含油气盆地油气藏破坏的油气显示及其地质意义

Oil-gas shows from destruction oil/gas reservoirs in the petroliferous basins of China and their geological significance

油气显示可以为发现与其相关的残留油气藏或次生油气藏提供重要的线索。通过野外调查、地质分析和文献调研,系统研究了各类油气显示在中国各盆地或地区的分布,探讨了油气显示的成因机制,并分析了其石油地质意义。研究表明,按油气藏破坏的程度,油气显示可分为轻度破坏型、严重破坏型和完全破坏型3类。这3类油气显示在中国各盆地或地区广泛分布。其中,油苗、气苗和泥火山等轻度破坏型油气显示主要分布在中国西部和南方;稠油等严重破坏型油气显示主要分布在中国西部和东部;天然沥青、沥青砂和地蜡等完全破坏型油气显示主要分布在中国西部和南方。按照油气藏破坏的次数和程度,油气显示可分为直接破坏成因和二次破坏成因。直接破坏成因的油气显示包括地表油苗、气苗和泥火山,它们的形成主要受强烈构造运动、频繁地震和快速沉积等因素影响,按照出露地表的方式可细分为断裂通天型、隆升剥蚀型、底辟刺穿型和不整合面露地型4种类型。二次破坏成因的油气显示包括地表和地下的稠油、天然沥青、沥青砂和地蜡,其显著特征是油气发生直接破坏后又发生了水洗、氧化、生物降解等稠变作用,它们常具有共生或过渡的关系。在勘探早期,轻度破坏型或位于活动冲断带和底辟构造上的油气显示对地下油气藏的指导意义更大。各种破坏作用在破坏油气藏形成各种油气显示的同时,有时也可对油气的再分配和保存起到一定的积极作用。因此,保存条件是在油气显示发育区寻找油气藏的关键因素。

Oil-gas shows can provide much important information to explore the related residual or secondary reservoirs. Based on field survey, geological analysis and literature investigation, this paper systematically studied the distribution of oil-gas shows in different basins/regions in China, discussed their genetic mechanisms and analyzed their petroleum geo- logical significance. According to the degree of destruction of reservoirs, oil-gas shows can be classified into three types： partial destruction, strong destruction, and complete destruction. All these three types of oil-gas shows are widely distribu- ted in each basin/region in China. The partial-destruction type of oil-gas shows, including oil seepage, gas seepage and mud volcano, is mainly distributed in the western and southern China. The strong-destruction type of oil-gas shows such as heavy oil is mainly distributed in the western and eastern China. The complete-destruction type of oil-gas shows, such as natural bitumen, tar sand and mineral wax, mainly occurs in the western and southern China. On the other hand, in terms of the times and extent of destruction of reservoirs, the genetic mechanism of oil-gas shows can be categorized into two types：primary-destruction and secondary-destruction. The former type of oil-gas shows include surface oil seepage, gas seepage and volcano and their formation are influenced by the intense tectonic movements, frequent earthquakes and rapid deposition. It can be further divided into four kinds according to their ways of out-flowing the surface of earth ： surface-cut- ting fault, uplifting-denudation, diapir penetrating, unconformity outcropping. The secondary-destruction type of oil-gas shows include heavy oil, natural bitumen, tar sand and mineral wax on the surface and underground, and features in waterwashing oxidation and biodegradation after destroyed directly and they are usually paragenic and transitional. In the early stage of i^etroleum exploration,the oil-gas shows of partial-destruction type or that on thrust belt and diaper structure have greater guiding significance to discover underground reservoirs. On the one hand, although all kinds of destructive effects can destroy reservoirs to form oil-gas shows, they could also have positive influences on the redistribution and preservation of hydrocarbons. Therefore, preservation condition is the key factor to find reservoirs in areas with oil-gas shows.