Prediction of Wellbore Position Accuracy When Surveyed With Gyroscopic Tools

Abstract

Abstract This paper describes a new method for estimation of well bore 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 modelling of most gyro surveying services. The error propagation mechanisms are chosen to be identical to those in the ISCWSA’s MWD error model (SPE 67616), which has become an industry standard during the last five years. Thus future standardisation and software implementation are simplified. The description of the model and the attached numerical examples should be sufficient to implement the model. The paper is a product of a collaborative work in ISCWSA (Industry Steering Committee on Wellbore Surveying Accuracy).