Abstract:

Fractures are the main flowing channel and effective storage space for the low permeability reservoir in Chaoyanggou Oilfield, Songliao Basin. The exploitation of oil deposits in this oilfield is strongly controlled by the complex distribution of fractures. Based on regional tectonic study, core structural analysis and the data from outcrops and thin sections, we have studied the developmental characteristics, the genetic mechanism and the controlling factors of the fractures in the Chaoyanggou Oilfield. The results show that there are four sets of tectonic fractures in the reservoir,  extending in the southnorth, eastwest, northwest and northeast orientations respectively.  The fractures with low dipangle are dominant in the studied area, which are mainly the alongbedding detachment fractures formed by compressive folding, and the shear fractures related to the thrusting of faults. The fractures with high dipangle are mainly the extension fractures and oblique fractures. The tectonic fractures are mainly formed in the reversal tectonic stage at the end of Mingshui Formation, when there developed the nearly SN and nearly EW orientations fractures. The development degree of the fractures is controlled by the factors of lithology, strata thickness, the faulting, the folding, the depth, etc. The development degree of fractures is different with different lithology; there is a linear relationship between the fracture spacing and the fractured strata thickness; most fractures have a relation to the faulting; the types of fractures are different with different formation phases of the fold; and the development degree of fractures is sharply decreased with the increase in depth.

Key words:

Key words: reservoir fracture; development characteristic; controlling factor; Chaoyanggou Oilfield; Songliao Basin