石油实验地质

2013, 35(1)

Abstract(1129) PDF-CN(885)

Abstract:

Geological characteristics of superposed tight sandstone gas-bearing areas in western Sichuan

Yang Keming, Zhu Hongquan

2013, 35(1): 1-8. doi: 10.11781/sysydz201301001

Abstract(1794) PDF-CN(1123)

Abstract:
Based on the geologic background, reservoir forming features and reservoir characteristics of tight sandstone gas reservoirs in the western Sichuan, the concept of superposed tight sandstone gas-bearing areas has been proposed. The superposed tight sandstone gas-bearing areas in the western Sichuan have the characteristics of superimposition, extensive spread ability, rhythmicity, ambiguity and diversity. Superimposition refers to the superimposed properties of prototype basin, tectonic deformation, reservoir stratum and reservoir forming assemblage. Extensive spread ability refers to the wide distribution features of source rock, reservoir stratum, trap and gas reservoir. Rhythmicity refers to the rhythm properties of structural evolution, sedimentary evolution, migration and infilling. Ambiguity refers to the fuzzy properties of gas-water boundary, trap types and the heterogeneity of reservoir. Diversity refers to the variety of source rocks, reservoir types, migration patterns and gas reservoir types. Generally speaking, the superposed tight sandstone gas-bearing areas in the western Sichuan have the three-elements (source, facies, position) reservoir-controlling characteristics.

Risk analysis and play evaluation of marine residual basins in South China

Xu Zhengyu, Yao Genshun, Huang Ling, Dong Yong, Wang Pengwan, Yu Guang

2013, 35(1): 9-16. doi: 10.11781/sysydz201301009

Abstract(2085) PDF-CN(963)

Abstract:
Multiple cycles of hydrocarbon generation, reserve and cap assemblages with sea at the bottom and continent at the top developed in South China. There were mainly 2 sets of marine accumulation assemblages including Sinian-the Lower Paleozoic and the Middle-Upper Paleozoic. On plane map, the study area was divided into 2 accumulation zones (the southern one and the northern one) by the Jiangshao-Shiwandashan Fault. In the northern accumulation zone, 2 sets of accumulation assemblages developed, while in the southern accumulation zone, only the Middle-Upper Paleozoic assemblage existed. The distribution of ancient reservoirs and oil-and-gas shows was controlled by ancient uplifts. Petroleum accumulation experienced over 3 stages of tectonic events, for example, oil generating in Caledonian-Hercynian stages, oil cracking to gas in Indosinian stage, and adjusting and deforming in Yanshanian-Himalayan stages. The present marine reservoirs in South China have distinctive residual features. Their exploration degrees are low, techniques are not mature, and the knowledge about accumulation rules is restricted. The risks are higher for normal petroleum explorations, lower for marine superimposed basin explorations, and the lowest for unconventional shale gas explorations. The marine strata in South China were evaluated and the favorable zones for exploration were pointed out.

Characteristics of multiple-circular slope break geomorphology and its controlling on sedimentary process in Changling Sag, Songliao Basin

Hu Chunxin, Yang Shuai, Lu Yongchao, Du Xuebin

2013, 35(1): 17-23. doi: 10.11781/sysydz201301017

Abstract(1906) PDF-CN(1290)

Abstract:
By means of high-resolution sequence stratigraphy, tectonic stratigraphy, fine sedimentary system analysis and tectonic-palaeogeomorphology recovery, the formation feature and process of the Changling Sag during depressive stage were studied systematically. It was concluded that during the depressive stage, the sag was both uplifted and depressive controlled by multiple circles of slope-break belts. The slope-break belts not only divided geographic units, but also controlled the changes of sedimentary facies, resulting in the close coupling relationship between palaeogeomorphology and sedimentary system distribution. Furthermore, 4 favorable exploration regions in the study area were proposed, including the plain lithofacies of uplift belt, the proximal delta front of slope belt, the proximal delta front of deep depression, and the far delta front of deep depression.

Hydrocarbon accumulation features and exploration potentials in Anshun Sag, Southern Guizhou Depression

Bai Senshu, Peng Jinning, Liu Guangxiang, Wang Yanqing

2013, 35(1): 24-28. doi: 10.11781/sysydz201301024

Abstract(1723) PDF-CN(1347)

Abstract:
The potential petroleum accumulation types, features and forecasts of the Anshun Sag in the Southern Guizhou Depression have been discussed based on seismic interpretations and previous studies. In the lower formations of the sag, "Majiang paleo-reservoirs" have been found. In the upper formation, there exist "reef-flat" and "unconformity surface or regolith" reservoirs. Meanwhile, source rocks are well-developed and the sag is the long-term target zone for hydrocarbon migration. Good cap rocks provide good regional hydrocarbon preservation conditions. The Puding synclinorium is the most favorable exploration target in the Anshun Sag.

