JP7450215B2 - Treatment method for water produced by oil drilling - Google Patents

Description

The present invention relates to a method for treating water produced from oil drilling.

When drilling for oil at an oil drilling site, groundwater is pumped along with the oil. The produced water pumped up in this way (sometimes referred to as "produced water" in the present invention) contains COD components such as oil, soil-derived suspended matter (sludge), and inorganic salts. include. Moreover, the amount of produced water generated is large, said to be several times more than the amount of oil pumped up, and is a difficult waste to dispose of. In order to protect the drilling drill, drilling mud is supplied to the drilling drill. This drilling mud also mixes with the produced water and forms part of the produced water.

Currently, many oil drilling sites are located in remote areas without developed infrastructure, but there are ways to properly treat produced water by transporting the produced water to a factory with appropriate wastewater treatment equipment and treating it there. One possible method is to install such wastewater treatment equipment on-site and treat it on the spot. However, the former is not realistic from the viewpoint of transportation costs.

In addition, treated and purified water is discharged into rivers, but the residue produced as a result of treatment requires further treatment processes such as solidification and landfilling. Therefore, how to reduce (concentrate) the amount of generated residue is an important factor in the treatment of produced water.

Regarding the above-mentioned on-site method of treating produced water, Patent Documents 1 and 2 disclose that produced water is subjected to reverse osmosis membrane treatment (after preliminary precision membrane filtration), and then A method for evaporating and concentrating the obtained concentrated water is disclosed.

WO2013/153587 publication WO2012/008013 publication

However, according to studies by the present inventors, the methods proposed in Patent Documents 1 and 2, in which a reverse osmosis membrane is used to perform a separation process on produced water, have the following problems. First, the composition of produced water varies greatly, especially regarding oil content. That is, when a drilling drill is drilling into a water layer, the produced water is relatively clean and contains very little oil. On the other hand, when the drilling drill approaches an oil layer, the produced water contains a large amount of oil. Other times, the drill drill is simply digging into the soil. Furthermore, produced water also contains substances derived from soil and components derived from drilling mud, and is a mixture with a complex composition.

The reverse osmosis membrane used in the method of Patent Document 1 etc. has very excellent separation performance, so it has excellent purification performance of produced water, but as mentioned above, produced water is a mixture with a complex composition. The load on the membrane is so high that it soon becomes unusable. For this reason, in the actual operation of oil drilling produced water treatment, the frequency of membrane replacement is high, and when considering the amount of produced water generated, the cost of producing produced water becomes enormous. This problem becomes particularly noticeable when the resulting water contains a large amount of oil and other components (particularly protective agents derived from mud and drilling mud (high molecular compounds such as polysaccharides such as guar gum) that can clog the membrane).

The present invention was made under the above circumstances, and the problem it seeks to solve is to provide a method that can condense oil, etc. and discharge it at low cost, even if the produced water is more contaminated with oil, etc. The object of the present invention is to provide a treatment method that purifies the water to a certain level.

In order to solve the above-mentioned problems, the present inventors conducted intensive research and found that if contaminated water is subjected to coagulation-sedimentation treatment and the resulting clear water is subjected to evaporation concentration treatment, it can be done at low cost. They discovered that it is possible to obtain condensed water that has been purified to a level that can be discharged, and concentrated water that can be treated appropriately, and have completed the present invention.

