Method for evaluating influence of sand grains on organic solid phase deposition in crude oil

Abstract

The invention discloses a method for evaluating the influence of sand grains on organic solid phase deposition in crude oil, which mainly aims at the actual oil and gas production, and the wellhead temperature of an oil and gas well blocked by an organic solid phase is generally higher than 0 DEG C. Therefore, an interpolation base line in an interval from a wax precipitation point to 0 DEG C and a DSC curve are selected for surrounding to obtain a peak area; the ratio of the peak area to the mass of the sample mixture is used as the wax precipitation enthalpy of the test sample, the accurate wax content is determined through the wax precipitation enthalpy and the preset sample crystallization heat, and finally multiple groups of evaluation data are obtained through multiple tests so as to complete the evaluation of the influence of the sand grains on the organic solid phase deposition in the crude oil. By adopting the method, the defect that the wax precipitation condition of an oil and gas production site cannot be truly reflected due to the fact that only single crude oil is used for testing the wax precipitation point and the wax content can be effectively overcome; the method plays an important role in promoting the knowledge of oil field on-site crude oil wax precipitation.

Description

Technical Field

[0001] This invention belongs to the field of oil and gas field development technology, and particularly relates to the field of wellbore flow assurance technology, specifically to a method for evaluating the influence of sand particles on the deposition of organic solid phases in crude oil. Background Technology

[0002] Over the past decade, ultra-deep oil and gas discoveries have primarily occurred in the Tarim, Junggar, and Sichuan basins of Xinjiang. With the exploration and development of deep / ultra-deep oil and gas, wax deposition and bitumen sedimentation in oil and gas wells have become increasingly prominent. Since 2014, the problem of wellbore blockage by foreign objects (organic solid phases) has gradually emerged in the Tarim Basin platform area, concentrated in Fuman and Donghe. Similar problems have also appeared in areas such as Yudong and Bozi blocks in recent years, with the cumulative proportion of blocked wells exceeding 20%. Wellbore blockage by foreign objects affects production, causes difficulties in production layer testing, and leads to pipe bursts on the surface, becoming a key factor restricting the safe and stable production of oil wells.

[0003] As early as 2012, the petroleum and natural gas industry standard SY / T 0545-2012 "Determination of Thermal Characteristics Parameters of Wax Separation in Crude Oil by Differential Scanning Calorimetry" and the CNPC enterprise standard Q / SY TZ0659-2020 "Determination of Wax Content in Crude Oil by Differential Scanning Calorimetry" were implemented, proposing to test the wax content of crude oil using differential scanning calorimetry. The invention patent application (patent) CN202010214289.2 proposes a method for reconstructing the wax separation point of waxy crude oil in formations, which also obtains the reconstructed wax separation point of crude oil through differential scanning calorimetry and numerical simulation. Differential scanning calorimetry (DSC) is a method for measuring and recording the change in enthalpy and temperature relationship of a substance. It has the advantages of high precision and high resolution. Its principle is that during the heating or cooling process, changes in the structure, phase, or chemical properties of a substance will be accompanied by corresponding changes in enthalpy. Although the use of differential scanning calorimetry to determine the wax point of a single crude oil phase is widely recognized in the industry, in actual production processes, especially for oil and gas wells with formation sand production, relying solely on the wax point and wax content tests of a single crude oil cannot truly reflect the wax precipitation conditions at the oil and gas production site. Therefore, there are differences between the wax content and wax point measured by the crude oil differential scanning calorimeter and the actual wax content and wax point.

[0004] It is evident that existing evaluation methods, which rely solely on testing the wax precipitation point and wax content of a single crude oil, cannot accurately reflect the wax precipitation conditions at the oil and gas production site. This results in an inability to accurately simulate and evaluate the impact of sand particle size and content on the wax precipitation point and wax content of crude oil, making it difficult to accurately predict the risk of crude oil wax formation and affecting the safety and efficiency of oilfield operations. Summary of the Invention

[0005] The purpose of this invention is to provide a method for evaluating the influence of sand particles on the deposition of organic solid phases in crude oil, in order to solve the technical problem in existing evaluation methods that cannot truly reflect the wax precipitation conditions at the oil and gas production site due to the inability to accurately simulate and evaluate the influence of sand particle size and content on the wax precipitation point and wax content of crude oil, since relying solely on the wax precipitation point and wax content test of a single crude oil cannot accurately reflect the wax precipitation conditions at the oil and gas production site.

[0006] To achieve the above objectives, the present invention adopts the following technical solution:

[0007] A method for evaluating the effect of sand grains on the deposition of organic solid phases in crude oil includes:

[0008] S1: Differential scanning calorimetry is used to determine the differential heat flux of the sample mixture, and the DSC curve of the sample mixture is obtained based on the differential heat flux of the sample mixture; wherein, the sample mixture includes a mixture of crude oil and sand or a mixture of organic solid blockage and sand.

