TREATMENT OF SUBTERRANEAN FORMATIONS

Abstract

A method of treating a subterranean formation by contacting the formation with the following: (a) ammonium compound; (b) an oxidizing agent selected from a perchlorate or a nitrite or combinations thereof; and (c) sulfamic acid.

Claims

1-34. (canceled)

35. A method of treating a subterranean formation, the method comprising contacting the formation with the following: (a) ammonium sulfamate; and (b) an oxidizing agent selected from a perchlorate or a nitrite or combinations thereof; and/or (c) an acid.

36. The method according to claim 35, wherein the method comprises treating the formation to create or enhance a fracture in the formation.

37. The method according to claim 35, wherein said oxidizing agent comprises a nitrite.

38. The method according to claim 35, wherein said oxidizing agent is sodium nitrite and wherein said ammonium sulfamate and said oxidizing agent are contacted so they react and nitrogen is generated in the formation.

39. The method according to claim 35, wherein a ratio (A) defined as the number of moles of ammonium sulfamate divided by the number of moles of nitrite contacted with the formation and/or reacted in the formation is in the range 0.2 to 0.6.

40. The method according to claim 35, wherein the method comprises contacting the formation with said ammonium sulfamate, said oxidizing agent and an acid (AA), wherein said acid (AA) is arranged to react to produce a gas, wherein the gas produced includes carbon and/or nitrogen atoms originating in the acid (AA).

41. The method according to claim 40, wherein said acid (AA) is treated in the method to produce gas which supplements gas produced by reaction of said ammonium sulfamate and said oxidizing agent.

42. The method according to claim 41, wherein said acid (AA) includes a moiety ##STR00004## and wherein said acid (AA) includes a nitrogen-atom.

43. The method according to claim 41, wherein said acid (AA) is selected from sulfamic acid and ammonium bisulfate; and mixtures of sulfamic acid and ammonium bisulfate.

44. The method according to claim 35, wherein a ratio (B) defined as the number of moles of ammonium sulfamate divided by the total number of moles of acid contacted with the formation and/or reacted with sulfamate and oxidizing agent in the formation is in the range 0.4 to 1.1; and/or wherein a ratio (C) defined as the number of moles of ammonium sulfamate divided by the sum of the number of moles of one or more acids which are arranged to react with other materials contacted with the formation to produce a gas is in the range 0.4 to 1.1; and/or wherein a ratio (E) defined as the number of moles of ammonium sulfamate divided by the sum of the number of moles of sulfamic acid and ammonium bisulfate contacted with the formation is in the range 0.4 to 1.1.

45. The method according to claim 35, wherein a ratio (D) defined as the number of moles of ammonium sulfamate divided by the sum of the number of moles of one or more acids which include a nitrogen atom contacted with the formation and/or reacted with ammonium sulfamate and/or said oxidizing agent in the formation is in the range 0.4 to 1.1; and/or wherein a ratio (H) defined as the number of moles of oxidizing agent divided by the total number of moles of acid contacted with the formation and/or reacted with said ammonium sulfamate is in the range 0.9 to 3.5; and/or wherein a ratio (I) defined as the number of moles of oxidizing agent divided by the sum of the number of moles of one or more acids which are arranged to react to produce a gas are in the range 0.9 to 3.5.

46. The method according to claim 35, wherein said ammonium sulfamate is provided as a slurry, an emulsion or a solution; wherein said oxidizing agent is provided in water; and wherein the method includes contacting the formation with an aqueous solution or slurry of an acid (AA).

47. The method according to claim 35, wherein in the method the sum of the wt % of a formulation (F1) comprising said ammonium sulfamate, a formulation (F2) comprising said oxidizing agent and a formulation (F3) comprising an acid (AA) introduced into the formation is at least 98 wt %, of the total weight of materials introduced into the formation as part of the fracturing of the formation by production of gas within the formation.

48. The method according to claim 35, wherein the method comprises contacting the formation with a formulation (F5) which is aqueous and comprises said ammonium sulfamate and an acid (AA) which is selected from sulfamic acid and ammonium bisulfate; and mixtures of sulfamic acid and ammonium bisulfate.

