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Reservoir-forming mechanism of carbonate dolomitization of Permian Changxing Formation in northeastern Sichuan Basin
HE Wenyuan, YUN Jianbing, ZHONG Jianhua
2022, Vol.34(5): 1–25
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Diagenesis of alkaline lacustrine dolomitic reservoirs of Permian Fengcheng Formation in Mahu Sag
LYU Zhengxiang, LIAO Zheyuan, LI Yuefeng, SONG Xiuzhang, LI Xiang, HE Wenjun, HUANG Liliang, QING Yuanhua
2022, Vol.34(5): 26–37
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Difference of maturity parameters of mixed crude oil and its geological significance:A case study of Ordovician in Tuofutai area,Tabei uplift
CHEN Zhonghong, CHAI Zhi
2022, Vol.34(5): 38–49
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239 )
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322
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Microscopic pore structure characteristics of shale of Ordovician Wulalike Formation in western Ordos Basin
ZHANG Fengqi, LI Yinong, LUO Julan, REN Xiaofeng, ZHANG Lanxin, ZHANG Jieyu
2022, Vol.34(5): 50–62
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317 )
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Sedimentary characteristics of fan delta in restricted lacustrine basin of Permian Xiazijie Formation in Mahu Sag
YANG Fan, BIAN Baoli, LIU Huiying, YAO Zongquan, YOU Xincai, LIU Hailei, WEI Yanzhao
2022, Vol.34(5): 63–72
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243 )
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Sedimentary environment and organic matter enrichment mechanism of Permian Lucaogou Formation in Jiye-1 well area,Jimsar Sag
LUO Jinchang, TIAN Jijun, MA Jinghui, YAN Jiaqi, LIANG Yafei, HU Zhuohao
2022, Vol.34(5): 73–85
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293 )
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Deep-reservoir characteristics and main controlling factors of Triassic Xujiahe Formation in northwestern Sichuan Basin
SU Yiqing, YANG Wei, JIN Hui, WANG Zhihong, CUI Junfeng, ZHU Qiuying, WU Xueqiong, BAI Zhuangzhuang
2022, Vol.34(5): 86–99
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Sedimentary characteristics and reservoir control of beach bar in faulted lake basin:A case study of Cretaceous Tongbomiao Formation in Tanan Sag
SUI Liwei, YANG Wenlu, LI Junhui, FAN Xiaodong, JIANG Hongfu, WEN Quan, ZHANG Dazhi, YUAN Yong
2022, Vol.34(5): 100–109
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Internal sedimentary structure and stacking patterns of deep-water lobe complex:A case study of Miocene zone D in Akpo oilfield, Niger Delta Basin
DUAN Ruikai, ZHANG Xu, GUO Fuxin, CHEN Guoning, HU Guangyi, ZOU Jingyun
2022, Vol.34(5): 110–120
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267 )
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Quantitative characterization of gravel roundness of sandy conglomerates of Triassic Baikouquan Formation in Mahu Sag
PENG Miao, ZHANG Lei, TAO Jinyu, ZHAO Kang, ZHANG Xianghui, ZHANG Changmin
2022, Vol.34(5): 121–129
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Hydrocarbon accumulation characteristics of the second member of Sinian Dengying Formation in the north slope of central Sichuan paleo-uplift
ZHOU Hongfei, DAI Xin, JIA Min, ZHANG Rui, LI Guohui, LI Nan, YANG Qiang, BAI Rong
2022, Vol.34(5): 130–138
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Source-reservoir characteristics and configuration of the third member of Middle Triassic Leikoupo Formation in central Sichuan Basin
RUAN Yunbo, ZHOU Gang, HUO Fei, SUN Haofei, GUO Pei, LUO Tao, JIANG Huachuan, WEN Huaguo
2022, Vol.34(5): 139–151
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Physical simulation experiment of steam flooding in horizontal wells of Neogene heavy oil reservoir in Lvda oilfield,Bohai Sea
MA Kuiqian, LIU Dong, HUANG Qin
2022, Vol.34(5): 152–161
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Oil production contribution evaluation method of gas/water drive in gas-cap and edge-water reservoirs
MENG Zhiqiang, GE Lizhen, ZHU Xiaolin, WANG Yongping, ZHU Zhiqiang
2022, Vol.34(5): 162–170
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Reservoir-forming mechanism of carbonate dolomitization of Permian Changxing Formation in northeastern Sichuan Basin
HE Wenyuan, YUN Jianbing, ZHONG Jianhua
2022, Vol.34(5): 1–25
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405 )
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doi: https://doi.org/10.12108/yxyqc.20220501