[0009] S2: Obtain the wax precipitation point and corresponding wax precipitation enthalpy of the sample mixture from the DSC curve; where the wax precipitation enthalpy is the ratio of the peak area to the mass of the sample mixture; the peak area is obtained by enclosing the interpolation baseline from the wax precipitation point of the sample to 0℃ and the DSC curve;

[0010] S3: Wax content is obtained based on the enthalpy of wax precipitation and the preset sample crystallization heat;

[0011] S4: Change the mixing ratio of crude oil and sand sample or organic solid blockage material and sand sample, and change the sand sample particle size. Repeat S1-S3 to obtain the wax content and corresponding wax precipitation point of multiple sets of test samples with different sand particle content, as well as the wax content and wax precipitation point of multiple sets of test samples with different sand particle size as evaluation data.

[0012] S5: Based on the obtained multiple sets of evaluation data, complete the evaluation of the influence of sand particles on the deposition of organic solid phases in crude oil.

[0013] Furthermore, if the sample mixture consists of an organic solid phase plug and a sand sample mixture, then before S1, the organic solid phase plug and sand sample mixture shall be pretreated, and the specific steps are as follows:

[0014] The first step involves sequentially subjecting the organic solid blockage to liquid-phase adsorption and high-temperature ashing treatments, and then calculating the weight loss rate of the treated organic solid blockage to determine its organic content.

[0015] The second step is to perform particle size analysis on the treated organic solid blockage to determine the particle size distribution, which will provide data support for evaluating the impact of sand particles on the deposition of organic solid phases in crude oil.

[0016] Furthermore, in S1, the specific steps for determining the differential heat flux of the sample mixture using differential scanning calorimetry are as follows:

[0017] Start the DSC analyzer and maintain the sample mixture at a constant temperature for a preset time; then begin the cooling process until the temperature drops to the preset temperature, and record the differential heat flux of the sample mixture and the reference at each temperature point.

[0018] Furthermore, if the sample mixture includes a flowable crude oil sample, it is maintained at a constant temperature for 1 to 2 minutes; if the sample mixture includes a non-flowable crude oil sample, it is maintained at a constant temperature for 3 to 5 minutes; if the sample mixture includes organic solid blockages, it is maintained at a constant temperature for 5 to 10 minutes.

[0019] Further, the DSC analyzer is started, and the detection cell of the DSC analyzer is first heated to the initial test temperature. The sample mixture is then kept at the initial temperature for a preset time. Specifically, at room temperature, if the sample mixture includes a flowable crude oil sample, the initial temperature is 80°C; if the sample mixture includes a non-flowable crude oil sample, the initial temperature is 120°C; and if the sample mixture includes organic solid blockages, the initial temperature is 150°C to 200°C.

[0020] Furthermore, the temperature is lowered starting from the initial temperature until it drops to -30℃ to -20℃.

[0021] Furthermore, in S2, the specific steps for obtaining the wax precipitation point of the sample based on the DSC curve of the sample mixture are as follows:

[0022] Two curves are plotted on the DSC curve at the point where it begins to deviate from the exothermic baseline. One curve is the exothermic baseline at high temperature, and the other curve is the first front line that begins to deviate from the exothermic baseline. The intersection of the extensions of the two curves is taken as the first wax precipitation point.

[0023] The temperature increment is determined by half the difference between the starting temperature at the point where the DSC curve begins to deviate from the exothermic baseline and the first wax precipitation point.

[0024] The sum of the first wax precipitation point and the temperature increase value is taken as the wax precipitation point of the sample.

[0025] Further, in S3, the wax content is the ratio of the enthalpy of wax precipitation to the crystallization of the preset sample; wherein, the specific formula for calculating the wax content is as follows:

[0026]

[0027] In the formula, φ represents the wax content, which is a percentage by mass; ΔH 测试样品 This indicates the heat of crystallization of the sample, in J / g;

[0028] ΔH 区块标样represents the wax precipitation enthalpy of the sample, J / g; f represents the peak area, mJ; m represents the sample mass, mg; K represents the DSC instrument calibration constant, with a value of 1.

[0029] Furthermore, the crystallization of the preset sample is obtained by testing methods or by directly selecting the average heat of crystallization, which is 190 J / g to 210 J / g.

[0030] Furthermore, an orthogonal experimental design method was adopted to change the mixing ratio of crude oil and sand sample or organic solid blockage material and sand sample, as well as the sand sample particle size. S1-S3 were repeated to obtain the wax content and corresponding wax precipitation point of multiple groups of test samples with different sand particle content, as well as the wax content and wax precipitation point of multiple groups of test samples with different sand particle sizes as evaluation data.

