Variation in horizontal stress with pore pressure depletion in coal under uniaxial strain conditions: An update on the modelling of laboratory data

Shi, Ji‐Quan; Durucan, Şevket

doi:10.1016/j.coal.2018.01.009

Cited by 6 publications

(2 citation statements)

References 10 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…As shown in Figure 4, the proposed model can reproduce appropriately both the horizontal stress and the permeability. The deviation of the predicted horizontal stress for the lowest two pressure points (when P is less than 1.4 MPa) can be explained by the reduction in Young's modulus at low pore pressure Shi and Durucan, 2018).…”

Section: Model Validationmentioning

confidence: 95%

Permeability changes in coal seams: The role of anisotropy

Wang

Vandamme

Pereira

et al. 2018

International Journal of Coal Geology

View full text Add to dashboard Cite

The permeability of coal seams is pore pressure-dependent. A number of analytical models have been proposed to investigate this problem, but many disregard a crucial factor: the anisotropy of coal. This paper is devoted to investigating the role of anisotropy in modeling the change of horizontal permeability with pressure. Analysis is conducted using a fully anisotropic model that incorporates both the anisotropies of mechanical properties and of the permeability dependence on stresses. Analytical expressions of the pressure-permeability relationship are derived in oedometric and isochoric geomechanical conditions, and validations are conducted against both laboratory and field data. Then, the roles of the anisotropy of stiffness and of permeability dependence on stresses in the permeability-change model are explored. We demonstrate that the mechanical anisotropy can be simplified to an isotropic model without introducing significant errors in prediction of pressure-permeability relationship, while neglecting the anisotropy of permeability dependence on stresses leads to considerable errors. When both anisotropy sources are disregarded, the pressure-permeability curve can be exactly reproduced by a totally isotropic material in both oedometric and isotropic conditions. However, the material properties (e.g., bulk modulus) are skewed; moreover, such an equivalent material might lead to significant errors in other geomechanical conditions. Finally, the permeability change is investigated at the reservoir scale, and the reservoir simulation results confirm the conclusions obtained from the analytical analysis.coalbeds are conferred unique poromechanical properties by their two-scale porosity systems: macro-porosity and micro-porosity (Espinoza et al., 2014;Nikoosokhan et al., 2014). The macro-pores in coalbeds are commonly constituted by cleats, that are, natural fractures developed during diagenetic processes (Laubach et al., 1998). The cleats act as the major channel for methane to flow and thus govern the permeability of fractured coal seams. Between cleats, one finds a microporous organic continuum, routinely called as coal matrix. Methane is stored inside the micro-pores of coal matrix. In the micro-pores (typically sized in the order of 10 −9 to 10 −8 m), all fluid molecules interact with the atoms of solid matrix; they are therefore not in their bulk state as in the macro-pores but are in adsorbed state (Vandamme et al., 2010;Brochard et al., 2012). The adsorbed state of methane in micro-pores governs the adsorption/desorption phenomena and subsequent swelling/shrinking of coal matrix (Pan and Connell, 2007;Day et al., 2008).The permeability of fractured CBM reservoirs changes with depletion during production, and this process plays an important role during production and enhanced recovery operations. The permeability change with depletion (i.e., decrease of pore pressure) mainly stems from two mechanisms with opposing effects. The first mechanism involves the mechanical deformation due to pressure changes: w...

show abstract

Section: Model Validationmentioning

confidence: 95%

Permeability changes in coal seams: The role of anisotropy

Wang

Vandamme

Pereira

et al. 2018

International Journal of Coal Geology

View full text Add to dashboard Cite

show abstract

“…Coal failure during coalbed methane production has received a lot of attention from researchers, whereas coal failure during CO 2 -ECBM has received less attention. Shi and Durucan [6] initially estimated the effective stress change during depletion using an analogy between thermal contraction and gas desorption-induced matrix shrinkage, and experimental data demonstrate excellent agreement [7]. Liu and Harpalani [8] provided an experimental investigation of the horizontal stress variations, and discovered that in addition to the poroelastic effect seen in conventional reservoirs, sorption-induced shrinkage also alters in-situ stress and increases coal failure potential.…”

Section: Introductionmentioning

confidence: 98%

Critical Conditions for Wellbore Failure during CO2-ECBM Considering Sorption Stress

Xiao

Wang

et al. 2023

Sustainability

View full text Add to dashboard Cite

Significant stress changes caused by sorption-induced swelling raise the coal wellbore failure potential, which directly impacts the safety and sustainability of CO2 enhanced coalbed methane (CO2-ECBM). Additionally, a mixture gas (CO2/N2) injection is recommended due to the sharp decline of permeability with pure CO2 injection. In this study, incorporating the impacts of mixture gas adsorption and poroelastic effects, a semi-analytical model of coal wellbore stability during mixture gas injection is proposed. Model results indicate that the stress field is significantly influenced by the boundary condition and sorption effect. In addition, parametric studies are performed to determine the influence of adsorption parameters, mechanical properties, and gas composition on the stress distribution and then on the wellbore failure index. Furthermore, mixture gas injection with a large proportion of CO2 or N2 both cause wellbore instability. Significant compressive hoop stress and shear failure are caused by the mixture gas injection with a large proportion of CO2. In contrast, the displacement of CH4 with weakly adsorptive N2 will result in less compressive and shear or tensile failure, which occurs near the wellbore. Thus, mixture gas (including pure CO2/N2) injection must be controlled by coal wellbore failure, providing an accurate estimation of in-situ coal seams’ CO2 storage capacity from the perspective of wellbore stability.

show abstract