Favorable Block Evaluation Of Coalbed Methane Development In The New Set And The Preferred Method Discussed

According to research thinking for basins in "integral, dynamic, synthesis " aspects andidentifying favorable blocks for coalbed methane (CBM) development in coal mine-scale, the geological background of CBM reservoir and reservoir properties in Xinji coal mining area are systematically summarized in this paper. The paper discussed the characteristics of reservoir, including reservoir's normal pressure, low gas content, low CBM saturation and low permeability, as well as analyzed variation regularity of these parameters and their influencing factors.. The coal reservoir's evolution history is rebuilt. The result shows that during the geological age of 120-23 Ma, the reservoir pressure, CBM content and CBM saturation are reduced due to the basement uplift; since 23Ma, the values of these parameters are resumed because coals are buried at shallow depth, generating secondary biogenic methane. The low reservoir permeability is mainly caused by destroyed fracture system, producing and increasing fragmented coal and mylonitic coal.Primary coal and cataclastic coal mainly situated at underlayer of coal system and deep of mine, fracture is more development and permeability is good in these coal.It is suggested that the thickness of primary coal and cataclastic coal is availability thickness for estimating favorable blocks and calculating CBM resource. The method for predicting CBM content ,permeability and reservoir's pressure is established. Combining mine practical information a new CBM resources classification is put forward, the geological evaluation resource is divided 3 grades in term of the investigation data of coal geology in the classification.The analyzing method of estimating favorable blocks should be combining of qualitative and quantitative. An assessment method is decided for predicting favorable blocks of CBM based on quantitative and subsidiary-quantitative of geographic information system. The evaluation parameters for favorable blocks and value rages of parameters are presented. As a result, 7 favorable blocks for CBM development in Xinji area are identified seam by seam,and the CBM resources in place are calculated seam by seam, block by block, grade by grade. Atlast it is indicated that in Xinji area the CBM resource in place is as much as 19.98×10 m and the resource abundance is about 1.00×108m3/km2.