Previous Talks

Wednesday, June 27th, 2007

New Directions in Wellbore Stability Prediction

Steve Willson (BP)


Conventional approaches to wellbore stability have been well documented for some time, yet wellbore instability remains a significant cause of drilling non-productive time. The talk discusses possible causes of this. In deepwater, salt exits and drilling in proximity to salt remain problematical. The geomechanical risks associated with subsalt well construction will be reviewed and comments made as to how these might be included into stability predictions for these wells. Another cause of instability (often severe) arises from bedding-related effects when the well deviation is within 20-degrees of the bedding parallel direction. This often an issue in ERD wells, but can also cause problems in more modestly-deviated wells in areas where the bedding dip is significant (e.g. in down-dip sidetracks to find oil-water contacts). Another area where new wellbore stability understanding is developing is in the important interaction between water-phase salinity in SOBM and the formation, where non-optimized solutions can give rise to worsening hole conditions over time. This can also give rise to hole cleaning problems, a further area where mud hydraulics and stability prediction need closer integration. The talk will conclude with some aspirations for enhanced real-time monitoring of these effects, where well outcomes can most readily be impacted.

Speaker Biography

Steve Willson is the Rock Mechanics Advisor in the EPTG Drilling Team in Houston and the Geomechanics Discipline Technical Authority for Subsurface, Reservoir & Wells. His current primary technical focus is on wellbore stability and various aspects of well-life integrity, particularly in deepwater, sub-salt field developments in the GoM. Steve holds a BSc in Civil Engineering and a PhD in Soil Mechanics from the University of Manchester, UK. He spent 5 years as a geotechnical engineer before joining BP in 1988. Apart from a period of employment as Completions Manager at TerraTek Inc., Salt Lake City, USA from 1992 – 1995, Steve’s career has been spent working various aspects of petroleum geomechanics as part of BP’s Drilling & Completions technology organization.