石油实验地质

2017, 39(2): .

Abstract(315) PDF-CN(336)

Abstract:

Effects of preservation conditions on enrichment and high yield of shale gas in Sichuan Basin and its periphery

Wei Xiangfeng, Li Yuping, Wei Zhihong, Liu Ruobing, Yu Guangchun, Wang Qingbo

2017, 39(2): 147-153. doi: 10.11781/sysydz201702147

Abstract(1481) PDF-CN(683)

Abstract:
The main controlling factors of shale gas preservation conditions and evaluation of the Niutitang and Wufeng-Longmaxi formations in the Sichuan Basin and its periphery, were considered in view of typical shale gas wells in different regions with different gas contents and production. The preservation conditions of shale gas were controlled by several factors such as the roof and bottom rocks, the sealing properties of shale itself, the structural reformation degree, and the timing of when the shale reservoirs were reformed, etc. Adjacent rock conditions and its sealing effect was the basic factor determining whether the early formed hydrocarbons were preserved. Late tectonic activity controlled the effusion, degree and abundance of shale gas, and it was a key factor in shale gas preservation. Meanwhile, we found that preservation conditions had an obvious effect on gas content, porosity, electrical resistivity, water saturation and gas composition. With poor preservation conditions, the gas content, porosity and resistivity were low, but water saturation and N₂ content were high. All these parameters could be used as indirect indexes of shale gas preservation evaluation. A preservation evaluation system with 5 types and 28 parameters for the Lower Paleozoic marine shale gas was set up, illustrating the time and space combination of sealing conditions, the sealing properties of shale itself, and tectonic effects (structural reformation time and degree, fault). The parameters of gas-bearing capacity of shale layer and the pressure coefficients also guide the evaluation of preservation conditions.

Sedimentary environment of the Lower Cambrian organic-rich shale and its influence on organic content in the Upper Yangtze

Zhang Yuying, He Zhiliang, Gao Bo, Liu Zhongbao

2017, 39(2): 154-161. doi: 10.11781/sysydz201702154

Abstract(1134) PDF-CN(428)

Abstract:
Rock samples from 3 typical Lower Cambrian outcrops in the Upper Yangtze have been collected to test the content of total organic carbon (TOC) as well as major elements and trace elements. The characteristics of primary productivity and redox in the Early Cambrian, and their effect on organic enrichment were analyzed. In stages Ⅰ-Ⅱ, the shallow shelf was anoxic and ferruginous with a high primary productivity; the deep shelf was anoxic and sulphate rich with a low primary productivity; and the slope-basin where upwelling brought massive nutrients was anoxic and ferruginous with an extremely high primary productivity. In stage Ⅲ, the shelf was changed to oxic communicating well with the open sea and decreasing the preservation of organic matter. Although the slope-basin became oxic-suboxic in this stage, the primary productivity was high enough to prevent organic matter from complete aerobic degradation before it was buried. In general, organic-rich shale in the shelf which was deposited in a reducing environment was controlled by in the Eh at the bottom; organic-rich shale in slope-basin with a higher TOC content was controlled by primary productivity as well as the sedimentary environment. Organic-rich shale of the Lower Cambrian deposited on the shelf and in the slope-deep basin would be a target layer for shale gas exploration and exploitation.

Peculiar accumulation conditions for shale gas in the Lower Cambrian in Qianzhong uplift and its periphery

Zhang Peixian

2017, 39(2): 162-168. doi: 10.11781/sysydz201702162

Abstract(838) PDF-CN(350)

