Study on stress sensitivity of medium rank coal reservoir with different saturated water pressure under repeated load

In order to ascertain an effective stress variation affected to the permeability of the water bearing and medium rank coal reservoir in the development of the coalbed methane, a stress sensitivity experiment was repeatedly conducted on a same coal pillar in No.1+3 seam of Songhe Block in West Guizhou. The paper had an analysis on the repeated load and saturated water pressure affected to the mechanism of the coal reservoir permeability and stress sensitivity and had a discussion on the reconstruction of coalbed methane well reservoir and the gas drainage optimized measures. The study results showed that the repeated load and the saturated water pressure of the coal sample would jointly influence permeability and stress sensitivity of the medium rank coal reservoir gas. With the number of the repeated loading increased, the coal mass would have a plastic-elastic deformation evolution, the stress sensitivity would steadily reduced and the failure rate of the permeability would irreversibly be reduced. In comparison with 10 MPa saturated water pressure, the initial gas permeability of 20 MPa saturated water coal sample would be obviously reduced and the stress sensitivity would be weakened and would be steadily stabilized. The micropore crack development of the medium rank coal reservoir was well and the stress sensitivity of the permeability was high. In the development engineering of the coalbed methane, more attention should be paid to the protection of the coal reservoir.