Casing Program Optimization and Drilling Matching Technologies for Horizontal Wells in Sulige Gas Field

The tight gas reservoirs in Sulige Gas Field are characterized by deep buried depth, prominent collapse and leakage of drilling strata, low rates of penetration (ROP). Thus, with the three-section casing program of early horizontal wells, it is difficult to continuously increase the ROP and reduce the drilling cost. In response, a theoretical analysis was carried out on reducing the intermediate completion cycles and optimizing the sealing section and the borehole size. And a transitional test of casing program optimization was performed. On these basis, ideas for casing program optimization were proposed and their feasibility was analyzed. The sealing section and the borehole sizes were optimized, and a two-section casing program was designed for slim boreholes in horizontal wells. The key drilling matching technologies were studied, including borehole trajectory control, optimization of customized drill bits and matching speed-up tools, and segmentation measure optimization for drilling fluids with strong inhibition and high-efficiency lubrication. The field application proved that the proposed technologies had a good application effect and they solved the “collapse and leakage coexist, with leakage above and collapse below” problems in long openhole sections. The ROP in each section was improved, and the drilling cycle was greatly shortened. The application suggests that the two-section casing program for slim boreholes is reasonable, and the drilling matching technologies dramatically increase the ROP and therefore can be applied in horizontal well drilling in Sulige Gas Field.