaining oil. The research result takes into account the control effect of reservoir architecture on the remaining oil and the seepage characteristics of the flow units, so it can effectively guide the deployment of reservoir injection and production well pattern, and provide new ideas for the adjustment of the subsequent water injection development of the oilfield.