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2013 Vol. 35, No. 6

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2013, 35(6)
Abstract(408) PDF-CN(686)
Abstract:
Research progress, existing problem and development trend of tight rock oil
Wang Zhenliang
2013, 35(6): 587-595. doi: 10.11781/sysydz201306587
Abstract(1108) PDF-CN(1931)
Abstract:
Tight rock oil is a more realistic exploration domain of oil fields to succeed. The difficulties in tight rock oil research include the impact of tight process and different porosity classes on petroleum migration, whether petroleum has been transported or not, and whether all the reservoirs are continuous. In recent years, the main geologic features of domestic tight rock oil has been concluded, a preliminary discussion of the generation, distribution and accumulation of tight rock oil has been carried out, and an observation and measurement technique of nano-class pores has been established gradually. By contrast, the overseas researchers suggest that the fluid flow in tight rocks is controlled by the distribution of dominant pore-throat size. The networks of mesopores are observed to connect with large macropores within organic matter, which would obviously increase permeability in tight rocks. The obvious lateral migration of tight rock oil may take place during enrichment process. The model of continuous hydrocarbon accumulation could not evaluate accurately the resource potential in both the Williston Basin and the Greater Green River Basin. In near future, three crucial scientific problems should be focused on: rock tightening process and the relative distribution of miro- and nano- pore and throat structure, the occurrence state and migration and accumulation mechanisms of tight rock oil, as well as the evaluating indictors of resource potential of Chinese tight rock oil.
Geologic analysis of Middle-Lower Jurassic shale reservoirs in Yuanba area, northeastern Sichuan Basin
Zhou Dehua, Jiao Fangzheng, Guo Xusheng, Guo Tonglou, Wei Zhihong
2013, 35(6): 596-600. doi: 10.11781/sysydz201306596
Abstract(1236) PDF-CN(1220)
Abstract:
Integrating with drillings, cores, outcrops and logging data, we made a comprehensive geologic analysis of the Middle-Lower Jurassic shale reservoirs in the Yuanba area of the northeastern Sichuan Basin, from the aspects such as organic-rich shale distribution, geochemical characterization, mineral composition, hydrocarbon store space property, shale porosity and permeability condition, and geomechanical nature. The organic-rich shales mainly generated from the Daanzhai member of the Ziliujing Formation to the 1st and 2nd members of the Qianfoya Formation. They are shallow to semi-deep lacustrine facies, and mainly consist of dark shales with limes and sand stones. Organic matters are rich, and of type Ⅱ2. The average TOC content is 1.14%. The vitrinite reflectance (Ro) ranges from 1.4% to 1.6%, indicating for the mature and high-mature stages of condensate oil and wet gas. Generally, the Middle-Lower Jurassic shales have simple and stable structure with few fractures developed, hence are favorable for hydrocarbon generation and preservation. The lacustrine facies shales in the Daanzhai member are similar to the Eagle Ford shales in the North America in general. The dark shales in the Daanzhai member are 40-115 m thick with various pore types. Horizontal and micro fractures are well-developed. The average brittle mineral content, Young’s modulus and Poisson ratio are 52.7%, 37 GPa and 0.30, respectively, all contributing to the formation of fracture network.
Gas-bearing influential factors and evaluation of shale gas reservoir: A case study of Paleozoic shale gas reservoir in Upper Yangtze region
Guo Shaobin, Huang Lei
2013, 35(6): 601-606. doi: 10.11781/sysydz201306601
Abstract(901) PDF-CN(1018)
Abstract:
Shale gas reservoirs are self-generated and self-contained, and gas-bearing property should be focused on during reservoir evaluation. Based on test data of core samples from 7 wells of Paleozoic in the Upper Yangtze Platform, beginning with gas content, the influential factors for gas-bearing property were discussed, including TOC, Ro, porosity, isothermal adsorption data, illite/ smectite formation content and movable fluid percentage. It was discovered that taking 0.5 m3/t as the boundary between reservoir and non-reservoir was practicable, and each parameter appears its relationship to total gas content. Based on grey relational theory, reservoir evaluation was performed. Referring to previous results and empirical data, reservoir evaluation scheme and space image characteristics were accomplished.
