Evaluation method for oxidation activity of crude oil and method for increasing oxidation activity of crude oil

Abstract

The present invention relates to the technical field of crude oil exploitation, and discloses a method for evaluating the oxidation activity of crude oil and a method for improving the oxidation activity of crude oil. The evaluation method includes: collecting multiple groups of crude oil; respectively conducting oxidation kinetics tests on the multiple groups of crude oil to obtain the oxidation kinetics curves of each group of crude oil; according to the oxidation kinetics curves, dividing the oxidation process of each group of crude oil into three specific processes, namely, low-temperature oxidation process, negative temperature coefficient oxidation process and high-temperature oxidation process, and obtaining the reaction equations occurring in each of the three specific processes through simulation analysis; conducting an oxidation kinetics test on the crude oil to be evaluated to judge the oxidation activity of the crude oil to be evaluated. Three possible situations for judging the oxidation activity of crude oil are determined according to the evaluation method of the present invention, and corresponding measures are taken for Class II oil and Class III oil according to the judgment results to improve the oxidation activity of crude oil, thereby avoiding ignition failure caused by too long ignition delay time and improving the efficiency of air injection development.

Description

Technical Field

[0001] The present invention relates to the technical field of heavy oil production by air injection, and particularly to a method for evaluating the oxidation activity of crude oil and a method for improving the oxidation activity of crude oil. Background Art

[0002] The commonly used technologies in domestic and foreign crude oil development - the implementation design and exploitation of air flooding and in-situ combustion, respectively focus on the description and realization of the low-temperature oxidation and high-temperature oxidation characteristics of crude oil and reservoirs. That is, it is considered that air flooding is a process of injecting high-pressure air into the reservoir, and the components of formation crude oil react with oxygen in the air to undergo low-temperature oxidation; in-situ combustion is a high-temperature oxidation process of using various ignition methods to ignite the oil layer of the injection well and continue to inject air or oxygen into the oil layer to assist combustion to form a moving combustion front. Although designing the exploitation conditions through low-temperature oxidation and high-temperature oxidation respectively can be applicable to most cases, phenomena such as pore plugging and ignition delay will occur in laboratory experiments and field implementations, resulting in poor efficiency of air flooding and failure of in-situ combustion, seriously restricting the application and development of related technologies.

[0003] The prior art is difficult to explain phenomena such as pore plugging and ignition delay. "Pore plugging" mainly refers to the phenomenon that during the process of air injection for production, crude oil severely cokes in the reservoir, blocks the displacement channel, reduces the gas-phase permeability, and cuts off the oxygen supply at the front of the air injection. "Ignition delay" refers to the phenomenon that the fuel-air mixture does not immediately ignite and burn when the temperature is higher than the ignition temperature. "Ignition delay" will affect the occurrence time and action range of high-temperature oxidation. When the "ignition delay" phenomenon is significant, it is impossible to achieve air injection production mainly involving high-temperature oxidation reactions.

[0004] During the process of crude oil exploitation at home and abroad, whether it is medium-temperature gas-steam flooding, air flooding or in-situ combustion, it is necessary to master the oxidation characteristics of crude oil. And the oxidation activity is the main reason affecting the oxidation characteristics, and the oxidation activity determines the oxidation characteristics. For different geological oil layers, the viscosity, components, and oxidation kinetic characteristics of their crude oil vary greatly, and thus the selected oil production methods and oil production processes are significantly different. Internationally, there have been phenomena such as ignition failure due to unclear oxidation kinetic characteristics of crude oil, seriously affecting the oil recovery rate. Summary of the Invention

[0005] The purpose of the present invention is to overcome the problems of ignition delay, ignition failure, and low efficiency of crude oil air injection production existing in the prior art due to inaccurate division of the crude oil reaction process and inaccurate understanding of the oxidation activity of crude oil, and to provide a method for evaluating the oxidation activity of crude oil and a method for improving the oxidation activity of crude oil, which method improves the efficiency of crude oil air injection production.

