fax 01-972-952-9435. AbstractSince their introduction in 1997, rotary steerable drilling systems have delivered significant gains in drilling efficiency. In addition to this fundamental benefit, these systems have enabled more challenging wells to be drilled at low risk with a wide range of other advantages, including improved well placement, etc.Continuous rotary drilling operations do however bring with them certain challenges which must be considered before rotary steering is selected for use. These include instantaneous penetration rate, specifications of rig rotary equipment, casing or drillpipe wear, stress on the drillstring, loss of drilling power through wellbore friction and drilling dynamics.Using high powered drilling motors, traditional performance drilling has been applied since the early 1990's to improve penetration rates by applying high power and consistent operating parameters directly to the drillbit. This has however been limited to straight holes or the most basic of directional profiles.A system has been developed which integrates a specially designed high power drilling motor within a high speed rotary steering assembly. By using this new system: • many of the challenges of continuous rotary drilling are mitigated, • more complex wells benefit from the advantages of traditional performance drilling, • existing drilling envelopes can be extended to further improve field recovery. This paper discusses the engineering design of the complete system, including the specially designed motor and high speed rotary steering system. The paper then goes on to discuss specific applications where the system should be considered for use, illustrated with results from real examples.

The development strategy for Qatar's offshore Al Shaheen field involves a large number of extended-reach horizontal wells with total depths (TDs) ranging from 20,000 to 40,000 ft measured depths (MDs). Since the 2005 field development plan was initiated in May 2006, about 3 million ft of productive footage has been drilled. Drilling performance and tool reliability have been consistent challenges but have been improved to levels that enable the drilling of most sections in one bottomhole assembly (BHA) run to TD. This paper reviews the changes made to increase drilling efficiency and to reduce non-productive time, including analysis of drilling performance for each hole section and subsequent improvement strategies. Discussions encompass the systems and processes contributing to the improvements.