Sichuan Basin is an important petroliferous basin in China,and carbonate rocks of Permian Changxing Formation in northeastern Sichuan Basin are important gas producing strata. The natural gas fields discovered in recent years such as Puguang,Longgang and Yuanba are important bases for West-to-East Gas Transmission,and play an important role in the national oil and gas strategic security. Based on the analysis of field outcrop samples and drilling cores,reservoir-forming mechanism of carbonate dolomitization and main controlling factors of Permian Changxing Formation in northeastern Sichuan Basin were analyzed. The results show that:(1)The gas reservoir of Permian Changxing Formation in northeastern Sichuan Basin is mainly dolomitic gas reservoir,and the poor reservoir capacity of reef limestone is related to asphalt filling,which is a gas source layer. The reef cap dolomite has more developed reservoir space according to field outcrop investigation. The dolomite at the top of Changxing Formation in Puguang gas field is a kind of non-reef-cap dolomite,which reveals that the pure dolomite at the top of Changxing Formation is a gas-bearing reservoir and has little relationship with biogenic reef. (2)The reservoir space of dolomitic reservoirs of Changxing Formation in northeastern Sichuan Basin includes karst caves,intercrystalline pores,intracrystalline dissolved pores and intracrystalline fracture,which are completely formed by dolomitization in the process of diagenesis.(3)There are five genetic mechanisms for dolomitization of Changxing Formation in northeastern Sichuan Basin:exposed fresh water leaching and evaporation pumping,seepage reflux or saline reflux platform metasomatism,buried diagenetic dolomitization,hydrothermal dolomitization and weathering metasomatic dolomitization,with the former two being dominant. Supergene and early diagenetic dolomites are controlled by sedimentary microfacies,and there are different genetic models in different regions. Dolomitization often occurs in reefs in northeastern Sichuan Basin,especially at the top of reefs. The reservoir properties have been greatly improved after dolomitization.(4)The discovery of dolomitic gas reservoirs at the middle and upper part of Changxing Formation in the study area is of great theoretical significance and industrial value. The dolomite at the top of Changxing Formation has good natural gas storage capacity, and industrial gas reservoirs can be formed as long as the corresponding conditions are available. Changxing Formation outside the platform margin of Kaijiang-Liangping trough(including Pingchang trough)has the potential of large industrial gas fields.
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Diagenesis of alkaline lacustrine dolomitic reservoirs of Permian Fengcheng Formation in Mahu Sag
LYU Zhengxiang, LIAO Zheyuan, LI Yuefeng, SONG Xiuzhang, LI Xiang, HE Wenjun, HUANG Liliang, QING Yuanhua
2022, Vol.34(5): 26–37
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doi: https://doi.org/10.12108/yxyqc.20220502
Based on the data of polarizing microscope identification,scanning electron microscope energy spectrum analysis,inclusion temperature measurement,oxygen isotope analysis,X-ray diffraction and organic geochemical analysis,the diagenesis and diagenetic evolution sequence of alkaline lacustrine dolomitic reservoirs of Permian Fengcheng Formation in Mahu Sag of Junggar Basin were studied. The results show that:(1)The dolomitic reservoirs of Permian Fengcheng Formation in Mahu Sag are typical alkaline lacustrine deposits,and are composed of various dolomitic rocks,which mainly consists of dolomitic tuff and dolomitic sedimentary tuff.(2)Devitrification of dolomitic rocks is common,authigenic minerals mainly consist of siliceous minerals,calcium magnesium carbonate minerals,aluminosilicate minerals and non-calcium magnesium carbonate minerals,dissolution mainly occurs in aluminosilicate minerals and saline minerals,diagenetic fractures and multi-stage structural fractures are generally developed,and hydrocarbon charging exhibits three major stages.(3)Most dolomitic rocks have entered phase A of mesodiagenesis,a few followed by phase B of mesodiagenesis,and devitrification occurred in phase A of eodiagenesis. Authigenic dolomites are formed in three different periods from early to late, and are mostly developed in phase B of eodiagenesis. Non-calcium magnesium carbonate minerals are mainly formed in syndiagenetic stage. Dissolution with three stages is mainly developed in phase A of mesodiagenesis. Hydrocarbon charging began in phase B of eodiagenesis,and kept successive charging for the longest time in phase B of mesodiagenesis. Devitrification,dissolution of feldspar and non-calcium magnesium carbonate minerals,and structural fractures are imperative to the formation of dolomitic reservoirs of Fengcheng Formation in Mahu Sag.(4)The reservoir pores formed by devitrification provide reservoir space for early hydrocarbon charging. The acidic fluid released by thermal evolution of high-quality alkaline lacustrine source rocks dissolved aluminosilicate minerals and saline minerals in dolomitic rocks,which effectively improves reservoir properties.
