Daan Veeningen, NOV IntelliServ, Martyn Fear, Husky Energy, Stephen Willson,
SPE Deepwater Drilling and Completions Conference,
20-21 June 2012,
Galveston, Texas, USA
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.
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.