Showing papers on "Permeability (earth sciences) published in 1979"

Pore Distribution and Permeability of Silty Clays

Abstract: This investigation utilizes pore size distribution measurements to examine the relationship between permeability and compactive variables for laboratory compacted clayey silts. Closed-system falling head permeability tests under back pressure were performed on each of the compacted samples. Freeze drying was successfully used to dehydrate specimens prior to pore size measurements. The mercury intrusion technique was used to determine the pore size distribution. The pore size distributions of the soils tested were bimodal with a large pore mode occurring between 10 μ and 1 μ and a small pore mode occurring at 0.1 μ. Varying the compaction variables produced changes in the size and frequency of the large pore mode, but caused no change in the pore size distribution about the small pore mode for a given soil type. Three theoretical permeability models that relate pore size distribution parameters to permeability were generated. These parameters were successfully used to determine empirical permeability prediction equations for the soils tested.

The generalization of Darcy's Law for nonuniform flows

Abstract: A generalized Darcy's law for nonuniform flows in which the pressure gradient depends on the velocity and its derivatives is adopted. The permeability coefficient, as well as a new coefficient, is investigated with the aid of the averaged dissipation equation. The additional coefficient appearing in the generalized law is estimated with the aid of a cell model, and the generalized law is employed in order to solve a few problems (Couette flow past a porous boundary, refraction at the boundary between two porous samples, and flow around a thin partition). Deviations from Darcy's law are found to be confined to thin layers near the medium boundaries.

Oil Recovery Efficiency and the Rock-Pore Properties of Some Sandstone Reservoirs

Abstract: The efficiency with which oil is displaced by water during waterflooding of reservoirs varies from less than 10 per cent to as much as 80 per cent. Both the properties of the fluids and the properties of the rock-pore system contribute to this variability. The total recovery efficiency is the product of the volume fraction of the reservoir contacted or swept by water, which is related to macroscopic properties of the reservoir and to the pore-by-pore displacement efficiency in the swept regions, which is related to the microscopic properties of the reservoir rocks. Trapping on the microscopic scale in swept regions can be estimated from tests on individual samples of core, and it is these tests that are discussed here. Oil displacement efficiency is commonly estimated from relative-permeability tests, but these are difficult and time-consuming to perform and few tests are normally available for a large, heterogeneous reservoir. There is a need for simpler test methods to measure displacement efficiency so that chances of properly modelling a reservoir can be improved. Mercury capillary-pressure tests may be useful in this regard because they can be performed simply, rapidly and inexpensively. Although they provide a measure of displacement efficiency, they do not provide the information on multiphase flow rates obtained from relative-permeability tests. The major objective of this study is to compare mercury recovery efficiency, measured by capillary-pressure tests, to oil recovery efficiency obtained from relative-permeability tests. Furthermore, the results of both these types of tests are related to other petrophysical data such as porosity and gas permeability, as well as to petrographic observations and direct observations of pore structure made from resin casts. For a diverse group of sandstone reservoir rocks there is a statistically significant correlation between mercury recovery efficiencies and oil recovery efficiencies. Rock-pore properties that are significantly related to high recovery efficiency are high porosity, small pore-to-throat size ratio, small mean particle size and low percentage of carbonate. Although permeability is regarded as a property of fundamental importance in modelling the performance of a reservoir, there is no correlation between any measure of permeability, absolute or relative, and mercury or oil recovery efficiency. Porosity is a more sensitive indicator of nonwetting-phase recovery efficiency than is permeability.

Method and apparatus for measuring rock permeability at elevated pressures and temperature

Abstract: The permeability of a rock formation is determined at elevated pressures and temperature by heating a core sample taken from the rock formation and a fluid which is utilized to determine the permeability of the core sample to an elevated temperature. The fluid is injected under pressure and a second pressure which is higher than the injection pressure is applied to the surface area of the core sample. The effect of injecting a fluid such as a corrosion inhibitor or a polymer useful in secondary or tertiary recovery techniques on the permeability of the rock formation can be determined at elevated pressures and temperature by comparing the permeability of the rock formation before the fluid is injected and after the fluid is injected.

An Experimental Technique for Obtaining Permeability-Porosity Relationships in Acidized Porous Media

Abstract: A technique was developed for obtaining permeability-porosity relationships in naturally consolidated porous media. Tests were conducted on limestone and sandstone. The results show that the local change of permeability with porosity is an order or magnitude greater than previously reported. The method also may be used for determining mass transfer coefficients in naturally consolidated systems where the acidization rate is diffusion controlled.

Determination of Permeability Anisotropy in a Two-Way Permeameter

Abstract: This paper describes the use of a new item of laboratory equipment, a two-way permeameter for determination of the degree of permeability anisotropy of compacted or undisturbed samples of soil. The test is performed on a single sample of soil. The relevant theoretical solutions for seepage flow through the permeameter have been provided, based on exact solutions and manual sketching of flow nets.

