Mechanism model for shale gas transport considering diffusion, adsorption/desorption and Darcy flow

Wei, Mingqiang; Duan, Yonggang; Fang, Quantang; Wang, Rong; Yu, Benhai; Yu, Chunsheng

doi:10.1007/s11771-013-1692-7

Cited by 11 publications

(4 citation statements)

References 5 publications

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“…With the increasing demand for the world economy, the development of unconventional shale gas resource has attracted extensive attention worldwide, which has gradually become the strategic supplemental of conventional oil and gas resources Tokunaga et al, 2017). Shale gas is a kind of unconventional natural gas that is adsorbed, free or dissolved within the pores of shale rocks (Wei et al, 2013;. Compared with conventional gas reservoirs, shale gas reservoirs are characterized by low porosity and ultra-low permeability, so horizontal drilling and hydraulic fracturing are the key technologies to produce gas from shale gas reservoirs (Cheng, 2012;Xu et al, 2015;Shen et al, 2016;Wei et al, 2016).…”

Section: Introductionmentioning

confidence: 99%

Experimental and numerical simulation of water adsorption and diffusion in shale gas reservoir rocks

Shen

Cihan

et al. 2019

Adv. Geo-Energy Res.

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Despite the success of deep horizontal drilling and hydraulic fracturing in yielding large production increases from unconventional shale gas reservoirs, uncertainties associated with basic transport processes require understanding in order to improve efficiency and minimize environmental impacts. The hydraulic fracturing process introduces large volumes of water into shale gas reservoirs, most of which remains unrecoverable and interferes with gas production. In this study, the water adsorption and diffusion measurements of the Longmaxi Formation shale were conducted at 30 • C and 50 • C for relative humidities from 11.1% to 97.0%. Based on the experiment, a computational model based on the Maxwell-Stefan diffusion equation was constructed to analyze water adsorption and diffusion in shale rocks, and the Guggenheim-Anderson-de Boer (GAB) isotherm for gas adsorption was included in the model. The results show that water adsorption isotherms of shales belong to type II curve, including the monolayer, multilayer adsorption and capillary condensation, and the GAB model can be used to describe the water adsorption process in shale rocks. With the increasing of relative pressure, the water adsorption of shale increases, and the organic carbon content and temperature strengthen the water adsorption in shale. The capillary pressure can reach the order of several hundreds of MPa after the hydraulic fracturing process, and it results in a large amount of fracturing fluid retained in shale gas reservoirs. Furthermore, the simulation of water adsorption and diffusion in shale rocks is less than the experimental value, which further indicates that capillary condensation occurs in shale rocks.

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Section: Introductionmentioning

confidence: 99%

Experimental and numerical simulation of water adsorption and diffusion in shale gas reservoir rocks

Shen

Cihan

et al. 2019

Adv. Geo-Energy Res.

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“…Shale is a fragile rock formed by the deposition of clay materials at the specific pressure and temperature, which has a complex mineral composition, apparent bedding structures, and varying degrees of anisotropy (Shen et al., 2015; Wei et al., 2013). Due to the unique storage and low permeability characteristics of shale gas reservoirs, horizontal drilling and hydraulic fracturing are the two key technologies for the successful development (Li et al., 2015; Shen et al., 2016; Zhu and Qi, 2016).…”

Section: Introductionmentioning

confidence: 99%

Study on mechanical characteristics and damage mechanism of the Longmaxi Formation shale in southern Sichuan Basin, China

