Updating its progress on the Sunrise-Mayel No. 2H natural gas well near Delano, CA, Tri-Valley Corp. reported that it is expanding operations to the upper Shafter-Wasco zone of the McClure Shale formation because the current zone has a significant amount of clay content that can swell and block gas delivery.

The Bakersfield, CA-based company noted that the content of the formation surrounding the 3,100 feet of horizontal wellbore apparently “reduced the effectiveness of the horizontal fracture process,” resulting in the failure to produce at commercial rates at this time. Tri-Valley said it has a better chance to achieve a commercial production rate from the upper zone because analysis shows it has far less clay content.

The new zone will require another horizontal bore. The company said preparing, drilling and fracturing the upper zone is expected to take 90-120 days. Tri-Valley said it plans to return to the first zone tested at a later date after pursuing the more immediate opportunity. The company added that the location also contains three other zones that bring the total to nearly 300 net feet of gas-charged zones.

“We believe that this new location has tremendous potential,” said F. Lynn Blystone, CEO of Tri-Valley Corp. “The Sunrise Natural Gas Project is most intriguing because of the immense amount of gas calculated to be in place in the tight McClure Shale zones from the two discovery and test wells. Enabling the gas to be liberated at commercial rates is an engineering task to deal with the unique fact that California, to the best of our knowledge, has the only producing diatomite formations in the world. However, that production can be prolific.”

Tri-Valley’s 8,300-acre lease covers approximately 6,600 acres of mapped closure that the company speculates may contain a potential 3 Tcf of natural gas in place in all five zones. Data produced by the company on the play show 40% porosity with 70% gas saturation at an average 3.5 ohms for about 80 Bcf per 160 acres.

The company said the Sunrise Natural Gas Project is one of 26 very large, high-impact targets in its TVOG Opus I Drilling Program LP.

In July 2002, Tri-Valley acknowledged that the McClure Shale formation is very dense, noting that it only became possible to produce from the formation after ChevronTexaco and EOG Resources recently perfected a combination horizontal drilling/hydraulic fracturing program (see Daily GPI, July 12, 2002). The company said it would use some of those techniques in combination with its own in the Sunrise-Mayel No. 2.

Discovered in April of 2001, the Sunrise Natural Gas Project has been touted by Tri-Valley as possibly one of the largest onshore finds in more than half a century (see Daily GPI, April 12, 2001).

Tri-Valley currently produces “a couple million” cubic feet of gas a day from California plays, according to Blystone. The company is currently producing gas from outside the city of Tracy (east of San Francisco), Rio Vista (southwest of Sacramento) and on Bethel Island (Northeast of San Francisco). He noted that the company has prospects in Nevada, but they have not been drilled to date.

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