[0006] To achieve the above purpose, in the first aspect of the present invention, a method for evaluating the oxidation activity of crude oil is provided, and the evaluation method includes:

[0007] S1. Collect multiple groups of crude oil;

[0008] S2. Conduct oxidation kinetics tests on the multiple groups of crude oil respectively to obtain the oxidation kinetics curves of each group of crude oil;

[0009] S3. According to the oxidation kinetics curves, divide the oxidation process of each group of crude oil into three specific processes: low-temperature oxidation process, negative temperature coefficient oxidation process, and high-temperature oxidation process, and obtain the reaction equations occurring in each of the three specific processes through simulation analysis;

[0010] S4. Conduct oxidation kinetics tests on the crude oil to be evaluated, and obtain the reaction equation occurring in the crude oil to be evaluated through simulation analysis;

[0011] S5. Judge the oxidation activity of the crude oil according to the correlation between the reaction equation occurring in the crude oil to be evaluated and the reaction equations occurring in each of the three specific processes.

[0012] In the second aspect of the present invention, a method for improving the oxidation activity of crude oil is provided, and the method includes:

[0013] Judge the oxidation activity of the crude oil to be tested according to the evaluation method described in any one of the foregoing;

[0014] Take corresponding measures according to the judgment result of the oxidation activity of the crude oil to be tested to improve the oxidation activity of the crude oil to be tested.

[0015] Through the above technical solution, the evaluation method for the oxidation activity of crude oil proposed by the present invention is based on the oxidation kinetics curve results of each group of crude oil and / or narrow fraction oil obtained from the oxidation kinetics tests of multiple groups of crude oil, and re-divides the oxidation process of crude oil into three specific processes: low-temperature oxidation process, negative temperature coefficient oxidation process, and high-temperature oxidation process. The negative temperature coefficient oxidation process refers to the process of the ignition delay interval where the reaction rate decreases with the increase of temperature, and thus can reflect the process of crude oil at a temperature higher than the ignition temperature but not burning. The present invention further obtains the reaction equations occurring in each of the three specific processes through simulation analysis to approximately describe the reaction process. Then, by comparing the reaction equation occurring in the crude oil to be evaluated with the reaction equations occurring in the three specific processes, the specific oxidation activity type of the crude oil to be evaluated is determined, which can provide a more reasonable measure direction for further improving the oxidation activity of the crude oil to be evaluated.

[0016] The present invention further provides a method for improving the oxidation activity of crude oil in air injection production. First, the oxidation activity of the crude oil to be tested is judged according to the above evaluation method. The oxidation activity of the crude oil may be in three situations - "good oil" and "non-good oil", where type I oil is "good oil", and type II oil and type III oil are "non-good oil". According to the judgment result, corresponding measures are taken for the specific type of non-good oil of the crude oil to be tested to improve the oxidation activity of the crude oil to be tested. The present invention analyzes the oxidation activity of the crude oil to be tested from a new and reasonable perspective and takes targeted measures to improve the oxidation activity of the crude oil to be tested by increasing the heat of the crude oil and adding additives rich in active components respectively, so that the oxidation activity of the heavy oil meets the requirement of crossing the ignition delay interval and successfully enters the high-temperature oxidation process, avoiding the occurrence of pore blockage phenomenon, and avoiding ignition failure due to too long ignition delay time, and establishing a general control strategy for the conversion from low-temperature oxidation to high-temperature oxidation, thereby greatly improving the air injection production efficiency. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 FIG. is a schematic diagram of the three-stage oxidation mode distribution of crude oil including three specific processes: low-temperature oxidation process, negative temperature coefficient oxidation process, and high-temperature oxidation process, proposed for an embodiment of the present invention;

[0018] Figure 2a 、 Figure 2b 、 Figure 2c 、 Figure 2d and Figure 2e are respectively the pressure change curves at temperatures of 674 - 684K, 710 - 723K, 730 - 740K, 757 - 771K, and 829 - 850K during the oxidation reaction process of the <100°C low-boiling fraction oil of common heavy oil;

[0019] Figure 3a 、 Figure 3b 、 Figure 3c and Figure 3d are respectively the pressure change curves at temperatures of 698 - 712K, 737 - 761K, 774 - 790K, and 829 - 850K during the oxidation reaction process of the fraction oil with a distillation temperature of 100 - 125°C of common heavy oil;

