Showing papers on "Permeability (earth sciences) published in 1980"

A Laboratory Study of Low-Permeability Gas Sands

Abstract: To help moderate or reverse the persistent decline in US gas reserves, the industry is expanding its exploration and development efforts to include fields with permeabilities in the microdarcy range; however, the design of stimulation treatments to achieve commercial rates of production from such low-permeability rocks demands a more accurate means of determining their flow properties. Laboratory tests designed to develop correlations for predicting a reservoir's in situ permeability from routine core-analysis data have shown that the routine permeability values of tight gas sands are often more than 100 times greater than permeabilities under actual reservoir conditions because of the great relief of stress, absence of connate water, and increased gas slippage. The correlations developed can account for these three separate effects and produce a closer estimate of the reservoir's in situ effective gas permeability.

A mechanistic theory of ice lens formation in fine-grained soils

Abstract: This study reveals that a freezing soil can be characterized by two parameters, the segregation-freezing temperature Ts and the overall permeability of the frozen fringe . During unsteady heat flow...

Oil Recovery by Gravity Drainage

Abstract: Recent observations have indicated surprisingly high oil recoveries for gravity drainage. This has prompted the reexamination of gravity drainage as an oil recovery process. It is shown that oil relative permeability is a key factor. To measure this oil relative permeability accurately, a new method based on centrifugal gas-oil displacement in small cores is described. Several oil relative permeabilities for various rock types are presented. These relative permeabilities confirm that gravity drainage in water-wet connate-water-bearing reservoirs can be a very effective oil recovery process.

Darcy's Law for Flow in Porous Media and the Two-Space Method,

Abstract: A common problem in engineering and science is to derive simple equations governing complicated phenomena. Often complicated governing equations are known, but they are too difficult to analyze. An example of a simplified equation is Darcy’s law, which describes flow of a viscous fluid through a porous medium. The more complicated equation for the same phenomenon is the Navier-Stokes equation. As an example of a general method for simplifying equations, This chapter shows how to derive Darcy’s law from the Navier-Stokes equation. Simplified equations are often called “homogenized equations,” and the procedure of replacing the original equations by them is often called “homogenization.” The chapter discusses the two-space method for deriving simplified equations by using an example of the flow of a compressible viscous fluid through a rigid porous medium.

Gravitational stability of water over steam in vapor‐dominated geothermal systems

Abstract: Vapor-dominated geothermal systems exist in a most extraordinary state: a condensate or water layer several hundred meters thick overlies a main steam zone of undetermined thickness. Why doesn't the water fall down. We show that a heavy fluid phase overlying a light phase of the same fluid in a porous medium can be stable provided the permeability in the vicinity of the interface is not too large. The special behavior of a phase change interface in response to disturbances of the boundary account for the stabilization. Heavy fluids overlying light fluids in a porous medium are unstable, irrespective of permeability, if the fluids are immiscible. Application of the stabiliy analysis to vapor-dominated geothermal systems shows that the condensate layer can be stabilized if the permeability near its base is no large than about 40 nm/sup 2/ (0.04 millidarcy).

Transient Flow In Naturally Fractured Reservoirs And Its Application To Devonian Gas Shales

Abstract: Devonian shale gas reservoirs typically are characterized by a low storage, high flow-capacity natural fracture system fed by a high storage, low flow-capacity rock matrix. In this study analytical solutions are developed to analyze the basic fractured reservoir parameters that control well productivity. These parameters include fractured system porosity and permeability, matrix porosity and permeability, and matrix size. It is shown that the conventional well test method does not usually work for fractured Devonian shale gas reservoirs. For most cases, the semi-log plot of the drawdown then buildup data does not show 2 parallel straight lines with a vertical separation. Numerical solutions also are used to include the Klinkenberg effect and desorption in the shale matrix. 18 references.

Groundwater regime associated with slope stability in Champlain clay deposits

Abstract: Slope stability analyses in terms of effective stresses are most often based on hypothetical conditions of pore pressure. It is generally assumed that the flow occurs parallel to the slope or even that the conditions are hydrostatic. In fact, in situ measurements tend to show that the real situation could significantly deviate from these approximations due to geologic conditions. The influence of various geometric and stratigraphic factors on the groundwater regime and on the stability of slopes was studied with the finite-element method. To illustrate the parametric study, experimental evaluations of the flow patterns are presented at four sites. The stratigraphy and permeability measurements combined with the finite-element method enabled a complete flow net to be drawn and although some hypotheses had to be formulated with regards to the underlying aquifer recharge or permeability anisotropy, reasonable agreement was found between simulated and measured piezometric heads.

