PROCESS FOR TREATING PRODUCED WATER FROM AN OIL & GAS FIELD

Abstract

A process of treating a liquid containing oil and solids, includes an ultra- or micro-filtration step followed by a coalescing step of the concentrate obtained from the filtering step by uses of a coalescing contactor.

Claims

1. A process for treating a produced water from an oil and gas field containing oil and solids, said process comprising a first step of obtaining a concentrate by ultra- or micro-filtration (103) of the produced water followed by a second step of coalescing the concentrate obtained from said first step by mean of a coalescing contactor (104) for obtaining at least a deoiled concentrate.

2. The process according to claim 1 wherein said liquid containing oil and solids is selected from at least one of oily water, oil industry waste streams, oil contaminated water or brine, wastewater, contaminated oil, oil containing drainage water, water contaminated with oil, seawater contaminated with oil, brine contaminated with oil, industrial effluents that comprise oil, natural effluents that comprise oil, drilling mud, tailing ponds, leach residue, produced water, oil sands tailing, frac water, connate water, an oil/water/solid mixture, a gravity separated oil/water/solid mixture, water-oil mixtures, aqueous slurries, oil-water mixture from an oil-bearing formation.

3. The process according to claim 1, wherein the first step comprises obtaining a backwash wastewater and wherein the process further comprises a third step of directing said backwash wastewater to the coalescing contactor (104).

4. The process according to claim 1, further comprising before the first step a preliminary step of upstream pretreatment to allow primary separation of the suspended solids and oil (102).

5. The process according to claim 4 further comprising after the second step, a fourth step of recirculating the deoiled concentrate of the second step containing suspended solids from the coalescing contactor (104) back to the preliminary step of upstream pretreatment to allow separation of the suspended solids (102).

6. The process according to claim 3, further comprising after the third step, a fifth step of recirculating the concentrate and/or backwash wastewater of the third step containing suspended solids from the coalescing contactor (104) back to the preliminary step of upstream pretreatment to allow separation of the suspended solids (102).

7. The process according to claim 1, wherein the liquid containing oil and solids is oil-water mixture from an oil-bearing formation and wherein the process further comprises a sixth step selected from: injecting the permeate of the ultrafiltration or microfiltration membrane free of suspended solids and oil back in the oil bearing formation (105), directing the permeate of the ultrafiltration or microfiltration membrane free of suspended solids and oil to a polishing step (106) before injection in the oil bearing formation (105) and directing the permeate of the ultrafiltration or microfiltration membrane free of suspended solids and oil to a polishing step (106) before discharging it to a surface water body (107).

8. The process according to claim 7 wherein the polishing step (106) is selected from a nanofiltration step, a reverse osmosis step, a forward osmosis step, a precipitation step, evaporation/crystallization step, oxidation step, disinfection step or an adsorption step.

9. The process according to claim 2, wherein the first step comprises obtaining a backwash wastewater and wherein the process further comprises a third step of directing said backwash wastewater to the coalescing contactor (104).

10. The process according to claim 2, further comprising before the first step a preliminary step of upstream pretreatment to allow primary separation of the suspended solids and oil (102).

11. The process according to claim 3, further comprising before the first step a preliminary step of upstream pretreatment to allow primary separation of the suspended solids and oil (102).

12. The process according to claim 10, further comprising after the second step, a fourth step of recirculating the deoiled concentrate of the second step containing suspended solids from the coalescing contactor (104) back to the preliminary step of upstream pretreatment to allow separation of the suspended solids (102).

13. The process according to claim 12, further comprising after the second step, a fourth step of recirculating the deoiled concentrate of the second step containing suspended solids from the coalescing contactor (104) back to the preliminary step of upstream pretreatment to allow separation of the suspended solids (102).

14. The process according to claim 4, further comprising after the third step, a fifth step of recirculating the concentrate and/or backwash wastewater of the third step containing suspended solids from the coalescing contactor (104) back to the preliminary step of upstream pretreatment to allow separation of the suspended solids (102).

15. The process according to claim 2, wherein the liquid containing oil and solids is oil-water mixture from an oil-bearing formation and wherein the process further comprises a sixth step selected from: injecting the permeate of the ultrafiltration or microfiltration membrane free of suspended solids and oil back in the oil bearing formation (105), directing the permeate of the ultrafiltration or microfiltration membrane free of suspended solids and oil to a polishing step (106) before injection in the oil bearing formation (105) and directing the permeate of the ultrafiltration or microfiltration membrane free of suspended solids and oil to a polishing step (106) before discharging it to a surface water body (107).

