Well Design Advancement – Engineering Solutions to Overcome Risks and Challenges in Drilling Risky Thermal Filed in North of Oman
Authors: Rawahi Qasim , Rashdi Hussain 
Published: March 2022

This paper discusses how re-designing the well is driving the performance and maximizing the well life considering all risks and challenges associated with drilling in Oman thermal Q fields that required further engineering solutions and in-depth simulation and analysis. Managing the risk and delivering wells safely in the most competitive and economical approach are most critical value drivers of these wells. Main risks in Q field are shallow gas, high level of H2s, highly fractured formation, drilling in total losses scenario with ERD wells profile, managing high reactive shale, cement bond quality and critical zonal isolation requirement. It also reflects the unique well control approach in managing gas cap risk with total losses scenario.

Collecting the data and list all risks and challenges associated with drilling operation to identify the functionality and other enablers was the most critical step in evaluating what givens and opportunities are. Then, utilizing well plan landmark and other simulation tools to simulate torque and drag, shock and vibration, hydraulics and hole cleaning to optimize the design of the well profile and BHA configurations. Consequently, re-designing the well and proposed the most suitable and fit for purpose design along with different loads and stress checks utilizing wellcat tool. Real-time data utilized during the execution phase to maximize drilling efficiency and design effectiveness. Finally, the well delivered assessed against its critical function requirements like minimum zonal isolation between different reservoirs and well integrity.

By proposing engineering solutions and design optimization, utilizing both frontend simulation and past filed best practices, all Q field wells delivered safely with required quality within its budget and time frame. All challenges and risks have been overcome and managed to deliver the project efficiently like torque and drag, hole cleaning, shock and vibration, and back-reaming. Also landing criteria and drilling parameters have been developed to avoid losses while landing the well in a highly depleted reservoir and manage the threat of getting well control scenario. Furthermore, in the execution phase, real-time data monitored to enhance the efficiency and drilling parameters were optimized to keep them within the planned operating envelope. As the design focused on long-term well integrity and longevity, further evaluation post well delivery curried out to check the zonal isolation with positive results that reflect healthy well integrity and fulfillment all functional requirement.

This paper reflects the complexity and unique approach in managing well control risk with dynamic kill procedure (Natih procedure) while drilling gas cap in highly fractured formation associated with concertation of H2S gas. Also, it is echoing the importance of advance engineering analysis and solutions in delivering the high ERD ratio wells with their challenges and risk profile. As well it is emphasizing on the need of reviewing the standardized well design within development fields due to the changing in subsurface parameters and drilling strategies.