Experimental Investigation of Oil Recovery From Siliceous Shale by Miscible CO2 Injection

Vega, Bolivia; O’Brien, William J.; Kovscek, Anthony R.

doi:10.2118/135627-ms

Cited by 43 publications

(25 citation statements)

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“…Shyeh-Yung (Shyeh-Yung, 1991) concluded that two mechanisms of CO 2 EOR were low interfacial tension (IFT) displacement and extraction of oil components, and the latter dominated after CO 2 breakthrough. Vega B. et al (Vega, O'Brien, and Kovscek, 2010) conducted the miscible injection of CO 2 into siliceous shale. CO 2 injection under countercurrent (diffusion-like) conditions achieved 54% recovery of the OOIP and subsequent (displacement-like) cocurrent process yielded 39% recovery of the OOIP with a total 93% oil recovery.…”

Section: Introductionmentioning

confidence: 99%

Nuclear Magnetic Resonance Study on Mechanisms of Oil Mobilization in Tight Reservoir Exposed to CO2 in Pore Scale

Wang

Lun

et al. 2016

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Nuclear magnetic resonance (NMR) was used to investigate the exposure between CO 2 and matrix with permeability of 0.218 mD at 40°C and 12 MPa. Before NMR experiment, the core was saturated with oil. To investigate the effects of exposure time on EOR, the saturated core was exposed to CO 2 and T2 test was continuously performed with NMR system until the obtained T2 spectrum was unchanged. After the first exposure, CO 2 and matrix reached equilibrium state. The second exposure started when CO 2 injection was under a constant pressure of 12 MPa and at a constant rate to keep fresh CO 2 in system. The procedure of T2 test was unchanged. The third and fourth exposures were conducted in sequence. The results showed that (1) Oil in all pores can mobilize as exposure time increases. (2) The recovery is 46.6% for oil in pores with the diameter of pore larger than 1 m, this result is higher than the recovery (12.8%) for oil in pores with the diameter of pore smaller than 1 m. (3) Recovery can be divided into two stages according to the exposure time: a fast-growing stage and a slow-growing stage. (4) Initially, the oil exists in pores with maximum radius of 21 m in the originally saturated core. After CO 2 injection, oil flows to pores with radius greater than 21 m, suggesting that oil in tight matrix ЉdiffusesЉ to the surface of core with exposure between CO 2 and matrix. (5) The final recoveries of 1 st , 2 nd , 3 rd , 4 th exposure experiments are 23.7%, 7.2%, 2.6% and 1.5%, respectively.

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Section: Introductionmentioning

confidence: 99%

Nuclear Magnetic Resonance Study on Mechanisms of Oil Mobilization in Tight Reservoir Exposed to CO2 in Pore Scale

Wang

Lun

et al. 2016

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“…Miscible CO 2 injection increased recovery from 6.02% obtained under primary production to 21.58% of OOIP. Vega et al (2010) studied miscible CO 2 injection into siliceous shale with 1.3 md permeability and 34% porosity. Experimental and simulation results together with computed tomography image analysis revealed CO 2 was able to penetrate from the fracture to the matrix and recover almost all the oil.…”

Section: Introductionmentioning

confidence: 99%

Experimental Investigation of Enhanced Recovery in Unconventional Liquid Reservoirs using CO2: A Look Ahead to the Future of Unconventional EOR

Tovar

Eide

Graue

et al. 2014

SPE Unconventional Resources Conference

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The poor rock quality and matrix permeability several orders of magnitude lower than conventional oil reservoirs observed in unconventional liquid reservoirs (ULR) presents many uncertainties on the storage capacity of the rock and the possibility of enhancing recovery. The technological advances in multiple stage hydraulic fracturing and horizontal drilling have improved the overall profitability of oil shale plays by enhancing the matrix -wellbore connectivity. The combination of these technologies has become the key factor for the operators to reach economically attractive production rates in the exploitation of ULR, causing a lot of focus on their improvement. However, as the reservoir matures, primary production mechanisms no longer drive oil to the hydraulic fractures, making the improvement of matrix -wellbore connectivity insufficient to provide economically attractive production rates. Therefore, the need to develop enhanced recovery techniques in order to improve the displacement of the oil from the matrix, maintain profitable production rates, extend the life of the assets and increase ultimate oil recovery becomes evident.This study presents experimental results on the use of CO 2 as an enhanced oil recovery (EOR) agent in preserved, rotary sidewall reservoir core samples with negligible permeability. To simulate the presence of hydraulic fractures, the ULR cores were surrounded by high permeability glass beads and packed in a core holder. The high permeability media was then saturated with CO 2 at constant pressure and temperature during the experiment. Production was monitored and the experiment was imaged using x-ray computed tomography to track saturation changes inside the core samples.The results of this investigation support CO 2 as a promising EOR agent for ULR. Oil recovery was estimated to be between 18 to 55% of OOIP. We provide a detailed description of the experimental set up and procedures. The analysis of the x-ray computed tomography images revealed saturation changes within the ULR core as a result of CO 2 injection. A discussion about the mechanisms is presented, including diffusion and reduction in capillary forces. This paper opens a door to the investigation of CO 2 enhanced oil recovery in ULR.

