SACRAMENTO VALLEY LIGHTLY DRILLED, POTENTIAL STRONG

One trillion cu ft of gas remains to be discovered in the Sacramento Valley of California even though exploration and production has proceeded there for more than five decades, says Reinhard Suchsland of Dekalb Energy Co. in Bakersfield. Finding the gas will require geologists to expand their minds and horizons, Suchsland told the San Joaquin Geological Society.

May 17, 1993

3 min read

Finding the gas will require geologists to expand their minds and horizons, Suchsland told the San Joaquin Geological Society.

Suchsland, exploration manager for Dekalb's West Coast district, said, "Many of us are continuing exploration and development efforts solely around the edges of production. This is a necessary activity and many good projects are being developed, vet none of these activities in my opinion will give us the trillion cubic feet or so of reserves vet to be found in the basin.

"If you go through the exercise of making penetration maps or dry hole density maps around existing fields, you become impressed with the fact that the basin is largely underexplored. A good part of the remaining reserves of I tcf will need to be found in new areas."

Suchsland tabbed four areas. One is the southern Sacramento Valley near Stockton, where Lathrop gas field was discovered in 1961 and Union Island gas field in 1972. The two fields have produced more than 585 bcf of gas.

"On a productivity per acre basis, Lathrop and Union Island are astounding. We might be able to agree that these and the other local accumulations may be related to the major thrust faults in the area: Stockton, Vernalis, and Western margin,

"If you measure the length of these thrusts, you come up with over 10 townships and less than a handful of recent wells drilled along their extent."

Another area is the Brentwood and Dutch Slough/Sherman Island trend southwest of Rio Vista, described as intersected by at least major fault zones whose extent has not been totally explored.

"How about the north flank of the gorge at Brentwood oil field? Do the dry holes condemn all of the fault blocks productive nearby? And what's the extent of the geophysical information?"

Farther north, Suchsland tabbed the area west of Rio Vista gas field, California's largest gas field, as "one of the most underexplored areas of the basin."

The area of interest is bounded on the east by Rio Vista field and on the west by the Kirby Hills thrust.

"This trend has so few significant penetrations that you can literally draw out an almost 100 sq mile area of undrilled acreage. Many if not all of the horizons productive nearby are present in this area."

Suggesting that depth to target has been the major stumbling block, Suchsland said depths no greater than 12,000 ft ought to be sufficient to evaluate targets. He added that the east side of the cross basin structure also has been underexplored.

Suchsland said the Malton/Arbuckle trend in the northern part of the Sacramento Valley also has been ignored, with Arbuckle gas field the only major accumulation discovered on the trend.

"To the north, the boundary of (Upper Cretaceous) Forbes productivity appears to be related to the Willows thrust and yet we know that the stratigraphy productive in the field is present.

"The only recent drilling has been for (Upper Cretaceous) Kione gas north of Willows and for Forbes gas south of Williams. There is only a scant amount of seismic data in the area, no new released data at all, and less than five exploratory wells that are more than a mile from existing production that were probably drilled with the latest geophysical support."