Coalbed Methane Reservoir Seismic Response Characteristics And Applications

China is abundant in coalbed methane(CBM) resources, the exploitation of which notonly be can regarded as an important supplement of conventional energy resources, but alsoit can effectively reduce the gas outburst accidents underground, thus contributing to coalminesafety production. At present, the exploitation of CBM resources is restricted by the miningefficiency, therefore accurate prediction of the areas rich in CBM is the key to increase themining efficiency. This thesis focuses on seismic prediction method of CBM content andpermeability in CBM reservoir and presents the prediction technique of the CBM-enrichedareas based on seismic attribute through the research on the response characteristics ofseismic attribute of CBM reservoir.This paper summarizes the geological elements affecting the high CBM-enriched areas,and researches on the response relationship between CBM content and seismic attribute bymeans of in-situ test under the shaft; the CBM reservoir geologic model is establishedaccording to the effective medium theory, and by analyzing the seismic attribute responserelationship of CBM content through seismic forward modeling, it could be found that theresult of forward modeling is identical with that of the in-situ test underground.This thesis puts forward a prediction method of CBM content based on DST and DSmTself-adaptive multi-seismic attributes fusion. First select four seismic attributes, named rootmean square amplitude, instantaneous frequency, instantaneous phase and frequency bandwidth as sensitive seismic attributes of CBM content based on the response relationshipbetween CBM content and seismic attribute; then fuse these four seismic attributes throughDST and DSmT self-adaptive information fusion method, and make predictions of CBMcontent, thus effectively solving the uncertainty and multi-solution problem of a singleseismic attribute prediction and improving the prediction accuracy.The fracture density of CBM reservoir is an important factor responsible for the CBMreservoir permeability. The author summarizes the results of velocity anisotropy testing andanalyzing under the stress in coal samples, analyzes the relationship between AVO（AVA）andCBM reservoir fracture density with the forward modeling method, presents the AVAanalytical method of CBM reservoir fracture density, and make information fusion of theprediction result of CBM reservoir fracture density and crustal stress, another importantinfluential element of CBM reservoir permeability. Finally a new prediction method of CBMreservoir permeability is formed.At last, this paper puts forward the three-level geophysical information fusion method of the CBM-enriched areas:①make predictions of resource conditions of the CBM-enrichedareas through information fusion of CBM content and coal thickness;②make predictions ofCBM mining conditions through information fusion of fracture density and crustal stress;③finally, the prediction method of geophysical information fusion for the CBM-enrichedareas could be formed through information fusion of resource conditions and miningconditions. The trial of the CBM test site of Sihe minefield in Qinshui Basin shows that theprediction result is consistent with the output of CBM blowholes in this area and the highprediction accuracy proves the feasibility of this method.