Experimental Study on the Acid-Etched Fracture Conductivity of Novel Nano Retarded Acid System

Abstract

The expansion of new energy construction, characterized by its scalability and cost-effectiveness, is increasingly integrated into the oil and gas industry, albeit still in the exploratory phase. Chinese oil fields predominantly employ continuous water injection methods, which incur substantial electricity consumption and costs. Embracing new energy sources for supply promises substantial reductions in electricity costs. However, the intermittent and unpredictable nature of wind and solar power generation does not align with the consistent and stable electricity demand required for continuous water injection, necessitating the exploration of novel water injection models compatible with new energy supplies. In pursuit of minimizing water injection electricity costs, this study proposes an intermittent water injection model grounded in the distinctive characteristics of new energy supply. During peaks of green electricity output surpassing production demand, "increased injection" is implemented, while during troughs of green electricity output falling below production demand, "reduced or halted injection" strategies are adopted. Insights derived from well test interpretations using shut-in pressure drop data guide the fine-tuning of water injection parameters. This transition shifts the water injection regime from the conventional "24-hour stable flow continuous water injection" to an "X hours injection/ 24-X hours shut-in intermittent water injection" approach. The feasibility of this model is comprehensively evaluated through real-time monitoring, engineering tests, and well test interpretations, assessing injection capacity, water absorption efficiency, reservoir characteristics, and productivity across the project lifecycle. A 5-month intermittent water injection trial was conducted across two injection-production well pairs in the low-permeability reservoirs of the Jilin oilfield. Three distinct intermittent water injection protocols were designed: "15 hours injection/ 9 hours shut-in", "13.3 hours injection/ 10.7 hours shut-in", and "12 hours injection/ 12 hours shut-in". The injection rates, set at 1.6 times, 1.8 times, and 2.0 times the rate of continuous water injection, respectively, were determined by these protocols. Trial outcomes demonstrate reasonable high-speed injection pressures, satisfactory injection volumes, intact reservoir conditions, a 2.5 % reduction in water cut, and a delay of over 1.5 % in natural decline. Calculations based on new energy generation costs reveal a reduction of over 60% in daily electricity expenses compared to continuous water injection methods. The successful field trial validates the feasibility of intermittent technology in low-permeability reservoirs, showcasing substantial savings in electricity costs and offering robust technical underpinning for the efficient development of such reservoirs.