Optimization and practice of drilling and completion technology on increasing of ROP and efficiency in ZS block

The gas reservoirs in ZS block is dominated by lithology of rhyolite, tuff and volcanic breccia and are characterized by high hardness and abrasiveness, strong heterogeneity, well- developed fractures and rich acidic fluids. In the offset well, the average ROP is 1.49 m/h, and the average drilling cycle is 137.12 d. Lost circulation and casing corrosion always occur. In addition, the cement ring seal fails during stimulation and production, resulting in wellhead pressure. The well structure was optimize through the technology of one-trip drilling. The non-planar tooth drill bits with good compatibility with the formation and the water-in-oil drilling fluid system were selected. The completion method was optimized according to the reservoir characteristics. The factors affecting CO₂ corrosion were analyzed to optimize the casing types. The self-repairing cement was used to prevent wellhead pressure. The average drilling cycle is reduced to 69.82 d. The average ROP in the third spud is 3.11 m/h, which is 108.5% higher than that of the offset well. There are no lost circulation during the drilling process and no annular pressure after cementing operation.