Redefining Transient Pressure Testing in High-Risk Wells with 45% H2S: ADNOC Offshore Success with Advance Intelligent Wireline Mini-DST Eliminating Conventional DST Requirements

Abstract

Conventional drill stem testing (DST) in high-risk high H2S offshore carbonate wells increase operational complexity, rig time, and health, safety, and environmental (HSE) exposure, as well as contributes to GHG emissions. For the appraisal well located inside the Marine Protected Area, DST execution may be even more technically challenging or operationally unjustifiable. Permitting constraints might have resulted in a shift of surface location, significant increment in cost and complexity of drilling and testing operations, in addition to stringent flaring restrictions. This paper demonstrates Abu Dhabi Offshore case study how intelligent wireline-based Mini-DST and transient pressure testing were successfully deployed to obtain decision-critical reservoir data while eliminating conventional DST requirements and environmental footprint. Despite challenging borehole conditions, including 33% H2S in reservoir conditions and up to 45% H2S in the gas phase at surface, the wireline Mini-DST program successfully delivered reliable formation pressure, mobility indication, and fluid identification across the targeted Arab reservoirs. The results enabled reliable assessment of reservoir behavior and supported development decisions without executing a conventional DST. Controlled drawdown and buildup sequences provided a fit-for-purpose radius of investigation, effectively bridging the gap between conventional wireline formation testing and DST objectives while avoiding prolonged surface flow. Compared with the originally planned sour conventional DST scenario, the adopted intelligent wireline Mini-DST workflow eliminated the need for extended sour surface production and avoided the major DST package, contributing to an estimated 40 days of avoided DST-related exposure and approximately USD 10 million in total cost avoidance, including approximately USD 7 million directly associated with eliminating the conventional DST scope. This case study demonstrates that intelligent wireline Mini DST executed in an 8.5″ hole section can serve as a fit-for-purpose alternative to conventional DST in high-risk offshore wells. By redefining transient pressure testing through a risk-balanced, decision-driven approach, the workflow provides a scalable and repeatable template for future and similar cases.