Pilot test on the ROP-improvement BHA of vertical drilling tool & screw rod with equal wall thickness: A case study on Well Keshen A in the high-steep structure of Kuqa piedmont area

The wells in Kuqa piedmont area suffer the problems of difficult hole deviation control, bit swirling and drilling tool stick-slip caused by high-steep structure, high conglomerate content and formation anisotropy. In order to solve these problems effectively, Tarim Oilfield applies the bottom hole assembly (BHA) of “vertical drilling tool + screw rod with equal wall thickness” for rate of penetration (ROP) improvement in Kangcun Formation and Jidike Formation of supra-salt formation with high conglomerate content in Well A of Keshen . The positive displacement drill with high output power, stable performance and strong complex situation treatment ability suitable for Kuqa piedmont area is selected, and its matching problem with the vertical drilling tool is solved based on the optimization design of drill string mechanics and hydromechanics. In the process of actual drilling, the available weight on bit (WOB) is high, the torque is stable and the ROP is high, so hole deviation is controlled effectively and abnormal drilling states are improved, such as bit swirling and drilling tool stick-slip, so as to reach the target of WOB liberation, bit protection and rock breaking efficiency improvement. Compared with the same hole section in the same horizon of its neighboring well, its ROP and single-trip drilling footage are increased by 75%-262% and 51%-134%, respectively. It is verified that the BHA of “vertical drilling tool + screw rod with equal wall thickness” is feasible to the ROP improvement in high-steep conglomeratic formation of Kuqa piedmont area, so it can be applied and popularized in the supra-salt formation in the wells of Kuqa piedmont area in a large scale.