Browsing by Subject "Dolomite"
Now showing 1 - 9 of 9
Results Per Page
Sort Options
Item A Comparative Study of Dolomite Dissolution in Simple Organic Acids and Chelating Agents(2013-05-03) Adenuga, Olusegun OAcid treatments have predominantly been conducted using HCl for its availability, high rock dissolving power and soluble reaction products. At high temperatures, rapid spending of the acid with carbonates prevents deeper penetration distance into the formations. Alternative fluids such as acetic and formic acid have lent themselves to retarded reaction rates, low corrosivity and reduced tendency to form acid/oil sludge in asphaltene-rich crudes but for high reaction rate problems. Chelating agents, with the added advantage of complexing with alkali-earth metals in carbonates to form water-soluble products that are thermally stable at high temperature, have been introduced as stimulation fluids. Glutamic acid diacetic acid (GLDA) ethylenediaminetetraacetic acid (EDTA) and hydroxyethylenediaminetriacetic acid (HEDTA) are aminopolycarboxylic acids that were studied. To predict the spending of chelating agents relative to simple organic acids at temperatures between 150 and 250?F, the chemical kinetics of dolomite dissolution in these acid solutions were investigated over different reaction conditions in a rotating disk apparatus. Samples of the reacted acids from the reactor were collected and then analyzed with inductively coupled plasma (ICP). Analyses of the experimental data were carried out to determine kinetic parameters of the heterogeneous reactions needed for matrix stimulation of dolomitic reservoirs. Experimental results indicated that dolomite dissolution rates increased in all the acid solutions as the disk rotational speeds increased at 150, 200, and 250?F. The dissolution of dolomite in 0.886 M GLDA was found to be surface-reaction limited at lower temperatures and mass-transfer limited at highest temperature. GLDA with the lowest reaction rates and relative diffusion coefficient demonstrated retardation before spending with deeper penetration capability for productivity and injectivity improvement.Item A study of lacustrine dolomite and associated sediments of Lake Mound, Lynn and Terry counties, Texas(Texas Tech University, 1969-05) Leach, Jerald WayneThe purpose of this study was to collect geological and geochemical data which would aid in describing conditions surrounding the formation of penecontemporaneous dolomite in Lake Moxind. The advantage gained in studying this particular dolomite is that it has not been subjected to processes of extensive diagenesis and offers a model for examining some of the environmental conditions similar to those that existed during the time of dolomite formation. Studies of penecontemporaneous dolomite provide the best information available regarding conditions surrounding the formation of dolomite. When sufficient data become available, it should be possible to isolate conditions essential to the process, to reproduce these in the laboratory, and to synthesize dolomite under conditions which could exist in a natural sedimentary environment.Item 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 Integrated stratigraphy and petrology of the Silurian Wink formation (Wenlock-Ludlow) Howard County, Texas(Texas Tech University, 2004-05) Kohl, Michael LThe Cobra-Frazier #1 well in Howard County penetrated the Silurian Wristen Group and Fusselman Formation, and a core with sixty feet of strata was recovered, the majority of which belongs to the Wink Formation of the Wristen Group. Petrologic, petrographic, and geochemical studies allow interpretation of the depositional and diagenetic history of the Wink Formation in the eastern margin of the Permian Basin region. The Wink of the Cobra-Frazier #1 consists of argillaceous skeletal wackestones and mudstones that are dominated by a deep water fauna dominated by arthropods. Conodont faunas indicate that the age of the Wink ranges from the early Sheinwoodian (Wenlock), into the Gorstian (Ludlow) and perhaps as young as the early Ludfordian. The Wink Formation was deposited when the exposed Fusselman platform was flooded in the early Sheinwoodian. Deposition continued in a carbonate ramp setting until differential subsidence produced the platform and basin fades of the Fasken and Frame formations. During the hiatus that separated the Thirtyone Formation from the Woodford Formation, the Wink was karsted, evidenced by the presence of crackle, mosaic, and chaotic breccia fabrics related to paleocave formation and collapse. The karst-related porosity was subsequently filled by fine-grained argillaceous carbonate sediments. After the karsting event, the Wink strata underwent to three dolomitization events, two diagenetic, and one epithermal event related to the Ouachita Orogeny. The two diagenetic dolomitization events did not affect the entire Wink equally, with increased dolomitization in the lower portion of the core. In the lower Wink, this created a dolostone with intercrystalline, vuggy, and