Compositions and methods for well completions

• US 8,689,871 B2
• Filed: 10/14/2011
• Issued: 04/08/2014
• Est. Priority Date: 11/08/2010
• Status: Active Grant

• Current Assignee: Schlumberger Technology Corporation (SLB)
• Original Assignee: Schlumberger Technology Corporation (SLB)
• Inventors: Khatri, Deepak, Rice, Mitch, Strickler, Nikole, Williams, Robert
• Primary Examiner(s): Bates, Zakiya W
• Application Number:
  US13/273,236
• Publication Number:
  US 20120175118A1
• Time in Patent Office: 907 Days
• Field of Search: None
• US Class Current: 166/293
• CPC Class Codes: C04B 20/008 Micro- or nanosized fillers, e.g. micronised fillers with particle size smaller than that of the hydraulic binder colloidal silica C04B14/062 ; silica fume C04B18/146
• CPC Class Codes: C04B 20/1033 obtained by reactions only involving carbon-to-carbon unsaturated bonds
• CPC Class Codes: C04B 20/1048 Polysaccharides, e.g. cellulose, or derivatives thereof
• CPC Class Codes: C04B 22/04 Metals, e.g. aluminium used as blowing agent
• CPC Class Codes: C04B 24/129 Compounds containing one or more nitrogen-to-nitrogen double bonds, e.g. azo-compounds
• CPC Class Codes: C04B 28/02 containing hydraulic cements other than calcium sulfates
• CPC Class Codes: C04B 38/02 by adding chemical blowing agents
• CPC Class Codes: C04B 40/0633 Chemical separation of ingredients, e.g. slowly soluble activator
• CPC Class Codes: C09K 8/426 for plugging
• CPC Class Codes: C09K 8/428 for squeeze cementing, e.g. for repairing
• CPC Class Codes: C09K 8/473 Density reducing additives, e.g. for obtaining foamed cement compositions

Abstract

Expansive cements for use in cementing subterranean wells contain an encapsulated gas-generating substance. The gas-generating substance comprises one or more materials that release hydrogen, nitrogen or both. The gas-generating substance is encapsulated by a coating comprising a polymer. The coating prevents premature gas release at the surface during slurry mixing, and promotes gas release at a desired location in the subterranean well. The released gas may also control the internal pore pressure of the cement slurry, thereby inhibiting the invasion of formation fluids into the borehole.

Claims

1. A method for cementing a subterranean well, comprising:

(i) preparing a well-cementing composition comprising water, an inorganic cement and an additive comprising particles comprising a gas-generating substance that is encapsulated by coating comprising a polymer, wherein the gas-generating substance comprises one or more materials that release hydrogen, nitrogen or both; and

(ii) placing the composition in the well,

wherein the additive particle size is between about 2 μ

m and 2000 μ

m.

2. The method of claim 1, wherein the gas-generating materials that release hydrogen comprise one or more members of the list comprising aluminum, calcium, zinc, iron, magnesium, lithium, sodium and potassium.

3. The method of claim 1, wherein the gas-generating materials that release nitrogen comprise one or more members of the list comprising azodicarbonamide, sodium azodicarboxylate, azobismethyl propionitrite and p-toluenesulfonhydrazide.

4. The method of claim 1, wherein the coating comprises one or more members selected from the group consisting of styrene-butadiene copolymer latexes, acrylic resins, styrene/acrylic copolymer resins, acrylic ester resins, methylcellulose, ethylcellulose, hydroxypropylcellulose, and polyvinylidene chloride.

5. The method of claim 4, wherein the molecular weight of the styrene-butadiene copolymer is between about 1.5·

10⁵ g/mol and about 4.0·

10⁵ g/mol.

6. The method of claim 1, wherein the coating is present at a concentration up to about 20% by weight of gas-generating material.

7. A method for controlling the liberation of gas from a gas-generating agent, comprising:

(i) providing particles comprising a gas-generating substance, wherein the gas-generating substance comprises one or more materials that release hydrogen, nitrogen or both; and

(ii) coating the particle surfaces with a material comprising a polymer, thereby encapsulating the particles,

wherein the additive particle size is between about 2 μ

m and 2000 μ

m.

8. The method of claim 7, wherein the gas-generating material releases hydrogen, and comprises one or more members of the list comprising aluminum, calcium, zinc, iron, magnesium, lithium, sodium and potassium.

9. The method of claim 7, wherein the gas-generating material releases nitrogen, and comprises one or more members of the list comprising azodicarbonamide, sodium azodicarboxylate, azobismethyl propionitrite and p-toluenesulfonhydrazide.

10. The method of claim 7, wherein the coating comprises one or more members selected from the group consisting of styrene-butadiene copolymer latexes, acrylic resins, styrene/acrylic copolymer resins, acrylic ester resins, methylcellulose, ethylcellulose, hydroxypropylcellulose, and polyvinylidene chloride.

11. The method of claim 10, wherein the molecular weight of the styrene-butadiene copolymer is between about 1.5·

10⁵ g/mol and about 4.0·

10⁵ g/mol.

12. The method of claim 7, wherein the coating is present at a concentration up to about 20% by weight of gas-generating material.

13. A method for controlling the internal pore pressure of a well-cementing composition in a subterranean well, comprising:

(i) preparing a well-cementing composition comprising water, an inorganic cement and an additive comprising particles comprising a gas-generating substance that is encapsulated by a coating comprising a polymer, wherein the gas-generating substance comprises one or more materials that release hydrogen, nitrogen or both;

(ii) placing the composition in the well; and

(iii) allowing the coating to degrade, thereby exposing the gas-generating material to water, thereby causing the liberation of gas, thereby pressurizing the well-cementing composition,

wherein the additive particle size is between about 2 μ

m and 2000 μ

m.

14. The method of claim 13, wherein the gas-generating material releases hydrogen, and comprises one or more members of the list comprising aluminum, calcium, zinc, iron, magnesium, lithium, sodium and potassium.

15. The method of claim 13, wherein the gas-generating material releases nitrogen, and comprises one or more members of the list comprising azodicarbonamide, sodium azodicarboxylate, azobismethyl propionitrite and p-toluenesulfonhydrazide.

16. The method of claim 13, wherein the coating comprises one or more members selected from the group consisting of styrene-butadiene copolymer latexes, acrylic resins, styrene/acrylic copolymer resins, acrylic ester resins, methylcellulose, ethylcellulose, hydroxypropylcellulose, and polyvinylidene chloride.

17. The method of claim 13, wherein the coating is present at a concentration up to about 20% by weight of gas-generating material.