That is, the first invention for solving the problem is:
A method for treating water produced by oil drilling, the method comprising:
A step of subjecting the oil drilling produced water to a coagulation-sedimentation treatment and separating it into clear water and precipitate;
This is a method for treating water produced from oil drilling, which includes a step of subjecting the clear water to evaporation concentration treatment to obtain condensed water and concentrated water.
The second invention is
The oil drilling associated water according to the first invention, wherein the oil concentration in the oil drilling associated water is 100 to 5000 ppm, the COD is 10 to 20,000 ppm, and the inorganic salt concentration is 200 to 35,000 ppm as TDS. It is a water treatment method.
The third invention is
The first or second invention further comprises a step of measuring the oil concentration in the condensed water and, if it is found to exceed a predetermined value, removing the oil from the condensed water using an oil separation membrane. This is a method for treating water produced from oil drilling as described in .
The fourth invention is
Further, according to any one of the first to third inventions, the method further comprises a step of measuring the nitrogen concentration in the condensed water and, if it is found that it exceeds a predetermined value, performing a treatment to remove nitrogen from the condensed water. This is the method for treating water produced from oil drilling.
The fifth invention is
The method for treating water produced by oil drilling according to any one of the first to fourth inventions, wherein the clarified water has an oil concentration of 5 to 1000 ppm.
The sixth invention is
The oil drilling companion according to any one of the first to fifth inventions, wherein the concentration of oil in the condensed water is 5 to 100 ppm, the COD is 5 to 200 ppm, and the concentration of inorganic salts is 10 to 100 ppm as TDS. It is a water treatment method.
The seventh invention is
According to the first to sixth inventions, the evaporation concentration process is carried out using an evaporation concentration device that can be transported by a vehicle, or an evaporation concentration device that can be separated into 2 to 4 units that can be transported by a vehicle. The method for treating water produced by oil drilling according to any one of the above.
The eighth invention is
The method for treating oil drilling produced water according to any one of the first to seventh inventions, wherein a treatment for removing organic components in the oil drilling produced water is performed before the coagulation and precipitation treatment.

According to the present invention, even if produced water is more contaminated, it is possible to concentrate oil and the like and purify it to a level where it can be discharged at low cost.

FIG. 2 is a diagram showing an operation flow and an example of a treatment device of a method for treating water produced by oil drilling according to the present invention.

As mentioned above, the present invention deals with groundwater pumped up together with oil during oil drilling at an oil drilling site, and which contains not only oil but also COD components, soil-derived suspended solids (mud), and inorganic salts. This is a low-cost treatment method that condenses produced water (which also contains drilling mud) and purifies it to a level that can be discharged.

The method for treating water produced by oil drilling according to the present invention includes a coagulation-sedimentation treatment step in which produced water is subjected to a coagulation-sedimentation treatment and separated into clear water and precipitate; and an evaporation concentration treatment step to obtain. Furthermore, in the method for treating water produced from oil drilling according to the present invention, an oil removal step for removing oil from the condensed water is optionally provided, and a denitrification treatment step is optionally provided for removing nitrogen from the condensed water. There are cases. Further, if desired, an organic component removal step may be provided before the coagulation and precipitation treatment step.

The present invention will be described below with reference to FIG. 1, which shows an example of an operation flow of a processing method and a processing apparatus according to the present invention.

As shown in FIG. 1, the present invention receives produced water (10) from which organic components have been removed by an organic component removal step [1'] as necessary, coagulates and precipitates the produced water (10), and then produces clear water ( 11) and a coagulation-precipitation treatment step [1] to obtain a precipitate (12); and an evaporative concentration step in which clear water (11) is received and subjected to evaporation concentration treatment to obtain condensed water (21) and concentrated water (22). It has a treatment step [2]. The condensed water (21) is returned to the environment by, for example, being discharged into a river or the sea, and the condensed water (22) is subjected to appropriate treatment such as being transported to a disposal site and solidified. In FIG. 1, for convenience, the produced water received in the organic component removal step [1'] is indicated as "produced water (10)".

However, if the condensed water (21) contains oil or nitrogen in an amount higher than a predetermined standard, the oil removal step [3] of removing the oil from the condensed water (21) and/or the condensed water (21) It is preferable to provide a denitrification step [4] for removing nitrogen from the base.

Hereinafter, [1'] organic component removal step, [1] coagulation precipitation treatment step, [2] evaporation concentration treatment step, [3] oil removal step, [4] denitrification step, [5] precipitate and concentrated water. The present invention will be explained in order of processing.

[1'] Organic component removal step If the produced water (10) contains a large amount of organic components, the organic component removal step [1'] is carried out before the coagulation-sedimentation treatment step [1]. It's okay. In this case, it is preferable to provide a biological treatment tank (17) before the flocculation tank (15) that performs the coagulation-sedimentation treatment step [1]. Organic components are decomposed by aerobic/anaerobic treatment. A preferred example of the biological treatment tank (17) is an SBR tank because it allows selection of aerobic and anaerobic conditions and has high solid-liquid separation stability.