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“…Different investigators have demonstrated the efficiency of molecular diffusion in fractured reservoirs (e.g. da Silva and Belery, 1989;Hu and Whitson, 1991;Darvish et al, 2006;Hoteit and Firoozabadi, 2009;Vega et al, 2010;Jamili et al, 2010).…”

Section: Introductionmentioning

confidence: 99%

“…da Silva and Belery, 1989;Coats, 1989;Darvish et al, 2006;Vega et al, 2010;Jamili et al, 2010), multicomponent molecular diffusion is modeled using a classical Fick's law approach with effective diffusion coefficients. This means the diffusion flux of each component will always be in the opposite direction of its concentration gradient.…”

Section: Introductionmentioning

confidence: 99%

Diffusion and Matrix-Fracture Interactions during Gas Injection in Fractured Reservoirs

Shojaei

Jessen

2014

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Molecular diffusion can play a significant role in oil recovery during gas injection in fractured reservoirs. Diffusion of gas components from a fracture into the matrix extracts oil components from matrix and delays, to some extent, the gas breakthrough. This in turn increases both sweep and displacement efficiencies.In current simulation models, molecular diffusion is commonly modeled using a classical Fick's law approach with constant diffusion coefficients. In the classical Fick's law approach, the dragging effects (off-diagonal diffusion coefficients) are neglected. In addition, the gas-oil diffusion at the fracture-matrix interface is normally modeled by assuming an average composition at the interface which does not have a sound physical basis.In this paper, we present a dual-porosity model in which the generalized Fick's law is used for molecular diffusion to account for the dragging effects; and gas-oil diffusion at the fracture-matrix interface is modeled based on film theory in which the gas in fracture and oil in the matrix are assumed to be at equilibrium. A novel shape factor is also introduced for gas-oil diffusion based on film theory. Diffusion coefficients are calculated using the Maxwell-Stefan model and are pressure, temperature and composition dependent. A time-dependent transfer function is used for matrix-fracture exchange in which the shape factor is adjusted using a boost factor to differentiate between the transfer rate at early and late times.Field-scale examples are used to demonstrate that the dragging effects (off-diagonal diffusion coefficients) can significantly impact the oil recovery during gas injection in fractured reservoirs. It is also shown that using proper physical models for matrix-fracture interactions (film theory for gas-oil diffusion and transfer function with boost factor) can considerably affect the simulation results as compared to conventional models. We also show that miscibility is not developed in the matrix blocks even at pressures above minimum miscibility pressure (MMP) when molecular diffusion is the main recovery mechanism during gas injection in fractured reservoirs.The work presented in this paper is directly applicable to the study and design of gas injection processes in fractured reservoirs through an improved understanding of the effect of diffusion and matrix-fracture interactions on these processes.

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Experimental Investigation of Oil Recovery From Siliceous Shale by Miscible CO2 Injection

Cited by 43 publications

References 10 publications

Nuclear Magnetic Resonance Study on Mechanisms of Oil Mobilization in Tight Reservoir Exposed to CO2 in Pore Scale

Nuclear Magnetic Resonance Study on Mechanisms of Oil Mobilization in Tight Reservoir Exposed to CO2 in Pore Scale

Experimental Investigation of Enhanced Recovery in Unconventional Liquid Reservoirs using CO2: A Look Ahead to the Future of Unconventional EOR

Diffusion and Matrix-Fracture Interactions during Gas Injection in Fractured Reservoirs

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