An improved system for evaluating the adaptability of natural gas flooding in enhancing oil recovery considering the miscible ability

Tang, Yong; Chen, Yulin; He, Youwei; Yu, Gaoming; Guo, Xifeng; Yang, Qing; Yong, Wang

doi:10.1016/j.energy.2021.121441

Cited by 27 publications

(7 citation statements)

References 29 publications

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“…In addition, artificial intelligence (AI) has been widely used in the oil industry due to its outstanding performance, including development effect evaluation [77][78][79], data segmentation [80][81][82], and flow simulation [83,84]. In this study, the SOM machine learning method [55,85] was used to automatically classify the residual oil pattern.…”

Section: 42mentioning

confidence: 99%

Effects of Wettability and Minerals on Residual Oil Distributions Based on Digital Rock and Machine Learning

Zhang

Lin

et al. 2022

Lithosphere

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The wettability of mineral surfaces has significant impacts on transport mechanisms of two-phase flow, distribution characteristics of fluids, and the formation mechanisms of residual oil during water flooding. However, few studies have investigated such effects of mineral type and its surface wettability on rock properties in the literature. To unravel the dependence of hydrodynamics on wettability and minerals distribution, we designed a new experimental procedure that combined the multiphase flow experiments with a CT scan and QEMSCAN to obtain 3D digital models with multiple minerals and fluids. With the aid of QEMSCAN, six mineral components and two fluids in sandstones were segmented from the CT data based on the histogram threshold and watershed methods. Then, a mineral surface analysis algorithm was proposed to extract the mineral surface and classify its mineral categories. The in situ contact angle and pore occupancy were calculated to reveal the wettability variation of mineral surface and distribution characteristics of fluids. According to the shape features of the oil phase, the self-organizing map (SOM) method, one of the machine learning methods, was used to classify the residual oil into five types, namely, network, cluster, film, isolated, and droplet oil. The results indicate that each mineral’s contribution to the mineral surface is not proportional to its relative content. Feldspar, quartz, and clay are the main minerals in the studied sandstones and play a controlling role in the wettability variation. Different wettability samples show various characteristics of pore occupancy. The water flooding front of the weakly water-wet to intermediate-wet sample is uniform, and oil is effectively displaced in all pores with a long oil production period. The water-wet sample demonstrates severe fingering, with a high pore occupancy change rate in large pores and a short oil production period. The residual oil patterns gradually evolve from networks to clusters, isolated, and films due to the effects of snap-off and wettability inversion. This paper reveals the effects of wettability of mineral surface on the distribution characteristics and formation mechanisms of residual oil, which offers us an in-deep understanding of the impacts of wettability and minerals on multiphase flow and helps us make good schemes to improve oil recovery.

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Section: 42mentioning

confidence: 99%

Effects of Wettability and Minerals on Residual Oil Distributions Based on Digital Rock and Machine Learning

Zhang

Lin

et al. 2022

Lithosphere

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“…The results of oilfield development and application show that better development benefits can be obtained by gas injection to rise to the top of the reservoir and then drive down oil, − which inspires oilfield workers to take advantage of the automatic separation to formulate development plans by directly injecting gas at the top of the oil and gas production layer and use gravity differentiation and gas expansion to displace oil downward into production wells. − In response to this idea, Cardwell proposed the gravity drainage theory . Meszaros et al found that up to 70% of the oil reservoirs produced by gravity-stabilized gas flooding was by N 2 injection .…”

Section: Introductionmentioning

confidence: 99%

Establishment of Stability Evaluation Criteria for the Oil–Gas Interface during Gas-Cap Gravity Flooding in Oil Reservoirs with Strong Edge-Water Drive

et al. 2023

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A three-dimensional (3D) experimental model considering the influence of water energy is established to innovatively analyze oil−gas interface stability, and it is found that a stable gas cap with sufficient driving energy can be formed only under a stable oil and gas interface. So, the bidirectional displacement through the gas cap and edge water can be realized during the late development stage in the strong edge-water drive reservoirs. Results show that the recovery of bidirectional displacement can reach 60%, while the recovery of an unstable interface is basically below 50%. The recovery degree under a stable oil−gas interface is more than 25.63% than that of the unstable interface. Based on the Navier−Stokes equation, a "steady flow velocity u s " formula that considers the influence of multiple factors is defined, and the ratio of the flow velocity at the oil−gas interface to the gas injection rate is controlled between 0.6 and 0.85 to determine the criteria for the stable oil−gas interface. At the same time, the differentiationhindered quasi-number (Gr) is defined to clarify the influence mechanism of various mechanical factors on gravity differentiation and the difficulty of oil and gas replacement. When Gr is equal to 1, the oil−gas interface reaches stable migration conditions. Larger formation dip angle, higher permeability, smaller oil viscosity, and lower gas injection rate are the favorable conditions for forming stable flow. The findings are recommended to be used in reservoirs with relatively homogeneous reservoirs, certain dip angles, and moderate or low oil viscosity.

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“…Oil development efficiency in ultra-low-permeability sandstone reservoirs is typically inadequate due to poor physical properties, such as the strong water sensitivity, intense micro heterogeneity and ultra-low permeability [1][2][3]. Low oil recovery ratio and high water cut are always evident during water flooding.…”

Section: Introductionmentioning

confidence: 99%

Investigation on the Injection Pattern of Intermittent Natural Gas Flooding in Ultra-Low Permeability Reservoirs

Dong

et al. 2022

Processes

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Natural gas is a viable oil displacement agent in ultra-low-permeability reservoirs due to its good fluidity. It can also cause gas channeling during continuous injection, which limits its oilfield application. In order to relieve gas channeling during natural gas flooding, the injection mode should be changed. The use of intermittent natural gas injection (IGI) after the continuous natural gas injection in an ultra-low-permeability reservoir is proposed, and optimization of the injection parameters is discussed. The results show that IGI can be divided into three stages, the gas injection stage, the well shutting stage and the oil production stage. With the increase in injection time, the oil recovery enhances obviously as a result of IGI because the gas fingering can be controlled at the well shutting stage, and the gas/liquid ratio grows slowly because the gas breakthrough can be reduced at the oil production stage. The oil recovery improves with the increase in cycle time of IGI, while the increase rate reduces evidently after the cycle time reaches 360 min. The oil recovery increment is low if the cycle index exceeds 3 in the ultra-low-permeability reservoir. Thus, the optimal cycle time for each round and the appropriate cycle index of IGI are 360 min and three rounds.

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An improved system for evaluating the adaptability of natural gas flooding in enhancing oil recovery considering the miscible ability

Cited by 27 publications

References 29 publications

Effects of Wettability and Minerals on Residual Oil Distributions Based on Digital Rock and Machine Learning

Effects of Wettability and Minerals on Residual Oil Distributions Based on Digital Rock and Machine Learning

Establishment of Stability Evaluation Criteria for the Oil–Gas Interface during Gas-Cap Gravity Flooding in Oil Reservoirs with Strong Edge-Water Drive

Investigation on the Injection Pattern of Intermittent Natural Gas Flooding in Ultra-Low Permeability Reservoirs

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