CA2769064C - Method of recovering oil from extra heavy oil layer - Google Patents

Abstract

The invention is a method of recovering oil from an extra heavy oil layer, including the steps of purifying and reusing high-temperature water separated from a mixture of oil and the high-temperature water, a method of recovering oil from an extra heavy oil layer, including separating and recovering oil and high-temperature water from a mixture of the oil and the high-temperature water, which is obtained by injecting high-temperature steam into the extra heavy oil layer, and then reusing the high-temperature water to generate the high-temperature steam, the method including the step of subjecting raw water, which is obtained by cooling the high-temperature water to a temperature of 60 to 90°C, to ultrafiltration by feeding the raw water to an ultrafiltration membrane equipment, thereby providing permeated water with a reduced content of a water-soluble organic substance, in which the ultrafiltration membrane equipment used in the ultrafiltration step includes an ultrafiltration membrane module filled with a hollow fiber membrane which is made of a heat-resistant resin and has a molecular weight cut-off of 8,000 to 30,000.

Description

.* CA 02769064 2012-02-24 Description Method of recovering oil from extra heavy oil layer Technical Field [0001]
The present invention relates to a method of recovering extra heavy oil from Canadian oil sands or a Venezuelan extra heavy oil layer (hereinafter, referred to as "extra heavy oil layer") by employing a steam assisted gravity drainage (SAGD) method.
Background Arts

[0002]
In recovering extra heavy oil from an extra heavy oil layer, an SAGD method including injecting steam into the extra heavy oil layer to recover the extra heavy oil as a mixture of oil and water has been put into practical use in Canada. More specifically, the following recovery process is conducted.

[0003]
The extra heavy oil contained in the extra heavy oil layer is present as high-viscosity oil which does not flow at normal temperature. Therefore, high-temperature steam is injected under pressure for heating so as to reduce the viscosity of the oil. In this manner, a mixture of high-temperature water, which is formed by condensation of the steam, and oil is recovered.
The mixture is separated into the oil and the high-temperature water in a facility located on the ground.

[0004]
The oil obtained by the separation is shipped as a product, whereas the high-temperature water is heated again in a boiler and converted to steam to be reused in the SAGD method. At this time, the high-temperature water contains silica, a hardness component such as a calcium salt and a magnesium salt, metal ions, and a water-soluble organic substance mainly containing a humic substance, which are eluted from the extra heavy oil layer, and the like. Therefore, when the high-temperature water is to be reused in the SAGD method, those substances are required to be removed.

[0005]
Patent Document 1 discloses a method of treating an organic substance, including adsorbing the organic substance to an adsorbent and desorbing the organic substance from the adsorbent by electrolysis. Activated carbon and zeolite are described as examples of the adsorbent (Examples 1 and 2, paragraphs 0082 and 0083) .
Patent Document 2 discloses an invention in which bitumen is extracted from a bitumen-mixed fluid recovered from the ground and heated oil-containing water separated from the mixed fluid is treated with a microfiltration membrane (MF membrane) made of polytetrafluoroethylene when bitumen is produced from oil sands. In paragraph 0028, it is described that a UF membrane, an RO membrane, and an NF membrane are not preferred.
Patent Documents 3 and 4 each disclose a method of treating heated oil-containing water, similar to that disclosed in Patent Document 2. FIG. 1 illustrates a flow diagram including subjecting high-temperature water with an anionic flocculant or a cationic flocculant treatment to form coagulation solid under an acidic conditionandcooling the acidic high-temperature water to a temperature close to normal temperature, followed by a membrane treatment in which a UFmembrane 1034, an NFmembrane 1036, and an RO membrane 1118 are connected in series.

[0006]
The above cited Patent Document 1 is JP-A2008-279435, Patent Document 2 is JP-A 2010-248431, Patent Document 3 is CA 2673981 Al and Patent Document 4 is CA 2673982 Al.
Summary of the Invention

[0007]
The present invention relates to a method of recovering oil from an extra heavy oil layer, including a process for separating and recovering oil and high-temperature water from a mixture of the oil and the high-temperature water, which is obtained by injecting high-temperature steam into the extra heavy oil layer, and the reusing the high-temperature water to generate the high-temperature steam, the process including subjecting the high-temperature water to a softening treatment and a coarse filtration treatment, followed by ultrafiltration using an ultrafiltration membrane equipment, thereby removing a hardness component, a suspended substance, and a water-soluble organic substance dissolved in the high-temperature water at such a high removal rate that enables the reuse of the high-temperature water.

