Formation Mechanism of High-Obliquity Faults in Platform Areas of Chinese Western Basins and Their Control on Petroleum Migration and Occurrence
-
摘要: 给出了中国西部盆地台盆区普遍发育高角度(倾角 > 45°) 断层的证据, 从断裂形成的力学机制上分析了高角度断层的成因, 认为中国西部盆地台盆区高角度断层的形成主要受压扭性应力场控制, 同时与脆性地层的变形特点有关.断层面静封闭压力由岩石泊桑比、上覆地层容重、断层埋藏深度和倾角、最大和最小主应力以及断层走向与最大主应力方向的夹角等计算, 作为断层开启性评价的一个指标, 断层面静封闭压力的计算表明, 断层的开启性随断层倾角的增加而增加, 同时, 沿断层面运移的油气所受浮力在平行断层面方向上的分力也随着断层倾角的增加而增加, 这就决定了高角度断层更有利于油气的垂向运移.结合西部盆地的具体分析, 认为中国西部盆地区域性高角度断层是沟通深部成藏动力学系统与中上部成藏动力学系统的重要通道, 是中上部系统成藏的关键, 直接决定着中上部系统中油气的分布, 在每一系统内部发育的高角度断层具有使油气在断层断开的最新层位中优先充注成藏的基本规律.这些认识对指导油气勘探具有重要意义, 而且, 这些认识同样可推广到其他存在高角度断层的盆地中.Abstract: High-obliquity faults (superior to 45°) are very commonly encountered in the platform areas in Chinese western basins. Geomechanical analysis demonstrates that high-obliquity faults are produced by the compression-torsion stress field existing in Chinese western basins, and they may also be related to the stratum's brittle deformation. Static sealing pressure, which can be calculated from Poisson's coefficient, burial depth, obliquity degree of the fault, and maximum and minimum principal stresses, is used as an index of the sealing capacity or openness degree of a fault for petroleum migration. The calculation of static sealing pressure indicates that the openness degree of a fault increases with the fault's obliquity degree. The floating force decomposition illustrates that the decomposed force along the fault surface also increases with the fault's obliquity degree. Therefore, vertical, cross-formational petroleum migration via a high-obliquity fault is easier than via a low-obliquity fault. This conclusion is applied to interpret the control of high-obliquity faults on petroleum migration and occurrence in the Tarim and Junggar basins of western China.Conclusionsare: (1) Regional high-obliquity faults crossing different dynamic fluid systems control the petroleum distribution in different systems, especially as petroleum migration pass-ways for the middle-upper systems, as they are essential for pool formation in the latter; (2) Inside each dynamic fluid system, petroleum migrating along high-obliquity faults is most likely tofill the newest layer cut by the faults. The conclusions obtained have clear implications for petroleum exploration and these conclusions can be extended to other basins where high-obliquity faults exist.
-
图 9 塔里木盆地轮南2井油藏油气运聚和调整剖面(顾家裕和周兴熙, 2001)
1.油层; 2.残余油显示; 3.断层
Fig. 9. Profile of petroleum migration-accumulation and adjustment of well Lunnan 2 reservoir in Tarim basin
表 1 西部叠合盆地部分断层倾角统计
Table 1. Statistics of some faults' obliquity in some western basins
-
Allen, P.A., Allen, J.R., 1990. Basin analysis, principle and application. Blackwell Scientific Publications. Gu, J.Y., Zhou, X.X., 2001. Tarim basin Lunnan buried hill and occurrence of oil and gas. Petroleum Industry Press, Beijing(in Chinese). Kang, Y.S., Qiu, N.S., Liu, L.F., et al., 2004. Influence of fluid dynamic systems on homogenization temperatures of fluid inclusions and its significance— An application example from the Ludong area of Junggar basin, northwestern China. Acta Geologica Sinica, 78(5): 