33/9-18 A

General

Well 33/9-18 A was drilled to a structure situated east of the Statfjord Field and south-west of the Tordis Field. The main objective of well 33/9-18 A was to test the lithology of a strong seismic amplitude within the same prospect as drilled in well 33/9-18. Well 33/9-18 A is a sidetrack from well 33/9-18.

Operations and results

Exploration well 33/9-18 A was spudded on 21 December 1994 with the semi-submersible installation Deepsea Bergen and drilled from kick-off at 1974 m to TD at 3597 m in the Late Jurassic Draupne Formation. The 12 1/4" hole section was drilled with KC1/PAC POLYMER and KCl mud system to prevent bit balling. No shallow gas was recorded.

Parts of the 12 1/4" section have anomalous resistivity data. The MWD data records from 3070 m to TD are missing, due to washout, lost signal, stuck pipe and MWD tool lost in hole. No wireline logging was performed. 1 core was cut in the Draupne Formation the interval 3397-3404.5 m. No fluid samples were collected. Bit balling was observed several times and a lot of pills were pumped to prevent balling, but minor effects were observed. Dyno-CC-115 (soap) pills showed best results. Drilling from 3145 m to 3397 m had to stop after 49 m due to bad weather. Drilling continued after 7 days stop and the flow rate was increased to maintain a pressure of 280 bar. At TD the actual pressure was nearly 100 bar less than the "theoretical" pressure. This pressure drop was caused by wash out between two drill collars. Got differential stuck at 3512 m when pulling out of the hole. Cut the string at 3382 m to get free. Extra cost related to logistics is estimated to approximately 3.3 mill. NOK. The well was plugged and abandoned after being stuck for 83.5 hrs.

The well has been interpreted to penetrate large slump/slide blocks consisting of the Brent Group, the Dunlin Group and the Statfjord Formation which are deposited within the Draupne Formation. The strong seismic