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Difference of maturity parameters of mixed crude oil and its geological significance:A case study of Ordovician in Tuofutai area,Tabei uplift
CHEN Zhonghong, CHAI Zhi
2022, Vol.34(5): 38–49
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doi: https://doi.org/10.12108/yxyqc.20220503
Based on the characteristics of physical properties,group component,molecular marker and maturity of Ordovician crude oil in Tuofutai area of Tabei uplift in Tarim Basin,the differences of maturity parameters after crude oil mixing and their geological significance were analyzed. The results show that:(1)Although different maturity parameters indicate that the crude oil is in mature to high maturity stage,the values of maturity calculated from light hydrocarbons and diamondoids are higher than that calculated from steranes,terpanes and aromatics. This phenomenon is caused by the mixing of crude oil with different maturity,which can be used as favorable evidence for multi-stage filling and mixing. Light hydrocarbons and diamondoids mainly reflect the maturity of latefilled crude oil,while steranes and terpanes,phenanthrenes and dibenzothiophenes usually indicate the maturity of early-filled crude oil.(2)Due to the difference in resistance to biodegradation of different maturity parameters,biodegradation will lead to different changes in maturity parameters.(3)The differences of maturity parameters calculated from the light hydrocarbons,diamondoids,steranes,terpanes and aromatics on the plane reflect the changes of hydrocarbon filling pathway or the activity of oil-source faults.(4)The physical properties of crude oil are a comprehensive reflection of various components and basic parameters for analyzing regional hydrocarbon accumulation mechanism.
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Microscopic pore structure characteristics of shale of Ordovician Wulalike Formation in western Ordos Basin
ZHANG Fengqi, LI Yinong, LUO Julan, REN Xiaofeng, ZHANG Lanxin, ZHANG Jieyu
2022, Vol.34(5): 50–62
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doi: https://doi.org/10.12108/yxyqc.20220504
By means of argon ion polishing field emission scanning electron microscope observation,X-ray dif-fraction analysis,helium porosity measurement,cryogenic nitrogen adsorption-desorption and other experimental methods,combined with FHH fractal theory model,the microscopic pore structure characteristics of different types of shale of Ordovician Wulalike Formation in western Ordos Basin were characterized. The results show that:(1)The study area has complex mineral composition,relatively stable clay mineral content,high brittle mineral content and wide variation range. It can be divided into three types of lithofacies,including siliceous shale lithofacies,mixed shale lithofacies and calcareous shale lithofacies from bottom to top.(2)The overall porosity of the study area is low,mainly ranging from 0.16% to 1.50%,with an average of 1.20%. Microfracture development results in a small amount of porosity greater than 4.00%. Siliceous shale has the highest porosity,calcareous shale has the lowest porosity,and mixed shale has the porosity between them. The pore types are complex and closely related to lithofacies. The calcareous shale is compact as a whole,dominated by intercrystalline pores and dissolved pores,and mainly slit pores. The pores of siliceous shale are relatively developed,which are mostly intergranular pores,interlayer fractures and microfractures of clay minerals. The open pores are mainly flat,and inkbottle shaped amorphous pores are occasionally seen.(3)The pore structure in the study area can be divided into three types. TypeⅠis mainly composed of 2-4 nm mesopores,with large pore volume and well-developed mesopores,which are common in siliceous shale. Type Ⅱ is dominated by 0-4 nm micropores and mesopores,with less macro-pores,which are common in siliceous shales and mixed rocks. Type Ⅲ is dominated by 50-100 nm macropores,but small in size,which are common in calcareous shale.(4)The microscopic pore structure of shale in the study area has obvious fractal characteristics,complex internal structure and strong heterogeneity. The higher the TOC,clay minerals and quartz content,the more complex the pore structure and pore surface.(5)The siliceous shale reservoir in the study area has the best pore structure and is rich in organic matter,which is the most favorable exploration target.