[0008]
The present invention relates to a method of recovering oil from an extra heavy oil layer, including separating and recovering oil and high-temperature water from a mixture of the oil and the high-temperature water, which is obtained by injecting high-temperature steam into the extra heavy oil layer, and then reusing the high-temperature water to generate the high-temperature steam, the method including the step of subjecting raw water, which is obtained by cooling the high-temperature water to a temperature of 60 to 90 C, to ultrafiltration by feeding the raw water to an ultrafiltration membrane equipment, thereby providing permeated water with a reduced content of a water-soluble organic substance, in which:
the permeated water is reused to generate the high-temperature steam; and the ultrafiltration membrane equipment used in the ultrafiltration step includes an ultrafiltration membrane module filled with a hollow fiber membrane or hollow fiber membranes which are made of a heat-resistant resin and have a molecular weight cut-off of 8,000 to 30,000.

[0009]
The present invention relates to a method of recovering oil from an extra heavy oil layer, including separating and recovering oil and high-temperature water from a mixture of the oil and the high-temperature water, which is obtained by injecting high-temperature steam into the extra heavy oil layer, and then reusing the high-temperature water to generate the high-temperature steam, the method including the steps of:
charging the high-temperature water separated from the mixture of the oil and the high-temperature water into a raw-water tank;subj ecting the high-temperature water in the raw-water tank to a softening treatment by delivering the high-temperature water to a softener;
subjecting the alkaline high-temperature water obtained by the softening treatment in the previous step to a coarse filtration treatment;
subjecting raw water, which is obtained by cooling the high-temperature water to a temperature of 60 to 90 C, to ultrafiltration process, thereby providing ultrafiltration permeated water with a reduced content of a water-soluble organic '65702-562 CA 02769064 2012-02-24 substance; and subjecting the permeated water from which the water-soluble organic substance is removed in the previous step to an ion exchange treatment, in which:
the permeated water obtained by the ion exchange treatment is reused to generate the high-temperature steam; and the ultrafiltration membrane equipment used in the ultrafiltration step includes an ultrafiltration membrane module filled with a hollow fiber membrane or hollow fiber membranes which are made of a heat-resistant resin and have a molecular weight cut-off of 8,000 to 30,000.

[0010]
In other words, the invention relates to a method of recovering oil from an extra heavy oil layer, including injecting high temperature steam into the extra heavy oil layer and separating and recovering oil and high-temperature water from a mixture of the oil and the high-temperature water, further including cooling the high-temperature water to a temperature of 60 to 90 C to obtain raw water, subjecting the raw water to ultrafiltration by feeding the raw water to an ultrafiltration membrane device, thereby providing permeatedwater with a reduced content of a water-soluble organic substance (s) , heating the permeated water to generate the high-temperature steam to reuse the high-temperature water to generate the high-temperature 55'702-562 CA 02769064 2012-02-24 steam, in which the ultrafiltration membrane equipment includes an ultrafiltration membrane module filled with a hollow fiber membrane or hollow fiber membranes which are made of a heat-resistant resin and has a molecular weight cut-off of 8,000 to 30,000.
According to the method of recovering oil from an extra heavy oil layer of the present invention, the ultrafiltration membrane equipment is provided in the recovery step. Therefore, the following effects can be obtained.
(I) By the operation of the ultrafiltration membrane equipment, the permeated water with a lowered concentration of a humic substance can be fed to a boiler. Therefore, the frequency, and cost of maintenance for maintaining a normal operation of the boiler are reduced.
(II) The operating time of the boiler can be increased because the frequency and cost of maintenance for maintaining the normal operation of the boiler are reduced. Therefore, an operating rate of the boiler can be increased.
(III) Concentrated water and back-pressure washing waste water generated by the operation of the ultrafiltration membrane equipment are recycled. Therefore, a recovery rate of water used for recovering the oil from the extra heavy oil layer is improved. Moreover, a supply water amount of river water or well water can be saved.
(IV) Auxiliary equipments for treatments, which are provided downstream of the ultrafiltration membrane equipment, are fed with the permeated water with the concentration of the humic substance lowered by the operation of the ultrafiltration membrane equipment. Therefore, a load on the auxiliary equipment is reduced to further enhance treatment capability.
(V) When the amount of an impurity is further reduced by providing an NF-membrane equipment or an RO-membrane equipment downstream of the ultrafiltration membrane equipment device, a stable membrane treatment operation can be performed because the concentration of the humic substance which causes fouling in the membrane treatments is reduced.
The method of recovering oil from an extra heavy oil layer of the resent invention can be used as a method including injecting steam into the extra heavy oil layer to recover extra heavy oil as a mixture of oil and water when the extra heavy oil is recovered from the extra heavy oil layer.