704-709(in Chinese with English abstract). Luo, Q., 2002. Fault controlling hydrocarbon theory and petroleum exploration practice. Earth Science—Journal of China University of Geosciences, 27(6): 751-756(in Chinese with English abstract). Luo, X.R., Xiao, L.X., Li, X.Y., et al., 2004. Overpressure distribution and affecting factors in southern margin of Junggar basin. Earth Science—Journal of China University of Geosciences, 29(4): 404-412(in Chinese with English abstract). Perez, R. J., Boles, J., 2002. Evidence and scale of mass transfer associated with a Quaternary thrust fault: Examples from the Wheeler Ridge oilfield, southern San Joaquin basin, California. AAPG Bulletin, 86(13). Shutaro, H., Sorkhabi, R., Iwanaga, S., et al., 2002. Fault seal analysis in the Temana field, offshore Sarawak, Malaysia. AAPG Bulletin, 86(13). Sibson, R.H., 1994. Crustal stress, faulting and fluid flow, In: Geofluids: Origin, migration and evolution of fluids in sedimentary basins. Geological Society Special Publication, 78: 69-84. doi: 10.1144/GSL.SP.1994.078.01.07 Smith, D. A., 1980. Sealing and nonsealing faults in Louisiana Gulf salt basin. AAPG Bulletin, 64(2): 145-172. Wang, P., Li, J.F., Li, Y.Q., 1994. Exploration and development of complex faulted oil reservoirs. Petroleum Industry Press, Beijing(in Chinese). Wang, X.P., Yan, J.J., 1995. Structural framework of major faults in north Tarim basin. Earth Science—Journal of China University of Geosciences, 20(3): 237-242(in Chinese with English abstract). Wei, G.Q., Jia, C.Z., 2001. Tectonic characteristics and petroleum accumulation in extensional-shear fault system in Mesozoic-Cenozoic formations in the northern area of Taibei uplift, Tarim. Acta Petrolei Sinica, 22(1): 19-25(in Chinese with English abstract). Wei, G.Q., Jia, C. Z, Yao, H.J., 1995. The relation of thruststrike slip structure and hydrocarbon potential in late Hercynian in north area of Tarim basin. Xinjiang Petroleum Geology, 16(2): 96-102(in Chinese with English abstract). Yang, C.L., Wu, Q.Z., Xia, Y.P., 2000. The origin of Mesozoic-Cenozoic extension-torsional fault system in the north positive element in the Tarim basin, and its role in accumulating oil and gas. Oil Geophysical Prospect, 35(4): 461-469(in Chinese with English abstract). 顾家裕, 周兴熙, 2001. 塔里木盆地轮南潜山岩溶及油气分布规律. 北京: 石油工业出版. 康永尚, 邱楠生, 刘洛夫, 等, 2004. 流体动力系统对流体包裹体均一温度的影响及其意义——以准噶尔盆地陆东地区为例. 地质学报, 78(5): 704-709. doi: 10.3321/j.issn:0001-5717.2004.05.015 罗群, 2002. 断裂控烃理论与油气勘探实践. 地球科学——中国地质大学学报, 27(6): 751-756. https://www.cnki.com.cn/Article/CJFDTOTAL-DQKX200206017.htm 罗晓容, 肖立新, 李学义, 等, 2004. 准噶尔盆地南缘中段异常压力分布及影响因素. 地球科学——中国地质大学学报, 29(4): 404-412. https://www.cnki.com.cn/Article/CJFDTOTAL-DQKX200404004.htm 王平, 李纪辐, 李幼琼, 1994. 复杂断块油田详探与开发. 北京: 石油工业出版社. 王燮培, 严俊君, 1995. 塔里木盆地北部断层格架分析. 地球科学——中国地质大学学报, 20(3): 237-242. 魏国齐, 贾承造, 2001. 塔北隆起北部中新生界张扭性断层系统特征. 石油学报, 22(1): 19-25. doi: 10.3321/j.issn:0253-2697.2001.01.004 魏国齐, 贾承造, 姚慧君, 1995. 塔北地区海西晚期逆冲—走滑构造与含油气关系. 新疆石油地质, 16(2): 96-102. https://www.cnki.com.cn/Article/CJFDTOTAL-XJSD502.001.htm 杨春林, 吴奇之, 夏义平, 2000. 塔里木盆地北部隆起中、新生界张扭断层系统成因及其油气聚集的作用. 石油地球物理勘探, 35(4): 461-469. doi: 10.3321/j.issn:1000-7210.2000.04.008