Browsing by Subject "Porosity"
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Item Compressibility and permeability of Gulf of Mexico mudrocks, resedimented and in-situ(2014-05) Betts, William Salter; Flemings, Peter Barry, 1960-Uniaxial consolidation tests of resedimented mudrocks from the offshore Gulf of Mexico reveal compression and permeability behavior that is in many ways similar to those of intact core specimens and field measurements. Porosity (n) of the resedimented mudrock also falls between field porosity estimates obtained from sonic and bulk density well logs at comparable effective stresses. Laboratory-prepared mudrocks are used as testing analogs because accurate in-situ measurements and intact cores are difficult to obtain. However, few direct comparisons between laboratory-prepared mudrocks, field behavior, and intact core behavior have been made. In this thesis, I compare permeability and compressibility of laboratory-prepared specimens from Gulf of Mexico material to intact core and field analysis of this material. I resediment high plasticity silty claystone obtained from Plio-Pleistocene-aged mudrocks in the Eugene Island Block 330 oilfield, offshore Louisiana, and characterize its compression and permeability behavior through constant rate of strain consolidation tests. The resedimented mudrocks decrease in void ratio (e) from 1.4 (61% porosity) at 100 kPa of effective stress to 0.34 (26% porosity) at 20.4 MPa. I model the compression behavior using a power function between specific volume (v=1+e) and effective stress ([sigma]'v): v=1.85[sigma]'v-⁰̇¹⁰⁸. Vertical permeability (k) decreases from 2.5·10-¹⁶ m² to 4.5·10-²⁰ m² over this range, and I model the permeability as a log-linear function of porosity (n): log₁₀ k=10.83n - 23.21. Field porosity estimates are calculated from well logs using two approaches; an empirical correlation based on sonic velocities, and a calculation using the bulk density. Porosity of the resedimented mudrock falls above the sonic-derived porosity and below the density porosity at all effective stresses. Measurements on intact core specimens display similar compression and permeability behavior to the resedimented specimens. Similar compression behavior is also observed in Ursa Basin mudrocks. Based on these similarities, resedimented Gulf of Mexico mudrock is a reasonable analog for field behavior.Item Dependence of transport properties on grain size distribution(2016-12) Tripp, Brandon Jamal; Daigle, HughThe topic of this thesis is investigating the relationship between grain size distribution and absolute permeability for medium silt to very fine-grained sandstones that are typical reservoir rocks in deepwater, offshore environments. I analyzed the relationship between grain size, mean grain size, median grain size, and grain size mode; grain size standard deviation; and absolute permeability through the amalgamation of numerical modeling and experimental core data for marine clay from the Pacific Ocean and Gulf of Alaska. The Pacific Ocean core sample was selected to represent porous media exhibiting narrow grain size distributions; the Gulf of Alaska samples were selected to represent porous media exhibiting broad grain size distributions. I constructed porous media composed of random packings of spheres with grain size distributions modeled on the grain size distribution of the Pacific Ocean core, and determined permeability by performing Lattice-Boltzmann simulations. The narrow grain size distributions exhibited a power law relationship between grain size standard deviation and permeability relationship. I then compared these results to measured data on the Gulf of Alaska samples, which exhibited very broad grain size distributions. The Gulf of Alaska samples had a different relationship between permeability and the standard deviation of the grain size distribution, although the relationship was still a power law. This illustrates how the breadth of the grain size distribution must be considered in empirical permeability relationships.Item Deposition and diagenesis of San Andres cores 16-69 and 20-69(Texas Tech University, 1982-05) Jarvi, Thomas RobertNot availableItem Deposition, diagenesis and porosity relationships of the Mississippian Chappel limestone, Shackelford County, Texas(Texas Tech University, 1978-12) Washburn, Judith Rena HintonNot availableItem Deposition, Diagenesis, and Porosity Relationships of the Lower San Andres Formation, Quay and Roosevelt Counties, New Mexico(Texas Tech University, 1979-05) Worthen, John AldrichNot Available.Item Depositional environments and diagenesis of the San Andres Formation in Howard-Glasscock Field, Howard County, Texas(Texas Tech University, 1986-12) Chen, JinxingNot availableItem Diagenesis and Porosity Relationships of Lower San Andres Formation, Quay and Roosevelt counties, New Mexico(Texas Tech University, 1978-12) Foley, Donald CharlesNot Available.Item Effect of rough fractal