Summary
Many deepwater-development projects in operators’ portfolios require lower
costs to meet internal economic thresholds. Because of this, Shell has
looked at extending surface-blowout-preventer (BOP) activities to include well
testing and completion techniques for deepwater wells in conjunction with
surface-BOP drilling.
The cost advantages of surface-BOP-drilled wells have been demonstrated
(notably in the Far East), but the recent surface-BOP-drilled well in Brazil is
a milestone in terms of extending the applicability to deeper water and harsher
environments. The enabling technology has been the subsea isolation device
(SID). Testing and completion techniques have been developed to be
compatible with surface-BOP wells drilled with an SID.
This paper focuses on the following aspects:
•Well testing using surface-BOPs from a moored rig and
•Well completions using surface-BOPs from a moored rig.
Shell has developed a testing configuration to carry out a DST, essentially
using standard equipment. The well-testing equipment configuration is currently
ready for use and has been run in a subsea-BOP well.
In completion operations, the availability of a high-pressure (HP) riser
does not add significant complexity and even actually simplifies some of the
completion activities. Conceptual studies and early hazard/risk
assessments have shown there are no obvious “showstoppers,” and the duration of
a surface-BOP-rig completion is expected to be very similar to a subsea-BOP-rig
completion.
This paper describes the results of the conceptual studies, early hazard
assessment exercises used to define the basic design parameters, and more
detailed hazop studies.
Introduction
As deepwater exploration and development move into even deeper water and
more arduous environments, operators are looking at ways to reduce well costs
to make prospects and developments economically more attractive. One of
the key avenues seen to do this is to accomplish drilling, testing, and
completing wells by use of smaller deepwater rigs, consequently resulting in a
reduction in rig rates. Surface-BOP technology facilitates the deployment
of smaller rigs in deeper water, thus lowering day rates, well costs, and
field-development costs.
To date, most ultradeepwater wells (in which water depth is greater than
5,000 ft) have been executed using the latest generation of new or converted
drilling vessels (these will be referred to as “Generation V” rigs). Over
150 subsea wells in varying water depths have now been executed with floating
rigs with surface-BOPs in locations around the world. In 1967, a
semisubmersible rig (Sedco-135) was used to drill a subsea well by use of
surface-BOPs offshore Nigeria in EA-3. Since then, a number of operators
have pioneered the use of surface-BOPs with moored rigs in the benign
environmental conditions of the Far East. Shell has recently used
surface-BOPs on a Generation V dynamically positioned (DP) rig to extend the
7,500-ft-water-depth capability of the rig—drilling a deepwater exploration
well in 9,474 ft of water offshore Brazil.1 The trend is to take this technique
and apply it in a number of deepwater-operating areas with older Generation III
and IV rigs that were not specifically built for deepwater operation. This
paper outlines the well-testing and well-completion approaches that are planned
to meet these challenges.
The overall surface-BOP system will be described followed by the description
of well-testing and well-completion methodologies. It should be noted that
these methodologies are continuously worked on and refined; once actual
experience is gained, they will, of course, change and be further
optimized.
© 2005. IADC/SPE Drilling Conference
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