Wellbore Position Errors Caused by Drilling-Fluid Contamination

摘要

Recent improvements in magnetic-survey quality control have revealed the presence of systematic azimuth anomalies that affect the calculated trajectories of a significant number of wells. Although these anomalies display some features commonly asso- ciated with drillstring magnetic interference, they cannot be removed by traditional magnetic correction techniques. New magnetic-survey quality-control procedures have identified the problem as an attenuation of the transverse component of the Earth's field, similar to that caused by magnetically permeable material surrounding the magnetometers.