Measurement of cement slurry properties under downhole conditions

Abstract

The present invention relates to a method for measuring a cement slurry property, such as static gel strength or yield stress, under at least one downhole condition, and apparatuses and systems for performing the same. In some embodiments, the method includes detecting a downward force exerted by a curing cement slurry under at least one downhole condition within a vessel movable along a vertical axis proportionally to the downward force. A surface substantially nonmovable along the vertical axis is disposed at least partially within the cement slurry. The method also includes determining at least one property of the cement slurry from the detected downward force.

1 . A method of measuring a cement slurry property under a downhole condition, the method comprising:
 detecting a downward force exerted by a curing cement slurry under at least one downhole condition within a vessel movable along a vertical axis proportionally to the downward force, a surface substantially nonmovable along the vertical axis being disposed at least partially within the cement slurry; and   determining at least one property of the cement slurry from the detected downward force.   
     
     
         2 . The method of  claim 1 , wherein the downward force comprises a buoyancy weight of the slurry minus a weight of the slurry supported on the surface by shear stress. 
     
     
         3 . (canceled) 
     
     
         4 . The method of  claim 1 , wherein detecting the downward force comprises detecting a vertical position of the vessel. 
     
     
         5 . The method of  claim 1 , wherein the determining the at least one property comprises determining at least one of a shear stress of the cement slurry on the surface, a static gel strength of the cement slurry, a yield stress of the cement slurry, a loss of weight of the cement slurry due to curing, a variation of hydrostatic pressure of the slurry over time, a setting time of the cement slurry, and a dormant time of the cement slurry. 
     
     
         6 . The method of  claim 1 , wherein the determining comprises determining the approximate shear stress of the cement slurry on the surface at time t comprising dividing a first quantity by a surface area of the surface contacted by the cement slurry, wherein the first quantity comprises the downward force exerted by the curing cement slurry at time 0 minus the downward force exerted by the curing cement slurry at time t. 
     
     
         7 . The method of  claim 6 , wherein determining the first quantity comprises multiplying a spring constant by a second quantity, wherein the second quantity comprises a vertical position of the vessel at time 0 minus a vertical position of the vessel at time t. 
     
     
         8 - 10 . (canceled) 
     
     
         11 . The method of  claim 1 , wherein a compartment encloses the vessel within an interior of the compartment, wherein the compartment is configured to provide the at least one downhole condition within the vessel. 
     
     
         12 - 15 . (canceled) 
     
     
         16 . The method of  claim 11 , wherein the compartment encloses at least part of a detector within the interior of the compartment, wherein the detector detects the downward force. 
     
     
         17 . (canceled) 
     
     
         18 . The method of  claim 11 , wherein the vessel is movable along the vertical axis with respect to the interior of the compartment. 
     
     
         19 . The method of  claim 11 , wherein the compartment encloses at least part of the surface within the vessel. 
     
     
         20 . (canceled) 
     
     
         21 . The method of  claim 11 , wherein the surface is secured to the interior of the compartment and the surface is substantially nonmovable along the vertical axis with respect to the interior of the compartment. 
     
     
         22 . The method of  claim 1 , wherein the downhole condition comprises at least one of temperature, pressure, agitation, and liquid environment of the slurry. 
     
     
         23 - 28 . (canceled) 
     
     
         29 . The method of  claim 22 , wherein the agitation comprises at least one of shearing, vibrating, shaking, and stirring. 
     
     
         30 . (canceled) 
     
     
         31 . The method of  claim 1 , wherein the surface comprises a textured surface. 
     
     
         32 . The method of  claim 1 , wherein the detecting of the downward force comprises using a detector. 
     
     
         33 . The method of  claim 32 , wherein the detector comprises a scale. 
     
     
         34 . The method of  claim 32 , wherein a resilient member provides upward resistance proportional to downward vertical movement of the vessel along the vertical axis. 
     
     
         35 . (canceled) 
     
     
         36 . The method of  claim 1 , wherein the cement slurry comprises Portland cement, pozzolana cement, gypsum cement, high alumina content cement, slag cement, silica cement, or a combination thereof. 
     
     
         37 - 38 . (canceled) 
     
     
         39 . A method of measuring a cement slurry property under a downhole condition, the method comprising:
 providing or obtaining an apparatus comprising
 a vessel configured to move along a vertical axis proportionally to a downward force within the vessel; 
 a detector configured to detect a vertical position of the vessel along the vertical axis; and 
 a surface disposed at least partially within the vessel, wherein the surface is substantially nonmovable along the vertical axis; 
 wherein the apparatus is configured to provide at least one downhole condition within the vessel; 
   placing a cement slurry within the vessel;   configuring at least one downhole condition within the vessel;   allowing the cement slurry to at least partially cure; and   determining at least one property of the cement slurry from the detected vertical position of the vessel during at least part of the curing of the cement slurry.   
     
     
         40 . An apparatus for measuring a property of a cement slurry under a downhole condition, the apparatus comprising:
 a vessel configured to move along a vertical axis proportionally to a downward force within the vessel;   a detector configured to detect the downward force; and   a surface disposed at least partially within the vessel, wherein the surface is substantially nonmovable along the vertical axis;   wherein the apparatus is configured to provide at least one downhole condition within the vessel.   
     
     
         41 - 47 . (canceled)