[0020] Figure 4a 、 Figure 4b 、 Figure 4c and Figure 4dThey are respectively the pressure change curves at temperatures of 798 - 815K, 815 - 825K, 825 - 843K, and 860 - 878K during the oxidation reaction process of the fraction oil with a distillation temperature of 125 - 150℃ of ordinary heavy oil;

[0021] Figure 5a and Figure 5b and Figure 5c and Figure 5d They are respectively the pressure change curves at temperatures of 709 - 720K, 751 - 758K, 784 - 794K, and 840 - 853K during the oxidation reaction process of the fraction oil with a distillation temperature of 175 - 200℃ of ordinary heavy oil;

[0022] Figure 6a and Figure 6b and Figure 6c and Figure 6d They are respectively the pressure change curves at temperatures of 823 - 840K, 840 - 850K, 849 - 868K, and 885 - 903K during the oxidation reaction process of the fraction oil with a distillation temperature of 200 - 225℃ of ordinary heavy oil;

[0023] Figure 7a and Figure 7b and Figure 7c and Figure 7d They are respectively the pressure change curves at temperatures of 710 - 712K, 743 - 755K, 790 - 798K, and 841 - 868K during the oxidation reaction process of the fraction oil with a distillation temperature of 100 - 125℃ of Xinjiang No.1 extra - heavy oil;

[0024] Figure 8a and Figure 8b They are respectively the pressure change curves at temperatures of 871 - 890K and 966 - 982K during the oxidation reaction process of the fraction oil with a distillation temperature of 125 - 150℃ of Xinjiang No.1 extra - heavy oil;

[0025] Figure 9a and Figure 9b They are respectively the pressure change curves at temperatures of 814 - 829K and 871 - 890K during the oxidation reaction process of the fraction oil with a distillation temperature of 150 - 175℃ of Xinjiang No.1 extra - heavy oil;

[0026] Figure 10a and Figure 10b andFigure 10c and Figure 10d are respectively the pressure change curves at temperatures of 812 - 826K, 857 - 877K, 913 - 930K, and 983 - 994K during the oxidation reaction process of the distillate oil with a distillation temperature of 175 - 200℃ of Xinjiang No. 1 extra-heavy oil;

[0027] Figure 11a 、 Figure 11b and Figure 11c are respectively the pressure change curves at temperatures of 855 - 877K, 909 - 915K, and 960 - 982K during the oxidation reaction process of the distillate oil with a distillation temperature of 200 - 225℃ of Xinjiang No. 2 extra-heavy oil;

[0028] Figure 12 is the ARC experimental result graph of the distillate oil with a distillation temperature of 425 - 450℃ of Xinjiang No. 2 extra-heavy oil;

[0029] Figure 13 is the ARC experimental result graph of the vacuum residue of Xinjiang No. 2 extra-heavy oil;

[0030] Figure 14 is the ARC experimental result graph of Xinjiang No. 2 extra-heavy oil. Specific Embodiments

[0031] The following details the specific embodiments of the present invention. It should be understood that the specific embodiments described herein are only for the purpose of illustrating and explaining the present invention, and are not used to limit the present invention.

[0032] The first aspect of the present invention provides a method for evaluating the oxidation activity of crude oil, and the evaluation method includes:

[0033] S1. Collect multiple groups of crude oil;

[0034] In the present invention, three groups of crude oil from Liaohe and Xinjiang oil regions are collected. Among them, the ordinary heavy oil collected from the Liaohe oil region has a ground degassed oil viscosity of 540 mPa·s and has a certain flow ability in the oil layer; the No. 1 extra-heavy oil collected from the Xinjiang oil region has a ground degassed oil viscosity of 5900 mPa·s and basically has no flow ability in the oil layer; the No. 2 extra-heavy oil collected from the Xinjiang oil region has a ground degassed oil viscosity of 21000 mPa·s and has no flow ability in the oil layer at all and needs to be heated to flow. The three kinds of heavy oil belong to ordinary heavy oil and extra-heavy oil respectively, and have good representativeness for the domestic heavy oil that is currently in the middle and late stages of steam injection development.

