Effect of Rock Strength Criterion on the Predicted Onset of Sand Production

Based on the assumption that rock strength follows the log normal distribution statistically, this paper establishes a damage constitutive model of rock under uniaxial stress conditions in combination with the Mohr–Coulomb strength criterion and damage mechanical theory. Experiments were carried out to investigate the damage evolution process of rock material, which can be categorized into nondamaging, accelerated growth, constant-speed, similar growth, and speed-reducing growth stages. The evolution process had a good corresponding relationship with the rock stress-strain curves. Based on the statistical damage constitutive model proposed in this paper, a numerical fitting analysis was conducted on the uniaxial compression testing data of laboratory sand rock and on experimental data from other literature, in order to validate the rationality of the constitutive equation and the determination of its parameters and to analyze the effect of internal friction variables on damage variables and compression strength. The research outcomes presented in this paper can provide useful reference for the theory of rock mechanics and for rock engineering.

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Three-Dimensional Numerical Analysis of the Tunnel for Polyaxial State of Stress

Mathematical Problems in Engineering ◽

10.1155/2015/301241 ◽

2015 ◽

Vol 2015 ◽

pp. 1-8

Author(s):

Wenge Qiu ◽

Chao Kong ◽

Kai Liu

Keyword(s):

Numerical Simulation ◽

Mechanical Behavior ◽

Principal Stress ◽

Failure Criterion ◽

Rock Strength ◽

Strength Criterion ◽

Intermediate Principal Stress ◽

State Of Stress ◽

Coulomb Failure ◽

Coulomb Failure Criterion

The aim of this study is to have a comprehensive understanding of the mechanical behavior of rock masses around excavation under different value of intermediate principal stress. Numerical simulation was performed to investigate the influence of intermediate principal stress using a new polyaxial strength criterion which takes polyaxial state of stress into account. In order to equivalently substitute polyaxial failure criterion with Mohr-Coulomb failure criterion, a mathematical relationship was established between these two failure criteria. The influence of intermediate principal stress had been analyzed when Mohr-Coulomb strength criterion and polyaxial strength criterion were applied in the numerical simulation, respectively. Results indicate that intermediate principal stress has great influence on the mechanical behavior of rock masses; rock strength enhanced by intermediate principal stress is significant based on polyaxial strength criterion; the results of numerical simulation under Mohr-Coulomb failure criterion show that it does not exert a significant influence on rock strength. Results also indicate that when intermediate principal stress is relatively small, polyaxial strength criterion is not applicable.

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An experimental investigation on the effect of rock strength and perforation size on sand production

Journal of Petroleum Science and Engineering ◽

10.1016/j.petrol.2012.03.023 ◽

2012 ◽

Vol 86-87 ◽

pp. 172-189 ◽

Cited By ~ 22

Author(s):

Vahidoddin Fattahpour ◽

Mahdi Moosavi ◽

Mahdi Mehranpour

Keyword(s):

Experimental Investigation ◽

Rock Strength ◽

Sand Production

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Unification of Hoek-Brown Criterion on the Basis of United Strength Theory

Applied Mechanics and Materials ◽

10.4028/www.scientific.net/amm.501-504.415 ◽

2014 ◽

Vol 501-504 ◽

pp. 415-418

Author(s):

Yuan Li ◽

Qi Liang Liu ◽

Qing Chi Cai

Keyword(s):

Rock Mass ◽

Rock Strength ◽

Hard Rock ◽

Strength Criterion ◽

Strength Reduction ◽

Strength Theory ◽

Unified Strength Theory ◽

Rock Mass Strength ◽

Decomposition Formula ◽

Theory Formula

Based on twin failure mechanism of fracture and shear , the bilinear transitional strength decomposition formula reflecting the nonlinear strength of rock material is proposed,.The decomposed brittle shear formula is integrated and finally the unified strength theory formula characterized by nonlinearity of Hoek-Brown criterion is established. It makes the unified strength theory characterized by nonlinearity of empirical strength criterion, rock mass strength reduction, etc. Besides, it contributes to promote the accuracy and applicability of unified strength theory in rock strength and rock mass strength,especially for the hard rock failure analysis.

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Geomechanical model and sanding onset assessment: A field case study in Vietnam

Petrovietnam Journal ◽

10.47800/pvj.2021.10-04 ◽

2021 ◽

Vol 10 ◽

pp. 40-46

Author(s):

Văn Hùng Nguyễn ◽

Thị Thuỳ Linh Bùi

Keyword(s):

Rock Strength ◽

In Situ Stress ◽

Reservoir Pressure ◽

Sand Production ◽

Geomechanical Model ◽

Field Case ◽

Sand Control ◽

Maximum Drawdown

Sand production is a key issue when selecting and applying completion solutions like open holes, screens or perforated liners. This problem can be seen in several types of reservoirs such as weakly consolidated and non-consolidated carbonates. The paper presents a method to model wellbore failures for sanding prediction. Our study shows that the potential sand risk in this field is defined by the rock strength rather than the in-situ stress. If the rock is sufficiently competent, the potential of sand production is negligible, and the development wells can be completed conventionally without any downhole sand control for the reservoir pressure above 1,280 psi and the maximum drawdown pressure of 2,380 psi.

