DETERMINING ANISOTROPIC RESISTIVITY
First Claim
1. A method to determine the vertical resistivity of a subsurface formation, comprising:
- providing a downhole logging tool having a plurality of spaced antennas, at least one of which is a transverse antenna, at least two of which are tilted antennas, and at least two of which are axial antennas;
obtaining measurements involving the transverse and/or the tilted antennas of the downhole logging tool;
forming voltage ratios using the measurements;
forming conditioning factors by raising the voltage ratios not involving the transverse antenna to some power, wherein the sum of the exponents of the conditioning factors equals one;
computing a ratio using at a voltage ratio involving a transverse antenna and the conditioning factors; and
determining the vertical resistivity of the subsurface formation using the computed ratio.
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Accused Products
Abstract
The present disclosure relates to a method to determine the vertical resistivity of a subsurface formation. A downhole logging tool having a plurality of spaced antennas, at least one of which is a transverse antenna, at least two of which are tilted antennas, and at least two of which are axial antennas is provided. Measurements involving the transverse and/or the tilted antennas of the downhole logging tool are obtained. Voltage ratios are formed using the measurements, and conditioning factors are formed by raising the determined voltage ratios not involving the transverse antenna to some arbitrary power. The sum of the exponents of the conditioning factors preferably equals one. A voltage ratio involving the transverse antenna is multiplied by the conditioning factors, and the vertical resistivity of the subsurface formation is determined using the resulting ratio.
17 Citations
20 Claims
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1. A method to determine the vertical resistivity of a subsurface formation, comprising:
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providing a downhole logging tool having a plurality of spaced antennas, at least one of which is a transverse antenna, at least two of which are tilted antennas, and at least two of which are axial antennas; obtaining measurements involving the transverse and/or the tilted antennas of the downhole logging tool; forming voltage ratios using the measurements; forming conditioning factors by raising the voltage ratios not involving the transverse antenna to some power, wherein the sum of the exponents of the conditioning factors equals one; computing a ratio using at a voltage ratio involving a transverse antenna and the conditioning factors; and determining the vertical resistivity of the subsurface formation using the computed ratio. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12)
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13. A system to determine the vertical resistivity of a subsurface formation, comprising:
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a downhole logging tool having a plurality of spaced antennas, at least one of which is a transverse antenna, at least two of which are tilted antennas, and at least two of which are axial antennas; and a processor capable of; forming voltage ratios using measurements involving the transverse and/or the tilted antennas of the downhole logging tool; forming conditioning factors by raising the voltage ratios not involving the transverse antenna to some power, wherein the sum of the exponents of the conditioning factors equals one; computing a ratio using a voltage ratio involving the transverse antenna and the conditioning factors; and determining the vertical resistivity of the subsurface formation using the computed ratio. - View Dependent Claims (14, 15, 16, 17, 18)
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19. A system having a computer-readable medium having a set of computer-readable instructions encoded thereon that, when executed, perform acts comprising:
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obtaining measurements involving the transverse and/or the tilted antennas of a downhole logging tool; forming voltage ratios using the measurements; forming conditioning factors by raising the voltage ratios not involving the transverse antenna to some power, wherein the sum of the exponents of the conditioning factors equals one; computing a ratio using a voltage ratio involving a transverse antenna and the conditioning factors; and determining the vertical resistivity of the subsurface formation using the computed ratio. - View Dependent Claims (20)
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Specification