Discussions on Carboniferous stratigraphy of Bachu uplift, Tarim Basin
Huang Taizhu, Cai Xiyao, Guo Shuyuan
2013, 35(6): 607-614. doi: 10.11781/sysydz201306607
Abstract(839) PDF-CN(967)
Abstract:
Based on the comprehensive analysis of drilling data, the Carboniferous stratigraphy of the Bachu uplift in the Tarim Basin was discussed. Four new stratigraphic sequences were found, the original definitions of the Bachu and Kalashayi Formations were restored, and the Mazatage Formation was established. It was confirmed that the Bachu Movement took place at the end of the Early Carboniferous, and the movement was severe in the west and weak in the east of the Tarim Basin. In the east of the Bachu uplift, sandstones and mudstones lay on the upper mudstones with an angle unconformity. In the west of the uplift, the Xiaohaizi Formation lay on the middle mudstones or the bioclast limestones. From the west of the uplift to the Keping area, the Kangkelin Formation lay on the Sishichang Formation, and the Bachu and Mazatage Formations were eroded. Triticites belt and the strata of Xiaoyiaoan Stage developed in the Xiaohaizi Formation in the west of the Bachu uplift and disappeared in the east. A classification standard of lithologic and logging characteristics was founded between the Xiaohaizi Formation and the overlying Nanzha Formation of the Lower Permian. The S.suberectus-S. parvus-G. bella and Triticites belts developed in the Xiaohaizi Formation while the S. isolatus, S. whitei-N. pequopensis and Pseudoschwagerina belts developed in the Nanzha Formation. The discontinuity between the two formations gradually reduced from east to west in the Bachu uplift, and disappeared (with conformity) in the western edge of the uplift.
Characteristics and main controlling factors of tight sandstone reservoirs in Silurian of Kongquehe slope, Tarim Basin
Wang Bin, Zhao Yongqiang, Wang Shuyi, Zhang Genfa, Luo Yu, Chen Xuyun, Lei lei
2013, 35(6): 615-620. doi: 10.11781/sysydz201306615
Abstract(842) PDF-CN(889)
Abstract:
The sandstone reservoir characteristics such as clastic component, sedimentation, diagenesis and so on in the Silurian of Kongquehe slope were analyzed based on the data of core, casting film, electron microscope scanning and reservoir property analysis to determine the main controlling factors of reservoir quality. The research result shows that reservoir lithology is mainly lithic sandstone and feldspathic litharenite, which have medium texture maturity and lower maturity composition. Reservoir accumulation properties are worse, which belong to low-porosity and extra-low-permeability tight sandstone reservoirs. Main reservoir space is corrosion pore between grains or in grains and a few micro-fractures. The connectivity between pore space and throat is poor. Sedimentation is the fundamental factor for the development of sandstone reservoirs in Silurian. Strong compaction and widespread cementation are the dominant factors. Structure fracturing and dissolution are also important factors for the formation of secondary pores in sandstone reservoirs.
Oil accumulation related to migration of source kitchens in northwestern margin structural belt, Junggar Basin
Liu Bo, Liu Dingyong, Guo Tianxu, Huang Zhilong, Liu Zhenyu, Wu Fan
2013, 35(6): 621-625. doi: 10.11781/sysydz201306621
Abstract(953) PDF-CN(728)
Abstract:
According to the analyses of hydrocarbon-source correlation, hydrocarbon accumulation periods and source kitchen migration, the present hydrocarbon distributions in the northwestern margin of the Junggar Basin are controlled by three sets of source kitchen migration. The natural gas which generated during the early stage from source kitchens in the Jiamuhe Formation has not been preserved, and the present location of source kitchens controls reservoir distribution. The source kitchens in Fengcheng Formation at the centre of the Mahu Sag can not generate gas since they are over-matured. Only the source kitchens at the margin of the sag can generate hydrocarbon and control the location of oils generated from them. The source kitchens in Wuerhe Formation can still generate oil and gas in the center of the sag and also control the location of oil generated from them. Because of the different hydrocarbon-generation intensity for the same source kitchen during different geological periods and different source kitchens at the same geological period, different hydrocarbon supply modes develop and control the location of hydrocarbon in the northwestern margin of Junggar Basin.