Characteristics and main controlling factors of fractures in gas reservoir of Xujiahe Formation, Dayi Structure

Chen Yingbin, Zheng Bing, Yuan Dongshan, Hu Ye, Wang Yanqing

2013, 35(1): 29-35. doi: 10.11781/sysydz201301029

Abstract(1886) PDF-CN(1160)

Abstract:
The gas reservoir of the Xujiahe Formation in the Dayi Structure is a fractured reservoir. The generation degree of fracture is the key factor for natural gas enrichment and high productivity. According to the core and logging data from 14 wells, combined with structural and sedimentary facies analyses as well as ancient tectonic stress field simulation, it has been concluded that 3 genetic types of fractures exist in the study area, including structural fracture, stratification fracture and abnormal pressure blowdown fracture. Structural and stratification fractures are relatively more effective; however, they are usually in smaller amount, and extend for short distance and narrow width. They are filled for higher degree and have stronger heterogeneity. Small formation stress and weak deformation are the primary causes for the poor development of structural fractures. Induced feather fractures during the Himalayan period control the formation and distribution of structural fractures. Parallel beddings and inclined beddings which develop in the distributary channels of delta plains and delta fronts are the main bedding types for stratification fracture formation. The genetic types of fractures, filling characteristics, later denudation and current ground stress field control the effectiveness of fractures.

Sedimentary environment and its controlling on source rocks during late Permian in Sichuan Basin

Cao Qinggu, Liu Guangxiang, Zhang Changjiang, Pan Wenlei

2013, 35(1): 36-41. doi: 10.11781/sysydz201301036

Abstract(1986) PDF-CN(1239)

Abstract:
As the most important source rock for gas generation in the Sichuan Basin, Permian source rocks have attracted more and more attentions. The lithofacies palaeogeography during the Longtan phase of the Late Permian in the Sichuan Basin was reconstructed, and the controlling effects of sedimentary environment on source rock generation were analyzed. In the Upper Permian of the Sichuan Basin, favorable source rocks mainly developed in the shallow shelf, tidal flat-lagoon and onshore swamp facies. The concept of "organic carbon thickness" was introduced in this article. Organic carbon content was multiplied by source rock thickness so as to illustrate the generation features of source rocks. Combined with inorganic geochemical characteristics and organic carbon analyses, the controlling effects of sedimentary environment on source rock generation were studied, providing theoretical reference for the macroscopic distribution prediction of source rocks and resource estimation.

Evolution of Paleogene saline deposits and effectiveness of traps in Kelasu tectonic zone, Kuqa Depression, Tarim Basin

Zhuo Qingong, Li Yong, Song Yan, Yang Xianzhang, Zhao Mengjun, Fang Shihu, Liu Shaobo, Lu Xuesong

2013, 35(1): 42-47. doi: 10.11781/sysydz201301042

Abstract(1991) PDF-CN(1291)

Abstract:
Saline deposits are good regional cap rocks in petroliferous basins, yet not perfect. Research shows that saline deposits are characterized by "embitterment at low temperature and plastic deformation at high temperature". The sealing capacity of saline deposits changes with burial depth, and the depth from 3 000 to 3 200 m is critical to the capping effectiveness of saline deposits in the Kelasu tectonic zone. The effectiveness of subsalt trap accumulations is influenced by the evolution of saline deposits. The key time for the closing of cap rocks in the anti-cline zone of Kesalu is the middle and late Kuqa periods, and the main exploration targets are the complete anticline traps buried over 3 200 m deep. In the deep zone of Kelasu, the key time for the closing of cap rocks is the early and middle Kuqa periods, and petroleum may be trapped in subsalt blocks and broken anticlines when faults are laterally sealed. Research fits the status of exploration, and helps to improve exploration success rate.

