Method and apparatus for ultrasound velocity measurements in drilling fluids

• US 20060101916A1
• Filed: 11/21/2003
• Published: 05/18/2006
• Est. Priority Date: 12/31/2002
• Status: Active Grant

• Current Assignee: Schlumberger Technology Corporation (SLB)
• Original Assignee: Schlumberger Technology Corporation (SLB)
• Inventors: Griffiths, Roger, Pabon, Miquel
• Granted Patent: US 7,418,865 B2
• Time in Patent Office: Days
• US Class Current: 73/597
• CPC Class Codes: E21B 47/085 using radiant means, e.g. acoustic, radioactive or electromagnetic

Abstract

The disclosure relates to methods and apparatus for determining the velocity of an ultrasound pulse in drilling fluids in downhole environments. A method for determining a velocity of ultrasound propagation in a drilling fluid in a downhole environment includes emitting an ultrasound pulse into the drilling fluid in a borehole using a first ultrasound transducer (37); detecting the ultrasound pulse after the ultrasound pulse has traveled a distance (d); determining a travel time (t) required for the ultrasound pulse to travel the distance (d); and determining the velocity of ultrasound propagation from the known distance (d) and the travel time (t). An apparatus for determining a velocity of ultrasound propagation in a drilling fluid in a downhole environment includes a first ultrasound transducer (37) disposed on a tool; and a circuitry (82) for controlling a timing of an ultrasound pulse transmitted by the first ultrasound transducer (37) and for measuring a time lapse between ultrasound transmission and detection after the ultrasound pulse has traveled a distance (d).

Claims

1. - A method for determining a velocity of ultrasound propagation in a drilling fluid in a downhole environment, comprising:

disposing a first ultrasound transducer (37) adjacent to a second ultrasound transducer (39) such that the front face (37f) of the first transducer (37) is offset from the front face (39f) of the second ultrasound transducer (39) by a predetermined radial offset distance (Δ

Df).

emitting an ultrasound pulse into the drilling fluid in a borehole using the first ultrasound transducer (37);

detecting the ultrasound pulse after the ultrasound pulse has travelled through the drilling fluid a distance (d); and

determining the velocity of ultrasound propagation from the distance (d) and the travel time (t).

2. - The method according to claim 1, wherein the detecting the ultrasound pulse is performed with the first ultrasound transducer (37).

3. - The method according to claim 1, wherein the detecting the ultrasound pulse is performed with the second ultrasound transducer (39).

4. - The method according to claim 1, wherein the detecting the ultrasound pulse is performed with both the first and second ultrasound transducer.

5. - The method according to claim 4, further comprising determining a borehole diameter (D_bh) using the predetermined offset distance (Δ

Df) and a difference in travel times (T₂-T₁) for the ultrasound pulse to be detected by the first ultrasound transducer (37) and the second ultrasound transducer (39).

6. - The method according to claim 1, wherein the detecting the ultrasound pulse is performed by the first ultrasound transducer (37), and wherein the method further comprises:

emitting a second ultrasound pulse into the drilling fluid in the borehole using the second ultrasound transducer (39); and

detecting the second ultrasound pulse after the second ultrasound pulse has traveled through the drilling fluid a distance (d+2Δ

D_f) using the second ultrasound transducer (39).

7. - The method according to claim 6, wherein the ultrasound pulse and the second ultrasound pulse are emitted simultaneously.

8. - The method according to claim 1, wherein the drilling fluid is located in an annulus between a tool and a borehole wall.

9. - An apparatus for determining a velocity of ultrasound propagation in a drilling fluid in a downhole environment, comprising:

a first ultrasound transducer (37) disposed on a tool;

a second ultrasound transducer (39) adjacent to said first ultrasound transducer such that the front face (37f) of the first transducer (37) is offset from the front face (39f) of the second ultrasound transducer (39) by a predetermined radial offset distance (Δ

Df); and

a circuitry (82) for controlling a timing of an ultrasound pulse transmitted by the first ultrasound transducer (37) and for measuring a time lapse between ultrasound transmission and detection after the ultrasound pulse has traveled a distance (d).

10. - The apparatus according to claim 9, wherein the first ultrasound transducer (37) and the second ultrasound transducer (39) are disposed on an outside surface of the tool.