Brief Description of the Drawings

[0011]
FIG. 1 is a flow diagram for conducting a method of recovering oil from an extra heavy oil layer of the present invention.
FIG. 2 is a flow diagram of another embodiment for conducting the method of recovering oil from an extra heavy oil layer of the present invention.
FIG. 3 is a flow diagram of still another embodiment for conducting the method of recovering oil from an extra heavy oil layer of the present invention.
FIG. 4 is a schematic view of an ultrafiltration membrane equipment in each of the flows illustrated in FIGS. 1 to 3.
FIG. 5 is a diagram illustrating an ultrafiltration method of Example.
FIG. 6 is a graph showing changes with in permeated water amount (flux) when filtration is performed using hollow fiber membranes having molecular weight cut-offs of 10,000 and 30,000 in Example.
FIG. 7 is a graph showing change with time in water flux when filtration is performed using a hollow fiber membrane having a molecular weight cut-off of 150,000 in Comparative Example.
FIG. 8 is a graph showing changes with time in removal rate of a humic substance when filtration is performed using hollow fibermembranes havingmolecular weight cut-offs of 5,000,10,000, 30,000, and 150,000 in Example and Comparative Example.
In the drawings, reference Numerals are:
1 boiler 2 steam separator 3 wellhead separator 4 separator oil tank 6 separator 7 raw-water tank 6?702-562 CA 02769064 2012-02-24 8 softener 9 after filter ultrafiltration equipment 11 ultrafiltration membrane module

12 permeated-water tank

13 ion exchange equipment

14 tank for boiler feed water 21 crystallizer Detailed description of embodiments of the invention [0012]
A method of recovering oil from an extra heavy oil layer is described referring to FIG. 1. Note that, in FIG. 1, a process flow except for an ultrafiltration membrane equipment 10 and lines provided therewith is the same as a process flow executed in a known SAGD method.
Steam is supplied from a boiler 1 through a line la to a steam separator 2.
The steam separator 2 can recover part of the steam as condensed water.
High-temperature steam separated by the steam separator 2 is injected under pressure from a line 2a into an extra heavy oil layer.
[0013]
Extra heavy oil contained in the extra heavy oil layer is reduced inviscositybythe high-temperature steaminjectedunder pressure to give a mixture of high-temperature water, which is obtained by condensation of the steam, and oil.
The mixture of high-temperature water and oil is recovered from a line 3a to be delivered to a wellhead separator 3 where a gas component is separated.
The mixture of high-temperature water and oil, from which the gas components are separated away, is delivered through a line 3b to a separator 4 where the mixture is separated into the high-temperature water and the oil.
The oil obtained by the separation in the separator 4 is delivered through a line 4a to an oil tank 5 so as to be recovered as oil from a line 5a.
[0014]
The high-temperature water obtained by the separation in the separator 4 still contains oil therein and therefore is delivered through a line 4b to a separator 6 (for separating oil) to separate residual oil.
The high-temperature water after the oil is separated by the separator 6 (for separating oil) is delivered through a line 6a to a raw-water tank 7. Raw water in the raw-water tank 7 has a pH of about 6 to 7.

[0015]
The raw water at a high temperature (about 90 to 100 C) in the raw-water tank 7 is delivered through a raw-water line 7a to a softener 8. In the softener 8, a softening treatment corresponding to a step of removing a hardness component such as calcium and magnesium, silica, and the like is conducted.
Although the raw water is cooled even in a process for the softening treatment by the softener 8, river water or well water can be fed from a line 7b for further cooling as needed.
As a method for the softening treatment, a precipitation method with a coagulant, an adsorption method with an adsorbent, or the like can be employed.
When the precipitation method with a coagulant is employed, a method including adding, for example, calcium hydroxide (lime) and magnesium oxide can be employed.

[0016]
The raw water subjected to the softening treatment in the softener 8 is delivered through a line 8a to an after filter 9 where a coarse filtration treatment is performed.
The after filter 9 can remove larger impurities such as suspended solids by filtration.

