School of Resources and Geosciences, China University of Mining and Technology MOE Key Lab of Coal Bed
Methane Resources and Reservoir Formation Process

为了分析排采制度对于煤层气井产能的影响,以沁水盆地柿庄南区块煤层气垂直井的实际排采数据为基础,对比了不同排采速率下煤层气井的产能,并对不同排采阶段的排采制度进行了分析。结果表明:排采速率过快,会减小排采半径,引起速敏效应,致使裂缝闭合,降低煤层气井的产能。基于排采速率分析,煤层气井排采过程分3个阶段:动液面下降到煤层顶板附近为初始产气阶段,此阶段依地层的供液能力使动液面缓慢下降,下降速率以5~10 m/d为宜;控制井底流压的稳压波动阶段,控制套压稳定在0.2~0.4 MPa,此阶段产气量不稳定且持续时间较长;降压提产阶段,在产气量有明显下降时,动液面稳定下降到煤层底板,套压降低,最终稳定在约0.02 MPa,此阶段煤层气井的产气量会有所上升,发挥最大的产气潜能。

In order to analyze the drainage system's influence the production capacity of the coalbed methane well, based on the actual drainage data of the coalbe d methane vertical well in Shizhuang South Block of Qinshui Basin, the production capacities of the coalbed methane wells under different drainage rate were compared and an analysis was conducted on the drainage system in different drainage stage. The results showed that the fast drainage rate would reduce the radius of the draina ge, would cause a quick sensitive effect, would make the crack closed and would reduce the production capacity of the coalbed methane well. Based on the drainage ra te, the drainage process of the coalbed methane well could be divided into three stages. An initial gas production stage when the dynamic liquid level dropped down to t he seam roof nearby could make the dynamic liquid level slowly drop with the liquid supply capacity of the strata and the drop rate would be 5~ 10 m/ d suitably. A sta ble pressure waving stage which control the flow pressure of the well bottom could control the casing pressure stabilized within0. 2 ~ 0. 4 MPa and the gas production at the stage would cause unstable up and down waving and the unstable time would be long. At the pressure reduction and production increasing stage, when the gas p roduction was obviously reduced, the dynamic liquid level would steadily drop to the seam floor, the casing pressure would be reduced and finally the pressure would b e stabilized around 0.02 MPa. The gas production of the coalbed methane well at this stage would be increased anyhow and a max gas production potential would be p layed.

国家科技重大专项资助项目(2011ZX05034)；国家自然科学基金重点资助项目(41272178)；江苏省“青蓝工程”；江苏高校优势学科建设工程资助项目(PAPD)；