fracture porosity. Subsequent precipitation of baroque dolomite, from the epithermal event, and calcite cements destroyed much of the porosity throughout the core. Analysis of carbon and oxygen stable isotopes produced curves that were used to test models of oceanic and environmental cyclicity. When compared to oceanic and environmental models, the data was inconclusive, neither clearly supporting nor refuting any of the models. Two positive excursions associated with the Mulde Event and near the Wenlock-Ludlow Boundary are present in both the carbon and oxygen curves. These excursions have carbon §-values increased by slightly more than l%o, and the oxygen 5-values increases of more than 2%o. The excursions allow correlations between the Wink and strata in Oklahoma, Nevada, and across many parts of Europe, particularly the Baltic region.Item Outcrop-constrained flow and transport models of reflux dolomitization(2009-12) Garcia-Fresca, Beatriz, 1973-; Lucia, F. Jerry; Sharp, John Malcolm, Jr., 1944-Two hydrogeologic models explore reflux dolomitization using two outcrop datasets at different scales to constrain transient boundary conditions and heterogeneous petrophysical properties. A platform-scale petrophysical model of the Permian San Andres Formation was built from outcrop and subsurface data following a reservoir modeling approach that preserves outcrop heterogeneity and incorporates a sequence stratigraphic framework. This model was used as input for hydrogeological simulations of hypersaline fluid flow and solute transport during the accumulation and compaction of the platform. Boundary conditions change over time, as relative sealevel fluctuations drive sedimentation, depositional environment migration, topographic gradients, and location, size and salinity of the brine source. The potential volume and distribution of dolomite formed is inferred by a magnesium mass-balance. The composite result of reflux events at various orders of stratigraphic hierarchy is a complex dolomite pattern that resembles that observed on San Andres outcrops. Dolostone bodies across the platform may be generated by different combinations of favorable conditions, including proximity to the brine source, zones of higher permeability, permeability contrasts, and latent reflux. A meter-scale reactive transport model of the Albian Upper Glen Rose Formation simulates deposition of three high-frequency cycles punctuated by three brine reflux events. The simulator determines flow, solute and reactive transport along the flow paths, revealing the spatial and temporal distribution of calcite dissolution, and precipitation of dolomite and sulfate. The model recreates fully and partially dolomitized cycles within the time and lithological constrains on Glen Rose outcrops. Our results show that the distribution of dolomite within a high-frequency cycle may be the net result of intercycle processes, whereby dolomitizing fluids sourced from younger cycles flow across stratigraphically significant boundaries. We also show that variations in dolomite abundance and the unfulfilled dolomitization potential control the contemporaneous propagation of multiple dolomite fronts and the coalescence of discrete dolomite bodies. Results show that reflux is an effective and efficient mechanism to dolomitize carbonate formations that progresses simultaneously with sediment accumulation. Dolomitization is the cumulative result of many short-lived reflux events, sourced in different locations and times, and amalgamation of successive dolostone bodies. This model contrasts with previous studies that approached dolomitization of a carbonate platform as a discrete reflux event and current interpretations that relate dolomite bodies to their most immediate stratigraphic surfaces.Item Petrographic and geochemical analysis of Middle Permian dolomites: a comparison of subsurface and outcrop data.(Texas Tech University, 1973-12) Ashour, Abdurrahim M.Not availableItem Stimulation of Carbonate Reservoirs Using a New Emulsified Acid System(2013-05-15) Sayed, Mohammed Ali IbrahimThe scope of work can be divided into; the measurement of the rheological properties of a new emulsified acid system that can be suitable for high temperature applications, a study of the performance of the new emulsified acid in stimulating both calcite and dolomite formations, measuring the reaction rate and diffusion coefficient when the new emulsified acid systems react with both calcite and dolomite, and testing the new emulsified acid using core samples obtained from carbonate reservoirs. The droplet size has a practical impact on the performance of emulsified acid. A good understanding and characterization of the emulsified acid by its size distribution will lead to better understanding of its stability, rheology and how it reacts with carbonate rocks. The influence of the concentration of the new emulsifier on the droplet size, droplet size distribution and upon the rheology of emulsified acids is studied in detail. The emulsified acid reaction kinetics with calcite