Determination of gas-water seepage characteristics with consideration of dynamic pore-throat structure in a tight sandstone gas formation

Liu, Guangfeng; Wang, Yifeng; Yin, Handong; Ding, Yaping; Lan, Yifei; Yang, Daoyong

doi:10.1016/j.marpetgeo.2021.105440

Cited by 4 publications

(3 citation statements)

References 53 publications

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“…The size of the pore throat completely filled with water decreases as the effective stress increases, and the capillary resistance that CO 2 needs to overcome to drive the water becomes larger . Moreover, the water films on the walls of some pores and throats merge with each other as a result of the reduced radius of pore throats, such that these pore throats are filled with water and can be considered to be blocked by water blockages . The development of water blockages makes the connectivity between the pores and throats worse, further increasing the threshold pressure.…”

Section: Resultsmentioning

confidence: 99%

“…17 Moreover, the water films on the walls of some pores and throats merge with each other as a result of the reduced radius of pore throats, such that these pore throats are filled with water and can be considered to be blocked by water blockages. 37 The development of water blockages makes the connectivity between the pores and throats worse, further increasing the threshold pressure.…”

Section: ■ Research Methodsmentioning

confidence: 99%

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Quantifying Controls on Threshold Pressure during CO₂ Injection in Tight Gas Reservoir Rocks

et al. 2022

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The simultaneous flow of gas and water is controlled by a threshold pressure gradient (TPG) effect during CO 2 injection of tight gas reservoirs. The TPG effect is dynamic because it varies with both the effective stress and the water saturation. The sensitivity of TPG to effective stress and mobile water is affected by the porethroat microstructure. In this paper, we report the results of dynamic TPG tests on six cores with similar permeability. The influence of the pore-throat microstructure on the sensitivity of the TPG to stress and to mobile water was also quantitatively studied using a fractal method, and the distribution of the threshold pressure and corresponding gas production loss were calculated during CO 2 injection in tight gas reservoirs. The test results show that TPG decreases logarithmically with the increase of the pore fluid pressure during CO 2 injection, a change of 0.1−50 MPa in the pore fluid pressure corresponding to a 1.8−3.5 times increase of the TPG variation. The TPG increases exponentially by 3.5−6.7 times from irreducible water saturation to a mobile water saturation of 30%. The fractal dimension (D) of the heterogeneity of the rock pore-throat microstructure has a linear relationship with both the stress sensitivity coefficient (λ) and mobile water sensitivity coefficient (η), with the larger values of λ and η being associated with more heterogeneous pore-throat microstructures. The reservoir threshold pressure showed a significant nonlinear distribution in near-well reservoirs at low bottom-hole flow pressures of the production well during CO 2 injection. The calculated gas well production loss as a result of a dynamic threshold pressure is 7−16% higher than that of the fixed threshold pressure, and the difference is larger at low pressures.

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Section: Resultsmentioning

confidence: 99%

Section: ■ Research Methodsmentioning

confidence: 99%

Quantifying Controls on Threshold Pressure during CO₂ Injection in Tight Gas Reservoir Rocks

et al. 2022

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“…This is similar to the sensitivity of DTPG to effective stress because rocks with low permeability have small pore throats and complex pore throat structures. A small effective stress variation causes a large change in pore throat structure and also results in a large change in the water distribution . In this case, the DTPG shows a strong sensitivity to the effective stress.…”

Section: Resultsmentioning

confidence: 99%

Improving the Prediction of Production Loss in Heterogeneous Tight Gas Reservoirs Using Dynamic Threshold Pressure

et al. 2022

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Tight gas reservoirs commonly exhibit complex pore throat structures. Conventionally, a constant threshold pressure gradient (TPG) has been used to predict the production loss that arises from overcoming the rock's disinclination to flow water and gas through such complex pore throat structures. In this work, we find that the TPG is not constant during the production lifetime of a reservoir. The TPG varies significantly with both effective stress and water saturation, leading us to rename TPG as dynamic threshold pressure gradient (DTPG). In the first part of this paper, we examine the sensitivity of DTPG to stress and mobile water saturation for cores with different permeabilities, showing that DTPG increases logarithmically with effective stress from 0.17 to 0.5 MPa/m for a change in effective stress from 0.6 to 30.5 MPa. The DTPG also increases exponentially with mobile water saturation (S m ), which is 2.7−6.5 times higher at S m = 25% compared to the value at irreducible water saturation. The sensitivity of DTPG to both variables shows a decreasing power law trend with increasing rock permeability. These combined effects generally suggest that DTPG is larger than the conventional TPG. In the second part of this paper, we model the effects of using a variable DTPG in place of a constant TPG for the purpose of predicting the production loss associated with the latent pressure barrier in different heterogeneous reservoirs. When the interacting effects of effective stress, water saturation, and permeability are taken into account, we find that the threshold pressure is relatively small in heterogeneous reservoirs with a distribution of increasing permeability in the gas flow direction. The constant TPG approach underestimates the production loss by 34−45% with the greatest difference occurring at low gas pressures encountered at the production well, suggesting that gas production wells should be located in areas with high permeability.

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Performance evaluation of commingled production in a multilayer oil reservoir based on microscopic pore-throat structures

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Tian

Wang

et al. 2023

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Determination of gas-water seepage characteristics with consideration of dynamic pore-throat structure in a tight sandstone gas formation

Cited by 4 publications

References 53 publications

Quantifying Controls on Threshold Pressure during CO₂ Injection in Tight Gas Reservoir Rocks

Quantifying Controls on Threshold Pressure during CO₂ Injection in Tight Gas Reservoir Rocks

Improving the Prediction of Production Loss in Heterogeneous Tight Gas Reservoirs Using Dynamic Threshold Pressure

Performance evaluation of commingled production in a multilayer oil reservoir based on microscopic pore-throat structures

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Determination of gas-water seepage characteristics with consideration of dynamic pore-throat structure in a tight sandstone gas formation

Cited by 4 publications

References 53 publications

Quantifying Controls on Threshold Pressure during CO2 Injection in Tight Gas Reservoir Rocks

Quantifying Controls on Threshold Pressure during CO2 Injection in Tight Gas Reservoir Rocks

Improving the Prediction of Production Loss in Heterogeneous Tight Gas Reservoirs Using Dynamic Threshold Pressure

Performance evaluation of commingled production in a multilayer oil reservoir based on microscopic pore-throat structures

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Quantifying Controls on Threshold Pressure during CO₂ Injection in Tight Gas Reservoir Rocks

Quantifying Controls on Threshold Pressure during CO₂ Injection in Tight Gas Reservoir Rocks