The Tried and True Still Works

'Geology 101' Gets New Applications

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."

Image Caption

Bit by bit, putting it together: Coming up with an exploration strategy for Lake Washington involved a lot of "old-timey" work, like piecing together cross sections.
Graphics courtesy of Swift Energy

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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."

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