Abstract: Xishanyao reservoir in Cainan oilfield is a typical low-extra low permeability oil pool with well developed micro-fracture and serious heterogeneity of reservoir. Following the several-year high level of production, it has appeared in quickly rising water cut, high pro-duction decline and complicated distribution of formation pressure field due to water breakthrough and watered out. Hence, a series of measures have been taken such as conventional and depth profile controls in water injection wells and "econdary plus tertiary recovery technologies”, based on in-depth reservoir studies in order to make sure development of pay zone in vertical and horizontal directions, connection between injection and production wells, reservoir depositional microfacies, petrophysical facies, fractural facies and fluid flow behavior. The results have shown that producing level of pay zone increases from 68% to 95%, enabling deep flow to be displaced transversely, and improving water flooding swept volume and displacement efficiency. Each injection well is stimulated, and followed by two production wells being responsible in average. W ater cut in the stimulated well group decreases from 4.5% to 2.9%, with production decline slowing down from 20% to 10%, along with input-output ratio over 1: 3.5. These profile control measures have played important roles in stable oil production by water-cut control for the whole reservoir, and offered significant economic efficiency.

Key words: Junggar basin, Cainan oilfield, low permeability reservoir, sweet fficiency, oil displacement fficiency, injection profile