Abstract: New Developments in Well Planning for Deep and Ultra Deep Water Fields

Cunha, J. C.; Fábio S. N. Rosa; Ivan Alves; J. B. Saliés -Petrobras/E&P

The primary purpose of this paper is to give a highlight on the main well technologies that are now being developed or adapted to be used in the deep and ultra deep water oilfields in Brazil. Among the various new technologies this article will focus on the use of extended reach wells (ERW), multilateral wells, slender wells and the use of light weight drilling fluids.

ERW: Deep water fields have been developed mostly using sub-sea completion, however the use of dry completion with wells producing to TLP or Spar platforms will make the adoption of ERW almost mandatory. These technique will allow the drilling operation of all wells to be performed from one location, with the wells reaching various different points of the reservoir. Even in the case of sub-sea completion, ERW can be used to avoid the costly sub-sea flowlines and certain production problems.

Multilateral Wells: This technology allows the production from two or more horizons with fewer wells, eventually turning non-economic fields into profitable ones with a high impact on those so-called marginal fields. Also multilateral technology can be used in depleted mature fields that were primarily developed with regular wells. For those type of fields, multilateral technology can increase the production and the total recovery.

Slender Wells: Another important alternative for drilling and completion in deep water is the slender well concept, that can be used both in sub-sea or dry completion. The idea consists in changing the well design in order to allow the application of lighter and smaller wellheads, BOP, drilling riser and also drilling rigs. These wells can reach the reservoir with the same wellbore diameter as in conventional drilling, but decreasing the diameter of the previous three phases. As a result, we can extend the use of a rig originally designed to operate in shallow water to use in deep water.

Drilling with Light-Weight Fluids: For the near future, one of the most promising drilling techniques for application in deep water scenarios is the use of light-weight fluids for drilling operations from floating rigs. In this type of drilling, aerated fluids and foam are used to obtain pressure loads inside the well close to formation pressures, or even smaller. Some of the advantages of such technique, already common practice on onshore operations, are higher penetration rates, avoidance of circulation losses and less formation damage problems, which will, especially in low pressure and depleted reservoir, result in larger production rates and smaller stimulation costs.

AAPG Search and Discovery Article #90933©1998 ABGP/AAPG International Conference and Exhibition, Rio de Janeiro, Brazil