Self-Granulating Thermoplastic Elastic Particles for Fracture Conformance Control in Ultraharsh Reservoirs: Laboratory Investigation and Field Application

To address the challenges in fracture conformance control using polymer particles in ultraharsh reservoirs, we developed novel self-granulating thermoplastic elastic particles (SGTEPs). The innovation was driven by the complexity of the traditional polymer particle preparation process and the difficulties in balancing injectivity and conformance control performance. Polyvinyl alcohol (PVA) served as the particle skeleton, and millimeter-scale SGTEPs were prepared in situ by incorporating a hydrophobic modifier (HM) and a cross-linking agent (glutaraldehyde, GA) into an aqueous phase. The morphology, mechanical properties, and high-salinity thermal stability of SGTEPs were investigated using scanning electron microscopy (SEM), texture profile analysis (TPA), and thermal aging tests at 130°C. Particle size adjustability was demonstrated through the modulation of HM content and stirring speed. TPA highlighted SGTEPs’ superior elasticity and resilience. SGTEPs underwent thermal plasticization in ultrahigh-salinity brines (22.0 × 104 mg/L, Ca²⁺ + Mg²⁺ = 1.2 × 104 mg/L) and crude oil at temperatures up to 130°C, retaining exceptional mechanical properties even after 60 days of aging. Open fracture models were designed to investigate the effect of particle size, injection rate, and particle concentration on SGTEPs’ migration performance. Coreflooding experiments indicated effective migration and conformance control performance of SGTEPs, with appropriate matching coefficients of 1.45 and 1.50. The particles exhibited an “aggregation → accumulation → deformation migration” effect, with particle concentration linearly affecting differential pressures. After high-temperature aging, SGTEPs could efficiently plug the open fracture, achieving breakthrough pressures up to 1860 kPa. Field application results showed significant improvements in oil production and water-cut reduction. Specifically, the daily oil production of Well TK466 increased from 4.6 tons to 15.5 tons, with an incremental oil production of 252.5 tons per well and a reduction in average water cut from 90% to 82.7%. The newly developed SGTEPs offer a fresh perspective on material design for enhancing conformance control in ultraharsh condition reservoirs with large fractures and void spaces. The novel particles demonstrated excellent thermal stability, elasticity, and migration and plugging performance, making them a promising solution for improved oil recovery in challenging reservoir conditions.