| Coalbed methane(CBM)is a new unconventional natural gas resource with no pollution and high calorific value.The state has been encouraging the development of coalbed methane industry.Qinshui basin is one of the bases for the industrial development of coalbed methane in China.However,the gas production of different coalbed methane wells in the block varies greatly,so it is necessary to further identify the causes,analyze various geological engineering factors affecting the development of coalbed methane,find out the relationship between the dynamic changes of each factor,and propose targeted measures.By collecting and sorting out the data,this paper makes a systematic study of the geological background of the Fanzhuang block,such as the strata,structure,gas content and hydrological characteristics,so as to provide a theoretical basis for finding the rules.Then,the coal bed methane production indexes of the three well areas(Fanzhuang well area,Chengzhuang well area and Zhengcun well area)in Fanzhuang block were compared,and the reasons were analyzed from the aspects of geological structure,development technology and drainage control,etc.,and the dynamic law of coal bed methane mining was summarized.Then,by means of a large number of data collection,data collection,chart making and other methods,this paper analyzes and studies the causes of productivity difference from two aspects of geological control factors and engineering factors,reveals the relationship between the dynamic changes of each factor,and proposes reasonable control measures to better guide the efficient development of CBM application.The main achievements of this paper are as follows:1.The coal seam structure of Shanxi formation 3~#and taiyuan formation 15~#in Fanzhuang block is simple and stable,with large thickness and high gas content.The hydrological conditions are favorable for coal-bed methane enrichment.2.The development of Fanzhuang well area district was the earliest,and the development effect was not ideal.However,with the progress of technology and the implementation of stimulation measures,the gas production in this well area increased steadily.The development condition of Chengzhuang well area is obviously better than that of Fanzhuang.It has simple structure,good physical property,close to the influence of coal mining,high permeability and considerable gas production.The geological condition of Zhengcun well area is similar to that of Chengzhuang,and the well pattern is perfect.3.The geological factors affecting the productivity difference of coalbed methane wells include the reservoir pressure ratio,gas-bearing capacity,coal seam depth,and structural conditions.The higher the ratio of reservoir pressure,the higher the productivity of CBM wells.The permeability,gas-bearing and fault properties of different tectonic areas are obviously different.4.The engineering influencing factors of CBM wells productivity difference include extraction system and reservoir transformation technology.In terms of extraction system,the drainage and pressure lowering effect of coalbed methane wells in water-producing stage directly affects the gas production of coalbed methane wells.In the aspect of reservoir reconstruction technology,the relationship between the fracture length and width and the maximum daily gas output is parabolic.Within a certain range,the larger the amount of fluid in advance and in carrying sand,the better the fracturing effect and the more conducive to production.5.Based on the laws mastered in the study,three production improvement measures,such as rational well location deployment,optimized drainage system and secondary fracturing,were proposed to guide the development of high and stable production of coalbed methane wells.In the next step,it will be the focus of future research to find out the arrangement and production control of composite bed and optimize well pattern layout.There are 66 figures,19 tables and 87 references in this paper. |
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