川西DY地区致密砂岩储层裂缝特征及其成藏意义

Fracture characteristics and its hydrocarbon accumulation significance of tight sandstone reservoir in DY Region of west Sichuan

在川西DY地区须家河组致密砂岩气藏的形成过程中,裂缝起到重要作用。通过岩心描述及测井解释,识别出须家河组三段主要发育高角度构造缝。研究区南部裂缝走向为北西向,北部裂缝走向为东西向,裂缝总体充填程度不高。裂缝的产状、发育程度及空间分布与油气的运聚关系密切;裂缝不仅改善了储层的储集性能,更重要的是提高了储层的渗滤能力。通过对裂缝特征和区域构造应力场研究认为,该区主要发育2期裂缝,分别形成于印支晚期和喜山Ⅲ期。第1期,裂缝是"古油气藏"油气运聚成藏的通道之一;第2期,由于古隆起受喜山运动破坏成为断层遮挡圈闭,储层已致密化,裂缝成为油气藏重新调整、富集的主要通道。

Fractures play an important role in the formation of Xujiahe Formation tight sandstone gas reservoir in DY Region.Through the core description and the logging interpretation,this paper identifies that the tectonic fractures with high angle mainly developed in the 3rd Member of Xujiahe Formation and the fracture strike is northwest trending in the south of study area and east-west trending in the north of study area.The degree of filling is not high.The occurrence,degree of development and space distribution of fractures are closely related to hydrocarbon migration and accumulation.Fractures not only improve the reservoir property,but also improve the infiltration capacity of reservoir.Through the study of fracture characteristics and the regional tectonic stress field,it is considered that there are two stage fractures which formed in the late Indochinese epoch and Himalayan Ⅲ period respectively.The first stage fracture is one of channels for gas migration and accumulation,and the second one is the main channel of re-adjustment and enrichment of gas when the palaeohigh becomes fault block trap due to Himalayan movement destructiveness.