WO2018014096A1

WO2018014096A1 - Hybrid system and method for treating produced water and sea water to be re-injected into a subsea oil reservoir

Info

Publication number: WO2018014096A1
Application number: PCT/BR2017/000076
Authority: WO
Inventors: Giovani CAVALCANTI NUNES; Silvio Edegar WESCHENFELDER; Joyce MONTEIRO SAMBADE
Original assignee: Petróleo Brasileiro S.A. - Petrobras; Universidade Federal Do Rio De Janeiro - Ufrj; PIACSEK BORGES, Crístiano
Priority date: 2016-07-20
Filing date: 2017-07-19
Publication date: 2018-01-25
Also published as: RU2019104644A; CN109963814A; BR102016016758A2; RU2019104644A3; AU2017298020B2; AU2017298020A1; CA3042570A1; CN115925051A; RU2747649C2

Abstract

The present invention relates to systems for treating process water and sea water for secondary recovery in oil wells. In this situation, the present invention provides a hybrid system for treating produced water and sea water to be re-injected into a subsea oil reservoir, comprising (i) at least one inlet for the water to be treated, (ii) at least two treatment modules (20), each module comprising (ii-a) at least one set of micro/ultrafiltration membranes (20a, 20b, 20c) suitable for removing oils and solids from the water being treated, or (ii-b) at least one set of nanofiltration membranes (20a, 20b, 20c) suitable for removing sulphate ions from the water being treated, and (iii) at least one outlet for the treated water. The volume of water to be treated is led to a treatment module (20) comprising micro/ultrafiltration membranes or to a water treatment module comprising nanofiltration membranes, depending on the quality of the water, with regard to the oil and solid content or to the sulphate ion content. The present invention further provides a hybrid water treatment method associated with the above-mentioned system. Thus, the present invention provides a system and method for treating sea water and produced water, allowing the produced water to be re-injected without requiring an additional treatment system on the platform. Other advantages of the present invention include reduced oil discharge into the sea and reduced mounting, operation and maintenance costs, in comparison with an additional system on the sea installation.

Description

"HYBRID PROCESSED WATER AND SEA WATER TREATMENT SYSTEM AND PROCESS FOR REINJECTION IN SUBMARINE OIL RESERVOIR"

FIELD OF INVENTION

[0001] The present invention relates to water treatment systems in offshore oil production facilities. More specifically, the present invention relates to production water treatment and seawater treatment systems for secondary recovery in oil wells.

BACKGROUND OF THE INVENTION

It is well known that in offshore oil production facilities

(offshore), one of the techniques employed in secondary oil recovery is the injection of treated seawater. In this context, seawater is known to contain significant amounts of sulphate tones (SO ₄ ^-2 ), around 2800 mg / L. When seawater is injected into fields whose formation water (conata water) contains sufficient amount of Barium (Ba ⁺² ), Strontium (Sr ⁺² ) or Calcium (Ca ²⁺ ) ions in solution, the contact between these two fronts usually precipitate their sulfates: Barium Sulphate (BaSO ₄ ), Strontium Sulphate (SrSO ₄ ) or Calcium Sulphate (CaSO ₄ ). These salts are extremely insoluble and cause damage to formation due to clogging of the pores with the precipitated salts. They may also precipitate on the production lines and equipment of the process plant.

Depending on the levels of barium and strontium in the formation water, it may be necessary to deploy a sulfate removal unit (URS) for seawater treatment for injection into the reservoir as shown in Figure 1. In URS Nanofiltration membranes (either ceramic or polymer type) are used to remove sulfate ions from seawater. Due to the fact that seawater has solid particles as well as components of marine flora and fauna, it is necessary to install filters upstream of the URS unit to improve its performance. The filtration is initially done with coarse filter and later smaller filter cartridges.

In URS, water permeates through nanofiltration membranes while a fraction, typically 25%, is concentrated in sulfate ions and is separated for later disposal at sea. To achieve the design specification of sulfate ions in treated water, two parallel membrane assemblies are used followed by a third series in series, as shown in the schematic shown in Figure 2.

