Summary
The initial impetus for developing 2,000,000-lbf landing strings was the
fact that failures in the field were being experienced with loads less than
equipment ratings. This paper pertains to the technological development of a
completely integrated landing system that provides the ability to extend the
deepwater drilling and completion envelope. This system comprises an elevator,
slipless spider, and landing string—all specifically designed to land
heavy-casing strings in deepwater wells and thus overcome the load limitations
of conventional equipment. All stages of evolution are analyzed, including
research, development, design, verification testing, manufacturing, proof
testing, running, handling, and actual case histories detailing field use.
Actual verification-testing loads were over 5,200,000 lbf, and proof-testing
loads were 3,000,000 lbf. Unique manufacturing challenges and solutions
associated with the production of ultrathick wall landing strings, with
2,000,000 lbf at super-premium-yield ratings1 (90% remaining body wall), are
presented in detail.
Introduction
As the measured depths of deepwater wells increase toward 30,000 ft and
beyond, the wells become significantly more difficult and costly to drill.
Deepwater wells require larger casing programs with much heavier loads than
previously experienced. They also require a completely integrated landing
system that delivers optimum load-carrying capacity to handle the longest and
heaviest casing loads and is constructed in a manner that allows for minimum
time on location. Some operators have opted to run the otherwise very long
casing strings as a liner and tieback to eliminate the need to run a very heavy
load. This adds cost through increased rig time and the additional expense of
the liner and tieback hardware. This increases risk by running an
additional operation (at a critical stage in the well) that could otherwise be
eliminated, and it heightens design concerns associated with compression
loading on the casing-tieback connections. Other operators have opted to
“qualify” conventional equipment, typically comprising a mix of elevators,
slips, and landing strings that were developed independent of one another
through a test program integrating the various individual components. A
technological development was needed that had the capability to support the
very large loads required in deepwater operations, without the following:
• The limitations of conventional slip-based equipment.
• The inefficiencies and health, safety, and environmental (HSE) concerns of
conventional nonslip-based equipment.
• The expense and risks associated with dividing long casing strings
unnecessarily into liner and tieback arrangements.
• The investment of time and expense trying to “prove out” conventional
equipment.
The Landing and Slipless Technology (LAST) System2,3,4,5 was developed and
meets all criteria specified by the operator for the Thunder Horse
deepwater-drilling and completion program on the drillship Discoverer
Enterprise. The profiles of the 5½- and 6⅞-in. landing strings are shown in
Figs. 1 and 2, respectively. The performance properties are detailed in
Table 1.
BP has been using the Discoverer Enterprise to conduct drilling operations
in the central Mississippi Canyon region of the Gulf of Mexico for 1½ years.
This rig is equipped with latest-generation equipment, including dual-derrick
operations with a 2,000,000-lbf-load rating. The Thunder Horse project consists
of several wells more than 20,000 ft deep in water depths of more than 6,100
ft—all of which are shown graphically in Fig. 3—in relation to other
extended-reach wells in the industry.
Several experiences and lessons were documented during the extended field
use of this new system. One well in particular was recently drilled and
experienced one of the heaviest loads in the deepwater Gulf of Mexico. The
maximum actual hookload encountered during operations was more than 1,700,000
lbf. A wellbore schematic of this well is shown in Fig. 4.
© 2005. Society of Petroleum Engineers
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History
- Original manuscript received:
2 June 2004
- Revised manuscript received:
12 May 2005
- Manuscript approved:
22 May 2005
- Version of record:
15 June 2005
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