AN EMPIRICAL LIQUID PERMEABILITY GAS-PERMEABILITY CORRELATION FOR USEIN AQUIFER PROPERTIES STUDIES

Laboratory permeability studies can contribute significantly to the qu antification of aquifer heterogeneity. However, intrinsic permeabiliti es obtained by standard core analysis techniques using gas are differe nt from those obtained using water. This is because gas measurements m ay be affected by a molecular phenomenon known as gas slippage. An emp irical correlation is presented for liquid and gas permeability measur ements obtained for a suite of Permo-Triassic sandstones and shales fr om the Sherwood Sandstone Group of northern England. Liquid permeabili ty tests were performed using synthetic formation brines and deionized water. Gas permeability tests used nitrogen as the permeant. Liquid p ermeabilites, k(1), ranged from 9.0 x 10(19) m(2) to 2.4 x 10(12) m(2) and gas permeabilites, k(g), ranged from 1.7 x 10(-17) m(2) to 2.6 x 10(-12) m(2). The liquid and gas permeability data exhibit log-normal frequency distributions; the log transformed liquid and gas permeabili ty data have means of 5.1 x 10(-16) m(2) and 4.3 x 10(-15) m(2) respec tively. A linear least-squares fit to the data has the form log(10) k( 1) = 1.17 log(10) k(g) + 1.51. k(1)/k(g) ratios, in the range 0.03 to 0.9, indicate that Hagen-Poiseuille type models may not provide approp riate descriptions of gas flow in the Sherwood Sandstone.