A New Wellbore Position Calculation Method

Abstract

Summary A method for combining multiple wellbore surveys to obtain a single, composite, more accurate well position is described. Established methods for defining the wellbore position and its associated uncertainty rely on 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. When a modern wellbore is constructed today, each section may be surveyed for position many times with one or more magnetic, gyroscopic, or inertial survey instruments. By statistically combining the wellbore positions obtained from all 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 that of any of the constituent surveys. The major benefits of this technique is facilitating drilling smaller targets at greater distances, allowing new wellbores to be drilled in closer proximity to existing wellbores while maintaining accepted safety clearance rules, and improving reservoir delineation.