Advanced Drilling Strategies and Zonal Isolation Techniques for High Temperature, High Pressure Wells, A Case Study

Abstract This case study outlines the successful risk management through engineering in Mesozoic reservoir. The subject well is a High-Pressure High Temperature (HPHT) extended reach S-Shape. The primary objective of this paper is to detail the strategy applied to ensure well integrity, effective zonal isolation, and operational efficiency while mitigating risks associated with mud losses and crossflows. Scope will cover efficient isolation using a 5-in. liner × 6-1/8-in. open hole with a custom swellable packer; Validation the use of Managed Pressure Drilling (MPD) techniques and two-phase flow systems; minimization non-productive time (NPT) and operational costs. Risk management strategy starts through offset wells analysis. General well design is affected by the presence of a series of folds and faults, as well as salt domes without a predetermined orientation. Therefore, the existence of significant uncertainty in pore pressure prediction. A safe execution depends on real time follow up through dynamic simulations and managed pressure drilling with advanced intelligent chokes. Whenever the combination of late and early Jurassic was confirmed, contingency scenario needs to be activated. This involves custom cement job in reduced annular clearance of 5-in. × 6-1/8-in. with fit for purpose packer and cement system. And finally, to explore the early Jurassic reservoir at depths from 7,400 m to 7,500 m true vertical depth (TVD) safe execution depends on managed pressure drilling (MPD) with continuous nitrogen injection and real time parameters correlation with dynamic simulations for drilling 4-1/8-in. section. This strategy yielded several positive results. Good identification of the geo-body position through controlled influx management within 1.75 to 1.81 gr/cc using MPD equipment. Successful zonal isolation, through selection and deployment of a cement system and a swellable packer activated by oil-based mud, designed to operate up to 191 degrees Celsius (°C) and withstand differential pressure up to 10,000 psi. The well integrity was confirmed through negative test and further in production phase. The reservoir was successfully explored with minimal reservoir damage possible in subject conditions through the use of at balance two-phase flow to manage mud losses and maintain well control. Although at first, such target depths and high-pressure nature of the field may seem to be intimidating, the successful risk management and timely intervention to activate contingency has proven successful. The well achieved the planned technical limit time of 131 days, demonstrating this strategy's efficiency.