초록 ▼

A method for continuously mixing a borehole fluid such as cement includes using a measurement of the solid fraction of a cement slurry as it is being mixed to determine the ratio of the solid and liquid components to be added to the slurry. A system for mixing the includes a liquid material (water)

A method for continuously mixing a borehole fluid such as cement includes using a measurement of the solid fraction of a cement slurry as it is being mixed to determine the ratio of the solid and liquid components to be added to the slurry. A system for mixing the includes a liquid material (water) supply including a flow meter; a solid material (cement) supply; a mixer which receives the liquid and solid materials and includes an output for delivering materials from the mixer to a delivery system; a device for measuring the amount of material in the mixer, and a flow meter in the output; wherein measurements from the flow meters and the device for measuring the amount of material in the mixer are used to control the amount of solid and/or liquid material added to the mixer.

대표청구항 ▼

The invention claimed is: 1. A system for mixing a cement slurry comprising: i) a liquid material supply (101) including a device (104) for measuring the amount of liquid material supplied; ii) a solid cement supply (108); iii) a mixer including a tub (114) which receives the liquid and solid cemen

The invention claimed is: 1. A system for mixing a cement slurry comprising: i) a liquid material supply (101) including a device (104) for measuring the amount of liquid material supplied; ii) a solid cement supply (108); iii) a mixer including a tub (114) which receives the liquid and solid cement and includes an output (124) for delivering materials from the mixer to a delivery system; iv) a flow meter (128) in the output (124); and v) a computing device, wherein: the system further comprises a device (120) for measuring the amount of material in the mixer; the computing device receives the output from the device ( 120) for measuring the amount of material in the mixer and from the flow meter (104) and is arranged to calculate the variation in the amount of material in the tub (114) over time, and the solid fraction of the mixture; and the calculated solid fraction is used to control the relative amounts of solid and liquid material added to the mixer. 2. A system as claimed in claim 1, wherein the flow meter is selected from mass flow meters and volumetric flow meters. 3. A system as claimed in claim 1, wherein the flow meter is selected from Coriolis meter and electromagnetic meter. 4. A system as claimed in claim 1, wherein the mixer comprises a mixing section and the tub, mixed materials being fed from the mixing section to the mixing tub, and a portion of the materials in the tub being recirculated to the mixing section. 5. A system as claimed in claim 4, wherein the device comprises a level sensor in the tub. 6. A system as claimed in claim 4, wherein the device comprises a load sensor which measures the weight of the tub. 7. A system as claimed in claim 4, wherein recirculation of material takes place upstream of the flow meter in the output. 8. A system as claimed in claim 1, comprising separate supplies of cement and dry additives, a flow meter being provided to measure the rate of flow of the dry additives. 9. A system as claimed in claim 8, wherein the supply of dry additives comprises multiple separate supplies of additives, each with its own flow meter. 10. A system as claimed in any preceding claim, includes at least one tank. 11. A system as claimed in claim 10, further comprising a level sensor in the tank or a flow meter which measures the amount of liquid flowing from the tank. 12. A method of mixing a cement slurry, wherein the cement and liquid components are continuously delivered to a mixer and the cement slurry is continuously removed from the mixer for use, the method comprising: i) measuring the flow rate of liquid components added to the mixer; and ii) measuring the flow rate of slurry removed from the mixer; wherein: iii) measuring the amount of slurry in the mixer; iv) using a measurement of flow rate and amount of slurry to calculate the solid fraction of the fluid; and (v) controlling the delivery of cement and/or liquid components to the mixer according to the calculated solid fraction. 13. A method as claimed in claim 12, wherein additives are delivered to the mixer separately from cement, the method further comprising measuring the flow rate of the additives delivered to the mixer. 14. A method as claimed in claim 12 wherein the mixer includes a tub, the measurement of the amount of slurry in the mixer comprising a measurement of the amount of slurry in the tub. 15. A method as claimed in claim 14, wherein a portion of the slurry in the tub is recirculated into the mixer as solid and liquid components are added. 16. A method as claimed in claim 15, wherein the recirculation takes place upstream of the measurement of the flow rate of slurry removed from the mixer. 17. A method as claimed in any of claims 12-16, wherein liquid components are delivered for mixing from a liquid supply including at least one tank, the method further including the steps of measuring the level of liquid in the tank over time and computing displacement volume as: description="In-line Formulae" end="lead"Σ( V(h1n)-V(h2n))description="In-line Formulae" end="tail" where: V(h) is the exact volume of the tank at level (h) h1n is the start level of the n th displaced tank volume; and h2n is the stop level of the n th displaced tank volume. 18. A method as claimed in claim 12, wherein the step of using a measurement of the flow rate and amount of slurry to calculate the solid fraction of the fluid comprises calculating porosity, porosity being determined as water volume/slurry volume, and solid fraction being equal to one minus porosity. 19. A method as claimed in claim 12, wherein the step of using a measurement of flow rate is a step of using the measurement of the flow rate of the liquid components added to the mixer. 20. A method as claimed in claim 14, wherein the step of measuring the amount of slurry in the mixer comprises using a level sensor to measure the level of slurry in the tub.