Stress-dependent permeability measurement techniques for unconventional gas reservoirs: Review, evaluation, and application

In‐site investigation of regional outburst prevention in coal roadway strip of a deep mine using an improved method

“…The permeability of coal seam is measured with the gas radial flow method 45,47 . Figure 12 shows the variation of coal seam permeability at different positions before and after stress relief above the floor roadways.…”

“…2. To investigate the permeability variation of coal seam in the stress-relief range of the floor roadways, the radial gas flow method 45 is used to calculate seam permeability through cross-boreholes. The arrangement of measurement groups is similar to that for failure investigation, and detailed information about this arrangement and crossborehole is presented in Table 2.…”

“…The permeability of coal seam is measured with the gas radial flow method. 45,47 Figure 12 shows the variation of coal seam permeability at different positions before and after stress relief above the floor roadways. It can be found that the highest coal seam permeability occurs above the floor roadway, followed by the 2#, 4#, 1#, and 5# boreholes.…”

“…First, the YTJ20‐type camera system is inserted into the cross‐borehole to observe the failure characteristics of surrounding rock. Second, six gauging points are arranged in each cross‐borehole equipped with a DW‐6 multipoint extensometer to observe the displacement of the surrounding rock at different depths. To investigate the permeability variation of coal seam in the stress‐relief range of the floor roadways, the radial gas flow method 45 is used to calculate seam permeability through cross‐boreholes. The arrangement of measurement groups is similar to that for failure investigation, and detailed information about this arrangement and cross‐borehole is presented in Table 2. To investigate the effective gas extraction radius of boreholes, a statistical analysis method 46 of borehole gas flow is adopted to calculate the extraction radius of cross‐boreholes before and after stress relief in the test site.…”

A simplified transient technique for porosity and permeability determination in tight formations: Numerical simulation and experimental validation

“…Permeability of these formations must be measured effectively and accurately to understand and predict the fluid flow behavior in the reservoir 13,14 . The conventional steady‐state method is widely used for the permeability measurement on reservoir rocks with relatively high permeability, but fails to measure permeability of those with low permeability, such as highly stressed coal, tight gas sands, and shales, due to extremely small flowrates and the long time period required to attain a steady flow state 15‐17 . Sander et al 2 reviewed the commonly used permeability measurement methods and provided the possible permeability measurement range through statistical analysis.…”