Abstract:
The Lower Cambrian Niutitang Formation shale is characterized by large thickness, high organic carbon content, high thermal evolution degree and high brittle mineral content in the Qianzhong uplift and its periphery. It has the basic geological conditions for shale gas accumulation. However, after many years of exploration, the study area has not made a substantial breakthrough, and some peculiar conditions for shale gas accumulation are the main controlling factors. Through the systematic analysis of outcrop sections and the data from wells including Huangye 1, Longye 1 and Dingshan 1, this paper focuses on the study of the basic geological characteristics of shale, including sedimentary facies, shale distribution, organic carbon content, thermal evolution degree, and the shale reservoir characteristics, including reservoir types, reservoir physical properties and gas content. The peculiarities of shale gas accumulation conditions are mainly manifested in two aspects: (1) The particularity of high shale thermal evolution degree, with complex hydrocarbon generation and expulsion history, is not conducive to gas occurrence and enrichment. (2) The particularity of the shale reservoir. Complex thermal evolution and strong diagenesis resulted in low porosity, especially little organic matter pores and small diameter, which made the reservoir property of shale very poor. On this basis, some parameters for shale gas exploration were selected, and some favorable areas for shale gas enrichment were evaluated. The Huangping region in the Qiannan Depression is a type Ⅰ favorable area of shale gas exploration in the Qianzhong uplift and its periphery, with relatively stable structure, moderate depth, relatively low thermal evolution degree of organic matter, favorable preservation conditions and good gas-bearing capacity. The exploration risk of the Huangping region is relatively low. Because of high maturity, the Qianxi region is a type Ⅱ favorable area to explore for shale gas reservoirs with high thermal evolution degree.

Reservoir densification and tight-oil charging in Yanchang Formation, Ordos Basin

Guo Jigang, Guo Kai, Gong Pengqi, Xu Jing, Guo Jing

2017, 39(2): 169-179. doi: 10.11781/sysydz201702169

Abstract(1217) PDF-CN(352)

Abstract:
The Yanchang Formation in Longdong area, Ordos Basin, is characterized by low porosity and permeability and is considered as a tight-oil reservoir. However, reservoir densification and its influence on oil charging are not well-understood. Based on the analysis of reservoir diagenesis, densification history, oil-water distribution, driving force and resistance, the oil charging process in tight-sand reservoirs was discussed. The results showed that porosity evolution of the Chang 6-Chang 8 reservoirs has gone through four stages, and they became tight during the diagenetic A₁ stage, which was prior to oil charging. And the large resistance due to narrow pore throats made it impossible for buoyancy to be a driving force. Since the tight-sand reservoir is currently oil-saturated with "sweet spots" in locally high-quality reservoir, the excess pressure difference between the Chang 7 source rock and the Chang 6-Chang 8 reservoir is considered to be the main driving force for oil charging in the tight reservoirs.

Microscopic characteristics of shale oil reservoirs in Shahejie Formation in Zhanhua Sag, Bohai Bay Basin

Liu Yi, Lu Zhengyuan, Qi Minghui, Tian Tonghui, Feng Mingshi

2017, 39(2): 180-185. doi: 10.11781/sysydz201702180

Abstract(1003) PDF-CN(293)

Abstract:
The microscopic pore characteristics of shale oil reservoirs are important basic data for exploration and development. Eighteen core samples were collected from the third member of Shahejie Formation (Es₃) in well Luo 69 in the Zhanhua Sag, Bohai Bay Basin, and were analyzed using argon-ion polishing Scanning Electron Microscopy (SEM) to discuss the pore development characteristics of shale oil reservoirs. The shale oil layer in Es₃ showed a transitional lithology of mudstone and limestone, dominated by limy mudstone, argillaceous limestone and mud bearing limestone, with minor thin layers of limestone. Argillaceous inter-particle pores, carbonate dissolved pores, inter-crystal pores and intra-crystal pores are the main pore types of the shale oil layer. Argillaceous pores provided most of reservoir pores of the shale oil layer. Most of the plane porosity was argillaceous inter-particle pores, while calcite dissolved pores made a smaller contribution and inter-crystal pores and intra-crystal pores were less important. The pore diameters of shale oil reservoirs were classed as nano scale and micron scale, and the nano scale pores have an absolute dominance quantitatively. The reservoir pore area was mainly provided by non-dominant micro-scale pores, which should be focused on in shale oil exploration.

