Methods for evaluation of “in situ” coal permeability in underground coal mines using hydrodynamic test data

Abstract

The paper presents methods for in situ evaluation of coal permeability paying special attention to methods invented in the Oil and Gas Institute-National Research Institute (INiG-PIB). Included are: • a slug test method and alternative interpretation of slug test data using procedure devised in INiG-PIB, • a method which uses injection of water with a constant flow rate into a horizontal drainage well and accounts for the three dimensional flow (invented in INiG-PIB), • a method which uses air pressure decay in an isolated segment of a horizontal/vertical well to calculate permeability and skin effect (invented in INiG-PIB).

A Numerical Evaluation of Coal Seam Permeability Derived from Borehole Gas Flow Rate

“…Coal seam permeability may be inferred using a number of experimental methods, such as the drill stem test (DST) [1,6,7], packer test [8,9], and slug test [1,10,11]. These methods generally involve measuring the water pressure (or water head) and flow rate response during the controlled injection into, or withdrawal from, an isolated section of a borehole drilled from the ground surface.…”

“…The hydraulic conductivity, and hence the permeability of a coal seam, can be estimated from the testing data. These types of methods are commonly used in Australia [1,[6][7][8] and some other countries, such as the USA [1,9,10] and Poland [11].…”