fax 01-972-952-9435. AbstractA steerable rotary drilling system (SRD system) has been used on several extended reach wells at the Wytch Farm oilfield in southern England.Recently the SRD system successfully drilled the 8½" hole section of the first well ever to have a step out of more than 10km. The record breaking well, M11SPZ/SPY, has a measured depth of 34,967ft [10,658m] and a horizontal departure of 33,181ft [10,113m]. The reservoir section required rotary drilling techniques to be used. Improvements in drilling operations and reductions in cost were made in drilling the reservoir section. This section was geosteered throughout the reservoir with the SRD system giving control of both the inclination and azimuth.The 9 5 / 8 " casing was set from surface to 28,986ft. The SRD system drilled from 29,337ft (MD) to TD at 34,967ft (MD). The SRD system drilled a total of 7,680ft in 44 days (this included a side-track for geological reasons) against the plan of 5,548ft in 49 days. This improvement against the plan was achieved largely by the elimination of the requirement to slide a steerable motor in order to steer the well. Continuous rotation of the drillstring helped reduce drillstring torque and drag and improved hole cleaning. This led to more efficient weight transfer to the bit and allowed higher average penetration rates.