Abstract
Abstract
Subsurface geomechanical assessment has critical implications for optimum drilling and completion design and successful well delivery to efficiently mitigate drilling challenges as well as avoid non-productive time. The present study focuses on the carbonate-dominated prolific hydrocarbon field of the Arabian Peninsula which exhibits significant wellbore instability challenges owing to high in-situ stress, and partial to total mud losses in naturally fractured and vuggy carbonates. Commonly faced challenges include differential sticking, drill string vibration, poor LWD (logging while drilling) log quality and subsequent wellbore instability. Being in a strike-slip tectonic regime, drilling long multi-laterals towards the minimum horizontal stress (Shmin) is associated with increased hole instability challenges, hard reaming, and mechanical sticking, which is leading to BHA (bottom-hole assembly)/ tools lost in hole and accidental side-tracks. Those contribute to significant NPT (non-productive time) and compromised drilling performance. This study discusses the benefit of integrating geomechanical modeling and real-time monitoring into the drilling operations: those helped to overcome the aforementioned challenges and reduce NPT by enhancing drilling performance.
Comprehensive geomechanical modeling and wellbore stability analyses are carried out to study the impact of in-situ stresses, and pore pressure on the stability of the rock/ wellbore wall. Along with the safe mud weight window recommendation and supporting customized drilling fluid and bit design, the study also identified potential sub-surface and drilling risks, which were quantified to optimize the drilling practices and mitigation plans. The predrill models were updated in real-time to fine-tune the predictions on each well and to better constrain the regional geomechanical understanding. During real-time GeoMechanics monitoring we are using LWD logs and drilling parameters to aid in inferring early indicators about the wellbore condition, mud invasion into the formation and other drilling challenges; the real-time GeoMechanics group facilitated timely advisory and effective communication with the rig and relevant parties. Implemented recommendations based on the symptoms of wellbore failure (i.e., early, time dependent failure) exhibited measurable- and significant improvements in drilling performance, penetration rate, overall wellbore quality towards achieving well objectives with minimized NPT. Furthermore, by establishing new communication protocols and adhering to them, a proactive response culture has been developed in order to make informed and collective decisions timely and effective.