Delayed gelling agents

Abstract

The invention is directed to delayed gelation agents comprising a degradable polymeric cage containing therein one or more gelation agents. The cage degrades in situ, e.g, in an oil reservoir, thus releasing the gelation agent(s), which can then crosslink second polymers in situ to form a gel.

Claims

1. A delayed gelation composition, comprising a degradable polymeric cage, and having within said cage a gelation agent, wherein said polymer comprises one or more monomers and is crosslinked with a labile crosslinker to form said degradable polymeric cage, wherein the monomer comprises sodium AMPS and the labile crosslinker comprises a polyethylene glycol diacrylate and the gelation agent comprises chromium and polyethyleneimine.

2. The composition of claim 1, wherein the labile crosslinker is an acid labile ketal of the formula: ##STR00002## where wherein n and m are independently an integer of between 1 and 10, Y is a lower alkyl, and wherein R1 and R2 are independently a lower alkyl.

3. The composition of claim 1, wherein the labile crosslinker is 2-bis[2,2′-di(N-vinylformamido)ethoxy]propane or 2-(N-vinylformamido)ethyl ether.

4. A method of making the composition of claim 1, comprising a) mixing said sodium AMPS monomer and an initiator and said labile crosslinker and said gelation agent, to form a degradable polymeric cage containing said gelation agent; or b) mixing said polymer and said crosslinker and said gelation agent, to form a degradable polymeric cage containing said gelation agent, wherein said labile crosslinker comprises a polyethylene glycol diacrylate and said gelation agent comprises chromium and polyethyleneimine.

Description

DESCRIPTION OF THE FIGURES

(1) FIG. 1: Synthesis of (multivalent cations)-loaded crosslinked polymeric particles.

(2) FIG. 2: Comparison of gelation of 0.5% HPAM and d12 (100 ppm Cr.sup.3+ and 1200 ppm PEI) with 0.5% HPAM and Cr(IlI) Acetate (100 ppm Cr.sup.3+) in Synthetic Brine A at 75° C.

(3) FIG. 3: Comparison of gelation of 0.5% B29 polymer and d12 or d12-1 (100 ppm Cr.sup.3+ and 1200 ppm PEI) with 0.5% B29 polymer and Cr(IlI) Acetate (100 ppm Cr.sup.3+) in Synthetic Brine A at 75° C.

(4) FIG. 4: Comparison of gelation of 0.5% B29 polymer and d12S (100 ppm Cr.sup.3+ and 1200 ppm PEI) with 0.5% B29 polymer and Cr(IlI) Acetate (100 ppm Cr.sup.3+) in Synthetic Brine A at 65° C.

(5) FIG. 5: Comparison of gelation of 0.5% B29 polymer and d12-[no Cr] (PEI 1200 ppm) with 0.5% B29 polymer and Cr(IlI) Acetate (100 ppm Cr.sup.3+) in Synthetic Brine A at 65° C.

DESCRIPTION OF EMBODIMENTS OF THE INVENTION

(6) This invention provides a novel degradable polymeric cage containing a gelation agent that can delay the gelation of second polymers by delaying the release of gelation agent until the polymeric cage degrades.

(7) In an example of such composition, PEI/Cr(III)-acetate is encapsulated in a degradable crosslinked poly(Na-AMPS) particles shell, which can delay the release of PEI and Cr(III)-acetate for further gelation with anionic water-soluble polymers. Such novel polymeric particles have particular utility in delayed gelation of anionic polymers for placement of gels in target zones deep into oil- or gas-bearing formations.

(8) A schematic of the inventive polymers is provided in FIG. 1.

(9) The following examples are illustrative only and should not serve to unduly limit the invention.

EXAMPLE 1

NA-AMPS Cage Containing PEI/Chromium

(10) A representative multivalent cations and cationic polymer-loaded crosslinked polymeric particle or cage, herein referred to as “d12” was prepared using an inverse-emulsion polymerization.