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Sedimentary characteristics of fan delta in restricted lacustrine basin of Permian Xiazijie Formation in Mahu Sag
YANG Fan, BIAN Baoli, LIU Huiying, YAO Zongquan, YOU Xincai, LIU Hailei, WEI Yanzhao
2022, Vol.34(5): 63–72
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doi: https://doi.org/10.12108/yxyqc.20220505
Based on core observation,well logging and seismic interpretation,the sedimentary settings and sedimentary system of Permian Xiazijie Formation in Mahu Sag were systematically analyzed by using paleogeomorphology,lithofacies characteristics,single well facies and well-tie sedimentary facies contrast. The results show that:(1)Controlled by the accommodation space,the lithologies of Xiazijie Formation in Mahu Sag are mostly sandy conglomerate,and fan delta deposits are developed. The paleogeomorphology formed by tectonic movement controls the sedimentary space. The tectonic pattern shows "fault in the north,denudation in the west,and overlap in the southeast".(2)There are four major provenance systems in Xiazijie Formation in Mahu Sag. The northern region is a long axis far-source area with low sand-stratum ratio and thin reservoirs. The western,southern and eastern regions are mainly short-axis near-source areas with rapid deposition,large vertical thickness and narrow plane distribution of facies zone. However,a long-axis far-source is developed in the southern region.(3)The Xiazijie Formation in Mahu Sag is mainly composed of coarse and medium conglomerates with poor sorting,medium roundness and high content of matrix. The reservoirs are mainly distributed near the slope break zone and developed in braided channels and underwater distributary channels.(4)During the sedimentary period of Xiazijie Formation,the accommodation space is large at the mountain side of Mahu Sag where huge thick fan delta sand gravel body developed and extended limitedly. The narrow and long valley landform in Manan area provides a channel for sediment transportation to the middle of Mahu Sag. This long axis far-source sedimentary system can form large-scale effective reservoirs,the sand-stratum ratio is greater than 50%,and the sediment sorting and roundness are relatively good,which is a favorable reservoir development zone.
