chnical challenges of deepwater development cross all disciplines and
all phases of a deepwater fields life. It starts with the explorers, who interpret
subsalt images to locate potential fields hidden below thousands of feet of salt
at depths reaching the current limits of our rigs. It continues with the drillers,
who are drilling faster and deeper and collecting critical data to help subsurface
engineers appraise the size of the field. Additionally, they provide a stable well-
bore that enables the completion engineer to complete the well with little-to-no
formation damage and possibly stimulate the formation with reliable downhole
equipment. Finally, subsea and facility experts step in and install subsea and sur-
face kits (depending on whether the completion is wet, dry, or hybrid) designed
to handle a range of the fields conditions.
Long-term production from deepwater fields has been a challenge and will
become even more challenging with respect to being able to produce wells
at high rates initially and recover the maximum reserves. Producing beyond
primary depletion will require the use of artificial lift (e.g., gas lift or electrical
submersible pumps in the well or at the mudline) and reservoir-pressure main-
tenance (either natural or artificial) and, possibly, enhanced oil recovery.
As we continue to explore in deep water, new horizons at depths never before
completed are demanding development of new ideas and new technologies. As
professionals working in the oil industry, we need to continue working together
to come up with new ways to develop these deeper high-pressure reservoirs; we
need to keep that can-do attitude.
Deepwater Exploration and Production additional reading available
at the SPE eLibrary: www.spe.org
SPE 110089 Calibrating the Mechanical Properties and In-Situ Stresses Using
Acoustic Radial Profiles by Colin M. Sayers, SPE, Schlumberger, et al.
IPTC 11282 Planning a Deepwater Well for All Seasons: Platina-2, a
Combined Appraisal/Development Well by Ian Brown, BP plc, et al.
SPE 112472 Meeting the Flow-Assurance Challenges of Deepwater
Developments: From Capex Development to Field Startup by M.M. Jordan, SPE,
Nalco, et al.
SPE 111629 Techniques for Monitoring the Recovery of Deep, Cold-Water
Habitats Following Physical Disturbance From Drilling Discharges by Daniel O.B.
Jones, National Oceanography Centre, et al.
Deepwater Exploration
and Production
TECHNOLOGY FOCUS
52
JPT JUNE 2008
JPT
Karen Olson, SPE, is the Completion
Engineering Team Leader for the
Paleogene Performance Unit (Lower
Tertiary) for BP. She has worked in
the oil industry for more than 20 years.
Previously, Olson was with the Western
Company of North America and then
Mobil E&P working in west Texas, the
Gulf of Mexico (GOM), and Norway.
For the past 7 years, she has worked
for BP, first in Norway and now in the
deepwater GOM. During her career,
Olson con centrated on trying to under-
stand and optimize the productivity of
both gas and oil wells for major projects.
She has written and presented many
SPE papers and has been a discussion
leader at SPE workshops and forums.
Olson has served on the SPE Annual
Technical Conference and Exhibition
(ATCE) Stimulation Committee and is
a member of the ATCE Completion
Committee. She also serves on the JPT
Editorial Committee. Olson was the
Completion Cochairperson for the 2004
SPE Asia Pacific Completion Forum
and a Keynote Speaker at the 2007
Hydraulic Fracturing Conference. She
holds a BS degree in petroleum engineer-
ing from Louisiana State University and
an MS degree in petroleum engineering
from Texas A&M University. A high-level review of recent develop-
ment challenges for the deepwater
and ultradeepwater fields in the Gulf
of Mexico (GOM) is presented. How
these challenges were addressed and
how Chevron plans to address even-
more-demanding challenges in the
future are summarized.
Introduction
Operating in all areas of the world
presents many challenges. The GOM,
although a long-established and prolific
hydrocarbon basin, has, over the past 15
or so years, evolved into an arena where
operations challenges have been encoun-
tered in ever-increasing water depths
further from the coast. These challeng-
es include seismic acquisition, drilling
operations, completion operations, sub-
sea operations, production operations,
logistics support, and many more. Fields
are being developed in the GOM that
pose the greatest engineering challenges
that the company has addressed. It is
anticipated that developing resources in
water depths of 10,000 ft will be funda-
mental to the continued long-term suc-
cess of the GOM as one of the worlds
major producing basins.