[0035] S2. Conduct oxidation kinetic tests on the multiple groups of crude oils to obtain the oxidation kinetic curves of each group of crude oils respectively. Among them, the oxidation kinetic curves of each group of crude oils include the pressure change curves at different temperatures (as shown in Figure 2a - 11c ), and the change curves of the heating rate with temperature (as shown in Figure 12 - 14 ).

[0036] Most of the traditional experimental research equipment for crude oil oxidation kinetics is an accelerating calorimeter (ARC), TGA, DSC, combustion tube, etc. The results obtained are some lumped kinetic parameters, which cannot reflect the oxidation and combustion characteristics of crude oil with complex components and the process and intermediate process of the mixture at different temperatures and pressures. Obviously, it is difficult to display and analyze the process of technology application by simply applying these parameters, and it is even more impossible to grasp the key reaction links of the technology and carry out regulation research.

[0037] Ignition and combustion are fast reaction processes with strong light emission and heat release. Their experimental research has high costs, complex technologies, and difficult measurements. With the development of technology and the improvement of combustion requirements, the existing semi-empirical and empirical methods cannot meet the current needs. The Rapid Compression Machine (RCM) has outstanding advantages in the research fields of combustion characteristic mechanisms such as the influencing factors of fuel flame propagation, product formation mechanisms, ignition delay, component concentration changes, and verification of combustion models. The present invention adopts this mechanism research equipment.

[0038] Figure 2a - Figure 6d The pressure changes at different temperatures during the oxidation reaction of different narrow fraction oils obtained by conducting oxidation kinetic tests on Liaohe common heavy oil through a rapid compression machine.

[0039] Figure 7a - 10d The pressure changes at different temperatures during the oxidation reaction of different narrow fraction oils obtained by conducting oxidation kinetic tests on Xinjiang No. 1 extra heavy oil through a rapid compression machine.

[0040] Figure 11a - Figure 11c The pressure changes at different temperatures during the oxidation reaction of the 200 - 225 °C fraction oil of Xinjiang No. 2 extra heavy oil obtained by conducting oxidation kinetic tests through a rapid compression machine.

[0041] Taking Figure 2a as an example to illustrate, Figure 2a is the pressure - time change curve at 674 - 684K during the oxidation reaction process of the <100 °C low fraction oil of common heavy oil, corresponding to Example 1 in Table 1. This curve was detected under the experimental conditions of an equivalence ratio of 1, 20 bar, and T0 = 20 °C. Figure 2aFour curves are shown, which are curves formed at four temperature points of 674K, 678K, 681K, and 684K in the range of 674 - 684K. These four curves, from top to bottom, are the curves of the pressure change with time of conventional heavy oil <100℃ light distillate oil at 674K, 678K, 681K, and 684K. From Figure 2a It can be seen that the trends of these four curves in the temperature range of 674 - 684K are similar. From Figure 2, the low-temperature oxidation reaction process, high-temperature oxidation reaction process, and negative temperature coefficient oxidation process between them of this distillate oil can be clearly seen, and an obvious ignition delay phenomenon appears. It can be clearly seen from Figure 2 that there are turning points of the curves. The first turning point appears at 0.05ms, and the second turning point appears at 0.11 - 0.17. The second turning points of different curves are different, but they all have obvious turns. Taking the curve of the pressure change with time formed at 674K as an example, the 0 - 0.05ms section of the abscissa is the low-temperature oxidation reaction process, the 0.05ms - 0.11ms section is the negative temperature coefficient oxidation process, and the 0.11ms - 0.13ms section is the high-temperature oxidation reaction process. Therefore, according to the above first and second turning points, the oxidation process of crude oil can be divided into three specific processes.

[0042] Figure 2b - Figure 11c Please refer to Figure 2a for the explanation, which will not be elaborated here.

[0043] Figure 2a - Figure 11c In the figure, TDC refers to the top dead center shown by the experimental equipment. When the piston makes a reciprocating linear motion in the cylinder, when the piston moves upward to the highest position and the maximum distance from the piston top to the center of the crankshaft is reached, this position is called the top dead center.