pore-solid interface on single-phase permeability in random fractal porous media(2016-08) Cousins, Timothy Alexander; Daigle, Hugh; Prodanović, MašaSingle-phase permeability k has intensively been investigated over the past several decades by means of experiments, theories and simulations. Although the effect of surface roughness on fluid flow and permeability in single pores and fractures as well as in a network of fractures was studied previously, its influence on permeability in a random mass fractal porous medium constructed of pores of different sizes remained as an open question. A fractal medium is one whose pore space and solid matrix can be characterized by statistical self-similarity and described by a fractal dimension Dm. Specifically, in a random mass fractal, each iteration of construction of the medium is composed of identical-size particles and pores of different sizes that are distributed randomly within (Hunt et al. 2014). This thesis contains the research into the effect of rough pore-solid interface on single-phase flow and permeability in fractal porous media. Using fractal geometry, randomly generated three-dimensional Menger sponges were created to model porous media with a range of mass fractal dimensionalities Dm between 2.579 and 2.893. This dimensionality characterizes both the solid matrix and the pore space of the media. The pore-solid interface of the media is subsequently roughened using the Weierstrass-Mandelbrot approach and controlled primarily by the surface fractal dimension Ds and root-mean-square of roughness height σ. The permeability was calculated for all the roughened media using the lattice-Boltzmann method using D3Q19 geometry and Bhatnagar-Gross-Krook (BGK) collision model. The LBM simulations calculated the single-phase permeability based on Darcy’s Law. Results indicate that permeability decreases sharply with increasing Ds from 1 to 1.1 regardless of Dm value, and remains relatively constant as Ds increases from 1.1 to 1.6. Furthermore, while creating the media, a lower bound for the percolation threshold appeared to be around 29.8% for randomized Menger sponges. When fitted to the percolation model presented in Larson et al. (1981) with an upper limit of 0.36 from Kim et al. (2011), the parameters from a least squares fit point to a critical porosity ϕc of 30% and a percolation exponent t between 3.1 and 3.3. Future research should investigate the effect of the percolation threshold for these simulated porous media and the effect surface roughness would have on this threshold. Finally, future research should expand into two-phase flow and investigate the effects of surface roughness on relative permeability and capillary pressure in simulated fractal porous media.Item Electrochemical deposition of metal ions in porous laser sintered inter-metallic and ceramic preforms(2010-12) Goel, Abhishek, 1986-; Bourell, David Lee; Beaman Jr., Joseph J.Selective laser sintering (SLS) is a commercial, powder-based manufacturing process that produces parts with complicated shape and geometry based on a computer solid model. One of the major drawbacks of SLSed inter-metallic and ceramic parts is their high porosity because of the use of binder system. High porosity results in poor mechanical, electrical and thermal properties of the preform and hence renders it unsuitable for various applications. This thesis attempts to infiltrate SLSed preforms by carrying out electrochemical deposition of metal ions inside the interconnected pore network. One of the major benefits of carrying out this novel process is low processing temperature as opposed to existing methods such as melt infiltration. Low temperature reduces both energy consumption and associated carbon-footprint and also minimizes undesirable structural changes. Both conductive and non-conductive preforms may be electrochemically infiltrated, and MMCs produced by this method have potential for use in structural applications.Item Environments of deposition and diagenesis of the Upper Clear Fork Group, Yoakum County, Texas(Texas Tech University, 1987-08) Moore, Brian KeithThis project provides an Interpretation of the depositional environments, diagenesls, and resultant porosity relationships within the upper Clear Pork of Yoakum County, Texas. Of primary interest to this investigation Is the description of a small bryozoanalgal patch reef located at the base of the studied section. A discussion of the paleoecology, lateral variations, and community succession of the buildup also is given.Item Fracturing and fracture reorientation in unconsolidated sands and sandstones(2006) Zhai, Zongyu; Sharma, Mukul M.Item Genetic pore typing as a means of characterizing reservoir flow units: san andres, sunflower field, terry country, texas(2009-05-15) Humbolt, Aubrey NicoleCarbonate reservoirs are characteristically heterogeneous in reservoir quality and performance owing to the variety of processes that influence pore