Experimental investigation on the coupled effect of effective stress and gas slippage on the permeability of shale

Yang, Diansen; Wang, Wei; Chen, Weizhong; Wang, Shugang; Wang, Xiaoqiong

doi:10.1038/srep44696

Cited by 31 publications

(19 citation statements)

References 33 publications

(54 reference statements)

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“…In Darcy flow, the collision between molecules and pore walls is negligible, and the flow velocity of the liquid is approximated as zero on the pore walls. However, the additional flux due to gas flow at the wall surfaces effectively increases as the pore radius approaches the mean free path of the gas molecules [2,29]. This effect is expressed as follows:…”

Section: Resultsmentioning

confidence: 99%

“…The transport properties of rocks are of significant importance for many topics of earth sciences, for example, exploration and production of hydrocarbons, oil/gas storage in deep cavern, and high-level radioactive nuclear waste geological disposal [1][2][3][4]; they are also vital to understand the fundamental geologic processes such as heat and mass transfer, earthquake, and metamorphism [5][6][7][8][9]. Permeability is a key parameter to describe the transport properties of materials and it can be measured using different methods, for example, steady method and pulse-test [10].…”

Section: Introductionmentioning

confidence: 99%

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Investigating the Permeability of Marble under Moderate Pressure and Temperature

et al. 2017

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The permeability of intact marble samples collected from the depth of 1.6 km in southwestern China is investigated under moderate confining pressures and temperatures. No microcracks initiate or propagate during the tests, and the variation of permeability is due to the change of aperture of microcracks. Test results show a considerable decrease of permeability along with confining pressure increase from 10 to 30 MPa and temperature increase from 15 to 40 ∘ C. The thermal effect on the permeability is notable in comparison with the influence of the stress. A simple permeability evolution law is developed to correlate the permeability and the porosity in the compressive regime based on the microphysical geometric linkage model. Using this law, the permeability in the compressive regime for crystalline rock can be predicted from the volumetric strain curve of mechanical tests.

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Section: Resultsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Investigating the Permeability of Marble under Moderate Pressure and Temperature

et al. 2017

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“…Permeability is an important parameter for the gas flow especially in the coal reservoir;016. During the hydraulic flushing process, the permeability evolution in the coal mass is closely related to its stress state.…”

Section: Gas Extraction Modelmentioning

confidence: 99%

Hydraulic flushing in soft coal sublayer: Gas extraction enhancement mechanism and field application

Zhang

Wang

Yuan

et al. 2019

Energy Science & Engineering

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In China, one or several ultrathin soft coal sublayers are widely developed in the coal seam. Therefore, a method of using hydraulic flushing in soft sublayer to enhance the gas extraction in these particular coal seams is developed in this work. We first established a new fully coupled gas extraction model by combing gas diffusion, gas flow, and a permeability model that considers the effect of stress change and plastic failure. By adopting this model, the gas extraction enhancement mechanism and its main influence factors were studied using the numerical simulation method based on the engineering and geological background in the Yangquan No.5 coalmine. Thereafter, a hydraulic flushing equipment, which could move freely in the underground coalmine, was developed to apply the hydraulic flushing method in soft coal sublayers used in the 8402 working face. Its gas extraction effect was systematically investigated. Our simulation results match well with the field results, suggesting that our model is feasible. Meanwhile, after adopting this method, the gas extraction condition in this coalmine improves significantly. The borehole number decreases by 66.7%, while the gas extraction rate and gas extraction concentration increase by 1.33 times and 3 times, respectively. Moreover, during the coal mining process, the gas adsorption index of drilling cuttings, the quantity of drilling cuttings, and the CH4 concentration also decrease dramatically.

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“…Although, increasing gas pressure during injection reduces gas slip-flow effect, it also decreases the effective stress, which in turn influences the permeability. Yang et al [60] conducted laboratory experiments to investigate the coupled effect of both slip-flow effect and effective stress and found that the apparent permeability is greatly controlled by these two competing effects. Moreover, according to Vishal et al [40] and Jasinge et al [36], CO 2 permeability in coal exhibits an exponentially reducing trend with the effective stress applied on it (Figure 12).…”

Section: Effective Stressmentioning

confidence: 99%

A Comprehensive Overview of CO2 Flow Behaviour in Deep Coal Seams

Perera

2018

Energies

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Although enhanced coal bed methane recovery (ECBM) and CO 2 sequestration are effective approaches for achieving lower and safer CO 2 levels in the atmosphere, the effectiveness of CO 2 storage is greatly influenced by the flow ability of the injected CO 2 through the coal seam. A precious understanding of CO 2 flow behaviour is necessary due to various complexities generated in coal seams upon CO 2 injection. This paper aims to provide a comprehensive overview on the CO 2 flow behaviour in deep coal seams, specifically addressing the permeability alterations associated with different in situ conditions. The low permeability nature of natural coal seams has a significant impact on the CO 2 sequestration process. One of the major causative factors for this low permeability nature is the high effective stresses applying on them, which reduces the pore space available for fluid movement with giving negative impact on the flow capability. Further, deep coal seams are often water saturated where, the moisture behave as barriers for fluid movement and thus reduce the seam permeability. Although the high temperatures existing at deep seams cause thermal expansion in the coal matrix, reducing their permeability, extremely high temperatures may create thermal cracks, resulting permeability enhancements. Deep coal seams preferable for CO 2 sequestration generally are high-rank coal, as they have been subjected to greater pressure and temperature variations over a long period of time, which confirm the low permeability nature of such seams. The resulting extremely low CO 2 permeability nature creates serious issues in large-scale CO 2 sequestration/ECBM projects, as critically high injection pressures are required to achieve sufficient CO 2 injection into the coal seam. The situation becomes worse when CO 2 is injected into such coal seams, because CO 2 movement in the coal seam creates a significant influence on the natural permeability of the seams through CO 2 adsorption-induced swelling and hydrocarbon mobilisation. With regard to the temperature, the combined effects of the generation of thermal cracks, thermal expansion, adsorption behaviour alterations and the associated phase transition must be considered before coming to a final conclusion. A reduction in coal's CO 2 permeability with increasing CO 2 pressure may occur due to swelling and slip-flow effects, both of which are influenced by the phase transition in CO 2 from subto super-critical in deep seams. To date, many models have been proposed to simulate CO 2 movement in coal considering various factors, including porosity, effective stress, and swelling/shrinkage. These models have been extremely useful to predict CO 2 injectability into coal seams prior to field projects and have therefore assisted in implementing number of successful CO 2 sequestration/ECBM projects.

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Experimental investigation on the coupled effect of effective stress and gas slippage on the permeability of shale

Cited by 31 publications

References 33 publications

Investigating the Permeability of Marble under Moderate Pressure and Temperature

Investigating the Permeability of Marble under Moderate Pressure and Temperature

Hydraulic flushing in soft coal sublayer: Gas extraction enhancement mechanism and field application

A Comprehensive Overview of CO2 Flow Behaviour in Deep Coal Seams

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