[0044] Limited by the fact that the current rapid compressor has a limit on the distillation temperature of the experimental oil products not exceeding 300℃, for the oil products that cannot be experimented with by the rapid compressor, an adiabatic accelerating calorimeter (ARC) is used for research. To ensure the continuity and comparability of the research, for the marginal oil products experimented with by the rapid compressor, under the same temperature and pressure control conditions, ARC is used for comparative experiments to ensure the comparability of the crude oil experiments of the two experimental equipment.

[0045] Constrained by the fact that traditional crude oil oxidation kinetics experimental equipment can only study lumped kinetic parameters and cannot study the key substances and key reactions during the oxidation kinetic reaction of crude oil. With the help of a rapid compressor, three groups of crude oils from Liaohe and Xinjiang oil regions were collected, and the research on the oxidation kinetic mechanism of narrow distillate oils with different distillation ranges and crude oil was carried out.

[0046] Limited by the properties of experimental oils of current rapid compressors, high-viscosity fuels cannot be experimentally studied using rapid compressors. For the other narrow-fraction oils of No. 2 extra-heavy oil that cannot be experimentally studied using rapid compressors, an adiabatic accelerating calorimeter (ARC) was used to study the lumped characteristics of oxidation kinetics.

[0047] To ensure the continuity and comparability of the research, first, a comparative experiment was carried out on narrow-fraction oils of ordinary heavy oil with three-stage oxidation characteristics using ARC and a rapid compressor under the same temperature and pressure control conditions. The same three-stage oxidation phenomenon was obtained, and after confirming the comparability of the two experimental devices for crude oil experiments, ARC experiments were carried out on the 425-450 °C fraction with a distillation yield of No. 2 extra-heavy oil greater than, the residue oil with a distillation temperature greater than 505 °C, and the crude oil.

[0048] Figure 12 - Figure 14 They are the ARC experimental results of the 425-450 °C fraction, residue oil, and crude oil respectively, and all three groups of oils showed three-stage oxidation characteristics.

[0049] Take Figure 12 as an example to illustrate. The 425-450 °C fraction of No. 2 extra-heavy oil had low-temperature heat release at 150-180 °C, high-temperature heat release started at 200 °C, and there was a weak ignition delay phenomenon between 180-200 °C, and the temperature range of the ignition delay phenomenon was relatively narrow. Therefore, the temperature ranges of 150-180 °C, 180-200 °C, and above 200 °C were the low-temperature oxidation process, negative temperature coefficient oxidation process, and high-temperature oxidation process of No. 2 extra-heavy oil respectively.

[0050] S3. According to the above-mentioned multiple groups of oxidation kinetic curves, through analysis, the oxidation process of crude oil was divided into three specific processes: low-temperature oxidation process, negative temperature coefficient oxidation process, and high-temperature oxidation process. Among them, the negative temperature coefficient oxidation process was the oxidation process in the ignition delay interval where the system reaction rate decreased with the increase of temperature. And the reaction equations occurring in each of the three specific processes were obtained through simulation analysis; preferably, the reaction equations occurring in each of the three specific processes were obtained through simulation analysis using Chemkin software;

[0051] The reaction equations occurring in the negative temperature coefficient oxidation process and the high-temperature and low-temperature oxidation processes were analyzed through simulation analysis using Chemkin software as follows:

[0052] The inventors found through a large number of studies that there are a large number of straight-chain and branched-chain alkanes, cycloalkanes, alkenes, aromatic hydrocarbons and other components in crude oil, and the number of carbon atoms is unknown, and the oxidation reaction paths and their macroscopic characteristics of different components are also different. Generally speaking, as a mixture of hydrocarbon fuels, the oxidation reaction of crude oil can be divided into the following types of reactions:

[0053] The initial reaction is the dehydrogenation of fuel molecule R to form fuel radical R', and the dehydrogenation reaction of fuel molecule with oxygen molecule to form fuel radical R', that is

[0054] ①RH → H + R'; RH + O2 → R' + HO2

[0055] Among them, R' is the fuel radical, and HO2 and O2 will continue to participate in dehydrogenation to establish a radical pool, which includes O, N, OH, HO2, CH3, C2H3, etc.

