Summary Horizontal drilling operations targeting tight hydrocarbon reservoirs within the Sichuan Basin, prominently typified by the Shaximiao tight gas formation, persistently encounter the dual challenges of wellbore instability within hard brittle mudstones alongside elevated torque and drag across extended horizontal sections. In this context, traditional experience-based selection models often fail to strike an optimal performance balance between high-performance water-based mud (HPWBM) and oil-based mud (OBM). To resolve the technological bottlenecks associated with substituting OBMs, it is imperative to establish a quantitative decision-making framework. Such a framework must coordinate heterogeneous objectives, specifically inhibition, fluid loss control, and lubrication, rather than relying on the simplistic accumulation of individual additives. Based on formation characteristics, specific engineering criteria were established focusing on “four strengths and two lows”: strong inhibition, fluid loss control, lubrication, and stability, coupled with low water activity and fluid loss. Subsequently, an entropy-weight (EW) method and technique for order preference by similarity to an ideal solution (TOPSIS) multiattribute decision-making model was introduced to quantify key performance indicators, objectively optimizing five candidate systems by bridging microscopic mechanisms with macroscopic performance. Laboratory evaluation identified System 5 as the optimal formulation, subsequently demonstrating superior engineering adaptability during field trials on the JQ527 platform. Notably, the average hole enlargement rate in the horizontal section was maintained at 4.99%. This figure is marginally superior to the 7.59% recorded for OBMs and represents a significant improvement over the 22.7% observed with early-stage water-based muds (WBMs) on adjacent platforms. Crucially, the average horizontal drilling cycle with this optimized system was reduced to approximately 17.78 days. This represents a 58.15% reduction compared with the 42.49 days required for early-stage WBMs, closely approaching the operational efficiency of OBMs (16.14 days). Concurrently, the comprehensive drilling fluid cost per well decreased by 37.5% relative to OBMs, achieving a dual breakthrough in both technical feasibility and economic viability. These results robustly confirm that HPWBMs, optimized via the quantitative EW/TOPSIS method, possess the potential to replace OBMs in complex tight gas reservoirs. Furthermore, the universal applicability of the proposed methodology was systematically validated through its successful extension to two additional complex geological scenarios, including the Longmaxi deep shale formation and the Dengying high-temperature carbonate formation. Thus, this study provides a reproducible scientific paradigm for the environmentally sustainable and cost-effective development of unconventional hydrocarbon resources.
Xie et al. (Wed,) studied this question.