Method for separating fluids
Methods of treatment of fluids produced by an oil or gas well following a stimulation operation, allowing separation from the fluids and re-injection of oil and gas hydrocarbons in a production pipeline under pressure, and allowing achievement of suitable quality for the residual fluids compatible with their rejection, for example into the sea, including the following three elements; neutralization of the fluids by mixing with a high pH chemical, until the resulting pH reaches a level compatible with the equipment and pipes; use of optimized emulsion breakers in a phase separator, selected for best results with the fluids produced by the well, to accelerate the separation of oil from the fluids, and to lower the residual oil content in the fluids to levels compatible with environmental regulations; and use of a multi-phase pump to pump the oil and gas hydrocarbons produced and reinject them in a pipeline under pressure.
1. A method of separating multiphase fluids produced from a well, comprising:
(i) feeding the multiphase fluids to a separator so as to form separate water and hydrocarbon phases wherein the hydrocarbon phase comprises an oil phase;
(ii) passing the water phase to a skimmer in which any oil contained in the water phase is allowed to separate further;
(iii) passing the oil phase to a surge tank in which any water contained in the oil is allowed to separate further;
(iv) passing separated oil from the skimmer to the surge tank;
(v) passing separated water from the surge tank to the skimmer;
(vi) injecting oil from the surge tank into a production pipeline; and
(vii) discharging water from the skimmer.
2. A method as claimed in claim 1 , wherein injection of the oil into the production pipeline takes place via a multiphase pump.
3. A method as claimed in claim 1 wherein the hydrocarbon phase comprises a gas phase and an oil phase the method further comprising the steps of
separating the oil and gas phases; and
(ii) injecting the oil phase into the production pipeline.
4. A method as claimed in claim 3 further comprising burning the gas phase.
5. A method as claimed in claim 3 , comprising injecting the gas and oil phases into the production pipeline.
6. A method as claimed in claim 1 , further comprising treating the water phase to further reduce its oil content in the water phase.
7. A method as claimed in claim 6 , comprising reducing the oil content in the water phase to less than 80 ppm.
8. A method as claimed in claim 6 , further comprising using selected chemicals to accelerate breaking of emulsions.
9. A method as claimed in claim 8 , wherein the chemicals comprise surfactants including methanol-based cationic and anionic surface active agents, naphtha-based non-ionic surfactants, water-based surfactants, dodecylbenzene sulfonic acid-based non-ionic surfactants, propan-2-ol based surfactants, or blends thereof.
10. A method as claimed in claim 9 , wherein the methanol-based cationic and anionic surface active agents comprise:
quaternary amine compounds
15+14 40%
methanol
30+14 60%
aromatic alcohol glycol ether
+11 7+14 13%
propan-2-ol
+12 3+14 7%.
11. A method as claimed in claim 9 , wherein the naphtha-based non-ionic surfactants comprise:
naphthalene
+11 5+14 10%
poly(oxy-1,2-ethanediyl)-nonylphenyl-hydroxy
1+14 5%
heavy aromatic naphtha
+11 +12 60+14 100%.
12. A method as claimed in claim 9 , wherein the water based surfactants comprise:
propan-2-ol
30+14 60%
aliphatic alcohol glycol ether
10+14 30%
methanol
5%
water
30+14 60%
oxyalkylated alkanols
+11 0+14 20%
quaternary amine iodide derivatives
0+14 1%
quaternary amine chloride derivatives
0.1+14 1%.+11 +12
13. A method as claimed in claim 9 , wherein the dodecylbenzene sulfonic acid-based non-ionic surfactants comprise:
dodecylbenzene sulfonic acid
54%+12
poly(oxy-1,2-ethanediyl)-nonylphenyl-hydroxy
10+14 30%
methanol
24%.
14. A method as claimed in claim 9 , wherein the dodecylbenzene sulfonic acid-based non-ionic surfactants comprise:
dodecylbenzene sulfonic acid
+12 +12 +12 30+14 60%%
propan-2-ol
10+14 30%
glycol
3+14 7%
water
1+14 5%
1 st glycol-ether
+11 7+14 13%
2 nd glycol-ether
+12 10+14 30%.
15. A method as claimed in claim 9 , wherein the propan-2-ol based surfactant comprises:
propan-2-ol
15+14 40%+11
aromatic hydrocarbon
5+14 10%
oxyalkylated polyol
10+14 30%+11
alkyl ether phosphate ester
5+14 10%
1 st oxyalkylated alkanols
5+14 10%
2 nd oxyalkylated alkanols
5+14 10%
resin
7+14 13%
water
+12 7+14 13%.
16. A method as claimed in claim 9 , wherein the water-based surfactants comprise:
1 st polyglycol ether
15+14 25%
2 nd polyglycol ether
10+14 30%
propan-2-ol
15+14 25%
2-butoxyethanol
17+14 25%
water
+12 10+14 30%.
17. A method as claimed in claim 9 , wherein the surfactant blend comprises:
methanol-based cationic and anionic surface active agents
40%
naphtha-based non-ionic surfactants
30%
water-based surfactants
+12 30%.
18. A method as claimed in claim 9 , wherein the surfactant blend comprises:
naphtha-based non-ionic surfactants
30%
dodecylbenzene sulfonic acid-based non-ionic surfactants
30%
water-based surfactants
+12 20%.
19. A method as claimed in claim 1 , further comprising treating the multiphase fluids produced from the well.
20. A method as claimed in claim 19 , wherein the step of treating the multiphase fluids comprise neutralizing any acid in the fluids.
21. A method as claimed in claim 20 , comprising neutralizing acid using a solution of Na 2 CO 3 .
22. A method as claimed in claim 21 , wherein the solution is injected into the fluids prior to their passing to a separator.
23. A method as claimed in claim 22 , comprising raising the pH of the fluids to at least 5.5 prior to injection into the separator.