Reservoir wettability is controlled by crude oil/brine/rock interactions that have not been well understood. Studies using either model compounds or crude oil fractions have had only limited success in reproducing the wetting alteration that can occur in nature. In this study, the approach is first to identify the key features of interfacial activity unique to crude oils, then to design and conduct wetting alteration experiments—using both flat solids and porous media—that demonstrate the mechanisms by which alteration can occur. Components of crude oils that are interfacially active are found in the highest molecular weight, most polar fractions of the oil, the resins and asphaltenes. How these components affect wetting depends on the compositions of not only the oil, but also the mineral surfaces and the aqueous phase that is always present in oil reservoirs. Wettability altering interactions can occur by several mechanisms. In the absence of water, adsorption of polar species can create intermediately-wet surfaces. If the oil is a poor solvent for its asphaltene fraction, adsorption of large asphaltene aggregates can make surfaces fairly oil-wet. Adsorption can also occur because of ionic interactions between oppositely charged acidic and basic sites at the oil/water and solid/water interfaces. There may also be interactions between similarly charged sites, if ion binding can occur. All of these mechanisms have been documented for a range of crude oils with varying asphaltene fraction, solvency, acid number, and base number.

No description available.

No description available.

Thesis (Ph.D.)--University of Tulsa. / Bibliography: leaves 373-384.

No description available.

No description available.

Operators can improve a reservoir’s value by optimizing it in a more holistic manner, or over its entire life cycle. This thesis developed approaches to life cycle optimization, with emphasis on accessible technical and economic modeling techniques for production. The challenges of life cycle optimization are properly scheduling the times at which the operator should switch from one recovery phase to the next, along with determining other field design parameters such as well spacing and injection pressures for waterflooding and enhanced oil recovery processes. To deliver the most value, the operator needs to produce from a reservoir the greatest quantity of oil, at a relatively low cost, reasonably soon, and ideally at a time when the oil price is high. This is quite a tall order, as these goals are often in conflict. This thesis extended existing research regarding lifecycle optimization, first modeling production from a reservoir using an exponential decline model and assuming the oil price’s behavior can be approximated with mean-reverting processes. Implications of operating and capital costs potentially being correlated with the oil price were also examined. Finally, a mean-reverting price model that forecasts the mean oil price as increasing and described by a logistic model was proposed to accommodate both recent price forecasts and economic reality. As exponential decline models are more appropriate for characterizing existing production history rather than making a priori predictions, a geologic-parameter-based model was developed using a tank model for primary recovery and a model based on Koval theory and parameterizing a reservoir in terms of flow capacity and storage capacity for waterflooding and CO2 flooding. This model was adapted from existing theory to account for situations where a waterflood has incompletely swept a reservoir at the start of CO2 flooding. Analytical expressions were also derived for estimating injection rates into a formation parameterized by flow capacity and storage capacity. The geologic-parameter-based model was combined with economic assumptions and optimized using a genetic algorithm. This optimization suggested an operator should switch from primary recovery to a CO2 flood with a large WAG ratio relatively early in the reservoir’s life. / text

Thesis (Ph. D.)--University of Texas at Austin, 2008. / Vita. Includes bibliographical references.

No description available.

Due to capillary pressure, reservoir heterogeneity, oil mobility, and lack of reservoir energy, typically more than 50 % of the original oil in place is left in the reservoir after primary and secondary recovery oil production. With relatively easy-to-get conventional oil resources diminishing and the price of oil hovering around triple digits, enhanced oil recovery methods, such as polymer flooding, have become very attractive ways to recover oil effectively from existing reservoirs. Enhanced oil recovery methods can be categorized into three categories: water or chemical based, gas based, and thermal based. This thesis will focus on the chemical injection of surfactants, alkali, and polymer of the water based methods. Surfactants are used to alter the interfacial tension of the aqueous and oleic phases in order to facility oil production. Alkali chemicals are used to create surfactants by reacting with acidic oil. And polymer is used to reduce injection water mobility to effectively displace the contacted oil in heterogeneous reservoirs by improving the volumetric and displacement sweep efficiencies. This research presents several laboratory results of polymer and alkali/surfactant/polymer core floods performed in the Center for Petroleum and Geosystems Engineering laboratories. Properties of polymer and surfactant phase behavior were measured and modeled and each coreflood was history matched with UTCHEM, a three-dimensional chemical flooding simulator. The coreflood results and the history matched model parameters were then upscaled to a pilot case for viscous oil in offshore environment with four wells in a line drive pattern. The potential of polymer flooding was investigated and several sensitivity cases were performed to evaluate the effect of various physical property parameters on oil recovery. Water salinity and hardness (i.e. amount of calcium and magnesium) has detrimental effects on polymer viscosity and its stability. The potential benefits of low salinity water injection by desalinization of seawater for polymer flood projects have been discussed in recent publications. The effect of low salinity polymer flood was also investigated. A series of sensitivity studies on well pattern and well spacing is carried out to investigate the impact on recovery factor and recovery time. / text