Experimental study on overburden porosity and permeability of coal reservoir in Tucheng syncline of Western Guizhou

Abstract

In order to study the characteristics of porosity, permeability and stress sensitivity of middle rank coal reservoir in Tucheng syncline and their influence on coalbed methane exploitation, coal core samples of coal seams 1#, 3#, 5#, 15#, 17#, 291# and 292# in Tucheng syncline were collected. Based on the overburden porosity and permeability test, the variation law of porosity and permeability with effective stress of each coal reservoir is compared, and the sensitivity of effective stress of each coal reservoir is analyzed by using the parameters of porosity stress damage rate, permeability stress damage rate and permeability curvature. The results show that: with the increase of effective stress, the coal reservoir porosity and gas permeability were negative exponent; the stress sensitivity coefficient of test coal reservoir is 0.035-0.073 MPa-1, and the stress sensitivity regression coefficient of 3# coal sample is the largest; the stress damage rate of porosity increases with the increase of effective stress, and the stress damage rate of 3# coal sample with shallow burial depth is relatively large. The permeability stress damage rate increases exponentially with the increase of effective stress, and the permeability damage rate of 3# coal sample is obviously larger than that of other coal samples. The permeability curvature of coal reservoir decreases exponentially with the increase of effective stress.Under the same effective stress, the stress sensitivity of 3# coal seam is greater than that of 5#, 15# and 29# coal seam, and the stress sensitivity of 1# and 17# coal seam is the weakest.

Keywords

• tucheng syncline
• coal reservoir
• overburden hole permeability
• effective stress
• stress sensitivity