[0056] ②R' + O2 → R'O2

[0057] The fuel radical R' undergoes an addition reaction at medium and low temperatures; since the potential energy position of R'O2 is relatively low, that is, the activation barrier of this reaction is low, so the reaction is very likely to occur.

[0058] ③R'O2 → R”OOH

[0059] At medium and low temperatures, R'O2 undergoes hydrogen atom transfer through a transition state and isomerizes to R”OOH through a single hydrogenation reaction. Since the activation barrier of the six-membered ring transition state is relatively low, hydrogen atom transfer as shown in the following figure with heptyl fuel as an example is likely to occur:

[0060]

[0061] ④R”OOH → olefin, cyclic ether, aldehyde + OH

[0062] The R”OOH generated in the above reaction can undergo three types of reactions. One is the cleavage reaction of R”OOH, such as the β cleavage occurring in the above two equations:

[0063]

[0064] Or:

[0065]

[0066] The ethers, aldehydes, and olefins generated in the above reaction, together with the ketones generated in the following reaction, are very good organic solvents. Once a large amount of olefins, aldehydes, and ethers are generated during the combustion process, when they are miscible with the macromolecular hydrocarbon components, if the system temperature decreases (low-temperature reaction or the external heat input is less than the heat released to the outside), then the phenomenon of gum formation occurs and oil displacement cannot occur.

[0067] ⑤R”OOH + O2 → O2R”OOH

[0068] R″OOH undergoes a secondary oxygen addition reaction to obtain O2R”OOH, such as continuing to add oxygen molecules as shown in Equation (2):

[0069]

[0070] ⑥O2R”OOH → HOOR”’OOH

[0071] O2R”OOH undergoes a secondary hydrogenation reaction to isomerize into HOOR”’OOH;

[0072] ⑦HOOR”’OOH → OR”’O + 2OH

[0073] HOOR”’OOH undergoes a cracking reaction to form a ketone and two OH active groups.

[0074] In the series of reactions ① - ⑦ above, three OHs, aldehydes, ketones, and ethers are formed. On the one hand, the strong activity of OH can continue to cause system reactions, accelerating the reaction, further oxidizing the fuel, releasing heat, and increasing the system temperature; for the actual reaction process, ethers and aldehydes dissolve the high-molecular crude oil components, increasing the heat dissipation of the system. If the low-temperature heat release and / or the heat injected into the system is less than the heat dissipation, the temperature decreases, and the oil layer gels. This is the first reason for the failure of oil displacement.

[0075] ⑧R’ → small molecules

[0076] If in the above reactions, the heat release of the system is greater than the external heat dissipation, the reaction continues. As the temperature gradually increases, the rates of reactions (3) and (4) increase, while the rates of the secondary hydrogenation reaction and the isomerization reaction decrease, that is, the concentration of OH decreases. At this time, it enters the negative temperature coefficient reaction process, that is, the negative temperature coefficient (Negative Temperature Coefficient, NTC) interval, also known as the ignition delay interval. In this negative temperature coefficient (NTC) interval, the reaction rate decreases with the increase in temperature. In addition, during this period, after the temperature rises, the fuel radical R’ can directly crack into small molecule stable unsaturated olefins, which becomes a competitive reaction with the first hydrogenation reaction, further reducing the reaction rate. If the NTC duration is too long and the temperature decreases and the OH concentration is too low, it will lead to the inability to break through the NTC interval. This is the second reason for the failure of fire flooding.

[0077] ⑨H + O2 → O + OH

[0078] ⑩CO + O → CO2

[0079] In the ignition delay interval (NTC interval), if the OH concentration is too low or the reaction heat release is lower than the external heat dissipation, then the entire system will not be able to break through the NTC constraint, the chain reaction will be interrupted, and only low-temperature reactions will occur without high-temperature reactions. If the NTC duration is appropriate, the OH concentration is appropriate, or the reaction heat release is higher than the external heat dissipation, the reaction can enter the high-temperature oxidation process.

