Showing papers on "Permeability (earth sciences) published in 1977"

Theoretical derivation of Darcy's law

Abstract: Darcy's law for anisotropic porous media is derived from the Navier-Stokes equation by using a formal averaging procedure. Particular emphasis is placed upon the proof that the permeability tensor is symmetric. In addition, it is shown that there is a one-to-one relationship between the local and macroscopic velocity fields. This leads to the interesting phenomenological observation that the local velocity vector at any given point must always lie either on a fixed line or in a fixed plane. All of this holds true for an incompressible homogeneous Newtonian fluid moving slowly through a rigid porous medium with uniform porosity under isothermal and steady state conditions. The question whether Darcy's law is applicable under nonsteady or compressible flow conditions, or when the medium has nonuniform porosity, is also discussed. Finally, it is shown that the Hagen-Poiseuille equation, as well as the expression describing Couette flow between parallel plates, can be derived from the equations presented in this work and may thus be viewed as special cases of Darcy's law.

Plugging high permeability zones of reservoirs having heterogeneous permeability

Abstract: A method of forming a mixed plug in the more permeable zones of a subterranean reservoir of nonuniform permeability in which there is injected into the reservoir aqueous solutions of: a polymer, a material that reacts with the polymer to form a time-delayed polymer-containing plug, an alkali metal silicate and a material that reacts with the silicate to form a time-delayed silicate-containing plug. The injected solutions are either admixed at the surface prior to injection or are simultaneously injected so that a mixed polymer-silicate plug is formed in the reservoir.

Compressible fluid flow through rocks of variable permeability

Abstract: The effectiveness of course-grained igneous rocks as shelters for burying radioactive waste can be assessed by determining the rock permeabilities at their in situ pressures and stresses. Analytical and numerical methods were used to solve differential equations of one-dimensional fluid flow through rocks with permeabilities from 10/sup 4/ to 1 nD. In these calculations, upstream and downstream reservoir volumes of 5, 50, and 500 cm/sup 3/ were used. The optimal size combinations of the two reservoirs were determined for measurements of permeability, stress, strain, acoustic velocity, and electrical conductivity on low-porosity, coarse-grained igneous rocks.

Experimental Study of Fracture Permeability in Porous Rock

Abstract: Fluid flow through fractured porous subsurface reservoirs is an important but often unquantified property. The necessary quantification of this flow is achieved by both laboratory and field measurements. Laboratory experiments of the effect of temperature and confining pressure on permeability in Navajo Sandstone indicate that simulated fractures in porous rock (1) have a higher percentage rate of permeability decline with depth than whole rock, (2) experience a greater degree of permanent deformation with depth than whole rock, (3) are healed effectively when fracture permeabilty approaches that of the whole rock, and (4) experience a reduction in permeability dependent on the macroscopic ductility and previous maximum depth of burial of the host sandstone.

Binary gas diffusion of methane-nitrogen through porous solids

Abstract: Diffusion rates of nitrogen and methane have been measured across ten porous solids at 35°C and 1 atm by a steady state flow method. The porous plugs used were cylindrical in shape, with diffusion occurring in the direction of the axis. Diffusion data were taken with porous cores either dry or saturated with liquids. Water and n-heptane were used as saturating liquids. The rather complex internal structure of porous solids were indirectly characterized through some auxiliary measurements. These included porosity, permeability, and electrical resistivity factor (yet another indirect measurement of tortuosity). The effective diffusion coefficients were correlated for the gas phase diffusion as a function of porosity. The ratio of effective diffusion coefficient to the open space diffusion coefficient (De/Do) was correlated for dry cores using the properties approximately characterizing the pore structure.