Once translated by URS, the water acquires the required specification and can now be injected into the secondary recovery oil reservoir.

In addition, it is further known that the water produced arriving at the treatment unit is treated to remove oil droplets. Conventional techniques for this type of treatment have, in general and simplified, the configuration shown in Figure 1.

In particular, the water produced undergoes a treatment process for separation of the aqueous phase from the oil phase consisting of gravitational separation, hydrocyclones and floaters, and is then specified for disposal at sea in accordance with current Environmental Legislation. Water that is not specified for disposal on some platforms has the possibility of being directed to a tank called "Ofispec Tank", where it will have a longer time for separation of the oil phase, and in some cases may be reprocessed in the treatment plant.

These water treatment equipment, however, have a reduced efficiency in removing solids particles and oil droplets below 5.0μm. Such conditions limit the overall efficiency of the treatment and, consequently, the obtaining of an effluent stream with characteristics suitable for reinjection in more restrictive reservoirs in terms of suspended solids, oils and greases content. Therefore, after treatment, the water produced is specified for disposal at sea and is not specified for reinjection due to its content of suspended solids, oils and greases.

Thus, at present, the destination of water produced in offshore oil production facilities after treatment is only disposal. The low efficiency of conventionally produced water treatment plants employed to obtain solids and oil contents according to the requirements for reinjection in the most restrictive reservoirs contributes, among other factors, to the unfeasibility of reinjection. Thus, in recent projects for secondary recovery this alternative is still disregarded. It should be noted, however, that the development of a treatment system that allows the reinjection of the produced water is a very interesting option for the oil industry mainly due to the tendency of environmental legislation to take more and more as well as moving towards increasing the sustainability of industrial practices in this area.

In this sense, micro / ultra filtration membrane separation technologies (with ceramic membranes) have been shown as an interesting option for this challenge, since when applied to the treatment of produced water, it results in low water content. of oil and solids.

In the micro / ultra filtration membrane separation process, as known in the prior art, water permeates the membranes while a fraction of the feed volume accumulates the non-permeate oil and returns to the system as a recycle.

[0013] The document entitled "Ceram / c Ultra- and Nanofiitration

Membranes for Oilfield Produced Water Treatment: Mini Revievf, authored by Ashaghi, K. Shams et al., Reveals a review study regarding the use of ceramic micro / ultra filtration membranes to treat produced water (solids and particle removal). of Oil). Several techniques using ceramic micro / ultra filtration membranes are presented in this scientific paper, so that their description is incorporated herein by reference.

Weschenfelder, Silvio E. et al, one of the inventors of the present invention, discloses a study evaluating the performance of membranes for the treatment of water from the oil extraction process. membranes for the treatment of water produced by long-term tests with real effluent, taking into account the evolution of permeate flow and the characteristics of the generated effluent. The results indicate that by using 0.1 mm pore size membranes it is possible to obtain a permeate stream with solids content of less than 1 mg L ^"1 and oil and grease contents in the range of 1 to 3. mg L ^'1. Still, this document indicates that with the chemical regeneration process the re - establishment of 95% of the original membrane permeability micro / ultra filtration ceramics is possible. the description of this This document is also incorporated herein by reference.

In a current approach, if it were decided to apply the micro / ultra filtration membrane separation process to complement the conventional treatment of the water produced for repositioning viability, for example, an additional system would be required in the treatment plant, such as As described in the aforementioned prior art documents, this brings significantly higher deployment, operation and maintenance costs and greater operational difficulty, as well as greater weight and footprint.

Thus, it is clear that the state of the art lacks a produced water treatment system that allows for reinjection without the need for an additional treatment system as known in the state of the art.

As will be further detailed below, the present invention aims at solving the above-described problems of the art in a practical, efficient and low cost manner.

