Oil-water transition layer characterization method based on composition and characteristic analysis

Abstract

The invention relates to the technical field of oilfield development, in particular to an oil-water transition layer characterization method based on composition and characteristic analysis, which comprises the following steps: acquiring the water content of an oil-water transition layer; obtaining an oil phase composition of the oil-water transition layer; obtaining the solid phase composition of the oil-water transition layer; obtaining stability characteristics of the oil-water transition layer; obtaining the electric removal current and conductivity of the oil-water transition layer; the emulsification degree of the oil-water transition layer is characterized by the water content, the oil phase composition, the solid phase composition, the stability characteristic electric removal current and the conductivity. According to the method, a three-phase detection and characteristic analysis combined characterization method is adopted, and the formed characterization standard can provide a scientific guidance basis for the research direction of the treatment agent for the oil-water transition layer of the oil field.

Description

Technical Field

[0001] The present invention relates to the technical field of oilfield development, and more specifically, to a method for characterizing an oil-water transition layer based on composition and property analysis. Background Art

[0002] The oil displacement methods in each oil production plant of the Daqing Oilfield include water flooding, polymer flooding, salt-resistant polymer flooding, weak alkali ASP flooding, strong alkali ASP flooding, sodium chloride ASP flooding, and lipopeptide compounded weak alkali ASP flooding. However, the problem of electric field breakdown in the electric dehydrators has occurred in these blocks. This is because the produced fluids in each oil production plant cannot be effectively separated into oil and water in the electric dehydrator, enriching the oil-water transition layer. After the oil-water transition layer contacts the electrode plate, it conducts electricity, resulting in electric breakdown of the electrode plate and thus causing the electric field breakdown phenomenon. The frequencies of electric field breakdown in each oil production plant vary from 3 times / month to 2 times / day. In severe cases, the electric dehydrator cannot be started, and the water content of the exported oil does not meet the standard, affecting the export of crude oil. The first thing to solve this problem is to analyze the composition and properties of the oil-water transition layer and propose the research direction for the development of targeted treatment agents.

[0003] Due to the different geological conditions and oil displacement methods in the blocks, the compositions and properties of the oil-water transition layers in each block of each oil production plant are different. Currently, the analysis methods for the composition and properties of the oil-water transition layer mainly focus on studying the influence of the incoming fluid at the front end, mainly including the influence of aged oil, fracturing fluid, well flushing fluid, etc., without studying the specific composition and properties of the oil-water transition layer. There is no general analysis method, and it is difficult to enrich the solid particles in the transition layer. The existing analysis techniques cannot accurately measure the composition of the solid particles and cannot propose targeted solutions. Therefore, it is necessary to develop a general analysis method to characterize the composition and properties of the oil-water transition layer and guide the research direction of agent development based on the analysis results of the composition and properties. Summary of the Invention

[0004] In order to solve the problems existing in the above background art, the present invention adopts a three-phase detection combined with microscopic / macroscopic joint characterization method, which can provide a scientific guiding basis for the research direction of the treatment agents for the oil-water transition layer in the oilfield.

[0005] To achieve the above object, the present invention is realized through the following technical solutions:

[0006] In a first aspect of the present invention, there is provided a method for characterizing an oil-water transition layer, characterized by comprising the following steps:

[0007] Obtain the water cut of the oil-water transition layer, in %.

[0008] Obtain the oil phase composition and solid phase composition of the oil-water transition layer; wherein, the oil phase composition includes the asphaltene content, in %; the solid phase composition includes the solid particle content c in the oil-water transition layer and the FeS content, silica content, and carbonate content in the solid particles, in %.

[0009] Obtain the stability characteristics of the oil-water transition layer, and the stability characteristics include the TSI value.

[0010] Obtain the electro-desalting current and conductivity of the oil-water transition layer.

[0011] The water content of the oil-water transition layer, the asphaltene content, the solid particle content, and the stability characteristics of the oil-water transition layer characterize the emulsification degree of the oil-water transition layer; the FeS content, the silica content, and the carbonate content characterize the impurity components of the oil-water transition layer; the electro-desalting current and conductivity characterize the electro-desalting characteristics of the oil-water transition layer.

[0012] Under a preferred scheme, the detection method for the solid phase composition includes the following steps:

[0013] Enrich the solid particles in the oil-water transition layer, and use an X-ray fluorescence spectrometer to detect the content of Fe compounds, silica content, and carbonate content in the solid particles.