Coupling of abnormal overpressure and hydrocarbon charging: A case from the Huagang and Pinghu formations of Xihu Sag, East China Sea Shelf Basin

Chen Zhiyuan, Xu Zhixing, Chen Fei, Xu Guosheng, Zhang Wu

2017, 39(2): 186-194. doi: 10.11781/sysydz201702186

Abstract(937) PDF-CN(253)

Abstract:
Abnormal overpressure in the Huagang and Pinghu formations of the Xihu Sag, East China Sea Shelf Basin was studied based on sonic logging data, organic geochemistry and fluid inclusion testing. The abnormal pressure mainly originated from the lower Huagang Formation, and featured a "step type" distribution in the Xihu Sag. The top interface of high pressure becomes older from the Pinghu tectonic zone to the central inversion structural belt and from the edge to the center of the sag. Conductive overpressure due to the injection of high pressure fluid developed in the study area, and corresponds to good oil and gas reservoirs, which showed that the development of abnormal pressure and hydrocarbon charging had consistency in space. The evolution process of residual formation pressure was simulated using the basin simulation software, indicating that Miocene (15-7 Ma) and Pliocene to Quaternary (3-0 Ma) were the two key periods of residual formation pressure. Hydrocarbon charging history showed that hydrocarbon charging took place twice in the middle-late Miocene and the early Pliocene, which indicated that the development of abnormal pressure and hydrocarbon charging had consistency in time. Therefore, the abnormal overpressure of the Huagang and Pinghu formations coupled in time and space with hydrocarbon charging.

Source-reservoir-seal assemblage of marine Mesozoic-Paleozoic in South Yellow Sea Basin by land-ocean comparison

Yuan Yong, Chen Jianwen, Liang Jie, Zhang Penghui

2017, 39(2): 195-202. doi: 10.11781/sysydz201702195

Abstract(1005) PDF-CN(193)

Abstract:
The South Yellow Sea Basin is the main body of the Lower Yangtze area, where marine Mesozoic-Paleozoic strata are widely distributed. The characteristics of source-reservoir-seal assemblage of the marine Mesozoic-Paleozoic strata in the South Yellow Sea Basin were analyzed by comparing the characteristics of hydrocarbon source rocks, reservoir and cap rocks, and combining with seismic sections, drilling and outcrop data. Four sets of hydrocarbon source rocks developed, including the Lower Cambrian Hetang and Mufushan formations, the Lower Silurian Gaojiabian Formation, the Lower Permian Qixia Formation, and the Upper Permian Longtan and Dalong formations. By comparing the characteristics of hydrocarbon source rocks of the Yangtze land area, the source rocks of the South Yellow Sea Basin may be classed as good hydrocarbon source rocks. Carbonate is the main reservoir type in the South Yellow Sea area, and there are four carbonate reservoir types: porous dolomitic, reef-bank, weathered crust and fractured. The marine strata of South Yellow Sea Basin developed three sets of regional cap rocks and three sets of complete assemblages. The South Yellow Sea Basin has very good oil and gas prospects.

Characteristics of lacustrine carbonate rocks within the upper section of the fourth member of Shahejie Formation in Zhanhua-Chezhen area, Jiyang Depression, Bohai Bay Basin

Bi Caiqin, Zhu Qiang, Hu Zhifang, Lin Hongmei, Shi Quanqing, Hao Yunqing, Xu Yinbo

2017, 39(2): 203-212. doi: 10.11781/sysydz201702203

Abstract(964) PDF-CN(258)

Abstract:
Lacustrine carbonate rocks of the upper section of the fourth member of Shahejie Formation (E s₄) are extensive around the Yihezhuang high in the Zhanhua-Chezhen area in the Jiyang Depression, Bohai Bay Basin. With a great number of oil reservoir discoveries and plenty of drilling data, it has become an ideal location for lacustrine carbonate reservoir study. The carbonate rocks mainly include limestones (internal debris limestones, bioclastic limestones, composite granular limestones and micritelimestones), dolomites (mainly crystalline dolomites, including algaldolomites, algalframework dolomites and so on) and mixed ones (carbonate and clastic rocks). Primary pores, secondary pores and fractures are the main pore types in the reservoir. Both porosity and permeability are low. Reservoir physical properties areclosely related to rock type. Sedimentary environment determines reservoir quality. Compaction, cementation and dissolution deform the reservoir. The sedimentary paleogeographic environmentis a main controlling factor. Reservoirs are most favorable onthe steep slope in the south and east of Yihezhuang high, less favorable on the gentle slope in the north of Chenjiazhuang and Yihezhuang highs, and poor or unfavorable between the reef and beach or in lake and semi-deep water areas.

