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断层圈闭比简单的四向倾没圈闭风险性更大。要准确评估圈闭风险性,需要作更多的分析。可靠的断层圈闭评价始于精确的断层作图。未断裂的四向倾没的圈闭是最简单、最富吸引力的油气圈闭。一种封堵性岩性就能既提供顶部封堵,又提供侧向封堵。未断裂的四向倾没圈闭的封堵风险将趋于最低。遗憾的是,大多数大型的这类圈闭已被钻开,在美国墨西哥湾海岸区之类的老油气区尤其是如此。在深水区、地层深处或侧向速度差异很大的地区也许有例外,但研究老油气区的勘探人员多半要么寻找断层圈闭,要么寻找地层圈闭。本文重点研究张性断层体系,不过,许多观察结果也适用于挤压断裂和走向滑动断裂。文中讨论了以下4个问题; (1)断层作图,包括有关断层混淆问题、断层形状、三维数据、雁行断层和相干数据体的讨论; (2)断层圈闭的一般讨论; (3)并置圈闭及“Allan剖面图”的用途; (4)断层封堵圈闭和造成断裂带毛细性质与未断裂岩石毛细性质差异的三种机理——粘土“涂抹”作用、颗粒破碎作用和成岩作用。
Fault traps have a greater risk than simple four-way dumping. Accurate assessment of trapping risk requires more analysis. Reliable fault trap evaluation begins with accurate tomography. Unbroken 4-way dip trap is the easiest and most attractive oil and gas trap. A plugging lithology will provide both a top seal and a lateral seal. Unbroken four-way dump closure risk will tend to be the lowest. Unfortunately, most large traps of this kind have been drilled, especially in old oil and gas areas like the US Gulf Coast. There may be exceptions in deep-water areas where depths or lateral velocities vary widely, but most of the prospective oil and gas exploration geologists search for fault traps or stratigraphic traps. This paper focuses on the Zhang fault system, however, many observations are also applicable to the extrusion fracture and strike-slip fracture. The following four questions are discussed in the paper: (1) fault mapping, including discussions of fault confusion, fault shape, 3D data, geese faults and coherent data bodies; (2) general discussion of fault traps; (4) the three mechanisms of fault sealing and trapping and the capillary nature of the fault zone and the capillary nature of the non-fractured rock - the role of clay “smear” Crushing and diagenesis.