Determination of permeability in anisotropic rock-masses from integral samples

Abstract: A method is presented which makes it possible to characterize the permeability of a rock mass as an anisotropic magnitude--i.e. to determine its permeability tensor--from a characterization of its fracturing by means of intergral samples. For the purpose, a theory is developed by means of which the permeability tensor can be calculated from the attitudes and openings of the fractures and--if infillings are present--also from their coefficient of permeability. All these magnitudes are determined in integral samples it being assumed that the sampled fractures are continuous and plane, and have the same characteristics as the section of the fractures present in the samples. Possible deviations with respect to this assumption are taken into account by means of correcting factors derived from the results of pressure tests in situ. The permeability tensor of a rock mass at a point can be determined from a single integral sample, provided this is representative of the fracturing. Results of the application of the method are presented, which show it to look very promising. /Author/

Studies of Ventura Field, California, II: Lithology, Compaction, and Permeability of Sands

Abstract: Permeability of reservoir beds generally decreases in progressively deeper producing zones of the Ventura field. Petrographic studies indicate that the reduction of pore size in sands resulted chiefly from compaction by stress under load. The degree and trend of compaction of the Ventura field sediments have been evaluated by statistical correlations of sedimentologic data (grain size and sorting) and reservoir-engineering data (porosity and permeability). The data permitted the derivation of an empirical relation relating permeability to lithology and compaction: [EQUATION] where k is permeability in millidarcys, C an empirical number, dm the medium size in millimeters, and ^sgr^phgr the sorting expressed in ^phgr--standard deviation. Two new concepts are introduced. The granular parameter G is defined as [EQUATION] G gives a measure of the suitability of a clastic sediment as a potential reservoir bed before any diagenetic change has taken place. The empirical number C gives an expression of the degree of compaction. For any given sediment subjected to compaction, the granular parameter should remain unchanged if there has been no significant fracturing. The decrease of permeability is directly proportional to decrease of C. We thus might designate the ratio C to the Co for unconsolidated sediments as the compaction index. For any given region, a knowledge of the depositional environments of the sandy sediments should give a general knowledge of the range of granular parameters. After the degree of compaction is defined by obtaining empirically a value for compaction index, the permea ility of types of reservoir sands not yet encountered in explored zones can be estimated.

High conformance enhanced oil recovery process

Abstract: The conformance of a water flood oil recovery process, including surfactant or other chemicalized water flood process, in a formation containing at least two zones of varying permeability, the permeability of one zone being at least 50 percent greater than the permeability of the other zone, is improved by flooding until the higher permeability zone has been depleted, after which a fluid is injected into the high permeability zone, said fluid having relatively low viscosity at the time of injection and containing surface active agents which promote the formation of a coarse emulsion in the flow channels of the formation which reduces the permeability of the high permeability zone. Since the viscosity of the fluid injected into the previously water flooded, high permeability zone is no greater than water, it is injected easily into the zone and moves through substantially the same flow channels as water would move in the formation. After the permeability of the first zone has been reduced substantially, water flooding may then be accomplished in the second zone which was originally not invaded by the injected fluid since its permeability was substantially less than the permeability of the first zone. The surface active agent is tailored to exhibit optimum emulsion formation properties with the particular aqueous fluid present in the flow channels of the formation to be treated. The optimum emulsifying surfactant comprises a mixture of an alkylpolyalkoxyalkylene sulfonate or an alkylarylpolyalkoxylalkylene sulfonate and an organic sulfonate such as petroleum sulfonate.

Intrinsic viscosity and friction coefficient of permeable macromolecules in solution

Abstract: A polymer molecule in solution is treated as a porous sphere with a spherically symmetric permeability distribution. Solvent motion in and around this sphere is described by the Debije- Brinkman equation (Navier-Stokes equation and Darcy equation combined). The model allows a straightforward calculation of the frictional properties of a polymer in shear flow (intrinsic viscosity) and in translation (friction coefficient). Calculations have been carried out for a radial dependence of the permeability of the form k(r)=K exp(Qr2). The calculations provide us with 0 detailed information about the solvent flow through and around the macromolecular coil.