Fracture properties and formation mechanism of Laixi fault in Laiyang Sag, Jiaolai Basin

Zhang Bo, Wu Zhiping, Liu Hua, Li Zhong

2017, 39(2): 213-221. doi: 10.11781/sysydz201702213

Abstract(921) PDF-CN(243)

Abstract:
The Laixi fault was identified and described, and its geometric features and formation mechanism were also analyzed based on the gravity data and new 2D seismic data of the Laiyang Sag in order to clarify the fracture properties and formation mechanism of the Laixi fault. Several structural styles were found in the Laixi fault, such as zonal distribution, flower structure and dolphin effect. The geologic bodies on both sides of the fault showed a sinistral offset of 4.4 km, indicating a typical sinistral strike-slip fault. From the Late Cretaceous to Paleocene, the tectonic stress field in the study area was NEE-SWW compression. The activity of the Muping-Jimo fault zone converted from extension to dextral strike-slip, while the Laixi fault had an opposite direction, which was a conjugate strike slip fault of the Muping-Jimo fault zone. The Laixi fault did not control the sediment of the Cretaceous; therefore, it was not a concave boundary fault in the west of the Laiyang Sag, but an internal split fault, which cut the Laiyang Sag into two parts.

Tectonic characteristics and hydrocarbon accumulation in the eastern section of Maigaiti slope, Tarim Basin

Zhang Yuhang, Tang Liangjie

2017, 39(2): 222-229. doi: 10.11781/sysydz201702222

Abstract(936) PDF-CN(380)

Abstract:
Based on fault-related fold theory and the latest 3D seismic data, the tectonic deformation characteristics in the Yubei area on the eastern Maigaiti slope in the Tarim Basin were analyzed through seismic interpretation, and the relationship between tectonic characteristics and hydrocarbon accumulation was discussed. The study area featured vertically layered deformations. The pre-Cambrian basement developed normal faults and formed fault blocks. The Paleozoic developed slip-thrust faults along the Middle and Lower Cambrian gypsum rocks with a uniform slip surface, and the faults and folds were segmented horizontally. There are asymmetric (trishear) and symmetric (fan) folds in the Upper Paleozoic of the hanging wall, associated with fold-related fractures. Cenozoic did not develop faults or folds, and was represented by a west-tilting slope. Faults, tectonic fractures and unconformities constituted vertical and horizontal carrier systems for hydrocarbon migration in the Upper Paleozoic. The Upper Paleozoic kink bands extended reservoir space, and the associated structural fractures effectively improved reservoir performance. Influenced by the Late Hercynian and Himalayan tectonic movements, the intra-Ordovician karst reservoirs and the Upper Paleozoic fractured reservoirs are favorable accumulations of oil and gas.

Biomarker characteristics of Lower Paleozoic source rocks in Chezhen Sag, Bohai Bay Basin

Lin Hongmei

2017, 39(2): 230-237. doi: 10.11781/sysydz201702230

Abstract(1057) PDF-CN(255)

Abstract:
The biomarkers of the Lower Paleozoic carbonate rocks in the Chenzhen Sag of Bohai Bay Basin were stu-died using GS-MS. Their sedimentary environment, organic matter origin and thermal evolution degree were discussed, and compared them with the Eogene source rocks. The normal alkanes showed a single-peak distribution, with the main peak carbon varying between n-C₁₆ and n-C₁₈. Odd/even carbon number preference was not obvious, and Pr/Ph ratio ranged from 0.37 to 1.2, showing a weak phytane dominance or a balance between pristane and phytane. Hopane was the main terpane compound, with low tricyclic terpanes, high tetracyclic terpane, normal homohopane and low gammacerane contents. The C₂₇, C₂₈, C₂₉ regular steranes showed an asymmetrical "V" type distribution, with low rearranged sterane and high 4-methyl rearranged sterane contents. Phenanthrene and tris-fluorene series were the main aromatic compounds, lack of biphenyl and other higher plant imported biomarkers. The naphthalene series was abundant while 1,2,5-trimethylnaphthalene and 1,2,5,6-tetramethylnaphthalene had a low abundance. Dibenzothiophenes were rich and dibenzofurans were poor. Aromatic steranes were mainly triaryl steranes, and mono-aromatic steranes were absent. These biomarkers indicated that the Lower Paleozoic source rocks were deposited in a reductive shallow sea environment, mainly originated from fungus, algae and lower aquatic plankton, and were highly mature and over-mature. Four saturated hydrocarbon biomarkers and five aromatic hydrocarbon biomarkers were chosen to distinguish source rocks in the Lower Paleozoic and the Eogene, which provided evidence for oil and source correlation.