formation. Additionally, porosity and permeability do not conform to depositional facies boundaries in carbonate reservoirs affected by diagenesis or fracturing; consequently, conventional methods of petrophysical characterization of flow units based on depositional facies are unreliable as predictors of reservoir behavior. We provide an integrated stratigraphic, petrographic, and petrophysical study of the San Andres reservoir at Sunflower field that identifies and quality-ranks flow units on the basis of genetic pore types. A total of 12 full-diameter cores were analyzed revealing three primary depositional facies and cyclical patterns of deposition identified as parasequences. From the cores, 73 samples were chosen for thin sections. Through petrographic analysis, pores were classified using the Ahr 2005 method and four distinct, genetic pore types were identified. Petrophysical rock types were established by identifying which genetic pore types correspond to high poroperm values, and where they occur within the stratigraphic framework of the reservoir. Sixteen coherent plugs were also subjected to mercury injection capillary pressure analysis in order to quantify pore ? pore throat relationships. The data were then evaluated by facies, porosity type, and cycle position using graphical methods, such as k/phi, Winland R35, and Lorenz plots. The results of this study reveal that the most effective way of characterizing petrophysical flow units is the combination of k/phi ratio analyses and genetic pore typing.Item Hydraulic conductivity measurement of permeable friction course (PFC) experiencing two-dimensional nonlinear flow effects(2010-05) Klenzendorf, Joshua Brandon; Charbeneau, Randall J.; Barrett, Michael E.; Maidment, David R.; McKinney, Daene C.; Sepehrnoori, Kamy; Sharp, Jr., John M.Permeable Friction Course (PFC) is a layer of porous asphalt pavement with a thickness of up to 50 millimeters overlain on a conventional impervious hot mix asphalt or Portland cement concrete roadway surface. PFC is used for its driver safety and improved stormwater quality benefits associated with its ability to drain rainfall runoff from the roadway surface. PFC has recently been approved as a stormwater best management practice in the State of Texas. The drainage properties of PFC are typically considered to be governed primarily by two hydraulic properties: porosity and hydraulic conductivity. Both of these hydraulic properties are expected to change over the life of the PFC layer due to clogging of the pore space by trapped sediment. Therefore, proper measurement of the hydraulic properties can be problematic. Laboratory and field tests are necessary for accurately determining the hydraulic conductivity of the PFC layer in order to ensure whether the driver safety and water quality benefits will persist in the future. During testing, PFC experiences a nonlinear flow relationship which can be modeled using the Forchheimer equation. Due to the two-dimensional flow patterns created during testing, the hydraulic conductivity cannot be directly measured. Therefore, numerical modeling of the two-dimensional nonlinear flow relationship is required to convert the measureable flow characteristics into the theoretical flow characteristics in order to properly determine the isotropic hydraulic conductivity. This numerical model utilizes a new scalar quantity, defined as the hydraulic conductivity ratio, to allow for proper modeling of nonlinear flow in two-dimensional cylindrical coordinates. PFC core specimens have been extracted from three different roadway locations around Austin, Texas for the past four years (2007 to 2010). Porosity values of the core specimens range from 12% to 23%, and the porosity data suggest a statistical decrease over time due to trapped sediment in the pore space. A series of constant head tests used in the laboratory and a falling head test used in the field are recommended for measurement of PFC hydraulic characteristics using a modified Forchheimer equation. Through numerical modeling, regressions equations are presented to estimate the hydraulic conductivity and nonlinear Forchheimer coefficient from the measureable hydraulic characteristics determined during experimental testing. Hydraulic conductivity values determined for laboratory core specimens range from 0.02 centimeters per second (cm/s) to nearly 3 cm/s. Field measurements of in-situ hydraulic conductivity vary over a range from 0.6 cm/s to 3.6 cm/s. The results of this research provide well-defined laboratory and field methods for measurement of the isotropic hydraulic conductivity of PFC experiencing two-dimensional nonlinear flow and characterized by the Forchheimer equation. This methodology utilizes a numerical model which presents a proper solution for nonlinear flow in two-dimensions.Item Investigation of the pore size and structure in organic-rich shales(2015-05) Ezidiegwu, Sandra Nkechinyere; Daigle, HughPermeability in source