煤层气开发地质单元划分与应用实践

Division and application of development geological units for coalbed methane

  • 摘要: 根据煤层气生产潜力,结合开发地质条件划分煤层气开发地质单元,能为开发工艺选型提供重要支撑。通过分析各项地质储层参数对煤层气开发效果的影响,建立了评价参数体系,确定出主要研究内容;归纳总结出煤储层精细描述中的各项“点”参数和“面”参数获取的一般方法,结合“多层次模糊综合评价+多参数叠加”法,提出了煤层气开发地质单元的划分方法,在鄂尔多斯盆地东缘临兴地区进行了实践应用。根据钻井、测井、压裂、排采和实验室测试等数据,建立了相关数学模型,得出了各井点8+9号煤0层的埋深、构造曲率、厚度、含气量、含气饱和度、渗透率、临储压力比、地下水流体势、煤体结构、水平主应力差、脆性指数等参数,应用克里金插值法绘制各参数的等值线图。然后,应用多层次模糊综合评价法对产气潜力进行评价,叠加气体产出条件和煤层可改造性评价结果将研究区划分为3个产气潜力区38个开发地质单元。其中,“甜点”潜力区开发地质单元10个,包括产出和开发条件均有利的I1类2个,产出有利、开发一般的I2类3个,产出有利、开发较差的I3类1个,产出和开发条件均一般的II2类3个,产出条件不利、开发条件有利的III1类1个;“一般”潜力区开发地质单元20个;“不利”潜力区共划分了8个开发地质单元。该方法可有效服务于“地质-工程-排采”一体化的煤层气开发新理念,为煤层气高效建产区建设提供有效地质支撑。

     

    Abstract: According to the geological potential of Coalbed Methane (CBM) production and geological conditions of development,the division of CBM development geological units can provide an important support for the selection of development process. Through the analysis of the influences of different geology and reservoir parameters on the effect of CBM development,and an evaluation parameters system is established,and the main research contents are determined. The general methods of obtaining “point” parameters and “plane” parameters in the fine description of coal reservoir are summarized. Based on the method of multilevel fuzzy comprehensive evaluation and multi-parameter superposition,the division method of geological unit of CBM development is put forward. The method has been applied in the Linxing area of the eastern margin of ordos basin. According to the data of drilling,logging,fracturing,drainage and experimental testing,the corresponding mathematical model is established,and the parameters of No. 8+9 coal seam at each drilling point such as burial depth,tectonic curvature,thickness,gas content,gas saturation,permeability,ratio of critical desorption pressure and reservoir pressure,pressure gradient,groundwater flow potential,coal structure,horizontal principal stress and brittleness index are obtained. The contour map of each parameter is drawn by a Kriging interpolation method. Then,the gas production potential is evaluated by the multi-level fuzzy comprehensive evaluation method. The studying area is divided into three levels and 38 development geological units according to the potential evaluation results and evaluation results of superimposed gas production conditions and coal seam removability. Among them,the “sweet” areas are divided into 10 development geological units,including two favorable output and development conditions,three favorable output conditions and medium development conditions,one favorable output condition and adverse development condition,three medium output conditions and medium development conditions,one adverse output condition and favorable development condition;the 20 development geological units are divided into the “general” area with gas potential;and there are eight development geological units in the “unfavorable” area of gas potential. Division of development geological units can effectively serve the new concept of integration of “geology,engineering and drainage” of CBM development and provide an effective geological support for the construction of high-efficiency CBM development area.

     

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