The Mathematical Principles of Permeability Measurement by Transient Method for Hollow Cylinder Specimen Made of Low-Permeability Rock.

The authors have established strict formulation of mathematical equations for permeability determination by transient pulse method and extended the formulation to the specified cases, i. e., the authors have applied the transient pulse method to the hollow cylinder specimen and extended it's application to the case where fluid leakage from the pressure cell is taken into account. In the hollow cylinder specimen, fluid leakage along specimen boundary can be easily prevented.Intrinsic permeability k was given by the following formula:k=ακμ log(R0 / Ri) / 2πL V1 V2 / V1 + V2where α is the value to be determined from test data, κ is fluid compressibility, μ is fluid viscosity, R0, Ri and L are the outer radius, the inner radius and the height of the hollow cylinder specimen, respectively. V1 and V2 are capacity of the spaces communicating with the inside and the outside of the hollow cylinder specimen in the pressure cell.The authors developed a simple apparatus for permeability measurement. Pneumatic permeability tests using the apparatus were carried out and the permeability of a specimen made of limestone was determined. The permeability test takes only a few hours even for a specimen made of low-permeability rock because of low viscosity of air.