Selectively controlling fluid flow through the higher permeability zones of subterranean reservoirs

Abstract: A method for restricting fluid flow in depth outwardly from the bore hole through the medium to high permeable zones of a subterranean reservoir of nonuniform permeability in which there is injected into the reservoir aqueous solutions of a water-soluble polymer and an alkali metal silicate. The injected solutions are either admixed at the surface prior to injection, simultaneously injected or injected sequentially.

Hydraulic Properties of Coal and Related Materials, Northern Great Plains

Abstract: The hydraulic properties (hydraulic conductivity, specific storage and porosity) of coal and the sediments that surround the coal must be known or estimated to properly evaluate the environmental impact of coal strip mining on ground-water flow systems. Published and unpublished data have been summarized from five study areas in North Dakota, three areas in Wyoming, two areas in Montana and two study sites in Alberta. Coal and sand beds form important aquifers in the region. Both materials have hydraulic conductivities of about 2 × 10−6 m.s−1 and specific storage values on the order of 5 × 10−6 m−1. Aquitards in the region consist of clayey silt to clay bedrock and pebble−loam (in parts of the region). The aquitards are fractured to varying degrees resulting in a wide range of measured hydraulic conductivity values. The aquitards are, in general, 100 to 1,000 times less permeable than the aquifers. Specific storage values of the aquitard material is on the order of 3 × 10−4 m−1. The hydraulic conductivity of strip mine spoils has a six order of magnitude range with a mean of 8 × 10−7 m.s−1. Variability is due to a number of factors including spatial variation of overburden lithology, method of spoil handling and contouring and time of year during which the spoil is handled. The hydraulic conductivity of the coal shows wide spatial variability within a given mine site. Variability of coal hydraulic conductivity between mines within North Dakota is less than within a given mine. Within the Northern Great Plains the permeability of coal may increase slightly from east to west.

Diffusion Salt Flow Through Membranes and Permeability Determination from Gell Potential Measurements

Abstract: In the present paper a method to obtain the diffusion salt flow through a passive membrane is shown, when the membrane separates two solutions at different concentrations of the same electrolyte. This method is based on the determination of the concentration change in the more diluted solution, from the variation in its cell potential with respect to a reference solution. These flows are average flows corresponding to the time interval in which the diffusion process occurs. From these flows we can obtain the flux at time t = 0. The application of the described method to Nuclepore membranes of different pore diameter is presented. Introduction The measurements of salt flows through a membrane has been effectuated by different methods. Delmotte and Chanu [ 1 ] have built a device which allows to establish a constant gradient of concentration through a membrane, by injecting automatically, in the compartments containing the diluted and concentrated solutions, the suitable volume of dissolvent or superconcentrated solution, respectively. Evaluating the injected amount, it is possible to determine the salt flow corresponding to the established concentration gradient. Other authors, as for example Nomura et al [2], determine the salt flux from the experimental change in the electrical conductance of the solutions, due to the diffusion. 1. Content * The present paper furnishes a method to determine the diffusion salt flows through passive membranes, i.e. membranes without biological material arising a chemical transport, based on the cell potential measurement. The paper presents also the * Author to whom all correspondence should be addressed. 0340-0204/80/0005-0313$02.00 © Copyright by Walter de Gruyter & Co. Berlin · New York 3 j 4 J. A. Ibanez et al. application of this method to Nuclepore membranes. The diffusion process through the membrane, which separates two solutions at different concentration of the same electrolyte (in an isolated and unstirred system), is a non-stationajry process and has been studied, in the case of organic liquids, by Hoogervorst et al. [3-5]. The measurements of salt flows allow the determination of the permeability of the membrane system (formed by the membrane and the two diffusion boundary layers flanking it), whose knowledge is very intersting since from it we can obtain some internal characteristics of the membrane system, such as the diffusivity of the electrolyte in the membrane, and the thickness of the diffusion boundary layers [6]. 2. Experimental device Membranes and the membrane cell The membranes used in this work, are Nuclepore filters manufactured by General Electric (USA). They consist of a thin sheet of polycarbonate perforated by an array of discrete and nearly parallel pores. The filters are available in a range of graded pore sizes. We have used six kinds of these filters, whose maximun pore radius (manufacturer indication), so as the evaluated value experimentally by the \"half-time\"method [7] are given in Table 1. These membranes were placed in the holder of a membrane cell, of the same type as the one employed by Meares in some of his experiments [7]. The membrane cell is formed by the membrane holder and two electrolyte compartments, R, which contain the solutions at both sides of the membrane holder. The exposed area of the membrane in the holder was of 0.95 ± 0.02 cm. Each of the compartments R had an internal volume, V, of 358 ± 3 ml. Solutions of NaCl (Panreac) were used, prepared from distilled deionized water. The solutions were degassed. Tab. 1: Nuclepore membranes used in the experiments. Nominal and experimental values of the .pore radii.

