浅层页岩气井间压窜影响因素与防治优化

Influencing factors and prevention optimization of shallow shale gas inter-well frac-hits

  • 摘要: 昭通浅层页岩气田是国内第一个中浅层页岩气开发示范区,主体埋深在1 000~2 200 m,因产建不同步、区域断裂系统发育、水平应力差小等原因,新井压裂过程中频繁出现井间干扰现象,呈现压窜范围广、产量恢复难度大等一系列难题;“压裂井—生产井”之间的压窜主要表现为“响应快、复产难、多频次”的特点,对被压窜井的统计结果来看,投产时间越长的井压窜治理后的恢复程度越低,因此有必要开展井间压窜影响因素分析与防治措施。对昭通浅层页岩气田全部压窜的32井次的工程、地质条件动静态参数进行了梳理,通过训练随机森林模型,评估了地质工程参数对压窜现象的影响程度,明确井间压窜主控因素排序为井间距、施工强度和母井投产时间。结合数值模拟方法,提出了子母井最优井间距为450 m;正交设计模拟结果显示,母井投产后被压窜后总是受到负面干扰,随着投产时间越长,母井受到的干扰比例从6.3%增加到35%;而当母井投产1年内、子母井的井距大于400 m后,子井受到正向干扰,随着井距增大干扰程度变化范围为2.5%~8.6%。提出的井距优化措施支撑了昭通浅层页岩气开发方案的井位部署和压裂参数优化,证明了该研究成果的可能性。

     

    Abstract: The Zhaotong shallow shale gas field is the first pilot demonstration area in China for medium to shallow shale gas development, with main burial depths ranging from 1 000 to 2 200 m. Due to asynchronous production and infrastructure construction and a small horizontal stress difference in the regional fault system, inter-well interference frequently occurs during the fracturing of new wells. This presents a series of problems such as extensive frac-hits and difficulty in restoring production. The frac-hits between fractured wells and producing wells are mainly characterized by fast response, difficult production recovery, and multiple occurrences. Statistical analysis of affected wells showed that the longer the production time, the lower the recovery rates after the implementation of frac-hits control measures. To address these challenges, it is imperative to analyze the influencing factors of inter-well frac-hits and propose preventive measures. The study comprehensively reviewed the dynamic and static parameters under the engineering and geological conditions from 32 wells experiencing frac-hits in the Zhaotong shallow shale gas field. A random forest model was trained to evaluate the influence of geological and engineering parameters on frac-fits. The main controlling factors were identified as well spacing, construction intensity, and the production time of the parent well. Numerical simulations suggested an optimal parent-child well spacing of 450 m. Orthogonal design simulations revealed that parent wells consistently suffered negative interference after experiencing frac-hits, with the interference ratio increasing from 6.3% to 35% as the production time extended. When the parent-child well spacing exceeded 400 m within the first year of parent well production, child wells experienced positive interference, and the interference degree ranging from 2.5% to 8.6% as well spacing increased. The proposed well spacing optimization strategy supports well location deployment and fracturing parameter optimization in the Zhaotong shallow shale gas field, validating the research results.

     

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