Record extended reach well drilled off Tierra del Fuego

Total Exploration Production has successfully drilled an extended reach well, with a 6,253-m (20,510 ft) horizontal departure at a depth of 1,700 m (5,576 ft), in the Atlantic Ocean offshore Tierra del Fuego (Fig. 1 [39472 bytes]). Total believes, according to its Energies publication, that this well is a record extended reach well on the South American continent.

The well was drilled from a jack up rig positioned over the northern Hidra production platform in 30 m of water. About 85% of the oil reserves have already been produced from Total's Hidra field. Total had two alternatives to tap these additional reserves: build a new platform and drill three horizontal wells or drill a long reach well from the current platform. The recoverable reserves in the field, however, did not justify the cost of a new platform.

The long reach well required a horizontal departure twice as great as that of a classic horizontal well (Fig. 2 [21831 bytes]). Despite the risk and cost, this solution offered an economic advantage because it could be implemented in 2 months. This quick time frame would bring the wells into immediate production and recoup the investment in less than 4 months by allowing production from an existing platform.

Moreover, once Total engineers mastered the technology of extended reach drilling with a large horizontal departure, the technique could be used to develop other reserves, including those in Tierra del Fuego, which may otherwise remain unproduced.

Before this well was undertaken, no deviated wells with a departure of more than 2,700 m had been drilled in Tierra del Fuego.

Solid organization was instrumental in the drilling of this well. The first step for Total's engineers was to gather all available information on previous projects of this nature. Then the drilling teams spent several months working on similar well sites to learn how to handle such a long drillstring-the total well length was 6,982 m. The well was drilled to total depth in just 51 days.

The well inclination was angled away from vertical at a rate of 0.1°/m until the hole angle reached 80°. This inclination angle was just steep enough to allow the drillstring to slide under its own weight. Although the oil-based mud provided some degree of lubrication, torque and drag were still problems. A key piece of equipment in this operation was a top drive power system with a torque capacity twice as high as normal to overcome some of the torque and drag problems.

This year, Total plans to drill two additional extended reach wells offshore Tierra del Fuego. Next year, several other extended reach wells are expected to be drilled from onshore sites there to access new offshore reserves.