煤层气井排采初期井底流压动态模型及应用分析

摘要

Bottomhole flowing pressure is one of the key parameters that affect gas production of coalbed methane (CBM) wells, how to control the change of the bottomhole flowing pressure to increase the gas production of coalbed methane well is a problem worth considering. Based on the radial seepage theory, two dynamic prediction models are established, one is under the condition of infinite outer boundary with inner boundary of regular pro-duction and the other is non-regular production, and the change law of the bottomhole flowing pressure is finally revealed under the condition of regular production and non-regular production in the early stage of the drainage. Results show that the flowing bottomhole pressure reduces with the drainage time by the negative logarithm law under the condition of regular production and the flowing bottomhole pressure reduces with the displacement by the negative linear law in the condition of non-regular production. The prediction and analysis of the prediction model were applied in 6 CBM wells of Shizhuangnan block in the early stage of the drainage. It turns out that the predicted result fits the actual situation well.%井底流压是影响煤层气井产气量的关键参数之一，如何控制井底流压的变化来提高煤层气井产气量是值得考虑的问题。基于平面径向渗流理论，建立了外边界无限大，内边界定产与非定产条件下井底流压2种动态预测模型，揭示煤层气井排采初期在定产条件和非定产条件下井底流压变化规律。研究结果表明：在定产条件下井底流压随排采时间的增加按负对数函数规律降低；非定产条件下井底流压随排水量的增加呈负线性函数规律降低。利用预测模型对沁水盆地柿庄南区块6口煤层气井排采前期的生产动态进行预测分析，预测结果与实际结果拟合程度较好。