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Sedimentary environment and organic matter enrichment mechanism of Permian Lucaogou Formation in Jiye-1 well area,Jimsar Sag
LUO Jinchang, TIAN Jijun, MA Jinghui, YAN Jiaqi, LIANG Yafei, HU Zhuohao
2022, Vol.34(5): 73–85
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doi: https://doi.org/10.12108/yxyqc.20220506
The paleoenvironment,paleoproductivity and organic matter enrichment mechanism of hydrocarbon source rocks of Permian Luchaogou Formation in Jimsar Sag were investigated by X-ray diffraction,organic carbon testing, major and trace element testing and saturated hydrocarbon chromatography. The results show that:(1)The source rocks of Permian Lucaogou Formation in Jiye-1 well area of Jimsar Sag are dominated by feldspars-quartz mixed fine-grained sedimentary rocks and clayey mixed fine-grained sedimentary rocks. The sources of organic matter include terrestrial organic matters and marine algae,with a greater contribution from marine algae. The average TOC values are 5.93% and 5.69% in the first and second(Lu-1 and Lu-2)members of Lucaogou Formation respectively.(2)The content of Ba element in rock samples in the study area is high,with an average mass fraction of 12 052.89×10-6. The n-alkane curve of the source rock shows unimodal distribution. The main peak carbon of Lu-1 member is C17 and C19,with weak odd carbon predominance,and the main peak carbon of Lu-2 member is C 19,with odd carbon predominance,and the overall isoprene-like hydrocarbons are rich in Pr and Ph.(3)The Luchaogou Formation in the study area has an overall arid-saline reductive depositional background. During the depositional period of Lu-1 member,the overall depositional environment was arid,with shallow palaeohydric depth and high palaeo-salinity,and the water was stratified to form a stable reduction environment with stronger palaeo-productivity than Lu-2 member. During the depositional period of Lu-2 member,t he depositional environment was semi-wet to semi-arid,with deeper palaeohydric depth,lower palaeo-salinity and good reduction environment.(4)The organic matter enrichment of source rocks in the study area is controlled by terrigenous clastic supply,paleoproductivity and paleoclimate. Throughout the sedimentary period of Lucaogou Formation,it was in a stable reducing environment,which is a typical "productivity enrichment mode". The influence of palaeoclimate, palaeosalinity and terrigenous debris resulted in the low TOC content of Lu-2 member.
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Deep-reservoir characteristics and main controlling factors of Triassic Xujiahe Formation in northwestern Sichuan Basin
SU Yiqing, YANG Wei, JIN Hui, WANG Zhihong, CUI Junfeng, ZHU Qiuying, WU Xueqiong, BAI Zhuangzhuang
2022, Vol.34(5): 86–99
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doi: https://doi.org/10.12108/yxyqc.20220507
The deep clastic rocks of Triassic Xujiahe Formation in Northwest Sichuan are important areas for natural gas exploration,and reservoir quality is very important to the development scale of gas reservoirs. The reservoir characteristics and main controlling factors of Triassic Xujiahe Formation in northwestern Sichuan Basin were analyzed by using core,outcrop,seismic and logging data,and the favorable reservoir development areas were evaluated. The results show that:(1)The deep effective reservoirs of Triassic Xujiahe Formation belong to low porosity and low permeability reservoirs,which are mainly developed in delta underwater distributary channel and estuarine bar. The lithologies are mainly coarse sandstone and pebbly fine sandstone,and the reservoir space mainly includes primary pores,intragranular and intergranular dissolved pores and fractures.(2)The development of effective reservoir is mainly controlled by sedimentary microfacies,diagenesis and structural fracturing. The underwater distributary channel sand bodies are most favorable. The dissolved pores formed by dissolution and the transformation of primary pores effectively improve the porosity and permeability of sand bodies. The structural fractures produced by fracturing play an important role in the formation of effective reservoirs.(3)A large area of sand bodies are developed in the underwater distributary channel of delta front of Xujiahe Formation in the study area,and many primary pores were preserved in the early rapid burial process. In the process of late burial diagenesis,the organic acids produced in the process of hydrocarbon generation caused a large number of dissolved pores. A large number of fractures formed by Himalayan tectonic movement improved the reservoir physical properties.(4)The relatively high-quality reservoirs of Triassic Xujiahe Formation in northwestern Sichuan Basin are mainly distributed in Laoguanmiao-Wenxingchang-Zhebachang,Zhongtaishan,Liyamiao and Jianmenguan area.
