Development effect and productivity evaluation of multi-thin coal seam horizontal well in Zhijin block, Guizhou Province

The productivity of coalbed methane horizontal Wells is affected by many factors such as geological conditions of coal seam, degree of fracturing transformation, drainage and production management system, and there is a phenomenon of large productivity difference among different horizontal Wells in the same working area. Taking Zhijin CBM horizontal Wells as the research object, the coal seam geological characteristics, reservoir reconstruction scale and drainage management differences of each horizontal well are deeply discussed. Based on the fuzzy comprehensive evaluation method, a comprehensive evaluation model for CBM horizontal Wells' productivity was proposed, and the comprehensive scores of each horizontal well in Zhijin working area were calculated semi-quantitatively. ZP3 and Z56 Wells with high productivity potential in the work area were selected to provide effective guidance for the efficient development and utilization of Zhijin coalbed methane. On-site discharge and production have verified its rationality and reliability. The results show that: The coal seam of Longtan Formation in Zhijin block belongs to the transitional facies environment of sea and land, and has the geological characteristics of wide distribution, thin single layer and many layers; Among them, the NO.23 and NO.27 coal seams of Longtan Formation have stable distribution and high gas content, which provides a good geological basis for the generation and storage of coalbed gas, and has better adaptability to horizontal well technology. The key to the productivity breakthrough of horizontal Wells is to realize the “geology+engineering” double dessert construction. It is suggested that the CBM horizontal Wells should focus on optimizing the parameters of sand addition and sand intensity during the development stage, do a good job in horizontal fracturing with high gas measurement of total hydrocarbon value, and extend the flowback fluid volume before gas discovery, which is conducive to the productivity breakthrough of horizontal Wells. The comprehensive evaluation results of 6 horizontal Wells in Zhijin block are as follows: ZP3>Z56>ZP1>Z58>Z2U1>ZP2, which provides effective guidance for further releasing CBM well productivity in Zhijin.