Mudrocks have complex petrophysical properties due, in part, to their very fine grain size and the associated high specific surface area (m2/g) and cation exchange capacity (CEC, meq/g). The role of ...the cation exchange capacity and its associated bound water must be included to account for mudrock electrical, transport, and mechanical properties. A widely varying set of samples from the deep water Gulf of Mexico Miocene section, the arctic seafloor, the Pierre Shale, and Brazos River sand (used for varying sand content) were resedimented to study the effects of these variations on compaction and permeability. The mudrocks were characterized in terms of CEC, clay mineral content, bulk mineralogy, and particle size distribution. Resedimentation techniques were employed to measure the mudrock properties under controlled conditions i.e. slurries were made with known clay mineral type, bulk mineralogy, particle size distribution, CEC, and pore fluid salinity, and subsequently compacted in an oedometer cell.
The measured permeabilities were found to be strongly dependent on the clay mineral CEC and on initial pore fluid salinity. Two models were developed to explain the variation in measured permeability: a modified Carman-Kozeny model and a staged differential effective medium model (SDEM). The Carman-Kozeny model fits the permeability data to within a factor of three but underestimates the stress dependence. The SDEM model includes the effects of both bound water saturation and porosity on fluid flow. The model was also able to estimate permeability for all the different mudrocks to within a factor of three with an improved match to the stress dependence. These two models were also successfully tested using previously published permeability data for both resedimented and intact Boston Blue clay samples.
A compaction model for porosity was also developed and applied to published data for artificial mixtures of smectite and kaolinite. The model predicts the stress dependent porosity of the resedimented clays to within four percent error. It is then extended to incorporate the influence of the inclusion of sand sized material and applied to our resedimentation data and previously published Boston Blue Clay data. The required inputs for the model include the weight fraction of non-clay sized material, and the cation exchange capacity (CEC, meq/gram). No consistent salinity dependence was observed for compaction.
•Developed models for the stress dependent porosity and permeability of mudrocks.•Porosity is a function of clay type (CEC) and volume of the non-clay size fraction (presence of shelter pores).•Porosity model agrees well with observed porosity in Gulf of Mexico subsurface samples.•Carman-Kozeny and SDEM models for permeability agreed with measurements to within a factor of 3.
Conductivity optimization is important for hydraulic fracturing due to its key roles in determining fractured well productivity. Proppant embedment is an important mechanism that could cause a ...remarkable reduction in fracture width and, thus, damage the fracture conductivity. In this work a new analytical model, based on contact mechanics and the Carman-Kozeny model, is developed to calculate the embedment and conductivity for the sparse distribution of proppant packs. Features and controlling factors of embedment, residual width and conductivity are analyzed. The results indicate an optimum distance between proppant packs that has the potential to maintain the maximum conductivity after proppant embedment under a sparse distribution condition. A change in the optimum distance is primarily controlled by closure pressure, the rock elastic modulus and the proppant elastic modulus. The proppant concentrations and the poroelastic effect do not influence this optimum distance.
A Lattice–Boltzmann method is used to calculate grain-scale, low Reynolds number, single phase, interstitial porous melt flow in two independent igneous microstructures: 1) a microstructure simulated ...using a stochastic algorithm for progressive crystallization, and 2) a natural microstructure obtained through X-ray Computed Tomography (CT) of a partially melted basalt. In both cases, the error in the calculated flow field due to finite discretization and domain size has been estimated or demonstrated to be insignificant. Visually, the porous melt flow tends to localize into high flux channels, especially with increasing crystallinity, and this impression is quantitatively confirmed by increasing skewness of the velocity distribution in the direction parallel to the imposed pressure gradient driving the flow. A change from uniform to localized melt flow in naturally occurring situations may have a profound effect on the distribution of trace elements and, if the melt is reactive, the chemical and structural evolution of the igneous microstructure through localized phase change. Permeabilities of both microstructures are determined from the calculated steady flow field. The permeabilities are then fitted to two different correlation models which are based on the Rumpf–Gupte and Carman–Kozeny relations. In these models, we express permeability as functions of melt fraction and either the mean crystal length or specific surface area. Extrapolated permeability to higher melt fractions using both correlation models for the partially melted basalt is shown to be within a factor of four of experimentally determined permeability of a similar sample. We determine permeability estimates in the relatively unexplored melt fraction range of 30%–80% and find consistency with previous work for permeability estimates in the melt fraction range of 20%–30%.