Jurassic reservoir development in Fukang Deep Sag, Central Junggar Basin

Shi Haoguo

2017, 39(2): 238-246. doi: 10.11781/sysydz201702238

Abstract(1424) PDF-CN(193)

Abstract:
Jurassic reservoirs were deeply buried in the Fukang Deep Sag, where faults are difficult to identify, and traps are subtle, leading to significant differences in reservoir-forming controls where they are dominated by large structural traps in the uplift zone. The process of oil and gas migration and accumulation and the main factors controlling hydrocarbon accumulation were analyzed based on the study of oil and gas source, migration pathway, migration agent and timing of reservoir development. Geological and geochemical analyses showed that oil and gas in the Fukang Deep Sag mainly came from coal-measure source rocks which were deposited in a freshwater environment in the Badaowan Formation. Combined with the analyses of abnormal pressure, oil and gas migration characteristics and reservoir-forming stages, it was deduced that, after discharge from the Badaowan Formation, oil and gas laterally migrated for a long distance in sand bodies of the Badaowan and Sangonghe formations, and then, through strike slip faults, vertically to traps in the Toutunhe Formation. The analyses of the main factors controlling hydrocarbon accumulation in the Fukang Deep Sag indicated that the formation of oil and gas reservoirs in the Toutunhe Formation was controlled by overpressure, fault, trap and the good matching of them. A reservoir development model of the study area was established.

Composition and geologic significance of carbon and oxygen isotopes in hydrocarbon source rocks, Dongying Sag, Bohai Bay Basin

Liu Qing

2017, 39(2): 247-252. doi: 10.11781/sysydz201702247

Abstract(1086) PDF-CN(262)

Abstract:
Lacustrine hydrocarbon source rocks of the Shahejie Formation in the Dongying Sag were sampled, and the carbon and oxygen isotope composition of carbonates were analyzed. Combined with previous references and precise stratigraphic division, the isotope composition in different stratigraphic units and the evolution of ancient lacustrine environment were discussed. The δ¹³C and δ¹⁸O of carbonates in the lower section of the fourth member of Shahejie Formation are positively correlated, which indicated that the basin was hydrologically closed during the initial period of rifting. But the carbon and oxygen isotopes are relatively light on the whole, which indicated that the water body of the salt lake was not stable, and was frequently influenced by fresh water. The δ¹³C and δ¹⁸O of carbonates in the upper section of the fourth member of Shahejie Formation are relatively heavy and positively correlated, which indicated that the salt lake was closed and stable during the acceleration phase of rifting. The carbon and oxygen isotopes of carbonate rocks with different lithologies in the lower section of the third member of Shahejie Formation varied. The δ¹³C and δ¹⁸O of non-calcium shale vary very little and are highly concentrated, which implied that the brackish lacustrine environment during peak rifting period was very stable and hydrologically closed. The middle and lower sections of the third member of Shahejie Formation have similar properties to the non-calcium shale, which suggested that the former may have inherited the isotope features of the latter.

Effects of inorganic minerals in source rocks on hydrocarbon generation from organic matter

Cai Yuwen, Zhang Shuichang, He Kun, Mi Jingkui, Zhang Wenlong, Wang Xiaomei, Wang Huajian, Wu Chaodong

2017, 39(2): 253-260. doi: 10.11781/sysydz201702253

Abstract(1017) PDF-CN(308)

