澳大利亚博文盆地薄煤层含气量测井评价方法及应用

以澳大利亚博文盆地为例,利用煤组的地质、测井及大量煤心实验分析数据,开展薄煤层含气量预测模型参数优选,采用回归分析法、等温吸附法及等温吸附校正法,分析含气量与固定碳、地层温度、压力、埋深及测井曲线之间的关系,建立了3个含气量评价模型,并进行了精细误差分析和方法优选。结果表明,光电吸收截面指数、补偿密度测井曲线和受围岩岩性影响小的地层温度、压力、埋深等属性参数适用于薄层测井解释,在薄煤层含气量评价中应用效果好。基于上述参数建立的3种评价模型中,等温吸附校正法含气量预测值与实测值吻合度高,适用于薄煤、泥、砂互层的地层特征;回归分析法可作为辅助模型用于验证未校正的等温吸附法在含气量大于20m3/t时误差较大,具有局限性。

Application of the Log Evaluation Method of Gas Content in Thin Coal Seam from Bowen Basin of Australia

In order to solve the problem in accurately evaluating the gas content of thin coalbeds,based on the geology,loggings and large number of core experimental data of Bowen basin,Australia,combining with the relationship between gas content and fixed carbon,formation temperature,pressure,depth and logging curves,three gas content evaluation models have been established by optimizing model parameters and utilizing regression analysis method,isothermal adsorption method and isothermal adsorption extension method.Additionally,error analysis and method optimization have been conducted.The results show that photoelectric absorption crosssection index log,compensated density log and parameters which are affected little by surrounding rock lithology,such as formation temperature,pressure and depth etc,suit for thin reservoir logging evaluation and achieve better results in gas content prediction of thin coalbeds.Among three evaluation models,which were established on the basis of mentioned above parameters,the isothermal adsorption extension model is more suitable for interbedded formation of thin coalbed,mudstone and sandstone,because the predictive value of gas content of this method matches well with the measured value.Regression analysis method can be used as an auxiliary model for verification.However,the original isothermal adsorption method has relatively large error when the gas content is larger than 20 m3/t.