SUMMARY OF THE INVENTION

The main object of the present invention is to provide a production and hybrid seawater treatment and production system and process which allows the reinjection of produced water without the need for an additional platform treatment system.

In order to achieve the above described objective, the present invention provides a hybrid system of treatment of produced water and seawater for reinjection into subsea oil reservoir, comprising (i) at least one water inlet to be treated, (ii) at least two water treatment modules, each module comprising (ii-a) at least one set of micro / ultra filtration membranes adapted to remove oils and solids from the water to be treated or (ii-b) by at least one set of nanofiltration membranes adapted to remove sulfate ions from the water to be treated, and (iii) at least one treated water outlet, wherein the volume of water to be treated is directed to a water treatment module comprising micro / ultra filtration membranes or for a water treatment module comprising nanofiltration membranes depending on water quality with respect to oil and solid content or sulfate ions content The.

[0020] The present invention further provides a hybrid process of treating produced water and seawater for reservoir reinjection. subsea petroleum, basically comprising the steps of (i) directing the water to be treated to a water treatment module comprising at least one set of micro / ultrafiltration membranes adapted to remove oils and solids from the water to be treated or ( ii) directing the water to be treated to a water treatment module comprising at least one set of nanofiltration membranes adapted to remove sulfate ions from the water to be treated, wherein the volume of water to be treated is directed to the module. water treatment modules comprising micro / ultra filtration membranes or for the water treatment module comprising nanofiltration membranes depending on the water quality with respect to oil and solids content or sulfate ions content.

BRIEF DESCRIPTION OF THE FIGURES

The detailed description given below refers to the accompanying figures and their respective reference numerals.

Figure 1 illustrates a schematic diagram of a seawater treatment system and water produced for injection and disposal, respectively, as known at the prior art.

Figure 2 illustrates a schematic diagram of an example of seawater treatment for injection into an oil reservoir via a sulphate removal unit (URS) as known in the prior art.

Figure 3 illustrates a schematic diagram of a treatment module comprising nanofiltration or microfiltration membranes in accordance with the preferred embodiment of the present invention.

Figure 4 illustrates a schematic diagram of one of a hybrid seawater and reinjection produced water treatment system according to the preferred embodiment of the present invention.

Figure 5 illustrates a schematic diagram of a complete seawater and reinjection produced water treatment system comprising the hybrid system of the present invention.

DETAILED DESCRIPTION OF THE INVENTION

First of all, it is emphasized that the following description will start from a preferred embodiment of the invention. As will be apparent to any person skilled in the art, however, the invention is not limited to that particular embodiment.

Figure 4 illustrates a simplified schematic diagram of one of a hybrid seawater treatment system and water produced for subsequent reinjection in accordance with the preferred embodiment of the present invention. This figure basically contemplates two water inlets to be treated, namely, one produced water 2, with high levels of oils and solids, and one seawater 4, with high content of sulfate ions.

The water produced is preferably stored in at least one tank 10 before being directed for disposal or treatment through the hybrid system of the present invention.

Preferably, seawater captured for treatment and further injection is passed through a sequence of filters, the former having thicker meshed filter elements and the latter having finer meshed filtering elements. Preferably, a first filter 12 retains particles up to 500 μm, a second 14 retains particles up to 25 μm and a third filter up to 5 μm.

Preferably, both the produced water and the captured seawater respectively arrive in at least one manifold 18 consisting of a plurality of water control valves that will enter each of the treatment modules 20.

Each treatment module 20 comprises at least one set of micro / ultra filtration membranes (ceramic membranes) adapted to remove oils and solids from the produced water or at least one set of nanofiltration membranes (ceramic or polymeric membranes). for removal of sulfate ions from seawater. Thus, the at least one manifold 18, through its control valves, directs the water produced to the modules comprising micro / ultrafiltration membranes and the seawater captured to the modules comprising nanofiltration membranes. Preferably, the at least one manifold is subdivided into two manifolds, one for controlling the ingress of water produced in the modules comprising microfiltration membranes and the other for controlling the ingress of seawater into the modules comprising nanofiltration membranes.

