Claims can be found in technical literature for using Mono Diameter Expandable Liners in deepwater applications. In a technical review of the existing Mono Diameter Expandable Liner systems by various vendors, it is concluded that Mono Diameter Expandable Liner can be considered for using as a drilling liner if certain prerequisites as discussed in this paper are met. Further, the product can be used in a brown field development scenario, where no pore pressure surprises are expected. In any case, once drilling to target has been achieved, the product must be covered by a conventional casing. Proper risk evaluation before running in the hole is recommended, given the high per day costs associated with the deepwater wells. On the other hand, if the product has to be used for deepwater pre planning and casing design purposes, substantial increase in strength (collapse & burst of the pipe) will be required, without which the product will not qualify industry standard casing design criteria’s at the basis of design level. From design perspective, one time or multiple mono diameter expandable liner extension are the same and the key issue to address in using this product is meeting the collapse pressure requirements.

Statoil drilled 7 deepwater wells, including one sidetrack, on the Norwegian Continental Shelf from 2007 to 2009. The semi-submersible rig Transocean Leader was used for these drilling operations. All the wells were drilled and abandoned in a total of 460 days, some 135 days ahead of schedule. Gas and/or condensate were discovered in 6 out of these 7 wells. The wells were all drilled with higher efficiency compared to previous deepwater wells drilled on the Norwegian Continental Shelf. The water depth for the wells ranged from 950 m to 1350 m. In the planning phase, the proposed well designs were challenging. However, continuous improvement in drilling performance and risk management were achieved through comprehensive and systematic work in the multi-disciplinary project team of geologists and drilling engineers. Additional contributing key factors to success were good cooperation and planning between the offshore and onshore project team including personnel from the rig contractor and service companies. In the planning phase, early identification of technical challenges and solutions were discussed. Key learning from international deepwater projects in StatoilHydro and other operators were also highlighted. The geological and pore pressure prognosis for all the wells were quite accurate compared to the measured values during drilling and logging. This paper describes how deepwater exploration wells were planned and successfully completed with Transocean Leader. Good teamwork between offshore and onshore contributed to this success story.

TX 75083-3836, U.S.A., fax 01-972-952-9435. AbstractSchlumberger has worked collaboratively with Shell U.K. Limited (Shell), BP and Statoil to develop a 3 ¼-in. ultra slim through tubing rotary steerable system (RSS) with the objective of extending the production profile of offshore maturing fields. Through tubing rotary drilling (TTRD) is a very attractive option for enhanced reservoir development at low cost. Current methods use motor bottomhole assemblies (BHAs) in TTRD applications, but these have limitations. The introduction of the RSS will extend the reach of TTRD to pursue more distant targets, enhance production through precise directional control, improve drilling performance, reduce drilling cost, and improve ultra slimhole hydraulics. The tool has entered its field test stage and has two successful downhole runs to date.This paper provides a brief overview of TTRD as a method of sustainable development of mature oilfields (brownfields). A detailed overview of the tool development is given, including the main milestones and a system description. The joint RSS development project is presented as a best practice in industry collaboration and a good example of a collective visionary approach to future brownfield development.