Abstract:

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.

Key words: tectonic fracture, development characteristics, low-permeable reservoir, Eogene System, Leijia Oilfield