Preferably, the at least one manifold 18 is fluidly connected to the two water inlet ducts to be treated, namely one for water produced 2 and one for seawater 4. Each of these inlet ducts separately is subdivided into a plurality of parallel ducts, one secondary duct for each treatment module. Secondary produced water and seawater ducts, prior to entry into each treatment module 20, flow into a single inlet duct per module downstream of each control valve.

Control valves are positioned upstream of each treatment module 20 so that each valve controls the inlet of a type of water to be treated, namely produced water or seawater from each one. of the secondary ducts.

Preferably, there is no mixing between produced water and seawater before entering treatment modules 20. That is, if the produced water inlet control valve is open, the seawater inlet control valve it should preferably be closed.

Preferably, each treatment module 20 comprises only one type of membrane, namely nanofiitration or micro / ultra filtration. Thus, preferably, if a particular treatment module 20 comprises only nanofiitration membranes, only seawater will be directed to it, the produced water inlet control valve being closed. Likewise, the water produced will be directed to a treatment module 20 comprising only micro / ultra filtration membranes.

Each treatment module 20 is designed to allow interchangeability between nanofiitration and micro / ultra filtration membranes. In other words, each module can have its nanofiitration membranes replaced with micro / ultra filtration (and vice versa) depending on the treatment demand of each water.

By way of example, it is to be expected that soon after the implementation of the hybrid system of the present invention there is only demand for seawater treatment through nanofiitration membranes, as no water will be produced yet. Thus, virtually all treatment modules 20 may be equipped with nanofiitration membranes only. As produced water is generated, the demand for seawater treatment decreases. In this case, the nanofiitration membranes of the treatment modules 20 will being replaced by micro / ultra filtration membranes.

Figure 3 illustrates in a schematic diagram details of a treatment module 20 in accordance with the present invention. As mentioned, the treatment module 20 may comprise nanofit or microfiltration membranes depending on the type of water (produced or sea) that will pass through that particular module. Each module comprises at least one set of microfiltration or nanofiltration membranes. Preferably, like the prior art URS, each module comprises two parallel membrane assemblies 20a, 20b followed by a third series membrane array 20c.

Preferably, in the case of a treatment module 20 provided with nanofiitration membranes, for removal of sulfate ions from seawater, the water to be treated passes through the first two sets of nanofiitration membranes in parallel, so that The largest fraction of the volume of treated water comprises a low concentration of sulfate ions and is sent for injection into the reservoir.

The remainder of the water that passes through the first set of membranes, concentrated in sulfate ions, is directed to the third set of membranes 20c in series with the first two. This third set treats this more concentrated water and also generates a larger portion with low sulfate ion concentration, which will be mixed with water treated by the first two membrane sets, and a smaller extremely concentrated sulfate ion portion that is normally discarded in the sea.

Water with low sulfate ion concentration from the treatment of nanofiitration membrane assemblies is used for injection into the reservoir and may instead undergo additional treatment steps.

In the case of a treatment module 20 having micro / ultra filtration membranes for removing oils and solids from the produced water, the procedure is quite similar to the previous one. Preferably, the water to be treated passes through the first two sets of membranes 20a, 20b in parallel, so that the largest fraction of the volume of treated water comprises low concentration of oils and solids and is directed for rejection in the reservoir.

The remainder of the water that passes through the first sets of membranes, concentrated in oils and solids, is deactivated for the third set of membranes 20c in series with the first two. This third set performs the treatment of this more concentrated water and also generates a larger portion with low concentration of oils and solids, which will be mixed with water treated by the first two sets of membranes. Water with low concentration in oils and solids from treatment of all three micro / ultra filtration membrane assemblies is used for reinjection into the reservoir.

Depending on the quality of the water to be treated, each treatment module 20 may comprise more or less series of and / or parallel membrane assemblies. Thus, it is noted that the present invention is not limited to the membrane assembly configuration illustrated in Figure 3.

