A Novel Approach to Predicting Caprock Integrity for CCUS Using Drill Cuttings

Abstract Leakages and caprock integrity are major challenges in Carbon Capture, Utilization, and Storage (CCUS), as caprock acts as a sealing layer that traps CO2 within subsurface formations, preventing leakage to the surface. Caprock integrity is determined through fracture gradient calculations validated by Leak Off Test (LOT) data and rock mechanical tests on conventional core samples. However, core and LOT data specific to the caprock are often unavailable, leading to fracture gradient being estimated solely through empirical equations without proper validation. This study aims to introduce a novel approach utilizing drill cuttings, particularly cuttings from drilling events (sloughing), by measuring penetration depth under predetermined loads and correlating the results with LOT data. The resulting correlations can be used to predict LOT in wells lacking such data by leveraging available drilling cuttings. Testing was conducted on samples from well PHE-AAA. The results provided penetration depth data, which was then correlated with LOT data. The derived equations were used to predict LOT values for wells PHE-SSS and PHE-YYY. The substituted equations yielded LOT values of 15.6 ppg for well PHE-SSS and 17.7 ppg for well PHE-YYY. The substituted results showed an average accuracy of 95% compared to available LOT data. The advantage of this study lies in introducing a novel approach to predicting a key parameter of caprock integrity—specifically the fracture gradient—by utilizing drill cuttings or sloughing cuttings. Traditionally, such analyses have relied on LOT and core data, which are not always available. This method also facilitates mud weight estimation during drilling operations and has significant implications for CCUS applications by helping to reduce the risk of CO2 leakage.