Production prediction method of horizontal wells in tight gas reservoirs considering threshold pressure gradient and stress sensitivity

Ning, Bo; Xiang, Zhengrong; Liu, Xianshan; Li, Zhijun; Chen, Zhonghua; Jiang, Bocai; Zhao, Xiuyang; Tang, Huan; Xiaolong, Chang

doi:10.1016/j.petrol.2019.106750

Cited by 31 publications

(16 citation statements)

References 13 publications

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“…In tight gas reservoirs, the radius of the fluid flow channel is small, and the water films at narrow pore throats generate a large flow resistance, even potentially forming a water blockage in the gas–water flow channel. − The gas needs to overcome the capillary resistance to break through the water blockage, and then the gas can start to flow through the pore throat during CO 2 injection. , The threshold pressure effect appears during the gas–water transport in tight rock. , The smaller pore-throat size leads to a larger capillary resistance. The water distribution in the rock is mainly controlled by the pore-throat microstructure; consequently, the rock pore-throat microstructure has a significant impact on the threshold pressure. , …”

Section: Introductionmentioning

confidence: 99%

“…10,11 The threshold pressure effect appears during the gas−water transport in tight rock. 12,13 The smaller pore-throat size leads to a larger capillary resistance. The water distribution in the rock is mainly controlled by the pore-throat microstructure; consequently, the rock pore-throat microstructure has a significant impact on the threshold pressure.…”

Section: ■ Introductionmentioning

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: Introductionmentioning

confidence: 99%

Section: ■ Introductionmentioning

confidence: 99%

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

et al. 2022

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“…changed by changing the stress loaded on the rubber sleeve of the core holder to achieve a change in the solid source conduction stress in order to change the effective net stress [37]. In the variable fluid pressure experiment method, the stress is changed by fixing the confining pressure and changing the fluid pressure.…”

Section: Hard Spring Soft Springmentioning

confidence: 99%

Influence of Microcracks on Stress Sensitivity in Tight Sandstone

Zhang

et al. 2021

Lithosphere

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Stress sensitivity occurs throughout the reservoir development process, especially in the study of low permeability tight reservoir, considering the influence of stress sensitivity is particularly important. When studying stress sensitivity, the current main experimental methods are variable confining pressure and variable fluid pressure methods, but they cannot simulate the stress sensitivity during water injection development. Therefore, in this paper, an experimental stress sensitivity method that can be used to study the depletion mining and water injection development processes is established. In addition, the influence of different degrees of microcrack development on the stress sensitivity of the reservoir is investigated. The results of this study show that under the experimental conditions described in this article, the loading of axial compression plays a role of preloading stress and realizes the whole process of stress sensitivity under the condition that the fluid pressure is lower than the confining pressure. In the experiment, the permeability growth rate of matrix cores does not exceed 20%. For cores containing microcracks, when the axial pressure was less than 30 MPa, the permeability slowly increased with increasing fluid pressure. When the axial pressure was 30 MPa, the permeability changes are mainly divided into two stages. In the first stage, the microcracks are closed under compressive stress. At this time, the microcracks have a limited impact on the seepage capacity. The permeability increases slowly with increasing fluid pressure. In the second stage, the permeability rapidly increases after the microcracks open. These two stages can be described by two straight lines. The slope of the first line has nothing to do with the development of microcracks; the higher the degree of microcrack development, the greater the slope of the straight line of the second stage. For all of the cores, the permeability decreases as the axial pressure increases.

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“…The TPG is considered to be a fixed value, and this value is measured at a low effective stress. 24 The predicted threshold pressure with distance is linear according to this value, which inevitably leads to an underestimated calculated gas production loss. Consequently, the predicted gas production is overestimated, resulting in the actual production deviating from the expected development schedule.…”

Section: ■ Introductionmentioning

confidence: 99%

“…Existing gas well production formulae have been established using the magnitude of the threshold pressure without taking into account its dynamic nature. The TPG is considered to be a fixed value, and this value is measured at a low effective stress . The predicted threshold pressure with distance is linear according to this value, which inevitably leads to an underestimated calculated gas production loss.…”

Section: Introductionmentioning

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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Production prediction method of horizontal wells in tight gas reservoirs considering threshold pressure gradient and stress sensitivity

Cited by 31 publications

References 13 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

Influence of Microcracks on Stress Sensitivity in Tight Sandstone

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

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Production prediction method of horizontal wells in tight gas reservoirs considering threshold pressure gradient and stress sensitivity

Cited by 31 publications

References 13 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

Influence of Microcracks on Stress Sensitivity in Tight Sandstone

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

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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