The Tofkat and Putu puzzle

Alan Bailey

Petroleum News

During an April 21 presentation to the Alaska Geological Society on the recent Nanushuk and Torok oil discoveries, Josef Chmielowski, a geoscientist with Alaska’s Division of Oil and Gas, commented on the drilling of the Tofkat No. 1 well and sidetracks by Brooks Range Petroleum in 2008 and the drilling of the nearby Putu No. 2 well and sidetrack by ConocoPhillips this winter. Chmielowski has been using seismic data recently released to the public to assess the strategies for drilling various wells associated with the Nanushuk/Torok play.

Brooks Range reported oil at several horizons in the Tofkat wells. However, although a Tofkat unit was formed, the company conducted no further drilling in the prospect and ConocoPhillips eventually acquired the leases, adding the leases to the Colville River unit.

Chmielowski showed a seismic section for the Putu/Tofkat area. There is a clear, relatively shallow seismic amplitude anomaly that Conoco appears to have targeted with the Putu wells. That anomaly seems associated with a Nanushuk trend linked with the Pikka/Horseshoe oil discovery. And ConocoPhillips has announced an oil find with the Putu well.

A plot of the trajectory of the Tofkat well shows the well missing the seismic anomaly by a horizontal distance of about 800 feet. So, did Brooks Range fail to identify what could have been a large oil find?

Not so, Chmielowski said. He understands that Brooks Range was aware of the seismic anomaly but had to drill from a location on the east side of the Colville River, a location that prevented directional drilling into the relatively shallow Brookian target. The Tofkat well was, in fact, targeting deeper prospects in Alpine and Kuparuk sands. The company had intended to return to drill into the shallow prospect but, following funding and unitization issues, that drilling never happened, Chmielowski said. - ALAN BAILEY