Oil and gas well fracturing (frac) water treatment process

• US 20050098504A1
• Filed: 09/23/2004
• Published: 05/12/2005
• Est. Priority Date: 12/11/2002
• Status: Abandoned Application

• Current Assignee: Davnor Water Treatment Technologies Limited
• Original Assignee: Davnor Water Treatment Technologies Limited
• Inventors: Manz, David Harold, Mahmood, Tariq, Khanam, Hamida Azhar
• Application Number:
  US10/947,226
• Publication Number:
  US 20050098504A1
• Time in Patent Office: Days
• US Class Current: 210/721
• CPC Class Codes: C02F 1/001 Processes for the treatment of water whereby the filtration technique is of importance C02F1/44 takes precedence; construction of filters in general B01D24/00 - B01D41/00
• CPC Class Codes: C02F 1/008 Control or steering systems not provided for elsewhere in subclass C02F
• CPC Class Codes: C02F 1/52 by flocculation or precipitation of suspended impurities C02F1/463 takes precedence
• CPC Class Codes: C02F 1/66 by neutralisation; pH adjustment for degassing C02F1/20; using ion-exchange C02F1/42; for flocculation or precipitation of suspended impurities C02F1/52; for removing dissolved compounds C02F1/58
• CPC Class Codes: C02F 1/72 by oxidation C02F1/4672 takes precedence
• CPC Class Codes: C02F 2103/10 from quarries or from mining activities
• CPC Class Codes: C02F 2209/006 comprising a software program or a logic diagram
• CPC Class Codes: C02F 9/00 Multistage treatment of water, waste water or sewage
• CPC Class Codes: C10G 33/04 with chemical means

Abstract

This invention relates to a novel process for treating and removing undesirable impurities from oil and gas well fracturing fluid. A method for treating fracturing water comprising: (a) passing contaminated fracturing water containing solids and liquid through a mechanical separator to remove solids from the liquid; (b) treating the fracturing water liquid with an alkaline agent to increase the pH of the liquid to a level of above 9; (c)) adding a coagulant to the fracturing water to form an agglomerate and separating the agglomerate from the fracturing water; (d) reducing the pH of the fracturing water of step (c)) to a level of less than about 5.5; and (e) adding an oxidizing agent to the fracturing water of step (d) to oxidize oxidizable impurities in the fracturing water.

Claims

1. A method of treating reclaimed contaminated oil and well fracturing water comprising:

(a) passing the contaminated fracturing water containing solids and liquid through a separator to remove solids from the liquid;

(b) treating the fracturing water liquid with an alkaline agent to increase the pH of the liquid to a level above about 9;

(c) adding a coagulant to the fracturing water liquid to form an agglomerate and separating the agglomerate from the fracturing water liquid;

(d) reducing the pH of the fracturing water liquid to a level of less than about 5.5;

(e) adding an oxidizing agent to the fracturing water liquid to oxidize and insolubilize oxidizable impurities in the fracturing water liquid; and

(f) removing the insolubilized impurities from the liquid.

2. A method as claimed in claim 1 wherein the oxidation and acidification steps (d) and (e) are performed in reverse order.

3. A method as claimed in claim 1 wherein hydrated lime is added at step (b) to increase the pH of the fracturing water to a level of above about 9.

4. A method as claimed in claim 1 wherein the coagulant in step (c) is polyaluminum chloride.

5. A method as claimed in claim 1 wherein both a flocculating agent and a coagulant are added to the fracturing water liquid in step (c)).

6. A method as claimed in claim 1 wherein an inorganic acid is added to the fracturing water liquid at step (d) to reduce the pH to less than 5.5.

7. A method as claimed in claim 6 wherein the inorganic acid is hydrochloric acid.

8. A method as claimed in claim 1 wherein the insolubilized impurities in step (f) are removed by passing the liquid through a sand water filter or a sediment cartridge filter.

9. A method as claimed in claim 1 wherein the oxidation agent in step (e) is potassium permanganate.

10. A method as claimed in claim 1 wherein after step (c)) and before step (d), the liquid is neutralized by reducing the pH to about 7.0.

11. A method as claimed in claim 10 wherein the neutralization and oxidation steps (d) and (e) are performed in reverse order.

12. A method as claimed in claim 1 wherein the fracturing water liquid that remains after oxidized insolubilized impurities are removed in step (f) is subjected to a second clarification step which includes a second acidification step, followed by a second oxidation step.

13. A method as claimed in claim 12 wherein the acid used in the second acidification step is hydrochloric acid.

14. A method as claimed in claim 12 wherein the oxidizing agent used in the second oxidation step is potassium permanganate.

15. A method as claimed in claim 12 wherein a coagulant is added to the fracturing water liquid during the second clarification step.

16. A method as claimed in claim 13 wherein the coagulant is polyaluminum chloride.

17. A method as claimed in claim 15 wherein a flocculant is also added to the fracturing water liquid during the second clarification step.

18. A method as claimed in claim 17 wherein the fracturing water liquid from the second clarification step is neutralized before being reused as water.

19. A method as claimed in claim 18 wherein the water that is produced from the second clarification step is treated by being passed through a sand water filter or a sediment cartridge filter to remove remaining particles in the liquid.

20. A method of treating reclaimed contaminated fracturing water comprising:

(a) passing the contaminated fracturing water containing solids and liquid through a mechanical separator to remove solids from the liquid;

(b) treating the fracturing water liquid with a hydrated lime to increase the pH of the liquid to a level of above about 9;

(c)) adding polyaluminum chloride to the fracturing water liquid to form an agglomerate and separating the agglomerate from the fracturing water liquid;

(d) reducing the pH of the fracturing water liquid to a level of less than about 5.5 by adding hydrochloride acid to the liquid;

(e) adding potassium permanganate to the fracturing water to oxidize and insolubilize oxidizable impurities in the fracturing water liquid; and

(f) removing the insolubilized impurities from the liquid.