Multi-index comprehensive evaluation method for difficulty of demulsification of crude oil emulsion

Abstract

The present application relates to the oil field chemical technology field, specifically relates to a kind of crude oil emulsion demulsification difficulty degree's multi-index comprehensive evaluation method.The method includes the following steps: the content of high valence metal ion in sample is determined, the high valence metal ion influence parameter value is calculated;The surface tension of sample is determined;According to the high valence metal ion influence parameter value and surface tension obtained comprehensive judgment the crude oil emulsion sample demulsification difficulty degree.This method can more accurately, quickly screen and evaluate the crude oil emulsion demulsification difficulty degree, can effectively guide the production process of crude oil emulsion demulsification, reduce operating cost.

Description

Technical Field

[0001] This invention relates to the field of oilfield chemical technology, specifically to a multi-index comprehensive evaluation method for the ease of demulsification of crude oil emulsions. Background Technology

[0002] During water injection extraction in oilfields, shearing and agitation during the flow process cause droplets to disperse into the oil phase, forming an oil-water emulsion. Asphaltenes, high-melting-point waxes, and other high-molecular-weight organic compounds in crude oil, as well as solids such as sand and clay, and small molecules such as fatty acids and naphthenic acids, can all act as emulsifiers to form an oil-water interface film, giving the emulsion a certain degree of stability. Reducing the stability of the oil-water interface film and promoting droplet coalescence are key to demulsification.

[0003] Electrodesalting is a commonly used method for demulsifying crude oil. Under the influence of an applied electric field, the surface of the emulsion droplets also carries a charge. This causes the droplet movement direction to continuously change with the electric field, leading to droplet aggregation along the direction of the electric field and achieving oil-water separation. During electrodesalting, a certain amount of demulsifier is often added to the crude oil emulsion to disrupt the interfacial film. Demulsifiers are mostly surfactants, and there are many types, mainly including alkyl sulfonates, alkylbenzene sulfonates, fatty acid salts, and high-molecular-weight demulsifiers such as polyethers and polyacrylates. Some metal ions in the aqueous phase, especially high-valence metal ions, can interact with ionic surfactants, changing their hydrophilicity and lipophilicity, thereby altering the demulsifying effect of the demulsifier.

[0004] Currently, with the promotion of tertiary oil recovery technology in oilfields, the types of oil recovery agents are numerous and the amounts added are increasing. Residual surfactants, especially ionic surfactants, remain in the recovered crude oil emulsion. These surfactants react with high-valence metal ions in the water sample, altering the oil-to-hydrophilic properties, changing the oil-soluble nature from water-soluble to oil-soluble. This makes demulsification of W / O type crude oil emulsions increasingly difficult, leading to increased demulsification costs. Therefore, a preliminary assessment of the ease of demulsification of the recovered crude oil emulsion is necessary before demulsification. A common method for determining the ease of demulsification is to measure the dehydration rate of the crude oil emulsion after standing for a period of time. CN114076782A relates to a method for characterizing the stability of crude oil emulsions by measuring the conductivity values ​​at a certain location in the upper and lower layers of the sample. The method includes: measuring the conductivity values ​​at a certain location in the upper and lower layers of the sample respectively; under the same frequency conditions, the smaller the difference in conductivity values ​​between the upper and lower layers, the more stable the sample. The device includes a sample tube clamp, a sample tube, two conductivity meters, a constant temperature circulating water bath, and two electrodes. The sample tube is placed in the sample tube clamp, which is connected to the constant temperature circulating water bath. The two electrodes are placed at the upper and lower ends of the sample tube, respectively, and the two conductivity meters are connected to the terminals of the two electrodes. This patent mainly characterizes emulsion stability by measuring conductivity. However, this method only reflects the situation at the measured point and cannot represent the average condition of the entire sample. CN 104877706 A and CN 105273200 A mainly disclose a demulsifier, and the stability evaluation method of the crude oil emulsion involved therein is also characterized by the water removal rate. This is a commonly used method, but it also suffers from the problem that the sample taken is not representative; or after the samples from various points are mixed, the measured water content is an average value and cannot identify the highest water content and the severity of emulsification. Chinese patent CN 105273200 A discloses a method for characterizing the flowability of specific components in an emulsion. First, a lysine slide with a grid-like structure is prepared. Individual emulsion molecules are mixed with a fluorescent probe and immobilized. Then, a laser confocal microscope is used to acquire images and data of the fluorescence recovery of the specific components after bleaching. The flowability of different specific components is analyzed by comparing the calculated time when fluorescence recovers to half of its final stable value, the diffusion coefficient, and the proportion of dynamic molecules. This patent primarily characterizes the flowability of specific components in an emulsion and has little to do with the characterization of emulsion stability. The article "Latest Preparation Technology and Related Evaluation Methods for Crude Oil Emulsions" discusses methods for characterizing the stability of crude oil emulsions, including static observation evaluation, emulsification rate evaluation, microscopic particle size distribution evaluation, resistivity evaluation, and demulsification voltage evaluation. These measurement methods are complex. Furthermore, all of these methods only reflect the stability of the crude oil emulsion and do not reflect the factors affecting the stability of the emulsion.