[1] Coagulation and precipitation treatment step In the present invention, after implementing the organic component removal step [1'] on the produced water (10) as needed, the coagulation and precipitation treatment step [1] is carried out. The produced water (10) received in this step is a mixture with a complex composition, as described above, and is typically black to brown in color. The oil concentration usually varies widely, from about 100 to 5000 ppm. This is because, as mentioned above, the composition of the produced water (10) changes greatly depending on when the drilling drill is drilling near an oil layer, when drilling near a water layer, or when neither of these conditions exist. be. Specifically, when a drilling drill is drilling near an oil layer, the oil content shows a high value. The COD of the produced water is usually about 10 to 20,000 ppm, and the concentration of inorganic salts is usually about 200 to 35,000 ppm as TDS. The present invention can treat even if the oil concentration in the produced water (10) is high, without any problem, and is preferably applicable to the produced water (10) with an oil concentration of 120 to 5000 ppm. It is more preferably applicable to produced water (10) of 150 to 5000 ppm.

In addition, if the oil concentration is so thick as to exceed 5000 ppm, the oil will be floating on the surface of the produced water, so it is possible to bring the concentration within the above range by scooping it up and then carry out the coagulation-sedimentation treatment step [1]. preferable.

The coagulation-sedimentation treatment step [1] is a coagulation treatment using a coagulation tank (15) followed by a sedimentation treatment to remove soil-derived suspended matter (sludge) in the produced water (10) and produce clear water (11). The purpose is to obtain. The coagulation-sedimentation treatment is often preferable in that it is possible to also remove some of the COD and oil in the produced water (10).

In the coagulation-sedimentation treatment step [1], a coagulant is first added to the coagulation tank (15) containing the produced water (10), and substances that can be captured by the coagulant (such as the above-mentioned suspended matter) are coagulated. Examples of the flocculant include an inorganic flocculant (13) and a polymer flocculant (14). Preferred examples of the inorganic flocculant (13) include polyferric sulfate, polyferric chloride, polyaluminum chloride, polyaluminum sulfate, and the like. Preferred examples of the polymer flocculant (14) include anionic flocculants, cationic flocculants, and nonionic flocculants.

Among these flocculants, polyferric sulfate has an excellent oil removal function, can form and remove precipitates with components that cause scale, such as calcium, and can be used when the pH changes during a series of treatments for produced water (10). It has the excellent feature that the precipitate does not re-dissolve even when the pH reaches about 10 (particularly when the pH reaches about 10). These characteristics are preferable from the viewpoint of maintaining stable operation of the subsequent evaporation concentration treatment step [2].

In the coagulation-sedimentation treatment step [1], the produced water (10) in which aggregates have been generated due to the coagulation described above is subjected to solid-liquid separation using a solid-liquid separator (16) (as a specific example, using a centrifugal separator). Clear water (11) and precipitate (12) are separated by centrifugation, sedimentation using a thickener, filtration using a hollow fiber membrane, decantation from a coagulation tank, etc.). If necessary, the clear water (11) is temporarily stored in the evaporation concentration raw water tank (20).

The oil concentration in the clear water (11) obtained in the coagulation-sedimentation treatment step [1] is usually about 5 to 1000 ppm, and the COD is usually about 10 to 5000 ppm, which may be reduced compared to the starting produced water (10). many. The concentration of inorganic salts is usually about 200 to 35,000 ppm as TDS. In addition, in the clear water (11), the suspended solids (mud) contained in the produced water (10) have been significantly removed, and the color is colorless and transparent to white and translucent, or is derived from the chemicals used in this process. It is the color of

[2] Evaporation concentration treatment step In the evaporation concentration treatment step [2], the clear water (11) obtained in the coagulation and precipitation treatment step [1] is subjected to evaporation concentration treatment using the evaporation concentration device (23). conduct. Through the evaporation concentration process, condensed water (21) and concentrated water (22) are obtained. If the target to be evaporated and concentrated contains coarse substances such as mud, this will be transferred to concentrated water (22), but this will cause problems such as clogging the pipes of the evaporation and concentration equipment, making continuous operation impossible. become unable. In other words, this leads to an increase in operating costs. However, in the present invention, the produced water (10) is first subjected to coagulation and sedimentation treatment to substantially remove coarse substances, so the above problem does not occur and continuous operation is possible, reducing operating costs. It can be kept low.