Still in the case of a treatment module 20 provided with micro / ultra filtration membranes, the smaller portion from the third set of membranes 20c, concentrated in oils and solids, may be directed to the inlet of the treatment module 20 as shown. illustrated in figure 3.

Alternatively, as illustrated in Figure 5 (complete diagram of marine installation), water concentrated in oils and solids (oily recycle) can be routed to the water phase separation water treatment system. Preferably, the water concentrated in oils and solids may be directed to some treatment tank, shown schematically in Figure 5 (treatment tank 24). This tank can be, for example, an off spec tank that is normally already used in produced water treatment plants. Alternatively, an additional tank may be provided for performing this step in addition to the off spec tank.

Optionally, at least one water outlet is provided in the lower portion of the low oil concentration water treatment tank 24, since the oil, less dense than water, after a certain period will become concentrated. on top. Water drawn through the water outlet in the lower portion of the treatment tank 24, which has a relatively low or medium concentration in oils, may be disposed of if specified or directed to the hybrid treatment system according to present invention where it will be directed to treatment modules 20 comprising micro / ultra filtration membranes to undergo a new oil and solids removal treatment. The remaining oily concentrate in the treatment tank 24, after part of the water has been removed, is preferably directed to the oil and water separation system 23 for use in production oil. This contributes to minimizing the disposal of oil at sea and to a better use of oil present in the water produced in the total well production.

The present invention further provides for the possibility of performing a backwashing procedure of the membranes used in the treatment modules, especially the micro / ultra filtration membranes. Such a procedure may be performed, for example, by pumps (not shown) or manipulation of timed valves in the treated water line and the supply line of each assembly. This procedure allows periodic inversion of the membrane flow, cleaning it and maintaining its performance.

Optionally at least one first deaerator unit

28 is provided upstream or downstream of the seawater deaeration treatment modules 20 if necessary prior to reinjection into the reservoir.

The present invention further provides a hybrid process of treating produced water and seawater for reinjection into the subsea reservoir, comprising basically the steps of:

(a) directing the water to be treated to a water treatment module comprising at least one set of micro / ultra filtration membranes adapted to remove oils and solids from the water to be treated; or b) directing the water to be treated to a water treatment module comprising at least one set of nanofiitration membranes adapted to remove sulfate ions from the water to be treated, wherein the volume of water to be treated is directed to the water. water treatment module comprising micro / ultra filtration membranes or for water treatment module comprising nanofiitration membranes depending on water quality with respect to oil and solids content or sulfate ion content.

It is further emphasized that all treatment steps described in this detailed description apply to both the system and the process of the present invention.

Accordingly, based on the above description, the present invention provides a production and seawater treatment system and process that allows the reinjection of produced water without the need for an additional treatment system on the platform. Still further advantages are achieved through the present invention, such as the reduction of oil discharge at sea by the more efficient treatment of the water produced and the reduction of installation, operation and maintenance costs associated with an additional system in the marine installation.

Numerous variations affecting the scope of protection of this application are permitted. Accordingly, it is emphasized that the present invention is not limited to the particular embodiments / embodiments described above.

Claims

1. Hybrid produced water and seawater treatment system for reinjection into a subsea oil reservoir, comprising:

at least one water inlet to be treated;

at least two treatment modules (20), each module

comprising:

at least one set of micro / ultra filtration membranes (20a, 20b, 20c) adapted to remove oils and solids from the water to be treated; or at least one set of nanofiltration membranes (20a, 20b, 20c) adapted to remove sulfate ions from the water to be treated; and

at least one treated water outlet, wherein the volume of water to be treated is directed to a treatment module (20) comprising micro / ultra filtration membranes or to a water treatment module comprising nanofiltration membranes depending on the quality of the water. water with respect to oil and solid content or sulfate ion content.

System according to Claim 1, characterized in that each of the treatment modules (20) comprises at least two membrane assemblies (20a, 20b) in parallel.