[0031] Compared with the prior art, the present invention has the following beneficial effects:

[0032] This invention provides a method for evaluating the influence of sand particles on the deposition of organic solid phases in crude oil. This method is primarily designed for practical oil and gas production. For oil and gas wells with organic solid phase blockage, the wellhead temperature is generally above 0°C. Therefore, this method selects an interpolated baseline within the wax precipitation point to 0°C range and uses it to enclose the peak area with the DSC curve. The ratio of the peak area to the mass of the sample mixture is then used as the wax precipitation enthalpy of the test sample. By comparing the wax precipitation enthalpy with the preset sample crystallization heat, the precise wax content is determined. Finally, multiple sets of evaluation data are obtained through repeated experiments to complete the evaluation of the influence of sand particles on the deposition of organic solid phases in crude oil. This method effectively solves the problem of relying solely on a single crude oil for wax precipitation point and wax content testing, which fails to accurately reflect the wax precipitation conditions at the oil and gas production site. This method, by realistically simulating and evaluating the influence of sand particle size and content on the wax precipitation point and wax content of crude oil, plays a significant role in improving the understanding of crude oil wax formation in oilfields.

[0033] Preferably, in this invention, the mixture of organic solid blockage and sand sample is pretreated, and the organic content is determined by liquid phase adsorption and high-temperature ashing treatment, and particle size analysis is performed, which improves the accuracy and reliability of the evaluation. This provides more detailed and accurate data support for the subsequent evaluation of the influence of sand particles on organic solid deposition.

[0034] Preferably, in this invention, by starting the DSC detector, the sample mixture is placed in a constant temperature state for a preset time; then the cooling process is started until the temperature drops to the preset temperature, and the differential heat flow of the sample mixture and the reference material at each temperature point is recorded; the above operation ensures the standardization and consistency of the measurement process, thereby improving the accuracy and repeatability of the test results.

[0035] More preferably, in this invention, different isothermal holding times are set according to the characteristics of different types of sample mixtures, ensuring that the samples reach a stable state before testing, thereby further improving the accuracy of the test results.

[0036] More preferably, in this invention, different initial heating temperatures and isothermal holding times are set according to the type of sample mixture, which helps to eliminate the thermal history effect in the sample and ensure the accuracy and reliability of the DSC curve.

[0037] More preferably, in this invention, the endpoint temperature range of the cooling process is given, ensuring that the DSC curve can cover the main exothermic range of the sample, thereby accurately obtaining key parameters such as the wax precipitation point and wax precipitation enthalpy.

[0038] Preferably, in this invention, the wax precipitation point is determined by plotting two curves and calculating the temperature increase value based on the starting point of the DSC curve where it deviates from the exothermic baseline, thereby improving the accuracy and scientific nature of the wax precipitation point determination.

[0039] Preferably, in this invention, the wax content is calculated by the ratio of the wax precipitation enthalpy to the preset sample crystallization heat, providing a quantitative indicator for evaluating the influence of sand particles on the deposition of organic solid phases in crude oil.

[0040] Preferably, in this invention, the heat of crystallization of the preset sample can be obtained by testing or by selecting the average heat of crystallization, which provides a flexible option for calculating the wax content and improves the applicability of the evaluation method.

[0041] Preferably, in this invention, an orthogonal experimental design method is used to systematically obtain multiple sets of evaluation data by changing the mixing ratio of crude oil and sand sample or organic solid phase blockage material and sand sample, as well as the sand sample particle size. This method can efficiently screen out the key factors affecting organic solid phase deposition and provide a scientific basis for formulating effective prevention and control measures. Attached Figure Description

[0042] Figure 1 A flowchart illustrating a method for evaluating the effect of sand particles on the deposition of organic solid phases in crude oil, provided as an embodiment of the present invention;

[0043] Figure 2 This is a result analysis report diagram of the DSC detector provided in an embodiment of the present invention;

[0044] Figure 3 The DSC curves show the effect of different sand contents on the deposition of organic solid phases in crude oil, as provided in the embodiments of the present invention. Detailed Implementation

[0045] To enable those skilled in the art to better understand the technical solutions of this invention, the technical solutions in the embodiments of this invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this invention, and not all embodiments. Based on the embodiments of this invention, all other embodiments obtained by those skilled in the art without creative effort should fall within the scope of protection of this invention.

[0046] It should be noted that when an element is referred to as being "set on" another element, it can be directly on the other element or there may be an intervening element. When an element is referred to as being "connected to" another element, it can be directly connected to the other element or there may be an intervening element. The terms "vertical," "horizontal," "left," "right," and similar expressions used herein are for illustrative purposes only and do not represent the only embodiments.

[0047] Example 1

[0048] As mentioned in the background section, although the use of differential scanning calorimetry (DSC) to determine the wax point of a single crude oil phase is widely accepted in the industry, in actual production processes, especially for oil and gas wells with formation sand production, relying solely on testing the wax point and wax content of a single crude oil cannot accurately reflect the wax precipitation conditions at the oil and gas production site. Therefore, there is a difference between the wax content and wax point measured by the crude oil DSC and the actual wax content and wax point. It is evident that because relying solely on testing the wax point and wax content of a single crude oil cannot accurately reflect the wax precipitation conditions at the oil and gas production site, it is impossible to accurately simulate and evaluate the impact of sand particle size and content on the wax point and wax content of crude oil. This makes it difficult to accurately predict the risk of crude oil wax formation, affecting the safety and efficiency of oilfield operations.