The evaporation concentration device (23) used in the evaporation concentration treatment step [2] is not particularly limited. For example, a steam compression salt water distiller (steam compression salt water distiller equipped with a horizontal heat exchanger tube and a steam compressor) described in JP-A-59-26184, An evaporative compression type concentrator (a concentrator capable of two-stage compression using two compression means), a vacuum evaporator described in JP-A No. 2011-185192 (a vacuum evaporator equipped with a Roots blower), etc. are used in the process. It can be used as an evaporative concentration device. However, considering that many oil drilling sites are located in remote areas, constructing an evaporative concentrator on-site from scratch would require a long construction period and result in high construction costs.

Here, the present inventors have discovered that it is possible to transport and install the finished product or the evaporative concentrator (23) separated into multiple units to an oil drilling site, or to perform final assembly, installation, and operation. I came up with something nice. Such an evaporation concentration device (23) is of a size that can be transported by a vehicle such as a truck, or can be separated into about 2 to 4 units, and each of the separated units can be transported by a vehicle. It is a large size. Furthermore, the present inventors have discovered that the evaporation concentration device disclosed in Japanese Patent Application Laid-open No. 2018-126680 separates the device into two storage containers (a first storage container and a second storage container in claim 1 of the publication). The present inventors have also come up with the idea that the apparatus is particularly suitable for use in the evaporation and concentration treatment step [2] of the present invention, since each of them can be transported by a vehicle such as a truck.

Regarding the evaporation conditions in the evaporation concentration process [2], it is recommended to set the liquid temperature in the evaporator of the evaporation concentrator (23) to 60 to 80°C and the pressure in the evaporator to 5 to 50 kPa abs to reduce operating costs. preferred from the viewpoint of The concentration ratio of the concentrated water (22) obtained in this process (the volume ratio of the clear water (11) to the concentrated water (22)) should be 2 to 20 times the volume, depending on the concentration and operation of the produced water (10). Preferable from the viewpoint of cost reduction.

When the quality of condensed water (21) obtained through evaporation concentration treatment is checked, the oil concentration is usually about 5 to 100 ppm, the COD is usually about 5 to 200 ppm, and the content of inorganic salts is usually about 10 ppm as TDS. ~100ppm. Since the condensed water (21) is composed of volatile components in the clear water (11), oil content (excluding volatile oil) and other components are significantly reduced. If the oil content, COD, and inorganic salt content of the condensed water (21) is low enough to meet environmental standards, it can be directly discharged into rivers, etc., recycled as water at oil drilling sites, or stored underground. can be returned to.

By carrying out the coagulation-sedimentation treatment step [1] and the evaporation concentration treatment step [2] explained above, condensed water (21) that can be returned to the environment, etc., and precipitate to be treated by an appropriate method are obtained from the produced water (10). A product (12) and concentrated water (22) are obtained. According to the present invention, the concentration ratio from the produced water (10) to the sum of the precipitate (12) and concentrated water (22) (produced water/(precipitate + concentrated water)) is preferably 3 to 15 volume times. It is possible to achieve this magnification. Moreover, both the coagulation-precipitation treatment process [1] and the evaporation concentration treatment process [2] do not require the use of expensive chemicals or equipment, and can be operated continuously. The processing method can be implemented at very low cost.

[3] Oil removal process The oil removal process [3] is performed when the oil contained in the condensed water (21) exceeds a predetermined value as a result of the quality check (measurement of oil concentration) of the condensed water (21) described above. is a step in which, for example, condensed water (21) is subjected to specific gravity separation using an oil separation membrane (33) installed in an oil separation device (32) to obtain treated water (31) and oil (34). It is. Note that the method for measuring the oil concentration will be described later in Examples. Further, the predetermined value is a value determined by standards regarding wastewater such as environmental standards of each country, and this will be explained in detail in the section of the denitrification process [4] described later.

