24/9-4

General

Well 24/9-4 is located 1 km East of the border to British sector, on the northern outskirts of the 24/9-3 Discovery. The main objective of the well was to test the Early Eocene Frigg Formation forming a stratigraphic play in the western part of the block, where the reservoir was interpreted to result from a submarine fan deposition. The primary risk of the prospect was the presence of the reservoir. The prognosed gross thickness of the reservoir sequence was 230 metres with a net/gross ratio of 0.50 at the well location. No secondary targets were identified.

Operations and results

Well 24/9-4 was spudded with the semi-submersible installation Byford Dolphin on 17 April 1991 and drilled to TD at 2208 m in the Late Paleocene Lista Formation. Here, a wiper trip was performed. When back reaming the string stuck at 1864 m. It was not possible to circulate since the hole had packed off. Several fishing attempts were made, but all were unsuccessful, leaving an MWD tool and a CDR tool in the hole. The hole was then cemented to 1733 m. The sidetrack vas kicked off from 1753 m to an angle of four degrees before pulling out at 1842 m. A conventional packed hole assembly vas then run to try to drill to section TD. Drilling continued to 2021m where a viper trip vas performed to ream tight hole sections. Drilling resumed without incident to 2164 m where bottoms up vas circulated before tripping out. The string became differentially stuck whilst pulling out of the hole. After spotting a pill and jarring for several hours a back-off charge vas run leaving a 30 m fish in the hole, which included an MWD tool. Several unsuccessful fishing runs were attempted before running a VSP and E-logs. The well vas then plugged and abandoned at 2164 m.

Well 24/9-4 penetrated the top of the Frigg Formation sands at 1766 m, which was 51 metres deeper than prognosed. It consisted of very fine to fine grained well-sorted very argillaceous sandstone stringer