SAGD saline water system optimization

Patent metadata

Field	Value
Publication number	US-11034604-B2
Application number	US-201816156957-A
Country	US
Kind code	B2
Filing date	Oct 10, 2018
Priority date	Oct 11, 2017
Publication date	Jun 15, 2021
Grant date	Jun 15, 2021

Abstract

A new water treatment system for SAGD operations is disclosed. Instead of treating both produced water and recycled water using warm lime softening systems, the recycled water is combined with saline water in a cold lime softening system. This results in slightly warmed reactions that require less chemicals during the lime softening process while also allowing for larger volumes of treated produced water to be generated by the warm lime softening system.

First claim

The invention claimed is:

1. A water treatment system for SAGD comprising:
a) a saline water stream;
b) a fresh water stream,
c) a produced water stream;
d) a warm lime softener treatment unit comprising a warm lime softener system fluidly connected to a first ion exchange system, which is fluidly connected to at least one filter, said warm lime softener unit having an inlet for receiving and treating said produced water stream, a chemical injection inlet for receiving softening chemicals, a first outlet for a treated produced water stream, and a second outlet for a first regeneration stream;
e) a cold lime softener treatment unit comprising a cold lime softener system fluidly connected to a second ion exchange system, which is fluidly connected to at least one filter, said cold lime softener unit having a cold lime softener inlet, a chemical injection inlet for receiving softening chemicals, a first outlet for a first treated water stream, and a second outlet for a second regeneration stream;
f) one or more steam generators fluidly connected to said first outlet of said warm lime softener treatment unit and said first outlet of said cold lime softener treatment unit such that said steam generators receive and heat said first treated water stream and said treated produced water stream, said steam generators having a first outlet for steam and a second outlet for a blowdown stream; and,
g) a vessel fluidly connected to said second outlet of said warm lime softener treatment unit, said second outlet of said cold lime softener treatment unit, and second outlet of said steam generators, such that said vessel mixes said saline water stream, said fresh water stream, said first regeneration stream, said second regeneration stream, and said blowdown stream to form a stream to be treated, said vessel in fluid communication with said cold lime softener inlet, wherein the stream to be treated is received by said cold lime softener inlet in said cold lime softener treatment unit for treatment by said cold lime softener treatment unit.

2. The system in claim 1 , wherein said blowdown stream in said stream to be treated raises the temperature and pH of said cold lime softener treatment unit as compared to cold lime softener treatment units that do not use a blowdown stream.

3. The system in claim 2 , wherein the raise in temperature is 5-50° C.

4. The system in claim 2 , wherein said blowdown stream in said stream to be treated raises the temperature of said cold lime softener treatment unit to 30° C.

5. The system in claim 2 , wherein the raise in temperature and pH reduces the amount of softening chemicals required for treatment by the cold lime softener treatment unit by at least 20%.

6. The system in claim 1 , wherein said first ion exchange system and said second ion exchange system each comprises a weak acid cation exchanger.

7. The system in claim 1 , wherein said stream to be treated has a constant, known ratio of saline water stream, fresh water, first regeneration stream, second regeneration stream, and blowdown stream.

8. A method for treating feedwater for a steam generator, comprising:
a) treating a produced water stream with a warm lime softener treatment unit to make a treated produced water;
b) mixing a saline water, a makeup water and a steam generator blowdown stream in a vessel to form a combined stream;
c) treating said combined stream with a cold limewater stream in a cold lime softener treatment unit, wherein said steam generator blowdown stream increases the operating temperature and pH of said combined stream resulting in less cold limewater being used to make a treated combined stream as compared with cold lime softener treatment units that do not treat blowdown streams;
d) combining said treated produced water with said treated combined stream to form a feedwater for a steam generator.

9. The method of claim 8 , wherein said treating said combined stream with a cold limewater stream in a cold lime softener treatment unit comprises an organic coagulant.

10. The method of claim 9 , wherein said organic coagulant is a poly(diallyldimethylammonium chloride).

11. The method of claim 8 , further comprising the steps of generating steam from said feedwater, injecting said steam into an oil well, producing oil and a condensed steam, separating out said condensed steam to form a produced water, and repeating steps a)-d) for said produced water.

12. An improved water treatment method for SAGD, wherein said water treatment method comprises treating produced water, fresh water, blowdown water, and regeneration water with a warm lime softener treatment unit to produce a first treated water stream, treating saline water with a cold lime softener treatment unit to produce a second treated water stream, generating steam from said first and second treated water streams with at least one steam generator, the improvement comprising feeding said fresh water, said blowdown water, said regeneration water, and said saline water to a vessel and mixing to form a first mixture, and treating said first mixture in said cold lime softener treatment unit, wherein the warm lime softener treatment unit only treats said produced water.

13. The system in claim 12 , wherein said first mixture has a predetermined ratio of fresh, blowdown, regeneration, and saline water, wherein said predetermined ratio is maintained.

14. The system in claim 12 , wherein said improvement further comprises said warm lime softener treatment unit treating larger volumes of produced water than a method wherein a warm lime softener treatment unit treats produced water, fresh water, blowdown water, and regeneration water.

15. A method for treating saline water for SAGD operations, comprising:
a) mixing a saline water stream with a warm steam generator blowdown stream, a warm lime softener regeneration stream, a cold lime softener regeneration stream and a fresh water stream in a vessel at a known and constant ratio to form a mixture;
b) introducing said mixture into a cold lime softener unit, said cold lime softener unit comprising a cold lime softener, a first ion exchanger, and at least one filter in fluid communication, wherein said cold lime softener unit has an outlet for a regeneration stream, an inlet for said mixture, and an inlet for softening chemicals;
c) mixing said mixture with said softening chemicals in said cold lime softener to form a softened mixture, wherein the operation temperature and pH of said cold lime softener is raised by said warm steam generator blowdown stream, wherein said increase in temperature and pH increases the reaction rate of said softening chemicals such that the amount of softening chemicals needed for treatment is reduced;
d) treating the softened mixture with a second ion exchanger and at least one filter to form a treated saline water stream;
e) feeding said treated saline water stream into a steam generator; and
f) wherein said warm steam generator blowdown stream in step a) comes from said steam generator in step e).

16. The method of claim 15 , wherein said cold lime softener regeneration stream comes from said regeneration stream outlet of said a cold lime softener unit.

17. The method of claim 15 , wherein said first ion exchanger and said second ion exchanger each comprises a weak acid cation exchange mechanism.

18. The method of claim 15 , wherein said increase in temperature and pH reduces the amount of cold limewater by 20%.

19. The method of claim 15 , wherein said treated saline water stream is mixed with a treated produced

Assignees

• Conocophillips Co

Inventors

• Kannan Murugavel
• Sharma Ramesh

Classifications

• C02F9/00 Primary

  Multistage treatment of water, waste water or sewage · CPC title

• E21B43/2406

  Steam assisted gravity drainage [SAGD] · CPC title

• C02F1/42

  by ion-exchange (ion-exchange in general B01J) · CPC title

• C02F2001/425

  using cation exchangers · CPC title

• E21B43/2408

  SAGD in combination with other methods · CPC title