彬长矿区低煤阶煤层气井的排采特征与井型优化

为研究我国西部侏罗纪低阶煤储层瓦斯的地面井排采特性及影响因素，以彬长矿区大佛寺井田煤层气井的地质资料、历史排采数据为基础，分析了该区块不同井型煤层气井的产水量、产气量的主要影响因素，并探讨了相关因素的主要控制机理。研究发现储层特性、水文地质条件是影响该区煤层气成藏的重要因素，在所研究的几种井型中，多分支井在该区有着良好的地面排采效果，其最高日产气量为16 582.3 m3，垂直井次之，而U型井则相对较差。排采数据显示井底流压与产气量呈指数关系，井底流压的减小，日产气量呈指数增加的趋势。在煤层气井不同排采时期，动液面高度对产气量的影响有着不同的作用规律，且对高产气阶段的影响更为显著。套压与产气量之间近似表现为线性变化的关系，但不同排采阶段二者线性关系的比例截然不同。在煤层气井的产气衰减阶段，多分支水平井的日产气量/累计产气量的比值与排采时间呈现为良好的E指数衰减关系，并以此构建了以日产量与累计产量之比和开发时间之间的关系为基础的煤层气井产能预测模型，拟合相关系数均高于0.848 2。

CBM production character and surface well selection in Binchang low rank coal field

In order to investigate on gas production characteristics and its influencing factors of Jurassic low rank coal reservoirs in the western China，In the current study，the gas production of different surface wells，the key factors and controlling mechanisms were analyzed based on the geological information of surface boreholes and historical gas production data.The results show that the reservoir properties and hydro-geological conditions are important key factors which influence on the gas productions in the Binchang Dafosi coalfield.For the selected surface wells，the horizontal multi-branches wells performs better in terms of gas production，the highest daily gas production is about 16 582.3 m3/d.The vertical well is the second good performer，while the U shaped well is relatively poor.The historical data of gas production show that there is an obvious exponential function relationship between the bottom pressure and gas productions.With the decrease of bottom pressure，gas production would increase following the exponential relationship.At the different period of gas production，the height of fluid surface has different effects on gas production.The influence is much more significant at high gas production periods.There is a linear relationship between the casing pressure and gas production，however，the proportion of the linear relation varies greatly at different drainage stages.Through the historical data of gas production，one exponential function relationship have been deduced from the data between the ratios of daily gas production and the accumulated gas production with drainage time.A gas production prediction model has been established and the fitting coefficients are higher than 0.848 2，which shows a high accuracy.