[0017]
The raw water subjected to the coarse filtration by the after filter 9 is delivered through a line 9a to the ultrafiltration equipment 10 where a filtration treatment is performed.
When a temperature of the raw water fed to the ultrafiltration membrane equipment 10 is too high, an ultrafiltration membrane module is deteriorated, resulting in the need of early replacement of the module. Therefore, it is preferred that the temperature of the raw water be cooled to be in the range of 60 to 90 C.
The adjustment of the temperature of the raw water is sometimes performed by natural cooling when the raw water passes through each of the lines in the course through the softener 8 and the after filter 9 described above to the ultrafiltration membrane equipment 10. Besides, an air-cooling zone including air-cooling means or a water-cooling zone including water-circulating type water-cooling means can be provided in each of the lines (for example, the lines 6a and 7a) to the ultrafiltration membrane equipment 10.

[0018]
Any ultrafiltration membrane equipment may be used as the ultrafiltration membrane equipment 10 as long as the ultrafiltration membrane equipment includes an ultrafiltration membrane module 11, a permeated-water tank 12 for storing the permeatedwater after the ultrafiltration therein, and a pressure pump. The one as illustrated in FIG. 2 can be used.
Although the ultrafiltration membrane equipment 10 including the ultrafiltration membrane module 11, the permeated-water tank 12, and the pressure pump which are combined into one equipment is preferred, an ultrafiltration membrane equipment including the components provided separately may also be used.

[0019]
A pressure pump 10A is provided between the line 9a and the ultrafiltration membrane module 11 illustrated in FIG. 1.
The raw water whose pressure is boosted to a predetermined pressure by the pressure pump 10A is fed to the ultrafiltration membrane module 11 where an ultrafiltration treatment is performed.
Permeated water obtained by the filtration treatment in the ultrafiltration membrane module 11 is delivered through permeated-water lines ha and llf (Fig4) which are opened by operating three-way valves 10a and 10b to a permeated-water tank 12 so as to be stored therein.
Concentrated water generated during the filtration treatment conducted in the ultrafiltration membrane module 11 is delivered through the line llb (Figl) to the raw-water tank 7 or the line 6a (or the line 7a) before or after the raw-water tank 7 where a circulation process is performed. By the circulation process, a recovery rate of water is increased to save a supply water amount of the river water or well water.

[0020]
During a filtration operation of the ultrafiltration membrane module 11, back-pressure washing is conducted so as to maintain filtration performance.
The back-pressure washing is performed by actuating a back-pressure washing pump 10B to feed the permeated water in the permeated-water tank 12 through a back-pressure washing line 12b and the permeated-water line ha which is opened by operating the three-way valve 10b (the permeated-water line lib is closed) to the ultrafiltration membrane module 11. (Fig4) Intervals of conducing the back-pressure washing can be appropriately set in accordance with the degree of decrease of a permeated-water amount. For example, by the back-washing for about 30 to 90minutes for each interval, a stable permeated-water amount can be kept. A time period for one back-pressure washing is, for example, 0.5 to 2 minutes.
It is preferred to perform the back-pressure washing under a pressure of 0.1 to 0.2 MPa.
Washing waste water after the back-pressure washing is partially delivered, by operating a three-way valve 10c, through a line lid to the raw-water tank 7 or the line 6a or 7a before or after the raw-water tank 7 so as to be subjected to the circulation process. At this time, the washing waste water can also be delivered to the raw-water tank 7 or the line 6a or 7a before or after the raw-water tank 7 so as to be subjected to the circulation process after being subjected to a coagulation sedimentation treatment by adding a coagulant or an adsorption treatment using an adsorbent (such as activated carbon or anthracite) . By conducting the treatments under an acidic condition with a pH of 4 to 6, the efficiency of removal of a humic substance contained in the washing waste water can be enhanced. By the circulation process, the water recovery rate can be increased to save the water intake amount.
The remaining washing waste water is drained from a line lie by operating the three-way valve 10c. Tn he drained washing waste water can also be used in the water-circulating type water-cooling zone.

