Well cementing

Abstract

A hydraulic well cementing composition is disclosed. The well cementing composition contains a hydraulic cement and a fluid loss additive. The fluid loss additive is the polymerization reaction product of a two vinylamide monomers, wherein the polymerization reaction is conducted in the presence of a molecular weight control agent. One of the vinylamide monomers includes a sulfonic acid function, the second vinylamide monomer does not include a sulfonic acid function. The fluid loss additive controls fluid loss at temperatures up to 350 F.

Claims

1. A method of making a cementing fluid loss additive, said method consisting of combining a first monomer with a second monomer in a polymerization reaction in the presence of a molecular weight control agent and at a pH in the range of from about 7.0 to about 10.5; wherein: said first monomer is a vinylamide derivative which does include a sulfonic acid function in its structure, and said second monomer is a vinylamide derivative which does not include a sulfonic acid function in its structure; said molecular weight control agent is selected from humic acid, potassium humate, sodium humate and ammonium humate; and the ratio of said first monomer to said second monomer in said reaction is an amount in the range of from about 0.3 to about 2.0 moles of said first monomer per mole of said second monomer.

2. The product of the method of claim 1.

3. The method of claim 1 wherein said first monomer is 2-acrylamido-2-methylpropanesulfonic acid and the sodium, calcium and ammoniuim salts thereof, and the second monomer is selected from acrylamide, methacrylamide, N-methylacrylamide, N-i-propylacrylamide, N-i-propylmethacrylamide, N-t-butylacrylamide, N-t-butylmethacrylamide, N,N-dimethylacrylamide and N,N-dimethylmethacrylamide.

4. The method of claim 1 wherein said first monomer is the sodium salt of 2-acrylamido-2-methylpropanesulfonic acid and the second monomer is acrylamide and said molecular weight control agent is potassium humate.

5. The method of claim 4 wherein said ratio of said first monomer to said second monomer is about 0.72 moles of said first monomer per mole of said second monomer.

6. A method of making a cementing composition, said method being comprised of combining hydraulic cement with a cementing fluid loss additive made by the method consisting of combining a first monomer with a second monomer in a polymerization reaction in the presence of a molecular weight control agent and at a pH in the range of from about 7.0 to about 10.5; wherein: said molecular weight control agent is selected from humic acid, potassium humate, sodium humate and ammonium humate; and the ratio of said first monomer to said second monomer in said reaction is an amount in the range of from about 0.3 to about 2.0 moles of said first monomer per mole of said second monomer; and further wherein: said first monomer is 2-acrylamido-2-methylpropanesulfonic acid and the sodium, calcium and ammoniuim salts thereof, and said second monomer is selected from acrylamide, methacrylamide, N-methylacrylamide, N-i-propylacrylamide, N-i-propylmethacrylamide, N-t-butylacrylamide, N-t-butylmethacrylamide, N,N-dimethylacrylamide and N,N-dimethylmethacrylamide.

7. The cementing composition product of the method of claim 6.

8. The cementing composition of claim 7 mixed with water to form a slurry containing in the range of from about 35 to about 55 pounds of water per 100 pounds of said hydraulic cement in said cementing composition.

9. The method of claim 6 wherein said first monomer is the sodium salt of 2-acrylamido-2-methylpropanesulfonic acid and the second monomer is acrylamide and said molecular weight control agent is potassium humate.

10. The method of claim 9 wherein said ratio of said first monomer to said second monomer in said reaction is about 0.72 moles of said first monomer per mole of said second monomer.

Description

DESCRIPTION OF THE INVENTION

(1) The cementing fluid loss additive of this invention is a synthetic copolymer made by the reaction of two different vinylamide derivatives. The reaction is performed in the presence of a molecular weight control material and at a pH in the range of from about 7.0 to about 10.5 and preferably in the range of from about 9.0 to about 10.5. The first vinylamide derivative is a monomer which does include a sulfonic acid function in its structure. The second vinylamide derivative is a monomer which does not include a sulfonic acid function in its structure.