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Sedimentary characteristics and reservoir control of beach bar in faulted lake basin:A case study of Cretaceous Tongbomiao Formation in Tanan Sag
SUI Liwei, YANG Wenlu, LI Junhui, FAN Xiaodong, JIANG Hongfu, WEN Quan, ZHANG Dazhi, YUAN Yong
2022, Vol.34(5): 100–109
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doi: https://doi.org/10.12108/yxyqc.20220508
Based on core observation,well logging analysis and seismic interpretation data,the sedimentary characteristics,distribution law and reservoir accumulation model of beach bar sand bodies of Cretaceous Tongbomiao Formation in Tanan Sag were studied. The results show that:(1)the beach bar microfacies of Cretaceous Tongbomiao Formation in Tanan Sag can be divided into beach sand and bar sand according to lithology and sedimentary structural characteristics,and there are three sedimentary assemblages,including beach bar symbiosis, beach without bar and bar without beach. Beach bar symbiotic assemblage is developed in the western gentle slope zone of Tanan Sag,beach without bar assemblage is developed in the eastern steep slope zone and the concave bank of lake shoreline,and bar without beach assemblage is developed in underwater paleouplift and convex bank of lake shoreline.(2)The development characteristics and distribution law of beach bar are mainly controlled by ancient landform,ancient water depth and ancient wind direction. The paleogeomorphology of the slope zone and underwater central uplift zone in the sag controls the sedimentary range of beach bar. The NE trending ancient wind field controls the beach bar to be distributed in the NE direction along the lake shoreline on the plane. The difference of ancient water depth between the eastern and western sub depressions controls the sedimentary properties and thickness of beach bar.(3)Beach bar reservoir formation in Tanan Sag mainly includes internal accumulation of "source reservoir symbiosis" and lateral accumulation of "source reservoir connection". The internal accumulation of "source reservoir symbiosis" mainly forms lithologic reservoirs,which are mainly developed in the near source sag belt of the eastern sub-depression,and the potential area is near source sag. The lateral accumulation of "source reservoir connection" mainly forms structural lithologic reservoirs,which are mainly developed in the western slope zone,and the potential area is in the reverse fault step zone.
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Internal sedimentary structure and stacking patterns of deep-water lobe complex:A case study of Miocene zone D in Akpo oilfield, Niger Delta Basin
DUAN Ruikai, ZHANG Xu, GUO Fuxin, CHEN Guoning, HU Guangyi, ZOU Jingyun
2022, Vol.34(5): 110–120
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doi: https://doi.org/10.12108/yxyqc.20220509
Based on the core,well logging and seismic data of Miocene zone D in Akpo oilfield,Niger Delta Basin, the composition of sedimentary units,sedimentary microfacies,sedimentary evolution and reservoir stacking patterns were studied,and the internal sedimentary structure of deep-water lobe complex was revealed. The results show that:(1)The deep-water lobe complex of Miocene zone D in Akpo oilfield is composed of four stages of single lobe and three branch channels,and the sedimentary evolution of deep-water lobe complex is controlled by interaction between single lobe and branch channels. The trend of branch channels controls the plane distribution of single lobe, and the growth of single lobe affects the lateral migration of branch channels.(2)The sedimentary microfacies of deep-water lobe complex in the study area could be divided into five types:lobed axis,lobed margin,sedimentary channel,erosive channel and semi-pelagic mud.(3)Considering spatial arrangement of microfacies units,the internal sedimentary structure of deep-water lobe complex could be divided into four stacking patterns,including lobe margin with lobe margin,lobe axis with lobe axis,upper lobe axis with lower lobe margin and upper lobe margin with lower lobe axis,and different reservoir stacking pattern has different reservoir quality and connectivity. Branch channel erodes and transforms the underlying lobe,and then affects the lateral reservoir connectivity which is determined by the filling property of branch channel. The research results have guiding significance for the optimization of production system and well deployment in Akpo oilfield,and have achieved good application results.
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Quantitative characterization of gravel roundness of sandy conglomerates of Triassic Baikouquan Formation in Mahu Sag
PENG Miao, ZHANG Lei, TAO Jinyu, ZHAO Kang, ZHANG Xianghui, ZHANG Changmin
2022, Vol.34(5): 121–129
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doi: https://doi.org/10.12108/yxyqc.20220510
The gravel roundness characterization is important for facies analysis of sandy conglomerate strata. Based on the two parameters of gravel particle cross-sectional area and perimeter,the calculated roundness value was normalized to carry out quantitative characterization of roundness,so as to study the roundness characteris-tics of sandy conglomerates of Triassic Baikouquan Formation in Mahu Sag,and then analyze its sedimentary facies. The results show that:(1)The gravel roundness measurement process includes three steps:dividing the measurement unit,extracting the gravel image and calculating the morphological parameters,then the quantitative calculation of the de-flat roundness was completed,and finally the quantitative classification of the roundness was carried out.(2)The roundness of the gravel in the second coring of well Ma 15 is better than that in the third coring. The spherical and ellipsoidal gravel accounts for 19.89% and 38.98% respectively. The Rdn value of the second coring gravel shows a decreasing trend,and the roundness becomes worse as a whole,from subrounded to sub-angular and sub-rounded. The Rdn value of the third coring gravel gradually increases from the lower part to the upper part,and the roundness becomes better as a whole, from sub-angular to sub-angular and sub-rounded.(3)From the bottom to the top,the sedimentary facies of the second member of Baikouquan Formation of well Ma 15 transits from seasonal braided channel of delta plain to perennial braided channel of delta plain,corresponding to the change of gravel roundness from sub-angular to sub-angular and sub-rounded.
