7/11-8

General

Wildcat well 7/11-8 is located on the Cod Terrace of the North Sea, between the Mime Field to the South and the 7/8-3 Discovery to the North. The primary objective was to test Late Jurassic sandstones of the Ula Formation. Secondary objective of the well was to test continental sandstone reservoirs of Triassic age as seen in some nearby wells. Rocks of early and middle Jurassic age were thought to be absent at this location. The well was planned to be drilled to 4550 + 100 m, approximately 730 m into the Triassic to penetrate a strong intra Triassic reflector.

Operations and results

Well 7/11-8 was spudded with the semi-submersible installation Treasure Scout on 22 September 1983 and drilled to TD at 4750 m, almost one km into Triassic sediments. Gumbo problems and problems with the seal assembly were experienced when running the 13 3/8" casing. The well was drilled with seawater and pre-hydrated bentonite down to 620 m, with KCl polymer mud from 620 m to 3673 m, and with a bentonite/lignosulphonate/barite/lignite mud system from 3673 m to TD.

The well encountered water bearing Triassic sandstones directly underlying lower Cretaceous shales. The Ula Formation was thus missing. No shows or other hydrocarbon indications were seen in the well. The intra Triassic marker was found at 4605 m in a shaly sequence.

One core was cut in the Triassic sandstones from 3725 to 3743.95 m. The entire core consisted of greyish red to moderate brown sandstones, with occasional bands of greenish black to greenish grey sandstones. The RFT tool was run to obtain pressure points in the Triassic sands. The pressure data indicated a water gradient of 1.09 g/cm3 and no fluid sample was taken

The well was permanently abandoned on 12 December 1983 as a dry well.

Testing

No drill stem test was performed