Permeability (earth sciences)

About: Permeability (earth sciences) is a research topic. Over the lifetime, 15424 publications have been published within this topic receiving 288535 citations.

Flow Unit Concept--Integrated Approach to Reservoir Description for Engineering Projects: ABSTRACT

Abstract: The successful application of secondary and tertiary oil recovery technology requires an accurate understanding of the internal architecture of the reservoir. Engineers have difficulty incorporating geological heterogeneity in their numerical models for simulating reservoir behavior. The concept of flow units has been developed to integrate geological and engineering data into a system for reservoir description. A flow unit is a volume of the total reservoir rock within which geological and petrophysical properties that affect fluid flow are internally consistent and predictably different from properties of other rock volumes (i.e., flow units). Flow units are defined by geological properties, such as texture, mineralogy, sedimentary structures, bedding contacts, and the nature of permeability barriers, combined with quantitative petrophysical properties, such as porosity, permeability, capillarity, and fluid saturations. Studies in the subsurface and in surface outcrops have shown that flow units do not always coincide with geologic lithofacies. The flow unit approach provides a means of uniquely subdividing reservoirs into volumes that approximate the architecture of a reservoir at a scale consistent with reservoir simulations. Thus, reservoir engineers can incorporate critical geological information into a reservoir simulation without greatly increasing the complexity of their models. This approach has advantages over more traditional methodsmore » of reservoir zonation whereby model layers are determined on the basis of vertical distributions of permeability and porosity from core analyses and wireline logs.« less

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.

A multiscale study of the permeability of a thick clayey till

Abstract: We describe and evaluate two previously undocumented methods of bulk permeability (K) determination and compare results obtained with results of conventional smaller-scale tests on the same thick clayey till deposit. Analysis of the downward propagation of seasonal water table fluctuations yielded bulk K of approximately 10−10 m s−1, in close agreement with results of laboratory consolidation and permeameter tests, slug tests, and distribution of vertical hydraulic gradient with depth in the deposit. This agreement suggests that for such materials, high-gradient tests conducted at small scales of distance and time can provide reasonable estimates of bulk K. The results also imply groundwater residence times in the till of thousands of years. The flow pattern observed near a large excavation in the till was consistent with the initial recoveries of piezometers installed in much smaller boreholes, assuming perturbation of hydraulic head in the formation due to borehole excavation. Time scales of these perturbations, which prevent interpretation of measured hydraulic head using conventional well hydraulic methods, varied from months to tens of years.