Integrated Diagnosis of plugging in Western Sichuan Sour Gas Reservoirs: From Plugging Mechanisms to Mitigation Strategies

Abstract Since their commissioning in 2023, eighteen sour gas wells in the West Sichuan Gas Field have experienced over forty significant plugging incidents, severely compromising field productivity. This study employed multidisciplinary experimental methods to analyze plugging mechanism. Spearman correlation analysis identified plugging influencing factors, enabling recognition of plugging characterization and optimal unplugging timing. An optimized plugging removal fluid system was developed alongside a novel Quantitative Plugging Degree (QPD) assessment methodology, forming the basis of a targeted well mitigation strategy. Key findings reveal: (1) Three distinct plugging types—organic (predominantly long-chain alkanes and benzene compounds), inorganic (iron sulfides/oxides, BaSO₄, and clays), and composite plugging; (2) Acid demonstrates superior efficacy, with initial plugging diagnosis indicated at incremental pressure decline rates ≥ 0.02 MPa/d, necessitating intervention before rates exceed 0.2 MPa/d; (3) The QPD method enables precise plugging location identification, facilitating optimized mitigation strategy. Implemented in Wells P5 and X1, this classified mitigation strategies significantly extended unplugging validity periods with demonstrable field success.