Well Bore Collision Avoidance and Interceptions – State of the Art

Abstract

This paper highlights key knowledge that was shared at the SPE Collision Avoidance and Well Interceptions Applied Technology Workshop held in Inverness, September 2012. It has been written to raise awareness of critical issues concerning well bore collisions and interceptions.

Planning to ensure well collisions do not occur during drilling is a complex and demanding task which is often not given the high priority it requires in drilling programs. Assumptions are made of the validity and accuracy of historical data which is unfounded. Conversely, planning well interceptions when required in operations such as relief wells / drainage intercept wells requires a sound working knowledge of wellbore positioning technologies and techniques.

Well bore interceptions and proximity placement are becoming critical applications for development of some reservoirs, specifically tar sands and coal bed methane. Well bore collision avoidance is entering the everyday skills requirement of drilling engineers as they plan more infill wells and more cluster (pad) drilling. Ultimately, demonstrating knowledge of the bore hole position during the whole drilling process is becoming more of a regulatory requirement that demands greater understanding by the drilling engineering community and drilling / asset managers. Are drilling engineers trained, competent and adhering to procedures designed to manage the intricacies of well bore surveying requirements as applied to collision avoidance and well interceptions?

The workshop covered the topic under the following headings:

– Survey database integrity.
– Collision avoidance management.
– Practical directional drilling.
– Relief well design.
– Interception techniques.

The outcome of the workshop was to emphasize that wellbore collisions must be treated as high risk events with serious consequences that must be managed through systematic survey management procedures. Borehole position errors are a critical input to subsurface modeling and can have a major impact on field economics. Several members of the workshop committee are also members of the SPE Wellbore Positioning Technical Section that has published two SPE papers providing the industry with the ellipse of uncertainty error models commonly referred to as the Industry Steering Committee on Wellbore Survey Accuracy (ISCWSA) models.