Browsing by Subject "Geological carbon sequestration"
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Item Effects of surface mineralogy and roughness on CO2 wettability of the Mount Simon sandstone; implications for predicting CO2 storage capacity and pore scale transport(2016-05) Botto, Julien; Werth, Charles; Liljestrand, HowardWettability is a key reservoir characteristic influencing geological carbon sequestration (GCS) processes such as CO2 transport and storage capacity. Wettability is often determined on limited number of reservoir samples by measuring the contact angle at the CO2/brine/mineral interface, but the ability to predict this value has not been explored. In this work, minerals comprising a natural reservoir sample were identified, and the influence of their surface roughness, surface charge, and location in the sample on contact angle was quantified to evaluate controlling mechanisms and predictive models. A core sample was obtained from Mount Simon formation, a representative siliciclastic reservoir that is the site of Department of Energy CO2 injection project. Quartz, microcline, illite, hematite, illite + hematite were identified as dominant minerals in the core, and contact angle (θ) measurements were conducted over a wide range of pressure (290-3625 psi) at 40⁰C. At supercritical conditions, individual minerals and the Mount Simon sample were strongly water wet, with contact angles between 27⁰ and 45⁰ and contact angle generally increased with surface roughness, suggesting that brine is trapped in roughness pits between CO2 and the substrate. There was no relationship between contact angle and surface charge. A thin section of the Mount Simon sandstone was examined with a compound light microscope, and reddish precipitates coating quartz and feldspar grains were apparent. These were evaluated with environmental scanning electron microscopy (ESEM) and energy dispersive X-ray spectroscopy (EDS). ESEM images show precipitate morphology that is consistent with clay coatings. The EDS results identify regions of the precipitate with high iron content. Several predictive models for contact angle were evaluated, including the Wenzel, and Cassie-Baxter models, plus new modifications of these that account for alternative surface roughness geometries and/or the fraction of different minerals comprising the reservoir sample surface. Modeling results suggest the fraction of illite/hematite covering Mount Simon grain surfaces is the most important reservoir characteristics that control wettability. To our knowledge, this is the first study that provides mechanistic insights into the characteristics of individual minerals affecting the wettability of a natural reservoir sample.Item Reservoir simulation studies for coupled CO₂ sequestration and enhanced oil recovery(2008-05) Ghomian, Yousef, 1974-; Pope, Gary A.; Sepehrnoori, Kamy, 1951-Compositional reservoir simulation studies were performed to investigate the effect of uncertain reservoir parameters, flood design variables, and economic factors on coupled CO₂ sequestration and EOR projects. Typical sandstone and carbonate reservoir properties were used to build generic reservoir models. A large number of simulations were needed to quantify the impact of all these factors and their corresponding uncertainties taking into account various combinations of the factors. The design of experiment method along with response surface methodology and Monte-Carlo simulations were utilized to maximize the information gained from each uncertainty analysis. The two objective functions were project profit in the form of $/bbl of oil produced and sequestered amount of CO₂ in the reservoir. The optimized values for all objective functions predicted by design of experiment and the response surface method were found to be close to the values obtained by the simulation study, but with only a small fraction of the computational time. After the statistical analysis of the simulation results, the most to least influential factors for maximizing both profit and amount of stored CO₂ are the produced gas oil ratio constraint, production and injection well types, and well spacing. For WAG injection scenarios, the Dykstra-Parsons coefficient and combinations of WAG ratio and slug size are important parameters. Also for a CO₂ flood, no significant reduction of profit occurred when only the storage of CO₂ was maximized. In terms of the economic parameters, it was demonstrated that the oil price dominates the CO₂ EOR and storage. This study showed that sandstone reservoirs have higher probability of need for CO₂i ncentives. In addition, higher CO₂ credit is needed for WAG injection scenarios than continuous CO₂ injection. As the second part of this study, scaling groups for miscible CO₂ flooding in a three-dimensional oil reservoir were derived using inspectional analysis with special emphasis on the equations related to phase behavior. Some of these scaling groups were used to develop a new MMP correlation. This correlation was compared with published correlations using a wide range of reservoir fluids and found to give more accurate predictions of the MMP.