Petroleum geologic features and exploration potentials in deep-sea fan, Bay of Bengal

Wu Yiping, Zhang Yanmin, Tian Zuoji, Li Fuheng, Wang Hongping

2013, 35(1): 48-52. doi: 10.11781/sysydz201301048

Abstract(2294) PDF-CN(1198)

Abstract:
The deep-sea fan of the Bay of Bengal served as the main body for the LST of deep sequence. Tertiary complex sand bodies with giant thickness deposited. 5 sequence boundaries were identified. 3 sets of source rocks in the Bhuban Formation of Miocene, the Jenam Formation of Oligocene and the Kopili Formation of Eocene gave birth to hydrocarbon during the early Pleiocene (5 Ma), the end of Oligocene (29.3 Ma) and the end of Paleogene (23.3 Ma), respectively. Deepwater turbidity sandstones worked as the main reservoir, and were featured by a depositional model of multi-period vertical overlap. Oligocene-Miocene reservoir and seal assemblage was the most favorable. Vertically, faults, unconformities and continuously-distributed sand bodies provided good pathways for petroleum migration. The possible accumulation models belong to stratigraphic reservoirs of "above-generation and below-storage" or complex ones. Natural gas is the dominant product in the deep water zone of the Bay of Bengal. Therefore, the Tertiary aggradational confined channel complexes in the deep-water basin of the Bay Rim of Bengal, such as the upper-middle deep water fans of the Ganges river system and the Indian eastern sea, as well as the natural alluvial sand embankments near to "bottomless channel" in the middle-lower deep water fans are considered as the most potential zones.

Diagenesis stage division and petroleum geologic significances of Dainan Formation in Jinhu Sag, Northern Jiangsu Basin

Zhang Qin, Zhu Xiaomin, Dong Guodong, Mao Ling, Yang Ligan, Chen Qingyun

2013, 35(1): 53-59. doi: 10.11781/sysydz201301053

Abstract(1918) PDF-CN(1098)

Abstract:
Based on the analysis and testing data of microscopic slice, scanning electron microscope (SEMP), X-ray diffraction and fluid inclusion microthermometry, the diagenesis stage of clastic reservoirs of the Dainan Formation in the Jinhu Sag has been divided and confined according to vitrinite reflectance, buried history curve, and the variation of clay mineral as well as various diagenesis phenomena and marks. Most of the Dainan Formation is in A phase of the middle diagenesis stage, and less in B phase of the early diagenesis stage and B phase of the late diagenesis stage. Corresponding to diagenesis stage, pore types in the Dainan Formation also evolve from primary to secondary ones. At present, secondary pores account for a large amount in the Dainan Formation while primary pores are seldom found. It is predicted that the areas around wells Xinzhuang 1, Tian X77 and Guan X2 are favorable for reservoir formation. Based on the division of diagenesis stage, the organism in the underlying Funing Formation in most of the study area is predicted matured as the main hydrocarbon source rocks of the Dainan Formation. And it is inferred that the Dainan Formation in the areas around wells Qin X2, Tian X75 and Tian X92 has encountered strong structural uplift and erosion during the early buried stage.

Geologic features of abyssal topography and drilling conditions in block JDZ-2, Nigeria

Cheng Xuefeng

2013, 35(1): 60-64. doi: 10.11781/sysydz201301060

Abstract(1831) PDF-CN(1350)

Abstract:
In block JDZ-2 of Nigeria, oceanic 3d seismic data have been applied to obtain the reflection time to seabed. The water depth is calculated, on the basis of which a detailed topography of seabed is drawn. The types and distribution of seabed topography are analyzed. Combined with the drilling results of adjacent blocks, by means of 3d seismic data, the sequences of shallow formation are divided. 4 sequences are traced and interpreted on seismic profiles. The underlying geologic disasters to drilling engineering in the shallow formation of the whole block are demonstrated. According to the abovementioned analysis, the fine research of topographic characteristics and potential shallow calamities in the planned area for drilling is completed. The first exploration well surface location is optimized and the countermeasures are established for drilling. The research would be guidable for further explorations.

Forming mechanism of quasi-continuous tight sandstone reservoir of Chang 6 oil-bearing formation, Ordos Basin

Bai Yubin, Zhao Jingzhou, Fang Chaoqiang, Liu Peng

2013, 35(1): 65-71. doi: 10.11781/sysydz201301065

Abstract(1845) PDF-CN(1138)

Abstract:
The Chang 6 reservoir in the Yanchang Formation in the Shanbei slope of the Ordos Basin is a typical quasi-continuous unconventional tight sandstone reservoir. It has 7 main features as followed. (1) The formation and distribution of the Chang 6 reservoir were not restricted by traps. Oils spread for big area and were connected. (2) Regional relatively stable tectonic background and tight sand bodies connected for big area were the external factors for the formation and distribution of the Chang 6 reservoir. (3) Matured hydrocarbon source rocks in the Chang 7 formation were connected widely. High-strength hydrocarbon generation and expulsion were the basis for the formation and distribution of the Chang 6 reservoir. (4) The Chang 6 reservoir mainly resulted from primary migration and secondary migration of short distance. Vertical cracks and laterally-connected sand body effective combinations provided favorable pathways for petroleum migration. (5) The abnormal overpressure caused by hydrocarbon generation was the main force for petroleum migration. Buoyancy effect was very weak and played an unimportant effect in controlling the formation and distribution of the reservoir. (6) Oil and water distributions were complex in the Chang 6 reservoir. Pure oil was not found. Oil/water, water and dry layers coexisted. There was no unified oil/water boundary or pressure system. The reservoir had strong heterogeneity. Oil saturation was not unified. Reserve abundance was low. Cookies were found locally. (7) The Chang 6 reservoir had been compacted before the mass migration of petroleum, serving foundation for the formation of the Chang 6 quasi-continuous tight sandstone reservoir.