Effect of Temperature and Solution Composition on the Permeability of St. Peters Sandstone: Role of Iron (III)

Abstract: The purpose of this study was to systematically investigate effects of temperature and fluid composition on the permeability of quartz sandstones. We have concentrated our initial efforts on the time and flow dependence at 2 elevated temperatures (100°C, 200°C).

Permeability of Porous Media as a Function of Porosity and Particle Size Distribution

Abstract: AN experimental permeability model was developed relating intrinsic permeability to porosity and parti-cle size distribution of porous media composed of spherical particles. The influence of particle size distribution on porosity was greater than the effect of particle size. The experimental data showed that volume-surface mean diameter can be used to represent average particle size for flow problems.

The role of large-scale permeability measurements in fractured rock and their application at stripa

Abstract: The macropermeability experiment at the Stripa mine in Sweden is part of the Swedish-American Cooperative Program on Radioactive Waste Storage in Mined Caverns in Crystalline Rock (1,2). The experiment is an attempt to improve permeability characterization techniques for the analysis of regional groundwater flow through low permeability rock in the vicinity of a nuclear waste repository. This experiment consists of monitoring flow into, and pressure surrounding a 5 m x 5 m x 33 m long drift called the ventilation drift at the 335 m level of the Stripa mine (Fig. 1). This paper examines the theoretical problems associated with making such a measurement and describes the actual experiment now in progress.

Nonlinearity in groundwater flow

Abstract: Since 1856 when Darcy laid the basis for the calculation of the flow of water through sands, researchers have been interested in groundwater flow. Groundwater is essential for agriculture and water supply, but it also plays an important role when soil is used as a construction element, such as for dykes, roads and foundations. The mechanical behaviour of saturated or dry, fine graded or coarse soils are quite different. The theory of groundwater mechanics must be based on the system: water-soil-air. Up to now study has been restricted to mainly saturated and/or undeformable soil. In this thesis the contemporary theory is extended to compressible fluid flow in a semi-saturated deformable porous medium; a water-soil-air mixture, the air in which appears in the form of micro-bubbles. The pore water moves, whereas the soil itself deforms. It is assumed that this deformation behaviour is linear and free of rotations. From a fundamental reconsideration it is shown that the mechanical behaviour of this system can be formulated in a rather simple way taking into account various nonlinear effects. Convective terms and the variation of the permeability related to soil deformation are included. The validity of the formulation derived is discussed. A general solving procedure applying the Mellin transformation technique allows elucidation of the influence of these nonlinear terms on the basis of analytical solutions of some characteristic problems. In the phenomenon of groundwater flow so-called moving boundaries also occur. The free surface of natural groundwater, which actually varies, is such a boundary. This implies that the domain in which the process of porous flow is considered, changes (geometric nonlinearity). This aspect is explained. Transient phreatic porous flow problems can be solved by applying numerical models. In the discussion reference is made to the extensive literature. In conclusion, the following statements hold for nonlinear groundwater flow. In most practical cases the linear theory is sufficiently accurate, nonlinearity becomes manifest in a reduction of the area of influence, and time dependent porous flow problems can be explicitely solved applying a time step much larger than formerly assumed.

