Relationship Between Accumulation Conditions Of Coalbed Methane And Producing Gas

Coalbed methane （CBM） is a kind of abnormal gas, commonly known as the "gas"in a coal mine. It seriously hindered the coal mine safety in production. Because themain component of coalbed gas is methane which is a kind of greenhouse effect gas asmuch as22times of carbon dioxide, so the CBM is also one of the main gas causes thegreenhouse effect. Nevertheless the CBM is a kind of clean energy resources. The totalamount of CBM is as high as1100×10⁸m3in Jiaozuo coalfield with potentialdevelopment value.Based on collecting the data and monitoring the CBM well drainage production,analyzing the hydrogeological condition and tectonic characteristics of the research area（Encun mine field）, studying the CBM occurrence characteristic, structure feature andstructure gas-controlling characteristic of Ⅱ₁coal seam by geological evolution, as wellas the CBM accumulation tectonic level control theory and generation, occurrence,moving characteristic theories of the CBM; through the sample macro description,electron microscope investigation, isothermal adsorption experiment of coal samplesand other methods, analyzing and researching porosity, crack characteristics andpermeability of coal seam; at last, the estimating CBM geological reserves andevaluating its recoverable by using volume method, the results are presented as follows.1. Shanxi sandstone and Taiyuan L8limestone aquifers have a great impact on theCBM exploration. There are aquifuge between two aquifers andⅡ₁coal seam, so theⅡ₁coal seam usually cannot connect with the other aquifers. Then in the CBMdevelopment process, the existed faults in some areas maybe make the connectionamong various aquifers, which affect the development of CBM.2. There are two enrichment belts in the F11to F4, the top of the syncline nearNo.12exploration line and the north of the Qiangnan synclinal axis. The CBM contentis positively correlated with the overlaying strata and coal seam buried depth.3. There are many small fractures in theⅡ₁coalbed in the study area. The tectonicsoft coal exists in the roof and floor of the coalbed, so that the adsorption capacity oftheⅡ₁coalbed become strong, the diffusivity ability is low and the permeability becomepoor. Thus, conventionally fracturing process is not suitable for the CBM developmentin Jiaozuo area. This is one of the major factors that cause low gas production of theCBM well.4. The predicted the CBM resource amount is155.50×10⁸m³and the recoverable is69.98×10⁸m³.