Showing papers on "Permeability (earth sciences) published in 2010"

Effective Correlation of Apparent Gas Permeability in Tight Porous Media

Abstract: Gaseous flow regimes through tight porous media are described by rigorous application of a unified Hagen–Poiseuille-type equation. Proper implementation is accomplished based on the realization of the preferential flow paths in porous media as a bundle of tortuous capillary tubes. Improved formulations and methodology presented here are shown to provide accurate and meaningful correlations of data considering the effect of the characteristic parameters of porous media including intrinsic permeability, porosity, and tortuosity on the apparent gas permeability, rarefaction coefficient, and Klinkenberg gas slippage factor.

A New Coal-Permeability Model: Internal Swelling Stress and Fracture–Matrix Interaction

Abstract: We have developed a new coal-permeability model for uniaxial strain and constant confining-stress conditions The model is unique in that it explicitly considers fracture–matrix interaction during coal-deformation processes and is based on a newly proposed internal swelling stress concept This concept is used to account for the impact of matrix swelling (or shrinkage) on fracture-aperture changes resulting from partial separation of matrix blocks by fractures that do not completely cut through the whole matrix The proposed permeability model is evaluated using data from three Valencia Canyon coalbed wells in the San Juan Basin, where increased permeability has been observed during CH4 gas production, as well as using published data from laboratory tests Model results are generally in good agreement with observed permeability changes The importance of fracture–matrix interaction in determining coal permeability, demonstrated in this study using relatively simple stress conditions, underscores the need for a dual-continuum (fracture and matrix) mechanical approach to rigorously capture coal-deformation processes under complex stress conditions, as well as the coupled flow and transport processes in coal seams

Lattice-Boltzmann studies of fluid flow in porous media with realistic rock geometries

Abstract: We present results of lattice-Boltzmann simulations to calculate flow in realistic porous media. Two examples are given for lattice-Boltzmann simulations in two- and three-dimensional (2D and 3D) rock samples. First, we show lattice-Boltzmann simulation results of the flow in quasi-two-dimensional micromodels. The third dimension was taken into account using an effective viscous drag force. In this case, we consider a 2D micromodel of Berea sandstone. We calculate the flow field and permeability of the micromodel and find excellent agreement with Microparticle Image Velocimetry (@m-PIV) experiments. Then, we use a particle tracking algorithm to calculate the dispersion of tracer particles in the Berea geometry, using the lattice-Boltzmann flow field. Second, we use lattice-Boltzmann simulations to calculate the flow in Bentheimer sandstone. The data set used in this study was obtained using X-ray microtomography (XMT). First, we consider a single phase flow. We systematically study the effect of system size and validate Darcy's law from the linear dependence of the flux on the body force exerted. We observe that the values of the permeability measurements as a function of porosity tend to concentrate in a narrower region of the porosity, as the system size of the computational sub-sample increases. Finally, we compute relative permeabilities for binary immiscible fluids in the XMT rock sample.

Hydraulic fracturing stimulation techniques and formation damage mechanisms—Implications from laboratory testing of tight sandstone-proppant systems

Abstract: Reservoir formation damage may seriously affect the productivity of a reservoir during various phases of fluid recovery from the subsurface. Hydraulic fracturing technology is one tool to overcome inflow impairments due to formation damage and to increase the productivity of reservoirs. However, the increase in productivity by hydraulic fracturing operations can be limited by permeability alterations adjacent to the newly created fracture face. Such an impairment of the inflow to the fracture is commonly referred to as fracture face skin (FFS). Here, we focus on mechanically induced fracture face skin, which may result from stress-induced mechanical interactions between proppants and reservoir rock during production. In order to achieve sustainable, long-term productivity from a reservoir, it is indispensable to understand the hydraulic and mechanical interactions in rock–proppant systems. We performed permeability measurements on tight sandstones with propped fractures under stress using two different flow cells, allowing to localise and quantify the mechanical damage at the fracture face. The laboratory experiments revealed a permeability reduction of this rock–proppant system down to 77% of initial rock permeability at 50 MPa differential stress leading to a permeability reduction in the fracture face skin zone up to a factor of 6. Considerable mechanical damage at the rock–proppant interface was already observed for stresses of about 5 MPa. Microstructure analysis identified quartz grain crushing, fines production, and pore space blocking at the fracture face causing the observed mechanically induced FFS. At higher stresses, damage and embedment of the ceramic proppants further reduces the fracture permeability. Therefore, even low differential stresses, which are expected under in-situ conditions, may considerably affect the productivity of hydraulic proppant fracturing stimulation campaigns, in particular in unconventional reservoirs where the fracture face is considerably larger compared to conventional hydraulic stimulations.

