31/2-18

General

The purpose of well 31/2-18 was to appraise the structure and oil bearing potential of a fault block in the northern part of the Troll West Gas province (TWGP). The objectives for drilling well 31/2-18 were to evaluate the structure for future development of oil producing wells in the TWGP-North area, and to determine the degree of development required to efficiently develop the oil reservoir in the TWGP-North area. Well 31/2-18A was drilled as a pre-planned sidetrack to Well 31/2-18 in order to evaluate the hydrocarbon potential of the Krossfjord Formation. The primary objective of the sidetrack was to evaluate a seismic anomaly, or "flat spot" which had been identified in the Krossfjord Formation. The location of the anomaly was situated 240 m to the northeast in an up thrown block, adjacent to the original well.

Operations

Appraisal well 31/2-18 was spudded with the semi-submersible installation "Treasure Saga" on 15 September 1992, and drilled to a total depth of 1711 m in the Middle Jurassic Fensfjord Formation. The well was drilled with seawater and hi-vis pills down to 940 m and with KCl/Polymer mud from 940 m to TD.

Palaeocene sand was encountered below base Våle Formation, from 1519.9 m to 1528.8 m. This sand is in direct contact with the underlying Late Jurassic Sognefjord Formation, which was encountered over the interval 1528.8 m - 1642.7 m. Gas was proven all through these sands from top of the Palaeocene sand down to 1571.2 m in the Sognefjord Formation. A thin oil leg was identified, with an oil-water contact at 1582.0 m. Sixteen good RFT pressure measurements, including segregated samples at 1575 m and 1582 m, were taken in one run over the interval 1522 m & 1689.5 m. The interval from 1498 m to 1678.5 m (Lower Rogaland Group including the Palaeocene sand, Sognefjord Formation, and Heather Formation) was cored in twelve cores with 86 100 % recovery.

After running wire line lo