[0005] Due to significant differences in the inherent properties of crude oil systems across different oilfields, different reservoir types within the same oilfield, and different blocks within the same reservoir type, as well as the varying types and amounts of production agents used in different wells and the substantial differences in formation water across different oilfields, characterizing the stability of crude oil emulsions is challenging, and existing characterization methods are not applicable. Therefore, there is an urgent need for a multi-index comprehensive evaluation method for the ease of demulsification of crude oil emulsions. This method should objectively and accurately reflect the degree of emulsification in crude oil emulsions and provide early warnings before the crude oil emulsion enters the electrostatic precipitator at the combined demulsification station, thereby reducing alarm malfunctions in the electrostatic precipitator. Simultaneously, this method must be easy to operate, and the instruments and equipment used should be conventional and widely available. Summary of the Invention

[0006] The main objective of this invention is to provide a multi-index comprehensive evaluation method for the ease of demulsification of crude oil emulsions. This method can more accurately and quickly screen and evaluate the ease of demulsification of crude oil emulsions, effectively guide the production process of crude oil emulsion demulsification, and reduce operating costs.

[0007] To achieve the above objectives, the present invention adopts the following technical solution:

[0008] This invention provides a multi-index comprehensive evaluation method for the ease of demulsification of crude oil emulsions, the method comprising the following steps:

[0009] The ease of demulsification of the crude oil emulsion sample is determined by comprehensively considering the obtained values ​​of the influence parameters of high-valence metal ions and surface tension.

[0010] Furthermore, when the obtained high-valence metal ion influence parameter value is ≥84mmol / kg and the surface tension is <45mN / m, the crude oil emulsion sample is difficult to demulsify.

[0011] Furthermore, when the obtained high-valence metal ion influence parameter value is <84mmol / kg or the surface tension is ≥45mN / m, the crude oil emulsion sample is prone to demulsification.

[0012] This invention, through extensive experimental research, has found that crude oil emulsions are difficult to demulsify when the influence parameter of high-valence metal ions is ≥84 mmol / kg and the surface tension is <45 mN / m. Conversely, crude oil emulsion samples are easily demulsified when the obtained influence parameter value of high-valence metal ions is <84 mmol / kg or the surface tension is ≥45 mN / m.

[0013] Furthermore, the influence parameters of the high-valence metal ions are expressed by the following formula:

[0014]

[0015] Where m B Z represents the molality of high-valence metal ions B in the sample, in mmol / kg. BThis indicates the valence number of the high-valence metal ion B in the sample.

