Managing Wellbore Instability in Horizontal Wells through Integrated Geomechanics Solutions: A Case Study from a Carbonate Reservoir

Khan, Khaleel Ur Rahman; Abdulaziz, Ahmad Azly; Ahmed, Sajjad; Ahmed, Mahbub

doi:10.2118/172550-ms

Cited by 7 publications

References 5 publications

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Stability Analysis of Highly Deviated Boreholes to Minimize Drilling Risks and Nonproductive Time

Abbas

Flori

Alsaba

2019

Journal of Energy Resources Technology

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The Lower Cretaceous Zubair Formation is a regionally extended gas- and oil-producing sandstone sequence in Southern Iraq. Due to the weak nature of the Zubair Formation, the lack of wellbore stability is one of the most critical challenges that continuously appears during the drilling development operations. Problems associated with lack of wellbore stability, such as the tight hole, shale caving, stuck pipe, and sidetracking, are both time-consuming and expensive. This study aimed to construct a geotechnical model based on offset well data, including rock mechanical properties, in situ stresses, and formation pore pressure, coupled with suitable rock failure criteria. Mohr–Coulomb and Mogi–Coulomb failure criteria were used to predict the potential rock failure around the wellbore. The effect of the inclination and azimuth of the deviated wells on the shear failure and tensile failure mud weights was investigated to optimize the wellbore trajectory. The results show that the best orientation to drill highly deviated wells (i.e., inclinations higher than 60 deg) is along to the minimum horizontal stress (140 deg). The recommended mud weight for this selected well trajectory ranges from 1.45 to 1.5 g/cc. This study emphasizes that a wellbore stability analysis can be applied as a cost-effective tool to guide future highly deviated boreholes for better drilling performance by reducing the nonproductive time.

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Stability Analysis of Highly Deviated Boreholes to Minimize Drilling Risks and Nonproductive Time

Abbas

Flori

Alsaba

2019

Journal of Energy Resources Technology

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Optimum Mud Overbalance and ROP Limits for Managing Wellbore Stability in Horizontal Wells in a Carbonate Gas Reservoir

Khan

Halim

Hamid

et al. 2016

SPE/IADC Middle East Drilling Technology Conference and Exhibition

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Saudi Aramco has been drilling horizontal and multilateral wells to develop gas fields. Due to production-induced decreasing reservoir pressures along with tight nature of the reservoir rock, development activities have focused more in placing wells towards the minimum horizontal stress direction and complete with multistage hydraulic fracturing aimed to improve lateral reservoir contact enabling higher production at sustained rates thereby increasing recovery with less number of wells to be drilled. Horizontal wells drilled in the minimum horizontal stress direction are more challenging due to complex geological conditions and compressional in-situ stress conditions. The data shows that some wells were drilled without major difficulty while some other wells encountered more problems leading to stuck pipe events. A detailed study was conducted to identify the nature of these problems and ascertain major controlling factors for this variable drilling experience to make future operations safer and more efficient through recommendations based on a diagnostic analysis of the observed problems in existing wells. Analysis of data suggests that excessive borehole breakouts and faster rate of penetration (ROP) are the key contributing factors to the observed drilling challenges. In addition, differential sticking has been found a potential risk across high porosity and/or depleted zones. As a result, optimum mud weight based on predrill geomechanics model was recommended to manage the hole stability. In addition, a safe limit of ROP as a function of hole azimuth was identified to manage efficient hole cleaning and avoid stuck pipe due to pack-off. The recommendations made based on this analysis enabled successful drilling and timely completion of several horizontal wells across the field.

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A Comprehensive Geomechanical Study to Understand Drilling Challenges in the Manifa Field Offshore, Saudi Arabia

et al. 2016

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Saudi Aramco has been producing from the Manifa offshore field in the Arabian Gulf since 2011. By drilling mainly lateral wells, Saudi Aramco has targeted the main reservoir that belongs to the early Jurassic period. The pay zone is overlaid with weaker interbedded sand/shale formations and carbonate formations of the upper and lower cretaceous period. The main challenges that were encountered while drilling these wells included total/partial mud losses and severe wellbore instability-related issues across the weaker formations overlaying the reservoir section (pay zone). An advanced geomechanical study was crucial for understanding the nature of the existing problems faced during drilling and applying the study's findings for drilling future extended reach (ERD) wells successfully. A comprehensive geomechanical study of the field was conducted by constructing a calibrated post-drill 1-D Mechanical Earth Model (1D-MEM) for selected vertical wells. The study helped in providing reliable rock mechanical properties and fracture gradients across the problematic formations, a lack of which was a limiting factor in understanding the nature of the problems while drilling. For the current study, an integrated workflow was implemented mainly to perform a root cause analysis of mud losses and to define well inclination (deviation) limits to drill through the problematic formations to minimize wellbore instability-related issues. Open hole log data was used to construct the 1D-MEMs. The developed models were further calibrated using all the available data (drilling observations, results of well testing, core mechanical testing, etc.). Image data was also analyzed to capture the presence of fractures/faults or related features along the wellbore. Based on the analysis results, it was concluded that the mud losses in the overlaid carbonate formations were attributed to the presence of localized open natural fractures or caverns, or vugs. It was also concluded that most of the wellbore instability-related issues (hole pack-offs, stuck pipe incidents, etc.) occurred due to insufficient drilling mud weights that were not able to support the rock on the wellbore wall. The present study helped in better characterization of the problematic formations and also provided useful information for planning future extended reach (ERD) wells. Some of the provided recommendations included acquisition of micro resistivity image logs (to identify nature of fracture), implementation of real-time geomechanics, and optimization of mud rheology, mud weight program, and casing design.

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Managing Wellbore Instability in Horizontal Wells through Integrated Geomechanics Solutions: A Case Study from a Carbonate Reservoir

Cited by 7 publications

References 5 publications

Stability Analysis of Highly Deviated Boreholes to Minimize Drilling Risks and Nonproductive Time

Stability Analysis of Highly Deviated Boreholes to Minimize Drilling Risks and Nonproductive Time

Optimum Mud Overbalance and ROP Limits for Managing Wellbore Stability in Horizontal Wells in a Carbonate Gas Reservoir

A Comprehensive Geomechanical Study to Understand Drilling Challenges in the Manifa Field Offshore, Saudi Arabia

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