The Enhancement of the Permeability of Granite by Explosive and Hydraulic Fracturing

Abstract: Geothermal energy is potentially available from rock at elevated temperatures in the Earth’s crust but which lacks circulating fluids to transport the energy to the surface. This resource has become known as the Hot Dry Rock energy source. Two alternative extraction concepts have been proposed and this paper details the results of a field experiment designed to stimulate many fractures at the wellbore. Unfocused explosive charges were used to produce optimum radial fracture patterns that could then be enhanced by hydraulic stimulation. The resulting system is extremely complex but the results indicate that this combination of fracturing techniques is essential to overcome the strength and impermeability of the granite fabric

Effect of Air on the Hydraulic Conductivity of Concrete

Abstract: The effect of air on the hydraulic conductivity or permeability of concrete has been discussed in the literature for many years. Although the effect of air may affect the rate of water flow significantly, this effect is very seldom accounted for in routine testing and evaluation of permeability of concrete. Since concrete is being used now to an increasing extent for large offshore structures in deep ocean waters, a better and more reliable basis for testing and evaluating concrete permeability is greatly needed. This is the background for a research program where the effect of varying testing conditions are being studied. In the present paper some preliminary results on the effect of air in the test system are reported. A few results of the effect of evaporation from the output side of the concrete also are included. Testing and evaluation of permeability are discussed, and a new approach for testing is outlined briefly.

Pressure transient testing of a manmade fractured geothermal reservoir: an examination of fracture versus matrix dominated flow effects

Abstract: The data analysis is in terms of a diffusion equation that determines the flow of water and hence the pressure in the main fracture system, associated joints, and the matrix permeability. The fits of the flow data to type curve solutions of the diffusion equation with pressure-dependent properties for various flow geometries are presented. The following points are considered in detail. (1) The limits on the fracture geometry, aperture, and diffusing areas are determined from the diffusion parameters. (2) Dependence of the parameters (impedance, diffusivity) of the flow-through systems are related to the inflation of the major fractures. (3) The rock properties are related to the reservoir compressibility and permeability. In particular, laboratory experiments have shown that the 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. The effects of this pressure dependence on the form of the type curves are included. (4) The competition of flow into the various types of porosity (main fractures, joints, and microstructure) and the effect on the interpretation of type curves are considered. The approach described makes an important departure from conventional pressure-transient reservoir analysis in that pressure-dependentmore » properties are incorporated into a numerically simulated generation of type curves resulting from one- and two-dimensional diffusion. In addition, the problem of specifying a unique flow geometry where both matrix and fracture-dominated, non-Darcy flow effects are possible is analyzed using a large amount of field and laboratory data in conjunction with a theoretical treatment that reviews the existing state of the art in reservoir mechanics.« less

Flow in aquifers when the permeability varies with depth / Coulement dans les aquifères quand la perméabilité varie en raison directe de la profondeur

Abstract: When the permeability of an aquifer varies with depth, the velocity of the water varies in proportion to the permeability. A numerical method of solution is introduced which Represents this feature. Examples are cited which demonstrate that this variation in permeability influences the amount of water that is stored in the aquifer following recharge.

Non-Darcy Transient Radial Gas Flow Through Porous Media

Abstract: Canadian researchers at the Univ. of Alberta and the Univ. of Calgary have developed a computer program to solve the nonlinear partial differential equations describing transient radial gas flow through porous media. Specifically, the program can handle 4 sets of boundary conditions encountered in a finite radial system. The program has been employed to obtain pressure distributions and mass fluxes as functions of time and position for the constant-terminal rate case and the constant-terminal pressure case, in porous media having different values of permeability, inertial-resistance coefficient, slip coefficient, and rock compressibility. Changes of gas properties with pressure were taken into account. Results indicate that each of these rock properties can, under certain conditions, appreciably affect the transient response. For instance, it was observed that slip, rather than being a laboratory curiosity, can affect the transient response in a typical tight reservoir.