System according to Claim 1 or 2, characterized in that each of the treatment modules (20) comprises at least one membrane assembly (20c) in series with the other membrane assemblies (20a, 20b).

System according to any one of Claims 1 to 3, characterized in that at least one water inlet to be treated is two water inlets, namely one produced water (2) and one seawater inlet. (4).

System according to claim 4, characterized in that it further comprises at least one manifold (18), provided with a plurality of valves, adapted for controlling the type of water that will enter each of the water treatment modules (20). ), namely produced water or seawater.

System according to claim 5, characterized in that each of the inlet ducts (2, 4) is separately subdivided into a plurality of secondary ducts in parallel, a secondary duct for each treatment module (20).

System according to any one of claims 1 to 6, characterized in that each treatment module (20) comprises only one type of membrane; namely nanofiltration or micro / ultra filtration.

System according to any one of claims 1 to 7, characterized in that the membranes of each treatment module (20) are interchangeable with another membrane type.

A system according to any one of claims 1 to 7, further comprising at least one water treatment tank (24) adapted for separating the aqueous phase from the oil phase by density difference.

System according to Claim 9, characterized in that the water treatment tank (24) is in fluid communication with the at least two downstream and upstream treatment modules (20), enclosing a cycle.

System according to Claim 9 or 10, characterized in that the water treatment tank (24) is additionally in fluid communication with at least one outlet for disposal at sea and a water inlet duct produced for separation between water. this is Leo.

12. Hybrid process of treatment of produced water and seawater for reinjection into a subsea oil reservoir, characterized by comprising the step of:

directing the water to be treated to at least one water treatment module (20) comprising at least one set of micro / ultra filtration membranes adapted to remove oils and solids from the water to be treated; or

directing the water to be treated to at least one treatment module (20) comprising at least one set of nanofiltration membranes adapted to remove sulfate ions from the water to be treated,

wherein the volume of water to be treated is directed to the at least one treatment module (20) comprising micro / ultrafiltration membranes or to at least one water treatment module comprising nanofiltration membranes depending on the type of water to be treated. be treated, namely produced water or seawater.

Process according to claim 12, characterized in that the step of directing the water to be treated to a treatment module (20) further comprises treating the water by at least two sets of water. membranes (20a, 20b) in parallel.

Process according to Claim 12 or 13, characterized in that the step of directing the water to be treated to a treatment module (20) further comprises treating the water through at least one membrane assembly (20c) in series. with the other membrane assemblies (20a, 20b).

Process according to any one of claims 12 to 14, characterized in that the water to be treated is water produced, concentrated in oils and solids, and seawater concentrated in sulfate ions.

A method according to claim 15, further comprising the step of controlling the type of water that will enter each of the treatment modules (20), namely produced water or seawater, by at least a manifold (18) provided with a plurality of valves.

Process according to any one of Claims 12 to 16, characterized in that it further comprises the step of directing a fraction of water concentrated in oils and solids from the breast minus a treatment module (20) comprising at least one set of membranes. micro / ultra filtration for at least one treatment tank (24).

Process according to Claim 17, characterized in that it further comprises the step of separating, by difference in density over a given period, the less dense oil phase from the denser aqueous phase within the treatment tank (24).

The method of claim 18 further comprising a step of removing the separated aqueous phase through at least one water outlet provided in the lower portion of the treatment tank (24).

A method according to claim 19 further comprising a step of directing the withdrawn aqueous phase for disposal at sea or for at least one treatment module (20).

Process according to any one of claims 18 to 20, characterized in that it further comprises a step of directing the remaining oily concentrate in the treatment tank (24), after the removal phase of the aqueous phase, to the separation system ( 23) water and oil.

Process according to any one of claims 14 to 24, characterized in that it further comprises at least one step of deaeration of the treated water through at least one deaerator unit (28).

A method according to any one of claims 12 to 22, further comprising at least one backwashing step of the membranes of at least one treatment module (20) by reversing the flow of water therein.