Thixotropic cement slurry and placement method to cure lost circulation

Patent metadata

Field	Value
Publication number	US-2019106952-A1
Application number	US-201816154248-A
Country	US
Kind code	A1
Filing date	Oct 8, 2018
Priority date	Oct 10, 2017
Publication date	Apr 11, 2019
Grant date	—

Abstract

Embodiments of methods for reducing lost circulation in a wellbore comprise inserting a conduit comprising a first and second end and an outer diameter and an inner diameter into the wellbore, and pumping a thixotropic cement slurry, wherein the thixotropic cement slurry will increase in viscosity with no shear and decrease in viscosity with shear, and have a power law exponent value of less than or equal to 0.3 when the thixotropic cement slurry has a density of greater than 12.69 pounds per gallon, through the conduit into the wellbore, in which the thixotropic cement slurry comprises at least one cement, at least one viscosifier, mix water, and one or more than one strength accelerating additives. The method further comprises allowing the thixotropic cement slurry to harden in the wellbore to create a plug, removing the conduit from the wellbore, and reducing lost circulation via the plug in the wellbore.

First claim

What is claimed is:

1 . A method of reducing lost circulation in a wellbore comprising:
inserting a conduit comprising a first and second end and an outer diameter and an inner diameter into the wellbore; pumping a thixotropic cement slurry, wherein the thixotropic cement slurry will increase in viscosity with no shear and decrease in viscosity with shear, and have a power law exponent value of less than or equal to 0.3 when the thixotropic cement slurry has a density of greater than 12.69 pounds per gallon, through the conduit into the wellbore, in which the thixotropic cement slurry comprises at least one cement, at least one viscosifier, mix water, and one or more than one strength accelerating additives; allowing the thixotropic cement slurry to harden in the wellbore to create a plug; removing the conduit from the wellbore; and reducing lost circulation via the plug in the wellbore.

2 . The method of claim 1 , in which the conduit is a pipe and the inner diameter has a range of 2.551″ to 5.875″.

3 . The method of claim 1 , in which the cement comprises Portland cement.

4 . The method of claim 1 , in which the viscosifier comprises bentonite.

5 . The method of claim 1 , in which the strength accelerating additive comprises at least one of sodium silicate or sodium metasilicate.

6 . The method of claim 1 , in which the thixotropic cement slurry further comprises at least one dispersant, at least one antifoaming agent, or at least one retarder.

7 . The method of claim 1 , in which the thixotropic cement slurry has a shear stress of greater than 9 centipoise at 3 rotations per minute at bottom hole circulating temperature.

8 . The method of claim 1 , in which the thixotropic cement slurry has a gel strength at 10 minutes at bottom hole circulating temperature greater than twice the gel strength at 10 seconds at bottom hole circulating temperature.

9 . The method of claim 1 , in which the thixotropic cement slurry mix water comprises at least one of fresh water or seawater.

10 . The method of claim 1 , in which the thixotropic cement slurry comprises bentonite in an amount ranging from 1 weight percent to 5 weight percent of cement pre-hydrated.

11 . The method of claim 1 , in which the thixotropic cement slurry comprises sodium meta-silicate in an amount ranging from 0.5 weight percent to 3 weight percent of cement pre-hydrated.

12 . The method of claim 1 , in which the plug has a maximum volume calculated by dividing a volume of the conduit by a factor of 0.7.

13 . The method of claim 1 , in which the outer diameter of the conduit is equal to a diameter of the wellbore divided by 2.25.

14 . The method of claim 1 , in which the diameters of the conduit vary along a length of the conduit.

15 . The method of claim 1 , further comprising inserting the conduit to a specified depth at or above a loss zone.

16 . The method of claim 1 , further comprising pumping a spacer fluid through the conduit prior to pumping the thixotropic cement slurry.

17 . The method of claim 1 , further comprising pumping a spacer fluid through the conduit following the thixotropic cement slurry.

18 . The method of claim 1 , further comprising pumping the thixotropic cement slurry through the conduit and pumping a drilling mud through the conduit.

19 . The method of claim 1 , further comprising removing the conduit while pumping at least one of the thixotropic cement slurry, the drilling mud, or the spacer fluid through the conduit until the second end of the conduit is above the plug.

20 . The method of claim 1 , further comprising pumping the drilling mud down the wellbore outside the conduit such that the drilling mud flows up the conduit.

Assignees

• Saudi Arabian Oil Co

Inventors

• Shine Jr Joseph Michael

Classifications

• C04B28/04 Primary

  Portland cements · CPC title

• C04B28/26

  Silicates of the alkali metals · CPC title

• E21B21/003 Primary

  Means for stopping loss of drilling fluid (plastering the borehole wall E21B33/138) · CPC title

• C09K8/426

  for plugging · CPC title

• C09K8/424

  using "spacer" compositions · CPC title