Cement analyzer measures gas migration and gel strength
The present invention pertains to a method and experimental apparatus for studying properties of cement slurry to be used in an oil or gas well under varied pressure and temperature conditions. This apparatus can be used to predict the likelihood of gas migration, compressive strength and static gel strength of cement slurry. It comprises a servo motor and coupling magnets to drive a paddle at a very slow speed through the cement in a pressure vessel, a pair of acoustic transducers to generate an acoustic signal and measure the transit time of the acoustic signal after it transits the cement, and a gas injection system to predict the severity of gas migration in cement.
1. A cement analyzer instrument used to determine gas migration and static gel strength, including:
a) a pressure vessel filled with a sample fluid,
b) a gas inlet to provide gas injection,
c) a means to measure a pressure difference of said sample fluid when said gas migrates through said sample fluid,
d) a paddle within said pressure vessel,
e) a means to drive said paddle to rotate,
f) a means to measure a torque that applies on said paddle rotating through said sample fluid.
2. The instrument of claim 1 further comprises a means to apply a confining pressure on said sample fluid by a pressure media.
3. The instrument of claim 2 further comprises a diaphragm for separating said sample fluid from said pressure media.
4. The instrument of claim 1 wherein said means to drive said paddle to rotate is a magnetic coupling across said pressure vessel.
5. The instrument of claim 1 further comprises a flow meter for controlling said gas migrating.
6. The instrument of claim 1 further comprises a means to measure a filtrate volume of said sample fluid.
7. The instrument of claim 1 further comprises a reduced opening between a top section of said pressure vessel and a lower section of said pressure vessel.
8. The instrument of claim 7 further comprises a low friction bearing means that is vertically disposed for supporting said paddle within or above said top section of said pressure vessel.
9. The instrument of claim 1 further comprises a heater to reach and maintain desired test temperature.