An experimental method for evaluating contribution rate of oil sludge sand to SRB

Abstract

The application discloses an experimental method for evaluating contribution rate of oil sludge sand to SRB, which comprises the following steps: firstly, adding bactericide into oilfield reinjection water to reduce the average corrosion rate of the oilfield reinjection water, so as to prove that the enrichment degree of SRB can be represented by the average corrosion rate in static water body; then, respectively putting metal hangers into at least two containers, respectively filling the containers with oil sludge sand with different thicknesses, and then pouring the oilfield reinjection water into the containers to cover the metal hangers, sealing the containers, cleaning the hangers, and evaluating the average corrosion rate under different thicknesses of the oil sludge sand according to the corrosion degree of the metal hangers, so as to represent the contribution rate to SRB. The application determines the contribution rate of different thicknesses of the oil sludge sand to SRB, improves the current unreasonable situation of sand cleaning period in an oilfield water treatment station, realizes timely sand cleaning before the oil sludge sand breeds a large amount of SRB, and reduces the corrosion of tank bottom and pipelines.

Description

TECHNICAL FIELD

[0001] The present application relates to an experimental method for evaluating the contribution rate of oil sludge to SRB. BACKGROUND

[0002] There is a large amount of oil sludge at the bottom of the settling tank of the oilfield water treatment station, which causes the breeding of SRB (sulfate-reducing bacteria), corrosion of the tank bottom and pipeline, and loss to the oilfield production, and thus the tank needs to be cleaned regularly. At present, the sand cleaning period is not reasonable, and there is a phenomenon that the sand is thin and the SRB has not formed serious corrosion, which increases the number of sand cleaning and affects the normal operation of the water treatment station. It is necessary to determine a reasonable sand cleaning period to avoid the breeding of SRB from too much sludge, which causes corrosion of the tank bottom and wall and causes the water tank to be perforated.

[0003] At present, there is no experimental method for evaluating the contribution rate of oil sludge to SRB. It is known that the oil sludge at the bottom of the settling tank will breed SRB, but the amount of breeding cannot be measured, and only the content of SRB in the upper water body of the oil sludge can be roughly indicated. This method is fast and simple, but it has the following disadvantages: first, the error is large, because the water body above the oil sludge is flowing, the content of SRB in the water body is changing, and the value of each detection fluctuates; second, the amount of SRB bred in the oil sludge and released into the upper water body is not clear, and it cannot be confirmed that all the content of SRB in the water body is contributed by the oil sludge.

[0004] Chinese patent document CN2013101067540 discloses a resource treatment device and method for oil sludge, which uniformly mixes and delivers heated water and compressed air into a stirring tank, sprays high-pressure and high-temperature mixed gas water, and the oil sludge is rapidly broken by high-pressure and high-temperature mixed gas water flushing and stirring in the stirring tank; the oil floats to the oil collector and then enters the cracking tank for cracking reaction to produce crude oil as raw material; the sand and stone with large particle size sink and are reversely washed by high-pressure and high-temperature mixed gas water, collected by a sand scraping machine, and then discharged and delivered by a screw press conveyor; the high-concentration sewage in the stirring tank is settled in the settling tank, and the supernatant is reused, and the fine sludge is used as a raw material for briquette coal.

[0005] CN2011100641350 discloses an oil sludge treatment device and process, which is provided with an original oil sludge inlet and a hot solid carrier backflow port on one side of a rotary kiln, a rotary kiln transmission motor and a slag discharge port, an oil gas outlet and a hot solid carrier discharge port on the other side, the oil gas outlet is connected with a condenser, the hot solid carrier discharge port is connected with a fluidized bed through a lifting hopper, a cyclone separator is arranged in the fluidized bed, solid separation and regeneration of the hot solid carrier are performed through the cyclone separator, the hot solid carrier backflow port is communicated with the rotary kiln, and the bottom of the fluidized bed is connected with a blower through a pipeline.

[0006] CN201010202999 X discloses a method for separating oil sludge, which comprises the following steps: contacting and reacting the oil sludge with a catalyst and an oxidizing agent in the presence of water to obtain water phase, oil phase and sludge; the oxidizing agent is a substance capable of oxidizing the oil in the oil sludge and reducing the viscosity of the oil; the catalyst is a substance capable of promoting the oxidizing agent to generate free radicals with strong oxidizing property.

[0007] The method for separating oil sludge provided by the application can significantly reduce the oil content in the obtained sludge, so that the oil, sludge and water in the oil sludge can be effectively and efficiently separated.

[0008] The above technical solution only separates and processes the oil sludge, and does not solve the technical problem of how to determine a reasonable sand cleaning period.