(11) In such process, an aqueous mixture containing 22 g of 50% sodium 2-acrylamido-2-methylpropane sulfonate (sodium AMPS), 10 g of 50% PEI (2000 Mw), 6.5 g distilled water, 35 mg poly(ethylene glycol) (258) diacrylate, 1.61 g Chromium (III) acetate hydroxide (CH.sub.3COO).sub.7Cr.sub.3(OH).sub.2 as the dispersed phase (6400 ppm Cr.sup.+++) and an oil mixture of 20 g kerosene, 3.2 g Span 83 and 1.8 g polyoxyethylene sorbitol hexaoleate (PSH) as continuous phase were prepared.

(12) The inverse-emulsion was prepared by mixing the aqueous phase and the oil phase, followed by rapid homogenization using a homogenizer. After adding the emulsion and 20 mg VAZO® 52 as an initiator into a 250 ml flask and purging this mixture with nitrogen for 15 minutes, polymerization was carried out in 50° C. oil bath for 7 hours. VAZO® 52 is a low-temperature polymerization initiator, whose rate of decomposition is first-order and is unaffected by contaminants such as metal ions.

EXAMPLE 2

NA-Vinyl Sulfonate Cages Containing PEI/Chromium

(13) In this example, we replaced sodium AMPS with sodium vinyl sulfonate (sodium VS) as a monomer in the synthesis of Example 1 above.

(14) A representative multivalent cations and cationic polymer-loaded crosslinked polymeric particle, here forth referred to as “d12S” was prepared containing 6400 ppm Cr(III) using inverse-emulsion polymerization. In such process, an aqueous mixture containing 30 g of 25% sodium VS, 8 g of 50% PEI (2000 Mw), 34 mg poly(ethylene glycol) (258) diacrylate, 1.60 g chromium (III) acetate hydroxide (CH.sub.3COO).sub.7Cr.sub.3(OH).sub.2 as the dispersed phase and an oil mixture of 20 g kerosene, 3.2 g Span 83 and 1.8 g PSH as continuous phase were prepared.

(15) The inverse-emulsion was prepared by mixing the aqueous phase and the oil phase, followed by rapid homogenization using a homogenizer. After adding the emulsion and 20 mg VAZO® 52 as an initiator into a 250 ml flask and purging this mixture with nitrogen for 15 minutes, polymerization was carried out in 50° C. oil bath for 7 hours.

EXAMPLE 3

NA-AMPS Cage Containing PEI

(16) A representative cationic polymer-loaded crosslinked polymeric particle or cage, herein referred to as “d12-[no Cr]” was prepared using an inverse-emulsion polymerization.

(17) In such process, an aqueous mixture containing 22 g of 50% sodium 2-acrylamido-2-methylpropane sulfonate (sodium AMPS), 10 g of 50% polyethyleneimine (2000 Mw), 8.1 g distilled water, 35 mg poly(ethylene glycol) (258) diacrylate as the dispersed phase and an oil mixture of 20 g kerosene, 3.2 g Span 83 and 1.8 g polyoxyethylene sorbitol hexaoleate (PSH) as continuous phase were prepared.

(18) The inverse-emulsion was prepared by mixing the aqueous phase and the oil phase, followed by rapid homogenization using a homogenizer. After adding the emulsion and 20 mg VAZO® 52 as an initiator into a 250 ml flask and purging this mixture with nitrogen for 15 minutes, polymerization was carried out in 50° C. oil bath for 7 hours. VAZO® 52 is a low-temperature polymerization initiator, whose rate of decomposition is first-order and is unaffected by contaminants such as metal ions.

EXAMPLE 4

Synthesis of Other Compounds

(19) The above examples can be repeated to include other positively charged polymers such as polylysine, poly(allylamine) etc. to replace PEI described in Examples 1 and 2 above. Alternatively, the PEI can be omitted, and the multivalent cation can be the sole gelation agent.

EXAMPLE 5

Extending Delay

(20) This process can also be expanded to a range of gelation delay, from one week to 3 months. This can be accomplished by varying the concentration or the composition of XL (labile crosslinker) in Scheme 1.

