Harvesting the Sacramento: long after the Sacramento Basin's natural gas reserves were believed exhausted, seismic-savvy operators are still tapping overlooked multiple pay zones.(3-D seismic )

Publication: Oil and Gas Investor

Publication Date: 01-SEP-05

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COPYRIGHT 2005 Hart Publications, Inc.

The nearly 250-mile-long and 75-mile-wide Sacramento Basin, cradled between the easterly Sierra Nevada Mountains and the westward Coastal Range, boasts a lush alphabet soup of crops, from asparagus to zucchini, as well as world-class wine vineyards.

But hidden beneath this flat, verdant lobe of northern California is also a structural and stratigraphic wonderland of highly folded, faulted and fractured Cretaceous and Eoceneage rocks that would make a geologic Alice do flips. The big subsurface harvest: natural gas.

Due to the play's complex geology and often tricky-to-target fault blocks, however, early operators--armed with only 2-D seismic or no seismic--often had to rely on serendipity for success. "I'd rather be lucky than smart" wasn't an uncommon expression as a producer approached the moment of drilling.

But later on, the application of 3-D seismic technology greatly shifted the odds of success in favor of the basin's producers. At the same time, the major oils began exiting the region in search of bigger hydrocarbon targets. Their belief was that by the late 1980s the Sacramento, which had already given up 8- to 9 trillion cubic feet (Tcf) of gas production, was on its last legs.

Some smaller independents working the basin took a much different view. In fact, one of their number, the head of Capital Oil Corp., contended at the time that there might be as much as 6 Tcf of remaining gas reserves in the Sacramento--in deeper, overlooked and undrilled horizons such as the Forbes formation.

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Several seismic-savvy operators outside the basin also shared this assessment. More importantly, they, too, came to the conclusion that the careful processing and analysis of 3-D seismic data gave independents a high statistical edge in economically drilling up the basin's remaining potential--even at then-low gas prices. Two such independents were Aspen Exploration Corp. and Royale Energy Inc.

Orphan finds home

Founded in 1980, Aspen Exploration Corp. (OTC BB: ASPN), with offices in Bakersfield, California, and Denver, entered the basin in 1996.

"We were attracted to the Sacramento because it...

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