rocks allows the flow of reservoir fluids during production and is dependent on the pore size distribution. In organic shales, the level of porosity of organic material (OM) is based on its range of pore sizes. Scanning electron microscope (SEM) images are commonly used to examine OM-hosted pores, but this technique is limited by resolution, which is in the order of ~5 nm. This study seeks to increase this range of pore size distribution (PSD) to ~ 0.38 nm, in organic-rich shales by using low-pressure carbon dioxide (CO₂) adsorption coupled with density functional theory (DFT). In addition, we coupled low-pressure nitrogen (N₂) adsorption with the Barrett-Joyner-Halenda (BJH) and DFT models to quantify pore sizes between ~2 to 170 nm. To characterize the entire range of pore sizes, we used high-pressure mercury intrusion because it is commonly used to quantify larger pores. The samples used in this study include a bulk sample and isolated kerogen of Green River shale (Eocene, Utah), Woodford shale (Upper Devonian, Oklahoma), and Cameo Coal (Cretaceous, Colorado). These samples represent type I, II and III, kerogen, respectively, at similar maturity levels and thus provide a good experimental basis for evaluating the PSD. The methodology consisted of four steps: i) Kerogens were isolated from the bulk samples by demineralization, ii) Samples were divided into sizes of ~ 0.5 grams into test tubes and degassed, iii) Samples were analyzed in the Porosimeter using low-pressure N₂ and CO₂ adsorption techniques, iv) Isotherm data from the adsorption measurement were extracted to create the PSD. Our results showed the presence of pore sizes as small as ~ 0.38 nm, based on combining techniques of N₂ adsorption at 77 K and CO₂ adsorption at 273 K in all three samples. Hence, we have expanded our understanding of the range of pore sizes contained in organic-rich material. In addition, the majority of pores in Green River shale and cameo coal fell below the SEM resolution limit of ~5 nm. Lastly, the kerogen and bulk samples of the Green River and Woodford shales showed a variation in the PSD, with the larger pores in the kerogen, which indicates that kerogen constitutes the majority of the pores in the samples. In conclusion, we developed a novel approach to investigate OM-hosted pore sizes. This approach increased the range of pore sizes from ~ 5 nm to ~ 0.38 nm, thus improving the estimation of flow rates during production in shale and in applicable reservoirs.Item Lithofacies, Porosity and Log Response of the Lower San Andres Formation in the Palo Duro Basin(Texas Tech University, 1983-05) Rahman, Ata UrThe lower San Andres Formation of Curry, DeBaca, Quay and Roosevelt counties, New Mexico, was deposited in the Tucumacari - Palo Duro Basin which was a swale on the Northwestern Shelf of the Permian Basin. Unlike other areas of the Permian Basin where San Andres forms prolific hydrocarbon reservoirs, in the study area it is devoid of hydrocarbons. The study of lithofacies distribution and associated depositional environments, porosity and permeability trends and geophysical log response could serve as a useful model in analyzing and interpreting other similar lithofacies. The lower San Andres consists of dolostones, limestones, dedolostones, anhydrite, halites and thin shales. Four major progradational depositional cycles are recorded. Upward from the base the cycles generally consist of subtidal and intertidal carbonates, supratidal carbonates, sulfates and halite. The vast bulk of the sulfate was emplaced as replacement of dolostones; thus, the presence of anhydrite within a cycle may have little genetic significance. As compared to carbonates, percentages of anhydrite and halite increase both towards the NW (proximally) and within successively younger cycles of deposition. Dolostones to limestone ratio also increases towards the NW and in younger cycles. Porosity and permeability generally increase towards the SE (distally) and in older cycles of deposition. This reflects’ a general progradation of supratidal environments towards SE (distally). Primary porosities are very rarely preserved. Most of the preserved porosities are secondary, tertiary and quaternary in nature. Secondary intercrystalline porosity is more abundant in distal (SE) areas, while moldic porosity is predominent in proximal (NW) areas. Dolostones generally have much greater porosity than limestones. Most lower San Andres intervals have been subjected to two or more cyclic fluid invasions sequences wherein dolomitizing, anhydritizing and low salinity fluids have successively registered their overprints. Dolomite, anhydrite and calcite cements formed during multiple cyclic diagenesis are the prominant porosity occluders. Generally most of the lithofacies can be differentiated on the basis of the log response; however, cross plots of various log values aid in differentiating the lithofacies more explicitly.Item Measurement and modeling of