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Hydrocarbon accumulation characteristics of the second member of Sinian Dengying Formation in the north slope of central Sichuan paleo-uplift
ZHOU Hongfei, DAI Xin, JIA Min, ZHANG Rui, LI Guohui, LI Nan, YANG Qiang, BAI Rong
2022, Vol.34(5): 130–138
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doi: https://doi.org/10.12108/yxyqc.20220511
The hydrocarbon accumulation characteristics of the second member of Sinian Dengying Formation (Deng 2 member)in the north slope of central Sichuan paleo-uplift were comprehensively studied by means of fine core description,thin section identification,hydrocarbon source correlation and seismic facies characterization. The results show that:(1)During the depositional period of Deng 2 member,restricted platform facies and platform margin facies are mainly developed in the north slope,with relatively developed platform margin algal mound facies and grain shoal facies. The average values of reservoir thickness,storage-land ratio,porosity and permeability of Dengying 2 member are 176.6 m,34.6%,4.4% and 3.6 mD,respectively. It belongs to low porosity and low permeability reservoir,and the reservoir quality is better than that in Gaomo area as a whole. (2)The Sinian-Cambrian in the north slope have good accumulation conditions,multiple sets of source rocks are developed, with two types of source-reservoir configuration:upper source and lower reservoir,and side source and side reservoir. The natural gas of Dengying 2 member is mainly supplied by source rocks from Qiongzhusi Formation and the deep Sinian source rocks.(3)Deng 2 member in the study area has the conditions for forming structural-lithologic gas reservoirs and lithologic gas reservoirs. The large-scale faults in the updip direction and the effective sealing of lithologic tight zones are the key for hydrocarbon accumulation and formation of different gas water systems. (4)Deng 2 member in the study area has better reservoir conditions,source rocks and source-reservoir configuration than that in Gaomo area,showing the geological basis for forming large gas fields. The amount of trap resources has reached 1.05×1012 m3,with great exploration potential,so it is an important replacement field for large-scale gas field exploration in central Sichuan paleo-uplift.
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Source-reservoir characteristics and configuration of the third member of Middle Triassic Leikoupo Formation in central Sichuan Basin
RUAN Yunbo, ZHOU Gang, HUO Fei, SUN Haofei, GUO Pei, LUO Tao, JIANG Huachuan, WEN Huaguo
2022, Vol.34(5): 139–151
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doi: https://doi.org/10.12108/yxyqc.20220512
Based on the data of core observation and thin section identification,combined with the analysis results of rock physical properties,X-ray diffraction,total organic carbon(TOC)content,rock pyrolysis and kerogen carbon isotope,the characteristics of source rocks and reservoirs of the third member of Middle Triassic Leikoupo Formation(T2 l3)in the Central Sichuan Basin and their configuration relationship were systematically studied. The results show that:(1)There is a set of hydrocarbon source rocks mainly composed of shale and marl developed in the second sub-member of T2l3(T2l32)in Central Sichuan Basin,with a thickness of 20-100 m. The average TOC value of shale is 1.08%,up to 4.01%,and the average TOC value of marl is 0.40%. The organic matters are mainly type Ⅱ1,followed by type Ⅰ,which are in the early stage of high maturity to over maturity,and have good hydrocarbon generation potential.(2)A set of reservoir mainly composed of silty dolomite and sandy dolomite is developed in the third sub-member of T2 l3(T2 l33). The reservoir space is mainly composed of intercrystalline(dissolved)pores and intergranular dissolved pores,with an average porosity of 4.05% and an average permeability of 1.1 mD. It has the characteristics of low porosity and medium permeability.(3)The source rocks of T2 l32 have a good source-reservoir configuration relationship with the reservoirs of T2 l33,which can form the hydrocarbon accumulation model of "lower generation and upper accumulation" and "self-generation and self-accumulation". The fracture system is not only an oil and gas migration channel,but also an important reservoir space. The overlying gypsum salt rocks of the fourth member of Leikoupo Formation and the mudstone of the first member of Xujiahe Formation are effective caprocks.