Gravity flow and internal wave and internal tide deposits in Upper Miocene of SE area, Yinggehai Basin
Yang Hongjun, Guo Shusheng, Liu Bo, Lu Qingzhi, Tong Yanming
2013, 35(6): 626-633. doi: 10.11781/sysydz201306626
Abstract(928) PDF-CN(692)
Abstract:
Integrated with cores, micro-resistivity images and conventional logs, deposits in the 1st member of the Huangliu Formation of the Upper Miocene in the SY and SE areas in the Dongfang tectonic belt of the Yinggehai Basin were analyzed in detail. It was shown that a set of fine-grained deposits of submarine fan developed in the 1st member of the Huangliu Formation, and the deposits were reformed by internal wave and internal tide of deep-water tract current during gravity flow deposition process, forming 5 typical lithofacies: 1) fine-grained sandstone with bidirectional sand ripple; 2) laminated sand and shale with flaser, wavy and lenticular bedding; 3) fine-grained sandstone with double mud layers or mud stripe; 4) Massive and graded fine-grained sandstone; 5) fine sandstone with floating mud clasts or mud debris. The 1st member of the Huangliu Formation in the SE area was mainly gravity flow deposits and partially internal wave and internal tide deposits, and the 2 kinds of deposits coupled locally.
Impact of CO2 on formation and distribution of gas hydrate in northern South China Sea
Jin Xiaohui, Lin Qing, Fu Ning, Huang Xia, Zhu Youhai
2013, 35(6): 634-639. doi: 10.11781/sysydz201306634
Abstract(1362) PDF-CN(1040)
Abstract:
In the northern South China Sea, non-hydrocarbon gases such as CO2 are abundant, which are both constructive and destructive for gas hydrates. When the natural gases containing CO2 leak upward to shallow formations, CO2 could be reduced to CH4 as carbon source under appropriate conditions, forming gas hydrates within shallow sediments. The experiments of gas samples with different CO2 and N2 contents have indicated that the temperature for gas hydrate formation of CO2-bearing gases is higher than that of CH4-bearing gases, resulting in deeper occurrence of hydrates and bigger thickness of hydrate stale zones. If strong seepage happened, natural gases with higher CO2 content would migrate upward to CH4 hydrate zone through deep faults. The replacement process of CH4 by CO2 will start. The previous gas hydrates will be damaged or the saturation of CH4 will decline.
Petrography and diagenesis of Permian sandstone reservoirs in Zhoukou Depression, Southern North China Basin
Li Ying, Ma Mingyong
2013, 35(6): 640-645. doi: 10.11781/sysydz201306640
Abstract(983) PDF-CN(1089)
Abstract:
The petrography and diagenesis of the Permian tight sandstone reservoirs in the Zhoukou Depression of the Southern North China Basin were studied using sedimentology, petrology and petroleum geology based on field outcrops, drilling cores observations and laboratory experiments. The main contributive sandstone reservoirs include the Hushi sandstones in the Taiyuan Formation, the Dazhan sandstones in the Shanxi Formation, the Shaguoyao sandstones in the Lower Shihezi Formation, the Tianjiagou sandstones in the Upper Shihezi Formation and the Pingdingshan sandstones in the Sunjiagou Formation. In the sandstones, quartz content is relatively higher. There are larger pores among quartz particles. But many pores disappeared and even the particles were broken because of pressure. Feldspar content is lower and most of which is potash one. The interstitial materials are mainly muddy, siliceous, calcareous and chlorite. Four types of diagenesis can be found, which include compaction-pressolution, cementation, dissolution and metasomatism. Many diagenesis indexes were studied in detail in order to con firm diagenetic stages, which is in the stage B of the middle diagenesis phase or the late diagenesis phase.
