geologists refer to it as "HTD," or hydrothermal dolomite. Others
call it thermobaric or zebra dolomite.
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
of Ontario, Quebec and Newfoundland. 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
are re-evaluating geological and geophysical data bases for Trenton-Black
River potential in eastern Canada's Appalachian front.
tool kit developed to explore for HTD plays in the Devonian and
Mississippian strata of western Canada and 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
of pipeline infrastructure in Eastern Canada — and the proximity
to large North American markets — has also generated renewed interest
in the Ordovician Trenton-Black River play. For a relatively small,
up-front exploration investment, Canadian companies ranging in size
from "start-ups" to large independents are picking up contiguous
blocks of provincial government lands on the scale of hundreds of
thousands of acres.
Field is situated on the shores of Lake Erie in southern Ontario,
and Talisman's green pump jacks dot the countryside — in farmyards,
beside lakeshore cottages and even inside the loop at the Leamington
Race Track. Soil berms fringed with evergreens provide visual relief
for residents and cottagers.
Energy of Calgary has unlocked the key to producing the heterogeneous,
hydrothermal reservoirs of the Trenton-Black River. Since acquiring
majority interest in the Goldsmith/Lakeshore field in late 1998,
Talisman has drilled 100 horizontal wells, extending the field to
the northwest and southwest, under the shores of Lake Erie — some
of these wells extend 5,000 meters under the lake, and include multi-lateral
arms off existing horizontals.
way, Talisman has broken Canadian records for the longest horizontal
and multi-lateral horizontal wells.
Field is 14 kilometers long, and varies in width from less than
400 meters to 1,200 meters. Since its discovery in 1985 the field
has produced five million barrels and three bcf of gas. Production
hovers around 700 barrels per day and 1 mmcf per day of gas. Estimated
remaining reserves are in the order of two million barrels and 1
bcf of gas.
government regulations stipulate that oil cannot be produced offshore;
if a well encounters oil, it must be abandoned. Talisman, however,
operates offshore, currently producing about 20 mmcf per day (net)
of natural gas from Silurian-age clastic and reef reservoirs.
As Talisman chased the
Trenton-Black River trend to the southwest, it came to the shores
of Lake Erie. An extensive grid of 2-D data confirmed that the collapse
graben structures containing the productive Sherman Fall member
of Trenton-Black River trend extended offshore, under the lake.
Talisman commenced an ambitious horizontal drilling program to tap
the riches under Lake Erie. Designed to cut across the collapse
grabens characteristic of southern Ontario's Trenton-Black River
play, the horizontal wells provided maximum exposure to the reservoir,
increasing chances of success and production rates.
of all of this science, there's always a surprise because the reservoir
is very heterogeneous," said Bob Bonnar, Talisman's exploration
manager for Ontario and Appalachia. "The critical risk is lack of
wells, Bonnar said, increase the chance of success (COS) from approximately
30 percent to 90 percent.
"On a full
cycle basis, the COS of commercially viable wells increases to about
70 percent with horizontals," Bonnar added. It costs, on average,
$C 2.5 million to drill a horizontal well at the Goldsmith/Lakeshore
a lot of geosteering involved in these wells," said Gerry Waugh,
a development engineer with Talisman. "The reservoir is compartmentalized,
so you can find virgin pressures in infill wells."
that one-third of the oil production comes out of fractures, and
two-thirds out of the matrix.
can't get to the matrix without fractures," he said, adding that
production from the fractures comes on hard and fast, then drops
off dramatically, perhaps by 60 percent. That leaves you with a
long-life producer that is draining the matrix porosity.
production from fractures poses a bit of a challenge," Bonnar explained.
"You have a horizontal treadmill with production ramping up and
then dropping off quickly."
the past five years, Talisman developed new drilling technologies
and introduced proven technologies from Alberta to Southern Ontario.
With the long-reach horizontal wells, the height to length ratio
of the borehole becomes critical — in other words, the wells are
drilled to roughly 850 meters true vertical depth before they turn
the corner, drilling horizontally for an additional 3,000 to 4,000
with methods to keep weight on the bit and to reduce friction while
drilling — he tried roller bearings strapped to the outside of
the drilling pipe and now extols the virtues of biodegradable vegetable
oil. "We probably use more canola oil than McDonald's restaurants,"
Talisman exported its exploration expertise, drilling technology
and proven track record in the Trenton-Black River to New York state.
