Fracturing technologies for low-grade sandstone gas reservoirs and their application to DF109H well
Gas reservoirs of Xujiahe Formation,Dongfengchang area,central Sichuan Basin,are characterized by extra low porosity and permeability,high water saturation and normal pressure,leading to terrible effects in their stimulation and sta-ble production after the early regular fracturing.Thus,we discussed fracturing technologies via an example from the new DF109H well in order to draw on the low-grade gas reserves in this formation.Geology-engineering integration technolo-gies were appeared through a series of research to reduce reservoir damage,speed up flowback,enlarge stimulated bulk,and realize efficient proppant placement.Results show that(i)one system of working fluid which is composed of energized prepad liquid nitrogen and water-based drag reducer can increase flowback energy in tight gas reservoirs with normal pres-sure,so as to advance liquid drainage and cut down reservoir damage,and to make a rapid breakthrough in deliverability;(ii)sweet spots of both mud and well logging are selected for perforating,and differential high-density fracture arrangement is conducted.Large displacement and composite temporary plugging are used to enlarge the size of hydraulic fractures,de-crease flow distance and raise distal supply capacity;and(iii)that fractures remain effective for a long time is the key to stable production.Fiber and dispersing agent are injected through pulse plug during sand fracturing so that proppant is placed more uniformly.In conclusion,with fine fitness in the tight gas reservoirs,these technologies may increase the pro-duction substantially and become considerable measures for the efficient reservoir development in Dongfengchang area.
Sandstone gas reservoirWater-based drag reducerHigh-density fractureEfficient proppant placementFrac-ture
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