New Real-Time Anticollision Alarm Improves Drilling Safety

A critical concern in directional drilling is ensuring the avoidance of collisions while drilling on multi-well locations. Collision avoidance planning is ordinarily carried out prior to well spud and is therefore valid only to the planned trajectory. Once drilling commences, deviation from the plan invariably occurs which may not only increase subsurface collision risk, but also compromise the ability to maintain adequate quality control of rigsite anticollision computations in an often stressful and demanding drilling situation. New high performance, multi-user computer systems at the rigsite provide the capability for clear anticollision analysis in real time without the need for hand computations. In this paper we describe a unique computer application which performs traveling cylinder calculations automatically in real time. The present bit location, computed from survey and depth measurements, is shown on a rigfloor color display along with the trajectories of the offset wells. Position uncertainties for both the current hole location and all the offset wells are computed and plotted as error ellipses on the screen. In addition, the application has a look-ahead feature which projects the trajectory beyond the current bit depth, and a Smart Alarm is triggered if any of the offset wells come within a user specified alarm proximity. Field data are shown which illustrate the effectiveness of the technique. The alarm has been designed to give early warning of potential collision situations. As a result, it improves safety and quality control at the rig and helps avoid the environmental damage that can result from well collisions.