geologists refer to it as "HTD" or hydrothermal dolomite.
Graham Davies uses the term "thermobaric" dolomite to acknowledge
that high pressures are as important for dolomitization as the existence
of hot, saline fluids.
also uses the term "implosion" dolomite to explain the processes
that created rocks with breccia clasts "floating" in saddle dolomite
crystals. He describes some hydrothermal dolomite fabrics as "ladder
zebras" and "chevron zebras," adding a level of sophistication that
includes a structural descriptor.)
are dramatic fabrics," explained Davies, president of Calgary-based
Graham Davies Geological Consultants. "We're dealing with an extremely
dynamic system that is not only temperature driven, but pressure
the descriptor, this rock is characterized by coarsely crystalline,
high temperature saddle dolomite, and forms the prolific reservoir
trends of the Trenton-Black River that stretch across continental
River fairway — containing the world class Albion-Scipio and Lima-Indiana
oil fields — crosses into Canada where it is virtually unexplored
renaissance, however, is under way in Canada's eastern provinces.
Fueled by a new understanding of the mechanisms that create hydrothermal
dolomites — and the critical role that wrench faults play as conduits
for high pressure, high temperature dolomitizing fluids — Canadian
oil and gas companies too are re-evaluating geological and geophysical
data bases for Trenton-Black River potential.
published by the mining industry indicate the very processes that
generated Mississippi Valley Deposits have, in fact, created the
HTD reservoirs that host commercial accumulations of oil and gas
across North America.
tool kit developed to explore for HTD plays in the Devonian and
Mississippian strata of Western Canada the Northwest Territories,
Canadian E&P firms are tackling Appalachia with new exploration
analogs. Canadian firms familiar with the Rocky Mountain front have
identified both thin-skinned and thick-skinned tectonics in Appalachia
— analogous to leading edge or Triangle Zone geometries observed
in the Rockies — that set up large thrust plays involving the Trenton-Black
Newfoundland is a field geologist's paradise when it comes to teaching
the theories of orogenesis and plate tectonics — very few places
in the world can boast outcrops of oceanic basalts and pillow lavas
juxtaposed against Cambro-Ordovician platform carbonates that have
been thrusted during more than one orogeny.
dolomite reservoirs to the tectonic mix, and geologists get pretty
was one of the proving grounds for plate tectonics, where Appalachia
came together," said Steven Millan, chief executive officer and
chairman of Newfoundland-based Canadian Imperial Venture Corporation
Millan, an AAPG member, walked the coast of western Newfoundland,
studying its geology.
at the time was that these structures were quite complex," he said,
"and the geophysics didn't have the capability of imaging these
years later, seismic data acquisition and processing techniques
have evolved to image thrust belts and, occasionally, to predict
reservoir characteristics (see Seismic
Targets and Gulf Targets) .
CIVC wants to acquire a multi-component, 3-D seismic survey over
the company's 33,000-acre lease on the Port au Port Peninsula. In
addition to the onshore lease, CIVC holds two adjacent offshore
a Calgary-based research scientist with the Geological Survey of
Canada, specializes in the structural geology of the Rocky Mountains
and in the leading edge of deformation, often termed "the Triangle
first looked at seismic data from offshore Newfoundland in 1987
— and what he saw surprised him.
he said, describing his epiphany on that first day, "that's the
20 years later, Stockmal still gets excited by the thin-skinned
and thick-skinned tectonics that he has studied in the Cambro-Ordovician
succession of western Newfoundland. He is currently working on apatite
fission track studies to generate a "thermo-chronology" of the various
orogenies that have affected the geology of western Newfoundland.
of thermal peaks or maxima," he said, "have helped us to constrain
the structures and the time of their emplacement."
Port au Port acreage was configured parallel to the strike of the
Round Head Thrust Fault — Millan believes the fault acts as both
a conduit for hydrothermal fluids and for oil moving out of the
oil kitchen. In fact, the Round Head Thrust carries the carbonate
platform and underlying basement to surface. The entire stratigraphic
section is repeated, under the thrust sheet.
Hunt Oil and PanCanadian Energy (now EnCana) tested this deeper,
underlying carbonate platform — situated at approximately 3,400
meters — with the Port au Port #1 well.
encountered several reservoirs.
On an extended
production test, the zone flowed a total of 5,012 barrels of oil
and 9.2 mmcf of natural gas over a nine-day period. The reservoir
showed no signs of pressure depletion.
Port #1 is not on production; to date, the well has produced a disappointing
22,000 barrels of oil — it's been plagued by many problems, including
casing integrity issues, calcium carbonate fines introduced into
the reservoir while drilling through a lost circulation zone (Millan
describes this as an underground "cave" or karst) and reservoir
plugging due to very saline, produced water.
CIVC farmed into the Port au Port acreage by virtue of drilling
two sidetrack wells to Port au Port #1. The first sidetrack encountered
non-commercial quantities of hydrocarbons; the second sidetrack
flowed at 195 barrels of oil per day and 1.2 mmcf per day of natural
gas, with no water.