Abstract:
The effects of inorganic minerals in source rocks on gas generation and isotopic fractionation of organic matter were studied by hydrous pyrolysis using two sets of whole rocks and their kerogens, which were separated from the low maturity shale of the Yanchang Formation in the Ordos Basin and the Xiamaling Formation in Huayuan area of North China. The liquid and gaseous hydrocarbon yields indicated that hydrous pyrolysis with whole source rocks were lower than those in pyrolysis of kerogen, but the amounts of CO₂ and H₂ in the former experiments were much higher, and the i-C₄/n-C₄ ratios in the whole rock hydrous pyrolysis were also lower. The results indicated that the presence of inorganic minerals in source rocks inhibited the interaction between water and organic matter, and the reaction mechanism between them also changed. Stable isotopic analyses revealed that little difference exists between the carbon isotopes of methane generated from two different types of hydrous pyrolysis, whereas the isotopic values of CO₂ were much more enriched due to the inorganic minerals present in source rocks, and the hydrogen isotopic values of gaseous hydrocarbons decrease significantly. These results demonstrated that inorganic minerals in source rocks have participated in and affected the isotopic compositions of hydrocarbon gases, and there exists indirect hydrogenation controlled by the presence of hydrogen.

Simulation of microseepage of light hydrocarbon of different occurrence states in strata above reservoirs

Wang Guojian, Tang Junhong, Tang Yuping, Li Xingqiang, Li Jipeng, Yang Jun, Huang Xin

2017, 39(2): 261-266. doi: 10.11781/sysydz201702261

Abstract(816) PDF-CN(145)

Abstract:
Several geochemical methods to analyze light hydrocarbons in subsurface rock and soil microseeping from hydrocarbon reservoirs were set up. The hydrocarbons included adsorbed and thermally-released hydrocarbon, head space gas, and free gas, etc., but the static data analyzed through these methods could not accurately describe the occurrence states and features of microseeping hydrocarbons in the overlying strata and soil. Most past studies on the occurrence mechanism of microseeping hydrocarbons were limited to a theoretical level, and lacked the support of reliable simulation, resulting in different understandings of the application of the light hydrocarbon indexes and the independence among them, which affected the interpretation of geochemical anomalies and proper application of the methods. An experiment was conducted to simulate hydrocarbon vertical microseepage through cap rocks and overlying strata based on a simplified theoretical model of hydrocarbon microseepage. The cylinder was dissected to recover subsamples after the experiment. According to the test results of gas and rock samples, the occurrence mechanisms of free gas, head space gas, thermally-released hydrocarbon, and adsorbed hydrocarbon in the strata overlying a reservoir were studied. The results showed that the free gas indicators were best in reflecting the present features of vertical microseepage, and the adsorbed hydrocarbon indicators were not affected by gas vertical migration in the short term, whereas the thermally-released hydrocarbon indicators and the head space gas indicators were affected by gas micro-migration, with the latter being most significantly affected. Because the occurrence mechanisms and the influence factors of these hydrocarbons in rock and soil are different, the characteristics of hydrocarbon microseepage can be reflected by using these light hydrocarbon indicators from different aspects. These experiment results can help geochemical explorers deepen the understanding of different types of light hydrocarbon indicators, and to explain the geological significance of geochemical anomalies better.

Comprehensive analysis methods in a mature exploration area: Jiyang Depression case study

Guo Yuanling, Du Zhenjing, Fang Xuqing, Hou Fei, Dong Weiwu

2017, 39(2): 267-271. doi: 10.11781/sysydz201702267

Abstract(1239) PDF-CN(295)

Abstract:
Contents and methods of comprehensive analysis of the Jiyang Depression were introduced. We divided exploration units, established exploration models, made clear exploration purpose and direction, assessed exploration risks, estimated economic value and investment scale, and finally proposed some advice for optimization. The analysis of exploration operation regularity may help grasp the characteristics and emphasis of exploration, improve the adaptability of exploration theory and technology, and improve exploration efficiency. Exploration comprehensive analysis would communicate theory study and management, help researchers keep abreast of macro-dynamic conditions, and improve management.

