Analysis On Fracturing Effect And Influencing Factors Of Coalbed Methane Wells In Zhengzhuang Block, Qinshui Basin

The south of Qinshui Basin is one of the most successful areas of coalbed methane development in China. However, during the development and practice, many coalbed methane wells have a lot of phenomena such as insufficient gas production,large amount of water production and low gas production rate. It is urgent to develop the research of the compatibility relationship between fracturing and drainage effect and geological influencing factors of coalbed methane wells in Zhengzhuang block. Based on the geological data, fracturing construction and the drainage data of thousands wells in Zhengzhuang block, this thesis analyzes the geological factors influencing fracturing and drainage effect in research area from qualitative and quantitative, discusses the evaluation scheme of fracturing and drainage effect. This study can provide effective guide for exploration and production of coalbed methane (CBM) in this area.Based on the comprehensively analysis of the fracturing curve of 284 wells,the fracturing curves of Zhengzhuang block can be divided into four types. According to fracturing effect (hydraulic curve, sand curve and displacement curve) from good to bad, they are the stable type, stable fluctuation type, descending type and fluctuation type. In the same engineering conditions, the fracturing effect of gas wells in the study area is affected by various geological factors. The coal structure is the main controlling factor, the tectonic condition and the geostress are the second. These factors influence the fracturing effect including the fracture morphology and expansion mode. The best fracturing area are in the place where there are thick normal-strucure coals, and less tectonic deformation.Based on the analysis of the 284 well drainage curve, the CBM produciton curve of Zhengzhuang block can be divided into for types, from good to bad they are stable type, rising type, attenuation type and fluctuation type. The well drainage effect in the study area is influenced by engineering factors and geological factors. The main geological factors are the gas content and, structural condition and burial depth, and the main engineering factors is run down speed of liquid surface of the CBM production well. The CBM well have good gas production rate in the areas of less structure deformation and large gas content.According to qualitative and quantitative analysis, the study area is divided into six main areas. The west and northwest are the optimum constituency. The middle and the east are preferred districts. The south and the Northeast are the bad constituency.Based on Artificial neural network (ANN) algorithm, the Neural network prediction of gas-time and accumulative gas production in coalbed methane wells in the research area is presented, and the prediction error is small, which shows that there is a good correlation between the typical parameters of coalbed gas well drainage in the research area.