Increasingly
sophisticated E&P tools have proven to work near-miracles in
much of the oil patch — but high-tech applications usually carry
a correspondingly high price tag that would break the budget of
the increasing numbers of small companies dotting the landscape.
This doesn't
have to be a "bad thing."
In fact,
some of the bigger entities with deeper pockets purposely eschew
the glitzy hydrocarbon-finding tools in certain instances, instead
using old-style, tried and true methods.
Such an
approach is people intensive, but the payoff can be substantial.
Here are
two examples of how old technology is succeeding via new applications.
'Old-Timey' Geology
Pays Off
Swift
Energy has amassed an impressive track record using "Geology 101,"
i.e., paper maps, cross sections, etc., to find new production at
Lake Washington field in Louisiana's Plaquemines Parish.
The water-drive
field, which is located around a shallow piercement salt feature,
was first discovered in the 1930s, and most of the drilling activity
occurred in the 1950s and 1960s. The operating agreement between
operator Exxon and partners Gulf and Shell required unanimous consent
for each project, which proved to hinder development, minimizing
the amount of data collected over the years.
When Swift
purchased the field in 2001, the deal included no seismic, a few
maps of isolated reservoirs where the most recent operator saw some
opportunity, and computerized historical production data from Exxon.
Development
proceeded in rapid-fire fashion following the Swift acquisition.
In fact, the company has drilled close to 100 wells (averaging 500,000
barrels recoverable per well) with a 79 percent success rate, increasing
reserves from 7.7 million barrels to 43 million barrels — a huge
payoff using basic, nuts 'n' bolts geology.
"We started
mapping at 1,500 feet and did multiple level maps," said Bill Moody,
director of exploitation and development at Swift, "and probably
made 150 old-timey structural cross sections.
"We did
a lot of this on the copy machine, shooting logs down using reducing
machines and basically built a framework of seismic lines from cross
sections," he said. "We hooked all the faults up and made fault
plane maps on all the faults, and we overlaid the subsurface structure
maps in base fashion where we could see what the contours did as
we went deeper."
Deep Success
Using the
computerized production data from Exxon, the team of geologists
and engineers did a lot of material balance work to make sure the
fault blocks mapped were large enough to handle the production that
had come out of them.
If not,
then it was back to the drawing board until the geology better fit
the production data.
"Once we
started drilling wells," Moody said, "the more we drilled, the more
we liked it."
There are
70 productive sands in the Lake Washington area, according to Moody,
and Swift has completed in 33 of these thus far, often encountering
new sands by going deeper than the intended target.
"We've
been steering the bit as much as we can along the salt face and
taking it a bit deeper each time, using directional drilling techniques,
which the previous operator hadn't used," Moody said. "This is how
we came into the F Sand, which had not been seen productive in the
field before, and now it's the most productive sand."
With the
exception of a couple of wells, the company's drilling program to
date has concentrated on depths no greater than 6,000 feet. The
Swift team is gearing up to implement the second stage of development,
targeting intermediate depths between 6,000 and 12,000 feet.
To do so,
they'll go high tech, using 3-D seismic data, which doesn't come
cheap in the shallow inland-water environs.
The plan
is to acquire 3-D data to get a better image of the salt face going
down and help to better develop the field away from well control.
Moody says it's possible there will even be another round of shallow
development where the 3-D shows additional opportunities.
Although
most of the Lake Washington production is oil, there is a substantial
amount of associated gas being produced. A portion of the gas volumes
is used for gas lift, which is necessary because of the low energy at the shallow depths being plumbed in the initial development stage
of the property.
Cecil's Log Plainly Is Gassy
Gas
lift is a common practice in old Gulf Coast fields. For many of
these fields, the availability — or lack thereof — of field gas
to run compressors, pump engines, etc., is all that stands between
production and shut-in.
A number
of longtime operators who are picking over old fields are finding
not only little stringer gas sands to meet field needs but substantial
pay zones as well, using what appears to be a rather simplistic,
relatively inexpensive well log that's been around for more than
30 years.