multiscale flow and transport through large-vug Cretaceous carbonates(2008-08) Nair, Narayan Gopinathan, 1980-; Bryant, Steven L.; Jennings, James W.Many of the world's oil fields and aquifers are found in carbonate strata. Some of these formations contain vugs or cavities several centimeters in size. Flow of fluids through such rocks depends strongly upon the spatial distribution and connectivity of the vugs. Enhanced oil recovery processes such as enriched gas drives and groundwater remediation efforts like soil venting operations depend on the amount of hydrodynamic dispersion of such rocks. Selecting a representative scale to measure permeability and dispersivity in such rocks can be crucial because the connected vug lengths can be longer than typical core diameters. Large touching vug (centimeter-scale), Cretaceous carbonate rocks from an exposed rudist (caprinid) reef buildup at the Pipe Creek Outcrop in Central Texas were studied at three different scales. Single-phase airflow and gas-tracer experiments were conducted on 2.5 in. diameter by 5 in. long cores (core-scale) and 5- to 10-ft-radius well tests (field-scale). Zhang et al. (2005) studied a 10 in. diameter by 14 in. high sample (bench-scale). Vertical permeability in the bench-scale varied from 100 darcies to 10 md and in the core-scale averaged 2.5 darcies. The field-scale permeability was estimated to be 500 md from steady state airflow and pressure transient tests. In the bench and core scales a connected path of vugs dominates flow and tracer concentration breakthrough profile. Tracer transport showed immediate breakthrough times and a long tail in the tracer concentrations characterized by multiple plateaus in concentrations. Neither flow nor tracer transport can be explained at these scales by the standard continuum equations (Darcy’s law or 1D convection dispersion equation). However, interpreting field-scale measurements with standard continuum equations suggested that a strongly connected path of vugs did not extend past a few feet. In particular, the tracer experiment in the field scale can be modeled accurately using an equivalent homogeneous porous medium with a dispersivity of 0.5 ft. In our measurements, permeability decreased with scale, while vug connectivity and multi-scale effects associated with vug connectivity decreased with increasing scale. We concluded that approximately 5 ft could be considered the representative scale for the large-touching-vug carbonate rocks at the Pipe Creek Outcrop. The major contribution of this research is the introduction of an integrated, multi-scale, experimental approach to understanding fluid flow in carbonate rocks with interconnected networks of vugs too large to be adequately characterized in core samples alone.Item Modeling nanoporosity development in thin film polymers for low-k (dielectric) applications(Texas Tech University, 2002-05) Doshi, PrathameshThe bubble growth dynamics subsequent to nucleation resulting from supersaturation of a polymer-dissolved gas system have been modeled. The model components include mass and momentum balance partial differential equations along with appropriate initial and boundary conditions. In addition the model equations also include thermodynamic equilibrium criteria along with equations of state, evolution of transport properties with concentration of dissolved gas and temperature, mechanical constitutive equations for polymer-dissolved gas/saturated gas phase. The model equations are based on the shell model of Arefmanesh et al. which envisages a concentric shell of polymer-dissolved gas surrounding every bubble nucleated. Bubble grows by diffusion of dissolved gas from this shell. The above model was modified to allow for diffusion of dissolved gas out of the shell in addition to diffusion into the bubble. The model equations are then solved using a finite difference approach. The results are presented for various growth conditions obtained by varying key variables in a parametric study. Detailed model equations include the Fox equation to model the reduction in the glass transition temperature, Tg, of the polymer upon plasticization. This change in the Tg affects material properties like viscosity (77), characteristic relaxation time(/l) and diffusivity (D) due to the softening effect. These material properties are temperature and dissolved gas concentration dependent and are modeled on the principles of time-temperature and time-concentration superposition. The shift factors have a Williams-Landell-Ferry (WLF) type dependence. A single element Maxwell fluid is used defme the polymer constitutive equation and diffusion is assumed to be Fickian, but with a nonconstant diffusivity. Equilibrium at the gas bubble and polymer shell interface is assumed to be defmed by Henry's law and the gas in the bubble is assumed to be ideal. A parametric analysis by varying film thickness ((^Q ) > temperature (T), diffusivity at the Tg DQ) and Henry's law