Aqueous solution of ketone solvent for enhanced oil recovery in tight reservoirs
Creators: name: Wang, Mingyuan, 1991-
Publisher: name: The University of Texas at Austin
Year: 2021
Subjects: Enhanced oil recovery
Tight reservoirs
Ketone
Imbibition

description: Horizontal drilling and multi-stage hydraulic fracturing have made it possible to recover oil from tight formations at economically feasible production rates. However, tight oil reservoirs often show a rapid decline in the production rate. Primary recovery factors in tight reservoirs are typically smaller than 10%. There is a critical need for enhanced oil recovery in tight reservoirs. Most tight oil reservoirs are originally intermediate- to oil-wet. Wettability alteration agents have been studied to facilitate water imbibition into tight rock matrices to enhance oil recovery. However, many factors affect the efficacy and efficiency of enhanced oil recovery by wettability alteration agents. The conventional wettability modifiers, such as surfactants, decrease the interfacial tension between the aqueous and oleic phases, which tends to limit the imbibition rate. The performance of wettability modifiers also depends on their mass transfer from the fracture to the matrix. However, the mass transfer of components between the fracture and the matrix has not been studied quantitatively in the literature. In addition, initial water saturation in the matrix, the concentration of wettability modifier in the injection fluid, and the injection/production pressures also affect the efficacy and efficiency of enhanced oil recovery by wettability alteration agents. This research aims to identify a practical solvent that can alter rock wettability without affecting interfacial tension and transfer efficiently from fracture to matrix. In addition, the effect of initial water saturation on enhanced water imbibition and the impact of the chemical concentration of the injected aqueous solution is investigated. In this research, we identified 3-pentanone, a symmetric dialkyl ketone, can act as a wettability alteration agent without affecting the interfacial tension between the aqueous and oleic phases. It is conceivable that the wettability change caused by 3-pentanone is related to the polar-polar interaction between 3-pentanone molecules and the calcite surface. This interaction may reduce the polar-polar interaction of the carboxylate group of naphthenic acids in oil with the calcite surface. Next, we compared 3-pentanone with a common wettability modifier, a surfactant. The dynamic imbibition experiments demonstrated that 3-pentanone was more efficient in transferring from a fracture to the surrounding matrices than the surfactant. Results indicated that an optimal process with a wettability modifier would have a large imbibed fraction to rapidly enhance the oil displacement by brine in the matrix. Then, we demonstrated that the 3-pentanone solution increased the oil recovery from the shale matrix in comparison to the injection brine through huff-n-puff experiments. Last, we developed a new method for reliable determination of saturation pressure from constant-mass expansion data even when the total compressibility of the fluid does not show a detectable change near the saturation pressure. The new method has been used successfully to design the live-oil experiments in this and other research projects