Systems and methods for EM ranging in oil-based mud

Nearby conductors 306 such as pipes, well casing, etc., are detectable from within a borehole filled with an oil-based fluid. At least some method embodiments provide a current flow between axially-spaced conductive bridges 204,206 on a drillstring. The current flow 302 disperses into the surroundin...

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Bibliographic Details
Main Authors MICHAEL S BITTAR, JING LI, SHANJUN LI, MICHAEL D FINKE
Format Patent
LanguageEnglish
Published 12.09.2012
Subjects
DETECTING MASSES OR OBJECTS
EARTH DRILLING
EARTH DRILLING, e.g. DEEP DRILLING
FIXED CONSTRUCTIONS
GEOPHYSICS
GRAVITATIONAL MEASUREMENTS
MEASURING
MINING
OBTAINING OIL, GAS, WATER, SOLUBLE OR MELTABLE MATERIALS OR ASLURRY OF MINERALS FROM WELLS
PHYSICS
TESTING
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Summary:Nearby conductors 306 such as pipes, well casing, etc., are detectable from within a borehole filled with an oil-based fluid. At least some method embodiments provide a current flow between axially-spaced conductive bridges 204,206 on a drillstring. The current flow 302 disperses into the surrounding formation 304 and causes a secondary current flow 306 in the nearby conductor. The magnetic field from the secondary current flow can be detected using one or more azimuthally-sensitive antennas 212. Direction and distance estimates are obtainable from the azimuthally-sensitive measurements, and can be used as the basis for steering the drillstring relative to the distant conductor. Possible techniques for providing current flow in the drillstring include imposing a voltage across an insulated gap or using a toroid around the drillstring to induce the current flow.
Bibliography:Application Number: GB20110010143