Division and application of development geological units for coalbed methane

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.