Compaction, permeability evolution and stress path effects in unconsolidated sand and weakly consolidated sandstone

Nguyễn, Văn Hùng; Gland, N.; Dautriat, Jérémie; David, Christian; Wassermann, J.; Guélard, Jean

doi:10.1016/j.ijrmms.2013.07.001

Cited by 60 publications

(50 citation statements)

References 30 publications

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“…It indicates that the shale rock elastic modulus is not only affected by the confining stress value but also by the stress history path. This observation of elastic modulus's dependence on both stress history path and in-situ stress state is an extension of previous observations that permeability is dependent on both in-situ stress state and reservoir stress history path [31]. Based on Equations (6) and (7), greater strain change leads to greater permeability decrease.…”

Section: Elastic Modulus Alterationsupporting

confidence: 79%

A Study of Nonlinear Elasticity Effects on Permeability of Stress Sensitive Shale Rocks Using an Improved Coupled Flow and Geomechanics Model: A Case Study of the Longmaxi Shale in China

Wei

Wang²,

et al. 2018

Energies

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Gas transport in shale gas reservoirs is largely affected by rock properties such as permeability. These properties are often sensitive to the in-situ stress state changes. Accurate modeling of shale gas transport in shale reservoir rocks considering the stress sensitive effects on rock petrophysical properties is important for successful shale gas extraction. Nonlinear elasticity in stress sensitive reservoir rocks depicts the nonlinear stress-strain relationship, yet it is not thoroughly studied in previous reservoir modeling works. In this study, an improved coupled flow and geomechanics model that considers nonlinear elasticity is proposed. The model is based on finite element methods, and the nonlinear elasticity in the model is validated with experimental data on shale samples selected from the Longmaxi Formation in Sichuan Basin China. Numerical results indicate that, in stress sensitive shale rocks, nonlinear elasticity affects shale permeability, shale porosity, and distributions of effective stress and pore pressure. Elastic modulus change is dependent on not only in-situ stress state but also stress history path. Without considering nonlinear elasticity, the modeling of shale rock permeability in Longmaxi Formation can overestimate permeability values by 1.6 to 53 times.

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Section: Elastic Modulus Alterationsupporting

confidence: 79%

A Study of Nonlinear Elasticity Effects on Permeability of Stress Sensitive Shale Rocks Using an Improved Coupled Flow and Geomechanics Model: A Case Study of the Longmaxi Shale in China

Wei

Wang²,

et al. 2018

Energies

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“…(a) Failure envelope for the water‐saturated Sherwood sandstone: the experimental data (open squares) from Nguyen et al . [] can be modeled using the cap model (solid and dashed brown lines) of Wong et al . [].…”

Section: Discussionmentioning

confidence: 92%

“…To assess a potential role of effective pressure variation on the sample failure, we use the failure envelope obtained by Nguyen et al . [] for the water‐saturated Sherwood sandstone, which can be fitted by the cap model of Wong et al . [] (Figure a).…”

Section: Discussionmentioning

confidence: 99%

“…The failure stress for TRX‐w is in good agreement with the data reported by Nguyen et al . []: for the sake of simplicity the failure envelope at low mean effective stress can be approximated by a straight line obtained by the least squares best fit on the three data points available for the water‐saturated Sherwood sandstone (Figure a). We assume that a straight line with equal slope but different intercept (i.e., pore fluid‐dependent cohesion) is also a good approximation for the failure envelope of the dry and oil‐saturated Sherwood sandstone (Figure b).…”

Section: Discussionmentioning

confidence: 99%

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Mechanical instability induced by water weakening in laboratory fluid injection tests

David¹,

Dautriat

Sarout

et al. 2015

JGR Solid Earth

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To assess water‐weakening effects in reservoir rocks, previous experimental studies have focused on changes in the failure envelopes derived from mechanical tests conducted on rocks fully saturated either with water or with inert fluids. So far, little attention has been paid to the mechanical behavior during fluid injection under conditions similar to enhanced oil recovery operations. We studied the effect of fluid injection on the mechanical behavior of the weakly consolidated Sherwood sandstone in laboratory experiments. Our specimens were instrumented with 16 ultrasonic P wave transducers for both passive and active acoustic monitoring during loading and fluid injection to record the acoustic signature of fluid migration in the pore space and the development of damage. Calibration triaxial tests were conducted on three samples saturated with air, water, or oil. In a second series of experiments, water and inert oil were injected into samples critically loaded up to 80% or 70% of the dry or oil‐saturated compressive strength, respectively, to assess the impact of fluid migration on mechanical strength and elastic properties. The fluids were injected with a low back pressure to minimize effective stress variations during injection. Our observations show that creep takes place with a much higher strain rate for water injection compared to oil injection. The most remarkable difference is that water injection in both dry and oil‐saturated samples triggers mechanical instability (macroscopic failure) within half an hour whereas oil injection does not after several hours. The analysis of X‐ray computed tomography images of postmortem samples revealed that the mechanical instability was probably linked to loss of cohesion in the water‐invaded region.

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“…In a recent review of mechanical compaction behaviors in 10 sandstones (with porosities ranging from 13% to 35%), Wong and Baud [] concluded that they all have elliptical caps, Bleurswiller sandstone being the sole exception. Elliptical caps were also documented in recent studies of poorly lithified sandstone and sand [ Skurtveit et al ., ; Nguyen et al ., ].…”

Section: Discussionmentioning

confidence: 99%

Mechanical compaction and strain localization in Bleurswiller sandstone

Baud

Reuschlé

et al. 2015

JGR Solid Earth

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We performed a systematic investigation of mechanical compaction and strain localization in Bleurswiller sandstone. Our data show that the effective pressure principle can be applied in both the brittle faulting and cataclastic flow regimes, with an effective pressure coefficient close to but somewhat less than 1. Under relatively high confinement, the samples typically fail by development of compaction bands. X‐ray computed tomography (CT) was used to resolve preexisting porosity clusters, as well as the initiation and propagation of the compaction bands in deformed samples. Synthesis of the CT and microstructural data indicates that there is no casual relation between collapse of the porosity clusters in Bleurswiller sandstone and nucleation of the compaction bands. Instead, the collapsed porosity clusters may represent barriers for the propagation of compaction localization, rendering the compaction bands to propagate along relatively tortuous paths so as to avoid the porosity clusters. The diffuse and tortuous geometry of compaction bands results in permeability reduction that is significantly lower than that associated with compaction band formation in other porous sandstones. Our new data confirm that Bleurswiller sandstone stands out as the only porous sandstone associated with a compactive cap that is linear, and our CT and microstructural observation show that it is intimately related to collapse of the porosity clusters. We demonstrate that the anomalous linear caps and their slopes are in agreement with a micromechanical model based on the collapse of a spherical pore embedded in an elastic‐plastic matrix that obeys the Coulomb failure criterion.

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Compaction, permeability evolution and stress path effects in unconsolidated sand and weakly consolidated sandstone

Cited by 60 publications

References 30 publications

A Study of Nonlinear Elasticity Effects on Permeability of Stress Sensitive Shale Rocks Using an Improved Coupled Flow and Geomechanics Model: A Case Study of the Longmaxi Shale in China

A Study of Nonlinear Elasticity Effects on Permeability of Stress Sensitive Shale Rocks Using an Improved Coupled Flow and Geomechanics Model: A Case Study of the Longmaxi Shale in China

Mechanical instability induced by water weakening in laboratory fluid injection tests

Mechanical compaction and strain localization in Bleurswiller sandstone

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