(2) Vinylamide monomers useful herein which do include a sulfonic acid function include 2-acrylamido-2-methylpropanesulfonic acid and the sodium, calcium and ammonium salts thereof. An aqueous solution containing about 50 percent by weight of active monomer can be employed in the reaction in an amount in the range of from about 1 to about 35, and preferably in an amount in the range of from about 10 to about 20 percent by weight of the reaction mass.

(3) Vinylamide monomers useful herein which do not include a sulfonic acid function include acrylamide, methacrylamide, N-methylacrylamide, N-i-propylacrylamide, N-i-propylmethacrylamide, N-t-butylacrylamide, N-t-butylmethacrylamide, N,N-dimethylacrylamide and N,N-dimethylmethacrylamide. An aqueous solution containing about 52 percent by weight of active monomer, can be employed in the reaction in an amount in the range of from about 1 to about 30 percent by weight of the reaction mass.

(4) The process for making the cementing fluid loss additive of this invention is comprised of the steps of:

(5) (a) Providing a reaction vessel equipped with means for introducing material into the reaction vessel, means for stirring the contents of the reaction vessel, means for heating the contents of the reaction vessel, means for measuring the temperature of the contents of the reaction vessel, and means for introducing nitrogen into the reaction vessel;

(6) (b) Introducing into the reaction vessel a quantity of deionized water, and stirring the contents of the reaction vessel at about 150 revolution per minute;

(7) (c) Introducing into the reaction vessel a quantity of a monomer of a vinylamide derivative which does contain a sulfonic acid function, such as the sodium salt of 2-acrylamido-2-methylpropanesulfonic acid;

(8) (d) Introducing into the reaction vessel a quantity of a reaction accelerator, such as potassium chloride;

(9) (e) Introducing into the reaction vessel a quantity of a molecular weight control agent, such as potassium humate, which could also function as a colloidal agent;

(10) (f) Introducing into the reaction vessel a quantity of a vinylamide derivative which does not contain a sulfonic acid function, such as acrylamide;

(11) (g) Introducing into the reaction vessel a quantity of a base material, such as sodium hydroxide, to adjust the pH of the contents of the reaction vessel;

(12) (h) Heating the contents of the reaction vessel to a value of about 114 F.;

(13) (i) Introducing nitrogen into the reaction vessel for about one hour to purge the reaction vessel of oxygen;

(14) (j) Introducing into the reaction vessel, after the contents of the reaction vessel have attained a temperature of about 114 F. and after the vessel has been purged, a quantity of a chain transfer agent, such as tetraethylene pentamine;

(15) (k) Introducing into the reaction vessel a quantity of a polymerization initiator, such as sodium persulfate;

(16) (l) Monitoring the reaction and measuring the temperature of the contents of the reaction vessel every two minutes until the temperature attains a maximum value;

(17) (m) Adjusting the temperature of the contents of the reaction vessel to a value of about 160 F.;

(18) (n) Maintaining the temperature of the contents of the reaction vessel at about 160 F. for about two hours after addition of the polymerization initiator to the reaction vessel;

(19) (o) Discontinuing stirring, heating and purging;

(20) (p) Permitting the contents of the reaction vessel to cool to room temperature; and

(21) (q) Drying the solution in the reaction vessel to recover the dry cementing fluid loss additive of this invention. This step is optional. The fluid loss additive of this invention can be employed in an aqueous solution.

(22) One cementing fluid loss additive of this invention is the copolymer product of the polymerization reaction of the sodium salt of 2-acrylamido-2-methylpropanesulfonic acid (the first vinylamide derivative) and acrylamide (the second vinylamide derivative) in the presence of potassium humate. The ratio of the first vinylamide derivative to the second vinylamide derivative is an amount in the range of from about 0.3 to about 2.0 and preferably about 0.72 moles of the first vinylamide derivative per mole of the second vinylamide derivative. The ratio of the first vinylamide derivative to potassium humate is an amount in the range of from about 1.0 to about 25 and preferably about 13.3 moles of the first vinylamide derivative per mole of potassium humate.