Hot dry rock energy extraction field test: 75 days of operation of a prototype reservoir at Fenton Hill, Segment 2 of Phase I

Abstract: Results from the first extensive field test of a man-made hot dry rock (HDR) geothermal reservoir in low permeability crystalline rock are presented. A reservoir with a small heat transfer area was utilized to study the characteristics of a prototype HDR system over a shortened lifetime. The resulting accelerated thermal drawdown was modeled to yield an effective area of 8000 m/sup 2/. In addition to the thermal effects, this test provided an opportunity to examine equipment operation, water permeation into the formation, geochemical interaction between the circulating fluid and the rock and flow characteristics including impedance and residence time distributions. Continuous monitoring for induced seismic effects showed that no activity to a Richter threshold of -1.0 was detected during the 75-day experiment.

Determination of the in situ permeability of base and subbase courses

Abstract: The development of a prototype in situ test device, designated the field permeability testing device (FPTD), for determination of the permeability of highway base and subbase courses is described and discussed. The research consisted of two phases. Phase I involved the development and laboratory investigation of feasible in situ permeability measurement techniques, which led to the selection of the velocity method of in situ permeability determination for futher development. Phase II involved the construction of a prototype field permeability tests device (FPTD) and an extensive program of laboratory and field evaluations of this equipment. Based on the results of these studies, it was concluded that the prototype field permeability test device (FPTD) developed during this project satisfies project objectives and provides a convenient means for the determination of the in situ coefficient of permeability of highway bases and subbases with reasonable accuracy and reproducibility. This device permits the consideration in design of saturated hydraulic conductivity (permeability) of bases and subbases and also permits the development of construction specifications for the permeability of these materials, since it makes available for the first time, a mechanism for the evaluation and control of permeability during construction. /FHWA/

Relative permeability during cyclic steam stimulation of heavy oil reservoirs

Abstract: Reliable relative permeability data are important to the overall planning for prospective thermal recovery projects. Empirically derived relative permeability functions presented have characteristics that are dissimilar from those determined experimentally. The empirical functions emerged from simulations of numerous, on-going thermal projects in California's unconsolidated, heavy-oil reservoirs. 12 references.

Soil conditioners for stabilising trench backfill in an unstable loam soil of low permeability

Abstract: Laboratory experiments were carried out to evaluate different soil conditioners for stabilising a loam soil, the aim being to increase the structural stability and the permeability of the backfill of drain trenches. Soil samples previously treated with different concentrations of polymer solutions or emulsions were dried to different moisture contents and packed in cylinders to determine the changes in water permeability. Identical soil samples were subjected to wet-sieving tests for different lengths of time. Loam soil samples treated with emulsions need to be air-dried to make them stable and highly permeable. At higher moisture contents the emulsions become ineffective because of the lack of coagulation between the soil particles. Polymer solutions are effective with regard to soil stability and water permeability even in situations where the soil remains wet. There is a fair agreement between the results of the wet-sieving test and those of the permeability test on loam soil samples. Those two tests were considered as reflecting the behaviour of the soil in a backfilled drain trench.

An analysis of the pressure transient testing of a man-made fractured geothermal reservoir *

Abstract: Pressure-transient testing of a hydraulically fractured geothermal reservoir in low-permeability crystalline basement rock has involved constant rate injection and pressure buildup tests under a wide range of field conditions for a number of fractured regions. Following conventional reservoir analysis methods, data are treated in terms of a transient diffusion equation that relates fluid flow and pressure levels in the main fracture system, associated joints, and the matrix permeability. Pressure-flow data are compared to type curve solutions of the diffusion equation for various flow geometries. The following points are considered in detail: (1) the limits on the fracture geometry, aperture and diffusing areas as determined from the diffusion parameters; (2) the parameters (flow impedance, diffusivity) of the flow-through systems are related to those governing the pressure inflation of the main fractures; (3) the relationship of the rock properties to the reservoir compressibility, effective porosity and permeability are discussed. In particular, laboratory experiments show that the flow properties of all sizes of cracks from large single fractures to the microstructure are pressure dependent if the fluid pressure is near the confining stress; and (4) the competition of flow into the various types of porosity (main fractures, joints, and microstructure) and the effectmore » on the interpretation of type curves are discussed.« less

Method of controlling permeability fr sintering material

Abstract: PURPOSE:To stabilize sintering operation by reducing variation in permeability of material through adjustment of water content and charge bulk of material with measurement thereof at two points in the surge hopper and immediately in front of a cut-off plate

A One-Dimensional Model of Sedimentation Using Darcy's Law

Abstract: Darcy's law together with the mass conservation equation is used to predict concentration profiles in a one-dimensional sedimenting column. Analytic solutions are obtained for two special cases of the diffusivity and hydraulic conductivity. For derived physical parameters the theoretical predictions are compared against experimental results from three sedimenting columns, each of different height. The predictions compare favorably with observations, indicating that this macroscopic approach of Darcy's law should be further developed, both numerically and into more than one spatial dimension.