Basic regularity of petroleum exploration development

Guo Yuanling

2013, 35(1): 72-75. doi: 10.11781/sysydz201301072

Abstract(1593) PDF-CN(1153)

Abstract:
The development of exploration is shown by the growth of reserves, and is influenced by team, environment and resource. It is easier to find the common elements (summarized as exploration system, guiding ideology, capability and process) in exploration if the differences of resource are not taken into consideration. The exploration system is an institutionalized correlation form among all of the essential factors. The structure of exploration system is decided by the strategic demands for resource and the different stages of exploration. Exploration guiding ideology of science is the key to the formation of strong exploration capabilities, and determines the working quality of exploration process. The various elements work together, and decide the growth characteristics of the reserves. The concept of the basic regularity of petroleum exploration development is put forward, which might be conducive to the regularity analysis of the characteristics of exploration activities.

Determination of maturity for source rocks in Biyang Sag of Nanxiang Basin and its significance

Li Zhiming, Zhang Jun, Yu Xiaolu, Bao Fang, Xie Xiaomin, Yang Yunfeng, Luo Jiaqun, Zhu Jingxiu

2013, 35(1): 76-80. doi: 10.11781/sysydz201301076

Abstract(2553) PDF-CN(1223)

Abstract:
19 source rock samples of lacustrine facies have been collected from the Hetaoyuan Formation in 15 drilling wells in the Biyang Sag of the Nanxiang Basin, and their maturities have been determined by means of fluorescence alteration of multiple macerals (FAMM) technique. The vitrinite reflectance of source rocks from the Hetaoyuan Formation is obviously suppressed, and the suppression corrected value is from 0.08% to 0.39%. The level of vitrinite reflectance suppression is relatively higher when source rock quality is better. The maturity of 19 samples has entered oil window (EqVR from 0.58% to 1.29%) instead of 0.38%-1.05% from vitrinite reflectance. According to the maturity of source rocks at different depth in 4 wells, paleogeothermal gradient is 36-45℃/km, and the depth of threshold for oil generation is 1 800-1 400 m. The correct determination of maturity for the source rocks from the Hetaoyuan Formation provides the basis to evaluate the potential of hydrocarbon reasonably.

Chemical features and diagenesis reactions of formation water under abnormal pressure in central depression of northern Songliao Basin

Lei Zhenyu, Xie Xinong, Meng Yuanlin, Huang Wei, Du Xuebin, Xiao Lihua, Meng Fanjin, Jiao Jinhe, Wei Wei

2013, 35(1): 81-86. doi: 10.11781/sysydz201301081

Abstract(1839) PDF-CN(1326)

Abstract:
The pressure system in the central depression of the Songliao Basin was analyzed systematically. A large amount of data about formation water was studied and compared, based on which the ions pattern as well as the diagenesis reaction of formation water were discussed. It has been concluded that abnormal pressure obviously influences geofluid and diagenesis. Both overpressure and underpressure can increase TDS; however, their influencing mechanisms are different. Water type varies in different pressure systems, leading to different diagenesis effects. In overpressure and normal pressure systems, NaHCO₃ and NaCl type water is dominant, and the dissolution of minerals works as the main diagenesis effect. As to underpressure system, CaCl₂ type water is dominant, and the main diagenesis effect is the albitiztion of feldspar.

