雷家油田下第三系低渗透储层裂缝特征

雷家油田下第三系低渗透储层中的裂缝分为节理型裂缝和断层型裂缝2种类型,其中断层型裂缝又可分为穿层、顺层裂缝。节理型裂缝垂直分布于岩层内,裂缝面两侧无错动,断层型裂缝面两侧有明显的错动,其中穿层裂缝呈高角度切割岩层,具有与区内正断层相一致的分布或组合样式,而顺层裂缝与层面近平行分布在泥岩夹层中。它们主要在伸展构造作用下形成,近东西向水平挤压作用也有重要的影响。裂缝的发育和分布受岩性、岩层厚度及断层等因素的控制。在低渗透储层的泥质夹层中,由于穿层裂缝及顺层裂缝发育,并相互连通组成三维裂缝网络系统,对油气的储渗有重要意义。岩层中裂缝的平均间距与层厚呈线性相关关系。伸展断层附近裂缝的发育具有较好的分带性,断层上盘的裂缝较下盘更发育。

FRACTURE CHARACTERISTICS OF EOGENE LOW PERMEABLE RESERVOIRS IN LEIJIA OILFIELD

The fractures in Eogene low permeable reservoirs of Leijia Oilfield could be divided into joint type and fault type fractures,within which the fault type fractures could be subdivided into cross bed and bedding fractures.The joint type fractures are distributed vertically with no displacement on the two sides of the fractnres,while those of fault tyre have evident displacement.The cross bed fractures cut rock layers at high angles and are similar in distribution and association pattern to that of normal faults in the study area; the bedding fractures are distributed in mud interlayers parallel to bedding plane.The development and distribution of the fractures are controlled by lithologic characteristics,rock thickness and faults.Well developed fractures in mud interlayers usually connect with each other and form 3 D fracture network.This is important for oil and gas reservoiring.The average space between fractures bear linear relation.Fractures developed near extentional fault show evident zonation,and the fractures developed well in the upper wall of the fault than that on the lower well.