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Tight
Gas Sands, Intensive Resource Development Is A Key Concept
Intensive Resource Development (IRD) is the
integrated application of a series of complementary resource
assessment, reservoir characterization and field development
technologies. IRD is particularly applicable to
low-permeability reservoirs with thick but discontinuous pay
zones.
IRD can encompass:
- Natural fracture identification
technologies to detect high-productivity sections
- Well logging technologies that reliable
distinguish between gas and water
- Multi-zone completion technologies
- Well testing technologies to establish
drainage volumes, communication and anisotropies
Begun in the 1980s, techniques have
evolved with major research investments by the Department of
Energy, Gas Technology Institute and others and from
operators drilling wells and applying the lessons learned.
Three field/basin examples illustrate different aspects of
IRD.
Southern Piceance Basin, Colorado. The Williams
Fork (Mesaverde) Formation in the Rulison Field is thick,
containing up to 135 Bcf per section but sands are very
lenticular and discontinuous. Drainage area is very limited.
These thick but discontinuous sections led operators early
on to think of wells as vertical rather than areal
reservoirs. Pressure data showed minimal
depletion/communication through successive waves of down
spacing, from 80s to 40s to 20s and now down to 10 acres in
selected areas. In the initial 10 wells drilled on 10-acre
spacing, pressure testing detected partial depletion in only
six of 98 individually tested sand bodies. Reserves for the
initial 10-acre wells are about 2 Bcf per well, in the range
of earlier wells developed on larger spacing.
Northwestern Greater
Green River Basin, Wyoming. The Lance Formation
is the major producing horizon in the Jonah and Pinedale
fields. A unique geologic setting involving the local uplift
of the over-pressured Lance section and a series of lateral
sealing faults has resulted in large volumes of gas in
place, from 250 to 300 Bcf per section. Development there
reveals a history of successive improvements in the
completion/ stimulation approach. Before 1992, |
stimulation treatments used relatively small
amounts of proppant (80,000 to 200,000 lb) and cross-linked
water-based gel or carbon dioxide foam. Production was
noncommercial. Between 1992 and 1995, treatments grew larger,
average of 550,000 lb, and used nitrogen foam. Initial
production was much higher, but rapid declines occurred.
Beginning in 1994, a new approach using water-based fluids
with borate cross linkers and a modified perforation technique
designed for flexible treatment of multiple intervals began to
be used. Flow rates were still good, but declines are much
shallower leading to higher reserves. Reserves have increased
from 1 to 2 Bcf per well in the early 1990s to 5 to 10 Bcf per
well currently. Development has begun on 40-acre spacing, and
it may go even lower.
Eastern Wind River
Basin, Wyoming. The largest Fort Union/Lance
Formation natural gas field in the Wind River Basin is Waltman/
Cave Gulch, on the northeast flank of the basin. Discovered in
1959, the Cave Gulch Unit produced only modest amounts of gas,
less than 5 Bcf and only a few MMcfd until Barrett Resources
began applying IRD techniques in 1994. The Bureau of Land
Management estimates the Fort Union and Lance formations in
this area contain an average 885 ft of net pay within a
4,000-ft gross interval, holding from 450 to 680 Bcf per
section. With IRD, wells are completed in as much of the
vertical sand interval as possible, averaging between four and
five stimulation stages per well with about 200,000 lb of sand
per stage on average. Production rates and reserves are much
higher, averaging about 9 Bcf per well versus 5 Bcf per well
in earlier shallower Fort Union only completions.
Excerpted from "Tight Gas Sands
Development—How To Dramatically Improve Recovery Efficiency,"
GasTIPS, Winter 2004, p. 15-20. View online
www.netl.doe.gov/scng/
explore/ref-shelf/gas-tips/
GasTIPS-Winter04.pdf. First in a three-part
series in GasTIPS.
New
ChevronTexaco Center of Research Excellence at CSM
In late 2003, the Colorado School of Mines (CSM)
and ChevronTexaco announced plans to establish a new Center of
Research Excellence (Center). The center will develop advanced
technologies to improve interpretation of subsurface geology
through computer modeling. ChevronTexaco will provide R&D
funding to establish the Center of Research Excellence, which
will draw upon expertise and resources within the CSM
Department of Geology |
and Geological Engineering. The center will
focus on developing integrated technologies. ChevronTexaco
employees will directly participate in the program and the
company will provide real-world geological data from oil and
gas fields from around the world. ChevronTexaco also plans to
provide additional research investments as expanded programs
develop with CSM. The center's co-executive directors will be
John Hebberger, research manager at ChevronTexaco Exploration
and Production Technology Co., and Chuck Kluth, distinguished
scientist at CSM.
Prior research centers or partnerships
formed by ChevronTexaco and academia include the University of
Tulsa (production fluid flow, December 2001) and the
University of Southern California (interactive smart oilfield
technologies, August 2003). PTTC takes pride in that two of
its regional programs (Rocky Mountain and West Coast Regions)
emanate from universities selected for Centers.
Full ChevronTexaco press release at
www.chevrontexaco.com/
news/press/2003/2003-
10-16.asp.
GeoScience World
Comprehensive Online Earth Science Resource
Six leading earth science societies and one
institute are launching GeoScienceWorld (GSW), a comprehensive
electronic research resource. GSW will deliver online the
aggregated journal content of both its founding organizations
and many other not-for-profit and independent earth science
publishers. The collection will feature full text searches
across the aggregated journals. GeoRef, the premier
bibliographic database for the geosciences, will be fully
integrated.
Founding organizations include: American
Association of Petroleum Geologists, American Geological
Institute, Geological Society of London, Geological Society of
London, Mineralogical Society of America, Society for
Sedimentary Geology, and the Society of Exploration
Geophysicists.
Other societies or independent publishers
still have the opportunity to become part of GSW. A free trial
period for potential subscribers is anticipated prior to the
launch of paid services later this year. Charter online
subscriptions rates will be announced this summer.
View GSW's website
www.Geo
ScienceWorld.org for
more information. |
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