A novel experimental investigation on the occurrence state of fluids in microscale pores of tight reservoirs

Dong, Xiaohu; Chen, Zhangxin; Hou, Yuguang; Luo, Qilan; Chen, Yihang

doi:10.1016/j.petrol.2020.107656

Cited by 23 publications

(14 citation statements)

References 21 publications

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“…According to the previous discussion, CO 2 can usually extract the light components from crude oil . The closest film-like oil to a pore wall is a heavy component, and the other side is a light component. , It is also the result of a contact between CO 2 and light components in crude oil. Therefore, it is shown that CO 2 can extract light components more effectively and thus further unlock an oil film in a porous medium.…”

Section: Results and Discussionmentioning

confidence: 99%

Pore-Scale Movability Evaluation for Tight Oil Enhanced Oil Recovery Methods Based on Miniature Core Test and Digital Core Construction

Dong

Chen

Hou

et al. 2020

Ind. Eng. Chem. Res.

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The movability of micro-remaining oil in microscale pores in tight reservoirs directly affects the recoverability of a reservoir fluid. Currently, core displacement and digital cores have been applied for the reservoir fluid movability and microstructure visualization. In this study, we present a practical framework for the pore-scale movability of tight oil, which combines core displacement tests and digital cores on real tight core samples. In this framework, the core displacement tests and miniature core displacement tests using three different displacement methods (water flooding, CH 4 flooding, and CO 2 flooding) are first performed. Then, through a series of CT (computed tomography) scanning results on the core displacement tests, a digital core model is constructed, and a distribution of micro-remaining oil is experimentally investigated. By combining the results of the miniature core displacement tests and the digital core model, the types and movability of tight oil at different times for the three methods are obtained. These results indicate that the remaining tight oil at pore scale can be classified into three different categories according to a shape factor (S) of the remaining oil, including block-like oil (4.85 > S > 1), flat-like oil (12.22 > S > 4.85) and film-like oil (S > 12.22). From CT scanning results, the method of water flooding can effectively unlock the type of block-like oil, while CH 4 flooding and CO 2 flooding can produce flat-like and film-like oil. Furthermore, CO 2 flooding can significantly unlock more film-like oil than CH 4 flooding.

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Section: Results and Discussionmentioning

confidence: 99%

Pore-Scale Movability Evaluation for Tight Oil Enhanced Oil Recovery Methods Based on Miniature Core Test and Digital Core Construction

Dong

Chen

Hou

et al. 2020

Ind. Eng. Chem. Res.

Self Cite

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“…Pinho et al [14] introduced a novel technique to conduct a microfluidic multicomponent phase behavior and showed that multicomponent P-T diagrams are altered under nanopore confinement effect. Other experimental techniques including temperature-programmed desorption (TPD) [15], neutron diffraction [16], volumetric measurement [17], X-ray diffraction [18], scanning electron microscope (SEM) [19], and micro-CT scanning [20] also have found similar phenomena in nanopores. All these experiments showed that nanoscale interaction had a remarkable effect on the gas-liquid equilibrium of hydrocarbon components, but the results were influenced by experimental materials, and there were few experimental studies on the phase behavior in nanopores with a radius smaller than 50 nm was present in the literature due to the unconventional characteristics of tight oil reservoirs and the limitations of laboratory equipment.…”

Section: Introductionmentioning

confidence: 92%

Nanopore Confinement Effect on the Phase Behavior of CO2/Hydrocarbons in Tight Oil Reservoirs considering Capillary Pressure, Fluid-Wall Interaction, and Molecule Adsorption