[0049] To address the above issues, this embodiment provides a method for evaluating the influence of sand particles on the deposition of organic solid phases in crude oil. This method can realistically simulate and evaluate the effects of sand particle size and content on the wax precipitation point and wax content of crude oil, which plays an important role in improving the understanding of crude oil wax deposition in oilfields.

[0050] like Figure 1 As shown in the figure, this embodiment provides a method for evaluating the influence of sand particles on the deposition of organic solid phases in crude oil. The specific steps are as follows:

[0051] S1: Differential scanning calorimetry is used to determine the differential heat flux of the sample mixture, and the DSC curve of the sample mixture is obtained based on the differential heat flux of the sample mixture; wherein, the sample mixture includes a mixture of crude oil and sand or a mixture of organic solid blockage and sand.

[0052] Here, if the sample mixture consists of an organic solid blockage and a sand sample, then before S1, the organic solid blockage and sand sample mixture shall be pretreated. The specific steps are as follows:

[0053] The first step involves sequentially subjecting the organic solid blockage to liquid-phase adsorption and high-temperature ashing treatments, and then calculating the weight loss rate of the treated organic solid blockage to determine its organic content.

[0054] The second step is to perform particle size analysis on the treated organic solid blockage to determine the particle size distribution, which will provide data support for evaluating the impact of sand particles on the deposition of organic solid phases in crude oil.

[0055] In this embodiment, the specific steps for determining the differential heat flux of the sample mixture using differential scanning calorimetry are as follows:

[0056] Start the DSC analyzer and first heat the analyzer's detection cell to the initial test temperature. Place the sample mixture at the initial temperature for a preset time. At room temperature, if the sample mixture includes a flowable crude oil sample, the initial temperature is 80°C; if the sample mixture includes a non-flowable crude oil sample, the initial temperature is 120°C; if the sample mixture includes organic solid blockages, the initial temperature is 150°C to 200°C. Then begin the cooling process until the temperature drops to -30°C to -20°C, and record the differential heat flux of the sample mixture and the reference material at each temperature point.

[0057] Specifically, if the sample mixture includes a flowable crude oil sample, it should be kept at a constant temperature for 1 to 2 minutes; if the sample mixture includes a non-flowable crude oil sample, it should be kept at a constant temperature for 3 to 5 minutes; if the sample mixture includes organic solid blockages, it should be kept at a constant temperature for 5 to 10 minutes.

[0058] S2: Obtain the wax precipitation point and corresponding wax precipitation enthalpy of the sample mixture from the DSC curve of the sample mixture; wherein, the wax precipitation enthalpy is the ratio of the peak area to the mass of the sample mixture; the peak area is obtained by enclosing the interpolation baseline from the wax precipitation point of the sample to 0℃ and the DSC curve.

[0059] In this embodiment, the specific steps for obtaining the wax precipitation point of the sample based on the DSC curve of the sample mixture are as follows:

[0060] Two curves are plotted on the DSC curve at the point where the curve begins to deviate from the exothermic baseline. One curve represents the exothermic baseline at high temperature, and the other curve represents the first peak line at the point where the curve begins to deviate from the exothermic baseline. The intersection of the extensions of the two curves is taken as the first wax precipitation point. Half of the difference between the starting temperature at the point where the curve begins to deviate from the exothermic baseline and the first wax precipitation point is taken as the temperature increase value. The sum of the first wax precipitation point and the temperature increase value is taken as the wax precipitation point of the sample.

[0061] S3: The wax content is obtained based on the wax precipitation enthalpy and the preset sample crystallization heat; wherein, the preset sample crystallization is obtained by a test method or by directly selecting the average crystallization heat, which is 190J / g~210J / g.

[0062] In this embodiment, the wax content is the ratio of the enthalpy of wax precipitation to the crystallization of the preset sample; the specific formula for calculating the wax content is as follows:

[0063]

[0064] In the formula, φ represents the wax content, which is a percentage by mass; ΔH 测试样品 This indicates the heat of crystallization of the sample, in J / g;

[0065] ΔH 区块标样 represents the wax precipitation enthalpy of the sample, J / g; f represents the peak area, mJ; m represents the sample mass, mg; K represents the DSC instrument calibration constant, with a value of 1.

[0066] S4: Change the mixing ratio of crude oil and sand sample or organic solid blockage material and sand sample, and change the sand sample particle size. Repeat S1-S3 to obtain the wax content and corresponding wax precipitation point of multiple sets of test samples with different sand particle content, as well as the wax content and wax precipitation point of multiple sets of test samples with different sand particle size as evaluation data.