constant ( ) is done, to investigate the effects of these variables on bubble growth dynamics.Item Nuclear magnetic resonance imaging and analysis for determination of porous media properties(Texas A&M University, 2007-04-25) Uh, JinsooAdvanced nuclear magnetic resonance (NMR) imaging methodologies have been developed to determine porous media properties associated with fluid flow processes. This dissertation presents the development of NMR experimental and analysis methodologies, called NMR probes, particularly for determination of porosity, permeability, and pore-size distributions of porous media while the developed methodologies can be used for other properties. The NMR relaxation distribution can provide various information about porous systems having NMR active nuclei. The determination of the distribution from NMR relaxation data is an ill-posed inverse problem that requires special care, but conventionally the problem has been solved by ad-hoc methods. We have developed a new method based on sound statistical theory that suitably implements smoothness and equality/inequality constraints. This method is used for determination of porosity distributions. A Carr-Purcell-Meiboom-Gill (CPMG) NMR experiment is designed to measure spatially resolved NMR relaxation data. The determined relaxation distribution provides the estimate of intrinsic magnetization which, in turn, is scaled to porosity. A pulsed-field-gradient stimulated-echo (PFGSTE) NMR velocity imaging experiment is designed to measure the superficial average velocity at each volume element. This experiment measures velocity number distributions as opposed to the average phase shift, which is conventionally measured, to suitably quantify the velocities within heterogeneous porous media. The permeability distributions are determined by solving the inverse problem formulated in terms of flow models and the velocity data. We present new experimental designs associated with flow conditions to enhance the accuracy of the estimates. Efforts have been put forth to further improve the accuracy by introducing and evaluating global optimization methods. The NMR relaxation distribution can be scaled to a pore-size distribution once the surface relaxivity is known. We have developed a new method, which avoids limitations on the range of time for which data may be used, to determine surface relaxivity by the PFGSTE NMR diffusion experiment.Item The origin and properties of mass transport deposits, Ursa Basin, Gulf of Mexico(2009-12) Strong, Hilary Elizabeth; Flemings, Peter Barry, 1960-; Day-Stirrat, Ruarri; Mohrig, DavidUniaxial consolidation experiments on Mass Transport Deposit (MTD) and non-MTD core samples from Ursa Basin, Gulf of Mexico, show MTDs have a lower porosity at a given effective stress compared to adjacent non-MTD sediments; a behavior observed in additional experiments on lab remolded Ursa core and resedimented Boston Blue Clay (BBC). I hypothesize debris flow action remolded the sediment: removing its stress history through shearing action, resulting in dense sediments at shallow depth. I supplement testing this hypothesis through lab remolding of BBC (in addition to Ursa clay) due to the greater availability and knowledge of this material. Ursa MTDs record multiple submarine slope failure events within the upper 200 meters below sea floor (mbsf); the most prominent is labeled MTD-2. MTDs have lower porosity and higher bulk density than surrounding, non-MTD, sediment. Porosity ([phi]) is 52% at 125mbsf – immediately below MTD-2; whereas [phi] is 46% at 115mbsf – within MTD-2. Comparison of non-MTD samples to MTD-2 samples, and intact to remolded samples, shows a decrease in sediment compressibility (Cc) within the MTD-2 and remolded sediments. Permeability within Ursa mudstones also declines with porosity according to: log (k) = A[phi] - B. Permeability is slightly higher within MTD-2; however grain size analysis indicates lower clay content in MTD-2 versus the non-MTDs. Pre-consolidation stress interpretations from the experiments show a linear trend in both MTD and non-MTD sediments, indicating both geologic units depict the same pore pressure profile. Remolding via debris flow explains the origin of MTDs at Ursa and governs the evolution of this geologic unit to its dense, highly consolidated, state today. At some point, slope failure triggered movement of the sediment down slope in form of a debris flow. The shearing action of the debris flow weakened the sediment, reducing its ability to support the overburden. As consolidation resumed, the remolded sediment followed a new, less steep, Cc curve. Within the geologic record, a distinctive dense, shallow unit is preserved; evidence for historical slope failure.Item Pore-scale petrophysical models for the simulation and combined interpretation of nuclear magnetic resonance and wide-band electromagnetic measurements of saturated rocks(2006) Toumelin, Emmanuel; Torres-Verdín, Carlos