Darcy's law‐based model for wicking in paper‐like swelling porous media

Abstract: The wicking of liquid into a paper-like swelling porous medium made from cellulose and superabsorbent fibers was modeled using Darcy's law. The work is built on a previous study in which the Washburn equation, modified to account for swelling, was used to predict wicking in a composite of cellulose and superabsorbent fibers. In a new wicking model proposed here, Darcy's law for flow in porous media is coupled with the mass conservation equation containing an added sink or source term to account for matrix swelling and liquid absorption. The wicking-rate predicted by the new model compares well with the previous experimental data, as well as the modified Washburn equation predictions. The effectiveness of various permeability models used with the new wicking model is also investigated. © 2010 American Institute of Chemical Engineers AIChE J, 2010

Permeability Reduction in Pervious Concretes due to Clogging: Experiments and Modeling

Abstract: The ability of in-place pervious concretes to effectively drain storm water runoff gradually reduces as it becomes clogged due to the ingress of fine particles into its pore structure. This study systematically investigates several pervious concrete mixtures propor- tioned using different size aggregates and their blends on their propensity to clogging so as to bring out the influence of pore structure features on particle retention and the consequent permeability reduction. A finer and a coarser sand are used as clogging materials and the experimental study on permeability reduction as a result of particle retention is carried out using a falling head permeability cell. Significant permeability reductions are observed when finer sand is used as the clogging material. A certain effective pore size to clogging particle size ratio is found in this study, that is most conducive to particle retention. Thus pervious concrete specimens of similar porosity, having very large 5-6 mm or very small 1-2 mm pore sizes are found to be less susceptible to clogging under the conditions of this study. An idealized three-dimensional geometry obtained from two-dimensional planar images of pervious concrete sections is used, along with a probablistic particle capture model to predict particle retention associated with clogging material addition and simulated runoff. The trends in the predicted particle retention and the experimentally determined permeability reduction agree well. A "clogging potential" is defined in this paper, either as a ratio of the porosity reduction because of clogging to the initial porosity, or as a ratio of the permeability reduction to the permability in the unclogged state. DOI: 10.1061/ASCEMT.1943-5533.0000079 CE Database subject headings: Concrete; Clogging; Porosity; Permeability; Experimentation. Author keywords: Pervious concrete; Pore structure; Clogging; Porosity; Permeability; Clogging potential; Particle capture model.

Coupled deformation–flow analysis for methane hydrate extraction

Abstract: Methane hydrate is estimated to be present in substantial amounts below deep sea floors. Particular scientific and engineering interests that encourage studies of mechanical behaviour of methane hydrate soils include submarine geohazards, such as the initiation of marine landslides through hydrate dissociation, wellbore stability and estimation of future gas production from wells. To study these problems, a formulation of a multi-physics model of methane hydrate flow coupled to soil deformation is developed. By assuming deformable porous media (soil matrix) that accommodate non-movable but dissociable hydrate, a two-phase flow formulation of water and methane gas is suggested according to Darcy's law and capillary pressure law. A single-phase elastic–perfectly plastic constitutive model for hydrate soil sediments, based on the concept of effective stress, is developed to account for the effect of hydrate saturation on mechanical strength and stiffness. The formulation is incorporated into the explicit sch...

Analysis of Mechanisms of Flow in Fractured Tight-Gas and Shale-Gas Reservoirs

Abstract: In this paper we analyze by means of numerical simulation the mechanisms and processes of flow in two types of fractured tight gas reservoirs: shale and tight-sand systems. The numerical model includes Darcy’s law as the basic equation of multiphase flow and accurately describes the thermophysical properties of the reservoir fluids, but also incorporates other options that cover the spectrum of known physics that may be involved: non-Darcy flow, as described by a multi-phase extension of the Forschheimer equation that accounts for laminar, inertial and turbulent effects; stress-sensitive flow properties of the matrix and of the fractures, i.e., porosity, permeability, relative permeability and capillary pressure; gas slippage (Klinkenberg) effects; and, non-isothermal effects, accounting for the consequences of energy balance and temperature changes in the presence of phenomena such as Joule-Thompson cooling in the course of gas production. The flow and storage behavior of the fractured media (shale or tight sand) is represented by various options of the Multiple Interactive Continua (MINC) conceptual model, in addition to an Effective Continuum Method (ECM) option, and includes a gas sorption term that follows the Langmuir isotherm. Comparison to field data, analysis of the simulation results and parameter determination through history matching indicates that (a) the ECM model is incapable of describing the fractured system behavior, and (b) shale and tight-sand reservoirs exhibit different behavior that can be captured (albeit imperfectly) using some of the more complex options of the multi-continua fractured-system models. The sorption term is necessary to describe the behavior of shale gas reservoirs, and significant deviations from the field data are observed if it is omitted. Conversely, production data from tight-sand reservoirs can be adequately represented without accounting for gas sorption. All the other processes and mechanisms allow refinement of the match between predictions and observations, but appear to have secondorder effects in the description of flow through fractured tight gas reservoirs.

