PREPARATION OF SETTING SLURRIES

• US 20110127034A1
• Filed: 11/30/2009
• Published: 06/02/2011
• Est. Priority Date: 11/30/2009
• Status: Abandoned Application

• Current Assignee: Schlumberger Technology Corporation (Schlumberger NV)
• Original Assignee: Schlumberger Technology Corporation (Schlumberger NV)
• Inventors: Johnson, Carl, Vidick, Benoit, Monteiro, Glen, Woodrow, Jonathan, Lawrence, Nathan, Hartshorne, Robert Seth
• Application Number:
  US12/627,588
• Publication Number:
  US 20110127034A1
• Time in Patent Office: Days
• US Class Current: 166/293
• CPC Class Codes: C04B 2103/22 Set retarders
• CPC Class Codes: C04B 28/02 containing hydraulic cements other than calcium sulfates
• CPC Class Codes: C04B 40/0032 Controlling the process of mixing, e.g. adding ingredients in a quantity depending on a measured or desired value B28C7/00 takes precedence
• CPC Class Codes: C04B 40/0039 Premixtures of ingredients
• CPC Class Codes: C09K 8/467 containing additives for specific purposes
• CPC Class Codes: E21B 33/14 for cementing casings into boreholes

Abstract

When preparing a settable slurry such as a cement slurry for cementing an oil well, cement or other solid powder is mixed with water and a set retarder. In order to be able to run a convenient and rapid check on the concentration of retarder after dilution at the site of use, a tracer material is mixed with the retarder in known amount during manufacture. The tracer is chosen to enable its concentration to be determined analytically after dilution at the site of use, thereby providing a way to determine the concentration of set retarder after such dilution. The tracer may be a redox-active material and its concentration may be determined by voltammetry. Tracer may likewise be mixed with additives other than set retarder.

Claims

1. A process of preparing a settable slurry by mixing a solid powder, water and one or more additives, characterised by mixing a tracer material with an additive before mixing that additive with the solid powder and the water and analysing a mixture containing at least the additive and at least part of the water to determine the concentration of tracer therein.

2. A process according to claim 1 wherein the step of analyzing a mixture is performed on the slurry.

3. A process according to claim 1 wherein the step of analyzing a mixture is performed on a mixture of the additive and water before mixing with the solid powder.

4. A process according to claim 1 wherein the solid powder is cement, so that the slurry is a cement slurry.

5. A process according to claim 4 wherein said additive with which the tracer is mixed is a cement set retarder.

6. A process according to claim 5 which includes a step of pumping the cement slurry into a space between a borehole and a casing within the borehole.

7. A process according to claim 1 wherein the tracer is mixed with the additive at a manufacturing or storage facility and the additive with admixed tracer is subsequently transported to another site for preparing the slurry by mixing with the solid powder and water.

8. A process according to claim 1 wherein analysis to determine the concentration of tracer is carried out by electrochemistry.

9. A process according to claim 8 carried out with an array of laminar electrodes formed on an insulating substrate.

10. A process according to claim 8 wherein the tracer undergoes electrochemical oxidation and/or reduction and analysis is carried out using voltammetry to determine the concentration of tracer.

11. A process according to claim 10 where analysis is carried out using square wave voltammetry.

12. A process according to claim 8 wherein

the step of analyzing a mixture is performed on a mixture containing a mediator compound which undergoes electrochemical oxidation and reduction

the tracer undergoes chemical reaction with the mediator compound, and

analysis is carried out using voltammetry to observe the effect of tracer on electrochemical reaction of the mediator compound.