EnCana have exited the play; CIVC is now the operator.
poked a hole to prove a geological concept," Millan said. "They
were surprised to get oil."
to Millan, Hunt and its partner intended to prove the geological
concept prior to testing a large Ordovician structure situated offshore.
also is optimistic about the chance of success at his next location
in the Port au Port Peninsula. At an estimated drilling depth of
3,400 meters and a cost of $C 5 million, the well will be located
on 3-D seismic data and situated close to the Round Head Thrust
Fault, increasing the chances of finding a HTD reservoir.
to Phonse Fagan, a geophysical consultant with Newfoundland's Department
of Mines and Energy, Port au Port #1 was the first well in western
Newfoundland ever drilled on seismic data, albeit a regional grid.
moving into the next exploration cycle with small companies taking
all of the seismic and well data that are released (by the government),"
2002 licensing round in the Great Northern Peninsula of western
Newfoundland was propelled by the release of 300 kilometers of 2-D
seismic data to industry. Two seismic programs were acquired during
the 1990s in Daniel's Harbour-Parson's Pond area, situated some
150 kilometers to the north of the Port au Port Peninsula. Interpretation
of the seismic data illustrates both thin-skinned and thick-skinned
tectonic features extending over a 100-kilometer-long fairway.
Langdon, the vice president of exploration of Calgary-based Contact
Exploration, is animated when he talks about the petroleum potential
of western Newfoundland.
is a publicly traded junior E&P company that focuses on "front-end"
exploration in Eastern Canada and internationally. The company's
strengths, according to Langdon, lie in identifying geological opportunities,
picking up large land spreads, acquiring and interpreting seismic
and attracting larger companies to drill the prospects.
2002, Contact Exploration acquired three exploration licenses from
the government of Newfoundland, totaling 160,000 acres onshore western
Newfoundland. Two of the permits are located in the Middle Ordovician
St. George Group fairway at Daniel's Harbour-Parson's Pond. This
"inversion" fairway is equivalent to the Appalachian fold-and-thrust
belt of western Newfoundland.
back as 150 years ago, the residents of Parson's Pond gathered oil
from surface seeps for local usage. Mining test holes and 27 shallow
wells have produced a total of 6,000 barrels of oil from this area.
The deepest well, located on the north shore of Parson's Pond, was
drilled to 1,302 meters before it collapsed and was abandoned. The
well contained 44 degree API oil, but didn't test any of the structures
delineated by modern seismic acquired in the mid- to late-1990s.
spudded Parson's Pond #1 in late January, using a water rig to drill
the surface hole. Once the surface casing is set, Contact will switch
to a continuous coring rig. With a price tag of $C 1 million, the
company intends to drill the slim hole test to about 1,200 meters,
targeting the leading edge of a shallowest thrust in the allochthon.
The reservoir is a deep-water carbonate facies, believed to be dolomitized,
with high amplitude seismic reflectors.
allochthonous carbonate sheet sits at 2,000 meters drilling depth,
and the underlying autochthonous carbonate platform at about 2,500
at the leading edge of an imbricate sheet in a partially eroded
Triangle Zone, Langdon hopes that this 1,200 meter-target may have
enhanced porosity due to thrust-induced fracturing. Seismic data
to the west and offshore, Langdon says, illustrate a well-preserved
Triangle Zone wedging into the foreland basin.
carbonate targets in the allochthon and autochthon lie within the
oil window, he added. The source rock is a deep-water carbonate
that also acts as a vertical and lateral seal.
Pond #1 well will test a 30-square-kilometer feature that is seismically
mapped. Contact estimates that the structure could contain about
100 million barrels of recoverable oil.
from Newfoundland, Langdon completed his doctoral thesis on the
geology of western Newfoundland. "I would love to be involved in
the first great discovery in western Newfoundland," Langdon said.
"That's my dream."
permit at Daniel's Harbour-Parson's Pond was picked up in December
2002 by a consortium of Canadian and American E&P firms: Canadian
firms Deer Lake Oil and Gas and 554568 Alberta Ltd., and American
partners East Resources and Ammonite Corporation. The consortium
paid the equivalent of $C 10 per acre — which represents a work
commitment to the Newfoundland government — to hold the 35,000-acre
block for five years.
Skip Hobbs, president of Ammonite, has been involved in this particular
play in western Newfoundland for more than 20 years. He's conducted
geological field work in the Great Northern Peninsula and has studied
the lead-zinc mine at Daniel's Harbor, where hydrothermal brines
altered the Ordovician host rock, creating zebra dolomites and collapse
breccias and precipitating economic deposits of galena and sphalerite.
is a sleeper," he said. "We realized that we had light gravity oil
with trap sizes that could approach the Albion-Scipio Field and,
with the thrusting, could be repeated. We know the petroleum system
is there — it's just a matter of putting enough holes in the ground
to find it."
takes guts," he added. "The industry just doesn't have the guts
to do onshore frontier exploration."