Acoustic method for determining the static gel strength of a cement slurry
First Claim
1. An acoustic method for determining the static gel strength of a cement slurry sample, comprising the steps of:
- (a) maintaining said sample in a static condition at a controlled temperature and pressure;
(b) transmitting an acoustic signal through said sample;
(c) measuring the amplitude of said acoustic signal as it transits said sample to obtain signal attenuation data;
(d) repeating steps (b) and (c) at a predetermined number of time points, thereby producing a predetermined number of amplitude measurements;
(e) calculating from said predetermined number of amplitude measurements at least one value representative of a derivative; and
,(f) calculating a static gel strength of said sample by using at least one of said at least one values representative of a derivative.
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Accused Products
Abstract
An acoustic method and system for determining the static gel strength of one or more cement slurry samples at wellbore temperatures and pressures. The cement slurry sample to be tested is maintained in a static condition inside an acoustic pressure vessel at a controlled temperature and pressure. A first transducer generates an acoustic signal which is transmitted through the sample. A second transducer measures and records the amplitude of the acoustic signal after it transits the sample. This data is then processed and the static gel strength of the sample is determined according to a predetermined relationship relating signal amplitude to static gel strength.
75 Citations
19 Claims
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1. An acoustic method for determining the static gel strength of a cement slurry sample, comprising the steps of:
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(a) maintaining said sample in a static condition at a controlled temperature and pressure; (b) transmitting an acoustic signal through said sample; (c) measuring the amplitude of said acoustic signal as it transits said sample to obtain signal attenuation data; (d) repeating steps (b) and (c) at a predetermined number of time points, thereby producing a predetermined number of amplitude measurements; (e) calculating from said predetermined number of amplitude measurements at least one value representative of a derivative; and
,(f) calculating a static gel strength of said sample by using at least one of said at least one values representative of a derivative. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14)
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15. A method for determining the static gel strength of a cement slurry sample, comprising the steps of:
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(a) maintaining said sample in a static condition at a controlled temperature and pressure; (b) transmitting an acoustic signal through said sample; (c) measuring the amplitude of said acoustic signal as it transits said sample to obtain signal attenuation data; (d) repeating steps (b) and (c) at a predetermined number of time points to obtain a predetermined number of amplitude measurements and a same predetermined number of corresponding time points, said amplitude measurements and time points together comprising an amplitude curve; (e) identifying, from within said amplitude curve, a region containing a plurality of amplitude measurements, wherein said amplitude curve is at least approximately linear; and
,(f) using at least two of said amplitude measurements within said approximately linear region to calculate an estimate of said static gel strength. - View Dependent Claims (16)
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17. A method for determining the static gel strength of a cement slurry sample, comprising the steps of:
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(a) maintaining said sample in a static condition at a controlled temperature and pressure; (b) transmitting an acoustic signal through said sample; (c) measuring an amplitude value of said acoustic signal as it transits said sample to obtain signal attenuation data; (d) repeating steps (b) and (c) at a predetermined number of time points to obtain a predetermined number of amplitude values and a same predetermined number of corresponding time points, said amplitude values and time points together comprising an amplitude curve; (e) identifying at least one amplitude value proximate to an inflection point of said amplitude curve; (f) calculating a static gel strength of said sample by using at least one of said at least one amplitude values proximate to an inflection point. - View Dependent Claims (18)
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19. An acoustic method for determining the static gel strength of a cement slurry sample, comprising the steps of:
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(a) maintaining said sample in a static condition at a controlled temperature and pressure; (b) transmitting an acoustic signal through said sample; (c) measuring the amplitude of said acoustic signal as it transits said sample to obtain signal attenuation data; and (d) calculating, according to a predetermined relationship relating signal attenuation to static gel strength, the static gel strength of said sample.
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Specification