Preliminary Assessment of a Geothermal Energy Reservoir Formed by Hydraulic Fracturing

Abstract: Two, 3-km-deep boreholes have been drilled into hot (approximately 200/sup 0/C) graphite in northern New Mexico in order to extract geothermal energy from hot dry rock. Both boreholes were hydraulically fractured to establish a flow connection. Presently this connection has a large flow impedance which may be improved with further stimulation. Fracture-to-borehole intersection locations and in situ thermal conductivity were determined from flowing temperature logs. In situ measurements of permeability show an extremely strong dependence upon pore pressure--the permeability increased by a factor of 80 as the pressure was increased 83 bars (1200 psi). An estimate of the minimum horizontal earth stress was derived from fracture extension pressures and found to be one-half the overburden stress.

Electrical Resistivity for Estimating Permeability

Abstract: The purpose of this note is to demonstrate that relations between aquifer resistivities determined from electric resistivity soundings and aquifer permeability can be developed. This approach should be useful for applications to shallow aquifers.

Energy extraction characteristics of hot dry rock geothermal systems

Abstract: The LASL Hot Dry Rock Geothermal Energy Project is investigating methods to extract energy at useful temperatures and rates from naturally heated crustal rock in locations where the rock does not spontaneously yield natural steam or hot water at a rate sufficient to support commercial utilization. Several concepts are discussed for application to low and high permeability formations. The method being investigated first is intended for use in formations of low initial permeability. It involves producing a circulation system within the hot rock by hydraulic fracturing to create a large crack connecting two drilled holes, then operating the system as a closed pressurized-water heat-extration loop. With the best input assumptions that present knowledge provides, the fluid-flow and heat-exchange calculations indicate that unpumped (buoyant) circulation through a large hydraulic fracture can maintain a commercially useful rate of heat extraction throughout a usefully long system life. With a power cycle designed for the temperature of the fluid produced, total capital investment and generating costs are estimated to be at least competitive with those of fossil-fuel-fired and nuclear electric plants. This paper discusses the potential of the hot dry rock resource, various heat extraction concepts, prediction of reservoir performance, and economic factors, andmore » summarizes recent progress in the LASL field program.« less

Critical Water Estimates for Gulf Coast Sands

Abstract: Hydrocarbon productive sands in the Gulf Coast area exhibit wide variances in formation water saturation (Sw). Values ranging from 10 to 70 percent pore space are common. These variances are related to the capillary properties of the sand, height above the water level, fluid interfacial tensions, and density difference of the entrained fluids. This formation water may, or may not flow in appreciable quantities, depending on the water retentive characteristics of the rock, the formation relative permeability and fluid viscosities. The combined influence of these variables results in a critical upper limit for formation water saturation, above which a significant percentage of water will be produced. This limiting water saturation exceeds the irreducible saturation value and has been called the critical interstitial water (Sciw). It can be correlated with the basic rock properties of permeability and porosity. Presented herein is a generalized correlation of critical interstitial water saturations for Gulf Coast sands. This correlation allows a critical saturation to be estimated from permeability and porosity data given in a routine core analysis report. Higher critical water saturations are found as porosity increases in samples of constant permeability. Higher values are also noted as permeability decreases in samples of constant porosity. The critical interstitial water saturation also influences the interpretation of the quick-look computer calculated apparent water resistivity (Rwa) curve used to predict hydrocarbon productive zones. The Rwa/Rw multiple of three which is commonly used to indicate hydrocarbon production corresponds to a water saturation of 58 percent of pore space. Low permeability zones may yield hydrocarbons with a Rwa multiple of two, which corresponds to a water saturation of 70 percent. High permeability sands may require multiples of six or more to be hydrocarbon productive. The required multiple for a sample of any given permeability and porosity can be estimated from the generalized correlation of critical water values presented.

A model relating root permeability to flux and potentials: application to existing data from soybean and other plants.

Abstract: A model that relates hydraulic permeability to water flux and to gradients in pressure potential and solute potential was tested using soybean (Glycine max) plants. Water flux was varied by additions of polyethylene glycol 6,000 around one portion of a divided root system and by changing the light intensity and CO2 concentration around the plants. The data are compatible with the model only if the hydraulic permeability varies with flux; however, the data were insufficient for rigorous testing. Three sets of published data fit the model only if hydraulic permeability varies. Evidence originally presented as involving constant hydraulic permeability is shown, rather, to require variable hydraulic permeability.