[0009] Therefore, it is necessary to establish an experimental method for evaluating the contribution rate of oil sludge to SRB, to evaluate the contribution of the amount and thickness of oil sludge to the growth of SRB, determine a reasonable sand cleaning period, and realize the development of oilfield benefits. SUMMARY

[0010] The application provides an experimental method for evaluating the contribution rate of oil sludge to SRB, to determine the contribution of the amount and thickness of oil sludge to the growth of SRB, determine a reasonable sand cleaning period, and realize the development of oilfield benefits.

[0011] The experimental method for evaluating the contribution rate of oil sludge to SRB of the application is realized as follows:

[0012] The corrosion degree of different thickness of oil sludge on the metal coupon is detected to represent the contribution rate of different thickness of oil sludge to SRB; first, a bactericide (quaternary ammonium salt type) for oilfield reinjection water is added to the oilfield reinjection water to reduce the average corrosion rate of the oilfield reinjection water, which proves that the enrichment degree of SRB can be represented by the average corrosion rate in a static water body; then, metal coupons are placed in at least two containers, different thickness of oil sludge is respectively placed in each container, oilfield reinjection water is poured into the containers to cover the metal coupons, the containers are sealed for culture, and then the metal coupons are cleaned; the average corrosion rate under different thickness of oil sludge is evaluated according to the corrosion degree of the metal coupons, which is used to represent the contribution rate to SRB.

[0013] The metal coupon is a standard A3 steel corrosion coupon.

[0014] The container is a wide-mouth bottle,

[0015] The number of containers is 2-6.

[0016] The container quantity is 5, and each container is filled with oil sludge sand of different thickness of 0, 3, 6, 9 and 12 cm respectively.

[0017] The culture is cultured at 48-52 DEG C (simulating the temperature of oilfield produced water in a tank in a water treatment station) for 7-10 days.

[0018] The average corrosion rate is calculated according to the following formula:

[0019]

[0020] In the formula:

[0021] F is the average corrosion rate, and the unit is millimeter per year (mm / year);

[0022] m gf is the mass of the test piece before the test, and the unit is gram (g);

[0023] m hf is the mass of the test piece after the test, and the unit is gram (g);

[0024] S is the surface area of the test piece, and the unit is square centimeter (cm 2 );

[0025] t f is the hanging piece time, and the unit is day (d);

[0026] ρ is the density of the test piece material, and the unit is gram per cubic centimeter (g / cm 3 ).

[0027] The present application determines that the corrosion degree of the A3 steel corrosion hanging piece can reflect the enrichment degree of SRB through experiments, and the average corrosion rate of the corrosion hanging piece under the growth of SRB of different thickness of oil sludge sand is obtained by filling different thickness of oil sludge sand to cover the A3 steel corrosion hanging piece in multiple sealed containers, the upper layer is isolated from air by oilfield reinjection water, and the method is constant temperature culture. The contribution rate of different thickness of oil sludge sand to SRB is represented. The contribution rate of different thickness of oil sludge sand to SRB is clear, the current unreasonable sand cleaning period of the water treatment station of the oil field is improved, the sand is cleaned in time before the large growth of SRB in the oil sludge sand, and the corrosion of the tank bottom and the pipeline is reduced.

[0028] The method of the present application scientifically and reasonably obtains the change curve of the average corrosion rate of different thickness of oil sludge sand, which can directly reflect the change of the SRB content with the thickness of the oil sludge sand. The sand cleaning period is reasonably determined, the phenomenon that the sand is cleaned before the SRB forms serious corrosion is avoided, and the normal operation of the water treatment station is ensured. BRIEF DESCRIPTION OF DRAWINGS

[0029] Figure 1 is a schematic view of the relationship between the thickness of the sludge sand and the average corrosion rate.

[0030] Figure 2 is the picture of A3 steel corrosion coupon after corrosion in five wide-mouth bottles. DETAILED DESCRIPTION

[0031] The experimental method for evaluating the contribution rate of oil sludge sand to SRB of the present application is to detect the corrosion degree of standard A3 steel corrosion coupon caused by different thickness of oil sludge sand, and to represent the contribution rate of different thickness of oil sludge sand to SRB.

[0032] Firstly, it is verified by experiment that adding bactericide can reduce the content of SRB in water, so as to reduce the average corrosion rate, and it is proved that in static water body, the average corrosion rate can be used to represent the enrichment degree of SRB. Then, 5 1L wide-mouth bottles are taken, A3 steel corrosion coupons are respectively put into the wide-mouth bottles, different thickness (0, 3, 6, 9, 12 cm) of oil sludge sand is respectively filled into the wide-mouth bottles, oilfield reinjection water is poured into the wide-mouth bottles, the wide-mouth bottles are sealed, and after 7 days of culture at 50℃, the coupons are cleaned, and the average corrosion rate under different thickness of oil sludge sand is evaluated, which is used to represent the contribution rate of SRB.

