Borehole Structure Optimization and Drilling Speed-up Technology in the East China Sea

In order to save the cost of exploration and development in oil and gas fields of the East China Sea, reduce the economic development threshold of new oil and gas fields, increase the rate of penetration (ROP), and achieve the purpose of cost reduction and efficiency increase in drilling, there are many drilling challenges in the 12-1/4 in borehole in the East China Sea, such as long open hole section, multiple inter-layers, poor drillability, and the borehole instability, which leads to difficulties in tripping, long reaming time, well-bore collapse and jamming of a drilling tool, etc.. The surface borehole size is further optimized, deep well structures are simplified, and motor with equal wall thickness, hydraulic oscillating screw, integrated compound speed-up tool and other drilling speed-increasing tools have been innovatively introduced in order to meet these challenges. Through the field application of the research results, the effect of cost reduction and efficiency increase is significant considering, the average ROP of the entire well in 2018 is 55% higher than the end of the 12th Five-year Plan, and the deep layer has increased by 72.2%. Application shows that this technology effectively guarantees the low-cost, safe and efficient exploration and development of oil and gas wells and it has a broad application prospects in the marginal field and old oilfields development as well as reduction of exploration well cost.