34/10-13

General

Well 34/10-13 was drilled on a horst block in the eastern part of the Gullfaks Fault Block. The primary objective of the well was to test the sandstone of Early Jurassic age (Statfjord formation). The Secondary objective was Carnian sandstone.

Operations and results

Appraisal well 34/10-13 was spudded with the semi-submersible installation Deepsea Saga on 24 August 1981 and drilled to TD at 3392 m, 76 m into the Carnian sandstone. At 1725 m, the well started to flow. The influx was circulated out with 1.69 s.g. mud. A total of 21.5 days were lost due to a strike after the drilling of the 6" section had been initiated. The well was drilled with spud mud down to 300 m, with seawater gel from 300 m to 893 m, and with gel/lignosulphonate mud from 893 m to TD. The RFT tool stuck at 2882 m during sampling. The tool was left in the hole and the well was plugged back and tested.

First oil shows, typically cut and/or fluorescence on claystone and limestone cuttings, was recorded at 1350 m in the Hordaland Group. The shows were described more or less continuous down to top Statfjord reservoir at 1924 m. When drilling mudstones, limestone and marl in the Lista Formation from 1656 to 1701 m there was oil in the mud. Oil was found from top Statfjord Group at 1924 m and down to at least 2114 m in the Hegre Group where oil was tested on DST. No oil/water contact could be established in the Statfjord sandstone and pressure measurements in the Hegre Group were inconclusive. Shows were recorded on sandstones down to 2450 m. From petrophysical analyses the Statfjord Group had 70 m net pay with 27% average porosity and 24% average water saturation. The Hegre Group reservoir had 16.5 m net pay with average 27.8% porosity and 56% average w