[0067] S5: Based on the obtained multiple sets of evaluation data, complete the evaluation of the influence of sand particles on the deposition of organic solid phases in crude oil.

[0068] Specifically, an orthogonal experimental design method is preferred. The mixing ratio of crude oil and sand sample or organic solid blockage material and sand sample is changed, as well as the particle size of sand sample is changed. S1-S3 are repeated to obtain the wax content and corresponding wax precipitation point of multiple sets of test samples with different sand particle content, as well as the wax content and wax precipitation point of multiple sets of test samples with different sand particle sizes as evaluation data.

[0069] To gain a more comprehensive understanding of this embodiment, the method will be described in more detail below:

[0070] This embodiment provides a method for evaluating the influence of sand particles on the deposition of organic solid phases in crude oil. The more detailed steps are as follows:

[0071] (1) For crude oil fluid samples that are liquid at room temperature, there is no need to perform a pretreatment step for organic solid blockages.

[0072] (2) If the sample mixture consists of an organic solid blockage material and a sand sample, the pretreatment steps for the organic solid blockage material are as follows:

[0073] ① Organic matter content: Use filter paper to remove moisture and other liquid phases (such as crude oil) from the organic solid blockage. Take a certain amount of organic blockage sample, aerate it on an electric furnace, and then place it in a muffle furnace for high-temperature ashing. Burn it at 550℃ for 2 hours, cool it to room temperature, weigh it, calculate its weight loss rate, and determine the organic matter content.

[0074] ② Regarding organic blockages, the remaining samples after high-temperature ashing are generally formation runoff sand. The sand samples are taken, weighed, and their particle size is analyzed to determine their particle size distribution, providing data support for subsequent evaluation of the impact of sand particles on the deposition of organic solid phases in crude oil.

[0075] (3) Test the heat of crystallization of the sample. Here, the heat of crystallization of the block organic solid phase blockage wax sample is used to calibrate the heat enthalpy of wax precipitation per unit mass. Of course, the average heat of crystallization of wax precipitation of domestic crude oil can also be selected, which is about 190J / g~210J / g. The value can be selected according to the compactness of the wax sample. If it is a dense wax sample, a high value can be selected, and otherwise a low value can be selected.

[0076] (4) Select a certain amount of sample mixture, that is, place the crude oil and sand mixture or the organic solid blockage and sand mixture in the crucible of the differential scanning calorimeter (dynamic DSC detector) and cold weld it for later use; the ratio of crude oil to sand sample is mixed according to their mass content. The mixing ratio can be referred to the actual situation of oil and gas well production site, or it can be determined by yourself according to the research and analysis needs.

[0077] (5) Start the DSC detector: Set the temperature program, start the DSC detector, and heat the DSC detection cell to the initial test temperature (80℃ for flowable crude oil samples at room temperature; 120℃ for non-flowable crude oil samples (heavy oil) at room temperature; and 150℃~200℃ for organic solid blockages).

[0078] (6) Temperature stability: If it is a flowable crude oil sample at room temperature, the temperature is stabilized for 1 min to 2 min; if it is a non-flowable crude oil sample (heavy oil) at room temperature, the temperature is stabilized for 3 min to 5 min; the temperature of organic solid blockage is stabilized for 5 min to 10 min, so as to ensure that the sample is heated sufficiently at the set temperature and avoid the occurrence of phase instability.

[0079] (7) Cooling test: Starting from the set temperature, the temperature is reduced at a certain rate until -30℃ (or -20℃). The differential heat flow of the sample and the reference material at each temperature point is recorded. The differential scanning calorimetry curve (DSC curve) is plotted with the differential heat flow as the vertical axis and the temperature as the horizontal axis.

[0080] (8) Sample wax precipitation point: Draw two curves at the point on the DSC curve where it begins to deviate from the exothermic baseline. One curve is the exothermic baseline at high temperature, and the other curve is the first peak line at the point where it begins to deviate from the exothermic baseline. The intersection of the extensions of the two curves is the first wax precipitation point. This wax precipitation point is lower than the true value of the wax precipitation point. The sample wax precipitation point is increased by a certain temperature based on the first wax precipitation point. The temperature increase is based on half of the difference between the starting temperature at the point on the DSC curve where it begins to deviate from the exothermic baseline and the first wax precipitation point. Generally, the increase is 0.5℃ to 5℃. The first wax precipitation point plus the temperature increase value is the sample wax precipitation point.

[0081] (9) Wax content: Currently, the industry generally selects the ratio of the peak area enclosed by the interpolation baseline and the DSC curve in the range from the wax precipitation point to -20℃ to the sample mass as the wax precipitation enthalpy of the test sample. The wax content is determined by the ratio of the wax precipitation enthalpy of the sample to the crystallization heat of the blocky organic solid phase blockage wax sample.

