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Wellbore Position Errors Caused by Drilling-Fluid Contamination

2001; Volume: 16; Issue: 04 Linguagem: Inglês

10.2118/75329-pa

1930-0204

Harry Wilson, Andrëw G. Brööks,

Geomagnetism and Paleomagnetism Studies

Summary 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 associated 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. The drill collars housing the sensors were inspected but showed no magnetic susceptibility, which led to the suspicion that the problems were caused by magnetic particles suspended in the drilling fluids. Laboratory testing has confirmed the magnetic properties of these fluids, and chemical analysis has verified the presence of iron in significant quantities. Field examples demonstrate the use of a multiple-survey qualitycontrol and correction method for identification and removal of these survey anomalies.