[0014] Use a scanning electron microscope-energy dispersive spectrometer to scan the microscopic morphology of the solid particles, detect the elemental composition of the solid particles, and then determine the FeS content based on the elemental composition in combination with the content of Fe compounds.

[0015] Under a preferred scheme, the method for enriching the solid particles includes the following steps:

[0016] Sa1. Centrifuge the oil-water transition layer and discard the upper oil phase.

[0017] Sa2. Add a mixed solution of a first organic solvent and a second organic solvent to the above product, shake and centrifuge, and then take the solid.

[0018] Sa3. Repeat step Sa2 several times until the centrifuged solution is colorless, take the solid, dry it, and obtain solid particles.

[0019] The first organic solvent is selected from petroleum ether, n-heptane, or n-hexane; the second organic solvent is selected from ethanol, ultrapure water, or methanol; the volume ratio of the first organic solvent to the second organic solvent is 1:(2 - 4).

[0020] Under a preferred scheme, the first organic solvent is petroleum ether, the second organic solvent is ethanol, and the volume ratio of petroleum ether to ethanol is 1:3.

[0021] Under the preferred scheme, the rotation speed of centrifugation in steps Sa1 to Sa3 is 10,000 - 11,000 rpm, and the time is 10 - 30 min; the temperature of shaking in step Sa2 is 40 - 55 °C, the time is 3 - 5 min, and the number of times is 30 - 60 times; the temperature of drying in step Sa3 is 80 - 100 °C, and the time is 24 - 48 h.

[0022] Under the preferred scheme, obtaining the asphaltene content includes the following steps:

[0023] Sb1. Centrifuge the oil - water transition layer, and take the upper - layer oil phase;

[0024] Sb2. Add a third organic solvent to the upper - layer oil phase and dissolve it fully;

[0025] Sb3. Filter the fully - dissolved solution with a funnel plugged with cotton, and then wash the funnel plugged with cotton with the third organic solvent until the dripping liquid is colorless;

[0026] Sb4. Wash the funnel plugged with cotton with a fourth organic solvent, collect the washing liquid, dry it, and obtain asphaltene; Asphaltene content (%) = asphaltene mass / upper - layer oil - phase mass;

[0027] The third organic solvent is selected from n - hexane, n - pentane or n - heptane; the fourth organic solvent is chloroform.

[0028] Under the preferred scheme, the rotation speed of centrifugation in step Sb1 is 10,000 - 11,000 rpm, and the time is 10 - 30 min.

[0029] In the second aspect of the present invention, an application of any of the above - mentioned oil - water transition layer characterization methods is provided.

[0030] Under the preferred scheme, the application of the oil - water transition layer characterization method is used to guide the research and development direction of oil - water transition layer treatment agents.

[0031] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0032] (1) Compared with the prior art, the oil - water transition layer composition analysis method of the present invention has a more comprehensive characterization in terms of composition and characteristics, and creatively proposes different research and development directions corresponding to different components.

[0033] (2) The method for enriching solid particles in the oil - water transition layer in the present invention is proposed for the first time, which can accurately analyze the composition of solid particles in the transition layer and provide a direction for treatment agents.

[0034] (3) The present invention can be applied to the analysis of oil - water transition layers in all development methods, and can also give the research and development direction of treatment agents according to the analysis results. Brief Description of the Drawings

[0035] Figure 1 It is a micrograph of the solid phase of the oil - water transition layer in the heavy oil water flooding of Example 1, magnified 200 times by scanning electron microscopy;

[0036] Figure 2 It is a micrograph of the solid phase of the oil - water transition layer in the heavy oil water flooding of Example 1, magnified 500 times by scanning electron microscopy;

[0037] Figure 3 It is a micrograph of the solid phase of the oil - water transition layer in the heavy oil water flooding of Example 1, magnified 1000 times by scanning electron microscopy;

[0038] Figure 4 It is a micrograph of the solid phase of the oil - water transition layer in the heavy oil water flooding of Example 1, magnified 2000 times by scanning electron microscopy;

[0039] Figure 5 It is an energy spectrum range map of the micrograph of the solid phase of the oil - water transition layer in the heavy oil water flooding of Example 1, magnified 2000 times by scanning electron microscopy;

[0040] Figure 6 It is a surface scan map of the solid phase energy spectrum of the oil - water transition layer in the heavy oil water flooding of Example 1;

[0041] Figure 7 It is an elemental energy spectrum map of the solid phase of the oil - water transition layer in the heavy oil water flooding of Example 1;

[0042] Figure 8 It is a micrograph of the oil - water transition layer in the heavy oil water flooding of Example 1 under natural light;

[0043] Figure 9 It is a micrograph of the oil - water transition layer in the heavy oil water flooding of Example 1 under fluorescence;

[0044] Figure 10 It is a multi - light separation characteristic map of the oil - water transition layer in the heavy oil water flooding of Example 1;

[0045] Figure 11 It is a TSI value map of the oil - water transition layer in the heavy oil water flooding of Example 1;

[0046] Figure 12 It is an electro - desalting characteristic map of the oil - water transition layer in the heavy oil water flooding of Example 1;

[0047] Figure 13 It is a graph of current and voltage of the oil - water transition layer after adding chemicals in Example 1. Detailed Description of the Invention

[0048] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the protection scope of the present invention.

