Sensitivity analysis of geomechanical parameters affecting a wellbore stability

Soltanian, Hamid; Pourmazaheri, Yaser; Abdollahipour, Abolfazl; Fatehi-Marji, Mohammad

doi:10.1007/s11771-019-4046-2

Cited by 18 publications

(5 citation statements)

References 31 publications

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“…There is little change between ROVmax and ROVmin for E at one specific value, which shows that the sensitivity of E is stable throughout the calculation period. Therefore, the strain or displacement evolution does not affect the sensitivity of E , as observed in another study (Abdollahipour et al 2019).…”

Section: Parameter Sensitivity Of Mechanical Behaviorsupporting

confidence: 57%

New Unsaturated Dynamic Porosity Hydromechanical Coupled Model and Experimental Validation

Wang

Howlett

et al. 2022

Int. J. Geomech.

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Constitutive coupled modeling has developed rapidly in recent decades, with numerous new models published. However, few models consider dynamic porosity, and experimental validation of such a model remains a challenge due to multiple variables. In this study, a new constitutive model for unsaturated soil with dynamic porosity was developed and validated using test data from two experimental studies that yielded good results (relative average error AVRE = 0.8631-1.3046, R 2 = 0.9028-0.9981). The sensitivity of the model to the four primary parameters was analyzed to investigate the influence of model properties on the hydraulic and mechanical behavior. Results show that the calculation of volumetric strain is most sensitive to Young's modulus (E), while the calculation of specific water volume is most sensitive to permeability (k). Also, the sensitivity of the parameters changes with their value. Modeled results show that the porosity change significantly affects both hydraulic and mechanical behavior, even when soil undergoes relatively low deformation. Relative calculation error decreases notably after porosity change is considered (44.9% and 35.2% improvement in two different calculations). This study also finds that dynamic porosity affects the deformation energy of solids.

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Section: Parameter Sensitivity Of Mechanical Behaviorsupporting

confidence: 57%

New Unsaturated Dynamic Porosity Hydromechanical Coupled Model and Experimental Validation

Wang

Howlett

et al. 2022

Int. J. Geomech.

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“…According to Equation ( 7), the maximum and minimum principal stresses of borehole wall are substituted into the formula of weak surface strength criterion (Equation ( 10)). According to Equation (11), it can be judged whether the shale has shear failure in the rock matrix or sliding failure along the soft surface. The wellbore failure area and failure pattern flow are shown in Figure 3.…”

Section: Stress Distribution Model Of Shale Formationmentioning

confidence: 99%

“…Moreover, in situ stress is very important for safe drilling [9], and the stress concentration is different from that of isotropic formations on the borehole wall of stratified shale [10]. Among them, the maximum horizontal ground stress has the greatest influence on the stability of shale formation [11]. In addition, anisotropic seepage will cause changes in the stress field near the shaft wall [12,13], which will affect the accurate calculation of shaft wall collapse pressure.…”

Section: Introductionmentioning

confidence: 99%

Study on Wellbore Stability and Failure Regions of Shale considering the Anisotropy of Wellbore Seepage

et al. 2021

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The hard and brittle shale formation is prone to collapse and instability, and the penetration of drilling fluid along the bedding reduces the mechanical properties of rock near the borehole wall, resulting in serious downhole accidents. Therefore, in this paper, the geomechanical parameters of the reservoir in the Longmaxi formation of Jiaoshiba were determined by field hydraulic fracturing and laboratory experiments. Then, the stress distribution model of borehole wall under the condition of underbalanced seepage flow is established based on the experimental results obtained by mechanical experiments on underground cores. The instability zone of borehole wall under the condition of underbalance is calculated and analyzed. The results show that the two-way horizontal ground stress of the Longmaxi formation is higher than 2.2 MPa/100 m, and the original ground stress is high. Moreover, the mechanical parameters of the stratified shale stratum matrix and weak surface are significantly different. The cohesion (4.7 MPa) and the angle of internal friction (26.9°) of bedding plane are significantly lower than that of the matrix (7.77 MPa) and the angle of internal friction (46.7°). Hard and brittle shale is easy to be destroyed along the stratification. Under the condition of underbalanced seepage, the mechanical properties of borehole shale can be stable. It is found that when the borehole axis is vertically stratified, the collapse pressure is the lowest, while in other drilling directions, the drilling fluid density needs to be increased by 0.5 g/cm3 to maintain the borehole stability. With the increase of the inclination angle of bedding plane, the wall failure area increases. The results of this study can provide guidance and suggestions for drilling in Jiaoshiba block and other permeable hard and brittle shale formations.

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“…17,18 The subjective factors mainly depend on the disturbance induced by drilling operations, including wellbore trajectory, wellbore pressure, wellbore temperature, drilling fluid chemistry, and drill-string collision. [19][20][21][22][23][24] Currently, many scholars focused on the determination of reasonable wellbore pressure or drilling fluid density, wellbore trajectory optimization, and chemical anti-collapse measure of the drilling fluid. [23][24][25][26] However, regarding the wellbore instability caused by drill-string collision has not been paying enough attention.…”

Section: Introductionmentioning

confidence: 99%

Influence of drill-string lateral collision on wellbore stability of a horizontal well

Huang

et al. 2022

Advances in Mechanical Engineering

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A finite element model of wellbore stability was proposed for a horizontal well, and drill-string friction and lateral collision in the process of rotary motion were taken into account. An unconfined compression test was used for model validation, the normalized yielded zone area (NYZA) was employed to analyze wellbore stability, and the influence of a lateral collision on wellbore stability was simulated. The results indicated that the stress-strain curve of numerical simulation consists with unconfined compression test, and the maximum relative error is <2.2%. The evolution of NYZA can be divided into three typical stages: stage I (static balance), stage II (dynamic growth), and stage III (dynamic balance). Both normal and shear stresses reach to the peak value in stage II, while they always fluctuate in a relatively small range in stage III, so that the wellbore stability mainly affected by the first collision of drill-string. Both lateral acceleration and friction effects have significant impact on wellbore stability. The initial collision position and the size of drilling tool have a certain influence on wellbore stability, while the revolving speed of drill-string almost has no impact. The present paper has guiding significance for wellbore collapse prevention and drilling parameter optimization.

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Sensitivity analysis of geomechanical parameters affecting a wellbore stability

Cited by 18 publications

References 31 publications

New Unsaturated Dynamic Porosity Hydromechanical Coupled Model and Experimental Validation

New Unsaturated Dynamic Porosity Hydromechanical Coupled Model and Experimental Validation

Study on Wellbore Stability and Failure Regions of Shale considering the Anisotropy of Wellbore Seepage

Influence of drill-string lateral collision on wellbore stability of a horizontal well

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