Performance of CO2 Foam Huff and Puff in Tight Oil Reservoirs

Abstract

The challenges associated with unconventional reservoirs are related to their intrinsic nature: extremely low porosity and permeability. Combinations of horizontal wells and multistage hydraulic fracturing techniques have been developed to overcome the production obstacles and unlock the vast amount of oil in place in such formations. However, oil production still exhibits a sharp decline within the first 2 years after the stimulation, leading to an oil recovery of less than 15%. Thus, enhanced oil recovery methods need to be investigated to further increase the production rates and the recovery. In this study, laboratory experiments and numerical simulations were conducted to evaluate the performance of the CO2 foam huff and puff process and its impacts on oil recovery in tight oil formations. More specifically, the foam half-life was measured as a function of surfactant concentration and followed by the foam drainage ratio and its rheological properties in the subsequent tests. Reservoir simulations were conducted using the lab data and the field data collected from Cardium formation. Sensitivity analyses were finally carried out to investigate the effects of controlling variables on the CO2 foam performance. Experimental results revealed that the optimal surfactant concentration was found to be 0.2%, which is the critical micelle concentration point. Simulation results show that CO2 foam huff and puff can increase the oil recovery by more than 11% compared to that of the primary production. Moreover, sensitivity analyses show that the production time, injection time, and soaking time are the main effecting parameters, while the injection rate and the incremental injection rate are less important.

Study on the Stabilization Mechanism of Wormlike Micelle-CO2 Foams in High-Temperature and High-Salt Oil Reservoirs

“…When the system continues to heat up, the rate of foam generation is inhibited, and under the shearing action of strong external force, considerable portion of the foam tends to be oriented in the direction of flow, causing a precipitous decline in apparent viscosity. Moreover, considering the increase in the particle size of the bubbles, the liquid film of the bubbles became thinner, most of the fluids chose to move closer to the plateau boundary, and the physical and chemical properties of the foam film were also be greatly reduced as a consequence . Continuous external shear can break the establishment of the stable structure of the foam system, and its apparent viscosity will further deteriorate.…”

“…Moreover, considering the increase in the particle size of the bubbles, the liquid film of the bubbles became thinner, most of the fluids chose to move closer to the plateau boundary, and the physical and chemical properties of the foam film were also be greatly reduced as a consequence. 32 Continuous external shear can break the establishment of the stable structure of the foam system, and its apparent viscosity will further deteriorate. Conversely, provided that the micelle system is not affected by adverse temperature conditions, the WLM-CO 2 foam structure is tighter, the size of the foam is not very different from each other, overall more even distribution of the foam, and the liquid phase is more uniformly distributed around the liquid film and the plateau.…”

Recovery mechanisms and formation influencing factors of miscible CO2 huff-n-puff processes in shale oil reservoirs: A systematic review

“…Except for oil swelling, another critical mechanism is viscosity reduction, the result of CO 2 dissolution into crude oil (Li et al, 2013;Barclay and Mishra, 2016;Or et al, 2016). For example, the application of CO 2 huff-n-puff technique in the Fuyu oil reservoir could lead to a substantial reduction in the viscosity of crude oil, that is, up to 50.7% (Shabib-Asl et al, 2022). In fact, almost all injected gas during EOR can cause the reduction of in-situ crude oil viscosity to various extents.…”