[0021]
A structure itself of the ultrafiltration membrane module 11 is well known and is such that a case housing including a raw-water inlet, a permeated-water outlet, and a concentrated-water outlet is filled with the ultrafiltration membrane.
A hollow fiber membrane made of a heat-resistant resin is preferred as the ultrafiltration membrane because a temperature of the raw water to be treated is high. As the hollow fiber membrane, any of an internal-pressure type one and an external-pressure type one may be used. In view of washing performance of the back-pressure washing, the internal-pressure type one is preferred. In the case of the internal-pressure type hollow fiber membrane, an inner diameter of 0.5 to 1.2 mm and an outer diameter of 0.8 to 2.0 mm are preferred, and an inner diameter of 0.8 to 1.0 mm and an outer diameter of 1.3 to 1.6 mm are more preferred. When the inner diameter is 0.5 mm or more, a permeation flow rate is prevented from being lowered owing to clogging of the hollow fiber membrane. On the other hand, when the inner diameter is 1.2 mm or less, an effective membrane area per module can be increased to save the cost.

[0022]
Further, a main component of the water-soluble organic substance (s) contained in the raw water is the humic substance.
Therefore, in order to efficiently separate the humic substance and the raw water, the hollow fiber membrane having a molecular weight cut-off of 8,000 to 30,000 is preferred.
When the molecular weight cut-off exceeds 30,000, the removal of the humic substance becomes insufficient, resulting in a risk of difficulty of the reuse of water. On the other hand, when the molecular weight cut-off is less than 8,000, the amount of permeated water through the membrane becomes smaller even though the removal of the humic substance is sufficient.
As a result, the size of the ultrafiltration membrane equipment becomes large by increasing a membrane area or increasing a operation pressure of the pump. As a result, there is a risk in that the equipment becomes economically inadequate.
The molecular weight cut-off is determined from a permeation rate and a rejection rate for solutes when a membrane filtration test is conducted using a dilute solution containing polyethyleneglycol and a trypsin inhibitor having predetermined molecular weights as the solutes. In the case of the present invention, a UF membrane having a molecular weight cut-off with a permeation rate of 20% or more for polyethyleneglycol = CA 02769064 2012-02-24 (molecular weight cut-off of 12,000) and a rejection rate of 90% or more for the trypsin inhibitor (molecular weight cut-off of 28,000) is preferred.
As the hollow fiber membrane made of a heat-resistant resin, a polysulfone, a polyethersulfone, a polyvinylidene fluoride, a polytetrafluoroethylene and the like are preferred. Of those, polyethersulfone which allows low molecular weight cut-off ultrafiltration and has heat resistance is more preferred.
As the ultrafiltration membrane module 11, for example, an FE10 module and an FW50 module manufactured by Daicen Membrane-Systems Ltd. can be used.
As the hollow fiber membrane made of the polyethersulfone membrane, for example, FUS0181, FUSO1C1, and FUS0382 manufactured by Daicen Membrane-Systems Ltd. can be used.

[0023]
Operating conditions of the ultrafiltration module 11 can be set as described below.
An operation pressure is 0.02 to 0.08 MPa, preferably 0.03 to 0.06 MPa in terms of a transmembrane pressure obtained by subtracting a permeation pressure from an average value of an inlet pressure and an outlet pressure of themodule . Across-flow velocity is preferably 0.1 to 0.6 m/s, more preferably 0.1 to 0.3 m/s.
It is preferred to perform the filtration operation at a permeation flow rate of about 1.0 to 1.5 m/day. Further, a = CA 02769064 2012-02-24 recovery rate of the permeated liquid is preferably 80 to 95%.

[0024]
It is preferred that 70% or more of an organic substance (humic substance) be removed from the permeated water obtained by the ultrafiltration treatment in the ultrafiltration membrane module 11 as compared with the raw water before being subjected to the filtration treatment. It is more preferred that 80% or more thereof be removed, and it is even more preferred that 85%
or more thereof be removed.

[0025]
In the permeated water subjected to the ultrafiltration treatment of the present invention a humic acid is removed.
Therefore, even when the NF-membrane equipment or the RO-membrane equipment are provided downstream of the ultrafiltration treatment so as to perform the membrane treatment, a concentration of the humic substance which causes fouling of the NF membrane or the RO membrane is kept low. Accordingly, the stable membrane treatment operation can be performed. Thus, the acquisition of treatedwater substantially free of impurities is expected.