In a number of corporate transactions (totaling $US 250 million),
Talisman's wholly owned subsidiary Fortuna Energy purchased 55 mmcf
per day of natural gas production and facilities, and 115 bcf of
reserves in upper New York. Talisman now controls in excess of 400,000
acres of prospective lands in New York's Finger Lakes district.
whose team works New York's Trenton-Black River from Calgary, calls
this the "early days" with respect to his team's success south of
the border. Additionally, he points out that this is still a relatively
new play concept for New York. However, Talisman reported that the
first two of its four wells drilled in 2003 reported test rates
of 2.4 mmcf per day and 10.4 mmcf per day.
team is poised to prove that it's got the "right stuff" to unlock
this complex HDT play in the Trenton-Black River of New York state.
the New York border, in nearby Quebec, Calgary-based Questerre Energy
is preparing to drill Sainte Sophie #1, its first test into the
Trenton-Black River play. Questerre currently holds more than 700,000
acres of exploration acreage in the St. Lawrence Lowlands, situated
between the cities of Montreal and Quebec City. The acreage is held
in 16 permits, and is grouped into six permit groups for work commitment
Sophie #1 will be drilled to 2,300 meters at an estimated cost of
$C 2.1 million. The lease is prepared; Questerre is waiting for
a rig that's currently drilling gas injection wells at the Saint
Flavien gas field, located about 100 kilometers to the northeast.
Drilled by Shell Canada in the 1970s, Saint Flavien produced 5.7
bcf of natural gas from the Ordovician Beekmantown formation before
being converted to a gas storage facility.
the 1980s and 1990s, several operators explored for the Trenton-Black
River and the deeper Beekmantown formations in the St. Lawrence
Lowlands. At that time, conventional wisdom involved drilling the
highest, central parts of the horst blocks on the carbonate platform;
conventional wisdom also involved avoiding faults that were viewed
as dangerous conduits for produced water. The result of this exploration
phase was a series of dry wells with little or no HTD reservoir
facies. However, most wells that tested the autochthonous carbonate
platform — including many of those drilled for mineral exploration
— encountered non-commercial amounts of natural gas in the Ordovician
and in shallower units.
Sophie was never drilled, because it was so heavily faulted," explained
John Brodylo, Questerre's exploration manager. Brodylo intends to
drill right down the side of a wrench fault, into a collapse or
sag feature. Sainte Sophie #1 will test a structural low that is
seismically mapped over 31 square kilometers. According to Brodylo,
this structure could contain an upside resource potential of 650
of these collapses or sags — often described as "negative" flower
structures — are trans-tensional or strike-slip faults that are
deeply rooted in the basement. Hydrothermal, high pressure brines
move up these faults: When the fluids hit porosity layers — usually
high energy grainstones, packstone and wackestones — they move
laterally, preferentially dolomitizing the carbonate rock.
is using Talisman's exploration analogs in southern Ontario and,
more recently, keying in on their gas discoveries in New York.
brings a unique Western Canadian perspective to Appalachia gained
during the exploration for HTD reservoirs in northern British Columbia,
and has re-interpreted 3,000 kilometers of trade, proprietary and
public domain 2-D seismic data.
a pretty multi-faceted approach," said Brodylo, a geologist, as
he described combining the seismic data with public domain aeromagnetic
data, cores, well logs and outcrop work to identify the major trans-tensional
fault systems that create reservoir rocks and traps in the St. Lawrence
is still a plum to be picked," said Michael Binnion, Questerre's
president, who cited several fiscal drivers that attract him to
- Royalty rates of
10 percent on daily production less than 3 mmcf per day, and 12.5
percent on production thereafter.
- 15 percent cash back
- Proximity to the
TCPL gas pipeline and to a large industrial base in the St. Lawrence
Lowlands between Montreal and Quebec City.
- Natural gas consumption
in Quebec averages 200 bcf.
- Opportunities for
bit of a paradox," Binnion said. "Storage reservoirs get valued
on a rate-of-return while producing reservoirs get devalued on depletion."