Depositional facies mapping based on seismic data: A case study of the 8th member of Shihezi Formation, Gaojiahe 3D block, Yanchang exploration zone, Ordos Basin

Lai Shenghua, Liu Weiming, Zhao Yonggang, Ding Xi

2017, 39(2): 272-277. doi: 10.11781/sysydz201702272

Abstract(900) PDF-CN(244)

Abstract:
Seismic data were applied in the study of sedimentary facies distributions in the 8th member of Shihezi Formation in Gaojiahe 3D block in Yanchang exploration area, the Ordos Basin. Rock properties are the basis for the application of seismic data in sedimentological interpretation. The seismic reflection frequency in sand layers was analyzed using a time-frequency technique and based on 90° phase seismic data body. Seismic wave interfe-rence in sand layers was reduced using filtering techniques. Combining geological, well logging and seismic data, a sedimentological interpretation of strata slices with different principal frequencies was made, which helped improve the accuracy of sedimentary facies prediction. The 8th member of Shihezi Formation is mainly delta front subfacies arising from two large rivers. One underwater distributary channel goes from southeast to northwest along wells S228, S232, S204, S205, Yq2 and S216, and the other goes from east to west along wells Y218, S222, Y120 and S226. The gamma curves of sand bodies in these underwater distributary channels are bell-shaped, dentate-like or box-shaped, and are shown in the stratigraphic section as a medium-strong energy band reflection pattern. In addition, a smaller-scale underwater distributary channel was found along wells S212, Y217, S211, S210, S246 and S247 on the western margin of the study area, and featured a medium to weak energy worm-like and small patch seismic reflection pattern on a stratigraphic section.

Quantitative characterization of extractable organic matter in lacustrine shale with different occurrences

Qian Menhui, Jiang Qigui, Li Maowen, Li Zhiming, Liu Peng, Ma Yuanyan, Cao Tingting

2017, 39(2): 278-286. doi: 10.11781/sysydz201702278

Abstract(1385) PDF-CN(336)

Abstract:
The extractable organic matter (OM) in lacustrine shale can be classified into free, adsorbed or miscible states. The quantitative study of OM of these different occurrences has significance for oil/gas resource evaluation, shale oil mobility, hydrocarbon generation mechanism and oil/gas occurrence. Two lacustrine shale samples of different lithofacies from East China were successively extracted by solvents with different polarities. Three different occurrence states of soluble OM were obtained, including free, kerogen adsorptive-miscible and mineral surface adsorptive states, which were characterized using FT-IR spectra and GC-FID analyses. The kerogen adsorptive-miscible state accounts for a large proportion of the soluble OM, followed by the free OM. The free soluble OM was dominated by light compounds, and fracturing was conducive to the precipitation of light components. The kerogen adsorptive-miscible state OM mainly had heavier components, and also contained a lower portion of light fractions. The mineral surface adsorbed OM was mainly comprised of oxygen-containing compounds. Compared to the massive shale samples, the laminated shale samples had a higher proportion of soluble OM, and the hydrocarbon molecules were smaller.

Reservoir characterization and its application to development

Zhao Xi, Liu Bo, Guo Rongtao, Zhang Shanming, Li Yang, Tian Zepu

2017, 39(2): 287-294. doi: 10.11781/sysydz201702287

Abstract(1398) PDF-CN(614)

Abstract:
Recently, the exploration and development of unconventional oil and gas resources have obtained a great breakthrough, which expanded research and promoted the technique innovation of reservoir study. Consequently, from conventional-scale to nano-scale pores, low to extra-low porosity and permeability, the understanding of reservoir pore structure, porosity and permeability continues to deepen. Various reservoir characterizations were introduced and compared. On the basis of pore structure and porosity-permeability characteristics, reservoirs were classified into four kinds: macro to medium-pore and high permeability reservoirs, micro-pore and low permeability reservoirs, nano-pore and ultra-low permeability reservoirs, and compound pore reservoirs. The advantages, disadvantages and applications of each characterization method were discussed, and some combined methods applicable to different types of reservoirs were also presented. A divisional-layered characterization technique was put forward to deal with compound pore reservoirs. In addition, the application in pore genesis, filling material, and surface structure of internal walls of pore were discussed. Thus, the research on reservoir extended from the structure level to the genesis level, providing references for more comprehensive understanding.

Peng Shoutao

2017, 39(2): 295-295.

Abstract(346) PDF-CN(203)

Abstract:

2017 Vol. 39, No. 2

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