Effective gas permeability of Tight Gas Sandstones as a function of capillary pressure - a non-steady-state approach

Geofluids ◽  
2015 ◽  
Vol 16 (3) ◽  
pp. 367-383 ◽  
Author(s):  
A. Amann-Hildenbrand ◽  
J. P. Dietrichs ◽  
B. M. Krooss
Keyword(s):  
Steady State ◽  
Capillary Pressure ◽  
Gas Permeability ◽  
Tight Gas ◽  
Tight Gas Sandstones

scholarly journals Upscaling gas permeability in tight-gas sandstones

2018 ◽  
Author(s):  
Behzad Ghanbarian ◽  
Carlos Torres-Verdín ◽  
Larry Lake ◽  
Michael Marder
Keyword(s):  
Gas Permeability ◽  
Tight Gas ◽  
Tight Gas Sandstones

A Water-Gas Relative Permeability Relationship for Tight Gas Sand Reservoirs

1990 ◽  
Vol 112 (4) ◽  
pp. 239-245 ◽  
Author(s):  
S. D. L. Lekia ◽  
R. D. Evans
Keyword(s):  
Capillary Pressure ◽  
Relative Permeability ◽  
Water Saturation ◽  
Gas Permeability ◽  
Tight Gas ◽  
Relative Permeabilities ◽  
The North ◽  
Tight Gas Sands ◽  
Straight Line ◽  
Phase Saturation

This paper presents a new approach for the analyses of laboratory-derived capillary pressure data for tight gas sands. The method uses the fact that a log-log plot of capillary pressure against water saturation is a straight line to derive new expressions for both wetting and nonwetting phase relative permeabilities. The new relative permeability equations are explicit functions of water saturation and the slope of the log-log straight line of capillary pressure plotted against water saturation. Relative permeabilities determined with the new expressions have been successfully used in simulation studies of naturally fractured tight gas sands where those determined with Corey-type expressions which are functions of reduced water saturation have failed. A dependence trend is observed between capillary pressure and gas permeability data from some of the tight gas sands of the North American Continent. The trend suggests that the lower the gas permeability, the higher the capillary pressure values at the same wetting phase saturation—especially for saturations less than 60 percent.

scholarly journals Towards Relative Permeability Measurements in Tight Gas Formations

2020 ◽  
Vol 146 ◽  
pp. 05001
Author(s):  
Denis Dzhafarov ◽  
Benjamin Nicot
Keyword(s):  
Steady State ◽  
Relative Permeability ◽  
Water Saturation ◽  
Gas Permeability ◽  
Tight Gas ◽  
Two Phase ◽  
Pressure Step ◽  
Injection Ratio ◽  
Insight Into ◽  
Good Agreement

Relative permeability is a concept used to convey the reduction in flow capability due to the presence of multiple fluids. Relative permeability governs the multiphase flow, therefore it has a significant importance in understanding the reservoir behavior. These parameters are routinely measured on conventional rocks, however their measurement becomes quite challenging for low permeability rocks such as tight gas formations. This study demonstrates a methodology for relative permeability measurements on tight gas samples. The gas permeability has been measured by the Step Decay method and two different techniques have been used to vary the saturations: steady state flooding and vapor desorption. Series of steady-state gas/water simultaneous injection have been performed on a tight gas sample. After stabilization at each injection ratio, NMR T2, NMR Saturation profile and low pressure Step Decay gas permeability have been measured. In parallel, progressive desaturation by vapor desorption technique has been performed on twin plugs. After stabilization at each relative humidity level the NMR T2 and Step Decay gas permeability have been measured in order to compare and validate the two approaches. The techniques were used to gain insight into the tight gas two phase relative permeability of extremely low petrophysical properties (K<100 nD, phi < 5 pu) of tight gas samples of Pyrophyllite outcrop. The two methods show quite good agreement. Both methods demonstrate significant permeability degradation at water saturation higher than irreducible. NMR T2 measurements for both methods indicates bimodal T2-distributions, and desaturation first occurs on low T2 signal (small pores). Comparison of humidity drying and steady-state desaturation technique has shown a 12-18 su difference between critical water saturation (Swc) measured in gas/water steady-state injection and irreducible saturation (Swirr) measured by vapor desorption.

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