Xinzhao oilfield, a naturally fractured low-permeability field in Daqing, was put into development in 2000 using an inverted nine-spot waterflood pattern with 300m×300m well spacing. Although waterflooding at Xinzhao oilfield had been an economic success, performance had generally been considered disappointing because oil response following expansion and waterflood adjustment was always less than predicted, so an integrated study aiming to improving the development effect of Xinzhao oilfield was conducted. This paper presents the results of a study addressing the impact of fractures on the recovery and on the reservoir management in pattern waterfloods.
Geological study and reservoir performance study indicate that several factors result in this seemingly unfavorable performance, one of main reasons are that the inverted nine-spot pattern is not compatible with the orientation of fractures. The production wells on the row of injectors are seriously watered-out and watercut increases very fast. Reservoir simulation studies indicate that oil cut can be improved if the injection pattern is modified from current inverted nine-spot well pattern to direct line drive pattern to take advantage of orientation of fractures. A field test project based on these studies has yielded results that indicate improved economic performance and better development effect.