Self-repairing cements
First Claim
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1. A method for maintaining zonal isolation in a subterranean well in which a borehole penetrates one or more methane-containing formations, comprising:
- (i) pumping a cement slurry comprising water, cement and thermoplastic block-polymer particles into the well, wherein the particles consist of styrene-isoprene-styrene polymer particles, and the polymer has a tensile strength between 1.5 MPa and 40 MPa; and
(ii) allowing the cement slurry to set and form a cement sheath; and
(iii) after microannuli, cracks or defects occur in the cement sheath, allowing the methane to contact the particles, thereby causing the particles to swell in response to contact with the methane, and enabling the cement sheath to undergo a hydraulic conductivity reduction of at least 97% and have self-healing properties,wherein the methane is present at a concentration higher than 91 mol % and at a pressure higher than 3.5 MPa.
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Abstract
A self-adaptive cement formulation includes cement, water and thermoplastic block-polymer particles. The set cement demonstrates self-healing properties when exposed to methane, and is particularly suited for well-cementing applications. After placement and curing, the self healing properties help maintain zonal isolation should bonding be disrupted between the set cement and the formation or a casing string, should cracks or defects appear in the set-cement matrix, or both.
32 Citations
12 Claims
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1. A method for maintaining zonal isolation in a subterranean well in which a borehole penetrates one or more methane-containing formations, comprising:
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(i) pumping a cement slurry comprising water, cement and thermoplastic block-polymer particles into the well, wherein the particles consist of styrene-isoprene-styrene polymer particles, and the polymer has a tensile strength between 1.5 MPa and 40 MPa; and (ii) allowing the cement slurry to set and form a cement sheath; and (iii) after microannuli, cracks or defects occur in the cement sheath, allowing the methane to contact the particles, thereby causing the particles to swell in response to contact with the methane, and enabling the cement sheath to undergo a hydraulic conductivity reduction of at least 97% and have self-healing properties, wherein the methane is present at a concentration higher than 91 mol % and at a pressure higher than 3.5 MPa. - View Dependent Claims (2, 3, 4, 5)
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6. A method, comprising:
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imparting self-healing properties to a cement formulation that is placed in a subterranean well penetrating one or more methane containing formations, the methane being present at a concentration higher than 91 mol % and at a pressure higher than 3.5 MPa; wherein once set, the cement forms a cement sheath and, after microannuli, cracks or defects occur in the cement sheath, the particles swell when contacted by the methane and cause the cement sheath to undergo a hydraulic conductivity reduction of at least 97%, and wherein said imparting is achieved by including thermoplastic block-polymer particles in the cement, wherein the particles consist of styrene-isoprene-styrene polymer particles, and the polymer has a tensile strength between 1.5 MPa and 40 MPa. - View Dependent Claims (7, 8, 9, 10)
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11. A method for maintaining zonal isolation in a subterranean well in which a borehole penetrates one or more hydrocarbon-containing formations, comprising:
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(i) pumping a cement slurry comprising water, cement and thermoplastic block-polymer particles into the well, wherein the particles consist of a styrene-butadiene-styrene polymer, and the polymer has a tensile strength between 1.5 MPa and 40 MPa; and (ii) allowing the cement slurry to set and form a cement sheath; and (iii) after microannuli, cracks or defects occur in the cement sheath, allowing formation hydrocarbons to contact the particles, thereby causing the particles to swell, and enabling the cement sheath to have self-healing properties, wherein a flow rate through the cement sheath is reduced by at least 49%, and wherein the hydrocarbon comprises at least 91 mol % methane, the hydrocarbon being present at a pressure higher than 3.5 MPa.
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12. A method, comprising:
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imparting self-healing properties to a cement formulation that is placed in a subterranean well penetrating one or more hydrocarbon-containing formations, the cement formulation comprising water, cement and thermoplastic block copolymer particles that consist of a styrene-isoprene-styrene polymer having a tensile strength between 1.5 MPa and 40 MPa, wherein the cement formulation sets and forms a cement sheath and, after microannuli, cracks or defects occur in the cement sheath, the particles swell when contacted by formation hydrocarbons comprising at least 91 mol % methane, the hydrocarbons being present at a pressure higher than 3.5 MPa and wherein the cement sheath undergoes a hydraulic conductivity reduction of at least 97%.
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Specification