The produced water (10) targeted by the oil drilling produced water treatment method of the present invention described in "Coagulation and precipitation treatment step [1]" generally has a very high oil content. For this reason, if an attempt is made to separate the oil from the produced water (10) using a method using a reverse osmosis membrane, etc. according to the conventional technology represented by Patent Document 1, the load on the reverse osmosis membrane etc. is high and the frequency of Replacement is required, which increases processing costs. Suspended matter (sludge) contained in the produced water (10) can also clog the reverse osmosis membrane (or the microfiltration membrane used before the reverse osmosis membrane), increasing the need for frequent replacement.

The reason why a reverse osmosis membrane is used in the prior art is that the precision membrane filtration that precedes it cannot remove substances of single nano-order or smaller ultrafine size, such as inorganic salts. In contrast, in the case of the present invention, ultrafine-sized substances such as inorganic salts are substantially removed by evaporation concentration treatment (removal focused on boiling point rather than size), and water and volatile oil (removal focused on boiling point rather than size) are substantially removed. Condensed water (21) consisting of 34) and very few other impurities is obtained. The oil (34) exists in the condensed water (21) as droplets of micron level. Removal of such oil (34) does not require an ultra-fine reverse osmosis membrane with a pore size of less than 1 nm, and it is possible to remove oil using a cheaper oil separation membrane (33). . Furthermore, since the condensed water (21) is substantially composed of water and volatile oil (34), the load on the oil separation membrane (33) is light; There is no need for frequent replacement, and the processing cost is low.

As described above, the oil separation membrane (33) does not need to be an expensive membrane such as a reverse osmosis membrane, in which the pore size is on the order of a single nanometer or smaller. In the present invention, a coalescer type membrane can be suitably used as the oil separation membrane (33). This type of oil separation membrane (33) is a membrane composed of fibers with a thickness (diameter if the cross section is circular) of about 0.1 to 10 μm, and water is first poured through it to moisten the fibers. I'll keep it. When condensed water (21) (containing oil content above a predetermined value) is subsequently flowed through the membrane, the water passes through the membrane, but the oil content (34) is repelled by the wet fibers and does not pass through the membrane. When the condensed water (21) continues to flow, oil accumulates on the fibers, coalesces, becomes larger, and is separated according to the specific gravity of the water (specific gravity separation). In this way, oil can be removed from the condensed water (21) by a simple and inexpensive method. In addition, when meeting strict standards regarding oil content, higher-level treatments such as oil removal treatment using activated carbon may be performed as necessary. Such processing can also be carried out at low cost.

As a result of the quality check of the treated water (31) obtained through the oil removal process [3], if the concentration of oil contained in the treated water (31) is below a predetermined value, it may be discharged into a river, recycled, or It can be sent back underground.

[4] Denitrification process In the denitrification process [4], the nitrogen concentration in the condensed water (21) or the treated water (31) obtained in the oil removal process [3] is measured, and the nitrogen concentration is determined to a predetermined value. If the amount exceeds 100%, the step is to use a known denitrification method. This is because if the condensed water (21) (or treated water (31)) contains a large amount of nitrogen, it may cause environmental burden. As the known denitrification method, the chloramine denitrification method is preferred because of its low operating cost. Note that the method for measuring the nitrogen concentration will be described later in Examples. Further, the predetermined value is a value determined by standards regarding wastewater such as environmental standards of each country, and examples are shown in Table 1 below together with the predetermined value regarding the oil wastewater standard in the oil removal step [3] described above. Note that for both the oil content and the nitrogen content, the predetermined value may be set to a value of 5% or more and less than 100% of the wastewater standard value by multiplying the wastewater standard value by a safety factor.

As a result of the quality check of the treated water (31) obtained through the denitrification process [4], if the nitrogen concentration contained in the obtained treated water (31) is below a predetermined value, it will be discharged into a river, etc. , can be recycled or sent underground. Note that if both oil removal and denitrification are required for the condensed water (21), it is preferable to perform oil removal first. This is because if the chloramine denitrification method, which is a typical denitrification method, is performed first, the oil in the condensed water (21) will be oxidized and become water-soluble, making it difficult to remove the oil.

