Method of eliminating conductive drill parasitic influence on the measurements of transient electromagnetic components in MWD tools
AssigneeBaker Hughes Incorporated
InventorGregory B. Itskovich
Life of this patent
Estimating the term…
Abstract
A transmitter on a bottomhole assembly (BHA) is used for generating a transient electromagnetic signal in an earth formation. A receiver on the BHA receives signals that are indicative of formation resistivity and distances to bed boundaries. The transmitter and receiver may have axes that are parallel to or inclined to the axis of the BHA. The transmitter and the receiver are on a tubular on a damping portion of the BHA that includes cuts for attenuating eddy currents. The damping portion may include non conducting material such as a ferrite on the outer surface.
Claims32
An apparatus for use in a borehole in an earth formation comprising:
- (a) a conducting tubular, said conducting tubular having a damping portion for reducing a flow of eddy currents;
- (b) at least one transmitter on said conducting tubular which propagates an electromagnetic field in the earth formation;
- (c) at least one receiver on said conducting tubular which receives a transient signal resulting from interaction of said electromagnetic field with said earth formation;
- and
- (d) a processor which determines from said transient signal a resistivity of said earth formation.
A method of drilling an earth formation comprising:
- (a) conveying a bottom hole assembly (BHA) into said earth formation, said BHA including a tabular having a damping portion for reducing a flow of eddy currents;
- (b) using at least one transmitter on said tubular for producing an electromagnetic field in the earth formation;
- (c) using at least one receiver on said tubular for receiving a transient signal resulting from interaction of said electromagnetic field with said earth formation;
- and
- (d) determining from said transient signal a resistivity of said earth formation.
Dependencies are inferred from the claim text.