rocks was studied before in few studies, and very little work was done with dolomite. One of the main objectives of the present work is to study in detail the reaction of the emulsified acid with both calcite and dolomite rocks using the rotating disk apparatus. Most of the previous studies on the emulsified acid were done using core samples that were saturated with brine or deionized water. One of the main objectives of the present work is to study in detail the effect of the presence of crude oil in the reservoir rock on the performance of emulsified acids. Lastly, an innovative technique of emulsifying the chelating agents is evaluated for high temperature applications. The rheology of the emulsified chelating agent is measured using an HPHT rheometer. Also, the reaction of the new emulsified chelating agent with calcite is studied using the rotating disk apparatus, and coreflood experiments were performed using chelating agents and calcite core samples.Item Surface energy characterization of reservoir rocks(2011-05) Arsalan, Naveed; Nguyen, Quoc P.; Pope, Gary A.The fundamental forces of adhesion are responsible for the spreading of fluids such as crude oil/brine on the reservoir rock surface. These physico-chemical interactions determine the surface energetics of a reservoir and thus their wetting phenomena. Inverse Gas Chromatography is introduced to characterize the surface energy of carbonates (calcite and dolomite) and sandstones (Ottawa sand and Berea sandstone). The behavior of the polar and non-polar interaction forces was investigated at varying water coverage and at different temperatures. The results indicated that in general as the water coverage increased, the Lifshitz-van der Waals component of surface energy decreased to nearly that of the bulk water, while the acid-base component also showed a decreasing trend. The Lifshitz-van der Waals component of surface energy always decreased with increase in temperature, while the acid-base properties mostly increased with temperature with the exception of calcite.Item Syndepositional fault control on dolomitization of a steep-walled carbonate platform margin, Yates Formation, Rattlesnake Canyon, New Mexico(2014-12) Simon, Rebekah Elizabeth; Kerans, C. (Charles), 1954-; Zahm, Christopher KentSyndepositional deformation features are fundamental components of carbonate platforms both in the subsurface and in seismic-scale field analogs. These deformation features are commonly opening-mode, solution-widened fractures that can evolve into extensional faults, and reactivate frequently through the evolution of the platform. They also have potential to behave as fluid flow conduits from the earliest phases of platform growth through burial and uplift, and can be active during hydrocarbon generation. As such, diagenetic alteration in the margins of these carbonate platforms is often intense, may demonstrate a preferential spatial relationship to the deformation features rather than the depositional fabrics of the strata, and may impact the permeability development of reservoir strata near deformation features. This study focuses on a syndepositional graben known as the Cave Graben fault system in the Yates Formation of Rattlesnake Canyon in the Guadalupe Mountains, and investigates the distribution of dolomite around the faults and associated opening-mode fractures, in an effort to understand the control the Cave Graben faults exert on fluid flow through the platform margins. Two generations of dolomite are identified on the outcrop: a fabric retentive dolomite located in the uppermost facies of the platform, and a fabric destructive dolomite that forms white, chalky haloes around syndepositional deformation features. The first generation of dolomite is dully luminescent and has very small crystal sizes, as well as a low trace element concentration and an ¹⁸O-enriched stable isotopic signature compared to Permian marine carbonate ratios. This dolomite is interpreted to have formed from the penecontemporaneous refluxing of concentrated lagoonal brine, and shows little fault control on its distribution. The second generation of dolomite is brightly luminescent and has much larger crystal sizes, as well as a higher trace element concentration and a slightly ¹⁸O-depleted isotopic signature compared to the first generation of dolomite, though it is still enriched in ¹⁸O compared to Permian marine carbonate. This dolomite is interpreted to have formed in a burial environment due to the transport of concentrated brines from the overlying evaporites through syndepositional deformation features. Overall, this study suggests that, once open, syndepositional deformation features may become the primary fluid conduit through otherwise impermeable strata, and may control the distribution of diagenetic products over a long period of geologic time. It provides valuable insight into the interaction of syndepositional faults and fractures and fluid flow, and may improve understanding of diagenesis in analogous subsurface carbonates reservoir intervals.