| Under the condition that conventional energy can’t meet the market demand for a long time, exploration and development of coalbed methane still have a long way to go. The research of coalbed methane has long focused on the part of the reservoir, including the physical properties of reservoir, rock mechanics, industrial group, coal quality and coal rank and etc. And the research on the top and bottom floors is relatively less. In terms of gas and water production prediction, in addition to the reservoir factors, geological factors, construction factors like fracturing and drainage, the impact of the roof and floor factors can’t be ignored. In this paper, based on the previous studies and using coalbed methane logging data of SZN block in Qinshui Basin, the logging response characteristics, rock mechanical characteristics, stability, sealing and water containing of roof and floor of the 3# coal seam are analyzed in the study area, also the relationship between the roof and floor properties and the gas and water production of coal reservoirs is discuss.The roof and floor of target coal seam were divided in the paper, and the strata can be divided from top to bottom for main roof, direct roof, coal, direct floor and main floor. According to the results of the roof and floor division, the log response characteristics of each layer are counted and analyzed. Results show that the main roof and main floor in logging response characteristics are similar, so are the direct roof and direct floor.The longitudinal and transverse wave curve is an indispensable material in the process of formation rock mechanics evaluation, so it is necessary to reconstruct the acoustic curve with the curve reconstruction technique. In this paper, the Xu-White model is used to reconstruct the p-wave and s-wave logging curve of the formation, and has achieved good results. On the basis of the above, the elastic modulus, strength parameters and formation stability parameters of the roof and floor are calculated. Results show that, e except for Poisson’s ratio and collapse pressure, the main roof and main floor are significantly larger than direct roof and direct floor in the rest of the rock elastic parameters, strength parameters and strata stability parameters.In the process of establishing the evaluation model of roof and floor, the stability evaluation model is established by using the fuzzy comprehensive evaluation method, the sealing evaluation model is established by normalization method, and the water containing evaluation model is established by using scoring method. In the practical application of the model, the stability, sealing and water containing of the roof and floor of CBM wells in the study area have been successively evaluated. According to the merits of the evaluation results, the plane distribution characteristics of the various properties of the roof and floor in the study area were determined. In the end, the relationship between the sealing property and water containing property of the roof and floor and gas production and water production of the reservoir is obtained. The following conclusions can be drawn: First, good sealing property of the roof and floor is a necessary condition for the production of coal-bed methane; Second, the roof water containing is closely related to the reservoir water production, but the floor water containing isn’t; Third, the distribution law of the roof water production index and the reservoir water production is highly consistent, and the two are closely related. |
PDF Full Text Request