Technical Paper: Integrated Dual-Reamer RSS BHA Contributed to Completion Optimization, Statfjord Field, North Sean

Society: SPE
Paper Number: 175696
Presentation Date: 2015
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Statfjord field, one of the largest and oldest fields operating the the North Sea continental shelf, has been producing since the early 1980s. It has three platforms, Statfjord A, B, and C, with more than 300 wellbores. Formation collapse (in the lower part of Shetland group) below casing/liner shoe in the overburden section on top of the reservoir has posed different challenges in the field. These challenges include problems in running screens and gravel packing in sand reservoirs. To respond to this challenge and focus on improving the drilling efficiency and rig cost savings, the drilling team evaluated drilling and 10 5/8 x 12 1/4-in section reaching the top of reservoir - 10m true vertical depth (TVD) above the predicted top of the Mime formation - with minimum rathole. A standard underreaming bottomhole assembly (BHA) with one ball-drop reamer leaves a 35-m to 40-m rathole below the 9 5/8-in. casing shoe, which induces different issues related to casing reaching bottom, cementing, potential packoffs due to overburder formation collapse while drilling the 8 1/2. in section in reservoir, problems in running screens, and gravel-packing operations. On two previous wells, running screens faced some challenges, and gravel-pack efficiency was compromised. To cope with these technical challenges, and integrated dual-reamer rathole elimination (RHE) BHA was proposed; this would reduce the rathole to 9m. The proposal was accepted by the operator after detailed risk assessment.

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