[0033] The specific experimental process is described as follows.

[0034] 1. Verify the feasibility of using average corrosion rate to reflect the enrichment degree of SRB

[0035] Two 1L wide-mouth bottles are taken, A3 steel corrosion coupons are respectively put into the wide-mouth bottles, and oilfield reinjection water containing SRB is poured into the wide-mouth bottles, one of the wide-mouth bottles is added with bactericide and sealed, and the other wide-mouth bottle is not added with bactericide, after 7 days of culture at 50℃, the A3 steel corrosion coupons are cleaned, and the average corrosion rate of static water body is evaluated. The experimental results show that adding bactericide can reduce the content of SRB in water, so as to reduce the average corrosion rate. Therefore, in static water body, the average corrosion rate can be used to represent the enrichment degree of SRB.

[0036] 2. Represent the contribution rate of different thickness of oil sludge sand to SRB by the corrosion degree of metal caused by different thickness of oil sludge sand

[0037] Five 1L wide-mouth bottles are taken, A3 steel corrosion coupons are respectively put into the wide-mouth bottles, and different thickness (0, 3, 6, 9, and 12 cm) of oil sludge sand is respectively filled into the wide-mouth bottles, oilfield reinjection water is poured into the wide-mouth bottles, the wide-mouth bottles are sealed, and after 7 days of culture at 50℃, the coupons are cleaned, and the average corrosion rate under different thickness of oil sludge sand is evaluated.

[0038] As Figure 1It is verified that when the thickness of the mud is 0-3cm, the average corrosion rate sharply decreases; when the thickness of the mud reaches 3-6cm, the average corrosion rate sharply increases; and when the thickness of the mud is 6-12cm, the average corrosion rate increases gently, which shows that the SRB grows less within 0-3cm, but the oil in the oil sludge protects the steel from corrosion; within 3-6cm, the number of SRB increases rapidly with the increase of the thickness of the mud; and when the thickness of the mud exceeds 6cm, the growth of SRB slows down obviously with the continuous increase of the thickness of the mud.

[0039] The corrosion state of the A3 steel corrosion hanging piece after corrosion in each jar is shown in Figure 2

[0040] The experimental method of the present application shows that when the thickness of the sand in the jar with a height of 15cm is within 3-6cm, the SRB grows rapidly. When the thickness of the oil sludge in the 10m-high water settlement tank in the oil field reaches 2m, the SRB will start to increase sharply. Therefore, the reasonable sand cleaning height of the 10m-high water settlement tank in the oil field is within 2m, and the sand cleaning should be performed before the thickness of the oil sludge reaches 2m, so as to avoid the corrosion perforation of the tank bottom and the pipeline caused by the sharp increase of the SRB when the thickness of the sand exceeds 2m.​

Claims

1. An experimental method for evaluating the contribution rate of oil sludge to SRB, characterized by: The contribution rate of different sludge thicknesses to SRB was represented by detecting the degree of corrosion caused to metal sludge sheets by different thicknesses of sludge. First, a quaternary ammonium salt bactericide for oilfield reinjection water was added to the oilfield reinjection water to reduce the average corrosion rate of the reinjection water, proving that the average corrosion rate can be used to represent the enrichment degree of SRB in static water bodies. Then, metal sludge sheets were placed in at least two containers, and different thicknesses of sludge were added to each container. Then, the original oilfield reinjection water was poured in to cover the metal sludge sheets. The containers were sealed and incubated, and then the metal sludge sheets were washed. The average corrosion rate under different sludge thicknesses was evaluated based on the degree of corrosion of the metal sludge sheets, and used to represent the contribution rate to SRB.

2. The experimental method for evaluating the contribution rate of oil sludge to SRB according to claim 1, characterized in that: The metal hangers are standard A3 steel corrosion hangers.

3. The experimental method for evaluating the contribution rate of oil sludge sand to SRB according to claim 1, characterized in that: The container is a wide-mouthed bottle.

4. The experimental method for evaluating the contribution rate of oil sludge to SRB according to claim 1, characterized in that: The number of containers is 2-6.

5. The experimental method for evaluating the contribution rate of oil sludge sand to SRB according to claim 1, characterized in that: The number of containers is 5, and each container is filled with oily mud sand of different thicknesses of 0, 3, 6, 9 and 12 cm respectively.

6. The experimental method for evaluating the contribution rate of oil sludge sand to SRB according to claim 1, characterized in that: The cultivation refers to cultivation at 48-52℃ for 7-10 days.

7. The experimental method for evaluating the contribution rate of oil sludge to SRB according to claim 1, characterized in that: The average corrosion rate is calculated using the following formula:

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