25/3-1

General

Well 25/3-1 was designed to drill a narrow NNW-SSE trending horst structure on the Utsira High. The main objective for the well was to test the hydrocarbon potential of the Middle Jurassic Vestland Group sandstones, and the Lower Jurassic Statfjord Formation sandstones. The site survey indicated two high amplitude events at two different levels west (135 m MSL) and northwest (180 m MSL) of the proposed well location that could indicate shallow gas.

Operations and results

Wildcat well 25/3-1 was spudded with the semi-submersible installation West Vanguard on 4 July 1989and drilled to TD at 3922 m in Late Triassic sediments of the Statfjord Formation. To assure safe operation in possible shallow gas zones, the interval (198 to 720 m) was drilled as a 17 1/2 " pilot hole before opening to 26" hole. Drilling went on without any serious problems. No shallow gas was encountered.

The Vestland Group reservoir was reached 65 m deeper than expected. The reservoir was thinner than expected, and of relatively bad quality and water bearing. The Statfjord Formation was reached 128 m deeper than expected, and also water bearing. Very weak shows were recorded in two samples from 2165 m and 2170 m in the Balder Formation; otherwise no shows were recorded while drilling. Geochemical source rock screening found very good Type II kerogen (oil) source potential in the Draupne Formation and good Type II-III kerogen (gas + light oil) source potential in the Heather shales and the Vestland Group coals and shales. The well has reached early maturity probably at ca 2700 m, so the Draupne shale is in the very early oil window.

Two cores were cut. Core no 1 was cut from 3112 to 3130 m in the Vestland Group, and no 2 from 3858 to 3876 m in the Statfjord Formation. The RFT tool was run, but due to obstruction in the hole representative pressure points were not obtained. No fluid sample was taken.

The well was permanently