Evaluation and optimization of development intervals under conditions of multiple coal seam combinations in Fukang area,Xinjiang Province

The evaluation of advantageous development intervals in multiple coal seam areas and the selection of advantageous combination intervals are important tasks that determine the utilization rate of CBM and the benefits of development.Considering the key parameters of coal reservoir reform ability and drainage,five evaluation indexes are selected including mechanical properties of coal,effective fracturing thickness,coal fragmentation degrees,critical reservoir ratio and permeability.The fuzzy mathematical analytic hierarchy process is used to optimize the dessert segment.Considering resource suitability,inter-layer compatibility,and drainage stability,five key parameters are selected:relative depth,gas content,critical reservoir ratio,reservoir pressure gradient and permeability.The cluster analysis explores the combination relationship of dominant production layers.The eval-uation results show that dessert section with potential value U>0.75 as the node can optimize 5 sets of coal seams A2,A5,39,41 and 42.They have excellent resource allocation,good permeability and strong transformability.The advantage combination section is preferably A3-A4,A7-A8,and 41-42 coal seam combinations.They have similar permeability,pressure gradients,and temporary storage ratios.It is easy to achieve a production“Synchronization”during the drainage and recovery process.The evaluation results are basically consistent with productivity characteristics.Combined with the analysis of drainage characteristics,the coupling of multiple factors is the main production control mechanism of coalbed gas wells in Sigonghe.Production deployment should focus on structural locations and burial depth characteristics and develop superior single coal seam (A2,A5) first.The dominant coal seam combination (A3-A4,A7-A8) consisting of low potential coal seams can be developed and deployed in the later stage.Coal structure,multi-coal drainage and well type are the main factors affecting the productivity of CBM wells in Baiyanghe.Based on a fully consideration of coal structure heterogeneity and coal seam discontinuity,the development area of fragmented and mylonitic coal should be avoided.The development of the superior single coal seam (42,etc.) can take into account the superior coal seam group (41-42,39-41-42) to improve the utilization rate of coalbed methane resources.