Quantifying Bottomhole Assembly Tendency Using Field Directional Drilling Data and a Finite Element Model

Abstract Predicting the directional tendency of a bottomhole assembly (BHA) is a key element in improving the efficiency of the directional drilling process. Finite element models attempt to represent the detailed physical interactions between the BHA and wellbore while drilling. However, effective use of such models has been hindered by parameters that are difficult to quantify, particularly the strength of the formation and variations in hole gauge. Details of over 6400 BHA runs made in the Gulf of Mexico from 1994 through 1997 were used in a systematic statistical analysis and combined with intelligent use of the tendency models to yield information that is not readily apparent in single runs of the software. This information can then be used as a predictive tool to minimize the effects of the parameter uncertainties, and to isolate and calibrate those variables to which the models are sensitive. From these studies the most representative values for formation stiffness and hole over-gauge were obtained for various areas within the Gulf region. We describe a methodology using this combination of advanced modeling and statistical analysis to provide more reliable predictions of BHA tendency and to give an indication of the conditions where such predictive techniques can be effectively applied.