49. The method according to claim 35, wherein: the sum of the total weight in grams (g) of ammonium sulfamate, oxidizing agent and acid(s) introduced into the formation is herein referred to as SUM-W; the sum of the total volume in cm.sup.3 of gas generated by reaction of ammonium sulfamate, oxidizing agent and said acid(s) is herein referred to as SUM-V; wherein, in the method, the Reaction Efficiency is defined as SUM-V divided by SUM-W; wherein the Reaction Efficiency is at least 100 cm.sup.3/g.

50. The method according to claim 35, wherein formulations comprising ammonium sulfamate, oxidizing agent and/or acid include one or more co-solvents selected from methanol or formamide; and/or the method comprises producing pulses within the formation, for example by controlling contact and/or amounts of ammonium sulfamate, oxidizing agent and/or acid within the formation.

51. A mixture within a subterranean formation, the mixture comprising: (a) ammonium sulfamate; (b) an oxidizing agent selected from a perchlorate or a nitrite or combinations thereof; and (c) an acid.

52. A mixture according to claim 51, wherein said mixture includes ammonium sulfamate, an oxidizing agent which is a nitrite and an acid (AA) which is selected from sulfamic acid and ammonium bisulfate; and mixtures of sulfamic acid and ammonium bisulfate.

53. A method of treating a subterranean formation, the method comprising contacting the formation with the following: (a) ammonium sulfamate; (b) an oxidizing agent selected from a perchlorate or a nitrite or combinations thereof; and (c) an acid; wherein a ratio (B) defined as the number of moles of ammonium sulfamate divided by the total number of moles of acid contacted with the formation and/or reacted with said ammonium sulfamate and oxidizing agent in the formation is greater than 0 and is 10 or less; and wherein a ratio (A) defined as the number of moles of ammonium sulfamate divided by the number of moles of said oxidizing agent contacted with the formation is from 0.05 to 2.0.

54. The method according to claim 53, wherein said oxidizing agent is sodium nitrite and said acid is selected from sulfamic acid and ammonium bisulfate; and mixtures of sulfamic acid and ammonium bisulfate.

55. The method according to claim 54, wherein said ratio (A) is in the range 0.2 to 0.6; and said ratio (B) is in the range 0.4 to 1.1.

Description

EXAMPLE 1—GENERAL PROCEDURE FOR UNDERTAKING REACTIONS

[0124] An ammonium compound and a nitrite or perchlorate-containing compound were added to a round-bottom flask and dissolved in the minimum quantity of water. Suitable apparatus to measure gas released was arranged in position and the solution heated with stirring to 75° C. Once the solution had reached 75° C., a selected amount of acid also heated to 75° C. was injected into the reaction vessel. The quantity of gas generated was recorded.

[0125] In Examples 2 to 4, use of ammonium sulfamate as the ammonium compound was compared with use of other ammonium compounds, namely ammonium chloride and ammonium bicarbonate.

EXAMPLES 2 AND 3—COMPARISON BETWEEN AMMONIUM SULFAMATE AND AMMONIUM CHLORIDE USING SULFAMIC ACID

[0126] In order to compare use of ammonium sulfamate with ammonium chloride, ammonium sulfamate was reacted with sulfamic acid (Example 2) and the gas volume determined. For comparison purposes, the same reaction and assessment was undertaken wherein the ammonium sulfamate was replaced with ammonium chloride (Example 3). In each case, 30 mmol of sodium nitrite was used as oxidizing agent.

[0127] Results are provided in the table below from which it will be noted that significantly more gas is generated when ammonium sulfamate is used compared to use of the other ammonium compounds.

TABLE-US-00001 Gas generated on reaction with acid/ Example No. Ammonium Salt Acid cm3 2 ammonium sulfamate sulfamic 1320 3 ammonium chloride sulfamic  960 (comparative)

EXAMPLES 4 TO 6—COMPARISON BETWEEN AMMONIUM SULFAMATE OTHER AMMONIUM COMPOUNDS USING HYDROCHLORIC ACID

[0128] The procedure described for Examples 2 and 3 was followed except hydrochloric acid was used instead of sulfamic acid. Results are provided in the table below.

TABLE-US-00002 Gas generated on reaction with acid/ Example No. Ammonium Salt Acid cm3 4 ammonium sulfamate hydrochloric 920 5 ammonium chloride hydrochloric 330 (comparative) 6 ammonium bicarbonate hydrochloric 560 (comparative)

[0129] Again, it should be noted that significantly more gas was generated when ammonium sulfamate was used compared to use of other ammonium compounds.

