f Understanding Borehole Surveying

There is a great need for cooperation across the disciplines when optimally positioning a well (and future completions) in the reservoir. Geoscience, surveying and drilling professionals gather, process and make use of multivariate data often with a limited understanding of the methods used, the accuracies achieved and the impact of quality. This paper sets out some of the key areas of wellbore surveying, the tools and methods available, the accuracies and the common human errors that can affect the success of the well. It also explains some key areas of cooperation particularly with regard to the propagation of wellbore position uncertainty as it affects target sizing. Geoscientists and drillers can take advantage of probability theory to better define targets with acceptable risk and design fit for purpose survey programmes to achieve shared objectives.