Method of recovering oil or gas and treating the resulting produced water

Patent metadata

Field	Value
Publication number	US-10023487-B2
Application number	US-201213443971-A
Country	US
Kind code	B2
Filing date	Apr 11, 2012
Priority date	Dec 12, 2006
Publication date	Jul 17, 2018
Grant date	Jul 17, 2018

Abstract

A method or process for treating wastewater containing high organics, silica, boron, hardness, and suspended and dissolved solids. The method includes degasifying the wastewater for the removal of dissolved gases and thereafter chemically softening the wastewater. After the chemical softening step, the wastewater is directed through a media filter or membrane which removes additional solids and precipitants. Thereafter the wastewater is directed through a sodium ion exchange that further softens the wastewater. The effluent from the ion exchange is directed through a cartridge filter and the effluent from the cartridge filter is directed through one or more reverse osmosis units. At a selected phase of the process, prior to the wastewater reaching the reverse osmosis unit or units, the pH of the wastewater is raised and maintained such that the pH of the wastewater reaching a reverse osmosis unit is at a pH greater than 10.5.

First claim

The invention claimed is:

1. A method of recovering oil or gas from an oil or gas well and treating resulting produced water, comprising:
a. recovering an oil/water or gas/water mixture from the oil or gas well;
b. separating oil from the oil/water mixture or separating gas from the gas/water mixture to produce an oil or gas product and the produced water, and wherein the produced water includes organics, silica, hardness, dissolved solids and suspended solids;
c. reducing hardness in the produced water by chemically softening the produced water in a chemical softening unit which results in the formation of hardness precipitants;
d. raising the pH of the produced water to 10.5 and above;
e. directing the produced water having said pH of 10.5 and above to a mixing tank forming a part of the chemical softening unit and mixing the produced water in said mixing tank and causing crystallization of the precipitants within the produced water;
f. after crystallization, removing free oil and crystals from the produced water by directing the produced water through a membrane filter and producing a membrane effluent and a membrane reject stream containing free oil and the crystals;
g. recirculating at least a portion of the membrane reject stream to the chemical softening unit and causing the crystals in reject stream to grow larger;
h. directing the membrane effluent to an ion exchange unit and further softening the membrane effluent by removing residual calcium and magnesium hardness therefrom and producing an ion exchange effluent and a waste stream;
i. after further softening the membrane effluent, directing the ion exchange effluent to at least one reverse osmosis unit and removing dissolved solids from the ion exchange effluent and producing a reject stream and a permeate stream which contain ammonium hydroxide (NH 4 OH);
j. reducing the concentration of ammonium hydroxide in the reverse osmosis permeate stream by directing the reverse osmosis permeate stream through an ammonia polisher located downstream from the reverse osmosis unit;
k. regenerating the ammonia polisher by adding an acid solution to the ammonia polisher which generates a waste stream produced by the ammonia polisher;
l. directing at least a portion of the waste stream produced by the ammonia polisher to the chemical softening unit and subjecting the waste stream from the ammonia polisher to treatment in the chemical softening unit;
m. wherein the ammonia polisher produces a treated effluent;
n. mixing hydrogen peroxide (H 2 O 2 ) with the treated effluent from the ammonia polisher;
o. after mixing hydrogen peroxide with the treated effluent, subjecting the ammonia polisher effluent to irradiation and converting the hydrogen peroxide in the treated effluent into hydroxyl radicals (HO.);
p. employing the hydroxyl radicals to oxidize organic content contained in the treated effluent from the ammonia polisher; and
q. after irradiating the treated effluent from the ammonia polisher, mixing sodium bisulfite with the treated effluent from the ammonia polisher to remove residual hydrogen peroxide.

2. The method of claim 1 wherein the produced water includes free oil and wherein the method includes, prior to removing hardness, directing the produced water to a treatment unit disposed upstream of the chemical softening unit for removing free oil and reducing turbidity and the concentration of organics in the produced water and including:
mixing an acid and a coagulant with the produced water;
after mixing the acid and the coagulant with the produced water, directing the produced water to a gas flotation chamber;
mixing a polymer with the produced water in the gas flotation chamber;
directing a gas through the produced water in the flotation chamber wherein gas bubbles associated with the gas to facilitate the removal of the free oil and insoluble organic particulates in the produced water as the gas bubbles rise to the top of the produced water in the gas flotation chamber and the method includes skimming the gas bubbles from the produced water; and
directing the produced water from the gas flotation chamber and directing at least a portion of the produced water to the chemical softening unit and recycling another portion of the produced water from the gas flotation chamber back to the gas flotation chamber.

Assignees

• Nagghappan Lnsp
• Korpiel John A
• Veolia Water Solutions & Tech

Inventors

• Nagghappan Lnsp
• Korpiel John A

Classifications

• C02F1/444

  by ultrafiltration or microfiltration · CPC title

• C02F2103/365

  from petrochemical industry (e.g. refineries) · CPC title

• C02F1/68

  by addition of specified substances, e.g. trace elements, for ameliorating potable water (medicinal water A61K) · CPC title

• C02F1/40

  Devices for separating or removing fatty or oily substances or similar floating material (cleaning or keeping clear the surface of open water from oil or like materials E02B15/04; devices in sewers for separating liquid or solid substances from sewage E03F5/14, e.g. for use in drains leading to the sewer E03F5/16) · CPC title

• C02F1/42

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