Carboniferous-Permian coal-bearing depositional system and its controlling role of coalbed methane in Hancheng area in Ordos Basin
Wang Xiaohong, Liu Dameng, Yao Yanbin, Xie Chen
2013, 35(6): 646-650. doi: 10.11781/sysydz201306646
Abstract(971) PDF-CN(1252)
Abstract:
The geological conditions for coalbed methane are complicated in Hancheng area of the Ordos Basin. The characteristics of coal-bearing depositional system work as the main controlling factor for the enrichment of coalbed methane. According to the features of coal-bearing sediments in Carboniferous and Permian in Hancheng area, the Taiyuan Formation constitutes of lagoon-tidal-barrier island sedimentation and carbonate flat sedimentation while the Shanxi Formation constitutes of fluvial-dominated delta sedimentation. The changes of sedimentation, the thickness of coalbed, the petrophysical property and the lithology of roof and floor of coalbed are directly concerned to analyze the influence of sedimentary environment on CBM enrichment. The coalbed no.3 is thin and even pinches out locally. The coalbed no.5, which is thick and stable, is widespread in the study area. The roof and floor of coalbed are mainly mudstone, sandstone and siltstone. The coalbed with stable structure and thick mudstone as roof and floor is favorable for the enrichment and accumulation of coalbed methane. The area to the east of Baimatan town is the exploration target for 2 sets of coalbed.
Spectral decomposition characteristics of reef-bank reservoirs of Changxing Formation in Yuanba area, northeastern Sichuan Basin
Xu Yongzhe, Wang Yuhua, Chen Lei, Lu Yongchao
2013, 35(6): 651-656. doi: 10.11781/sysydz201306651
Abstract(976) PDF-CN(895)
Abstract:
In Yuanba area of the northeastern Sichuan Basin, the reef-bank in the Permian Changxing Formation is characterized by deep burial depth and great lateral variation, hence is difficult to predict by conventional method. Based on well-seismic calibration and spectral decomposition of short windowed discrete Fourier transform, the frequency range of different facies is figured out. The form and plane distribution of platform margin reef complex changing with frequency are described. The boundary of lithologic reservoir is confirmed, providing scientific guiding for petroleum exploration.
Characteristics of high-energy channel sandstone and its exploration significance: A case from Xujiahe Formation in Yuanba area
Wang Wei
2013, 35(6): 657-661. doi: 10.11781/sysydz201306657
Abstract(773) PDF-CN(856)
Abstract:
The calcarenaceous sandstone reservoirs in the 3rd member of the Xujiahe Formation in the Yuanba area are lithologic ones featured by source and reservoir coexistence, high migration efficiency, favorable accumulation condition and overall gas-bearing capacity. Reservoirs mainly develop in the high-energy channel sandstones of braided river delta. The calcarenaceous high-energy channel sandstones in the 3rd member of the Xujiahe Formation in the northwestern Yuanba area are characterized by low GR (smooth box-like or toothed box-like gamma curves), high resistance, high carbonate debris content, low quartz content, and wide spread of dissolution pores and cracks. The big thickness of calcarenaceous high-energy channel sandstones provides the basement for the enrichment of natural gas in the 3rd member of the Xujiahe Formation. Near source, high carbonate debris content, high compression strength and high dissolution degree are the keys for the enrichment of natural gas in the 3rd member of the Xujiahe Formation. The explorations of calcarenaceous sandstone reservoirs in the 3rd member of the Xujiahe Formation should be focused on the near-source and high-energy channel sandstones with thick calcareous debris sandstone, high calcareous content and low quartz content.
Correlation of major source rocks and oil sources in Lishu Fault Depression
Gu Yi, Qin Du, Lu Qinghua, Li Kuang, Song Zhenxiang, Huang Dangwei
2013, 35(6): 662-667. doi: 10.11781/sysydz201306662
Abstract(860) PDF-CN(1056)
Abstract:
According to the geochemical features of source rocks and crude oils from different strata and different area in the Lishu Fault Depression, the main source rock features and crude oil geochemical characteristics have been concluded. The analyses of biomarker compound and carbon isotope show that crude oils in the Lishu Fault Depression mainly generated from parent materials of type Ⅱ1, while in Sujiatun area some crude oils which generated from parent materials of type Ⅲ mixed in. Oil and source correlation proves that crude oils in the Lishu Fault Depression mainly generated from the Shahezi Formation, while the 1st member of Yingcheng Formation also contributed in some area.
