断裂沥青带及其油气地质意义

Fault asphalt zone and its significance in petroleum geology

断裂作为油气运移的垂向通道与油气聚集的侧向遮挡条件,在断裂发育区的油气运移聚集中具有重要作用,其输导机理也是油气运移研究的热点之一。以在渤海湾盆地东辛复杂断块油气田发现的断裂沥青带为研究对象,对其成因及油气地质意义进行了探讨。研究表明,控制构造带形成的主干生长断层在其活动期间可以产生一些较大的"空洞",即"断裂空腔"。"断裂空腔"的形成受断层活动期的应力状态、两侧岩性、断面形态以及石油充注等因素的控制,断面形态的突变处是"空腔"产生的有利地区。"断裂空腔"发育的位置及规模不同,导致断层不同部位流体输导能力的差异,"断裂空腔"是油气沿断层运移的优势通道和汇聚区。油气进入"空腔"并聚集后,轻组分逐渐散失,重组分残留形成沥青。

As main conduits of hydrocarbon migration as well as seals,faults play an important role in hydrocarbon accumulation,especially in heavily faulted areas.The mechanism of hydrocarbon migration in fault zones remains to be a major issue in petroleum geology.This paper deals with the origin of fault asphalt zone and its significance in hydrocarbon migration in the Dongxin oil-gas field in Bohai Bay Basin.The results show that the larger growth-fault can form bigger cavities along fault zone during periods of active faulting.The characteristics of fault cavities are dependent mainly upon stress state,lithology,the shape of fault plane and hydrocarbon injection,with areas of high fault-plane irregularity being more favorable for occurrence of fault cavities,which in turn are better conduits for hydrocarbon migration.Therefore,the position and size of fault cavities determine the different migration paths of hydrocarbons along a fault.Once hydrocarbon migrates into the cavities,light components of hydrocarbon are escaped firstly,leaving the remains of heavy residue,i,e.,asphalts.