(23) The reaction accelerator can be present in the reaction in an amount of up to about 10 percent by weight of the reaction mass. Useful reaction accelerators include potassium chloride, sodium chloride and calcium chloride.

(24) A 12 percent aqueous solution of molecular weight control agent can be present in the reaction in an amount in the range of from about 1 to about 12 percent by weight of the reaction mass. Useful molecular weight control agents include humic acid, potassium humate, sodium humate and ammonium humate.

(25) A 50 percent aqueous solution of a base material can be present in the reaction in an amount in the range of from about 0.01 to about 3 percent by weight of the reaction mass. Useful base materials employed to adjust the pH of the reaction mass include sodium hydroxide, potassium hydroxide and ammonium hydroxide.

(26) The chain transfer agent can be present in the reaction in an amount in the range of from about 0.05 to about 5 percent by weight of the reaction mass. Useful chain transfer agents include tetraethylenepentamine, diethytriamine, triethyltetramine and mercaptoethanol.

(27) The polymerization initiator can be present in the reaction in an amount in the range of from about 0.05 to about 0.6 percent by weight of the reaction mass. Useful polymerization initiators include sodium persulfate and ammonium persulfate.

(28) A cementing fluid loss additive was prepared in accordance with the process described above. Table A defines and describes materials employed in the process. Table A1 defines the recipe employed in the process for making a cementing fluid loss additive of this invention.

(29) TABLE-US-00001 TABLE A Ingredients Employed in Making Cementing Fluid Loss Additive (FLA) Definitions, Functions, Activities and Molecular Weights Molecular Item Ingredient Definition Function Weight 1 D.I Water de-ionized water diluent, reaction 18.01 medium 2 ATBS 2-acrylamido-2- first 229.23 propanesulfonic acid, monomer sodium salt, 50% reactant aqueous solution 3 KCI potassium chloride, reaction 74.55 100% active accelerator 4 K Humate potassium humate, molecular 258.35 12% active solution weight control 5 ACR acrylamide, 52% second 71.08 aqueous solution monomer reactant 6 NaOH sodium hydroxide, base neutralizer 40.01 50% active solution 7 D.I. Water de-ionized water diluent, reaction 18.01 medium 8 TEPA tetraethylenepentamine, chain transfer 189.30 100% active agent 9 D.I. Water de-ionized water diluent, reaction 18.01 medium 10 SP sodium persulfate, polymerization 238.10 100% active initiator

(30) TABLE-US-00002 TABLE A1 Cementing Fluid Loss Additive (FLA) Recipe Mole Moles Quantity Weight Moles percent ATBS grams percent active active per mole Item Ingredient (fn 1) (fn 2) (fn 3) (fn 4) (fn 5) 1 D.I. Water 745.7600 62.1468 41.4081 90.8411 0.0093 2 ATBS 176.6972 14.7248 0.3854 0.8455 1.0000 3 KCL 101.6514 8.4710 1.3635 2.9913 0.2827 4 K Humate 62.3853 5.1988 0.0290 0.0636 13.3007 5 ACR 73.3945 6.1162 0.5369 1.1779 0.7178 6 NaOH 0.5872 0.0489 0.0073 0.0161 52.5259 7 D.I. Water 17.7982 1.4832 0.9882 2.1680 0.3900 8 TEPA 0.9174 0.0765 0.0048 0.0106 79.5253 9 D.I. Water 15.0459 1.2538 0.8354 1.8327 0.4613 10 SP 5.7600 0.4800 0.0242 0.0531 15.9318 Totals 1199.9970 100.0000 45.5830 100.0000 Footnotes: 1. Weight of material added to reaction vessel, see Table A. 2. Weight percent of material added to reaction vessel. 3. Moles of active material added to reaction vessel. 4. Mole percent of active material added to reaction vessel. 5. Active moles of ATBS per mole of designated active material.

(31) The invention provides a method of making a cementing composition containing the cementing fluid loss additive of this invention, and a slurry containing the cementing composition. The method of making the cementing composition is comprised of mixing dry ingredients in any convenient order to produce a dry product. The method of making the slurry is comprised of mixing the cementing composition with water in any convenient order.

