Miscible CO2 Injection in Highly Heterogeneous Carbonate Cores: Experimental and Numerical Simulation Studies

Eidan, Ahmed Abdulaziz Al; Mamora, Daulat Debataraja

doi:10.2118/141469-ms

Cited by 3 publications

References 16 publications

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Experimental and Numerical Simulation Studies of Different Modes of CO2 Injection in Fractured Carbonate Cores

2011

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We have performed a miscible CO 2 flood study using fractured and unfractured carbonate cores and 31° API west Texas oil to evaluate oil recovery under three main injection modes: SWAG, WAG, and CGI. For each injection mode, three cases were considered: unfractured, one horizontal fracture and two fractures (one horizontal and one vertical). Increasing the number of fractures will investigate different shape factors such as the elongated slab and sugar cube models. Then, a commercial simulator was used to match the experimental results and model the fractures. The experimental results may be summarized as follows. First, for the unfractured case, the oil recoveries for SWAG, WAG, and CGI are 98, 92, and 75 % of OOIP, respectively. Second, for the elongated slab case (one horizontal fracture), the oil recoveries for SWAG, WAG and CGI decreased to 72, 70, and 27 %, respectively. Third, for sugar cube model (two fractures), the oil recoveries for SWAG, WAG and CGI are 79, 79, and 55 %, respectively. The simulation shows that the improvement in recoveries during SWAG and WAG over CGI is a result of a better conformance provided by the injected water which hindered CO 2 mobility and decreased its cycling through the fracture. Also, the sugar cube model has shown better results than the elongated slab because of the presence of a vertical fracture in the middle which helped CO 2 to diffuse more in the matrix and contact oil. The results suggest that injecting CGI in fractured cases is not recommended and injecting water (wetting phase) along with CO 2 is essential. Finally, among all injection modes, SWAG has resulted in the most uniform displacement profile with the lowest residual oil saturation after the flood. This injection mode combines the benefits of water to transfer into the matrix with CO 2 excellent displacement.

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Experimental and Numerical Simulation Studies of Different Modes of CO2 Injection in Fractured Carbonate Cores

2011

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A Parametric Study of Reservoir Cooling for Enhanced Recovery by CO2 Flooding

Wang

Khanzode

Johns

2014

SPE Annual Technical Conference and Exhibition

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Slim-tube experiments and analytical calculations show that minimum miscible pressure (MMP) can significantly decrease with a relatively modest reduction in temperature. Compositional simulation, however, is often made under isothermal conditions even though a prior waterflood may have reduced reservoir temperature in the swept zones of the reservoir. This paper examines how cooling by a prior waterflood can impact recovery during a CO2 flood by lowering the MMP in the swept zones. The results show that for the cases considered injection of cooler water can increase incremental oil recovery significantly owing to MMP reduction in the zones swept by the solvent. A parametric simulation study demonstrates how injection temperature, initial reservoir pressure, formation heterogeneity, formation thickness, heat transfer with the over and under burden formations, and WAG ratio affect the incremental oil recovery. The simulations are conducted by performing a long waterflood of up to 2.0 PVI prior to CO2 injection. The water during the secondary recovery is injected at two temperatures for the 1-D and 2-D flow models. CO2 solvent is then injected continuously or in WAG at the same waterflood injection temperature. The increase in incremental recoveries (above what would have been obtained by a standard CO2 flood at original reservoir temperature) varied greatly depending on the flow dimension, initial reservoir pressure, level of heterogeneity, formation thickness, the degree of energy gain from the surroundings, and the injection temperature. Increases in recovery by CO2 flooding varied from a few %OOIP to over 20% with the highest recoveries occurring in 1 -D flow. For the same flow dimension, the largest increase in recoveries is achieved when the MMP is sufficiently reduced by temperature so that an otherwise immiscible or near miscible flood becomes a multicontact-miscible (MCM) flood. The results demonstrate that including temperature variations in the simulations is important for floods that are near miscible as recoveries are most impacted in that region. Further, including temperature variations could be very important to improve the quality of history matches used to understand the reservoir. Lastly, we give a new MMP correlation for CO2 injection based on the most recent slim-tube data from the literature.

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A Parametric Study of Reservoir Cooling for Enhanced Recovery by Carbon Dioxide Flooding

2016

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Summary Slimtube experiments and analytical calculations show that minimum miscibility pressure (MMP) can significantly decrease with a relatively modest reduction in temperature. Compositional simulation, however, is often made under isothermal conditions even though a prior waterflood may have reduced reservoir temperature in the swept zones of the reservoir. This study uses computer simulation to examine how cooling by a prior waterflood can affect recovery during a carbon dioxide (CO2) flood by lowering the MMP in the swept zones. The results show that for the cases considered, injection of cooler water can increase incremental oil recovery (IOR) significantly because of MMP reduction in the zones swept by the solvent. A parametric simulation study demonstrates how injection temperature, initial reservoir pressure, formation heterogeneity, formation thickness, heat transfer with the overburden/underburden formations, and water-alternating-gas (WAG) ratio may affect the IOR. The simulations are conducted by a long waterflood of up to 2.0 pore volumes injected before CO2 injection. The water during the secondary recovery is injected at several temperatures for selected 1D, 2D, and 3D flow models. CO2 solvent is then injected continuously, or in WAG mode, at the same waterflood-injection temperature. The increase in IORs (greater than what would have been obtained by a standard CO2 flood at original reservoir temperature) varied greatly depending on the flow dimension, initial reservoir pressure, level of heterogeneity, formation thickness, degree of energy gain from the surroundings, and injection temperature. Increases in recovery by CO2 flooding varied from a few percent to nearly 30% of original oil in place, with the highest recoveries occurring in 1D flow. For the same flow dimension, the largest increase in recoveries is achieved when the MMP is sufficiently reduced by temperature so that an otherwise immiscible or near-miscible flood becomes a multicontact miscible flood. The results demonstrate that including temperature variations in the simulations is important for floods that are nearly miscible because recoveries are most affected in that region. Further, including temperature variations could be very important to improve the quality of history matches used to understand the reservoir.

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Miscible CO2 Injection in Highly Heterogeneous Carbonate Cores: Experimental and Numerical Simulation Studies

Cited by 3 publications

References 16 publications

Experimental and Numerical Simulation Studies of Different Modes of CO2 Injection in Fractured Carbonate Cores

Experimental and Numerical Simulation Studies of Different Modes of CO2 Injection in Fractured Carbonate Cores

A Parametric Study of Reservoir Cooling for Enhanced Recovery by CO2 Flooding

A Parametric Study of Reservoir Cooling for Enhanced Recovery by Carbon Dioxide Flooding

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