Surfactant-Polymer (SP) and Alkaline-Surfactant-Polymer (ASP) floods are tertiary oil recovery processes that mobilize residual oil to waterflood. These Chemical EOR processes are most valuable when the residual oil saturation of a target reservoir to waterflood is high. The first steps of designing a SP or ASP flood are performed in a laboratory by developing a surfactant formulation and by performing core flood experiments to assess the performance of the flood to recovery residual oil to waterflood. The two criteria for a technically successful laboratory SP or ASP core flood are recovering greater than 90% of residual oil to waterflood leaving behind less than 5% of residual oil and accomplishing this at a field scalable pressure gradient across the porous medium of approximately 1 psi per foot. This thesis documents the laboratory development of SP and ASP core floods for a continental Unites States oil reservoir reported to contain the minerals anhydrite and gypsum. The significance of these minerals is that they provide an infinite acting source of calcium within the reservoir that makes using the traditional alkali sodium carbonate unfeasible using conventional Chemical EOR methods. This is because sodium carbonate will precipitate as calcite in the presence of free calcium ions. Secondly, this thesis investigates two novel alkalis that are compatible with free calcium ions, sodium acetate and tetrasodium EDTA, for their viability for use in ASP floods for reservoirs containing anhydrite or gypsum. / text

There is a vast deposit of viscous and heavy oil, especially in Canada and Venezuela. Typically thermal methods are used to recover heavy oil. However, thermal methods are inefficient when the depth of the reservoir is high and pay thickness is low. Non-thermal methods need to be developed for viscous and heavy oils. Alkaline-surfactant-polymer (ASP) floods can be used for improving the displacement efficiency, but its effect on sweep efficiency in viscous oil recovery has not been studied. The objective of this research was to investigate 2D ASP floods in a quarter five-spot pattern. Through careful phase behavior screening, the surfactant formulation was developed that produced ultra-low interfacial tension with reservoir viscous oil (100 cp). After verifying that the design of surfactant formulation was robust and can recover more than 90% of oil in a 1D ASP sandpack flood, it was tested in a 2D geometry. Both stable and unstable tertiary ASP floods were performed in a 2D quarter five-spot sandpack using the surfactant formulation developed in 1D ASP sandpack flood. In a stable ASP quarter five-spot sandpack flood, the oil recovery was excellent (~97% of ROIP). Oil recovery in the stable 2D ASP flood behaved similar to oil recovery in the 1D stable ASP flood. However, pressure drop obtained was high which would be unsustainable in field applications. Interestingly, unstable 2D flood performed well even with an adverse mobility ratio between oil/water bank and ASP slug with a recovery of 80% ROIP. Decreasing the viscosity of ASP slug 6 times decreased the maximum pressure drop 5 times; thus, the maximum pressure drop was almost proportional to the ASP slug viscosity in a 2D pattern. This research showed that unstable ASP flood in a 2D geometry can recover significant amount of oil with a practical pressure gradient. / text

The application of surfactants and polymers in carbonate reservoirs has a high potential with emerging technology of the manufacture of these chemicals. Tertiary or enhanced oil recovery with chemicals (CEOR) will become more relevant with decreasing new exploration of oil deposits and high remaining oil saturations in huge carbonate oil reservoirs. However, in several oil deposits, high reservoir brine salinity and moderate to high reservoir temperature are encountered. Under such conditions, many chemicals will be insoluble or degrade fast. A selection of commercial and research surfactants and polymers has been investigated for their application under brine salinity of up to 18 percent by weight with significant hardness and a moderate reservoir temperature of 70 °C. Chemical systems were tested towards outcrop limestone rock samples and calcite platelets in combination with a crude oil, which was modified by different organic acids regarding its wetting potential. Wettability alteration from preferentially oil-wet core plugs was pursued with ethoxylated tertiary amines and quaternary ammonium compounds. The main mechanism of wettability alteration towards more water-wet was proposed as extraction of carboxylate anions from the oil phase and the solid samples into aqueous micelles. Thus, high surfactant concentrations would result in improved recovery. From screening of different surfactant combinations in tertiary core flooding, one promising system of an alkyl ether sulfate and hexadecyltrimethylammonium combined with a terpolymer (TP) from acrylic acid, ATBS and NVP is proposed for the examined conditions. Low to moderate adsorption of the single surfactants and their combination as well as a favorable, stabilized phase behavior when combined with the polymer emphasize the applicability of the system. However, long term stability can be an issue with respect to the sulfate surfactant degradation at 70 °C. Analysis of mixed ionic surfactant systems after adsorption testing has been successfully pursued with a combined TC/TNb-determination.