Zheng

2021

Geofluids

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The pore sizes in tight reservoirs are nanopores, where the phase behavior deviates significantly from that of bulk fluids in conventional reservoirs. The phase behavior for fluids in tight reservoirs is essential for a better understanding of the mechanics of fluid flow. A novel methodology is proposed to investigate the phase behavior of carbon dioxide (CO2)/hydrocarbons systems considering nanopore confinement. The phase equilibrium calculation is modified by coupling the Peng-Robinson equation of state (PR-EOS) with capillary pressure, fluid-wall interaction, and molecule adsorption. The proposed model has been validated with CMG-Winprop and experimental results with bulk and confined fluids. Subsequently, one case study for the Bakken tight oil reservoir was performed, and the results show that the reduction in the nanopore size causes noticeable difference in the phase envelope and the bubble point pressure is depressed due to nanopore confinement, which is conductive to enhance oil recovery with a higher possibility of achieving miscibility in miscible gas injection. As the pore size decreases, the interfacial tension (IFT) decreases whereas the capillary pressure increases obviously. Finally, the recovery mechanisms for CO2 injection are investigated in terms of minimum miscibility pressure (MMP), solution gas-oil ratio, oil volume expansion, viscosity reduction, extraction of lighter hydrocarbons, and molecular diffusion. Results indicate that nanopore confinement effect contributes to decrease MMP, which suppresses to 650 psi (65.9% smaller) as the pore size decreases to 2 nm, resulting in the suppression of the resistance of fluid transport. With the nanopore confinement effect, the CO2 solution gas-oil ratio and the oil formation volume factor of the oil increase with the decrease of pore size. In turn, the oil viscosity reduces as the pore size decreases. It indicates that considering the nanopore confinement effect, the amount of gas dissolved into crude oil increases, which will lead to the increase of the oil volume expansion and the decrease of the viscosity of crude oil. Besides, considering nanopore confinement effect seems to have a slightly reduced effect on extraction of lighter hydrocarbons. On the contrary, it causes an increase in the CO2 diffusion coefficient for liquid phase. Generally, the nanopore confinement appears to have a positive effect on the recovery mechanisms for CO2 injection in tight oil reservoirs. The developed novel model could provide a better understanding of confinement effect on the phase behavior of nanoscale porous media in tight reservoirs. The findings of this study can also help for better understanding of a flow mechanism of tight oil reservoirs especially in the case of CO2 injection for enhancing oil recovery.

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“…It has been reported that the proportion of movable oil will increases with increasing burial depth. This phenomenon is related to the decrease in oil viscosity and density due to increasing temperature and light components (Wang et al, 2019b;Scheeder et al, 2020;Zhao W. Z. et al, 2021), which is conducive to a reduction in the oil film thickness and a relative increase in free oil in pores with the same pore size (Liu Y. S. et al, 2021). The increase in thermal maturity also leads to a decrease in the adsorption and swelling capacities of kerogen (Song et al, 2015;Wang et al, 2015b;Wang et al, 2019b reported that the decrease in adsorption capacity could be attributed to the reduction in TOC content with increasing maturity.…”

Section: Influencing Factors Of Movable Oilmentioning

confidence: 99%

Oil Retention in Shales: A Review of the Mechanism, Controls and Assessment

et al. 2021

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Shale oil is a vital alternative energy source for oil and gas and has recently received an extensive attention. Characterization of the shale oil content provides an important guiding significance for resource potential evaluation, sweet spot prediction, and development of shale oil. In this paper, the mechanism, evaluation and influencing factors of oil retention in shales are reviewed. Oil is retained in shales through adsorption and swelling of kerogen, adsorption onto minerals and storage in shale pores. Quite a few methods are developed for oil content evaluation, such as three-dimensional fluorescence quantitation, two-dimensional nuclear magnetic resonance (2D NMR), solvent extraction, pyrolysis, multiple extraction-multiple pyrolysis-multiple chromatography, logging calculation, statistical regression, pyrolysis simulation experiment, and mass balance calculation. However, the limitations of these methods represent a challenge in practical applications. On this basis, the influencing factors of the oil retention are summarized from the microscale to the macroscale. The oil retention capacity is comprehensively controlled by organic matter abundance, type and maturity, mineral composition and diagenesis, oil storage space, shale thickness, and preservation conditions. Finally, oil mobility evaluation methods are introduced, mainly including the multitemperature pyrolysis, 2D NMR, and adsorption-swelling experiment, and the influencing factors of movable shale oil are briefly discussed. The aim of this paper is to deepen the understanding of shale oil evaluation and provide a basis for further research.

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A novel experimental investigation on the occurrence state of fluids in microscale pores of tight reservoirs

Cited by 23 publications

References 21 publications

Pore-Scale Movability Evaluation for Tight Oil Enhanced Oil Recovery Methods Based on Miniature Core Test and Digital Core Construction

Pore-Scale Movability Evaluation for Tight Oil Enhanced Oil Recovery Methods Based on Miniature Core Test and Digital Core Construction

Nanopore Confinement Effect on the Phase Behavior of CO2/Hydrocarbons in Tight Oil Reservoirs considering Capillary Pressure, Fluid-Wall Interaction, and Molecule Adsorption

Oil Retention in Shales: A Review of the Mechanism, Controls and Assessment

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