Optimizing Drilling Mud Shearing

Abstract

Viscosity and other properties are determined at desired temperatures in drilling mud and other fluids by using a versatile cavitation device which, operating in the cavitation mode, mixes and heats the fluid to a specified temperature, and, operating in the shear mode, acts as a spindle for application of Couette principles to determine viscosity as a function of shear stress and shear rate. The invention obviates the practice of adjusting rheology of a drilling fluid by passing it through the drill bit. Drilling fluid may be managed by a “straight-through” method to the well, or by placing the cavitation device in a loop which isolates an aliquot of known volume and circulating the fluid through the loop including the cavitation device. A controller may be programmed to manage the viscosity and other properties at various temperatures by controlling the power input and angular rotation of the “spindle” (which has cavities on its cylindrical surface), and feeding viscosity-adjusting agents and other additives to the fluid. Data may be collected from the loop and used in the “straight-through” mode until it is determined that conditions require a new set of data, or the loop may be used continuously. The system may be used with a supplemental viscometer, density meter, and other instruments.

1 . Method of measuring viscosity of a fluid at a desired temperature comprising (a) heating said fluid in a cavitation mixer to said desired temperature and (b) calculating viscosity of said fluid by a spindle viscosity formula applied to said fluid in said cavitation mixer. 
     
     
         2 . (canceled) 
     
     
         3 . Method of  claim 1  wherein said cavitation mixer is a flow-directed cavitation mixer. 
     
     
         4 . Method of preparing drilling mud ingredients for use in a well comprising (a) pumping said drilling mud ingredients from at least one source through a conduit, said conduit including a recycle loop with valves for isolating an aliquot of said drilling mud ingredients in said recycle loop, (b) passing an aliquot of drilling mud ingredients so isolated through a cavitation mixer located on said recycle loop to heat, by cavitation, said drilling mud ingredients to a desired temperature, (c) passing said aliquot of drilling mud ingredients through said cavitation mixer, without cavitation, to shear said drilling mud ingredients at said desired temperature to obtain a desired viscosity, thus making a prepared drilling mud for a well, and (d) passing said prepared drilling mud outside said loop for storage or use in a well. 
     
     
         5 . Method of  claim 4  wherein said cavitation mixer is a flow-controlled cavitation mixer. 
     
     
         6 . Method of  claim 4  including, in step (c), determining said desired viscosity by Couette principles, optionally modified by a function of a difference in pressure across said cavitation mixer, applied to said cavitation mixer. 
     
     
         7 . Method of  claim 4  including, in step (c), measuring viscosity by an in-line viscometer within said loop and regulating, as a function of said viscosity, at least one of (i) power input to said cavitation mixer, and (ii) the addition of a viscosity modifier to said drilling mud ingredients. 
     
     
         8 . Method of  claim 4  including intermittently or continuously monitoring said drilling mud ingredients in said loop for at least one of density, flow, viscosity, pH, percent solids, water cut or oil/water ratio, electrical stability, particle size, and temperature. 
     
     
         9 - 35 . (canceled) 
     
     
         36 . Method of measuring the viscosity of a fluid at a desired temperature comprising (a) heating said fluid to said desired temperature in a cavitation mixer having a rotor, said cavitation mixer operated in the cavitation mode and (b) calculating viscosity of said fluid by a spindle velocity formula applied to said rotor in said cavitation mixer operated in the shear mode to shear said fluid at said desired temperature. 
     
     
         37 . Method of  claim 36  wherein said cavitation mixer is a flow-directed cavitation mixer. 
     
     
         38 . Method of  claim 36  wherein said fluid is an aliquot of a drilling fluid isolated in a loop including said cavitation mixer and a pump. 
     
     
         39 . Method of  claim 38  including using said calculated velocity as a factor in controlling viscosity of said drilling fluid as drilling is conducted in a well. 
     
     
         40 . Method of  claim 38  including additionally measuring viscosity of said aliquot of drilling fluid by a viscometer. 
     
     
         41 . Method of  claim 36  wherein said spindle velocity formula includes a function of torque and angular velocity of said rotor. 
     
     
         42 - 55 . (canceled)