(32) Cementing compositions and cement slurries were prepared. Table B defines and describes materials employed in the preparation of cementing compositions and cementing slurries.

(33) Table B1 provides recipes for a total of six dry cementing compositions. Compositions 1, 2, 4, 5, and 6 include the dry cementing fluid loss additive made as described in Table A1. Composition 3 does not include any ingredient other than cement.

(34) Table B2 provides recipes for making a total of nine cementing slurries containing the compositions described in Table B1.

(35) TABLE-US-00003 TABLE B Ingredients Employed in Making Cementing Composition Definitions, Functions, Activities and Molecular Weights Item Ingredient Definition Function 1 Class H Hydraulic Cement basic well cement for cement API Spec. 10 use from surface to 8000 feet 2 FW Fresh Water water mixed with 0% salt cement composition to form slurry 3 SSW Saturated Salt Water water mixed with cement water containing composition to form slurry 38% sodium chloride (77 F.) 4 SA Dry blend, 80 wt added to cement parts diutan composition to help gum, 240 wt suspend particle sof parts silica flour cement in slurry 5 FLA Fluid Loss Additive added to cement dried copolymer composition to product produced by reduce loss of water recipe of Table A1 from slurry 6 SG Sodium gluconate cement set time intensifier 7 SGCLS Dry blend, 25 wt cement set time retarder parts SG, and retarder intensifier 75 wt. parts CLS 8 SSA - 1 silica flour strength stabilizing agent 9 CLS calcium added to cement lignosulfonate composition to retard the set time of slurry 10 TTA tartaric acid added to cement composition to retard the set time of slurry

(36) TABLE-US-00004 TABLE B1 Cementing Compositions CEMENTING COMPOSITION grams Ingredient (fn 2 & 3) (fn 1) 1 2 3 4 5 6 Class H 100.00 100.00 100.00 100.00 100.00 100.000 cement FLA 0.60 0.60 0.60 0.40 0.700 SGCLS 0.30 0.30 SA 0.05 0.075 SSA - 1 35.000 CLS 1.200 TTA 0.600 TOTAL 100.90 100.95 100.00 100.60 100.40 137.575 Footnotes: 1. See Table B for definitions of ingredients. 2. See Table A1 for recipe of fluid loss additive (FLA) 3. Weights based on 100 grams of cement.

(37) TABLE-US-00005 TABLE B2 Cementing Slurries Cementing Slurry grams Ingredient 1 2 3 4 5 6 7 8 9 Comp. 1 100.90 100.90 Comp. 2 101.10 Comp. 3 100.00 100.00 Comp. 4 100.60 100.60 Comp. 5 100.40 Comp. 6 137.53 FW 38.00 38.00 38.00 53.00 53.00 53.00 38.00 SSW 38.00 38.00 Total 138.90 138.90 139.10 138.00 138.60 153.00 153.40 153.60 175.53 Weight Slurry 16.50 16.50 16.50 16.50 16.50 15.00 15.00 15.00 17.40 Density lb/gal

(38) The cementing slurries described in Table B2 were tested to determine consistency and API fluid loss. Consistency was measured at 100 and 180 degrees F. Fluid loss was measured at 100, 180, 250 and 350 degrees F. The test results are reported in Table B3.

(39) TABLE-US-00006 TABLE B3 Results From Testing of Cement Slurries Fann Viscometer Data API Fluid Slurry (Rotor R1, Bob B1 Spring F1) Loss 180 F. rpm 180 F. 300 200 100 6 3 cc/30 min 1 97 65 32 2 1 42 2 56 37 17 1 1 44 3 91 66 39 11 10 68 100 F. rpm 100 F. 300 200 100 6 3 cc/30 min 4 133 115 92 23 15 5 132 95 54 7 5 89 6 31 27 21 10 6 7 27 18 9 0 0 113 8 27 17 8 0 0 250 F. cc/30 min 9 67 350 F. cc/30 min 9 97

(40) The data in Table B3 illustrates that the cementing fluid additive of this invention does control fluid loss at temperatures up to 350 F.