[0080] In the above reaction, ① is the initial reaction; ② - ⑦ are oxygen addition and isomerization reactions under medium and low temperature conditions. During this period, most of the R”OOH undergoes cleavage to generate olefins, cyclic ethers, aldehydes, and an OH active group. Among them, ② - ④ are chain propagation reactions. In reactions ⑤ - ⑦, R”OOH undergoes secondary oxygen addition and isomerization reactions to generate ketones and 2 OHs, which belong to chain branching reactions and can accelerate the system reaction. As the temperature increases, reaction ⑧ and ② become competitive reactions, the concentration of OH groups in the system decreases, the reaction rate decreases, and a ignition delay phenomenon (also known as the negative temperature coefficient phenomenon, i.e., the NTC phenomenon) appears. ⑨ - ⑩ are high temperature reactions.

[0081] Based on the above reactions, the oxidation reactions occurring in each of the three specific processes are obtained; among them,

[0082] The following reactions mainly occur in the low temperature oxidation process:

[0083] ① RH → H + R’; RH + O2 → R’ + HO2;

[0084] ② R’ + O2 → R’O2;

[0085] The following reactions mainly occur in the negative temperature coefficient oxidation process:

[0086] ② R’ + O2 → R’O2;

[0087] ③ R’O2 → R”OOH;

[0088] ④ R”OOH → olefins, cyclic ethers, aldehydes + OH;

[0089] ⑤ R”OOH + O2 → O2R”OOH;

[0090] ⑥ O2R”OOH → HOOR”’OOH;

[0091] ⑦ HOOR”’OOH → OR”’O + 2OH;

[0092] ⑧ R’ → small molecules;

[0093] The following reactions mainly occur in the high temperature oxidation process:

[0094] ⑨ H + O2 → O + OH

[0095] ⑩ CO + O → CO2.

[0096] The present invention divides the oxidation mode of crude oil into three specific processes: low-temperature oxidation process, negative temperature coefficient oxidation process, and high-temperature oxidation process. Among them, the low-temperature oxidation process refers to the oxidation process in which the crude oil undergoes preliminary reactions and produces some carbon monoxide products; the negative temperature coefficient oxidation process refers to the oxidation process in the ignition delay interval where the reaction rate of the system decreases with the increase in temperature. If the crude oil has oxidation activity across the ignition delay interval, the crude oil can bypass the negative temperature coefficient oxidation process and enter the high-temperature oxidation process; the high-temperature oxidation process refers to the process of a series of oxidation reactions that occur after the crude oil catches fire, characterized by a sudden increase in temperature, a very fast rising speed, and a significant increase in pressure. Compared with the incomplete combustion characteristics in the low-temperature oxidation and negative temperature coefficient oxidation processes, the combustion in the high-temperature oxidation process is more complete.

[0097] Specifically, the oxidation kinetic test results of Liaohe common heavy oil, Xinjiang No. 1 and No. 2 extra-heavy oils, and their narrow fractions are as follows.

[0098] 1. Oxidation kinetic test of Liaohe common heavy oil

[0099] The experimental results of the oxidation kinetics test of Liaohe common heavy oil are as Figure 2a - Figure 6d shown in Table 1.

[0100] As Figure 2a - Figure 2e shown, it is the oxidation kinetic reaction of the <100°C low fraction of common heavy oil tested by a rapid compressor. It can be clearly seen from Figure 2 the low-temperature oxidation reaction, high-temperature oxidation reaction, and the negative temperature coefficient oxidation process in between of this fraction oil, and an obvious ignition delay phenomenon appears.

[0101] As Figure 3a - Figure 3d shown, it is the oxidation kinetic test results of the fraction oil of common heavy oil in the temperature range of 100 - 125°C. It can be seen that the three-stage oxidation kinetic characteristics of the 100 - 125°C fraction oil are obvious, including low-temperature oxidation reaction, negative temperature coefficient oxidation process, and high-temperature oxidation reaction, and an obvious ignition delay phenomenon appears in the medium-temperature oxidation.

[0102] As Figure 4a - Figure 4d shown, it is the oxidation kinetic test results of the fraction oil of common heavy oil in the range of 125 - 150°C. This fraction oil has no obvious ignition delay phenomenon, relatively weak reaction activity, a higher ignition temperature, and obvious ignition only occurs above 800K.

