The Explorers 2021: Sidebar: Stirrup/Horseshoe next?

Kay Cashman

Petroleum News

The Stirrup 1 exploration well drilled by Oil Search Alaska in early 2020 had one of the highest flow rates of any Nanushuk single-stage stimulation of a vertical well on the North Slope to date, the company’s Sydney-based parent said April 21, 2020.

Approximately seven and a half miles west of the 2017 Horseshoe 1 discovery well and almost 28 miles southwest of the proposed Pikka unit development, the Stirrup 1 well successfully penetrated the Nanushuk reservoir and encountered an oil column with net pay of 75 feet.

The wellbore was cored, perforated through a single-stage simulation and shut-in for six days to enable pressure build-up prior to testing in which Stirrup flowed at a stabilized rate of 3,520 barrels of oil per day, exceeding company expectations.

Stirrup is a direct analogue to the Horseshoe 1 Nanushuk discovery and as such the company said the new find could underpin a possible standalone Horseshoe development that would follow Pikka development. Or it could represent a low-cost tie-back to Pikka.

The other exploration wells drilled in early 2020 were the Mitquq 1 and its sidetrack Mitquq 1 ST1.

After discovering oil in the primary Nanushuk reservoir, the Mitquq 1 well was drilled into the secondary Alpine C formation where it encountered 52 feet of net hydrocarbon pay, comprising 31 feet of net oil pay and 21 feet of net gas pay. A comprehensive suite of wireline logs, pressure data and hydrocarbon samples were collected prior to the wellbore being plugged back to allow for the drilling of a sidetrack, Mitquq 1 ST1, to appraise the Mitquq 1 Nanushuk discovery.

The sidetrack intersected the Nanushuk and encountered approximately 172 feet of net hydrocarbon pay, including a 29-foot gas cap.

The wellbore was logged and cored and in late March a flow test was conducted with a single-stage stimulation. The test included a cleanup, flow period and a six-day pressure build-up, with the well achieving a stabilized rate of 1,730 bpd.

Located 5.6 miles east of the proposed processing facility for the Pikka development, Oil Search sees the Mitquq prospect as a “high value tieback” to future Pikka infrastructure.

- KAY CASHMAN