3D numerical modeling of hydrothermal processes during the lifetime of a deep geothermal reservoir

Abstract: Understanding hydrothermal processes during production is critical to optimal geothermal reservoir management and sustainable utilization. This study addresses the hydrothermal (HT) processes in a geothermal research doublet consisting of the injection well E GrSk3/90 and production well Gt GrSk4/05 at the deep geothermal reservoir of Gros Schonebeck (north of Berlin, Germany) during geothermal power production. The reservoir is located between −4050 to −4250 m depth in the Lower Permian of the Northeast German Basin. Operational activities such as hydraulic stimulation, production (T = 150°C; Q = −75 m3 h−1; C = 265 g l−1) and injection (T = 70°C; Q = 75 m3 h−1; C = 265 g l−1) change the HT conditions of the geothermal reservoir. The most significant changes affect temperature, mass concentration and pore pressure. These changes influence fluid density and viscosity as well as rock properties such as porosity, permeability, thermal conductivity and heat capacity. In addition, the geometry and hydraulic properties of hydraulically induced fractures vary during the lifetime of the reservoir. A three-dimensional reservoir model was developed based on a structural geological model to simulate and understand the complex interaction of such processes. This model includes a full HT coupling of various petrophysical parameters. Specifically, temperature-dependent thermal conductivity and heat capacity as well as the pressure-, temperature- and mass concentration-dependent fluid density and viscosity are considered. These parameters were determined by laboratory and field experiments. The effective pressure dependence of matrix permeability is less than 2.3% at our reservoir conditions and therefore can be neglected. The results of a three-dimensional thermohaline finite-element simulation of the life cycle performance of this geothermal well doublet indicate the beginning of thermal breakthrough after 3.6 years of utilization. This result is crucial for optimizing reservoir management. Geofluids (2010) 10, 406–421

Reservoir quality modeling of tight-gas sands in Wamsutter field: Integration of diagenesis, petroleum systems, and production data

Abstract: The Late Cretaceous Almond Formation is a lithic-rich, tight-gas sandstone reservoir in Wamsutter field, Wyoming. The Almond has measured porosities of less than 12% and permeabilities that are generally less than 0.1 md. This is the result of significant mechanical and chemical compaction, precipitation of carbonate cements and authigenic clays, and deep-burial cementation by quartz. Despite the advanced diagenesis and poor reservoir quality of this tight-gas sandstone, Touchstone diagenetic modeling was used successfully to simulate rock properties during burial. Basin modeling and fluid inclusion data were integrated with Touchstone™ simulations to constrain the timing of petroleum charge into the reservoir. Model results indicate that the Almond was initially charged by liquid petroleum, when the reservoir retained high porosity and permeability. Subsequent gas charging flushed most of the liquids from the system as the reservoir continued to experience porosity and permeability reduction from continued quartz cementation. The Almond Touchstone model was applied to 15 well locations throughout the field, ranging from areas of low thermal stress to high thermal stress. A comparison of Touchstone-predicted permeability and standard thermal stress yielded a correlation that was used to build a pseudopermeability reservoir quality risk map across the Wamsutter area. A comparison of this map with historical production data demonstrates that the map successfully predicts areas of enhanced well performance. The method used to build this risk map may be applied elsewhere as a quick means of high grading areas of risk during field development.