[0049] The experimental methods in the embodiments are all conventional methods unless otherwise specified. For those without specific conditions noted in the embodiments, they are carried out according to the conventional conditions or the conditions recommended by the manufacturer. The reagents or instruments without the manufacturer indicated are all conventional products that can be obtained through commercial purchase.

[0050] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by those skilled in the technical field to which this application belongs; the terms used herein are only for the purpose of describing specific embodiments and are not intended to limit this application; the term "including" and any variations thereof in the specification and claims of this application and the above drawings are intended to cover non-exclusive inclusion.

[0051] In the description of the embodiments of the present invention, technical terms such as "first" and "second" are only used to distinguish different objects and cannot be understood as indicating or implying relative importance or implicitly indicating the quantity, specific order or primary-secondary relationship of the indicated technical features.

[0052] The present invention adopts a method of jointly characterizing three-phase detection and emulsification characteristics, which includes both the composition of the transition layer and the emulsification characteristics of the transition layer. It is more comprehensive and scientific than the existing analysis methods, separately detecting the composition of the oil phase and the solid phase, and detecting the microscopic image, stability and electric desalting current of the transition layer. Combining the oil phase composition, microscopic image and stability to clarify the emulsification degree of the transition layer, and combining the solid phase analysis and electric desalting current to clarify the conductivity and conductive particles of the transition layer, which can provide a research and development direction for the treatment agent.

[0053] The characterization method of the oil-water transition layer based on composition and property analysis includes: detecting the water content of the oil-water transition layer; the oil phase composition of the oil-water transition layer; the enrichment and composition of solid particles in the oil-water transition layer; the scanning electron microscopy and energy spectrum of the oil-water transition layer; the stability characterization of the oil-water transition layer; the electric desalting current and conductivity of the oil-water transition layer. The treatment of the oil-water transition layer needs to take "interface film destruction - conductivity inhibition - particle dispersion" as the synergistic goal, and guide the research and development of the agent through multi-parameter linkage analysis.

[0054] Specifically, a method for characterizing an oil-water transition layer includes the following steps:

[0055] Obtain the water content of the oil-water transition layer, in %;

[0056] Obtain the oil-phase composition and solid-phase composition of the oil-water transition layer; wherein, the oil-phase composition includes the asphaltene content in %, and the solid-phase composition includes the solid particle content in the oil-water transition layer, as well as the FeS content, silica content, and carbonate content in the solid particles in %,

[0057] Obtain the stability characteristics of the oil-water transition layer, and the stability characteristics include the TSI value;

[0058] Obtain the electro-dehydration current and conductivity of the oil-water transition layer;

[0059] The water content of the oil-water transition layer, the asphaltene content, the solid particle content, and the stability characteristics of the oil-water transition layer characterize the emulsification degree of the oil-water transition layer; the FeS content, the silica content, and the carbonate content characterize the impurity components of the oil-water transition layer; the electro-dehydration current and conductivity characterize the electro-dehydration characteristics of the oil-water transition layer.

[0060] Wherein, the solid particle content = the mass of solid particles / the mass of the oil-water transition layer; the FeS content = the mass of FeS / the mass of solid particles; the silica content = the mass of silica / the mass of solid particles; the carbonate content = the mass of carbonate / the mass of solid particles.

[0061] The detection method of the solid-phase composition includes the following steps:

[0062] Enrich the solid particles in the oil-water transition layer, and use an X-ray fluorescence spectrometer to detect the content of Fe compounds, silica content, and carbonate content in the solid particles;

[0063] Use a scanning electron microscope-energy spectrometer to scan the microscopic morphology of the solid particles, detect the elemental composition of the solid particles, and then determine the FeS content based on the elemental composition in combination with the content of Fe compounds.