[0026]
The permeated water in the permeated-water tank 12 is delivered through a line 12a to an ion exchange equipment 13 where an ion exchange treatment is performed, and is then delivered through a line 13a to a tank for boiler feed water = CA 02769064 2012-02-24 14, to be stored therein.
The ion exchange equipment 13 includes an ion exchange membrane, an ion exchange resin, or a combination thereof as an ion exchanger. In the ion exchange equipment 13, the permeated water subjected to the filtration treatment by the ultrafiltration membrane equipment10 is treated as water to be treated. Therefore, a load on the ion exchange equipment 13 is reduced. Accordingly, a time period in which the ion exchanger is available can be further increased (the frequency of replacement of the ion exchanger can be reduced) .

[0027]
Thereafter, the permeated water in the tank for boiler feed water 14 is delivered through a line 14a to the boiler 1 to become high-temperature steam, which is then delivered through the line la to the steam separator 2.
In the boiler 1, the permeated water with the concentration of the humic substance sufficiently lowered by the ultrafiltration membrane equipment 10 is used. Therefore, a problem of precipitation of the humic substance in the boiler 1 is remarkably improved. Therefore, an interval between works for stopping the operation of the boiler 1 to remove coke inside a heating tube can be further increased. As a result, a workload therefor is reduced, while the operating time period of the boiler 1 can be further increased. Therefore, an operating rate can also be enhanced.

[0028]
Note that, in the case where part of the steam is recovered as condensed water (condensed water mainly containing sodium chloride) in the steam separator 2, the condensed water is delivered through a line 2b to a crystallizer 21 to remove the impurity (sodium chloride) and the like by crystallization.
When the amount of the humic substance remaining in the condensed water is large in this process, the humic substance disturbs crystal precipitation of sodium chloride and the like to lower the efficiency of removal of the impurity by the crystallization. In the present invention, however, the humic substance is removed in the ultrafiltration membrane equipment 10. Therefore, the efficiency of crystallization in the crystallizer 21 is improved to enhance a removal rate of the impurity (sodium chloride) as well.
The removed impurity is drained from a line 21a. Water after the removal of the impurity is delivered through a line 21b to the line 7a so as to be subjected to the circulation process .
By the circulation process, the water recovery rate can be enhanced to save the water intake amount.

[0029]
Next, another embodiment of a process flow illustrated in FIG. 1 is described referring to FIG. 2.
In the process flow illustrated in FIG. 2, when part of the steam is recovered as the condensed water (condensed water mainly containing sodium chloride) in the steam separator 2, the condensed water is delivered through the line 2b to an ultrafiltration membrane module 11' where the ultrafiltration treatment is performed.
A filtrate obtained in the ultrafiltration membrane module 11' is delivered through a line 2d to the crystallizer 21 where the impurity (sodium chloride) and the like are removed by the crystallization.
A concentrated liquid generated in the ultrafiltration membrane module 11' is returned to the line 6a to be then delivered to the raw-water tank 7 or is directly returned to the raw-water tank 7.
The impurity removed by the crystallizer 21 is drained from the line 21a. Water after the removal of the impurity is delivered from the line 21b to the line 7a so as to be subjected to the circulation process.
By providing the ultrafiltration membrane module 11', a load on the crystallizer 21 can be reduced to enhance the effect of saving the water intake amount.

[0030]
Next, still another embodiment of the process flow illustrated in FIG. 1 is described referring to FIG. 3. In the process flow illustrated in FIG. 3, when part of the steam is recovered as the condensed water (condensed water mainly containing sodium chloride) in the steam separator 2, the condensed water is delivered through the line 2b to a multieffect evaporator 22, the ultrafiltration membrane module 11 ' , and the crystallizer 21 in the stated order so as to be treated.
A treated liquid in the multieffect evaporator 22 is delivered through the line 2d to the ultrafiltration membrane module 11 ' . An distillate liquid from the top is delivered through a line 2e to the line 7a.
The treated liquid (filtrate) in the ultrafiltration membrane module 11' is delivered through a line 2g to the crystallizer 21. A concentrated liquid is returned through a line 2f to the line 6a to be then delivered to the raw-water tank 7 or is directly returned to the raw-water tank 7.
The impurity removed by the crystallizer 21 is drained from the line 21a. Water after the removal of the impurity is delivered through the line 21b to the line 7a so as to be subjected to the circulation process.
By providing the multieffect evaporator 22 and the ultrafiltrationmembranemodule 11' , the load on the crystallizer 21 can be reduced to enhance the effect of saving the water intake amount.
Examples

[0031]
Example and Comparative Example An evaluation was made for each sample obtained in the flow illustrated in FIG. 1 when ultrafiltration was conducted.

