Compositions and methods for treating lost circulation
AssigneeSchlumberger Technology Corporation
InventorsBenedicte Zusatz, Frederik Nilsson
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Abstract
A cement system for use in treating lost circulation includes a slurry of cement, water and a super-absorbent polymer which absorbs free water in the slurry to form a gel—ore preferably a solid-like structure—when placed in the well, and which releases the absorbed water to the cement hydration reaction as the cement sets. The absorption of water causes the slurry to develop a solid-like structure. In one embodiment, the superabsorbent is polyacrylamide or modified crosslinked poly(meth)acrylate. Also presented is a method of treating lost circulation by pumping the above-mentioned cement system.
Claims13
A pumpable cement slurry for treating lost circulation, comprising cement, water and a super-absorbent polymer selected from the group consisting of poly(2-propenamide-co-2-propenoic acid sodium salt), polyacrylamide and modified crosslinked poly(meth)acrylate, wherein the super-absorbent polymer is present in the slurry in an encapsulated form to prevent formation of the solid-like structure before the slurry is placed in the well and wherein the super-absorbent polymer absorbs free water in the slurry when the slurry is placed in a well.
A method of treating lost circulation in a well comprising the following steps:
- (i) preparing a slurry comprising cement, water and a super-absorbent polymer, wherein the super-absorbent polymer is selected from the group consisting of poly(2-propenamide-co-2-propenoic acid sodium salt), polyacrylamide and modified crosslinked poly(meth)acrylate and wherein the super-absorbent polymer is present in the slurry in an encapsulated form to prevent formation of the solid-like structure before the slurry is placed in the well;
- (ii) pumping the slurry into a region of lost circulation in the well;
- (iii) causing the slurry to form a solid-like structure in that region;
- and
- (iv) allowing the slurry to set.
Dependencies are inferred from the claim text.