[0064] The enrichment method of solid particles includes the following steps:

[0065] Sa1. Centrifuge the oil-water transition layer and discard the upper oil phase;

[0066] Sa2. Add a mixed solution of a first organic solvent and a second organic solvent to the above product, shake and centrifuge, and then take the solid;

[0067] Sa3. Repeat step Sa2 several times until the centrifuged solution is colorless, take the solid, dry it, and obtain solid particles;

[0068] The first organic solvent is selected from petroleum ether, n-heptane or n-hexane; the second organic solvent is selected from ethanol, ultrapure water or methanol; the volume ratio of the first organic solvent to the second organic solvent is 1:(2-4).

[0069] The first organic solvent is petroleum ether, the second organic solvent is ethanol, and the volume ratio of petroleum ether to ethanol is 1:3.

[0070] The rotation speed of the centrifugation in steps Sa1 to Sa3 is 10000-11000 rpm, and the time is 10-30 min; the temperature of the shaking in step Sa2 is 40-55 °C, the time is 3-5 min, and the number of times is 30-60 times; the temperature of the drying in step Sa3 is 80-100 °C, and the time is 24-48 h.

[0071] Obtaining the asphaltene content includes the following steps:

[0072] Sb1. Centrifuge the oil-water transition layer and take the upper oil phase.

[0073] Sb2. Add a third organic solvent to the upper oil phase and dissolve it fully.

[0074] Sb3. Filter the fully dissolved solution with a funnel plugged with cotton, and then wash the funnel plugged with cotton with the third organic solvent until the dripping liquid is colorless.

[0075] Sb4. Wash the funnel plugged with cotton with a fourth organic solvent, collect the washing solution, dry it, and obtain asphaltene; the asphaltene content (%) = asphaltene mass / upper oil phase mass.

[0076] The third organic solvent is selected from n-hexane, n-pentane or n-heptane; the fourth organic solvent is chloroform.

[0077] In step Sb1, the rotation speed of the centrifugation is 10000-11000 rpm, and the time is 10-30 min.

[0078] In the above data, the water content, asphaltene content, impurity content (solid particle content) and stability can characterize the emulsification degree of the oil-water transition layer. When the water content > 30%, and the TSI value < 1, it can indicate that the emulsification degree is serious and a demulsifier needs to be added. When the asphaltene content > 1%, a demulsifier containing sulfonic acid group, block polyether, phenolic resin polyether needs to be added. When the impurity content > 1%, specific agents are added according to the solid particle composition. For the treatment of high carbonate, the direction is to select chelating agents such as disodium EDTA, etc., to complex Fe2+, Ca 2+; The treatment direction for high iron sulfide is to select a sulfide remover, and the treatment direction for high silica is to add a surface modifier such as a silane coupling agent. The solid particle composition and scanning electron microscopy energy spectrum can characterize the specific components of the impurities; the solid particle composition can determine the proportions of SiO2, CaCO3, and iron compounds, and the scanning electron microscopy can analyze whether the iron compound contains FeS. Combining the solid particle composition and the scanning electron microscopy results can determine the proportions of the main components in the solid particles, and corresponding chemicals can be added according to the components.

[0079] The electric desalting current and conductivity can characterize the electric desalting characteristics of the oil-water transition layer. When the electric desalting current > 2A, it indicates that as the electric desalting experiment progresses, a large current will generate heat, which will cause the oil-water transition layer to boil and bubble, resulting in the breakdown of the electric field in the electric dehydrator. In severe cases, the current > 10A, and the electrodes of the electric dehydrator will be short-circuited and broken down, and the equipment will report a fault. When the current < 2A, the electric dehydrator operates stably during the 1h electric desalting experiment, and there will be no oil boiling phenomenon; when the conductivity is as high as 10 -6 μS / m, the conductivity of the oil-water transition layer is strong, and the current will increase during the electric desalting experiment, and the electric dehydrator will short-circuit and the electric field will break down. When the conductivity is lower than 10 -9 μS / m, the current is stable during the electric desalting process and will not be higher than 2A. The treatment direction for high electric desalting current and conductivity is to select a charge neutralizer. According to different compositions and characteristics, the treatment of the oil-water transition layer is divided into multiple directions, as shown in Table 1:

[0080]

[0081] A means the water content > 30%, TSI < 1, asphaltene > 1%, solid particles < 1%, electric desalting current < 2A, conductivity < 10 -9 μS / m, indicating that the reason for the serious emulsification of the transition layer is asphaltene, and the content of solid particles is low. There is no need to add chemicals to treat solid particles, and the low electric desalting current and low conductivity will not cause the breakdown of the electric field in the electric dehydrator, so there is no need to add a charge neutralizer. Therefore, with the core of treating asphaltene to reduce the water content, a demulsifier containing sulfonic acid group, block polyether, and phenolic resin polyether is added.

