Well-path optimization technology for stepped horizontal wells with large drop in the fault block reservoirs

In order to reduce the friction when running string in stepped horizontal wells in the fault block reservoir with large drop in the Dongpu depression, studies on optimization of well-path of stepped horizontal well with large span were carried out. Given the actual angle building rate of the formations, the pre-target displacement and build-up rate of the building up section were optimized. A model for analyzing the running friction of completion string with packer (or centralizer) and stress was built, and the wellbore curvature and displacement difference of the stepped transition interval was optimized. Analysis shows that, when the pre-target displacement at building up section is controlled at 300~400 m, the building rate is low first, then becomes high. Properly reducing the building rate and displacement difference of the stepped transition interval help reduce drilling friction and string running friction. The design result was used in four stepped horizontal wells in Dongpu Depression, the targeting rate of stepped landing was 100%, the maximum reservoir encountering ratio was 95.3%, the maximum horizontal section was 1 214 m, and the drop difference of faulted block was controlled at 7.14~40.3 m. The result of application indicates that the use of staged assessment method to optimize the parameters of stepped horizontal well track is pertinent and comprehensive and provides reference for the design of similar stepped horizontal wells.