[5] Treatment of precipitate and concentrated water The precipitate (12) explained in “Coagulation and precipitation treatment step [1]” and the concentrated water (22) explained in “Evaporation concentration treatment step [2]” are It is preferable to transport and dispose of it to a suitable disposal site. Considering that many oil drilling sites are located in remote areas, the cost of transporting the sediment (12) and concentrated water (22) to a disposal site is expensive. Therefore, it is important that the amount of these transported is small, that is, the concentration ratio from the produced water (10) is high. From this point of view, when considering the method for treating water produced by oil drilling according to the present invention, as mentioned above, the total amount of sediment (12) and concentrated water (22) is 3% compared to produced water (10). It has been concentrated and reduced in volume by ~15 times. The volume reduction through concentration is considered to be sufficiently effective from the perspective of reducing transportation costs.

Hereinafter, the present invention will be described in more detail with reference to Examples.
In addition, in the examples,
The oil concentration was determined by adjusting the sample to pH 4, extracting it with normal hexane, heating it to 80 ° C. to evaporate the normal hexane, and measuring the weight of the residue.
Inorganic salt concentrations were measured as TDS and total dissolved solids using an Orion ^™ Versa Star Pro ^™ pH/Conductivity desktop multiparameter meter;
The nitrogen concentration was measured as the concentration of ammonia nitrogen (NH ₃ -N) using an ion electrode method (Orion ^TM Versa Star Pro ^TM , manufactured by Thermo Fisher),
HORIBA pH meter F-16 is used to measure the pH value. If the sample temperature at the time of measurement is 25°C, the actual measured value is used, and if it is not 25°C, it is adjusted at 25°C using the built-in calibration function of the pH measuring device. Find the pH value of
COD was measured by the dichromic acid method (COD _Cr ) in accordance with JIS K 0102:2013.

(Reference example)
When the oil concentration was measured in oil drilling produced water (produced water 1 and 2) produced at different times at a certain oil drilling site, the oil concentration in produced water 1 was 3010 ppm, and the oil concentration in produced water 2 was 198 ppm. there were. This result shows that the oil concentration in oil drilling water fluctuates greatly. Note that all of the accompanying water contained a polymer compound as a protective agent. The same applies to the following examples.

(Example 1)
The method for treating oil drilling produced water according to the present invention was carried out using produced water produced at a certain oil drilling site as raw water.
Below, 1. Coagulation and precipitation treatment step, 2. Evaporation concentration treatment step, 3. The oil removal step will be explained in order.

1. Coagulation and sedimentation treatment process The produced water is introduced into the coagulation tank as raw water, and polyferric sulfate (registered trademark: Polytetsu, manufactured by Nittetsu Mining Co., Ltd.) is added there as a coagulant at a ratio of 2 g to 1 L of produced water. did. The resulting water contained suspended matter (mud) and was brown in color.

Then, the mixture was stirred and mixed at 250 rpm for 0.1 hour using a stirrer attached to the flocculation tank. The obtained slurry was centrifuged at 4500 rpm using a centrifugal separator, which is a solid-liquid separator, to separate it into clear water, which is a supernatant, and a precipitate. The clear water was pale orange in color. The amount of precipitate was approximately 1 to 5% by volume of the accompanying water.

2. Evaporation concentration treatment process The separated clear water is once stored in an evaporation concentration raw water tank, and then introduced into an evaporation concentration device (registered trademark: Mobile Evaporator VVCC-40) manufactured by Sasakura Co., Ltd. to perform evaporation concentration treatment. Ta. Note that the evaporation concentration device can be separated into two units (the first storage container and the second storage container disclosed in claim 1 of JP2018-126680A), and each can be transported by truck, etc. It is a device that is

The operating conditions of the evaporative concentration device were such that the degree of vacuum in the evaporator was 20 kPa abs, and the temperature of the retained liquid was 65° C. or higher and 70° C. or lower. Volatile components were evaporated and condensed from the retained liquid while controlling the increase in boiling point due to concentration of the components of the retained liquid to within 8° C. to generate condensed water, which was taken out from the evaporation concentrator. On the other hand, the specific gravity of the liquid held in the evaporator is monitored, and when the specific gravity reaches 1.1 kg/L, it is determined that the liquid has become concentrated water, and the liquid is discharged from the evaporator, thereby performing continuous evaporative concentration processing. Ta. The concentration rate was approximately 3.7 times by volume.