[0082] B means the water content > 30%, TSI < 1, asphaltene < 1%, solid particles > 1%, electric desalting current > 2A, conductivity > 10 -6 μS / m, and the solid particles are mainly carbonates. Add a chelating agent and a charge neutralizer.

[0083] C means the water content > 30%, TSI < 1, asphaltene < 1%, solid particles > 1%, electric desalting current > 2A, conductivity > 10 -6 μS / m, and the solid particles are mainly silica. Add a surface modifier and a charge neutralizer.

[0084] D has a water content > 30%, TSI < 1, asphaltene < 1%, solid particles > 1%, electro - desalting current > 2A, conductivity > 10 -6 μS / m, the solid particles are mainly ferrous sulfide, and a sulfide remover and a charge neutralizer are added.

[0085] E has a water content > 30%, TSI < 1, asphaltene > 1%, solid particles > 1%, electro - desalting current > 2A, conductivity > 10 -6 μS / m, the solid particles are mainly ferrous sulfide, and a demulsifier containing sulfonic acid group, block polyether, phenolic resin polyether, a sulfide remover and a charge neutralizer are added.

[0086] F has a water content > 30%, TSI < 1, asphaltene > 1%, solid particles > 1%, electro - desalting current > 2A, conductivity > 10 -6 μS / m, the solid particles are mainly silica, and a surface modifier, a charge neutralizer and a demulsifier containing sulfonic acid group, block polyether, phenolic resin polyether are added.

[0087] G has a water content > 30%, TSI < 1, asphaltene > 1%, solid particles > 1%, electro - desalting current > 2A, conductivity > 10 -6 μS / m, the solid particles are mainly carbonate, and a chelating agent, a charge neutralizer and a demulsifier containing sulfonic acid group, block polyether, phenolic resin polyether are added.

[0088] I has a water content > 30%, TSI < 1, asphaltene > 1%, solid particles > 1%, electro - desalting current > 2A, conductivity > 10 -6 μS / m, the solid particles are silica and calcium carbonate, and a surface modifier, a charge neutralizer, a chelating agent and a demulsifier containing sulfonic acid group, block polyether, phenolic resin polyether are added.

[0089] Among them, when the proportion of a certain target compound (silica, ferrous sulfide, and carbonate) in the solid particles is more than 10%, it is regarded as the main compound, and drugs need to be added for treatment according to this compound.

[0090] The present invention will take the oil - water transition layer of the heavy - oil water - flooding block in Daqing Oilfield as an example, use the scheme of the present invention to characterize the oil - water transition layer, and guide the use of treatment agents according to the characterization standard formed by the above - mentioned characterization results.

[0091] The microscopic morphology of the oil - water transition layer of the heavy - oil water - flooding block is obtained. Dip the oil - water transition layer on a glass slide, place a coverslip for pressing, observe the microscopic morphology of the transition layer using a microscope, observe respectively under natural light and fluorescence, compare the results under natural light and fluorescence, check whether there are black solid particles, whether there are micelles, and observe the morphology of the oil - water interface, so as to analyze the emulsification situation of the oil - water transition layer.

[0092] The microscopic morphology of the oil-water transition layer is as follows: Figures 8 - 9 As shown, Figure 8 This is a microscopic morphology of the oil-water transition layer of heavy oil under natural light. The oil phase is yellow, the water phase is round, and the black ones are opaque particles or micelles. Figure 9 This is a microscopic morphology of the oil-water transition layer of heavy oil under fluorescence. The oil phase is green, the water phase and solid particles are black. Figure 8 and 9 It can be distinguished that there are oil phase, a large number of water droplets, flocs and solid particles in the picture, and the interface is not clear, which shows that the emulsification is very serious.

[0093] The composition and characteristics of the oil-water transition layer in the heavy oil water drive block will be analyzed using the method of the present invention.

[0094] Example 1: Composition and characteristics analysis of the oil-water transition layer in a heavy oil water flooding block

[0095] The composition and characteristic analysis method of the oil-water transition layer comprises the following steps:

[0096] Step 1: Obtain the water content of the oil-water transition layer:

[0097] The water content of the transition layer is tested by distillation. 10g of the transition layer is placed in a distillation bottle. After 1 hour of distillation, the amount of water produced is recorded. The water content of the transition layer is the water content of the transition layer. A water content exceeding 30% will lead to severe emulsification and increased conductivity.

