In January 2007, ConocoPhillips completed what is believed to be the first well directionally drilled with casing using wireline retrievable bottom hole assemblies from an offshore installation. ConocoPhillips has considerable experience with this technology in reducing drilling days on predominately vertical land wells in South Texas. It was desired to determine if the same benefit could be realized in the offshore environment; where directional drilling is required. A candidate development well was identified in Norway on the ConocoPhillips operated Eldfisk Bravo platform that could benefit from advantages seen with Casing while Drilling. Two land based tests were conducted to confirm the ability to conduct casing directional drilling in wells similar to those expected in Norway. Simultaneously, a detailed plan for drilling the well in Norway was developed.Two production casing strings (10 ¾-in. and 7 ¾-in.) were successfully drilled directionally through the overburden section on the Eldfisk well. The well had a complex 3-dimensional well path with inclination up to 60°. All running and retrievals of the BHAs was planned to be done with wireline and a purpose-built traction winch system rated to a working load of 40,000 lbs. Once the 7 ¾-in. production casing was cemented, the casing string was converted to a production liner with an expandable liner hanger and the upper section of 7 ¾-in. was retrieved. In all, 10,968 ft of the 13,600 ft well was directionally drilled with casing.

When ConocoPhillips (COP) decided to conduct Casing Directional Drilling (CDD) operations from a platform in the Norwegian Sector of the North Sea, the well design required that the drilled in 7–3/4" production casing string be converted into a liner prior to completing the well. There was a challenge in identifying a liner hanger system that would be suitable for CDD operations; that did not require a running tool; would maintain a full internal diameter (ID) for running and retrieving bottom hole assemblies (BHA's) and would act as a barrier against gas migration over the service life of the well. Expandable technology(1) was identified as a potential solution. Once a service provider was identified, a basis of design was established and testing began. The end result after eighteen (18) months of work was a successful field deployment of a 7–3/4" liner hanger that was drilled in from surface; successfully expanded into 10–3/4" casing; had a load capability of over 440,000 lbs (200 metric tons or MT) and a 5,000 psi (345 bar) gas tight seal qualified to ISO 14310:V0. This paper will describe the development, testing and actual deployment that took place between December 2006 and January 2007. Introduction In the well under consideration, COP wanted to casing directionally drill a long string of 7–3/4" casing to the top of the reservoir, cement the casing shoe, then convert the long string into a liner and retrieve the upper section of 7–3/4" casing. This conversion was required for four main reasons: the completion & stimulation design; future sidetrack operations; concerns regarding Equivalent Circulating Density (ECD) while drilling the 6–1/2" reservoir section; and space constraints within the wellhead system. Conventional liner applications typically involve making up a liner with an integral liner top packer and a specific running tool; attaching the liner to the drill string; then running it into a pre-drilled hole section prior to cementing. However, it was planned to drill this well with casing as the drill string; with the casing string extending from Total Depth (TD) back to the rig floor. Bottom hole assemblies (BHA's) would have to be run through the liner hanger (LH) on wireline; the liner hanger would be picked up at surface and needed to be drilled in to approximately 4,800 ft after which it would need to be set and provide a gas tight seal. Therefore a conventional liner hanger assembly was not believed to be a viable solution. It was also important to ensure that the LH could be set at any depth in the well in the event the casing could not reach TD during CDD operations. As it happened, the casing did reach TD and although the LH was positioned across a 10–3/4" casing collar, this had no detrimental affect on the setting of the LH.