[0130] It is found that the solubility of sulfamic acid is relatively low. To address this, mixtures of sulfamic acid and ammonium bisulfate (which is extremely soluble) were used with the ammonium sulfamate as described below for Examples 7 to 18.

EXAMPLE 7

[0131] 2.9 mL of an aqueous solution of ammonium sulfamate (5 mmol) and sodium nitrite (20 mmol) was added to a round-bottom flask. Suitable apparatus to measure gas release was arranged in position and the solution heated to 75° C. Once the solution reached 75° C., 0.83 mL of a 12 M aqueous solution of hydrochloric acid (10 mmol), heated to the same temperature, was injected into the reaction vessel. The quantity of gas generated was recorded.

EXAMPLE 8

[0132] 2.9 mL of an aqueous solution of ammonium sulfamate (5 mmol) and sodium nitrite (20 mmol) was added to a round-bottom flask. Suitable apparatus to measure gas release was arranged in position and the solution heated to 75° C. Once the solution reached 75° C., 4.0 mL of an aqueous solution containing sulfamic acid (7.5 mmol) and ammonium bisulfate (2.5 mmol), heated to the same temperature, was injected into the reaction vessel. The quantity of gas generated was recorded.

EXAMPLE 9

[0133] 2.9 mL of an aqueous solution of ammonium sulfamate (5 mmol) and sodium nitrite (20 mmol) was added to a round-bottom flask. Suitable apparatus to measure gas release was arranged in position and the solution heated to 75° C. Once the solution reached 75° C., 3.0 mL of an aqueous solution containing sulfamic acid (5 mmol) and ammonium bisulfate (5 mmol), heated to the same temperature, was injected into the reaction vessel. The quantity of gas generated was recorded.

EXAMPLE 10

[0134] 2.9 mL of an aqueous solution of ammonium sulfamate (5 mmol) and sodium nitrite (20 mmol) was added to a round-bottom flask. Suitable apparatus to measure gas release was arranged in position and the solution heated to 75° C. Once the solution reached 75° C., 1.95 mL of an aqueous solution containing sulfamic acid (2.5 mmol) and ammonium bisulfate (7.5 mmol), heated to the same temperature, was injected into the reaction vessel. The quantity of gas generated was recorded.

EXAMPLE 11

[0135] 2.2 mL of an aqueous solution containing ammonium sulfamate (7 mmol), sulfamic acid (1 mmol) and ammonium bisulfate (9 mmol) were added to a round-bottom flask. Suitable apparatus to measure gas release was arranged in position and the solution heated to 75° C. Once the solution reached 75° C., 2.2 mL of an aqueous solution containing sodium nitrite (20 mmol), heated to the same temperature, was injected into the reaction vessel. The quantity of gas generated was recorded.

EXAMPLE 12

[0136] 2.5 mL of an aqueous solution containing ammonium sulfamate (5 mmol), sulfamic acid (2.5 mmol) and ammonium bisulfate (7.5 mmol) were added to a round-bottom flask. Suitable apparatus to measure gas release was arranged in position and the solution heated to 75° C. Once the solution reached 75° C., 2.5 mL of an aqueous solution containing sodium nitrite (20 mmol), heated to the same temperature, was injected into the reaction vessel. The quantity of gas generated was recorded.

EXAMPLE 13

[0137] 2.2 mL of an aqueous solution containing ammonium sulfamate (6.25 mmol), sulfamic acid (1.5 mmol) and ammonium bisulfate (8.5 mmol) were added to a round-bottom flask. Suitable apparatus to measure gas release was arranged in position and the solution heated to 75° C. Once the solution reached 75° C., 2.2 mL of an aqueous solution containing sodium nitrite (20 mmol), heated to the same temperature, was injected into the reaction vessel. The quantity of gas generated was recorded.

EXAMPLE 14

[0138] 2.2 mL of an aqueous solution containing ammonium sulfamate (6.25 mmol), sulfamic acid (1.75 mmol) and ammonium bisulfate (7 mmol) were added to a round-bottom flask. Suitable apparatus to measure gas release was arranged in position and the solution heated to 75° C. Once the solution reached 75° C., 2.2 mL of an aqueous solution containing sodium nitrite (20 mmol), heated to the same temperature, was injected into the reaction vessel. The quantity of gas generated was recorded.