[0016] Compared with the prior art, the present invention has the following advantages:

[0017] This invention uses two parameters, high-valence metal ion content and surface tension, to comprehensively measure and judge the ease of demulsification of crude oil emulsions. The results are more accurate and reliable, and the operation steps are simple, making it widely applicable and practical. Detailed Implementation

[0018] It should be noted that the following detailed descriptions are exemplary and intended to provide further illustration of the invention. Unless otherwise specified, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains.

[0019] It should be noted that the terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the exemplary embodiments of the present invention. As used herein, the singular form is intended to include the plural form as well, unless the context clearly indicates otherwise. Furthermore, it should be understood that when the terms "comprising" and / or "including" are used in this specification, they indicate the presence of features, steps, operations, and / or combinations thereof.

[0020] To address the problems described in the background art, this invention provides a multi-index comprehensive evaluation method for the ease of demulsification of crude oil emulsions, the method comprising the following steps:

[0021] The content of high-valence metal ions in the sample was determined, and the influence parameters of the high-valence metal ions were calculated; the surface tension of the sample was also determined.

[0022] The ease of demulsification of the crude oil emulsion sample is determined by comprehensively considering the obtained values ​​of the influence parameters of high-valence metal ions and surface tension.

[0023] As a preferred embodiment of the present invention, when the obtained high-valence metal ion influence parameter value is ≥84mmol / kg and the surface tension is <45mN / m, the crude oil emulsion sample is difficult to demulsify.

[0024] As a preferred embodiment of the present invention, when the obtained high-valence metal ion influence parameter value is <84mmol / kg or the surface tension is ≥45mN / m, the crude oil emulsion sample is prone to demulsification.

[0025] In a preferred embodiment of the present invention, the influence parameter of high-valence metal ions is expressed by the following formula:

[0026]

[0027] Where m BZ represents the molality of high-valence metal ions B in the sample, in mmol / kg. B This indicates the valence number of the high-valence metal ion B in the sample.

[0028] In a preferred embodiment of the present invention, the high-valence metallic ion has a valence greater than 1.

[0029] As a preferred embodiment of the present invention, the content of high-valence metal ions in the sample is determined by atomic absorption spectrometry.

[0030] As a preferred embodiment of the present invention, the surface tension of the sample at 20-25°C is determined by the hanging plate method.

[0031] To enable those skilled in the art to better understand the technical solution of the present invention, the technical solution of the present invention will be described in detail below with reference to specific embodiments.

[0032] In the following embodiments of the present invention, the method for determining the content of high-valence metal ions in a sample by atomic absorption spectrometry and the method for determining the surface tension of a sample by the pendant method are existing conventional techniques.

[0033] Example 1

[0034] A multi-index comprehensive evaluation method for the ease of demulsification of crude oil emulsions, taking Shengli Oilfield sample 1 as an example, the method includes the following steps:

[0035] Step 1. The content of high-valence metal ions in the sample was determined by atomic absorption spectrometry. The obtained contents are shown in Table 1 below.

[0036] Table 1. Content of high-valent cations in Sample 1 from Shengli Oilfield

[0037]

[0038] Step 2. Calculate the influence parameter M of high-valence metal ions:

[0039]

[0040] Where m B Z represents the molality of high-valence metal ions B in the sample, in mmol / kg. B This indicates the valence number of the high-valence metal ion B in the sample.

[0041] The obtained M value was 87 mmol / kg.

[0042] Step 3. The surface tension of sample 1 at 25℃ was measured to be 36.7 mN / m using the pendant method.

[0043] Step 4. By comparing the M value and surface tension value of sample 1 with the threshold values ​​of the high-valence metal ion influence parameter M and surface tension, respectively, it can be seen that the obtained M value is >84mmol / kg and the surface tension is <45mN / m. Therefore, the sample is judged to be a difficult-to-demulsify sample.

