Customized Plugging Strength: An Advanced Technique for Chemical Water Shut-Off in Viscous Crude Reservoirs

Abstract High water cut is a major challenge affecting the development of heavy oil reservoirs, particularly prominent in thermal recovery. Multiple factors such as reservoir development duration, heterogeneity, oil-water flow ratio, well pattern type, and production parameters influence water cut rise, and the control technologies must be comprehensively consideredfor these factors. How to accurately determine and select appropriate water shut-off strategies is a key issue for the efficient development of heavy oil fields. Firstly, it used the independently developed Intelligent Diagnosis Technology for Water Flooding Status in Complex Reservoirs (FLIISTM) to quantitatively identify and calculate dominant seepage channels. Secondly, it optimized customized plugging strengths and developed different chemical agents such as thermosensitive reversible gels and high-temperature-resistant foaming agents.At last it analyzed water invasion patterns by combining water breakthrough time and water cut rising rate to construct a step-by-step plugging design workflow. The thermosensitive reversible gel was an intelligent responsive gel system, which existed as a low-viscosity fluid below 80℃ and forms a colloid above 80℃. After gelation, its viscosity exceeded30,000 mPa·s, and the gel strength reached grade H, which can withstand temperatures above 180℃. The plugging rate exceeded 99.7% after core injection and gelation, indicating its strong plugging ability under thermal recovery conditions. Meanwhile, the product formula can be adjusted according to different reservoir temperatures to better adapt to the reservoir. The thermo-stable foaming agent had the properties of high temperature and salt resistance, with a temperature resistance of up to 350℃. Its resistance factor at 250℃ was greater than 30, which can inhibit gas channeling in multiple cycles of thermal recovery and improve development effects. Field applications show that in the first-round measures for Well A1, the initial water cut decreased from 74% to below 5%, the peak daily oil production reached 53.9 m³, cumulative oil increase was 4,100 m³, and the effective period lasted approximately 5 months. The thermosensitive gel alleviated inter-well gas channeling interference during single-well heat injection, increasing oil production by 40%-60% after thermal recovery.