= CA 02769064 2012-02-24

[0032]
<Raw-water sample>
For raw water for the UFmembrane treatment, a treated liquid obtained by subjecting the high-temperature water from the raw-water tank 7 to the softening treatment in the softener 8 and then subjecting the resultant to the coarse filtration treatment with the after filter 9 was used as the raw water.

[0033]
<Ultrafiltration membrane equipment>
An experimental filtration equipment illustrated in FIG.
was used.
A hollow fiber membrane 102 was provided between a container 101 corresponding to the raw-water tank (containing a raw-water sample) and a container 104 corresponding to a concentrated-water tank. Membrane-permeated water was obtained by an internal-pressure filtration method.
A container 103 corresponding to a permeated-water tank was provided just below the hollow fiber membrane 102 so as to be able to store the permeated water treated by the hollow fiber membrane (UF membrane) 102.

[0034]
<Types of membrane>
As the hollow fiber membranes made of polyethersulfone (PES) and having molecular weight cut-offs of 10,000, 30,000, and 150,000, FUS0181, FUS0381, and FUS1581 manufactured by Daicen = CA 02769064 2012-02-24 Membrane Systems Ltd. were used, respectively.
In a permeation test illustrated in FIG. 5, one hollow fiber membrane having a length of 1 m was used. The UF membranes used each had an inner diameter of 0.8 mm and an outer diameter of 1.3 mm.
As the membrane having a molecular weight cut-off of 5,000, a flat membrane made of PES (Microdyn UP005 manufactured by Microdyn-Nadir GmbH) was used and provided in accordance with the equipment illustrated in FIG. 4.

[0035]
<Operating conditions>
(Hollow fiber membrane) Pressure at membrane inlet 102a: 0.050 MPa Pressure at membrane outlet 102b: 0.035 MPa Recovery rate (permeated-water amount/raw-water amount) :
30 to 50%
Temperature of raw-water sample: 25 C or 65C
Filtration method: internal-pressure cross-flow filtration (Flat membrane) Pressure at membrane inlet: 1 MPa Filtration method: dead-end filtration Raw-water circulating amount: 1.2 L/min Temperature of raw-water sample: 25 C

[0036]

The results with the OF membranes with the respective molecular weight cut-offs are shown in FIGS. 6 and 7.
With the OF membranes with molecular weight cut-offs of 10,000, 30,000, and 150,000, a flux of 1.2 to 1.5 m3/m2.day was obtained even under a low pressure of 0.05 MPa. On the other hand, as shown in FIG. 6, when the flat membrane having a molecular weight cut-off of 5,000 was used, the membrane permeation became unavailable immediately after the start owing to fouling of the surface of the membrane. Even after the operation for 3 hours, the permeated liquid was not, successfully obtained. The reason is believed that the humic substance clogged the surface of the membrane.

[0037]
Next, when the organic substance to be removed was the humic substance in the membrane permeation experiment shown in FIGS.
6 and 7, a removal rate of the humic substance was defined by the following equation because a concentration thereof can be represented by an absorbance at the wavelength of 465 nm due to an aromatic ring of the humic substance ("Effect of the fractionation and immobilization on the sorption properties of humic acid", Soil Biology and Biochemistry volume 21, issu 2, 1989, Pages 223-230) . The results are shown in Table 1 and FIG.
8.
Removal rate of humic substance: R= (absorbance of permeated water at 465 nm/absorbance of raw water at 465 nm) x100 * CA 02769064 2012-02-24 [0 0 3 8]

[Table 1]

Removal rate (%) of humic substance Example 1 PES membrane (molecular weight cut-off of 10,000) 90 Example 2 PES membrane (molecular weight cut-off of 30,000) Example 3 PES membrane (molecular weight cut-off of 150,000) Example 4 PES membrane (molecular weight cut-off of 5,000)Unmeasurable because of unavailability of permeated liquid [0039]

As clear from Table 1 and FIG. 8, it was confirmed that about 80% of the humic substance was able to be removed by using the UF membrane having a molecular weight cut-off of 30,000 and 90% or more of the humic substance was able to be removed by using the UFmembrane having a molecular weight cut-off of 10,000.

Moreover, as understood from FIG. 8, with the UF membrane having a molecular weight cut-off of 10,000, the result that the removal rate of the humic substance at as high a temperature as 65 C

was slightly larger than that at 25 C was obtained.

