Evaluation of mechanical, chemical, and thermal effects on wellbore stability using different rock failure criteria

Aslannezhad, Masoud; Keshavarz, Alireza; Kalantariasl, Azim

doi:10.1016/j.jngse.2020.103276

Cited by 25 publications

(9 citation statements)

References 38 publications

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“…Fluids on a Wellbore Failure Zone. The Mohr−Coulomb criterion is often used to judge rock instability, 30,31 as shown in eq 13. In order to study the failure zone around a wellbore under the action of different drilling fluids, an additional cohesion strength is defined to reflect the failure zone, seen in eq 14.…”

Section: Influence Of Drillingmentioning

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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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: Influence Of Drillingmentioning

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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“…Shale oil and gas are important unconventional resources and are becoming more and more important in oil and gas production. At present, there are more and more serious wellbore instability problems in the drilling process of shale oil and gas wells (Chen et al, 2003;Akbarpour and Abdideh, 2020;Aslannezhad et al, 2020), and the instability proportion is as high as 90% (Chen et al, 2014;Liu, 2014;Liu et al, 2021). Many factors will lead to wellbore instability, such as wellbore stress concentration caused by wellbore formation, vibration of the drilling tool assembly during drilling, and changes in formation rock properties caused by invasion of drilling fluid into the formation.…”

Section: Introductionmentioning

confidence: 99%

The invasion law of drilling fluid along bedding fractures of shale

Wang²,

Zhang³

et al. 2023

Front. Earth Sci.

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In the process of drilling, the drilling fluid will invade into the bedding plane of shale under the action of pressure difference that will cause hydration collapse and wellbore instability. In order to ensure the wellbore stability during shale oil and gas drilling, it is necessary to clarify the invasion law of drilling fluid along bedding fractures during the drilling process. The immersion experiment method is often used to study the invasion law of drilling fluid, which is quite different from the actual invasion process of drilling fluid underground. In this paper, the depth of drilling fluid invasion into shale under different confining pressures and displacement times is intuitively and accurately determined by the displacement experiment and NMR scanning first. Also, then the mathematical relationships between drilling fluid invasion depth and invasion time, invasion pressure difference, confining pressure, bedding angle, and drilling fluid viscosity were established. The errors between the calculated values of the drilling fluid invasion depth and the experimental values were less than 15%, and the calculation accuracy was high. In addition to the influence of invasion time, formation pressure difference and confining pressure on invasion depth were researched through the method of numerical simulation. The results showed that the liquid invasion depth increased logarithmically with the increase of invasion time and formation pressure difference, but it grew slowly in the later period and tended to be stable; the invasion depth decreased exponentially with the increase of confining pressure, bedding plane angle, and drilling fluid viscosity. The results in the paper provide a basis for the subsequent determination of the collapse pressure and collapse period of bedding shale.

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“…Meng et al [50] examined the M-C, D-P, ML, Mg-C, and 3D H-B criteria using six types of rocks, the importance of strength criteria for WSA was assessed for HP/HT drilling, and their results indicated that the ML criterion is best selection to conduct WSA. Aslannezhad et al [51] comprehensively considered all mechanical, thermal, and chemical effects to evaluate the applicability of the six practical strength criteria in WSA, and they indicated that the ML, Mg-C, and 3D H-B criteria can predict a safer collapse pressure for shale formations, so these three criteria can be used interchangeably. Wang et al [52] used the M-C, D-P, and Mg-C criteria to assess the wellbore collapse pressure under the five different stress regimes, and they found that various well trajectories have different selection of the best strength criteria under different stress regimes.…”

Section: Introductionmentioning

confidence: 99%

“…In the above-mentioned studies, different criteria have been developed and employed to conduct WSA, most of the studies recommended to use the M-C, Mg-C, and ML criteria for WSA [8,[38][39][40][41][42][43][44][45][46][47][48][49][50][51][52]. However, the collapse pressure does not comply with different strength criteria, and some of the authors indicated that the best strength criteria are different for various well trajectories under different stress regimes [52,53].…”

Section: Introductionmentioning

confidence: 99%

Analytical Model of Wellbore Stability Analysis of Inclined Well Based on the Advantageous Synergy among the Five Strength Criteria

Shi

Zhang

et al. 2023

Geofluids

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The proper drilling mud density is vital for wellbore stability maintenance, which relies on both stress distribution on the borehole wall and rock strength. Thus, the selection of rock strength criterion is vital for wellbore stability analysis (WSA), and several strength criteria have been developed and employed to perform WSA, but the real collapse pressure does not comply with any single strength criterion. Therefore, to accurately predict the critical mud weight against wellbore collapse, an analytical model of WSA was proposed for inclined wells based on the advantageous synergy among the five types of strength criteria, such as the Mohr-Coulomb criterion, Mogi-Coulomb criterion, Drucker-Prager criterion, modified Wiebols-Cook criterion, and modified Lade criterion. The predicted results among these analytical and five conventional models were compared under three kinds of typical stress regimes, such as normal, strike-slip, and reverse faults. Finally, five kinds of typical oil and gas field data were collected to further verify the accuracy of this new model. The results indicated that different models predicted different collapse pressure, owing to the Mohr-Coulomb criterion ignoring the intermediate principal stress ( σ 2 ), so as to always give the greatest collapse pressure, followed by the present analytical model and the Mogi-Coulomb criterion, while the other three types of strength criteria gave different results, because of the difference in the influence of σ 2 , while the present analytical model integrated the advantageous synergy among the five strength criteria. The prediction error of the conventional analytical model ranges from 9.4 to 34.2% with an average of 22.1%, while the prediction error of this new model ranges from 2.3 to 12.5% with an average of 7.1%, so that the present analytical model has much higher accuracy than that of any single strength criterion. In addition, this new analytical model can be simplified as the conventional analytical model by adjusting the weight coefficients.

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Evaluation of mechanical, chemical, and thermal effects on wellbore stability using different rock failure criteria

Cited by 25 publications

References 38 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

The invasion law of drilling fluid along bedding fractures of shale

Analytical Model of Wellbore Stability Analysis of Inclined Well Based on the Advantageous Synergy among the Five Strength Criteria

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