[0082] This application primarily addresses practical oil and gas production. For oil and gas wells with organic solid phase blockage, the wellhead temperature is generally higher than 0℃. Therefore, the ratio of the peak area enclosed by the interpolation baseline and the DSC curve in the wax precipitation point to 0℃ range to the sample mass is selected as the wax precipitation enthalpy of the test sample. The wax content is determined by the ratio of the sample's wax precipitation enthalpy to the crystallization heat of the wax sample from the organic solid phase blockage in the block.

[0083]

[0084] In the formula, φ represents the wax content, which is a percentage by mass; ΔH 测试样品 This indicates the heat of crystallization of the sample, in J / g;

[0085] ΔH 区块标样 represents the wax precipitation enthalpy of the sample, J / g; f represents the peak area, mJ; m represents the sample mass, mg; K represents the DSC instrument calibration constant, with a value of 1.

[0086] (10) By changing the mixing ratio of crude oil and sand sample or organic solid blockage material and sand sample, and repeating steps (5) to (9), the wax content and wax precipitation point of test samples with different sand particle content can be obtained.

[0087] (11) Change the particle size of the sand sample and mix it with crude oil or organic solid blockage. Repeat steps (5) to (9) to obtain the wax content and wax precipitation point of test samples with different sand particle sizes.

[0088] (12) Adopt orthogonal experimental design method, and change the sand sample particle size and the mixing ratio of sand sample with crude oil or organic solid phase blockage; or clarify the influence of sand particles on the deposition of organic solid phase in crude oil by analyzing steps (10) and (11).

[0089] Therefore, this method is an evaluation method based on wellbore blockage pretreatment, sand particle size analysis in the sample, and differential scanning calorimetry (DSC) of fluid / organic solid phase. Compared with conventional DSC, its principle is equivalent to providing wax nuclei to crude oil or organic solid phase at a higher temperature (generally higher than the wax precipitation point tested by DSC). These nuclei will promote wax precipitation in crude oil / organic solid phase, which is reflected in the DSC curve as an increase in the wax precipitation point, and also affects the test results of wax content. Primarily targeting practical oil and gas production, for oil and gas wells with organic solid phase blockage, the wellhead temperature is generally higher than 0℃. Therefore, the ratio of the peak area enclosed by the interpolation baseline and the DSC curve within the wax precipitation point to 0℃ range to the sample mass is selected as the wax precipitation enthalpy of the test sample. The wax content is determined by the ratio of the sample's wax precipitation enthalpy to the crystallization heat of the wax sample from the organic solid phase blockage in the block. The wax precipitation point of the sample is determined by adding a certain temperature to the first wax precipitation point. The temperature increase is calculated as half the difference between the starting temperature at the point where the DSC curve begins to deviate from the exothermic baseline and the first wax precipitation point. The first wax precipitation point plus the temperature increase value is the sample's wax precipitation point. This method overcomes the shortcomings of relying solely on single crude oil for wax precipitation point and wax content testing, which cannot accurately reflect the wax precipitation conditions at the oil and gas production site. By realistically simulating and evaluating the impact of sand particle size and content on the wax precipitation point and wax content of crude oil, it plays a significant role in improving the understanding of crude oil wax formation in oilfields.

[0090] Example 2

[0091] In this embodiment, the method mentioned in Embodiment 1 is applied in practice, and the specific steps are as follows:

[0092] (1) Purify the organic blockage in the block and remove the waxy components (mainly remove the asphalt).

[0093] (2) Test the heat of crystallization of the purified organic solid phase and obtain the average heat of crystallization of the block wax sample by arithmetic mean.

[0094] (3) As shown in Table 1, the remaining sample after high-temperature ashing of sample #3 (unpurified) was selected. The sand sample was weighed and its particle size distribution was determined through particle size analysis. This provides data support for the subsequent evaluation of the influence of sand particles on the deposition of organic solid phases in crude oil. Figure 2 As shown.

[0095] Table 1 shows the crystallization heat of different crude oil wax samples.

[0096] (4) Select 6.75 mg of organic solid blockage material and 0.1 mg of sand sample, mix them evenly and place them in the crucible of the differential scanning calorimeter for cold welding.

[0097] (5) Start the DSC detector: Set the temperature program, start the DSC detector, and heat the DSC detection cell to the initial test temperature (set to 150℃).

[0098] (6) Temperature stabilization: The temperature of the organic solid blockage is stabilized for 5 minutes to ensure that the sample is heated sufficiently at the set temperature and to avoid the occurrence of phase instability.

[0099] (7) Cooling Test: Starting from the set temperature, the temperature is reduced at a rate of 5℃ / min until it reaches -30℃. The differential heat flow of the sample and the reference material at each temperature point is recorded. A differential scanning calorimetry (DSC) curve of crude oil wax precipitation is plotted with differential heat flow as the ordinate and temperature as the abscissa. Figure 2 As shown, the DSC curves were plotted based on different sand sample contents.

