Successful mechanical earth model construction and wellbore stability analysis using elastic and plasticity solutions, a case study

Motahari, M.; Hashemi, Abdolnabi; Molaghab, Abdollah

doi:10.1016/j.gete.2022.100357

Cited by 11 publications

(3 citation statements)

References 34 publications

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“…In the face of wellbore collapse, wellbore enlargement, and other phenomena during the drilling, the density of the drilling fluid was adjusted and improved in varying degrees, but the effort for reducing wellbore instability was minimal and even exacerbated wellbore collapse. For instance, in the 3100−4300 m section of well NP36, the drilling fluid density was increased from 1.23 to 1.39 g/cm 3 , but the well diameter expansion was not effectively reduced and increased to about 80% instead, which seriously affects the progress of oil and gas exploration and development in this block. Considering the geological characteristics of shale in study area, it is urgent to further study the adaptability of drilling fluid performance and shale in the Dongying formation, and to evaluate the performance of plugging drilling fluid to improve wellbore stability.…”

Section: Methodsmentioning

confidence: 99%

“…Wellbore instability is essentially mechanical instability . The most commonly used method on site is to increase the density of the drilling fluid to maintain wellbore stability. , However, high density drilling fluid will lead to an increase of liquid column pressure in the wellbore, which may lead to drilling fluid filter more easily due to a higher positive pressure difference, and even exacerbate wellbore instability.…”

Section: Introductionmentioning

confidence: 99%

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Experimental Study on the Adaptability of Plugging Drilling Fluids to Wellbore Stability in Hard Brittle Shale Formations

et al. 2022

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The problem of wellbore stability in hard brittle shale formations is an important research topic in the exploration and development of shale gas. To solve this problem, the adaptability of the plugging drilling fluid to wellbore stability in the hard brittle shale of the tertiary Dongying formation in Bohai Bay Basin, China, was investigated. The results show that the clay content of the hard brittle shale in the study block is as high as 39.2% on average, with great possibility for hydration. The pore structure in the shale is dominated by micron-scale fractures and pores. A dense structure was formed on the surface of the shale after being immersed in plugging drilling fluid, and the matrix permeability of the shale was reduced by 91.1% and the fracture permeability by 98.7%. The water content increment of the shale after immersion was merely 0.75%, which reduced the probability of hydration greatly. Compared with the field-inhibitive drilling fluid, the plugging drilling fluid improved the uniaxial compressive strength of shale by 28%, which is more conducive to maintaining the wellbore stability. The seepage stress aggravates the risk of wellbore instability, while the hydration stress does not, but both increase the risk of rock instability at positions away from the well wall. The plugging drilling fluid affects the seepage stress and hydration stress by reducing the shale permeability and water content. With the decrease of permeability and water content, the potential instability zone of a wellbore becomes smaller.

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Section: Methodsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Experimental Study on the Adaptability of Plugging Drilling Fluids to Wellbore Stability in Hard Brittle Shale Formations

et al. 2022

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“…Consequently, a numerical approach shall be considered to solve for these unknowns under specific initial and boundary conditions. Advanced numerical schemes, e.g., the finite element method, are suitable for solving complex geomechanical problems (Ebrahimabadi et al, 2015;Hosseini et al, 2023a;Hosseini et al, 2023b;Kianoush et al, 2023c;Kingson et al, 2023;Mackerle, 1999;Motahari et al, 2022;Palano et al, 2023;Rafieepour et al, 2020;Tao and Ghassemi, 2007;Zalnezhad et al, 2022). Regardless, the finite element method is time-consuming and computationally expensive.…”

Section: Introductionmentioning

confidence: 99%

Wellbore Stability in a Depleted Reservoir by Finite Element Analysis of Coupled thermo-poro-elastic Units in an Oilfield, SW Iran

Pirhadi,

Kianoush,

Ebrahimabadi

et al. 2023

Preprint

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Maintaining wellbore stability in depleted reservoirs is a critical problem. With production from hydrocarbon reservoirs, the pore pressure of the reservoir is reduced over time, and the reservoir is depleted since field development is one of the main purposes for oil companies. Heavy mud weight in depleted reservoir caused fracture due to reduced fracture gradient, and low mud weight caused blow out in high-pressure zone or well collapse due to shale beds that required high mud weight to prevent collapse. Considering geomechanics and coupled equilibrium equation, continuity equation, Hook’s law, compatibility equation, Darcy’s law, and thermal relation, the Thermo-poro-elastic equation was derived in this research. A finite element method has been developed to implement the fully coupled thermo-poro-elastic non-linear models. The finite element model was validated by comparing it to the available analytical solutions for the thermo-poro-elastic wellbore problems in shale. The non-linear thermal-poro-elasticity finite element model was used to analyze wellbore stability in a depleted limestone reservoir during drilling. The numerical results showed that a decrease drilling fluid’s temperature (cooling) causes to increase in the potential for tensile failure and reduces the potential of shear failure. Due to the depletion reservoir, the potential of tensile failure increased than shear failure, so heating the drilling fluid could cause wellbore stability in the depleted reservoir. Furthermore, based on the numerical results, it may be concluded that the drilling fluid’s temperature is one of the important factors in the wellbore stability analysis in depleted reservoirs.

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Assessing the Minimum Safe Drilling Mud Weight to Avoid Damage Zone by Frictional-Strengthening Cohesion-Weakening Models

Zoughy,

Molladavoodi

2023

Geotech Geol Eng

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Successful mechanical earth model construction and wellbore stability analysis using elastic and plasticity solutions, a case study

Cited by 11 publications

References 34 publications

Experimental Study on the Adaptability of Plugging Drilling Fluids to Wellbore Stability in Hard Brittle Shale Formations

Experimental Study on the Adaptability of Plugging Drilling Fluids to Wellbore Stability in Hard Brittle Shale Formations

Wellbore Stability in a Depleted Reservoir by Finite Element Analysis of Coupled thermo-poro-elastic Units in an Oilfield, SW Iran

Assessing the Minimum Safe Drilling Mud Weight to Avoid Damage Zone by Frictional-Strengthening Cohesion-Weakening Models

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