多层次模糊评价模型在低煤阶煤层气区块优选中的应用——以澳大利亚东部A区块为例

相比于中高阶煤层气，低煤阶煤层气具有煤岩煤化作用低、含气量低、灰分含量高以及储层物性好等特点，针对于低煤阶煤层气区块的优选研究对于降低开发成本、促进产业发展等具有重要意义。以澳大利亚东部地区的低煤阶煤层气区块为研究对象，应用多层次模糊数学思路，结合区块低煤阶煤层气特征，优选累计厚度、含气量、灰分含量、可采储量、孔隙度、渗透率、含气饱和度、临界解吸比和原始地层压力作为评价指标，建立低煤阶煤层气的开发效果多层次模糊评价模型。在此基础上，结合评价指标权重系数与研究区三维地质模型构建低煤阶煤层气开发效果评价参数。以稳定期日均产气量3万m3、0.6万m3作为衡量标准，确定研究区的开发效果评价参数门限值为0.507和0.317，进行研究区开发有利区划分，实现基于多层次模糊评价模型的低煤阶煤层气区块开发有利区优选中的应用。在实际应用中，高中低产区内的已开发井的单井产气量与优选结果高度吻合，表明多层次模糊评价对于低煤阶煤层气有利区块优选具有很好指导意义。

Application of multi-level fuzzy evaluation model to the selection of favorable block for low rank CBM: a case study on Block A in eastern Australia

Compared with middle and high rank CBM, low rank CBM is more advantageous with low coalification of coal rocks, low gas content, high ash content and good reservoir physical properties.The selection of low rank CBM blocks is of great significance to decrease CBM development cost and promote the development of CBM industry.The low rank CBM block in eastern Australia was taken as the study object.According to the multi-level fuzzy mathematical thinking, combined with the characteristics of low rank CBM in this block, cumulative thickness, gas content, ash content, recoverable reserves, porosity, permeability, gas saturation, critical desorption ratio and original formation pressure are selected as the evaluation indexes to establish the multi-level fuzzy model for evaluating the development results of low rank CBM.Then, based on the weight coefficient of evaluation index and the 3D geologic model of this block, development result evaluation parameters of low rank CBM are constituted.The thresholds of development result evaluation parameters of this block are determined as 0.507 and 0.317 by taking the average daily gas production in the stable period of 30×103 m3 and 6×103 m3 as the yardstick, and accordingly the favorable development areas in the this block were determined.Thus, multi-level fuzzy evaluation model is successfully applied to the selection of favorable development areas in low rank CBM blocks.In the actual application, the single-well gas production of developed wells in high, middle and low yield zones are highly accordance with the selection results.And it is indicated that multi-level fuzzy evaluation plays a guiding role in selecting the favorable blocks of low rank CBM.