This paper is a case history of the drilling of well C3 iron, the Statfjord ‘C’ platform, currently the world record in Extended Reach Drilling. The horizontal reach is 6086 m (19968 ft) and the measured depth 7250 m (23787 ft), with a sail angle of 80 degrees in the 12 1/4" hole section. This paper will concentrate on the important aspects of well planning, such as well profile, torque, drag, hole cleaning and surveying, and how the work was executed. Introduction The Statfjord-field was discovered in 1973. Based on the knowledge and experience at that time, it was expected that it would be possible to drill wells with a sail angle of up to 60 degrees in this area. This resulted in the establishment of three platforms with approximately 5 km separation. These 60 degree boundaries around each platform resulted in a horizontal reach of approximately 3000 meters at reservoir depth. The northern part of the Statfjord field, known as North Statfjord, is separated from the main field by a large fault (fig. I). The horizontal distance to North Statfjord is more than 5000 meters, It was planned to develop this part of utilising sub-sea technology. Such a development would cost approximately three times as much as an Extended Reach solution. The 60 degree boundary limit was first broken in 1988 when well B40 was drilled. The B40 well profile differs from the earlier 60 degree wells in that the kick-off point was higher and had a higher build-up rate. Horizontal reach was 3999 meters at a total depth of 5225 m MD. The inclination in the 17 1/2" section was 60 degrees and the sail angle was 67 degrees in 12 1/4" section. In 1989, well C10 was drilled and completed within 99 days. The drilling of this well was presented at the SPE Drilling Conference in Amsterdam, March 1991. This successful well had a horizontal reach of 5003 meters and a sail angle of 76 degrees in the 12 1/4" hole section. Total depth of this well was 6200 m MD. The importance of an optimum well profile was well demonstrated when drilling B40 and C10. The well profile has a great influence on torque/drag and hole profile has a great influence on torque/drag and hole cleaning. Based on the experience gained from C10, well C3 was planned and drilled with an additional horizontal reach of 1000 planned and drilled with an additional horizontal reach of 1000 meters (Fig.2). P. 75
fax 01-972-952-9435. AbstractThe value of multi-lateral well technology is increasing for the Statfjord field. This first cased multi-lateral well was drilled from the last vacant slot on the three Statfjord platforms. At the same time, limiting the production decline is increasingly dependent on successful drainage of remainiig oil pockets by WII1 drilling.This paper presents a case histo~covering the drilling and completion of the multi-lateral well C-23 on the Stadjord field. The well was drilled with two horizontal branches in the Brent reservoir, 1765 m and 2394 m long respectively. The two horizontal wellbores both penetrate the Tarbert and the Ness formation in the same direction, with a distance between each branch of only 80 m. Both laterals have 7" cemented liners in the reservoir. The lateral has been perforated in the Tatbert formation using a snubbing unit.The following list outlines tie main issues that will be described in the paper: q The commercial and technical just~lcation for drilling a multi-lateral well on the Statfjord field and the tectilcal requirements in each lateral.q Key issues in the planning phase. q The importance of establishing a dedicated team together with the service companies covering all disciplines.q The drilling phase, focusing on general well design, well profile, drilling technology (including the use of a rotary steerable system), running and cementing of 9 5/8" and 7" liners, as well as time schedule.q Design and requirements for the junction at 2376 mMD. Special emphasis will be put on the most critical phases, incIuding the solid whipstock exchange and re-establishing communication to the main bore.q Running and cementing the 2421 m long 7" liner in the lateral, and the use of a proprietary tough cement.q Completion design and production strategy.
This paper is a case history of the drilling of well C3 from the Statfjord 'C' platform, currently the world record in Extended Reach Drilling. The horizontal reach is 6086 m (19 968 ft) and the measured depth 7250 m (23 787 ft), with a I sail angle of 80 degrees in the 12 114" hole section. This paper I will concentrate on the important aspects of well planning, I such as well profile, torque, drag, hole cleaning and survey-I ing, and how the work was executed.
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