[0098] Step 2: Obtain the oil phase composition of the oil-water transition layer:

[0099] The asphaltene and oil phase impurity content of the transition layer oil phase is tested with reference to the petroleum industry standard "SY / T5119-2008 Analysis of Soluble Organic Matter in Rocks and Crude Oil Group Components". High asphaltene content will lead to severe emulsification, and high oil phase impurity content will lead to severe emulsification and enhanced conductivity.

[0100] Wherein, obtaining the asphaltene content includes the following steps:

[0101] Sb1. The oil-water transition layer was centrifuged to take the upper oil phase;

[0102] Sb2. A third organic solvent is added to the upper oil phase to fully dissolve;

[0103] Sb3. The fully dissolved solution was filtered using a funnel plugged with cotton, and then the funnel plugged with cotton was cleaned with the third organic solvent until the dripping liquid was colorless;

[0104] Sb4. The cotton plugged funnel is cleaned with a fourth organic solvent, the cleaning solution is taken, and the asphaltene is dried to obtain asphaltene; asphaltene content (%) = asphaltene mass / upper oil phase mass;

[0105] The third organic solvent is selected from n - hexane, n - pentane or n - heptane; the fourth organic solvent is chloroform.

[0106] Step three: Obtain the solid composition of the oil - water transition layer:

[0107] Enrich the solid particles in the oil - water transition layer, including the following steps:

[0108] The enrichment of solid particles includes taking the transition layer and centrifuging it at 11000 rpm. Take the lower - layer solid particles and 1 g of the middle - layer in the centrifuge tube (if there is no middle - layer, just take the lower - layer solid particles). Add 10 mL of petroleum ether and ethanol (petroleum ether:ethanol = 1:3), shake it up and down for 1 min to fully mix the solvent and the solid particles. Centrifuge this liquid again, take the lower - layer solid particles (at this time, the oil content is extremely low and there is no middle - layer), add petroleum ether and ethanol again, and repeat the above steps until the ethanol and petroleum ether have no color. Take the solid particles and dry them at 80 °C for 24 h for standby.

[0109] Step four: Obtain the contents of FeS, aluminosilicate and carbonate in the solid particles:

[0110] (1) Obtain the contents of Fe compounds, silicon dioxide and carbonate in the solid particles:

[0111] Take the solid particles and use an X - ray fluorescence spectrometer to detect the specific composition of the solid particles. Accurate results can be obtained according to the instrument standard. Select different treatment agents for aluminosilicate, Fe compounds and carbonate in the solid particles.

[0112] (2) Obtain the content of FeS in the solid particles:

[0113] Use the scanning electron microscope and energy spectrum of the oil - water transition layer. Place the solid particles prepared in step three on the conductive adhesive, observe the microscopic morphology of the solid particles using the scanning electron microscope, and detect the elemental composition of the solid particles using the energy spectrum. Analyze whether the Fe compound in the solid particles is FeS, and then determine the FeS content in combination with the content of Fe compounds in step (1), so as to give the selection direction of treatment agents.

[0114] Step five: Obtain the stability characteristics of the oil - water transition layer:

[0115] Take 20 mL of the oil - water transition layer and place it in a bottle. Use a Turbiscan stability analyzer to detect the transition layer. The experimental temperature is 55 °C, the experimental time is 3 h, and the scattering frequency is once every 2 min. The transmitted light, scattered light and TSI values can be used to analyze the stability of the transition layer.

[0116] Step six: Obtain the electric desalting current and conductivity of the oil - water transition layer:

[0117] Take 300 mL of the oil-water transition layer and place it in an electro-deoiling tank. Set the electro-deoiling parameters as follows: voltage 1 kV / cm, frequency 0.35 kHz, current upper limit 10 A, duty cycle 35%. Use the KRPS2020 type crude oil electro-dehydration control device to detect the electro-deoiling current and conductivity of the original transition layer. Analyze the electro-deoiling effectiveness of the transition layer through the current and conductivity to determine whether to add current-reducing agents. When the current > 2 A and the conductivity > 10 -6 μS / m, add a charge neutralizer.

