Guizhou Research Center of Coal Bed Methane and Shale Gas Engineering Technology, Guiyang , China

为了降低超压煤层在解吸前排采过程中的伤害，需确定煤层气井超压煤层的临界解吸压力，便于进行精细化排采控制，通过探讨了煤层超压的识别方法及对排采控制的影响，针对贵州松河区块多煤层超压煤层气井的地质参数、生产数据，建立该区块的超压煤层的临界解吸压力的数学模型。结果表明：超压煤储层含有较多的游离气，导致超压煤层的临界解吸压力与兰氏方程的计算值差距较大；超压储层能量高，排采过程中压力波动，发生贾敏效应的可能性较高；根据建立的数学模型计算临界解吸压力，应用于超压煤层气井的排采控制，见套压前的返排率达到37.1%，有效避免了排采控制不合理造成的煤层伤害。通过研究超压煤层的临界解吸压力，为该类煤层解吸前的精细化排采控制提供指导。

In order to reduce the gas drainage damage by the overpressure seam before desorption,it was necessary to determine the critical desorption pressure of the coalbed methane well in the overpressure seam so as to make a fine gas drainage control. The paper had a discussion on the overpressure identification method of the seam and the influences to the gas drainage control. According to the geological parameters and gas production data of the overpressure coalbed methane wells in multi seams of Songhe Block in Guizhou, the numerical model of the critical desorption pressure in the overpressure seam in the block was established. The results showed that the overpressure coal reservoir with many free gases could cause a big difference between the critical desorption pressure of the overpressure seam and the calculation value of the Langmuir’s equation. The overpressure coal seam would have a high energy and the pressure fluctuations occurred from the gas drainage process would have a high possibility to cause a Jamin Effect. The critical desorption pressure calculated by the established mathematical model could be applied to the gas drainage control of the overpressure coalbed methane well. Before the casing pressure occurred, the flow back rate was up to 37.1% and could effectively avoid the coal seam damage caused by the irrational gas drainage control. The study on the critical desorption pressure of the overpressure seam could provide the guidance to the fine gas drainage control of the coalbed methane well in this type coal seam before desorption.