涠洲12-1油田注气重力辅助稳定驱替机理研究

Research on gas injection & gravity assisted stable and displacement mechanism in Weizhou12-1 oilfield

涠12-1油田涠四段油藏注采井网不完善,并且在钻完井过程中由于储层受到严重污染,注水较晚,最终导致涠四段油藏地层压力下降,开发效果不好。为改善该油藏开发效果,试图进行注气开发,为确定油藏注气开发的效果,结合油藏的地质油藏特点,综合运用带倾角的长岩心注气重力稳定驱、带倾角的注采井组二维均质剖面模型、层状剖面模型以及韵律剖面模型,并采用注气驱机理数值模拟的方法对注气驱替机理进行了研究。模拟结果表明,涠洲12-1油田中块涠四段注气非混相驱油的主要机理为重力分异辅助作用,储层非均质性、油气毛管压力和注入气黏度变化对注气驱油的采收率影响较小。采油速度不超过5%,注气近混相驱可以形成比较稳定的下倾气驱油界面,且比注水开发将提高采收率10个百分点以上。

Imperfect well pattern in Wei4 reservoir of Wei12-1 oilfield and late water injection for reservoir polluted seriously during drilling and completion lead to relief of formation pressure in Wei4 reservoir.Therefore,the development effect is not good.In order to improve development effects of reservoirs,development of gas injection is tried to do.For determination of development effects of reservoir gas injection,combining with the geological reservoir characteristics,gas injection and displacement mechanism is studied by considering comprehensively as follows:long core gas injection and gravity stability drive with dip angle,numerical simulation method of gas injection drive mechanism from two dimension homogeneous profile model,layered profile model and rhythm profile model of injector-producer group with dip angle.Simulation results show that the main mechanism of gas injecting immiscible displacement of Wei4 area in middle block of Weizhou12-1 oilfield is gravity divergence assistant effect.Moreover,recovery efficiency of oil displacement by nitrogen injection is influenced little by reservoir heterogeneity and variation of oil and gas capillary pressure and viscosity of gas injected.Oil recovery rate is less than 5%,near-miscible flooding with gas injection may form comparatively stable down-dip gas displacement interface and is with 10% higher oil recovery rate than water injection development.