Matrix Permeability Measurement of Gas Productive Shales Available to Purchase

Three laboratory methods were developed to measure matrix gas permeability (K_m) of Devonian shale cores and drill cuttings at native water saturations. The first method uses pulse pressure testing of core plugs with helium. The second, new method uses pulse pressure testing of core chips or drill cuttings with helium. These methods gave comparable results on 23 companion shale samples from two wells, with K_m = 0.2 to 19 × 10⁻⁸ md. The third, new method uses degassibility of core plugs with helium and methane, and yielded K_m higher by a factor of 3 to 10. Most of the core plugs tested showed multiple microfractures that remain open at reservoir stress, and these dominate conventional flow tests. These microfractures are parallel to bedding, are coring induced, and are not present in the reservoir. Knowledge of K_m is important in computer simulation modeling of long term Devonian shale gas production, and has been a key to understanding the nature of the natural fracture network present in the reservoir.