克拉玛依油田八区下乌尔禾组油藏小井距开发试验

Pilot Test of Close Spacing Development in Lower Wuerhe Reservoir of District No.8 of Karamay Field

克拉玛依油田八区下乌尔禾组油藏为巨厚的特低渗透砾岩油藏,前期采用275 m井距反九点井网注水开发,油井见效低、压力保持程度低、采油速度低,低渗透储集层较大注采井距难以建立有效水驱是开发效果差的主要原因。小井距试验通过细分开发层系、缩小井距、改变井网方式以建立有效水驱体系。将开发层系细分为3套,逐层上返,首先试验P2w4,由275 m×388 m反九点井网加密为138 m×195 m反九点井网,后期转为五点井网平行裂缝方向注水。同时,控制单井注水量,采用点弱面强的注采政策。试验3 a后,与八区正常井距区块相比,各项开发指标明显好转,预计可提高采收率8.5%.

Lower Wuerhe reservoir of District No.8 in Karamay oil field is a thick massive ultra-low permeability conglomerate reservoir, and was developed by waterflooding process with inverted nine-spot pattern and well spacing of 275 m in one series of strata in early stage. But it featured such poor development effects as the low efficiency of response for producers, low pressure maintenance degree and low oil production rate. The low permeability reservoir and larger producer-injector well spacing should he the main reasons for it was hard to establish effective waterflood response. This paper presents the close spacing pilot test that is to establish effective waterflood system by subdividing the layer series of development, decreasing the well spacing and changing the well patterns. The layer series of development is subdivided into three layers and recompleted layer by layer. The WU-4 unit is the first layer to be tested. The inverted nine-spot well pattern is infilled from 275 m×388 m to 138 m×195 m in the first stage and then converted into five-spot pattern to take a waterflood along parallel fractures, while controlling the injection flow rate by strategy of water drive weak at the spot and intensive in the area. Three- year test has shown that the production indices are all better than the original ones before, and it is expected that the recovery factor will be increased by 8.5% by this test.