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Physical simulation experiment of steam flooding in horizontal wells of Neogene heavy oil reservoir in Lvda oilfield,Bohai Sea
MA Kuiqian, LIU Dong, HUANG Qin
2022, Vol.34(5): 152–161
Abstract
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doi: https://doi.org/10.12108/yxyqc.20220513
A physical simulation experiment of steam flooding in horizontal wells was carried out on a typical heavy oil reservoir of Neogene in Lvda oilfield,Bohai Sea. The long sand-packing tube model was used to analyze the effects of steam temperature,injection rate and oil viscosity on the steam flooding effect. The dynamic characteristics of steam flooding in different production stages,the variation of temperature and the mechanism of steam flooding were discussed. The results show that:(1)The physical simulation experiment of steam flooding adopts a long core single tube model,with an inner diameter of 2.5 cm and a length of 50.0 cm. After sand filling, the porosity of the model is 35.0%,the permeability is 4 500 mD,and the steam dryness is 0.7. The steam injection temperature is 250℃,the steam injection rate is 6 mL/min,and the oil displacement efficiency can reach 82.52%.(2)The steam flooding process in the study area can be divided into four stages:start-up,stable flooding, steam breakthrough and steam denudation. The temperature field of the steam chamber between the injection and production horizontal wells is not balanced,the temperature at the bottom of the horizontal well expands rapidly, and the temperature at the top expands slowly. During the start-up and stable flooding stages,the temperature field presents a "triangular" advancing mode. The temperature field of the steam chamber expands along the diagonal in the steam breakthrough and denudation stages. The recovery percent in the steam flooding stage is 51.86%, the stable flooding stage is the main oil production stage,and the recovery percent is 39.06%.(3)Thermal viscosity reduction is the main mechanism of steam flooding in Lvda oilfield. The denudation of high-temperature steam, distillation effect,and the improvement of microscopic sweep efficiency also affect the oil displacement efficiency.
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Oil production contribution evaluation method of gas/water drive in gas-cap and edge-water reservoirs
MENG Zhiqiang, GE Lizhen, ZHU Xiaolin, WANG Yongping, ZHU Zhiqiang
2022, Vol.34(5): 162–170
Abstract
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doi: https://doi.org/10.12108/yxyqc.20220514
Based on the study of oil-gas and oil-water two-phase seepage law in S31 reservoir of Jinzhou oilfield, combined with the material balance equation,the oil production contribution evaluation method of oil of gas/water drive was derived and established,and the contribution of gas drive and water drive in the cumulative oil production of this kind of reservoir was quantified,which lays a foundation for the evaluation of recoverable reserves and development effects of gas-cap and edge-water reservoirs. The results show that:(1)The horizontal well pattern divides the gas-cap and edge-water reservoirs into two parts,the gas-cap gas drive and the edge-water drive, and the recoverable reserves and development effects can be evaluated respectively.(2)The evaluation method reflects the relationships of the oil production contributed by gas/water drive with the production gas-oil ratio and water cut. The cumulative oil production contributed by gas drive and water drive can be calculated by using the production performance data.(3)Using the cumulative oil production contributed by gas drive and water drive and production performance data,combined with the gas drive and water drive characteristic curves,and development effect evaluation chart,the recoverable reserves and development effects of gas-cap and edge-water reservoirs can be evaluated,so as to point out the direction for next potential tapping of the oilfield.