16. The process according to claim 3, wherein the liquid containing oil and solids is oil-water mixture from an oil-bearing formation and wherein the process further comprises a sixth step selected from: injecting the permeate of the ultrafiltration or microfiltration membrane free of suspended solids and oil back in the oil bearing formation (105), directing the permeate of the ultrafiltration or microfiltration membrane free of suspended solids and oil to a polishing step (106) before injection in the oil bearing formation (105) and directing the permeate of the ultrafiltration or microfiltration membrane free of suspended solids and oil to a polishing step (106) before discharging it to a surface water body (107).

17. The process according to claim 4 wherein the liquid containing oil and solids is oil-water mixture from an oil-bearing formation and wherein the process further comprises a sixth step selected from: injecting the permeate of the ultrafiltration or microfiltration membrane free of suspended solids and oil back in the oil bearing formation (105), directing the permeate of the ultrafiltration or microfiltration membrane free of suspended solids and oil to a polishing step (106) before injection in the oil bearing formation (105) and directing the permeate of the ultrafiltration or microfiltration membrane free of suspended solids and oil to a polishing step (106) before discharging it to a surface water body (107).

18. The process according to claim 5, wherein the liquid containing oil and solids is oil-water mixture from an oil-bearing formation and wherein the process further comprises a sixth step selected from: injecting the permeate of the ultrafiltration or microfiltration membrane free of suspended solids and oil back in the oil bearing formation (105), directing the permeate of the ultrafiltration or microfiltration membrane free of suspended solids and oil to a polishing step (106) before injection in the oil bearing formation (105) and directing the permeate of the ultrafiltration or microfiltration membrane free of suspended solids and oil to a polishing step (106) before discharging it to a surface water body (107).

19. The process according to claim 6, wherein the liquid containing oil and solids is oil-water mixture from an oil-bearing formation and wherein the process further comprises a sixth step selected from: injecting the permeate of the ultrafiltration or microfiltration membrane free of suspended solids and oil back in the oil bearing formation (105), directing the permeate of the ultrafiltration or microfiltration membrane free of suspended solids and oil to a polishing step (106) before injection in the oil bearing formation (105) and directing the permeate of the ultrafiltration or microfiltration membrane free of suspended solids and oil to a polishing step (106) before discharging it to a surface water body (107).

20. The process according to claim 19, wherein the polishing step (106) is selected from a nanofiltration step, a reverse osmosis step, a forward osmosis step, a precipitation step, evaporation/crystallization step, oxidation step, disinfection step or an adsorption step.

Description

[0043] In a first embodiment of the invention, the liquid containing oil and solids is selected from at least one of oily water, oil industry waste streams, oil contaminated water or brine, wastewater, contaminated oil, oil containing drainage water, water contaminated with oil, seawater contaminated with oil, brine contaminated with oil, industrial effluents that comprise oil, natural effluents that comprise oil, drilling mud, tailing ponds, leach residue, produced water, oil sands tailing, frac water, connate water, an oil/water/solid mixture, a gravity separated oil/water/solid mixture, water-oil mixtures, aqueous slurries, oil-water mixture from an oil-bearing formation.

[0044] In a second embodiment of the invention, the first step of the process comprises obtaining a backwash wastewater and further comprises a third step of directing said backwash wastewater to the coalescing contactor (104).

[0045] The term backwash wastewater means a wastewater obtained by the membrane backwashing process, i.e. a process pumping water backward through the membrane to remove trapped solid particles.

[0046] In a third embodiment, after the fourth step the oil is recovered as a pure oil stream.

[0047] In another embodiment, the process comprises before the first step an upstream pretreatment to allow primary separation of the suspended solids and oil. The upstream pretreatment would be preferably a step of gravitational separation by using, for example, hydrocyclone or tank for decantation. The upstream pretreatment is not a step of ultra/micro-filtration.

[0048] In another embodiment, the process comprises further after the second step, a fourth step of recirculating the deoiled concentrate and/or backwash wastewater containing suspended solids from the coalescing contactor back to the upstream pretreatment step to allow separation of the suspended solids.

