Formation resistivity measurement sensor contained onboard a drill bit (resistivity in bit)
First Claim
1. An apparatus for making measurements of a parameter of interest of an earth formation during the drilling of a borehole therein, the apparatus comprising:
- (a) a drill bit conveyed on a bottom hole assembly for drilling the borehole;
(b) a first electrode carried on an exterior surface of the drillbit for conveying a measure current into the formation; and
(c) a measuring device set in a cavity on the drillbit responsive to (i) the measure current in the first electrode, and, (ii) a voltage of a second electrode with respect to a remote reference.
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Accused Products
Abstract
A method and apparatus for obtaining a resistivity measurement of an earth formation surrounding a borehole in an MWD device uses an electrode for injecting current into the earth formation and an electrode for obtaining a responsive signal from the borehole. The electrodes are located on the drill bit arm or blade. Measured resistivity values are obtained at the location of the drill bit. Measurements can be taken in both oil-based mud and water-based mud environments. Maximum or minimum resistivity can be used to best represent the resistivity of the surrounding formation.
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Citations
12 Claims
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1. An apparatus for making measurements of a parameter of interest of an earth formation during the drilling of a borehole therein, the apparatus comprising:
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(a) a drill bit conveyed on a bottom hole assembly for drilling the borehole;
(b) a first electrode carried on an exterior surface of the drillbit for conveying a measure current into the formation; and
(c) a measuring device set in a cavity on the drillbit responsive to (i) the measure current in the first electrode, and, (ii) a voltage of a second electrode with respect to a remote reference. - View Dependent Claims (2, 3, 4, 5, 6)
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7. A method determining a resistivity of an earth formation during the drilling of a borehole, the method comprising:
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(a) conveying a drill bit on a bottom hole assembly into a borehole;
(b) using a first electrode on an outer surface of said drill bit to inject a measure current into the formation;
(c) measuring a voltage of a second electrode on said drill bit; and
(d) determining said resistivity from a value of said measure current and said measured voltage of said second electrode. - View Dependent Claims (8, 9, 10, 11, 12)
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Specification