An Evaluation of the EOR Potential in Shale Oil Recovery by Cyclic Natural Gas Injection

Gamadi, Talal; Sheng, James J.

doi:10.15530/urtec-2014-1922690

Cited by 28 publications

(30 citation statements)

References 9 publications

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“…A general conclusion was that recovery factor was increased with increasing injection pressure. Some authors concluded that re-pressurization is the primary oil recovery mechanism for the huff-n-puff process [7,31,32]. Further investigations [29,32] indicated that increasing pressure only resulted in a good recovery performance at immiscible condition.…”

Section: Sensitivity Analysismentioning

confidence: 99%

“…However, a long shut-in period would result in a shorter production time. The optimum soaking time can be determined by calculating the gross/net gas utilization [7], as well as associating the cycle numbers and pressure distribution [36]. Some experimental and simulation results indicated that at miscible CO 2 injection condition, a longer soaking period allowed gas to diffuse further into the matrix, leading to a higher accumulative recovery [7,31,32].…”

Section: Sensitivity Analysismentioning

confidence: 99%

“…The optimum soaking time can be determined by calculating the gross/net gas utilization [7], as well as associating the cycle numbers and pressure distribution [36]. Some experimental and simulation results indicated that at miscible CO 2 injection condition, a longer soaking period allowed gas to diffuse further into the matrix, leading to a higher accumulative recovery [7,31,32]. Some studies reported that in a fixed duration of time, shortening the soaking time and allowing for more cycle numbers was more effective than a long soaking time with fewer cycles [9,15,32,37].…”

Section: Sensitivity Analysismentioning

confidence: 99%

“…The effect of heterogeneity of reservoir formation on huff-n-puff or cyclic natural gas injection efficiency has also been investigated [5,7,16,37]. The common conclusion that was drawn by different authors was that the recovery factor for a heterogeneous reservoir with low-permeability region outperformed homogenous reservoirs, since, for the latter one, CO 2 migrates into the deeper formation without playing the role of increasing the reservoir pressure and carrying oil back to the well.…”

Section: Sensitivity Analysismentioning

confidence: 99%

“…However, the salinity of connate water could reduce the EGR performance by decreasing the dispersion coefficient of CO 2 into CH 4 [92]. In addition, the intrinsic heterogeneity of shale rock generally negatively affects gas production in primary depletion [93,94]; however, it is expected to play a positive role in huff-n-puff gas injection EGR, similar to oil shale EOR [5,7,16,37,94]. A similar performance has also been reported for conventional rocks [95], as injection of the CO 2 and CH 4 mixture in heterogeneous carbonate rocks outperformed the same EOR process in homogeneous sandstones.…”

Section: Gas Injection-enhanced Recovery Mechanismsmentioning

confidence: 99%

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A Review of Gas Injection in Shale Reservoirs: Enhanced Oil/Gas Recovery Approaches and Greenhouse Gas Control

Nojabaei

2019

Energies

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Shale oil and gas resources contribute significantly to the energy production in the U.S. Greenhouse gas emissions come from combustion of fossil fuels from potential sources of power plants, oil refineries, and flaring or venting of produced gas (primarily methane) in oilfields. Economic utilization of greenhouse gases in shale reservoirs not only increases oil or gas recovery, but also contributes to CO2 sequestration. In this paper, the feasibility and efficiency of gas injection approaches, including huff-n-puff injection and gas flooding in shale oil/gas/condensate reservoirs are discussed based on the results of in-situ pilots, and experimental and simulation studies. In each section, one type of shale reservoir is discussed, with the following aspects covered: (1) Experimental and simulation results for different gas injection approaches; (2) mechanisms of different gas injection approaches; and (3) field pilots for gas injection enhanced oil recovery (EOR) and enhanced gas recovery (EGR). Based on the experimental and simulation studies, as well as some successful field trials, gas injection is deemed as a potential approach for EOR and EGR in shale reservoirs. The enhanced recovery factor varies for different experiments with different rock/fluid properties or models incorporating different effects and shale complexities. Based on the simulation studies and successful field pilots, CO2 could be successfully captured in shale gas reservoirs through gas injection and huff-n-puff regimes. The status of flaring gas emissions in oilfields and the outlook of economic utilization of greenhouse gases for enhanced oil or gas recovery and CO2 storage were given in the last section. The storage capacity varies in different simulation studies and is associated with well design, gas injection scheme and operation parameters, gas adsorption, molecular diffusion, and the modelling approaches.

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