Characteristics and maturity evolution history of Silurian hot shales in Rub Al Khali Basin
Zheng Lei, Jin Zhijun, Zhou Jin
2013, 35(6): 668-675. doi: 10.11781/sysydz201306668
Abstract(1057) PDF-CN(890)
Abstract:
The geological conditions of hot shales at the bottom of Silurian in the Rub Al Khali Basin were studied based on well drilling data. The w(TOC) test, pyrolysis analysis and Ro test of core and cutting samples were made, indicating that the hot shales are in the mature-high-mature and even over-mature stages. Through the carbon isotopic analyses of kerogen, bitumen “A” and group composition, organic type was confirmed as type II. By means of PetroMod Basin simulation software, the burial history, thermal history and maturity history of 3 wells were simulated. The maturity history of hot shales in contract blocks was simulated as well. The simulation results can be concluded that the forming age of Silurian hot shales in the Rub Al Khali Basin becomes later from the deep sag to the eastern slope, and the hot shales in the deep sag have entered into mature period since the Early Permian; however, the hot shales on the eastern slope became mature from the end of the Early Permian to the end of the Late Jurassic.
Organic geochemical characteristics of source rocks in Wuyu Basin, Tibet
Yi Li, Li Yalin, Wang Chengshan, Ma Pengfei, Zhang Hailong, Zhang Xiaolong
2013, 35(6): 676-682. doi: 10.11781/sysydz201306676
Abstract(982) PDF-CN(984)
Abstract:
The Wuyu Basin is a Cenozoic intermontane basin in the Tibetan Plateau. Since Oligocene, it has been deposited in the basin from base to top the formations as followed: the Oligocene Rigongla Formation, the Miocene Mangxiang Formation, the Pliocene Gazhacun Formation and the Pliocene Zongdangcun Formation. Dark source rocks have been found during field explorations in these strata. Geochemical studies have indicated that source rocks from the Mangxiang Formation are featured by good organic type, high abundance and superior hydrocarbon generation potential. They are during the peak period of hydrocarbon generation. The nC21-/nC22+ value is 1.2 in average, showing the lower aquatic organism sources for organic matters. The Pr/ Ph value is 1.2 in average, showing the deep or semi-deep lacustrine weak reduction environment for organic matter deposition. The average value of γ-acerance index has reached 3.32, indicating the stratification pattern and high salinity situation of water during deposition, which are favorable for organic matter preservation. The Mangxiang source rocks are the major source rocks in the Wuyu Basin. Coal samples from the Mangxiang Formation are good gas source rocks which have reached the mature stage and are abundant in organic materials, type III primarily.
Geochemical features and sources of crude oils in Bachu-Maigaiti area
Ding Yong, Jia Cunshan, Shao Zhibing
2013, 35(6): 683-688. doi: 10.11781/sysydz201306683
Abstract(973) PDF-CN(847)
Abstract:
 Bachu-Maigaiti area is an important focus area of oil and gas. In the Ordovician Yingshan Formation in well Yubei 1, industrial oil and gas flows of marine facies have been tested for 25.2 m3/d. It is urgent to solve the problem whether the crude oils from Ordovician of Yubei area and Bashituo oil field are of the same sources. Through the geochemical analysis, oil/ oil and oil/ source correlations of the crude oils from well Yubei 1 and Bashituo oil field, compared with the Ordovician crude oils from Tahe area, the geochemical characteristics of crude oil and oil source of the main oil-and-gas reservoirs in Bachu-Maigaiti area are discussed. The geochemical features of the Ordovician crude oils from Yubei area are similar to those of the Ordovician crude oils from Tahe area. According to the organic analogy of oil source, the Ordovician crude oils from Yubei area may originate from the Middle and Lower Ordovician source rocks of slope facies in the southwestern Tahe area. The light oils from Bashituo area mainly come from the Cambrian source rocks of basin-shelf facies, and partially from the Carboniferous source rocks of marine-terrigenous facies.
