| In this dissertation,coalbed methane of Mabi block in Jincheng was selected as the research object.The achievements of coalbed methane exploration and development had been collected systematically.The geological conditions of the block were studied and analyzed from large areas to small well groups.Also,researched and analysised the reservoir characterics.The relationship between geological and engineering factors and production capacity was analyzed.The main control factors of coalbed methane well production capacity in this area were obtained by using hierarchical analysis method.At the same time,the influence and restriction of block geological conditions on the development mode were analyzed,and the geological adaptability of development was evaluated.Finally,the block productivity chart was drawn,and the mechanism and method of block high yield were put forward.The following main results and understandings have been achieved.(1)The geological structure,reservoir and gas-bearing of the study area were studied.The overall structure is simple,and the No.3 coal seam of Shanxi formation,the No.15 coal seam of Taiyuan formation are developed stably,with good content and low permeability.On this basis,through the selection of some geological conditions and engineering conditions parameters for analysis and research.It has revealed that there is a significant correlation between gas content,coal seam thickness and cumulative gas production in the study area.When the abundance of resources is poor,the correlation between buried depth and production capacity is also significantly enhanced.The amount of fracturing fluid and sand in engineering factors has a significant correlation with the cumulative output of a single well,but the influence on the output gradually weakens with the extension of the drainage time.AHP was used to determine the weight of the main control factors of production capacity.The main control factors from strong to weak are fracturing sand,fracturing fluid,gas content,coal thickness and buried depth.(2)On the basis of determining the restriction of geological conditions on the development mode,the optimal development mode of the block was selected and the geological adaptability of the development was evaluated.Block coal reservoir permeability is poor,strong adsorption,so that fracturing influence range is small,coal bed methane desorption is difficult.It is beneficial to reduce the pressure of formation area and increase the output of single well and well group by using cluster well type combined with stratified fracturing.Based on the study of rock mechanics and rock properties of the top and bottom of 3~#coal seam and 15~#coal seam,it is feasible to develop stratified fracturing combined layer.In the process of fracturing,the variable displacement construction technology is adopted.(3)When buried depth is 640?750m,gas content is 15?18 m~3/t,coal thickness is5.4?6.3m,the sand ratio is 7.6?8.5%,and the amount of fracturing fluid per unit coal thickness is 70 and 90 m~3/m,the more easily the cluster well group can achieve high yield.Propose specific optimization measures for drainage technology,reservoir reconstruction,differential geological control of production capacity,production technology,etc.It is an effective method to obtain peak output as far as possible by using gas extraction(but not more than 10 m/d)with stable drainage strength of less than 12 m/d before casing pressure.Using active water fracturing plus sand fracturing,the recommended fracturing fluid volume 200 m~3/m,fracturing sand volume 15m~3/m,"low pre-ratio,rapid back-discharge"fracturing process,fine,medium,coarse sand three-stage sand addition mode to improve the fracturing effect.By adjusting the spacing between wells and increasing the scale of fracturing,forming effective inter-well interference,the yield of coalbed methane is improved.This dissertation has 63 pictures,12 tables and 123 references. |
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