Application of Risk Analysis Methods to Subsurface Well Collisions

Abstract

Summary Subsurface separation criteria have evolved empirically over the years. They still are based largely on untested assumptions about safety factors, comfort values, and survey tool accuracy. A mathematical analysis of the probability of collision combined with a decision tree describing the consequences provides a method of risk evaluation. The mathematics can be simplified under certain special assumptions, allowing key features of the problem to be illustrated. A flow chart of the directional-drilling tolerance setting procedure shows how the methods described can be used in daily well-planning operations.