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Abstract
Historically, extended reach offshore wells in Trinidad & Tobago were characterized by wellbore instability and hole cleaning challenges. These phenomena had become almost impossible to manage effectively in the highest angle wellbores, leading to levels of non-productive time (NPT) that threatened the economic viability of the latest development.

Wellbore instability exacerbated the hole cleaning challenge, fueled by a new instability mechanism at highest wellbore inclinations. This led to pack-offs and stuck pipe incidents. Additionally, poorly understood and generally insufficient hole cleaning practices increased stuck pipe risk, and also caused the equivalent circulating density (ECD) to rise, resulting in mud losses due to the narrow window between mud density required for wellbore stability, and formation fracture gradient.

The solution to these problems was found through advanced downhole measurements of borehole stability and hole cleaning, transmission of those data back to surface via a high frequency medium ("networked or wired" drill-pipe), deployment of subject matter experts into the rig team for critical phases of the operation, and introduction of unconventional drilling and decision-making practices to mitigate the problem phenomena.\

This paper describes the transformational efficiency improvement that was achieved by this combination of new technology, improved workflows, and multidisciplinary expertise deployed to the rigsite. The methodology was implemented on the third well, resulting in a reduction of NPT from 47% and 48% on the first two wells, to 10% on the third, clearly expressing the enhanced control of these drilling phenomena on the third well.

Recommendations offered are relevant to many extended reach drilling campaigns, and may be critical to the success of ultra-ERD wells.

Situation
The multi-well development drilling program targets sands in the Chachalaca complex and is located on the East Shelf of Trinidad, about eight km from the Mahogany Field. The field is situated on a regional NE-SW ridge and bisected by regional growth faults that separate the Mahogany/Chachalaca sub-basin from the Corallita/Lantana discovery, approximately 3 km to the east. The field consists of multiple stacked pay sands across multiple NW-SE trending normal faults that dip to the NE. See Figure 1.

As the Trinidad & Tobago multi-well campaign developed, the wells were drilled at higher inclination, extending the step out beyond 10,000ft, see Figure 2. Operations in both fields frequently suffered from wellbore instability and hole cleaning difficulties, especially around multiple problematic zones that are associated with faults.