Back in 1916, a weather map was generated by the state of Texas measuring the temperature 41/2 ft (1.4 m) above ground level. If one subscribed to the theory that the temperature over a large accumulation of hydrocarbons is slightly cooler than that of the surrounding area, the best place on that map to drill would have been in an area centered in Panola County in East Texas.

Had that been done, the East Texas oil field would have been discovered 17 years earlier than it actually was.

To think that the US National Weather Service might be as useful a library for oil and gas exploration as the data libraries of the major geophysical contractors sounds like an extreme view. But for Lloyd Fons, senior technical consultant for TAP (Thermal Anomaly Production), this view has consumed the better part of his career.

Fons went to work as a logging engineer in 1948. Early in his career he began to notice that whenever a well was TD'd above a pay zone, the bottomhole temperature was less than what the area's average gradient indicated that it should be. Once the well had been drilled through the pay zone, provided there were no deeper pays, the bottomhole temperature was higher than the gradient.

He continued to monitor this phenomenon throughout his career, and in 1980, started his own company. Relying on experience gained by interpreting some 150,000 wells plus available log library data, he documented gradients for most of the producing areas of the US. "Using those gradients and the bottomhole temperature of a well, you can determine if there are deeper hydrocarbons because the temperature is cooler than the average gradient value or if there are bypassed hydrocarbons because the temperature is hotter than the gradient," said Ed Banaszek, manager of operations and senior geologist for TAP.

The actual cause of this temperature anomaly is not known, but theories exist:

* The oil/water interfaces within the pore spaces of a reservoir form countless immiscible barriers which retard convective transfer of thermal energy;
* The insulating properties of hydrocarbons as compared to water tend to reduce conductive transfer; or
* An imperfect seal allowing hydrocarbons to migrate creates an alteration zone in iron-rich sediments, resulting in a cooler environment.

Fons began experimenting with other ways to monitor the temperature. He started pounding 5-ft (1.5-m) boreholes into the ground over known fields and found a minor temperature drop (2°F to 5°F). Even an infrared sensor mounted on a car could detect the field.

"So with his bottomhole temperature measurements, 5-ft depth temperature measurements and his surface temperature measurements, Fons felt, 'I've got something for the industry,'" Banaszek said. "And he went out and began knocking on doors."

He's been knocking ever since. Given the industry's conservative nature, coupled with what Fons believes are textbook errors regarding heat transfer, along with a few too many black-box salesmen over the years, the idea has been slow to catch on. But Fons found some seed funding through his long-time friend John C. Thrash, chairman of eCorp., and with Banaszek formed TAP.

Banaszek was already familiar with the technology. In 1997, he was in a group within a large service company that licensed the technology, and he worked with the engineer given the charge of trying to disprove Fons' claims. "If Lloyd went down a road, we went down that road," he said. "If he went offshore, we went offshore." After 6 months of following Fons and copying his techniques, the conclusion was that what Fons said was there was actually there. Any discrepancies were never positive anomalies, meaning that if Fons had missed on a measurement, it wouldn't have resulted in a dry hole.

The point of the group's work went beyond pure curiosity - it was hoped that the new technology would lead to better understanding of the company's potential assets. For instance, temperature measurements over the Opelika Field in East Texas indicated a major westward extension to the field, and recent drilling results have proved this out. Measurements over a field in Myanmar indicated a northwest extension, and comparisons with 2-D seismic data over the field confirmed those results.

The service company's group was disbanded in a merger, and TAP was formed to perform surveys as a service company. The methodology was updated with software and GPS and is still orders of magnitude cheaper and much less time-consuming than a seismic survey.

"It's interesting, I go out and do surveys of 250 miles in the morning and have the answers before breakfast," Fons said. "I've been up in an airplane and done 650 miles. What would 650 miles of seismic cost? It would cost about $50,000 per mile, and with one crew it would take more than 2 years, plus 6 months processing. I can have better answers the same morning I do the job; I'm convinced of that. But how do you tell that to the industry?"

Banaszek hastened to add that geological and geophysical work is still very important to the process since the relationship between the surface temperature anomaly and the depth to the hydrocarbon accumulation is not exact. But he added that the technique is a very useful method for minimizing risk because it can verify the presence of hydrocarbons.

Surveys to date have been performed over the Texas and Louisiana Gulf Coast as well as eastern Colorado; southwestern Nebraska; and the Black Warrior, Narragansett, Taylorville, Midland, Illinois, Fort Worth, East Texas and Michigan basins in the continental US. Additionally, surveys have been conducted in western Canada, the Mann Field in Myanmar, the Carpathian Foredeep in the Ukraine, and the Paris and Aquitaine basins in France.

For more information, contact (713) 497-1392 or tap@ecorpusa.com.

Clarification

In our March issue, I ran a short article about a seabed logging technique that incorrectly implied that Multiwave Geophysical had invented the technology. In truth, EMGS out of Norway, www.emgs.no, developed the SBL technology and has partnered with Multiwave, which is providing the vessel and marine crew.



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