The Development Of SAGD Technique For Double Horizontal Wells In Medium-deep Of Extra-heavy Oil Reservoir

The principal development methods in heavy oil are using thermal methods,such asCSS、Steamflooding、ISC and SAGD.SAGD is the main technology to enhance recovery ratioafter late stage of CSS for super-heavy oil,which has commercial applied in the USA andCanada,its ultimate recovery ratio can reach60to70percent high.But foreign oil reserviorsare usually buried shallow,at depths less than500meters. Super-heavy oil reservoir in Chinaare mainly distributed in the Liao-he and Xin-jiang Oilfield, the recovery ratio of CSS islower than20percent.As for domestic super heavy oil reservoir has such characteristics as deep buried depth,high crude oil viscosity,focusing on the test area that domestic have implemented, this paperhave system analyzed and recognized the main factors affecting development result duringdeep SAGD development.This paper consider that the key factor which affect steam cavity’sdevelopment after SAGD process is interwell heat degree of connectivity.And on the basis ofmeticulous numerical simulation study, performed dual horizontal well SAGD preheatingmethod study, this paper proposed dual horizontal well recycle preheating method beforeturning to SAGD, which can effectively increase the heat degree of connectivity between thedouble horizontal well. And according to the characteristics of double horizontal wells, thispaper has system optimized SAGD Design Considerations, the steam injection rate is300~400t/d, bottom dryness is less than70%, steam injection pressure is about4MPa,theproduction factor had better be greater than1.2, and1.4is the best.Through the above research, the dual horizontal well SAGD technology in deep superheavy oil reservoir is preliminary formed, this can provide a technical model to furtherimprove oil recovery after CSS in the domestic deep super heavy oil reservoir.