Molecular insights of condensate trapping mechanism in shale oil reservoirs and its implications on lean gas enhanced oil recovery

Wang, Shihao; Zhang, Hongwei; Jin, Bikai; Qiao, Rui; Wen, Xian-Huan

doi:10.1016/j.cej.2023.146366

Cited by 2 publications

(2 citation statements)

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“…Given the distinct adsorption of C10 and C19 on pore walls, following convention, ,,,,, we divide each component in the pore into two populations: the “adsorbed” oil and the “free” oil (i.e., those on the left and right sides of the dashed line in Figure a). As we will see later, from a transport perspective, the oil molecules in the second adsorption layer ( z = 0.53–0.97 nm) are much more mobile than those in the first adsorption layer and are relatively close to those of bulk oil.…”

Section: Resultsmentioning

confidence: 99%

“…The recovery of oil from the pore is thus similar to the loss of oil trapped inside the shale core samples exposed to a low-pressure environment. The present case is also relevant to the situation where condensates are trapped in unconventional reservoirs during the final stage of the primary recovery, 41 when the pressure difference between the pore and fracture can no longer drive oil recovery.…”

Section: Resultsmentioning

confidence: 99%

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Enhanced Recovery of Oil Mixtures from Calcite Nanopores Facilitated by CO₂ Injection

Zhang,

Wang,

Wang

et al. 2024

Energy Fuels

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Slow production, preferential recovery of light hydrocarbons, and low recovery factors are common challenges in oil production from unconventional reservoirs dominated by nanopores. Gas injection-based techniques such as CO 2 Huff-n-Puff have shown promise in addressing these challenges. However, a limited understanding of the recovery of oil mixtures on the nanopore scale hinders their effective optimization. Here, we use molecular dynamics simulations to study the recovery of an oil mixture (C10 + C19) from a single 4 nm-wide calcite dead-end pore, both with and without CO 2 injection. Without CO 2 injection, oil recovery is much faster than expected from oil vaporization and features an undesired selectivity, i.e., the preferential recovery of lighter C10. With CO 2 injection, oil recovery is accelerated and its selectivity toward C10 is greatly mitigated. These recovery behaviors are understood by analyzing the spatiotemporal evolution of C10, C19, and CO 2 distributions in the calcite pore. In particular, we show that interfacial phenomena (e.g., the strong adsorption of oil and CO 2 on pore walls, their competition, and their modulation of transport behavior) and bulk phenomena (e.g., solubilization of oil by CO 2 in the middle portion of the pore) play crucial roles in determining the oil recovery rate and selectivity.

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Section: Resultsmentioning

confidence: 99%

Section: Resultsmentioning

confidence: 99%

Enhanced Recovery of Oil Mixtures from Calcite Nanopores Facilitated by CO₂ Injection

Zhang,

Wang,

Wang

et al. 2024

Energy Fuels

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Dynamic Behaviors of CO2 Enhanced Shale Oil Flow in Nanopores by Molecular Simulation

Tian,

Wang,

et al. 2024

SPE Journal

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Summary With the development of unconventional oil and gas, shale oil has become a significant focus for exploration and development. The mineral composition of shale is notably complex, and the mechanisms underlying carbon dioxide (CO2)-enhanced shale oil flow remain insufficiently understood. While many studies have addressed adsorption in shale oil and gas, research into the dynamic flow of CO2 and shale oil within pore spaces is limited. To investigate the mobility behavior of CO2 and shale oil in nanopores from a microscopic perspective, a dynamic flow model for CO2-enhanced shale oil flow, considering wall adsorption effects, was established by using the Non-Equilibrium Molecular Dynamics (NEMD) method. This model simulated CO2-enhanced shale oil flow within organic nanopores under reservoir conditions and analysed the effects of pore size, temperature, and injection pressure. The results show that shale oil forms four adsorption layers in 4-nm graphene pores, with a density of 2.25 g/cm3 in the first adsorption layer and 0.63 g/cm3 in the free zone, closely aligning with the standard shale oil density of 0.66 g/cm3 at 343 K and 25 MPa, thereby validating the accuracy of the model. The peak density of the first adsorption layer is 3.55 times that of the free zone, highlighting shale oil’s strong adsorption capacity at the pore wall. The study reveals that the diffusion coefficients of CO2 within the pores are 1.05, 1.14, and 1.41 times higher than those of pentane, octane, and dodecane, respectively. Additionally, the diffusion coefficient of shale oil increased by 10.3 times when the pore size increased from 2 to 5 nm, and by 3.9 times when the temperature rose from 303 to 383 K. Injection pressure also led to a 1.5 times increase in diffusion coefficients. Thus, in shale oil development, adjusting pore size, temperature, and injection pressure can enhance production, although excessive injection pressure may result in CO2 gas channeling, negatively impacting CO2-enhanced shale oil flow. This study offers a microscopic exploration of CO2-enhanced shale oil flow mechanisms and provides a theoretical foundation for efficient shale oil development.

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Molecular insights of condensate trapping mechanism in shale oil reservoirs and its implications on lean gas enhanced oil recovery

Cited by 2 publications

References 32 publications

Enhanced Recovery of Oil Mixtures from Calcite Nanopores Facilitated by CO₂ Injection

Enhanced Recovery of Oil Mixtures from Calcite Nanopores Facilitated by CO₂ Injection

Dynamic Behaviors of CO2 Enhanced Shale Oil Flow in Nanopores by Molecular Simulation

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Molecular insights of condensate trapping mechanism in shale oil reservoirs and its implications on lean gas enhanced oil recovery

Cited by 2 publications

References 32 publications

Enhanced Recovery of Oil Mixtures from Calcite Nanopores Facilitated by CO2 Injection

Enhanced Recovery of Oil Mixtures from Calcite Nanopores Facilitated by CO2 Injection

Dynamic Behaviors of CO2 Enhanced Shale Oil Flow in Nanopores by Molecular Simulation

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Enhanced Recovery of Oil Mixtures from Calcite Nanopores Facilitated by CO₂ Injection

Enhanced Recovery of Oil Mixtures from Calcite Nanopores Facilitated by CO₂ Injection