Reports by LOUISE S. DURHAM
EXPLORER Correspondent

'Geology 101' Gets New Applications
The Tried and True Still Works

'Old-Timey' Geology Pays Off

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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."

Click images to enlarge

Graphics courtesy of Swift Energy

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.

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