On the other hand, with the UF membrane having a molecular weight cut-off of 150,000, the removal rate of the humic substance was only 70% or less . Therefore, the removal rate is insufficient.

With the UF membrane having a molecular weight cut-off of 5,000, the membrane was clogged immediately after the start of the filtration experiment as shown in FIG. 6. Therefore, the permeation experiment was not successfully conducted.

Claims (8)

CLAIMS;

1. A method of recovering oil from an extra heavy oil layer, comprising separating and recovering oil and high-temperature water from a mixture of the oil and the high-temperature water, which is obtained by injecting high-temperature steam into the extra heavy oil layer, and then reusing the high-temperature water to generate the high-temperature steam, the method comprising the step of subjecting raw water, which is obtained by cooling the high-temperature water to a temperature of 60 to 90°C, to ultrafiltration by feeding the raw water to an ultrafiltration membrane equipment, thereby providing permeated water with a reduced content of a water-soluble organic substance, wherein:
the permeated water is reused to generate the high-temperature steam; and the ultrafiltration membrane equipment used in the ultrafiltration step includes an ultrafiltration membrane module filled with a hollow fiber membrane or hollow fiber membranes which is made of a heat-resistant resin and has a molecular weight cut-off of 8,000 to 30,000.

2. A method of recovering oil from an extra heavy oil layer, comprising separating and recovering oil and high-temperature water from a mixture of the oil and the high-temperature water, which is obtained by injecting high-temperature steam into the extra heavy oil layer, and then reusing the high-temperature water to generate the high-temperature steam, the method comprising the steps of:
charging the high-temperature water separated from the mixture of the oil and the high-temperature water into a raw-water tank;
subjecting the high-temperature water in the raw-water tank to a softening treatment by delivering the high-temperature water to a softener;
subjecting the high-temperature water subjected to the softening treatment in the previous step to a coarse filtration treatment;
subjecting raw water, which is obtained by cooling the high-temperature water to a temperature of 60 to 90°C, to ultrafiltration by feeding the raw water to an ultrafiltration membrane equipment, thereby providing permeated water with a reduced content of a water-soluble organic substance(s); and subjecting the permeated water from which the water-soluble organic substances are removed in the previous step to an ion exchange treatment, wherein:
the permeated water subjected to the ion exchange treatment is reused to generate the high-temperature steam; and the ultrafiltration membrane equipment used in the ultrafiltration step includes an ultrafiltration membrane module filled with a hollow fiber membrane hollow or fiber membranes which are made of a heat-resistant resin and has a molecular weight cut-off of 8,000 to 30,000.

3. The method of recovering oil from an extra heavy oil layer according to claim 1 or 2, wherein:
the ultrafiltration membrane equipment includes the ultrafiltration membrane module filled with a hollow fiber membrane or hollow fiber membranes which is made of a heat-resistant resin and has a molecular weight cut-off of 8,000 to 30 , 000 , a permeated-water tank for storing the permeated water after the ultrafiltration, and a pressure pump; and the ultrafiltration membrane module and the permeated-water tank include a permeated-water line for delivering the permeated water from the ultrafiltration membrane module to the permeated-water tank, a back-pressure washing line for delivering back-pressure washing water from the permeated-water tank to the ultrafiltration membrane module, and a concentrated-water line for draining concentrated water generated in the ultrafiltration membrane module.

4. The method of recovering oil from an extra heavy oil layer according to claim 3, wherein:
the ultrafiltration membrane equipment further includes a drainage line for the back-pressure washing water, the concentrated-water line is connected to the raw-water tank or a line before or after the raw-water tank; and the drainage line for the back-pressure washing water is connected to the raw-water tank or the line before or after the raw-water tank.

5. The method of recovering oil from an extra heavy oil layer according to any one of claims 1 to 4, wherein the ultrafiltration membrane equipment is an internal-pressure cross-flow filtration type ultrafiltration membrane equipment.

6. The method of recovering oil from an extra heavy oil layer according to any one of claims 1 to 5, wherein the hollow fiber membrane made of a heat-resistant resin is a polyethersulfone membrane.

7. The method of recovering oil from an extra heavy oil layer according to any one of claims 1 to 6, wherein a pH of the treated water cooled to 60 to 90°C to be treated in the ultrafiltration membrane equipment falls within a range of 8 to 10.

8. The method of recovering oil from an extra heavy oil layer according to any one of claims 1 to 7, wherein the water-soluble organic substance contains a humic substance.