A Methodology for Drilling Through Shales in Environments with Narrow Mud 
Weight Window (NMWW)

Araujo, Ewerton; Fontoura, S. A. B.; Pastor, Jorge Aurelio

doi:10.2523/94769-ms

Cited by 4 publications

(2 citation statements)

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“…Mohr-Coulomb criterion was assumed to predict collapse gradients enabling 15 % of yield area along the wellbore wall, being the methodology used to calculate lower and upper collapses with a yield area around the wellbore wall previously developed by Araújo et al (2005). The fracture gradient was assumed to be that one capable to initiate a fracture along the wellbore wall.…”

Section: Stability Analysismentioning

confidence: 99%

A wellbore stability analysis of a horizontal well drilled through unconsolidated sandstones

Marchesi¹,

Morales-Monsalve²,

Fontoura³

et al. 2020

Congresso Brasileiro De Mecânica Dos Solos E Engenharia Geotécnica

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Wellbore stability studies are essential to guarantee the success during drilling oil and gas wells. This case study shows a Post Morten analysis of a horizontal well successfully drilled along a depleted reservoir, but with a narrow mud weight window, after a lost circulation during the cementation of the previous casing. The main goal is to show that even having a well-established general methodology for wellbore stability analysis, specific challenges may require different solutions to calibrate the mud weight window with field evidences. Challenges faced during drilling this wellbore were: (i) the wellbore was drilled after a lost circulation during cementing the previous phase. (ii) the existence of a narrow mud weight window, conditioned by unconsolidated sands with low resistance parameters, in the reservoir; (iii) the well path implies a critical combination of stresses around wellbore wall; (iv) the presence of a depleted reservoir. The in-situ stress prediction of horizontal stresses involved different criteria and showed a strong difference between the overburden and the reservoir. Minifrac tests, carried out in many wells along the field, present a considerable variation along the reservoir, suggesting some in-situ stress variation throughout the field. The analysis imposed a series of iterations by a carefully guided calibration of the input parameters and failure criteria. The analysis allowed calibrating and explaining field evidences, including the losses during cementing.

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Section: Stability Analysismentioning

confidence: 99%

A wellbore stability analysis of a horizontal well drilled through unconsolidated sandstones

Marchesi¹,

Morales-Monsalve²,

Fontoura³

et al. 2020

Congresso Brasileiro De Mecânica Dos Solos E Engenharia Geotécnica

View full text Add to dashboard Cite

show abstract

“…The well which is producing the formation may be damaged beyond repair. This requisite of well planning may be difficult to attain if the well planning situation incorporates borehole geometry which may be the causal attribute of mud challenges, profound zones and abnormal pressure characteristics (Villaescusa et al 2002;Araujo et al 2005;Nelson et al 2005).…”

Section: IImentioning

confidence: 99%

Log - Derived Pressure Profile Modelling in a Niger Delta Field

Anyanwu¹,

Dosunmu²

2019

IJERT

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Failure to accurately determine pore pressures prior to well planning has led to costly drilling failures and major environmental concerns. Uncertainty in these pressures arise from the lack of fit for purpose models suitable for pressures in the Niger Delta. In this work, Log methods have been applied to predict pore pressures for a field in the Niger Delta. RFT data has been used to validate existing pressure modelling methods to aid in selecting best suited model for this field.

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Analysis of Stress and Pore Pressure in Naturally Fractured Shale Formations: A Finite Element Based Chemo-Thermo-Poroplastic Model

Roshan

Rahman

2010

SPE Eastern Regional Meeting

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Most shale formations are naturally fractured and wellbore instability is a common problem in these formations. In previous wellbore stability analysis shale formations have been treated as a homogeneous rock which underestimates drilling mud parameters. The aim of this paper is to study the transient change in pore pressure and stress state around a wellbore drilled in a chemically active fractured shale formation. For this purpose a finite element model for coupled chemo-thermo-poro-plasticity is developed. A discrete fracture network is generated based on an object-based hybrid neuro-stochastic simulation. Permeability tensors of the fracture network were calculated by using boundary element method which is based on periodic boundary conditions around the grid block and interface boundary conditions around the fracture edges. In order to solve the plasticity problem a single step backward Euler algorithm including a yield surface correction scheme is used to integrate the plastic stress-strain relation and an initial stress method is employed to solve the non-linearity of the plastic equation. Super convergent patch recovery is used to accurately evaluate the time dependent stress tensor. The solute advection and thermal convection are also considered due to presence of the natural fracture system. From the results of this study it was revealed that the pore pressure decreases around the wellbore due to the backflow of chemical and thermal osmosis. When drilling through fractured shale formations, however, the decrease in pore pressure is lower than that of intact shale formations which is mainly due to solute advection through the fractures. Also it was found that the effective radial and tangential stresses can reach yield strength of the rock in presence of fracture system thus casusing serious instability problems. It is more likely to form a plastic zone near the wellbore wall in the presence of natural fracture than otherwise. In this study the formation of plastic zone leads to wellbore failure by exfoliation.

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A Methodology for Drilling Through Shales in Environments with Narrow Mud Weight Window (NMWW)

Cited by 4 publications

References 0 publications

A wellbore stability analysis of a horizontal well drilled through unconsolidated sandstones

A wellbore stability analysis of a horizontal well drilled through unconsolidated sandstones

Log - Derived Pressure Profile Modelling in a Niger Delta Field

Analysis of Stress and Pore Pressure in Naturally Fractured Shale Formations: A Finite Element Based Chemo-Thermo-Poroplastic Model

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