EXAMPLE 6

Delayed Gelation

(21) The gelation agent-loaded polymeric cages of this invention were predicted to delay the gelation of both HPAM and other anionic polymers, such as B29, a swellable copolymer of acrylamide and sodium acrylate crosslinked with poly(ethylene glycol) (258) diacrylate and methylene bisacrylamide.

(22) We sought to test the delayed gelation using Synthetic Brine A. Generally speaking, the polymeric cage particles d12 were mixed with Synthetic Brine A and a second polymer, set at 75° C. and the viscosity of the solutions measured at intervals to determine the rate of gelation of the second polymer. The second polymer can be an ordinary polymer, or is preferably a swellable polymer that swells in situ, such as is described above.

(23) TABLE-US-00002 Composition of Synthetic Brine A Component Unit Value pH — 8.0 Specific Gravity @ 60 F. — 1.0186 Bicarbonate mg/l 1621 Chloride mg/l 15330 Sulfate mg/l 250 Calcium mg/l 121 Potassium mg/l 86.9 Magnesium mg/l 169 Sodium mg/l 11040 Strontium mg/l 7.6

(24) Gelation of HPAM with degradable polymeric cages (D12): 0.78 g of 30% inverting surfactant and 25 g of 2% HPAM were added into 72.66 g of deoxygenated Synthetic Brine A in a beaker with stirring in an oxygen-free glove box; and then 1.56 g of degradable polymeric cage particles containing Cr(III)-Acetate and PEI (d12) was added into the above mixture under stirring (final Cr(III) concentration was 100 ppm, final PEI concentration was 1200 ppm); finally the initial viscosity was recorded. The solution was then divided into 6 ml vials and incubated at 75° C. The viscosities of the samples were monitored as a function of time.

(25) The results are shown in FIG. 2. As this figure shows, the delayed release gelation agents forms gels with HPAM at a much slower rate than the prior art complexed multivalent cations used alone to gel HPAM.

(26) Gelation of B29 with Degradable Polymeric Cages (d12 and d12-1):

(27) 1.62 g of 30% inverting surfactant was added into 95.15 g of deoxygenated Synthetic Brine A in a beaker with stirring in an oxygen-free glove box; and then 1.67 g of 30% B29 and 1.56 g of the degradable polymeric particle d12 or d12-1 were added into the above solution under stirring, respectively. The initial viscosity of the solution was determined before dividing the rest of the solution into 6 ml vials. The vials were incubated at 75° C. for various lengths of time before measuring their viscosity of the solution. The results for two degradable crosslinkers d12 and d12-1, a synthetic duplicate of d12, are shown in FIG. 3.

(28) Gelation of B29 with Degradable Polymeric Cages (d12S):

(29) 1.62 g of 30% inverting surfactant was added into 95.15 g of deoxygenated Synthetic Brine A in a beaker with stirring in an oxygen-free glove box; and then 1.67 g of 30% B29 and 1.56 g of the degradable polymeric particle d12S were added into the above solution under stirring, respectively. The initial viscosity of the solution was determined before dividing the rest of the solution into 6 ml vials. The vials were incubated at 65° C. for various lengths of time before measuring their viscosity of the solution. The results for d12S are shown in FIG. 4.

(30) Gelation of B29 with Degradable Polymeric Cages (d12-[No Cr]):

(31) 1.62 g of 30% inverting surfactant was added into 95.15 g of deoxygenated Synthetic Brine A in a beaker with stirring in an oxygen-free glove box; and then 1.67 g of 30% B29 and 1.56 g of the degradable polymeric particle d12-[no Cr] were added into the above solution under stirring, respectively. The initial viscosity of the solution was determined before dividing the rest of the solution into 6 ml vials. The vials were incubated at 65° C. for various lengths of time before measuring their viscosity of the solution. The results for d12-[no Cr] are shown in FIG. 5.

(32) The following references are incorporated by reference herein in their entirety:

(33) U.S. Pat. Nos. 6,454,003, 6,729,402 and U.S. Pat. No. 6,984,705

(34) U.S. Pat. No. 4,683,949

(35) U.S. Pat. No. 4,644,073

(36) U.S. Pat. No. 4,986,356

(37) US2008075667