Evaluation of trapping mechanisms in geologic CO2 sequestration: Case study of SACROC northern platform, A 35-year CO2 injection site

Abstract: CO2 trapping mechanisms in geologic sequestration are the specific processes that hold CO2 underground in porous formations after it is injected. The main trapping mechanisms of interest include (1) fundamental confinement of mobile CO2 phase under low-permeability caprocks, or stratigraphic trapping, (2) conversion of CO2 to mineral precipitates, or mineral trapping, (3) dissolution in in situ fluid, or solubility trapping, and (4) trapping by surface tension (capillary force) and, correspondingly, remaining in porous media as an immobile CO2 phase, or residual CO2 trapping. The purpose of this work is to evaluate and quantify the competing roles of these different trapping mechanisms, including the relative amounts of storage by each. For the sake of providing a realistic appraisal, we conducted our analyses on a case study site, the SACROC Unit in the Permian basin of western Texas. CO2 has been injected in the subsurface at the SACROC Unit for more than 35 years for the purpose of enhanced oil recovery. Our analysis of the SACROC production and injection history data suggests that about 93 million metric tons of CO2 were injected and about 38 million metric tons were produced from 1972 to 2005. As a result, a simple mass-balance suggests that the SACROC Unit has accumulated approximately 55 million metric tons of CO2. Our study specifically focuses on the northern platform area of the SACROC Unit where about 7 million metric tons of CO2 is stored. In the model describing the SACROC northern platform, porosity distributions were defined from extensive analyses of both 3-D seismic surveys and calibrated well logging data from 368 locations. Permeability distributions were estimated from determined porosity fields using a rock-fabric classification approach. The developed 3-D geocellular model representing the SACROC northern platform consists of over 9.4 million elements that characterize detailed 3-D heterogeneous reservoir geology. To facilitate simulation using conventional personal computers, we upscaled the 9.4 million elements model using a “renormalization” technique to reduce it to 15,470 elements. Analysis of groundwater chemistry from both the oil production formations (Cisco and Canyon Groups) and the formation above the sealing caprock suggests that the Wolfcamp Shale Formation performs well as a caprock at the SACROC Unit. However, results of geochemical mixing models also suggest that a small amount of shallow groundwater may be contaminated by reservoir brine possibly due to: (1) downward recharge of recycled reservoir brine from brine pits at the surface, or (2) upward leakage of CO2-saturated reservoir brine through the Wolfcamp Shale Formation. Using the upscaled 3-D geocellular model with detailed fluid injection/production history data and a vast amount of field data, we developed two separate models to evaluate competing CO2 trapping mechanisms at the SACROC northern platform. The first model simulated CO2 trapping mechanisms in a reservoir saturated with brine only. The second model simulated CO2 trapping mechanisms in a reservoir saturated with both brine and oil. CO2 trapping mechanisms in the brine-only model show distinctive stages accompanying injection and post-injection periods. In the 30-year injection period from 1972 to 2002, the amount of mobile CO2 increased to 5.0 million metric tons without increasing immobile CO2, and the mass of solubility-trapped CO2 sharply rose to 1.7 million metric tons. After CO2 injection ceased, the amount of mobile CO2 dramatically decreased and the amount of immobile CO2 increased. Relatively small amounts of mineral precipitation (less than 0.2 million metric tons of CO2 equivalent) occurred after 200 years. In the brine-plus-oil model, dissolution of CO2 in oil (oil-solubility trapping) and mobile CO2 dominated during the entire simulation period. While supercritical-phase CO2 is mobile near the injection wells due to the high CO2 saturation, it behaves like residually trapped CO2 because of the small density contrast between oil and CO2. In summary, the brine-only model reflected dominance by residual CO2 trapping over the long term, while CO2 in the brine-plus-oil model was dominated by oil-solubility trapping.

Non-isothermal Permeability Impairment by Fines Migration and Deposition in Porous Media including Dispersive Transport

Abstract: Particle migration and deposition, and resulting permeability impairment occurring in porous media are described by a practical phenomenological model considering temperature variation and particle transport by advection and dispersion. Variation of the filter coefficient and permeability of porous matrix by temperature and particle deposition, and other essential factors are considered by means of the special correlations of the relevant variables and dimensionless numbers. Comparison of the numerical results, obtained using a finite-difference numerical scheme with and without considering the dispersion mechanism and temperature variation, reveals the significance of such effects on fines migration and deposition, and consequent permeability impairment in porous media. Improved model presented in this article can be instrumental for scientifically guided experimentation, analysis, and optimal design of processes involving in transport of colloidal and fine particles through geological subsurface formations.

Permeability Measurement Methods in Porous Media of Fiber Reinforced Composites

Abstract: Accurate measurement of permeability is critical for fluid flow modeling in porous media. Various experimental methods devised to measure permeability as a porous material property in composites are reviewed. Liquid flow and gas flow methods of permeability measurement for in-plane and transverse directions specifically for fiber-reinforced composites are discussed, as well as issues related to these methods and some associated permeability models. Alternative methods of permeability determination based on cross transport phenomenon are reviewed as well. DOI: 10.1115/1.4001047