Natural Gas From Geopressured Aquifers

Abstract: This paper examines potential for natural gas production from geopressured Gulf Coast reservoirs whose thermal and mechanical energy production would be marginal or sub-marginal in relation to requirements for electricity generation. A base case evaluation with reservoir characteristics similar to those previously published for Frio Formation reservoirs in South Texas revealed reservoir criteria for producing natural gas to be much less stringent than for electricity generation. Parametric studies of cost for producing natural gas as the value of individual reservoir parameters is varied to reveal maximum sensitivity to those parameters most difficult to quantify. These are effective in-situ permeability, pay zone thickness, reservoir drive and drainage area. Potential significance of reservoir characteristics not reflected in the calculations are qualitatively discussed. These are the pressure dependence of compaction drive and permeability, the possibility of a gas drive due to gas trapped in pores as a result of relative permeability and the possibility of an increasing gas/water ratio due to expansion of the trapped gas resulting in finite permeability to natural gas.

Interaction between water flow and the mechanical behaviour of soil or rock masses

Abstract: THE AUTHORS STUDY THE LAWS GOVERNING THE MECHANICAL EFFECTS DUE TO WATER FLOW IN MASSES AND DEFINE THE MEANS BY WHICH THESE EFFECTS CAN BE TAKEN INTO ACCOUNT IN CALCULATIONS, BY USING, FOR EXAMPLE, MATHEMATICAL MODELS FOR THE SIMULATION OF THE MECHANICAL BEHAVIOUR OF MASSES (FINITE ELEMENT METHOD). THE NUMERICAL APPROACH USES BOTH HYDRAULIC AND MECHANICAL MODELS. THIS COUPLING CAN BE OBTAINED FOR A FIXED GEOMETRY MASS (I.E. CONSTANT PERMEABILITY) OR FOR A VARIABLE GEOMETRY MASS WITH PERMEABILITY AS A FUNCTION OF THE STRAIN STATE. IN THIS CASE THE SOLUTION IS OBTAINED BY SUCCESSIVE HYDRAULIC AND MECHANICAL SIMULATION.

High conformance oil recovery process

Abstract: The conformance of an enhanced oil recovery process, including waterflood, surfactant or other chemicalized water flood process, in a formation containing at least two strata or zones of varying permeability, the permeability of one zone being at least 50 percent greater than the permeability of the other zone, is improved by flooding until the higher permeability zone has been depleted, after which an aqueous fluid is injected into the high permeability zone, said fluid having relatively low viscosity at the time of injection and containing a particular surface active agent which promotes the formation of a coarse emulsion in the flow channels of the formation which reduces the permeability of the high permeability zone. After the permeability of the first zone has been reduced substantially, flooding may then be accomplished in the second zone which was originally not invaded by the injected oil recovery fluid since its permeability was substantially less than the permeability of the first zone. The surface active agents are individually tailored and the ratio of dissimilar surfactants balanced to exhibit optimum emulsion formation properties with the particular aqueous fluid present in the flow channels of the formation to be treated.

A water zone propagating through a permeable rock

Abstract: A Water Zone Propagating Through a Permeable Rock A one-dimensional front of a water zone penetrating an initially dry permeable medium is studied theoretically as well as experimentally. The theory includes the case when the permeability varies with position. Simple experiment and theory show that the front of the water zone increases as the square root of time if the permeability is constant. A method is suggested to measure the non-constant permeability by measuring the penetration rate.

A simple technique for measuring the permeability of coniferous wood and its application to the study of water conduction in living trees

Abstract: A method is described for measuring the permeability to water of fresh coniferous wood samples in accordance with the provisions of Darcy's Law describing fluid flow through porous media. Departures from this law are also described and briefly discussed.