Summary
Novel well completion techniques and exceptional field execution (per Dodson
Completion Performance Database) allowed the six well completions on the
Anadarko operated Marco Polo Deepwater Tension Leg Platform (TLP) project in
Green Canyon (GC) block 608 to be accomplished significantly ahead of schedule.
All six wells (17 frac packs) were placed on production in approximately 168
days (including 14 days lost because of storms) after riser tieback operations
were complete. An operational efficiency of 85%, with weather downtime
accounting for 9% and other lost time accounting for 6%, was obtained during
the completion campaign.
This paper will focus on how the implementation challenges of completing 17
zones in six deepwater dry-tree wells with a 1,000-hp rig were met, and will
highlight a number of concepts and “technical firsts” that can be applied to
other deepwater-development projects.
Background
Anadarko’s Marco Polo deepwater-development project is located in GC block
608 in the Gulf of Mexico, approximately 175 miles south of New Orleans, in a
4,300-ft water-depth(Renfro and Burman 2004).
Field Development. The Marco Polo field was discovered in 2000, and the
project was sanctioned for development in 2001. Six development wells were
drilled in 2002 and 2003 and were temporarily abandoned to await completion
after installation of the TLP in 2004 (Fig. 1). The TLP hull and deck
were installed in January 2004, designed to accommodate a 1,000-hp completion
rig to run riser tiebacks and perform completions. A significant issue for rig
operations is adherence to United States Coast Guard rules. Only 88 persons are
allowed on board the platform at a time.
Geology. The GC Block 608 field is located in the southern portion of the
Marco Polo salt withdrawal minibasin. The depositional model for the field is
restricted basin floor amalgamated sheet fan sand. Moderate to strong aquifer
support was expected, although the potential presence of internal baffles and
barriers introduced uncertainty to the extent of the aquifer support.
The trap geometry was created by salt withdrawal and extensional faulting
because of sediment loading on the eastern side of the salt ridge. The primary
trap consists of a fault-bounded graben dipping away from the salt ridge. The
main faults are west to southwest to east to northeast trending faults that
form the graben. The updip-trap component to the west is salt/sand pinchout.
The graben is further subdivided into separate compartments by additional
faulting (Fig. 2).
Two main fault compartments make up the Marco Polo field. Another graben
fault (downthrown to the northwest and trending in the same direction as the
bounding faults) subdivides the graben into two main compartments designated as
Fault Block I and Fault Block II. The two main compartments are further
subdivided into two additional compartments by faults that are trending
northwest to southeast and downthrown to the west (toward the salt). The four
main producing compartments for the Marco Polo field are designated FB IA, FB
IB, FB IIA, and FB IIB (updip compartments are denoted “A”).
The productive horizons at the Marco Polo field consist of seven
stacked Lower Pliocene sandstone reservoirs: the M10, M20, M30, M40, M50, M60,
and M70. 75% of the reserves are concentrated in the M40 and M50 sands.
Reservoir depths range from 11,000 to 13,500 ft true vertical depth (TVD)
(Fig. 3).
A complete openhole-logging suite was obtained on all discovery and
development wells. Continuous whole core was obtained through both the M40 and
M50 intervals in the GC 608 number 1 ST number 1 wellbore.
Reservoir. Initial reservoir pressures range from 6,700 to 7,600 psi.
Reservoir temperatures range from 115to 122°F. Ambient mudline temperature is
38°F at 4,300 ft water depth. Reservoir fluids are undersaturated
black oils, with API gravities ranging from 30 to 34° and gas oil ratio (GOR)
ranging from 700 to 1,000 scf/bbl. During the exploratory and development
drilling phases, reservoir pressures were measured on nearly all productive
intervals in all wells, and reservoir fluid samples were collected in the main
field pay zones and analyzed (Table 1).
Completion Design Overview
Multiple pay sands, low reservoir temperatures, the requirement to gas lift
the wells, and the deepwater environment drove the design of the Marco Polo
completions. After significant flow assurance modeling and evaluation, dual
barrier risers (with insulating gel in all annular spaces and with a separate
gas lift string terminated in a submudline or packoff-tubing hanger) were
chosen as the upper completion design (Renfro and Burman 2004).
The sandface completion design focused on risk management during completion
operations with the hardware designed to minimize future intervention risk. In
brief, the 17 pay intervals in six wells were developed with multi-zone
selective single stacked frac-pack completions using sliding sleeves with a
concentric-isolation string for zonal isolation.
Multiple chemical-injection points are installed for hydrate, paraffin,
asphaltene, and scale prevention. The installation of technology for
downhole-pressure sensing and distributed temperature along the tubing string
assisted in well surveillance and hydrate prevention (Fig. 4).
© 2007. Society of Petroleum Engineers
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History
- Original manuscript received:
8 July 2005
- Revised manuscript received:
14 May 2007
- Manuscript approved:
29 May 2007
- Version of record:
20 September 2007
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