Physical modeling of petroleum downward migration：A case study of western Chezhen Sag, Jiyang Depression, Bohai Bay Basin

Hao Xuefeng, Shan Yixian, Lao Haigang

2013, 35(1): 87-91. doi: 10.11781/sysydz201301087

Abstract(2014) PDF-CN(972)

Abstract:
According to the theory of hydrocarbon downward migration, based on seismology, geochemistry, well drilling and logging, it is discussed in this paper the accumulation mechanism of petroleum downward migration in the western Chezhen Sag, the Jiyang Depression, the Bohai Bay Basin. The main pathways of hydrocarbon downward migration include factures or micro cracks in the process of secondary migration, and the formation process of hydrocarbon downward migration is reproduced by experimental simulation. Source rocks in the middle and lower subsections of the 3rd member of the Shahejie Formation have good genetic relationships with oil sands from the upper subsection of the 4th member of the Shahejie Formation, and reservoirs discovered in the upper subsection of the 4th member of the Shahejie Formation are buried deeper than the bottom boundary of source rocks from the 3rd member of the Shahejie Formation. In the lower subsection of the 3rd member of the Shahejie Formation, pressure coefficients range from 1.0 to 1.4, and decrease both upwards and downwards, providing force for petroleum downward migration. Cracks and fractures break the mudstone interlayers between the bottom boundary of source rocks from the 3rd member of the Shahejie Formation and the top surface of the 4th member of the Shahejie Formation. As a result, source rocks and reservoirs are connected.

Physical simulation of brush structure in Linbei area, Huimin Sag, Bohai Bay Basin

Jia Hongyi, Tan Mingyou, Han Bo, Tang Mengjing

2013, 35(1): 92-97. doi: 10.11781/sysydz201301092

Abstract(1896) PDF-CN(1123)

Abstract:
Geological structure is very complicated in the Huimin Sag of the Bohai Bay Basin. The brush structure in Linbei area of the Huimin Sag was studied. Based on geologic, logging and seismic data, a geological model for the generation of typical brush structure in the study area was established. The paleo-stress circumstance when the brush structure developed was simulated through the dynamic modeling of tectonic deformation. The brush structure in Linbei area was controlled by the dextrorotatory strike slip tectonic stress field. Several sets of NE oriented echelon normal faults generated from north to south. The evolution sequence was featured by opening in the north and closing in the south. During the period from Es⁴ to Ed, structural activity changed from weak to strong and then to relatively strong, controlling sediment and the generation and migration of main deltas (nose structures).

Application of high-resolution sequence stratigraphy framework in reservoir prediction：A case study of 2nd member of Shuangyang Formation in Moliqing Oilfield

Hu Yuan, Chen Kaiyuan, Zhao Lei, Sun Yang, Li Geng

2013, 35(1): 98-103. doi: 10.11781/sysydz201301098

Abstract(1938) PDF-CN(901)

Abstract:
With multiple sources and multiple stages for strike-slip, the Moliqing Fault Basin has a complicated fracture pattern, and the source stage and reserve distribution still remain discussing. By means of high-resolution sequence stratigraphy, combining lithologic, electric and seismic data together, the 2nd member of the Shuangyang Formation in the Moliqing Oilfield has been divided into 4 4th-grade sequences (equivalent to mid-term base-level cycles) and 13 short-term base-level cycles. A high-resolution sequence stratigraphy framework of the MoliqingOilfield has been established. Grain size, seismic attribute and facies analyses have been applied to study sedimentary micro-facies. Using facies-constrained stochastic modeling method, the reservoir distributing features of high-exploitation blocks A and B have been fitted and the optimal parameters and models have been selected. Then these parameters are applied to the reservoir prediction in blocks C and D which are in low exploitation degree. Six oil-bearing reservoirs in the 2nd member of the Shuangyang Formation in the south of block C have been predicted with this method. The change from qualitative analysis to semi-quantitative and quantitative analyses in reservoir research provides more reliable foundation for the exploration and development of lithologic reservoirs.

A practical core cleaning method based on CO₂ dissolved gas drive

Han Xuehui, Yang Long, Wang Hongliang, Wang Xueliang, Fang Tao, Zhang Juanjuan

2013, 35(1): 111-114. doi: 10.11781/sysydz201301111

Abstract(1871) PDF-CN(1089)

Abstract:
In order to improve the efficiency of core cleaning, a practical core cleaning method based on CO₂ dissolved gas drive was developed. The method added vacuum-pumping, CO₂ pre-cleaning and solvent recovery to the method designed by Stewart in 1952. Then, the effect of core cleaning was observed through a series of experiment with the employment of DGO-1 type CO₂ dissolved gas drive core cleaning device which was self-made. The results of core cleaning of 6 rocks with different porosities and permeabilities showed that the fluorescence level was less than 3 and the porosity and permeability were steady after 6-10 circles. The effect met the standard SY/T 5336-2006. The period of core cleaning with the employment of the new method was 2-3 days, which was less than that of Soxhlet extraction device (2-3 weeks or longer). Since the method had the characteristics of clear principle, simple device, good operability, high efficiency and was environmental-friendly, it was recommended to popularize in rock physics lab.

2013 Vol. 35, No. 1

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