Prediction of Wellbore Position Accuracy When Surveyed With Gyroscopic Tools

Abstract

Summary This paper describes a new method for the estimation of wellbore position accuracies when using gyroscopic tools. The developed method represents a solution to the industry's need for a general and flexible error model which is applicable for all gyroscopic surveying tools and services. The general gyro error model consists of a new set of error terms and a mathematical description of how the different error sources contribute to position uncertainties dependent on sensor configurations and operational modes. The model is suitable for appropriate modeling of most gyro surveying services. The description of the model and the attached numerical examples are demonstrated to be sufficient to implement the model. The model has now been implemented in a number of commercial well planning and survey-management software packages. The paper is a product of a collaborative work within the SPE Wellbore Positioning Technical Section (SPE WPTS), formerly the Industry Steering Committee on Wellbore Surveying Accuracy (ISCWSA).