This paper discusses the design and application of the drilling and wellbore stability technology for an extended reach well drilled in the UK sector of the North Sea Central Graben Basin. The use of this technology can provide reservoir and development planners with an alternative means to economically and efficiently develop accumulations which are situated beyond conventional reach of drilling platforms. Very long reach drilling can enable developers to either defer or eliminate the capital spending associated with additional platforms and facilities or subsea development of satellite accumulations.
The paper addresses several areas that include mud weight and mud system, rock mechanics aspects impacting well-bore stability, well path design, drill string, casing and cementing considerations. It gives a detailed discussion of how the safe operating window for the mud weight was predicted from stability analysis and used to successfully drill the South Everest Extended Reach well (SEER T12) to TD. The paper also describes the rock mechanics data, in situ stress and pore pressure analysis, and operational practices trying to maintain the desired equivalent mud weight within the safe operating range.