EXAMPLE 15

[0139] 2.2 mL of an aqueous solution containing ammonium sulfamate (5.5 mmol), sulfamic acid (2.63 mmol) and ammonium bisulfate (4.88 mmol) were added to a round-bottom flask. Suitable apparatus to measure gas release was arranged in position and the solution heated to 75° C. Once the solution reached 75° C., 2.2 mL of an aqueous solution containing sodium nitrite (20 mmol), heated to the same temperature, was injected into the reaction vessel. The quantity of gas generated was recorded.

EXAMPLE 16

[0140] 2.2 mL of an aqueous solution containing ammonium sulfamate (6 mmol), sulfamic acid (2.24 mmol) and ammonium bisulfate (4.76 mmol) were added to a round-bottom flask. Suitable apparatus to measure gas release was arranged in position and the solution heated to 75° C. Once the solution reached 75° C., 2.2 mL of an aqueous solution containing sodium nitrite (20 mmol), heated to the same temperature, was injected into the reaction vessel. The quantity of gas generated was recorded.

EXAMPLE 17

[0141] 2.2 mL of an aqueous solution containing ammonium sulfamate (6.25 mmol), sulfamic acid (2.50 mmol) and ammonium bisulfate (4.25 mmol) were added to a round-bottom flask. Suitable apparatus to measure gas release was arranged in position and the solution heated to 75° C. Once the solution reached 75° C., 2.2 mL of an aqueous solution containing sodium nitrite (20 mmol), heated to the same temperature, was injected into the reaction vessel. The quantity of gas generated was recorded.

EXAMPLE 18

[0142] 2.2 mL of an aqueous solution containing ammonium sulfamate (6.25 mmol), sulfamic acid (2.50 mmol) and ammonium bisulfate (3.75 mmol) were added to a round-bottom flask. Suitable apparatus to measure gas release was arranged in position and the solution heated to 75° C. Once the solution reached 75° C., 2.2 mL of an aqueous solution containing sodium nitrite (20 mmol), heated to the same temperature, was injected into the reaction vessel. The quantity of gas generated was recorded.

[0143] Results for Examples 7 to 18 are provided in the table below.

TABLE-US-00003 mmol mmol mmol Gas Total Efficiency/ Example NH.sub.4NH.sub.2SO.sub.3 NaNO.sub.2 Acid acid generated/cm.sup.3 mass/g cm.sup.3 per g 7 5 20 Hydrochloric 10.0 460 2.95 156 8 5 20 Sulfamic/ammonium bisulfate (75:25) 10.0 740 2.97 249 9 5 20 Sulfamic/ammonium bisulfate (50:50) 10.0 700 3.01 232 10 5 20 Sulfamic/ammonium bisulfate (25:75) 10.0 660 3.06 216 11 7 20 Sulfamic/ammonium bisulfate (10:90) 10.0 630 3.31 190 12 5 20 Sulfamic/ammonium bisulfate (25:75) 10.0 660 3.06 216 13 6.25 20 Sulfamic/ammonium bisulfate (15:85) 10.0 640 3.22 199 14 6.25 20 Sulfamic/ammonium bisulfate (20:80) 8.8 660 3.07 215 15 5.5 20 Sulfamic/ammonium bisulfate (35:65) 7.5 660 2.82 234 16 6 20 Sulfamic/ammonium bisulfate (32:68) 7.0 665 2.83 235 17 6.25 20 Sulfamic/ammonium bisulfate (37:63) 6.8 670 2.83 237 18 6.25 20 Sulfamic/ammonium bisulfate (40:60) 6.3 650 2.77 235

[0144] Thus, ammonium sulfamate may advantageously be used to generate relatively large quantities of gas and, suitably, without generation of any carbon dioxide (or any carbon-containing gas).

[0145] The invention is not restricted to the details of the foregoing embodiment(s). The invention extends to any novel one, or any novel combination, of the features disclosed in this specification (including any accompanying claims, abstract and drawings), or to any novel one, or any novel combination, of the steps of any method or process so disclosed.