PFW水驱气顶油藏二次采气的可行性研究

Feasibility study of secondary gas production for PFW water-drive gas-cap reservoirs

初期不合理的开采方式会造成水驱气藏地层水的过早水侵,使得大量天然气被封闭而无法采出。通过大量排水降低水封闭气区的地层压力,使封闭气变为可流动的气体,在技术和经济上是可行的。基于三维三相模拟模型,评价了不同二次采气方案的开发效果。模拟结果表明,大于水侵速度的排水量有助于提高气藏的最终采收率,但是要受到地面的水处理设施及经济因素的制约。水平井在开发水驱气藏,尤其是底水气藏方面,具有明显的技术优势。对于常压、中等埋藏深度(小于3000m)的水驱气藏,含水层中溶解气的释放只能使地层压力的下降速度减缓,并不会对气藏的开发效果产生显著影响。研究结果为改善水驱气藏的开采效果提供了新的技术思路。

Irrational production fashions during initial stage may cause premature water invasion in water drive gas reservoirs,thus resulting in a great deal of gas being trapped and incapable of being produced.It is feasible technologically and economically to change trapped gas into flowing gas through reducing the formation pressure of water sealed areas by large amount of water drainage.Based upon the three-phase three-dimensional simulation model,the development results of various secondary gas recovery were evaluated.The simulation results indicate that massive water displacement higher than formation water invasion speed will be beneficial for enhancing ultimate gas recovery factor,whereas it should be restricted by surface water processing facilities and economic factors.Horizontal well has distinct technical advantages in development of water drive gas reservoirs,especially bottom water-drive reservoirs.As for water drive gas reservoirs with normal formation pressure and moderate burial depth(not more than 3000 meters),the release of dissolved gas in the aquifer can only slow down the declining rate of formation pressure,and it won't have any remarkable influences on development results of gas reservoirs.The research results can provide us a new technical thinking for improving production results of water-drive gas reservoirs.