How the liquid permeability of rocks is affected by pressure and temperature

Abstract

Laboratory determinations Of the permeabilities, porosities, and residual water saturation of rocks of oil-and gas-bearing areas are usually based on data obtained under atmospheric conditions.Investigations [1][2][3][4] have shown that the reservoir properties of deeply buried rocks differ markedly from those of the same rocks under atmospheric conditions. These differences are due to the physical conditions under which the values are determined. Owing to the natural differences between the rocks which act as reservoirs, we cannot use the experimental data obtained for individual specimens to assess the same characteristics of rocks from other oil-and gas-bearing areas. The great variety displayed by reservoir rocks is governed by the depth of occurrence, the chemical composition of the minerals, their grading, roundness, grain-size composition, the amount and quality of the cementing substance, the ratio of plastic and elastic minerals, the packing of the mineral grains, etc.The filtration characteristics of rocks depend on their depth of occurrence (on pressure and temperature, which cause deformation of the porous medium). To study the effects of pressure and temperature on the filtration characteristics of rocks, the Laboratory of Seam Physics of SNIIGGiMS designed an apparatus [5] enabling us to simulate a whole group of physical conditions, the specimen being tested under the natural conditions of occurrence.Before tests on liquid permeability were performed, the pore volume of the specimen was determined under given pressure and temperature conditions. This was effected as follows. The specimen was dried at 105-110~ saturated with distilled water to constant weight under vacuum, and then placed in a core holder [5], in which its lateral surface was subjected to a hydraulic pressure of up to 1.5-2 atm by means of a thin-walled rubber jacket and oil, fed through a connecting pipe. An impermeable steel cylinder was pressed against the upper face of the specimen by a ram, and a steel cylinder with an orifice and trap with ducts for obtaining an intraporous hydrostatic pressure was pressed against the lower face. The cylinder and trap were pressed against the lower face of the specimen by a nut and a movable punch. The specimen was heated to the given temperature, at which it was maintained automatically. During this process the water expands and collects on the bottom of the trap. The volume of water due to thermal expansion is determined from the formula = (P0 -do Vo) / a0, where W 0 is the volume of water obtained from the specimen due to thermal expansion and reduced to 20~ P0 is the weight of water completely saturating the specimen at 20~ v 0 is the pore volume of the specimen at 20~ 0 is the temperature in degrees, d o is the specific gravity of distilled water at 0, and d o is the specific gravity of water at 20~ Thermal expansion of the grains was neglected (to the best of my knowledge, no investigations are being performed on the temperature dependence of rock porosity in absence of external pressur...

Geochemical equilibrium modeling of the Auburn Thermal Energy Storage Field Test

“…Several experimental studies have demonstrated temperature effects on the absolute permeability of unconsolidated sands and consolidated sandstones (Greenberg et ale 1968, Afinogenov 1969, Weinbrandt 1972, Casse 1974, Aruna 1976, and Danesh et ale 1978. In general, the main observations derived from these studies are:…”