[0100] (8) Sample wax precipitation point: Draw two curves at the point where the DSC curve begins to deviate from the exothermic baseline. One curve is the exothermic baseline at high temperature, and the other curve is the first peak line at the point where the curve begins to deviate from the exothermic baseline. The intersection of the extensions of the two curves is the first wax precipitation point. This wax precipitation point is lower than the true value of the wax precipitation point. The sample wax precipitation point is increased by a certain temperature based on the first wax precipitation point. The temperature increase is half of the difference between the starting temperature at the point where the DSC curve begins to deviate from the exothermic baseline and the first wax precipitation point. The first wax precipitation point plus the temperature increase value is the sample wax precipitation point.

[0101] (9) Wax content: For oil and gas wells with organic solid phase blockage, the wellhead temperature is generally higher than 0℃. Therefore, the ratio of the peak area enclosed by the interpolation baseline and the DSC curve in the range from the wax precipitation point to 0℃ to the sample mass is selected as the wax precipitation enthalpy of the test sample. The wax content is determined by the ratio of the wax precipitation enthalpy of the sample to the crystallization heat of the wax sample of the organic solid phase blockage in the block. Here, the crystallization heat of wax samples of different crude oils is obtained, as shown in Table 2.

[0102] Table 2 shows the crystallization heat of different crude oil wax samples.

[0103]

[0104] (10) Change the mixing ratio of crude oil and sand sample or organic solid blockage and sand sample, select 5.28mg organic solid blockage and 0.2mg sand sample, repeat steps (5) to (9) to obtain the wax content and wax precipitation point of test samples with different sand content.

[0105] In summary, this invention provides a method for evaluating the influence of sand particles on the deposition of organic solid phases in crude oil, and provides a scientific, systematic and accurate method for assessing the influence of sand particles on the deposition of organic solid phases in crude oil. First, differential scanning calorimetry (DSC) is used to quantitatively determine the thermal behavior of sample mixtures (including crude oil and sand mixtures or organic solid blockages and sand mixtures) during the cooling process, thereby obtaining DSC curves reflecting wax precipitation characteristics. This step not only ensures the accuracy of the test but also provides a reliable data foundation for subsequent analysis. Next, the wax precipitation point and corresponding wax precipitation enthalpy extracted from the DSC curve are key parameters for evaluating wax precipitation behavior in crude oil. The calculation of the wax precipitation enthalpy considers the relationship between peak area and sample mass and is accurately determined by the interpolation baseline method. Furthermore, for actual oil and gas production, this method selects the interpolation baseline from the wax precipitation point to 0℃ and encloses the DSC curve to obtain the peak area, thus accurately reflecting the wax precipitation conditions at the oil and gas production site. Based on these parameters, the wax content can be calculated, providing a quantitative indicator for assessing the influence of sand particles on wax deposition. In addition, this method also conducts multiple sets of experiments by changing the mixing ratio of crude oil and sand or organic solid blockages and sand, as well as the sand particle size, to comprehensively investigate the influence of sand particles on organic solid deposition under different conditions. This orthogonal experimental design method not only improves experimental efficiency but also ensures the comprehensiveness and representativeness of the data. Ultimately, based on the comprehensive analysis of multiple sets of evaluation data, the impact of sand particles on the deposition of organic solid phases in crude oil can be more accurately assessed, providing scientific basis and technical support for oilfield development, pipeline transportation, and sediment control.

[0106] Unless otherwise defined, 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. The terminology used herein in the specification of this invention is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. The term "and / or" as used herein includes any and all combinations of one or more of the associated listed items.

[0107] The above are merely preferred embodiments of the present invention, but the scope of protection of the present invention is not limited thereto. Any equivalent substitutions or modifications made by those skilled in the art within the scope of the technology disclosed in the present invention, based on the technical solution and the disclosed concept of the present invention, should be covered within the scope of protection of the present invention.

[0108] The further detailed description provided in this publication should not be construed as limiting the specific embodiments of the present invention to this extent. For those skilled in the art, several simple deductions or substitutions can be made without departing from the concept of the present invention, and all such deductions or substitutions should be considered as falling within the scope of protection of the present invention as defined by the submitted claims.

Claims

1. A method for evaluating the effect of sand on the deposition of organic solids in crude oil, characterized in that, The method comprises the following steps: S1: differential scanning calorimetry is used to measure the differential heat flow of the sample mixture, and the DSC curve of the sample mixture is obtained according to the differential heat flow of the sample mixture; wherein the sample mixture comprises a crude oil and sand sample mixture or an organic solid phase plugging material and sand sample mixture; S2: the wax precipitation point and the corresponding wax precipitation enthalpy of the sample are obtained according to the DSC curve of the sample mixture; wherein the wax precipitation enthalpy is the ratio of the peak area to the mass of the sample mixture; the peak area is obtained by surrounding the DSC curve with the interpolation baseline in the interval from the wax precipitation point of the sample to 0℃; S3: the wax content is obtained based on the wax precipitation enthalpy and the preset sample crystallization heat; S4: the mixing ratio of the crude oil and sand sample or the organic solid phase plugging material and sand sample is changed, and the sand sample particle size is changed, and S1-S3 are repeated to obtain the wax content and the corresponding wax precipitation point of a plurality of different sand particle content test samples, and the wax content and the wax precipitation point of a plurality of different sand particle size test samples are obtained as evaluation data; S5: the evaluation of the influence of the sand particles on the organic solid phase deposition in the crude oil is completed based on the obtained plurality of evaluation data.

