Experimental Insights Into Geometrical Parameter Effects on the Jet Cleaning Process in the Plug and Abandonment of Oil and Gas Wells

Abstract The plug and abandonment (P&A) operation is a critical phase in the lifecycle of oil and gas wells, aimed at permanently sealing wells to prevent fluid migration between hydrocarbon-bearing zones and surrounding formations. The primary objective is to establish secure barriers and prevent crossflow after abandonment. This process involves sequential steps, including accessing the annulus space behind the casing, cleaning the target area, and installing cement plugs. Effective jet cleaning is crucial to ensure proper cement-casing bonding and avoid contamination. The efficiency of jet cleaning depends on various factors, including well geometry (e.g., inclination, nozzle-casing distance, nozzle-perforation diameter ratio) and fluid properties (e.g., rheology). This study experimentally investigates horizontal jets in a miscible medium to understand jet cleaning dynamics during P&A operations. Using a setup that mimics perforated casing structures, fluid is injected horizontally into a tank containing a miscible ambient fluid. Key parameters analyzed include injection velocity, perforation diameter, and ambient fluid rheology. Results show that smaller perforation diameters increase the mixing index, indicating higher mixing levels, while non-Newtonian ambient fluids reduce the mixing index. These findings provide insights for optimizing jet cleaning in P&A contexts.