Guo

Shen

et al. 2019

Energy Exploration & Exploitation

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During the development of shale gas reservoirs, the mechanical parameters of shale rocks are greatly significant to guide reservoir drilling design, reservoir stimulation, scheme design, and wellbore stability evaluation. Compared with conventional gas reservoirs, the mechanical properties of shale gas reservoir are more complex and lack of the comprehensive understanding. In this study, the uniaxial and triaxial compression experiments of the Longmaxi shale in South China were conducted to understand the mechanical characteristics and damage mechanism of shale rocks. Combined with the characteristics of shale microstructure, the effects of the mechanical properties such as mineral composition, deformation, stress–strain, and fracture damage characteristics were analyzed and discussed. The results show that the stress–strain curves of shale are two main types of elastic deformation and elastic–plastic deformation. There is a significant difference in effective pressure of yield platform in different shale post-peak deformation. The effective pressure of rigid shale is 60 MPa while that of other shales is 30 MPa. With the increase of effective pressure, the increase of peak compressive strength decreases gradually, and the effect of effective pressure on compressive strength decreases gradually with the transition from the brittleness to the ductility. The higher the effective pressure of the brittleness to the ductility is, the greater the change of compressive strength with effective pressure is, and the smaller the compressive strength under low effective pressure is, the smaller the variation with pressure is. Shale rocks with relatively high brittleness under different effective pressures are mainly characterized by brittle split fracture dominated by tensile fracture, while other shales with low brittleness are dominated by single shear fracture plane.

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“…Besides, the extended Langmuir model (ELM) is also included in EOS7C-ECBM for adsorption and desorption of gases (Webb 2011). Although there are a few studies about methane gas diffusion in shale gas reservoirs (Wei et al 2013), the gas flow transport in shale rocks has not been fully understood. Therefore, there is a necessity to understand methane diffusion and adsorption in shale and the effects of the problem so as to optimize gas productivity in shale gas reservoirs.…”

Section: Introductionmentioning

confidence: 99%

Methane Diffusion and Adsorption in Shale Rocks: A Numerical Study Using the Dusty Gas Model in TOUGH2/EOS7C-ECBM

et al. 2018

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Gas production from shale gas reservoirs plays a significant role in satisfying increasing energy demands. Compared with conventional sandstone and carbonate reservoirs, shale gas reservoirs are characterized by extremely low porosity, ultra-low permeability and high clay content. Slip flow, diffusion, adsorption and desorption are the primary gas transport processes in shale matrix, while Darcy flow is restricted to fractures. Understanding methane diffusion and adsorption, and gas flow and equilibrium in the low-permeability matrix of shale is crucial for shale formation evaluation and for predicting gas production. Modeling of diffusion in low-permeability shale rocks requires use of the Dusty gas model (DGM) rather than Fick's law. The DGM is incorporated in the TOUGH2 module EOS7C-ECBM, a modified version of EOS7C that simulates multicomponent gas mixture transport in porous media. Also included in EOS7C-ECBM is the extended Langmuir model for adsorption and desorption of gases. In this study, a column shale model was constructed to simulate methane diffusion and adsorption through shale rocks. The process of binary CH 4 −N 2 diffusion and adsorption was analyzed. A sensitivity study was performed to investigate the effects of pressure, temperature and permeability on diffusion and adsorption in shale rocks. The results show that methane gas diffusion and adsorption in shale is a slow process of dynamic equilibrium, which can be illustrated by the slope of a curve in CH 4 mass variation. The amount of adsorption increases with the pressure increase at the low pressure, and the mass change by gas diffusion will decrease due to the decrease in the compressibility factor of the gas. With the elevated temperature, the gas molecules move faster and then the greater gas diffusion rates make the process duration shorter. The gas diffusion rate decreases with the permeability decrease, and there is a limit of gas diffusion if the permeability is less than 1.0 × 10 −15 m 2 . The results can provide insights for a better understanding of methane diffusion and adsorption in the shale rocks so as to optimize gas production performance of shale gas reservoirs.

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Mechanism model for shale gas transport considering diffusion, adsorption/desorption and Darcy flow

Cited by 11 publications

References 5 publications

Experimental and numerical simulation of water adsorption and diffusion in shale gas reservoir rocks

Experimental and numerical simulation of water adsorption and diffusion in shale gas reservoir rocks

Study on mechanical characteristics and damage mechanism of the Longmaxi Formation shale in southern Sichuan Basin, China

Methane Diffusion and Adsorption in Shale Rocks: A Numerical Study Using the Dusty Gas Model in TOUGH2/EOS7C-ECBM

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