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

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.