3. Oil removal process Since the oil content contained in the condensed water obtained in the above-mentioned evaporation concentration treatment process was as high as 52 ppm, an oil separation device (registered trademark: Utec TH-80 manufactured by Asahi Kasei) equipped with an oil separation membrane was used. The oil removal step was carried out using a water filter to obtain treated water. Note that this oil separation device was a coalescer type device, and treated water was obtained by removing oil from condensed water through specific gravity separation.

The values of the pH value, inorganic salt concentration (as TDS), ammonia nitrogen concentration, COD value, and oil concentration of the produced water, clear water, condensed water, concentrated water, and treated water in the above operation are shown in Table 2 below.

The oil concentration of the obtained treated water can be further reduced by further treating it with, for example, activated carbon. Further, although it was not carried out in this example, if a denitrification process is carried out on the treated water, the ammonia nitrogen concentration can be easily reduced to 1 ppm or less.

(Example 2)
Produced water produced at an oil drilling site different from that in Example 1 was used as raw water. As in Example 1, 1. coagulation and precipitation treatment step, and 2. An evaporation concentration treatment step was carried out.
Table 3 shows the pH value, ammonia nitrogen concentration, COD value, and oil concentration values of the produced water, condensed water, and concentrated water in the above operations.

Note that if the evaporative concentration treatment step is performed without performing the coagulation-sedimentation treatment step on the produced water, the piping of the evaporation concentration device will become clogged, and the device will soon break down.

1': Organic component removal process 1: Coagulation precipitation process 2: Evaporation concentration process 3: Oil removal process 4: Denitrification process 10: Associated water 11: Clear water 12: Precipitate 13: Inorganic flocculant 14: Polymer Coagulant 15: Coagulation tank 16: Solid-liquid separator 17: Biological treatment tank (SBR tank)
20: Evaporation concentration raw water tank 21: Condensed water 22: Concentrated water 23: Evaporation concentration device 31: Treated water 32: Oil separation device 33: Oil separation membrane 34: Oil content

Claims (8)

A method for treating oil drilling water having an oil concentration of 100 to 5000 ppm ,
A step of subjecting the oil drilling produced water to a coagulation-sedimentation treatment and separating it into clear water and precipitate;
A method for treating water produced by oil drilling, comprising the step of subjecting the clear water to evaporation concentration treatment to obtain condensed water and concentrated water. The method for treating oil drilling produced water according to claim 1, wherein the C OD in the oil drilling produced water is 10 to 20,000 ppm, and the concentration of inorganic salts is 200 to 35,000 ppm as TDS. According to claim 1 or 2, further comprising the step of measuring the oil concentration in the condensed water and, if it is found that it exceeds a predetermined value, removing the oil from the condensed water using an oil separation membrane. A method for treating water produced by oil drilling. The method according to any one of claims 1 to 3, further comprising the step of measuring the nitrogen concentration in the condensed water and, if it is found to exceed a predetermined value, performing a treatment to remove nitrogen from the condensed water. A method for treating water produced by oil drilling. The method for treating oil drilling water according to any one of claims 1 to 4, wherein the oil concentration in the clear water is 5 to 1000 ppm. The oil drilling water according to any one of claims 1 to 5, wherein the condensed water has an oil concentration of 5 to 100 ppm, a COD of 5 to 200 ppm, and an inorganic salt concentration of 10 to 100 ppm as TDS. Processing method. Any one of claims 1 to 6, wherein the evaporation concentration process is carried out using an evaporation concentration device that can be transported by a vehicle, or an evaporation concentration device that can be separated into 2 to 4 units that can be transported by a vehicle. A method for treating water produced by oil drilling as described in . The method for treating oil drilling produced water according to any one of claims 1 to 7, wherein an organic component removal treatment in the oil drilling produced water is performed before the coagulation-sedimentation treatment.