基于测井参数的煤层含气量预测模型与应用
Application and Prediction Model of Coalbed Methane Content Based on Logging Parameters
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摘要: 煤层含气量是决定煤层气开发效果的重要参数,准确确定煤层含气量是煤层气勘探开发研究的一个关键问题。以沁水盆地东南部沁南东区块为依托,通过煤层含气量解吸试验和煤层气钻孔测井资料统计,分析了煤层含气量与测井参数之间的关系,选择了有效埋深的对数、体积密度、自然电位、深侧向电阻率与浅侧向电阻率比值、微球形聚焦电阻率的对数、声波时差与自然伽马和补偿中子乘积的比值等6个参数作为BP人工神经网络预测模型的基本特征量,建立了基于测井参数的煤层含气量BP人工神经网络预测模型,并对模型进行误差分析和应用结果对比分析。结果表明:基于测井参数的BP人工神经网络预测模型具有极强的非线性逼近能力,能真实反映煤层含气量与测井参数之间的非线性关系,预测结果与实测结果之间误差小,相对误差一般小于10%,采用测井参数预测煤层含气量具有较好的应用前景。Abstract: Coalbed mathane content was an important parameter to determine the development effect of coalbed methane. Accurate determination of the content w as a key problem for coalbed methane exploration and development research. Taking east Qinnan Block in southeast Qinshui basin as the target area, the relationship between coalbed mathane content and logging parameters were analyzed, based on gas desorption experiment of mathane content and coalbed methane drilling loggin g parameters. Six parameters were chosen as the basic characteristic quantities of BP artificial neural network prediction model, such as logarithm of effective buried d epth, volume density, spontaneous potential, ratio of deep lateral resistivity and shallow lateral resistivity, logarithm of microspherically focused resistivity, ratio of acous tic time difference and the product of natural gamma ray and compensated neutron. The BP artificial neural network prediction model for coalbed methane content was built. The model' error and results contrast of its application were analyzed. The results showed that BP artificial neural network prediction model based on logging para meters had strong nonlinear approximation ability and could actually reflect the nonlinear relationship between coalbed methane content and logging parameters. The e rror between predicted results and measured value was small, with the relative error generally less than 10%. There would be a good application prospect in using loggi ng curves to predict gas content of coal seam.