2. The method for evaluating the effect of sand on the deposition of organic solids in crude oil according to claim 1, characterized in that, If the sample mixture is an organic solid phase plugging material and sand sample mixture, the organic solid phase plugging material and sand sample mixture is pretreated before S1, and the specific steps are as follows: Firstly, the organic solid phase plugging material is sequentially subjected to liquid phase adsorption and high temperature ashing treatment, and the weight loss rate of the treated organic solid phase plugging material is calculated to determine the organic matter content; Secondly, the particle size analysis of the treated organic solid phase plugging material is performed to determine the particle size distribution, which provides data support for the evaluation of the influence of the sand particles on the organic solid phase deposition in the crude oil.

3. The method of evaluating the effect of sand on the deposition of organic solids in crude oil according to claim 1, wherein, In S1, the specific steps of using differential scanning calorimetry to measure the differential heat flow of the sample mixture are as follows: Start the DSC detector, place the sample mixture in a constant temperature state for a preset time, and then start the cooling process until the temperature drops to a preset temperature, and record the differential heat flow of the sample mixture and the reference material at each temperature point.

4. The method of evaluating the effect of sand on the deposition of organic solids in crude oil according to claim 3, wherein, If the sample mixture includes flowable crude oil samples, the constant temperature state is maintained for 1-2 minutes; if the sample mixture includes non-flowable crude oil samples, the constant temperature state is maintained for 3-5 minutes; if the sample mixture includes organic solid phase plugging material, the constant temperature state is maintained for 5-10 minutes.

5. The method of evaluating the effect of sand on the deposition of organic solids in crude oil according to claim 3, wherein, Start the DSC detector, first heat the detection cell of the DSC detector to the initial temperature of the test, and place the sample mixture in a constant temperature state at the initial temperature for a preset time; wherein at room temperature, if the sample mixture includes flowable crude oil samples, the initial temperature is 80℃; if the sample mixture includes non-flowable crude oil samples, the initial temperature is 120℃; if the sample mixture includes organic solid phase plugging material, the initial temperature is 150-200℃.

6. The method for evaluating the effect of sand on the deposition of organic solids in crude oil according to claim 5, characterized in that, Start cooling from the initial temperature until the temperature drops to -30- -20℃.

7. The method of evaluating the effect of sand on the deposition of organic solids in crude oil of claim 1, wherein, In S2, the specific steps of obtaining the wax precipitation point of the sample according to the DSC curve of the sample mixture are as follows: Draw two curves on the DSC curve where the heat release baseline starts to deviate, one curve is the heat release baseline at high temperature, and the other curve is the first line where the heat release baseline starts to deviate, and the intersection of the extensions of the two curves is taken as the first wax precipitation point; According to the half of the difference between the starting point temperature at which the DSC curve starts to deviate from the exothermic baseline and the first wax precipitation point as the temperature increase value; The sum of the first wax precipitation point and the temperature increase value is taken as the sample wax precipitation point.

8. The method of evaluating the effect of sand on the deposition of organic solids in crude oil of claim 1, wherein, In S3, the wax content is the ratio of the wax precipitation enthalpy to the preset sample crystallization; wherein, the specific calculation formula of the wax content is as follows: In the formula, φ represents the wax content, mass percent; ΔH 测试样品 represents the crystallization heat of the sample, J / g; ΔH 区块标样 represents the waxing thermal enthalpy of the sample, J / g; f represents the peak area, mJ; m represents the sample mass, mg; and K represents the DSC detector calibration constant, which has a value of 1.

9. The method for evaluating the effect of sand on the deposition of organic solids in crude oil according to claim 8, characterized in that, The preset sample crystallization is obtained by a test method, or directly selects an average crystallization heat, and the average crystallization heat is 190J / g-210J / g.

10. The method for evaluating the effect of sand on the deposition of organic solids in crude oil according to claim 1, characterized in that, By adopting an orthogonal experimental design method, the mixing ratio of the crude oil and the sand sample or the organic solid phase blocking object and the sand sample is changed, and the sand sample particle size is changed, S1-S3 are repeated, the wax content and the corresponding wax precipitation point of a plurality of groups of different sand particle content test samples are obtained, and the wax content and the wax precipitation point of a plurality of groups of different sand particle size test samples are taken as evaluation data.

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