[0044] The conventional dehydration rate method was used for verification: Sample 1 was placed in a 50mL glass graduated tube and left to stand in a 50℃ constant temperature water bath for 1 hour. The volume of water precipitated from the lower layer was observed, and the dehydration rate (the ratio of the volume of precipitated water to the total volume of water in the emulsion) was calculated. The calculated dehydration rate of the emulsion within 1 hour was 10%, which is far lower than the industry standard (80% dehydration rate within 1 hour). Therefore, Sample 1 is a difficult-to-demulsify sample. Thus, the results obtained using the conventional dehydration rate method are consistent with those of this embodiment, and the method in this patent is feasible.

[0045] Example 2

[0046] A multi-index comprehensive evaluation method for the ease of demulsification of crude oil emulsions, taking sample 2 from Shengli Oilfield as an example, the method includes the following steps:

[0047] Step 1. The content of high-valence metal ions in the sample was determined by atomic absorption spectrometry. The obtained contents are shown in Table 2 below.

[0048] Table 2. Content of high-valent cations in Sample 2 from Shengli Oilfield

[0049]

[0050] Step 2. Calculate the influence parameter M of high-valence metal ions:

[0051]

[0052] Where m B Z represents the molality of high-valence metal ions B in the sample, in mmol / kg. B This indicates the valence number of the high-valence metal ion B in the sample.

[0053] The obtained M value was 168 mmol / kg.

[0054] Step 3. The surface tension of sample 2 at 25℃ was measured to be 36.3 mN / m using the pendant method.

[0055] Step 4. By comparing the M value and surface tension value of sample 2 with the threshold values ​​of the high-valence metal ion influence parameter M and surface tension, respectively, it can be seen that the obtained M value is >84mmol / kg and the surface tension is <45mN / m. Therefore, the sample is judged to be a difficult-to-demulsify sample.

[0056] The conventional dehydration rate method was used for verification: Sample 2 was placed in a 50mL glass graduated tube and left to stand in a 50℃ constant temperature water bath for 1 hour. The volume of water precipitated from the lower layer was observed, and the dehydration rate (the ratio of the volume of precipitated water to the total volume of water in the emulsion) was calculated. The calculated dehydration rate of the emulsion within 1 hour was 20%, which is lower than the industry standard (80% dehydration rate within 1 hour). Therefore, Sample 2 is a difficult-to-demulsify sample. Thus, the results obtained using the conventional dehydration rate method are consistent with those of this embodiment, and the method in this patent is feasible.

[0057] Example 3

[0058] A multi-index comprehensive evaluation method for the ease of demulsification of crude oil emulsions, taking sample 3 from Shengli Oilfield as an example, the method includes the following steps:

[0059] Step 1. The content of high-valence metal ions in the sample was determined by atomic absorption spectrometry. The obtained contents are shown in Table 3 below.

[0060] Table 3. Content of high-valent cations in sample 3 from Shengli Oilfield

[0061]

[0062] Step 2. Calculate the influence parameter M of high-valence metal ions:

[0063]

[0064] Where m B Z represents the molality of high-valence metal ions B in the sample, in mmol / kg. B This indicates the valence number of the high-valence metal ion B in the sample.

[0065] The obtained M value was 219 mmol / kg.

[0066] Step 3. The surface tension of sample 3 at 25℃ was measured to be 41.6 mN / m using the pendant method.

[0067] Step 4. By comparing the M value and surface tension value of sample 3 with the threshold values ​​of the high-valence metal ion influence parameter M and surface tension, respectively, it can be seen that the obtained M value is >84mmol / kg and the surface tension is <45mN / m. Therefore, the sample is judged to be a difficult-to-demulsify sample.

