Soultz-Sous-Forets : Main Technical Aspects of Deepening the Well GPK2

Abstract

The well GPK2 at the European HDR site was successfully reentered and deepened from 3876 m to 5084 m depth and fully completed in 104 days (mid February to the end of May 1999). The programme of re-entry included pulling of the existing 3211 m long internal 9-5/8î by 7î casing string, fishing of a submersible pump and some 150 m of 2-3/8î tubing, sealing of a major loss zone and reaming open from 6-1/4î to 8-1/2î in granite (3211 ñ 3876 m). The well was extended to 5048 m in 8 1/2î hole size and again completed with a floating 9 5/8î by 7î casing string. The casing shoe is at 4431 m. A bottom hole core was taken at 5048 - 5051 m depth. The core recovery was app. 40%. A pilot hole in 6 1/4î was drilled from 5051 - 5084 m for in situ stress measurements. The re-entry and deepening of the well GPK2 was accompanied by several technical developments. Metal casing packers were developed jointly by SOCOMINE and MeSy GmbH (patent pending). These packer elements were successfully integrated into the completion of the well. The full weight of the casing string is supported by these elements which are filled with and imbedded in cement. High temperature cementing strategies (up to 170 - 190o C) for the complex saline fluids encountered in Soultz (High Magnesium Resistant Cements) were developed in a cooperation between Schlumberger Dowell (Vechta), SOCOMINE, SII of Houston, Ruhr-University Bochum, BGR Hannover and IFP Paris.