Comparing Organic Salt-Based and Oil-Based Drilling Fluids in Qinghai Shale Oil Wells: A 2022 Field Pilot Study on the Same Platform

In 2022, a field pilot study was conducted on a shale oil platform in the Yingxiongling Block, Qinghai Oilfield, China, to evaluate the feasibility of replacing conventional oil-based mud (OBM) with an organic salt-based mud (OSBM) under high mud weight and wellbore instability conditions. The platform consisted of 8 horizontal wells drilled in 2 phases, with 4 wells using OBM and 4 using OSBM. Identical drilling tools and parameters were applied across comparable intervals to ensure a valid performance comparison. The results showed that both drilling fluid systems maintained excellent borehole stability and clean hole conditions, with no incidents of differential sticking or sloughing. However, OSBM consistently delivered superior drilling efficiency. In 8½-inch hole sections using a rotary steerable system (RSS) without positive displacement motors (PDM), the OSBM wells achieved an average rate of penetration (ROP) more than twice that of OBM wells. Even after PDMs were introduced to the OBM wells, OSBM still required fewer trips and maintained higher ROP. Overall, OSBM reduced the total drilling time by 18.56% compared to OBM, despite complex shale formations and high-density fluid requirements. This study demonstrates that OSBM is a reliable, high-performance, and environmentally advantageous alternative to OBM in demanding shale drilling operations.