Abstract
Since 1967, TOTALFINAELF has been actively involved in deep water drilling operations but the saga really began in 1976 with the building of the PELERIN drill ship which broke a first water depth world record by drilling a well in 925 m of water offshore Algeria. This was followed by another outstanding performance in 1982 when TFE drilled the first well in a water depth greater than 1500 m (1714 m, in the Mediterranean sea). Following these campaigns, there was a lull in deepwater drilling that lasted about ten years.
However, in 1994 the exploration Offshore Angola on the bloc 17 re-activated the group drilling activity in deep waters. Since this time, 62 wells have been drilled in water depth ranging from 500m to 2851 m in Angola, Congo, Gabon, Equatorial Guinea, Nigeria, Brazil and in the GOM. The majority of those wells are challenging exploration or appraisal wells, for which core have been cut in nonconsolidated sands, sand control completion have been run and DST have been performed. Twelve wells are development wells, which have involved installation of subsea completions. All types of rigs have been used from moored semisubmersible, old DP drill ships, to new built semi-submersible and drill ships including two types of dual derrick units.
Those drilling performances leaded to the production start up of the Girassol field by 1400m of water on the 04th of December 2001 with some wells producing over 30,000 BOPD. It will shortly (summer 2002) lead to the start up of the Aconcagua gas field, which is the deepest field ever completed (2200 m of water).
This huge amount of deep water well operations brought a lot of data and experience, the purpose of this paper is to show what type of drilling and completion performance one can expect according to the type of well to be drilled. The paper will compare drilling operations durations achieved for dry hole wells with appraisal wells, including heavy data acquisition program. The type of rig will be analysed with in particular the gain one can expect by using dual derricks drilling rigs. Alternative solutions to conventional Subsea drilling such as surface BOP stack, slender wells will also be discussed.
