Influence Analysis of Local Structure of B1 Wellblock on Fracturing Operation and CBM Drainage in Baode Area

The B1 well block is located in the south of the Bode block. In the case of hydraulic fracturing of 4+5^# and 8+9^# coal seams in the well area, there are large construction pressure difference, large construction difficulty, large water production and less gas after the production. In view of these questions, on the basis of analyzing the data of hydraulic fracturing, geologic structure, seismic and sonic logging material, by summarizing the distribution laws of construction pressure and fracturing curves, and combined with coal roof structure characteristics, it shows that the low-pressure well and the descending-pressure curve well are mainly distributed in flexure and small fold zone. It is considered that local structure has a control effect on the fracture construction in the B1 well block. The two coal seam located under the neutral surface of Linzheyu fold is subjected to tectonic stress in the north and east during Himalaya movement; in the northern part of the B1 well block, the gently inclined coal seam only exists small structural deformation and stress concentration problem with local stress concentration. But in the southern part, there are a large amount of small faults and fractures in flexure and small fold zone, and the tectonic stress is released due to the intensive stratum deformation, which results in the difference in construction pressure. There are some large faults which go against the coalbed methane reserves in the south of B1 well block, while it may intercommunicate coalbed and high water-bearing strata through faults after hydraulic fracturing operation, it results in the large water production and less gas phenomenon.