[0068] The conventional dehydration rate method was used for verification: Sample 3 was placed in a 50mL glass graduated tube and left to stand in a 50℃ constant temperature water bath for 1 hour. The volume of water precipitated from the lower layer was observed, and the dehydration rate (the ratio of the volume of precipitated water to the total volume of water in the emulsion) was calculated. The calculated dehydration rate of the emulsion within 1 hour was 13%, which is far lower than the industry standard (80% dehydration rate within 1 hour). Therefore, Sample 3 is a difficult-to-demulsify sample. Thus, the results obtained using the conventional dehydration rate method are consistent with those of this embodiment, and the method in this patent is feasible.

[0069] Example 4

[0070] A multi-index comprehensive evaluation method for the ease of demulsification of crude oil emulsions, taking sample 4 from Shengli Oilfield as an example, the method includes the following steps:

[0071] Step 1. The content of high-valence metal ions in the sample was determined by atomic absorption spectrometry. The obtained contents are shown in Table 4 below.

[0072] Table 4. Content of high-valent cations in sample 4 from Shengli Oilfield

[0073]

[0074] Step 2. Calculate the influence parameter M of high-valence metal ions:

[0075]

[0076] Where m B Z represents the molality of high-valence metal ions B in the sample, in mmol / kg. B This indicates the valence number of the high-valence metal ion B in the sample.

[0077] The obtained M value was 214 mmol / kg.

[0078] Step 3. The surface tension of sample 4 at 25℃ was measured to be 34.4 mN / m using the pendant method.

[0079] Step 4. By comparing the M value and surface tension value of sample 4 with the threshold values ​​of the high-valence metal ion influence parameter M and surface tension, respectively, it can be seen that the obtained M value is >84mmol / kg and the surface tension is <45mN / m. Therefore, the sample is judged to be a difficult-to-demulsify sample.

[0080] The conventional dehydration rate method was used for verification: Sample 4 was placed in a 50mL glass graduated tube and left to stand in a 50℃ constant temperature water bath for 1 hour. The volume of water precipitated from the lower layer was observed, and the dehydration rate (the ratio of the volume of precipitated water to the total volume of water in the emulsion) was calculated. The calculated dehydration rate of the emulsion within 1 hour was 36%, which is far lower than the industry standard (80% dehydration rate within 1 hour). Therefore, Sample 4 is a difficult-to-demulsify sample. Thus, the results obtained using the conventional dehydration rate method are consistent with those of this embodiment, and the method in this patent is feasible.

[0081] The above embodiments are preferred embodiments of the present invention, but the embodiments of the present invention are not limited to the above embodiments. Any changes, modifications, substitutions, combinations, or simplifications made without departing from the spirit and principle of the present invention shall be considered equivalent substitutions and shall be included within the protection scope of the present invention.

Claims

1. A multi-index comprehensive evaluation method for the ease of demulsification of crude oil emulsions, characterized in that, Includes the following steps: The content of high-valence metal ions in the sample is determined, and the influence parameter value of the high-valence metal ions is calculated; Measure the surface tension of the sample; The ease of demulsification of the crude oil emulsion sample is judged based on the obtained values ​​of the influence parameters of high-valence metal ions and surface tension. The parameter values ​​for the influence of high-valence metal ions are expressed by the following formula: ； Where m B Z represents the molality of high-valence metal ions B in the sample, in mmol / kg. B Indicates the valence number of the high-valence metal ion B in the sample; When the obtained high-valence metal ion influence parameter value is ≥84mmol / kg and the surface tension is <45mN / m, the crude oil emulsion sample is difficult to demulsify. When the obtained high-valence metal ion influence parameter value is <84mmol / kg or the surface tension is ≥45mN / m, the crude oil emulsion sample is prone to demulsification.

2. The multi-index comprehensive evaluation method according to claim 1, characterized in that, The high-valence metallic ions have an ionic valence greater than 1.

3. The multi-index comprehensive evaluation method according to claim 1, characterized in that, The content of high-valence metal ions in a sample was determined by atomic absorption spectrometry.

4. The multi-index comprehensive evaluation method according to claim 1, characterized in that, The surface tension of the sample at 20-25℃ was determined using the hanging plate method.

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