A Comprehensive Model for Investigation of Carbon Dioxide Enhanced Oil Recovery With Nanopore Confinement in the Bakken Tight Oil Reservoir

Abstract

Summary Carbon dioxide (CO2) injection is an effective enhanced-oil-recovery (EOR) method in unconventional oil reservoirs. However, investigation of the CO2 huff ’n’ puff process in tight oil reservoirs with nanopore confinement is lacking in the petroleum industry. The conventional models need to be modified to consider nanopore confinement in both phase equilibrium and fluid transport. Hence, we develop an efficient model to fill this gap and apply to the field production of the Bakken tight oil reservoir. Complex-fracture geometries are also handled in this model. First, we revised the phase equilibrium calculation and evaluated the fluid properties with nanopore confinement. An excellent agreement between this proposed model and the experimental data is obtained considering nanopore confinement. Afterward, we verified the calculated minimum miscibility pressure (MMP) using this model against the experimental data from a rising-bubble apparatus (RBA). We analyzed the MMP and well performance of CO2 EOR in the Bakken tight oil reservoir. On the basis of the prediction of the field data, the MMP is 450 psi lower than the MMP with bulk fluid when the pore size reduces to 10 nm. Subsequently, we examined the effects of key parameters such as matrix permeability and CO2 molecular diffusion on the CO2 huff ’n’ puff process. Results show that both CO2-diffusion and capillary pressure effects improve the oil recovery factor from tight oil reservoirs, which should be correctly implemented in the simulation model. Finally, we analyzed well performance of a field-scale horizontal well from the Bakken Formation with nonplanar fractures and natural fractures. Contributions of CO2-diffusion and capillary pressure effects are also examined in depth in field scale with complex-fracture geometries. The oil recovery factor of the CO2 huff ’n’ puff process with both CO2-diffusion and capillary pressure effects increases by as much as 5.1% in the 20-year period compared with the case without these factors. This work efficiently analyzes the CO2 huff ’n’ puff process with complex-fracture geometries considering CO2 diffusion and nanopore confinement in the field production from the Bakken tight oil reservoir. This model can provide a strong basis for accurately predicting the long-term production with complex-fracture geometries in tight oil reservoirs.

A Literature Review of CO2, Natural Gas, and Water-Based Fluids for Enhanced Oil Recovery in Unconventional Reservoirs

“…MMP was more accurately predicted when the effects of nanoconfinement were included. 242 Sanaei et al compared four gases (CO 2 , N 2 , methane, and an 85% methane−15% ethane mixture) in a study of huff-n-puff in the Middle Bakken. Repressurization and oil swelling (not diffusion) were identified as the dominant mechanisms of oil recovery (Table 5, entry 21).…”

Thermodynamic effects of cycling carbon dioxide injectivity in shale reservoirs

“…The interaction of carbon dioxide with formation fluid has led to reduce oil viscosity and enhance the mobility ratio. The profound impact of crucial parameters such as temperature, pressure, carbon dioxide soaking time, and core stimulation on the oil recovery enhancement should be taken into consideration before performing recovery processes (Zhang et al, 2019;Li et al, 2019;Alfarge et al, 2018;Pranesh, 2018).…”

Compositional Simulation of Geological and Engineering Controls on Gas Huff-n-Puff in Duvernay Shale Volatile Oil Reservoirs, Canada

“…Most studies [14][15][16][17][18][19][20] on huff-n-puff simulation in shale reservoirs are focused on operational parameters control during huff-n-puff, including injection rate, injection time, injection pressure, soaking time, production time, flowing bottom-hole pressure (BHP), and number of huff-n-puff cycles. Chen et al [21] studied the effect of reservoir heterogeneity on CO 2 huff-n-puff in shale oil reservoirs.…”