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Sand production assessment considering the reservoir geomechanics and water breakthrough

The APPEA Journal ◽

10.1071/aj14016 ◽

2015 ◽

Vol 55 (1) ◽

pp. 215 ◽

Cited By ~ 3

Author(s):

Sadegh Asadi ◽

Khalil Rahman ◽

Hoanh V. Pham ◽

Thao Le Minh ◽

Andy Butt

Keyword(s):

Rock Strength ◽

Development Planning ◽

Production Plan ◽

Reservoir Pressure ◽

Water Production ◽

Sand Production ◽

Future Production ◽

Sand Control ◽

Well Trajectory ◽

Bottomhole Pressure

Sand production assessment is essential from the early stages of field development planning for completion design and later for the production optimisation. Unconsolidated and weakly consolidated sandstones are prone to fail at a low flowing bottomhole pressure during hydrocarbon production. To predict the critical flowing bottomhole pressure or a safe drawdown, a geomechanical model that integrates in situ stresses, rock mechanical properties, the well trajectory, reservoir pressure, the production plan and the depletion trend is required. For a given stress field, well trajectory and production plan, the rock strength index is a key parameter that has significant impacts on the sanding risk. This paper presents the results of a study investigating the potential of sand production from primary and secondary target reservoir rocks in a petroleum field in offshore Vietnam. A poroelastic analytical approach was used to investigate if sands will be produced from the open holes or perforations. The criterion of sanding was formulated to be the effective maximum principal stress to be greater than the effective rock strength. Observations of sanding or no sanding during drill stem tests (DSTs) were used to calibrate the sanding model to be used for sanding predictions of future production wells. The effects of reservoir pressure depletion on sanding risks were investigated using the stress arching theory. Since the water production from target reservoirs was observed in the nearby fields, the analysis was performed to investigate the effects of water production on rock weakening that may cause higher risks of sanding. The results showed low risks of sanding for majority of the reservoirs, with drawdowns as high as 3,000 psi at the original reservoir pressure. The drawdown was, however, required to reduce to 500 psi to produce sand-free after depleting the reservoir by more than 90% of its original pressure. The results of this study led to the decision of completing the wells without using sand control equipment and to avoid sanding by controlling drawdown for the life of the well.

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Effect of Fluid Type and Multiphase Flow on Sand Production in Oil and Gas Wells

SPE Journal ◽

10.2118/187117-pa ◽

2018 ◽

Vol 24 (02) ◽

pp. 733-743

Author(s):

Haotian Wang ◽

Deepen P. Gala ◽

Mukul M. Sharma

Keyword(s):

Fluid Flow ◽

Oil And Gas ◽

Rock Strength ◽

Oil Wells ◽

Darcy Flow ◽

Sand Production ◽

Gas Wells ◽

Drag Forces ◽

Oil And Gas Wells

Summary Controlled laboratory experiments and some field studies have shown that the onset of sand production in gas wells differs from that in oil wells. Results from a general 3D sand-production numerical model are presented to explain the differences in the onset of sanding and sand-production volume for different fluids and under different flow and in-situ stress conditions. The sand-production model accounts for multiphase-fluid flow and is fully coupled with an elasto-plastic geomechanical model. The sanding criterion considers both mechanical failure and sand erosion by fluid flow. Non-Darcy flow is implemented to account for the high flow rates. The drag forces on the sand grains are computed on the basis of the in-situ Reynolds number. Both the intact rock strength and the residual rock strength depend on water saturation. Water evaporation (drying) resulting from gas flow is modeled using phase equilibrium calculations. The onset of sand production is compared for different fluid types (oil and gas). Model results are shown to be consistent with experimental observations reported in the literature. For example, the onset of sanding is observed at higher compressive stresses for gas wells as compared with oil wells. The primary mechanism for this is for the first time shown to be sand strengthening induced by evaporation of water. This effect is not observed in oil wells. The sand-production rate when non-Darcy effects are considered is lower than for Darcy flow. The reason for this is the lower fluid velocity (for the same drawdown) and, consequently, smaller drag forces on the failed sand grains. The effect of water breakthrough and water cut on sand production is studied from both mechanical and erosion perspectives. The model is shown to be capable of accurately predicting the onset of sanding and sand production induced by multiphase- and compressible-fluid flows, helping us to predict sanding issues in both oil and gas wells.

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