It's a
cased hole log comprising three tools — gamma ray, density and
neutron curves (GDN) — and it's found a lot of hydrocarbons for
a lot of folks since it was initially developed in 1970, according
to veteran exploration geologist Alan Pennington.
In fact,
it's been dubbed the "gas-finding log" by a number of users.
It's also
frequently referred to as the "Cecil Eicke log," in deference to
the now-retired founder and owner of United Surveys (US) in Richmond,
Texas, who developed the log with help from an electronics engineer
at US, who continues as an on-site expert today.
"We've
run it for everybody, both big and small," said Eicke, who spent
his entire career in the wireline business. "There was a lot of
trial and error in developing it, and we've done a lot of fine tuning
over the years."
The GDN
log appears deceptively simple: the sand shows up on the gamma ray,
and gas presence is indicated by a reversal and ultimate crossover
of the neutron and density curves. An old open hole log for comparison
and verification helps but is not essential, according to Eicke.
Where the
old log without the density-neutron curves showed interesting places,
the GDN lets the owner go in for relatively little expense to verify
gas, Pennington noted.
Operators
have used the US log for a variety of applications over the years
to:
- Locate
gas behind pipe to aid in recompletion evaluation.
- Evaluate
abandoned wells for possible re-entry.
- Help
define depleted zones and moved water contacts in producing zones.
- Detect
oil zones in some instances.
"It's as
good a tool as any in the industry, cased-hole-log-wise, to indicate
reserves remaining in the well," said Richard Lee, managing member
of Masters Petroleum. "It also shows a gamma ray reversal where
a zone has been swept, so you know to stay away.
"We've
used it on close to two dozen wells up and down the Texas Gulf Coast
with incredible accuracy," Lee said.
"For a
company like Masters that makes its living re-exploring mature oil
and gas fields," Lee said, "a log like this is invaluable."
Good for
Oil, Too
There are
a number of more sophisticated, expensive cased hole evaluation
logs available, such as the pulsed neutron, or thermal neutron decay
(TDT) logs. For those companies who need the information a TDT provides,
such as porosity and water saturation, it's likely worth the expense.
In fact,
a petrophysicist with a major may be inclined to take this path
and bypass the GDN because it is qualitative and not quantitative.
"The GDN
doesn't tell you porosity, but it does tell you there is gas effect,"
Pennington said. "It was developed for a niche market that doesn't
need TDT or pulsed neutron and can get along fine with a less expensive
version.
"It's the
difference in a Mercedes and a Ford Taurus," he said. "Both get
you there; it just won't be quite as in style."
Like a
number of other operators who have used the GDN, Lee noted it's
a head-scratcher as to just how the log works. Pennington says,
simply, "nobody runs a cased hole density log like they do."
Although
known and valued primarily as a gas finder, the GDN is also a pretty
nifty tool to find oil.
"We've
run this log on 30 or 40 old wells the last couple of years," said
Richard O'Donnell, president Houston Petroleum Company, "and we've
found a lot of both oil and gas with it.
"With oil,
it doesn't necessarily give a crossover," O'Donnell said, "but you
can see where the density pulls in and the neutron pulls out. When
they get close, or begin to kiss, it indicates you've got some hydrocarbons
there."
It worked
for Lee.
"We recently
ran the log in a well at Red Fish Reef, where we saw a possible
oil zone overlooked by Exxon," he said. "We perfed, and it came
in flowing 200 bopd at 1,350 psi and no water.
"We've
experimented with a lot of different logs," Lee said, "and I find
it amazing that with all the very expensive, sophisticated tools
out there, it's the old tried and true proven technology that's
so often the best."
Pennington
offers a personal endorsement for the myriad oil finders picking
over innumerable old fields today:
"You should
run this log in every well before you plug it," he said. "If you
can find a little gas sand that will make a few hundred million,
that's a lot of money — and this thing really has made a lot of
money for a lot of people."