We have examined the properties of a new class of microfiltration and ultrafiltration membranes that are fabricated by assembling particles onto the surface of a microporous substrate and stabilizing ...the porous array into a composite. The particle array contains interstitial voids having a narrow size distribution that serve as channels for size sieving. This aqueous based technology has advantages relative to other membrane fabrication methods in terms of the control of asymmetry, the facile adjustment of pore size, and the ability to easily modify pore surfaces during the synthesis of particles. In this work we study the properties of the membranes (gas and water permeabilities) fabricated from different size particles and of varying thickness on a number of different supports. The experimental data is then analyzed with a standard model, Carman–Kozeny, to develop guidelines for the design of such membranes. For all of the composites, the volume porosity was found to be approximately 0.3, close to what would be expected for hexagonal closest packed array which corresponds to the visual appearance from electron micrographs. In this study, membranes with narrow pore size distributions from 0.038 to 0.122
μm were fabricated with fluxes three to four times higher than the commercial membranes of similar pore size manufactured by phase inversion processes.
The presence of oil in the environment is of major concern due to its acute toxicity and impact on human health and the environment. Thus, industries are being required to meet-stringent effluent ...standards. As a result, finding and developing innovative methods to treat oily waters effectively and economically is a necessity. In the present study, the, potential of bentonite organo-clay (modified bentonite) in the powdered and granular forms was evaluated in the removal of oil from five representative synthetic (standard mineral oil, SMO; kutwell45, KUT45; and valcool, VAL) and actual (refinery effluent, RE and produced water, PW) emulsions by a series of batch and column experiments. Bentonite was used in batch experiments to compare its oil removal efficiency with that of organo-clay. Batch kinetic experiments showed that the equilibrium time was in the range of 1 to 3 hours for bentonite, 2 to 3 hours for powdered organo-clay and 2 to 4 hours for organo-clay/anthracite mixture. The sorption of oil to bentonite was described by the Freundlich model for SMO, KUT45, VAL and PW; it followed the BET isotherm for RE. The sorption of oil to powdered organo-clay followed the Freundlich model for SMO, KUT45 and PW; it followed the Langmuir and the BET models for VAL and RE, respectively. Continuous column experiments using organo-clay/anthracite bed and various oil-in-water emulsions showed that oil removal efficiency decreased with increasing flow rate and increased with increasing depth of bed. A study on breakdown mechanisms for organo-clay/anthracite bed showed that the head-loss across the bed can well be predicted using the Carman-Kozeny filtration model for single-phase flow. It was observed that the Carman-Kozeny model may not yield accurate predictions at high flow rates in the case of two-phase flow. The analysis of the breakthrough data for RE showed that the homogeneous surface diffusion model (HSDM) exhibited a trend similar to observed values for the effluent oil concentration profiles in the case of organo-clay/anthracite beds. Based on the results obtained from batch and column experiments, bentonite organo-clay was an effective medium for oil removal from oily waters. (Abstract shortened by UMI.)
Baked products with various expanded structures were obtained by changes in process conditions and formulation. A device was set up to measure their gas permeability coefficient, k (from 10⁻¹² to ...3.6.10⁻¹⁰ m²) and then relate it to their structural features. The device consists of an hermetic cell connected to gas flow rate sensor and allows for modification of the sample density through compression. For a laminar air flow, k is determined by the measurement of the differential pressure, according to Darcy's law. Gas permeability on uncompressed and in situ compressed crumbs, with apparent density ρ* varying from 0.20 to 0.50 g/cm³, were found to depend on their porosity ε following the Carman-Kozeny's model. However, the deviation from theoretical values can not be explained by a simple model based on the tortuosity. Results highlighted the role of the expanded structure, mainly pore size and shape. This device may be used to measure these important properties that influence mass transfer in aerated foods and complement the characterization of their structure.
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