[0118] Analyze the composition and characteristics of the heavy oil-water transition layer through the above method. The test results are as follows:

[0119] (1) Detect the water content of the heavy oil-water transition layer, which is as high as 55.98%, and the emulsification is very serious;

[0120] (2) Detect the asphaltene and impurities in the oil phase of the heavy oil-water transition layer. The asphaltene content is 5.66%, and the oil phase impurity content is 7.38%. The asphaltene and impurity contents are extremely high;

[0121] (3) Since the heavy oil block is water-flooded, no polymers and surfactants are detected;

[0122] (4) The composition of solid particles in the oil-water transition layer is shown in Table 2. It can be seen that the SiO2 content is 36.91%, the Al2O3 content is 16.29%, and the iron compound is 27.81%. The main composition of solid particles is aluminosilicate and iron compounds. The specific composition of the iron compound needs to be determined in combination with the scanning electron microscope results.

[0123] Table 2 Solid particle components of the heavy oil transition layer

[0124]

[0125] (5) The scanning electron microscope results of solid particles in the oil-water transition layer are as Figures 1 - 7 shown in Table 3. In the solid particles, the Si element accounts for 12.95%, the Al element accounts for 4.42%, the Na element accounts for 0.87%, and the O element accounts for 32.09%. This indicates the presence of aluminosilicate; the Fe element on the solid particles accounts for 11.90%, and the S element accounts for 3.51%, indicating the presence of FeS; the Ca element content on the solid particles accounts for 2.24%, and the Ba element content accounts for 0.40%. This indicates the presence of carbonate. SiO2 and FeS are dominant among the three substances.

[0126] Table 3 Energy spectrum element composition of solid particles in the heavy oil transition layer

[0127]

[0128] (6) The stability characteristics of the oil-water transition layer are asFigure 10 and 11 As shown, the position from 1 mm to 40 mm is from the bottom to the top of the sample bottle, which is the oil-water transition layer. During the experiment, the transmitted light (T) is always 0, indicating that there is no water layer in the bottle and it is opaque; at the beginning of the experiment, the BS of the oil-water transition layer is 1.5, indicating that the water droplets in the oil-water transition layer of the sample bottle are evenly distributed. As the experiment progresses, the BS value starts to decrease at 24 mm, indicating that the upper-layer droplets move downward, the upper-layer droplets decrease, and the backscattered light intensity decreases. From Figure 11 it can be seen that the maximum value of TSI during the experiment is 0.5. The smaller the value, the more stable the transition layer and the greater the difficulty of oil-water separation. Combining the spectrogram and the TSI numerical results, it can be known that no oil-water separation phenomenon occurred after the oil-water transition layer was statically settled at 55 °C for 3 h. The small TSI value indicates that the emulsification is relatively serious and the oil and water cannot be effectively separated under thermal static settlement.

[0129] (7) The electro-dehydration current of the oil-water transition layer is as Figure 12 shown. After 1 minute of electro-dehydration, the current gradually rises to 10 A and the voltage gradually rises to 0.8 kV. At 2 minutes, the phenomenon of oil bubbling appears. At 5 minutes, the oil boils and overflows, causing the breakdown of the electric field. The conductivity of the transition layer is 8.325×10 -7 S / m. The conductivity of the imported samples of the electro-dehydrator in Daqing Oilfield is generally 0.35×10 -11 S / m. The conductivity of the samples at the peak of the chemical agent returning reached 2.68×10 -11 S / m. However, the conductivity of the oil-water transition layer at this station is as high as 10 -7 S / m. With strong conductivity and high current, the voltage between the electrodes of the electro-dehydrator is low, and the electro-dehydration effect is poor and normal dehydration cannot be carried out.

[0130] (8) At present, there is no clear analysis method and treatment method for the heavy oil transition layer. According to the characterization means provided by the present invention and the comprehensive analysis of all aspects of the present invention, the water content of the heavy oil-water transition layer is as high as 55.98%, the asphaltene content is 5.66%, the impurity content is 7.38%, it does not contain polymers and surfactants, the main components of the solid particles are SiO2 and FeS, the maximum value of TSI is 0.5, no oil-water separation phenomenon occurred after static settlement at 55 °C for 3 h, the electro-dehydration current reached 10 A, and the conductivity was as high as 8.325×10 -7 S / m; the high water content, asphaltene and impurities in the heavy oil-water transition layer result in a very high degree of emulsification, and oil-water separation cannot be carried out by conventional heating means. It is necessary to add surface modifiers, sulfide removers, charge neutralizers and demulsifiers containing sulfonic acid groups, block polyethers, and phenolic resin polyethers.

[0131] (9)Treatment solution for heavy oil transition layer provided by the present invention: adding a surface modifier, a sulfide remover, a charge neutralizer, and a demulsifier containing sulfonic acid group, block polyether, and phenolic resin polyether. After adding the agents, the current, as shown in Figure 13 , drops from 10 A to below 2 A. The electro-dehydration process is stable, without the phenomena of increased current and collapsed electric field. After electro-dehydration, the water content in the upper-layer oil drops to 0.3%. It can effectively solve the problem of collapsed electric field in the electro-dehydrator of the heavy oil block in the oilfield.

