Development patterns and strategies for offshore high-intensity steam stimulation with large well spacing

Abstract

Offshore heavy oil resources are abundant, driving a strong demand for thermal recovery development. Over years of practice, steam stimulation has been successfully applied to thin layer heavy oil, edge and bottom water heavy oil, and extra heavy oil. Accurately understanding the flow characteristics and development patterns of steam stimulation in offshore heavy oil reservoirs with large well spacing is essential for designing, adjusting, optimizing, and enhancing production and efficiency in thermal recovery development plans. Precise evaluation of thermal recovery effectiveness and development status is also critical. The study focuses on the quantitative characterization of the actual thermal field distribution and the steam override phenomenon in the thermal fluid zone, aiming to accurately depict changes in the heating radius. It summarizes the patterns and development experiences related to production decline, validity period, production pressure difference, and associated gas in offshore steam stimulation with large well spacing. From this analysis, three decline stages and average decline rates of offshore steam stimulation are identified. Based on these findings, the study proposes a development strategy for large well spacing steam stimulation in offshore heavy oil reservoirs, using reservoir numerical simulation methods for prediction. The study recommends horizontal wells for steam injection, especially in edge water reservoirs, with well placement over 150 to 200 meters from the oil-containing boundary. High steam dryness and large-cycle injection rates are suggested to enhance formation heat utilization efficiency. It is also found that offshore large well spacing thermal recovery has an average effective period of 329 days, with a first-cycle average monthly decline rate of 13.5%. The optimal production pressure difference for wells ranges from 3.5 to 5.0 MPa. The results offer valuable insights for scaling up offshore heavy oil thermal recovery development.

Keywords

• |offshore heavy oil reservoirs|steam stimulation|decline patterns|development patterns|development strategy