No abstract

According to dimensionless analysis of the coalbed methane (CBM) production data of Fanzhuang block in southern Qinshui basin, the dimensionless gas production rate is calculated to quantitatively divide the CBM well production process into four stages, i.e., drainage stage, unstable gas production stage, stable gas production stage, and gas production decline stage. By the material balance method, the coal reservoir permeability change in different stages is quantitatively characterized. The characteristics and control mechanisms of change in coalbed permeability (CICP) during different production stages are concluded on five aspects, i.e., permeability trend variation, controlling mechanism, system energy, phase state compositions, and production performance. The study reveals that CICP is characterized by first decline, then recovery, and finally by increase and is controlled directly by effective stress and matrix shrinkage effects. Further, the duration and intensity of the matrix shrinkage effect are inherently controlled by adsorption and desorption features.

This study divided the oil shale segments and the quality grades; tested the oil content of oil shale samples in different segments; found out the distribution characteristics of the ore bodies in each segment; identified the ore-bearing properties of oil shale ore bodies; summarized the method, the range, and the parameter determination of resource estimation; and the divisional principle of resource blocks. Then the separate-level profiling method was chosen to delineate the oil shale ore bodies over and under the ground, and the profile lines, the bottom contour lines (horizontal lines), the outcrop lines, the synclinal axis, and the boundary line of the mining area were used to constrain the blocks. Finally, the mineable oil shale amount in the study area was calculated. The results show that the amount of low-quality, medium-quality, and high-quality oil shales are 3,482, 2,598, and 1,348 million tons, respectively.