[0132] As mentioned above, it is only the preferred specific implementation manner of the present invention, but the protection scope of the present invention is not limited thereto. Any person skilled in the art within the technical scope disclosed by the present invention, according to the technical solution and inventive concept of the present invention, makes equivalent substitutions or changes, and should be covered within the protection scope of the present invention.

Claims

1. A method for characterizing an oil-water transition layer, characterized in that: The steps include: Get the water content of the oil-water transition layer, unit: %; Obtaining the oil phase composition and solid phase composition of the oil-water transition layer; wherein the oil phase composition includes the asphaltene content, in %, and the solid phase composition includes the solid particle content in the oil-water transition layer and the FeS content, silica content, and carbonate content in the solid particles, in %. Obtaining stability characteristics of the oil-water transition layer, wherein the stability characteristics include a TSI value; Obtaining the electrical desorption current and electrical conductivity of the oil-water transition layer; The water content of the oil-water transition layer, the asphaltene content, the solid particle content, and the stability characteristics of the oil-water transition layer characterize the emulsification degree of the oil-water transition layer; the FeS content, the silica content, and the carbonate content characterize the impurity components of the oil-water transition layer; the electro-desorption current and conductivity characterize the electro-desorption characteristics of the oil-water transition layer.

2. The method for characterizing the oil-water transition layer according to claim 1, characterized in that: The method for detecting the solid phase composition comprises the following steps: Enriching the solid particles in the oil-water transition layer, and detecting the Fe compound content, silicon dioxide content and carbonate content in the solid particles by using an X-ray fluorescence spectrometer; The microscopic morphology of the solid particles is scanned by a scanning electron microscope-energy spectrometer to detect the elemental composition of the solid particles, and then the FeS content is determined based on the elemental composition combined with the content of Fe compounds.

3. The method for characterizing the oil-water transition layer according to claim 1 or 2, characterized in that: The solid particle enrichment method comprises the following steps: Sa1. The oil-water transition layer is centrifuged and the upper oil phase is discarded; Sa2. A mixed solution of a first organic solvent and a second organic solvent was added to the above product, shaken, centrifuged, and the solid was taken; Sa3 repeat step Sa2 several times until the solution after centrifugation is colorless, take the solid, dry it, and obtain solid particles; The first organic solvent is selected from petroleum ether, n-heptane or n-hexane; the second organic solvent is selected from ethanol, ultrapure water or methanol; the volume ratio of the first organic solvent to the second organic solvent is 1:(2-4).

4. The method for characterizing the oil-water transition layer according to claim 3, characterized in that: The first organic solvent is petroleum ether, the second organic solvent is ethanol, and the volume ratio of petroleum ether to ethanol is 1:

3.

5. The method for characterizing the oil-water transition layer according to claim 3, characterized in that: The centrifugal speed in steps Sa1 to Sa3 is 10000-11000 rpm, and the time is 10-30 min; the shaking temperature in step Sa2 is 40-55°C, the time is 3-5 min, and the number of times is 30-60 times; the drying temperature in step Sa3 is 80-100°C, and the time is 24-48 h.

6. The method for characterizing the oil-water transition layer according to claim 1, characterized in that: Obtaining the asphaltene content comprises the following steps: Sb1. The oil-water transition layer was centrifuged to take the upper oil phase; Sb2. A third organic solvent is added to the upper oil phase to fully dissolve; Sb3. The fully dissolved solution was filtered using a funnel plugged with cotton, and then the funnel plugged with cotton was cleaned with the third organic solvent until the dripping liquid was colorless; Sb4. The cotton plugged funnel is cleaned with a fourth organic solvent, the cleaning solution is taken, and the asphaltene is dried to obtain asphaltene; asphaltene content (%) = asphaltene mass / upper oil phase mass; The third organic solvent is selected from n-hexane, n-pentane or n-heptane; and the fourth organic solvent is chloroform.

7. The method for characterizing the oil-water transition layer according to claim 6, characterized in that: The centrifugal speed in step Sb1 is 10000-11000 rpm, and the time is 10-30 min.

8. Use of the method for characterizing the oil-water transition layer according to any one of claims 1 to 7.

9. Application of the method for characterizing the oil-water transition layer according to claim 8, characterized in that: Used to guide the research and development direction of oil-water transition layer treatment agents.

Images