Challenges
Many of the prospects in the ultradeep-
water GOM have a unique combina-
tion of challenges. The combination of
deep water (to 10,000 ft water depth),
high pressure (>10,000 psi shut-in
pressures), high temperatures (>350°F
bottomhole temperature), problematic
formations (e.g., salt or tar zones), deep
reservoirs (more than 30,000 ft true
vertical depth), tight-sandstone reser-
voirs (<10 md), and fluids with extreme
flow-assurance issues separates many
GOM deepwater and ultradeepwater
wells from deepwater and ultradeepwa-
ter wells in other parts of the world.
As Fig. 1 shows, much of the pro-
spective GOM deepwater exploration
area is in 4,000 to 10,000 ft of water.
Most of this area is in a subsalt envi-
ronment, with salt canopies ranging
from 7,000 to 20,000 ft thick and
target depths ranging from 25,000 to
35,000 ft true vertical depth.
The vast salt zones inhibit deep-seis-
mic resolution, presenting great chal-
lenges in exploration, appraisal, and
development operations. Understanding
the geology associated with the massive
salt and, more importantly, the quality
of imaging below the salt is paramount.
A key technology being developed to
address this challenge is wide-azimuth-
towed-streamer technology. This tech-
nique allows better subsurface imaging
for effective reservoir management and
will dictate well placement and number
of wells required to drain the reservoir
optimally. The true vertical depths of
some deepwater wells are in excess of
34,000 ft. Fig. 2 shows some of the
drilling challenges.
The complex nature of the forma-
tions, combined with the drilling depths
required to reach the target zones, pres-
ents a great challenge to drilling engi-
neers. The complexity is shown in Fig. 3,
which gives a birds eye view looking
down actual wells. The casing program
on the right illustrates a conventional
five-string casing design, which is used
on standard deepwater wells in the
GOM and elsewhere. The casing pro-
gram on the left illustrates a nine-string
casing design, used in development wells
in deepwater high-pressure/high-tem-
perature (HP/HT) fields. This number of
casing strings, required to drill to target
depth, highlights the challenge in achiev-
ing good cement isolation in tight-toler-
ance annuli and HP/HT conditions.
With development wells having been
drilled successfully, the next challenge
This article, written by Technology Editor
Dennis Denney, contains highlights of
paper SPE 113011, Deepwater Gulf
of Mexico Development Challenges
Overview, by Frank Close, Bob
McCavitt, SPE, and Brian Smith,
Chevron North America E&P Company,
prepared for the 2008 SPE North Africa
Technical Conference and Exhibition,
Marrakech, Morocco, 1214 March. The
paper has not been peer reviewed.
Deepwater Gulf of Mexico Development Challenges
DEEPWATER EXPLORATION AND PRODUCTION
Fig. 1GOM salt-canopy distribution.
For a limited time, the full-length paper is available free to SPE members at www.spe.org/jpt.
JPT JUNE 2008
53 54
JPT JUNE 2008
is to complete the wells. Because the
reservoir zones generally have low
porosity (<20%) and permeability
(<10 md), they require fracturing and
proppant packing to produce in com-
mercial quantities. Performing these
operations effectively and efficiently in
a deepwater, deep-well, HP/HT envi-
ronment requires the highest level of
planning and operational focus.
After the wells are completed below
the mudline, the subsea production
equipment is installed. These high-
pressure fields require the use of
15,000-psi wellheads and trees. Many
existing products had to be requali-
fied for the increased demands of the
production envelopes. A process was
adopted that involved rigorous quali-
fication testing of components and of
complete systems to mimic as many
of the conditions encountered in the
field as possible. The size of this equip-
ment is greater than that considered
as standard for subsea developments.
The trees used on the deepwater
HP/HT fields weigh as much as 72 tons,
whereas standard deepwater 10,000-psi
trees weigh approximately 42 tons.
It is imperative that all aspects of the
riser-system design be considered in
the selection of the topside unit, be it a
surface piercing articulated riser, semi-
submersible, tension-leg platform, or
other. If overlooked or not recognized
at the preliminary design phase, it can
have a large effect on the engineer-
ing and construction of the topside
unit. The preferred riser system must
be decided in conjunction with the
preferred topside unit. This consider-
ation is particularly true for s