废停页岩气井改造同轴水平井闭式循环采热方法研究

Research on the Closed-Loop Heat Extraction Method of Transforming Abandoned Shale Gas Wells into Coaxial Horizontal Wells

摘要: 本研究根据四川盆地焦石坝区志留系龙马溪组泥页岩储层及水平井的特征，构建了单井同轴水平井闭式循环采热模型。结合有限元模拟探究了不同系统的采热效果，分析了井身结构与注采参数的影响规律。研究表明，在水循环速率1500 m³/day，注入温度20℃及水平段长度1500 m条件下，单井同轴水平井采热运行初期井口水温达57.84℃，采热功率为2746.29 kW。在循环采热10年后，单井同轴水平井井口水温下降至33.51℃，采热功率下降到980.43 kW。水循环速率的增加会降低井口水温，但会提高采热速率；注入温度的增加可以提高井口水温，但会降低采热速率；水平段长度增加能够有效提高井口水温和采热速率。上述研究结果可为未来矿场应用提供一定的理论指导。

Abstract: Based on the characteristics of the Silurian Longmaxi Formation shale reservoir and horizontal wells in the Jiaoshiba area of the Sichuan Basin, this study constructed a closed-loop heat extraction model for a single coaxial horizontal well. By employing finite element simulations, the heat extraction performance of different systems was investigated, and the influence patterns of wellbore structure and injection-production parameters were analyzed. The research demonstrates that under the conditions of a water circulation rate of 1500 m³/day, an injection temperature of 20˚C, and a horizontal section length of 1500 m, the wellhead temperature of the single coaxial horizontal well reaches 57.84˚C, with a heat extraction power of 2746.29 kW during the initial operation phase. After 10 years of circulation heat extraction, the wellhead temperature decreases to 33.51˚C, and the heat extraction power drops to 980.43 kW. An increase in water circulation rate reduces the wellhead temperature but enhances the heat extraction rate, while an increase in injection temperature raises the wellhead temperature but lowers the heat extraction rate. Moreover, increasing the horizontal section length effectively improves both the wellhead temperature and the heat extraction rate. These findings provide theoretical guidance for future field applications.