Real-time velocity and pore pressure prediction ahead of bit

A method for estimating velocity ahead of a drill bit 208 includes generating seismic waves at a surface from at least two source positions 214 in the vicinity of the borehole 210, receiving seismic waves reflected from a target reflector 212 ahead of the drill bit, determining travel times of the s...

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Bibliographic Details
Main Authors CENGIZ ESMERSOY, BRIAN CLARK
Format Patent
LanguageEnglish
Published 23.02.2005
Edition7
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:A method for estimating velocity ahead of a drill bit 208 includes generating seismic waves at a surface from at least two source positions 214 in the vicinity of the borehole 210, receiving seismic waves reflected from a target reflector 212 ahead of the drill bit, determining travel times of the seismic waves received at one or more receivers 216 in a downhole tool near the drill bit, and inverting the travel times to determine the velocity of the formation ahead of the drill bit. The velocities ahead of the drill bit are transformed into pore pressures using known transforms (eg Hottman-Johnson). The method may be used to provide accurate real-time check-shot data to update pre-drill velocities determined during an earlier surface seismic survey.
Bibliography:Application Number: GB20040015930