高压注水井裂缝分析及合理压力界限的确定

Fracture Analysis and Reasonable Injection Pressure Limit Definition of High Pressure Waterflooding Well

油田在高压注水过程中,有些吸水指示曲线出现弯曲现象。采用流度分析和注水过程中引起的地应力变化方法,判定注水过程中是否有裂缝产生,并确定出高压注水的合理压力界限。通过对2口井的计算分析,说明高压注水过程中造成吸水指示曲线弯曲的原因是注入水降低了地层的地应力,使得井底附近有微裂缝产生。通过泣水与地层温差引起的地应力变化及注水使孔隙压力增加引起的地应力变化,导致在注水过程中井底附近的地层破裂压力降低。当高压注水时,可控制高压注水压力使之低于地层破裂压力,以防在注水中油层产出裂缝,避免水沿裂缝窜流,影响注水的开发效果。

During the process of high pressure waterflooding in oilfield, there are bends in some water index curves. Mobility analysis and calculation the in-situ stress changes caused by waterflooding are used to define whether the formation is fractured, and to define the reasonable pressure limit of high pressure waterflooding. Two wells are calculated. The reason of the bend of water index curve is the decrease of in-situ stress caused by waterflooding. It causes the microfracture near the well.