Synergistic approach to develop resilient cement systems for long term wellbore integrity of oil, gas and geothermal wells
AssigneeSaudi Arabian Oil Company
InventorsAshok Santra, Kenneth Johnson, Roland Martinez
Life of this patent
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Abstract
A cement slurry includes water, a cement precursor, a sliding ring polymer, and an additional polymer. A cured cement composition, such as a cement sheath, can be prepared from the cement slurry. A method for providing a cement sheath in a wellbore includes introducing the cement slurry to an area between a casing and a formation rock of the wellbore and curing the cement slurry injected to the area between the casing and the formation rock of the wellbore, thereby forming the cement sheath in the wellbore.
Claims16
A cement slurry comprising:
- From 45 to 75 wt. % of water by weight of the cement precursor;
- a cement precursor;
- from 30 to 50 wt. % of silica flour by weight of the cement precursor;
- from 0.25 to 3.5 wt. % of a sliding ring polymer comprising a polyrotaxane polymer by weight of the cement precursor;
- from 10 to 20 wt. % of a thermoplastic styrene-butadiene copolymer by weight of the cement precursor;
- and
- from 0.1 to 10 wt. % of a cement retarder by weight of the cement precursor, wherein the cement retarder comprises one or more compounds selected from the group consisting of a sodium lignosulfonate, a calcium lignosulfonate, a copolymer of acrylic acid (AA) and 2-acrylamido-2-methylpropane sulfonic acid (AMPS), and combinations thereof;
- wherein the sliding ring polymer and the thermoplastic styrene-butadiene copolymer are present in the cement slurry as a mixture of polymers;
- and
- wherein a cured cement composition formed from the cement slurry has a lower Young's modulus as compared to a cured cement prepared in the absence of the sliding ring polymer or the thermoplastic styrene-butadiene copolymer.
A method for providing a cement sheath in a wellbore, the method comprising:
- introducing a cement slurry to an area between a casing and a formation rock of the wellbore,
- wherein the cement slurry comprises:
- from 45 to 75 wt. % of water by weight of the cement precursor;
- a cement precursor;
- from 30 to 50 wt. % of silica flour by weight of the cement precursor;
- from 0.25 to 3.5 wt. % of a sliding ring polymer comprising a polyrotaxane polymer by weight of the cement precursor;
- from 10 to 20 wt. % of a thermoplastic styrene-butadiene copolymer by weight of the cement precursor;
- and
- from 0.1 to 10 wt. % of a cement retarder by weight of the cement precursor, wherein the cement retarder comprises one or more compounds selected from the group consisting of a sodium lignosulfonate, a calcium lignosulfonate, a copolymer of acrylic acid (AA) and 2-acrylamido-2-methylpropane sulfonic acid (AMPS), and combinations thereof,
- wherein the sliding ring polymer and the thermoplastic styrene-butadiene copolymer are present in the cement slurry as a mixture of polymers,
- curing the cement slurry injected to the area between the casing and the formation rock of the wellbore, thereby forming the cement sheath in the wellbore, wherein the cement sheath has a lower Young's modulus as compared to a cured cement prepared in the absence of the sliding ring polymer or the thermoplastic styrene-butadiene copolymer.
Dependencies are inferred from the claim text.