海上稠油资源丰富，热采开发需求大，经过多年实践，实现了对薄层稠油、边底水稠油和特—超稠油的蒸汽吞吐开发。准确认识海上稠油油藏大井距蒸汽吞吐的渗流特征和蒸汽吞吐开发规律，进而对热采开发效果和开发状况准确评价，成为海上稠油热采开发方案设计、调整、优化和增产增效的关键。通过对热液区实际温场分布和蒸汽超覆现象定量化表征的研究，表征加热半径变化，总结海上大井距蒸汽吞吐的产量递减、有效期、生产压差、伴生气的规律和开发经验，确定了海上蒸汽吞吐的3个递减阶段和平均递减率。在此基础上，通过使用油藏数值模拟方法进行预测，提出了海上稠油油藏大井距蒸汽吞吐的开发策略。海上大井距蒸汽吞吐型开发推荐水平井，边水油藏在距离内含油边界150~200 m以上布井，采用高干度、大周期注入量提高地层热利用率，海上大井距热采平均有效期为329 d，第一周期平均月递减率为13.5%，生产井的合理生产压差介于3.5~5.0 MPa。研究结果对海洋石油稠油热采规模化开发具有一定的指导意义。

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.