Estimation of two-phase petroleum reservoir properties

Abstract: The estimation of petroleum reservoir properties on the basis of production rate and pressure observations at the wells is an essential component in the prediction of reservoir behavior. The reservoir properties to be estimated appear as parameters in the partial differential equations describing the flow of fluids in the reservoir. The estimation of these properties is referred to variously as the inverse or identification problem or as history matching. In this dissertation, new results have been obtained pertaining to the estimation of petroleum reservoir properties. Most of the prior analysis of the reservoir parameter estimation problem has been confined to reservoirs containing a single fluid phase, e.g., oil. We consider here reservoirs that contain two fluid phases, e.g., oil and water. The parameters to be estimated in such a case are the porosity and permeability, which depend on spatial location, and the saturation-dependent relative permeabilities. In this work we treat two basic problems in reservoir parameter estimation: (1) establishing the ability to estimate the desired parameters (so-called identifiability), and (2) developing and testing a new algorithm, based on optimal control theory, to carry out the estimation. In regard to problem (1), we have extended the classic analytical (Buckley-Leverett) solution for incompressible flow to heterogeneous reservoirs. Analysis for an incompressible water flooding situation shows that the spatially varying properties at locations behind the saturation front have an effect on the pressure solution. The spatially varying properties can be uniquely determined based on data taken up to the time of water breakthrough. Only an integral value of the porosity can be determined from the water-oil ratio data alone; however, the spatially varying porosity may be determined when the initial saturation varies with location. The values of the relative permeabilities which are identifiable, and the information about the relative permeabilities obtained for other intervals of saturation, is established. Analytical expressions are derived for the sensitivity of the pressure and water-oil ratio observations to parameters appearing in functional forms of the relative permeabilities. When the relative permeabilities are represented as exponential functions, the coefficients and exponents can be uniquely determined. For problem (2), an algorithm is developed for the estimation of porosity, permeability and the relative permeabilities for two-phase, compressible reservoirs. This work represents the first study for which relative permeabilities have been estimated based on a model generally used to represent fluid flow in petroleum reservoirs. An objective function, composed of the weighted sum of squares of the deviations between the observed and calculated values of pressure and water-oil ratio, is minimized by a first-order gradient method based on optimal control theory. The algorithm is tested for one and two-dimensional hypothetical water floods. The algorithm performed well for problems in which the porosity, permeability and relative permeability exponents were simultaneously estimated. The increase from one to two spatial variables does not appear to change the properties of the estimation problem. Small observation errors are shown not to significantly affect the convergence of the estimates.

Gaseous carbon dioxide feeding apparatus

Abstract: PURPOSE: A gaseous carbon dioxide feeding apparatus for storing a food, having a gas-permeable bag containing a bag containing an aqueous solution of a carbohydrate and a support containing a yeast, and readily utilizable in general home. CONSTITUTION: A dried yeast 2 active even at a low temperature, e.g. beer yeast, is adhered to a support 1, e.g. a ceramic solid or paper, made of a hygroscopic material. A bag 3 made of water-resistant material readily broken by the artificial external force contains an aqueous solution 4 of a carbohydrate, e.g. glucose, therein. A bag 6 containing the support 1 and the bag 3 has a great gas permeability, is made of a material which will not evaporate the internal yeast 2 and protected from atmospheric moisture and external force by a bag 7. A heat insulating material 5 having a greast gas permeability may be used. The apparatus is used by the following method: The bag 7 is removed, and the bag 3 is then broken without damaging the bag 6. The solution 4 is made to flow over and absorbed in the support 1. The yeast 2 is activated with the solution 4 to start the evolution of CO 2 . The resultant apparatus is then introduced into a food storing bag with a food, sealed up and placed in a refrigerator. COPYRIGHT: (C)1981,JPO&Japio

Effect of permeability on cooling of a magmatic intrusion in a geothermal reservoir

Abstract: Transient cooling of magmatic intrusion in a geothermal reservoir due to conduction and convection is studied. The effects of overlying cap rock and different horizontal and vertical permeability of the reservoir are considered. Results are compared to the data from Salton Sea Geothermal Field. It is also observed that multiple layers of convection cells exist when horizontal permeability is much larger than the vertical permeability. The sharp dropoff of surface heat flow observed at Salton Sea Geothermal Field is confirmed by numerical results. Based on these numerical results, it is possible to speculate that the age of the intrusive body is about 8000 to 12,000 years.

Method of increasing porosity and permeability of subsurface rock formations to increase efficiency of secondary hydrocarbon recovery operations

Abstract: The permeability and porosity of subsurface rock formations are enhanced by injecting a fluid into the formation together with carbon dioxide, an ammonium ion source, and a catalyst system that includes a free chloride ion source, a free nitrate ion source, and an anionic hydrophile dissolved in a polar solvent.