EP 0793000 A2 19970903 - Method for correcting directional surveys
Title (en)
Method for correcting directional surveys
Title (de)
Verfahren zum Korrigieren von Richtungsmessungen
Title (fr)
Méthode pour corriger les mesures de la direction
Publication
Application
Priority
GB 9509819 A 19950515
Abstract (en)
In a method for determining the orientation of a borehole from measurements of the gravity and magnetic fields within the borehole, the hole azimuth is obtained corrected for sources of permanent, induced and electrically caused magnetic interference. Information on these sources and on the earth's magnetic field is computed as a by product so that in the fullest application of the invention no prior information is required. The method uses several survey measurements to provide the required data for the correction, and provides quality assurance indicators that do not depend on ad hoc rules. The method uses predicted components of the magnetic field (including error components resulting from interference sources as above) and a predicted gravity field vector (allowing for possible motion of the drillstring and survey package during measurement), and adjusts the predicted values on the basis of best fit with the field values from the survey. The updated values are then available for use with the field values from the next survey.
IPC 1-7
IPC 8 full level
E21B 47/022 (2006.01)
CPC (source: EP)
E21B 47/022 (2013.01)
Designated contracting state (EPC)
FR GB NL
DOCDB simple family (publication)
GB 2301438 A 19961204; GB 2301438 B 19990421; GB 9509819 D0 19950705; EP 0793000 A2 19970903; EP 0793000 A3 19980204; EP 0793000 B1 20011004; NO 316336 B1 20040112; NO 961966 D0 19960514; NO 961966 L 19961118
DOCDB simple family (application)
GB 9509819 A 19950515; EP 96303391 A 19960514; NO 961966 A 19960514