Shale research progress and achievements in seal appraisal technology
Qin Jianzhong, Liu Weixin, Fan Ming, Zhang Wengtao, Yu Lingjie
2013, 35(6): 689-693. doi: 10.11781/sysydz201306689
Abstract(883) PDF-CN(1102)
Abstract:
Shales form a large proportion of sedimentary basin fill worldwide and they have not been studied in great detail to date due to the lack of preserved specimens, clay mineral dilation and shrinkage, small granular, timing taken to perform tests. Understanding shale behavior is critical to a range of issues confronting petroleum industry, such as wellbore stability, top seal, predicting overpressure for low-permeability shale, understanding the effects of anisotropy on depth conversion, shale mechanics and petrophysical response on logs. It is also necessary for the exploration of shale gas. A series of progress has been made in shale research and seal appraisal at home and abroad.
One kind of brittle shale characterization method and its geological significance
Bao Yunjie, Yang Zhenheng, Yang Qi, Chen Hongyu, Fu Xiaodong, Wang Jie
2013, 35(6): 694-697. doi: 10.11781/sysydz201306694
Abstract(842) PDF-CN(864)
Abstract:
The paper presents one kind of brittle shale characterization method: brittle index, and introduces the determination process and procedure for the index. This method is simple to operate, and has no special requirements for sample size and shape, hence has universal significance for shale sample test. Experimental data show that the brittle index is positively correlated to porosity and specific surface area. According to measurement process, method, experimental data and literature analysis, the brittle index can characterize the extent and internal structure of porosity, especially the potential application for micro pores and cracks. The prospects for the application of brittle index in the studies of shale internal structure and gas desorption are discussed preliminarily.
Laboratory experimental research on waterflooding sweep efficiency of large-scale and two-dimensional inter-layer heterogeneous physical model
Wang Ming, Du Li, Guo Dianbin, Li Zhongchao, Nie Fajian
2013, 35(6): 698-701. doi: 10.11781/sysydz201306698
Abstract(1080) PDF-CN(799)
Abstract:
In order to recognize the dynamic sweep process of heterogeneous reservoir in water injection development, a large-scale, two-dimensional heterogeneous physical model was made for the first time on the basis of Zhongyuan Oil Field. Through the three-dimensional physical simulation experiment in laboratory, the quantitative research on the variation characteristics of oil saturation and sweep efficiency of the geological model of positive rhythm and high water-cut reservoir under different injection volume and displacement pressure was made. The results showed that there were obvious differences among the three layers’ producing degree of the heterogeneity model and there was a positive correlation between producing degree and reservoir permeability. When the injection volume was raised from 0.10 HCPV to 1.15 HCPV, the sweep efficiency increased from 36.73% to 100% in high permeability layer, from 24.49% to 76.60% in middle permeability layer, and from 14.24% to 44.90% in low permeability layer. When the displacement pressure difference was raised, the recovery percentage of low permeability layer was significantly higher than that of high permeability. Through hierarchical ordering measures, the recovery percentage of middle permeability layer and low permeability layer can be increased, and the interlayer adjustment is an effective measure for improving the development result of heterogeneous reservoir.
Forecasting methods of SEC reserves replacement rate
Wei Ping, Zhang Ling, Zhai Zhongxi, Xiao Xizhen, Guo Mingli
2013, 35(6): 702-706. doi: 10.11781/sysydz201306702
Abstract(1341) PDF-CN(1483)
Abstract:
 The reserve replacement rate is an important reflection of the management state of oil companies, especially in sustainable development. It is also an important indicator for oil companies to make annual plan and an important basis for branch company assessment. Because of many uncertain factors, it is very difficult to predict the reserve replacement rate. The connotation and characteristics of the SEC reserve replacement rate have been introduced in this paper, through forecasting three parts of the reserves, which include the annual “boundary extending and new discovery of new reserves”, “increasing recoverable reserves” and “correction” reserves. Then the SEC reserve replacement rate has been predicated. The method is simple and easy to operate. It has been applied in some oilfield to predict the SEC reserve replacement rate for the year 2011. Four main affecting factors for SEC reserves replacement rate have been discussed.

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