A New Wellbore Position Calculation Method

Abstract

AbstractA method is described for combining multiple wellbore surveys to obtain a single composite, more accurate, well position. Established methods for defining the wellbore position, and its associated uncertainty, rely upon accepting the position obtained from the most accurate survey instrument used in each section of the wellbore. This position is then assigned an uncertainty based on the information from this single survey instrument run. Today, when a modern wellbore is constructed, each section may be surveyed for position many times using one or more magnetic, gyroscopic or inertial survey instruments. By statistically combining the wellbore positions obtained from all of the survey instruments run in a given section of the wellbore a new position, designated the ‘Most Accurate Position’ (MAP), is calculated. The main advantage of the MAP is that its uncertainty is smaller than the uncertainty of any of the constituent surveys. The major benefits of this technique will be to facilitate the drilling of smaller targets at greater distances, allow the drilling of new wellbores in closer proximity to existing wellbores while maintaining accepted safety clearance rules, and improved reservoir delineation.