The interracialtension of water against mixtures of methane and normal decane has been measured in the interval 74 to 3j0°F and 14.7 to 12,000 psia These measurements show the range of interracialtension values obtained witb water against an ideal "live-oil" system under reservoir conditions of temperature and pressure.

The pore-volume compressibilities and porosities presented here were derived from 256 samples of sandstone and limestone representing 40 reservoirs. These and previously published data are in poor agreement with compressibility-porosity correlations in the literature. The salient conclusion is that to evaluate rock compressibility for a given reservoir it is necessary to measure compressibility in the laboratory. Introduction The use of pore-volume compressibility-porosity correlations in engineering calculations is well known. The correlations developed by Hall for both sandstones and limestones have been widely distributed. Van der Knaap published a similar correlation using limestone samples from a single well and also correlated the data with net pressure. Such correlations are attractive because of the simple relationship established. However, those correlations were intended only for well consolidated samples; correlations for friable or unconsolidated samples have not been published. This study compares our laboratory data with the published correlations of consolidated samples as published correlations of consolidated samples as well as with values for friable and unconsolidated sandstones. Compressibility values are presented for 256 rock samples from 40 reservoirs - 197 samples from 29 sandstone reservoirs and 59 samples from 11 limestone reservoirs. Porosities ranged from less than 1 percent to 35 percent. Compressibility values from the literature for 79 samples are added, including Hall's and Van der Knaap's. The Experiments Sampling To obtain a representative sample of a formation for testing, one must avoid grain rearrangement. This problem is unlikely to occur with consolidated problem is unlikely to occur with consolidated samples or friable samples containing some cementation, although the effect of removing the overburden is still unknown. Unconsolidated samples, on the other hand, present a much more complex problem, in that grain rearrangement is very likely during either coring or subsequent handling. The advent of the rubber-sleeve core barrel much improved the chances of obtaining, representative samples. We have some evidence that, if carefully handled. rubber-sleeve cores will provide reasonably undisturbed samples. However, even if the sand is captured undisturbed in the rubber sleeve, internal gas can expand the core during the trip to the surface. The history of all the samples used in this study is not complete, but most of the unconsolidated samples were obtained from rubber-sleeve cores. Preparing the Samples Preparing the Samples The consolidated and friable samples used in this study were generally plugs 1 in. in diameter and 3 in. long, and their condition ranged from well preserved to dry and weathered. The core plugs were extracted in solvent to remove water and hydrocarbons, put into a flexible jacket, and saturated with a refined oil. The unconsolidated samples of about the same dimensions were generally cored from rubber-sleeve cores that had been frozen in liquid nitrogen and for which liquid nitrogen had been used as a drilling fluid. The frozen samples were placed in a Teflon sleeve and allowed to thaw. End plates and screens were then placed on the ends of the samples. JPT P. 129

Chalks or chalklike carbonates have been reported to fail when returned to or near in-situ reservoir stress in the laboratory. Failure of chalks during reservoir production tests has also been reported.This paper presents laboratory results showing that the compaction behavior of the chalks is dependent on the water chemistry of the saturating fluid. The chalks were found to be strong and stable under hydrostatic stress when saturated with oil. Injection of water into the oilsaturated chalks, at stress, caused immediate compaction. The weakening of chalks by water increased the compressibility values four to eight times the oilsaturated values. The chalks resisted failure when stabilized with synthesized formation water containing calcium/bicarbonate ratios equal to the calcium/bicarbonate ratio present in the formation-water analysis. Permeabilities of the chalks saturated with oil and brines are also presented.

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Laboratory equipment is described a experimental methods presented for the measurement of the compression characteristics and permeability of reservoir rock under various states of stress, pore pressure and temperature. The equipment is capable of subjecting cylindrical samples to independently varying pore pressure, axial stress, lateral stress, and temperture. Independent measurements are made of the amount of pore fluid expelled from the sample, the axial strain, the lateral strain, the acoustical travel time across the sample, the rate of fluid flow through the sample, and the fluid pressure drop across the sample. These measurements allow the determination of rock parameters including permeability, porosity change, bulk, pore and grain volume porosity change, bulk, pore and grain volume compressibilities; Poisson's ratio; Young's modulus; and compressional wave (P wave) velocity. Laboratory data are presented of the compressional characteristics of three rocks subjected to two different test conditions. Results are presented of tests on isotropic and anisotropic rock. Results indicate that the past industry practice of calculating bulk and pore volume compressibilities from only axial strain measurements can lead to serious errors if the rock sample is anisotropic. Introduction Many investigators have presented laboratory equipment and/or experimental methods for measuring the compression characteristics of reservoir rocks under various states of stress and fluid pressures. In some cases the equipment was either limited to a single stress state or limited to the number of physical quantities that could be measured at a given stress state. In other cases the equipment was limited both in stress level and temperature so that simulated reservoir conditions for many reservoirs were not possible. This paper describes equipment and experimental methods used for the measurement of compression characteristics of reservoir rocks under various states of stress and fluid pressure at temperatures up to 350 degrees F. The compression characteristics include bulk, pore and grain volume compressibility; porosity; permeability; Poisson's ratio; Young's modulus; Poisson's ratio; Young's modulus; compressive strength; and "P" wave velocity, many of which can be obtained simultaneously. The stress and pressure capabilities of the compression equipment include uniaxial, hydrostatic and biaxial loading. The hydrostatic and biaxial loading can be obtained under either effective or simulated reservoir stress conditions. The stress and pressure capabilities of the compression equipment include uniaxial loading to 45,000 psi, hydrostatic loading to 10,000 psi, biaxial loading to 45,000 psi axial psi, biaxial loading to 45,000 psi axial stress, and 10,000 psi confining stress with pore fluid pressures to 10,000 psi. Axial and lateral strains of the rock samples are monitored during stress and pressure application and a direct measurement pressure application and a direct measurement of the pore fluid volume changes can be made during the application of effective stress with atmospheric pore fluid pressure. pressure. THE EQUIPMENT The basic test equipment is shown schematically in Figures 1 and 2 and photographed in Figure 3. It consists photographed in Figure 3. It consists primarily of a test cell, a hydrostatic primarily of a test cell, a hydrostatic loading frame, a pressure system and a strain monitoring system.