Determination of formation pressure during a drilling operation
First Claim
1. A method for determining true formation pressure while drilling in an earth formation, using recirculating fluid that flows downward through a drill string and returns to a surface in a void between the drill string and the earth formation that has a portion of mudcake thereon, the method comprising:
- a) providing a measurement device with a probe on the drill string;
b) controlling a mud flow rate to obtain a first measured borehole pressure and measuring a corresponding first probe pressure with the probe wherein the corresponding first probe pressure is the pressure in the earth formation adjacent the mudcake;
c) controlling the mud flow rate to obtain a second measured borehole pressure and measuring a corresponding second probe pressure with the probe wherein the corresponding second probe pressure is the pressure in the earth formation adjacent the mudcake;
d) deriving the true formation pressure from calculating a first ratio from the first and second measured borehole pressures and the first and second probe pressures.
1 Assignment
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Accused Products
Abstract
A drilling operation wherein a borehole can be drilled through earth formations with a drill bit at the end of a drill string, using recirculating drilling mud that flows downward through the drill string, exits through the drill bit, and returns to the earth'"'"'s surface in the annulus between the drill string and the borehole wall, at least a portion of which has a mudcake thereon, and a surface pumping system for pumping the mud to recirculate. Determining true formation pressure, including the following steps: providing a measurement device, having a probe, on the drill string; controlling the mud flow rate to obtain a first measured borehole pressure and measuring, with the probe of the measurement device, as a corresponding first probe pressure, the pressure in the formation adjacent the mudcake; controlling the mud flow rate to obtain a second measured borehole pressure and measuring, with the probe of the measurement device, as a corresponding second probe pressure, the pressure in the formation adjacent the mudcake; and deriving the true formation pressure from the first and second measured borehole pressures and the first and second probe pressures.
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Citations
24 Claims
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1. A method for determining true formation pressure while drilling in an earth formation, using recirculating fluid that flows downward through a drill string and returns to a surface in a void between the drill string and the earth formation that has a portion of mudcake thereon, the method comprising:
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a) providing a measurement device with a probe on the drill string; b) controlling a mud flow rate to obtain a first measured borehole pressure and measuring a corresponding first probe pressure with the probe wherein the corresponding first probe pressure is the pressure in the earth formation adjacent the mudcake; c) controlling the mud flow rate to obtain a second measured borehole pressure and measuring a corresponding second probe pressure with the probe wherein the corresponding second probe pressure is the pressure in the earth formation adjacent the mudcake; d) deriving the true formation pressure from calculating a first ratio from the first and second measured borehole pressures and the first and second probe pressures. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13)
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14. A method for determining true formation pressure while drilling in an earth formation, using recirculating fluid that flows downward through a drill string and returns to a surface in a void between the drill string and the earth formation that has a portion of mudcake thereon, the method comprising:
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a) providing a measurement device having a probe on the drill string; b) using a surface pumping system for controlling the mud flow rate to obtain at least three measured borehole pressures and measuring at least three corresponding measured probe pressures with the probe wherein the corresponding at least three probe pressures relate to the pressure in the earth formation adjacent the mudcake; c) using the at least three corresponding measured probe pressures as a function of the at least three measured borehole pressures to obtain at least three pressure measurement data pair points, and plotting the at least three pressure measurement data pair points; d) fitting a line through the at least three pressure measurement pair data points, extrapolating to a point along the fitted line where the probe pressure equals the borehole pressure; and e) obtaining the true formation pressure which is equal to the probe pressure at the point along the fitted line where the probe pressure equals the borehole pressure. - View Dependent Claims (15, 16, 17, 18, 19)
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20. A method for determining true formation pressure while drilling in a subterranean environment from using recirculation fluid that flows through a drill string and a void between the drill string and the subterranean environment being drilled, the method comprising the steps of:
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a) providing a measurement device having a probe on the drill string; b) providing a drill bit on a the drill string such that the measurement device is approximate the drill bit; c) using a controlling means for controlling a mud flow rate to obtain a first measured borehole pressure and a corresponding first measured probe pressure with the probe, wherein the measured pressures are in the subterranean environment adjacent a mudcake located approximate the void; d) using the controlling means for controlling the mud flow rate to obtain a second measured borehole pressure and a corresponding second measured probe pressure with the probe, wherein the measured pressures are in the subterranean environment adjacent the mudcake; and e) deriving the true formation pressure from the first and second measured borehole pressures and the first and second measured probe pressures, wherein the derived true formation pressure is communicated to a bottom hole assembly. - View Dependent Claims (21, 22, 23)
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24. A method for determining true formation pressure while drilling in a formation, wherein the true formation pressure is determined from using recirculation fluid flowing downward through a drill string and returning to a surface in a void between the drill string and the formation that has a mudcake thereon, the method comprising:
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a) providing a measurement device with a probe on the drill string; b) using a controllable pump with a processor for controlling a mud flow rate to obtain a first measured borehole pressure and a corresponding first measured probe pressure with the probe, wherein the corresponding first measured probe pressure is the pressure in the formation adjacent the mudcake; c) using the controllable pump with a processor for controlling a mud flow rate to obtain a second measured borehole pressure and a corresponding second measured probe pressure with the probe wherein the corresponding second measured probe pressure is the pressure in the formation adjacent the mudcake; d) calculating a first ratio from the first and second measured borehole pressures and the first and second measured probe pressures; and e) deriving the true formation pressure from multiplying the first ratio with a sum of the second measured borehole pressure less the first measured borehole pressure, then dividing by a sum of the first ratio less one.
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Specification