[0049] In another embodiment, the process comprises further after the third step, a fifth step of recirculating the deoiled concentrate and/or backwash wastewater containing suspended solids from the coalescing contactor back to the upstream pretreatment step to allow separation of the suspended solids.

[0050] In yet another embodiment when the liquid containing oil and solids is an oil-water mixture from an oil-bearing formation then the process comprises further a sixth step selected from: [0051] injecting the permeate of the ultrafiltration or microfiltration membrane free of suspended solids and oil back in the oil bearing formation, [0052] directing the permeate of the ultrafiltration or microfiltration membrane free of suspended solids and oil to a polishing step before injection in the oil bearing formation and [0053] directing the permeate of the ultrafiltration or microfiltration membrane free of suspended solids and oil to a polishing step before discharging it to a surface water body.

[0054] According to the invention, the polishing step is well known from the one skilled in the art and may be selected from a nanofiltration step, a reverse osmosis step, a forward osmosis step, a precipitation step, evaporation/crystallization step, oxidation step, disinfection step, or an adsorption step.

[0055] Preferred embodiments of the invention are disclosed in following description and the accompanying drawings which are merely illustrative of such invention.

[0056] It will be understood that particular embodiments described herein are shown by way of illustration and not as limitations of the invention. The principal features of this invention can be employed in various embodiments without departing from the scope of the invention. Those skilled in the art will recognize, or be able to ascertain using no more than routine experimentation, numerous equivalents to the specific procedures described herein. Such equivalents are considered to be within the scope of this invention and are covered by the claims.

[0057] FIG. 1 is a schematic illustration of one embodiment of the process of the present invention. The oil-water mixture from an oil-bearing formation (100) is pumped by the production well (101); the pumping may be realised by all methods of pumping, propelling, or feeding fluid from one location to another employing hoses, lines, tubes ducts, pipes, or pipelines including under pressure. It also includes gravity flow of fluid; said mixture is submitted to a primary oil/water separation step (102) in order to discard parts of the solid particles and the bulk oil; such step may be processed by gravity separation or separated by other methods, e.g., flotation, centrifugation and the like. The collected liquid of step (102) is passed in a first step on an Ultrafiltration or Microfiltration membrane (103); the membrane are either ceramic membrane like silicon carbide (SiC), titanium dioxide (TiO.sub.2), zirconium dioxide (ZrO.sub.2), aluminum oxide (Al.sub.2O.sub.3) or polymeric material like polyacrylonitrile (PAN), polyvinylidene difluoride (PVDF), polytetrafluoroethylene (PTFE), polyethersulfone (PES) and surface modified polymers. The concentrate or the backwash waste water are respectively directed in a second or a third step to the coalescing contactor (104) from which pure oil is recovered whereas the deoiled concentrate and/or backwash wastewater containing suspended solids are returned respectively in a fourth and a fifth step to the primary separation step (102) and treated as described before. The filtrate from the passing through an Ultrafiltration or Microfiltration membrane is returned back through an injection well (105) into the oil-bearing formation (100).

[0058] FIG. 2 is a schematic illustration of a second embodiment of the process of the present invention. The steps are identical to those described in FIG. 1 except that the filtrate from the passing through an Ultrafiltration or Microfiltration membrane is submitted in a sixth step to a polishing treatment (106) before returning back through an injection well (105) into the oil-bearing formation (100). The polishing treatment is processed by any methods, for example oxidation, chemical reduction, pH adjustment, carbon filtering or filtration through sand (calcium carbonate) or fabric filters, disinfection, membrane filtration, thermal treatment, adsorption or combination thereof.

[0059] FIG. 3 is a schematic illustration of a third embodiment of the process of the present invention. The steps are identical to those described in FIG. 2 except that the filtrate from the passing through an Ultrafiltration or Microfiltration membrane submitted to a polishing treatment (106) is discharged to surface water body (107).

[0060] The method according to the invention removes more than 99% of the non-polar oil (ie water insoluble oil) from the feed stream and recovers more than 80% of the non-polar oil (ie water insoluble oil) as pure oil stream from the UF/MF concentrate.

[0061] Moreover the produced water devoid of undesired compounds contained in the produced water such as suspended solids and oil may be used for injection in the oil bearing formation leading to lower operating expenses.