[0103] As Figure 5a - Figure 5d 、 Figure 6a - Figure 6d shown are the oxidation kinetic test results of the fraction oils of common heavy oil in the ranges of 175 - 200°C and 200 - 225°C respectively. By comparison, the 175 - 200°C fraction oil shows obvious three-stage oxidation characteristics; while the 200 - 225°C fraction oil has weak reaction activity, no obvious ignition delay phenomenon, a higher ignition temperature, and obvious ignition only occurs above 825K.

[0104] Table 1 summarizes the test results of ordinary heavy oil narrow fractions using a rapid compressor. Among the six groups of narrow fraction oil experiments, three groups showed obvious three-stage oxidation characteristics.

[0105] Table 1 Oxidation Kinetics Test Results of Ordinary Heavy Oil Narrow Fractions

[0106]

[0107] Note: The above experimental conditions were all carried out at T0 = 20°C. The equivalence ratio refers to the molar ratio of air to narrow fraction oil.

[0108] 2. Oxidation Kinetics Test of Xinjiang No. 1 Extra Heavy Oil

[0109] The oxidation kinetics experimental results of Xinjiang No. 1 extra heavy oil are as Figure 7a - Figure 10d shown in Table 2.

[0110] As Figure 7a - Figure 7d shown, it is the oxidation kinetics reaction of the 100 - 125°C fraction of Xinjiang No. 1 extra heavy oil tested by a rapid compressor. It can be clearly seen from Figure 7 that the ignition delay duration of this fraction oil is long, and the low-temperature oxidation reaction, high-temperature oxidation reaction, and the negative temperature coefficient oxidation process between them (an obvious ignition delay phenomenon appears) - the three-stage oxidation characteristics are obvious. In the on-site production of oilfields, if this fraction oil participates in the air injection oxidation process and the chemical reaction of the negative temperature coefficient oxidation process is not considered, then an inexplicable "negative temperature coefficient interval" will appear, and the relevant designs and controls carried out will also be difficult to achieve the expected results.

[0111] As Figure 8a and Figure 8b shown, it is the oxidation kinetics reaction of the 125 - 150°C fraction of Xinjiang No. 1 extra heavy oil tested by a rapid compressor. The ignition delay duration of this fraction oil is long, and the high-temperature combustion appears after a long ignition delay.

[0112] As Figure 9a and Figure 9b shown, it is the test result of the oxidation reaction of the 150 - 175°C fraction of Xinjiang No. 1 extra heavy oil using a rapid compressor. This fraction oil has a fast combustion speed, a high peak pressure, an obvious ignition delay phenomenon, and significant three-stage oxidation characteristics.

[0113] As Figure 10a - Figure 10d shown, it is the test result of the oxidation reaction of the 175 - 200°C fraction of Xinjiang No. 1 extra heavy oil. Compared with the oxidation reaction characteristics of the previous 3 groups of Xinjiang No. 1 extra heavy oil fractions, this fraction oil has a slow combustion speed, a not high peak pressure, and an insignificant three-stage ignition delay phenomenon.

[0114] Table 2 shows the statistical results of the experimental study on the oxidation reaction of narrow fraction oils with different distillation temperatures of Xinjiang No. 1 extra-heavy oil tested by a rapid compressor. In the five groups of narrow fraction oil experiments, two groups showed obvious three-stage oxidation kinetic characteristics.

[0115] Table 2 Oxidation Kinetic Test Results of Narrow Fraction Oils of Xinjiang No. 1 Extra-Heavy Oil

[0116]

[0117] Note: The above experimental conditions were all carried out at T0 = 20°C. The equivalence ratio refers to the molar ratio of air to narrow fraction oil;

[0118] 3. Oxidation Kinetic Test of Xinjiang No. 2 Extra-Heavy Oil

[0119] As Figure 11a - Figure 11c shown, it is the oxidation kinetic test result of the 200-225°C fraction oil of Xinjiang No. 2 extra-heavy oil. The 200-225°C fraction of this crude oil does not have the NTC phenomenon. Due to the small distillation yield, the 225-250°C fraction oil cannot be judged.

[0120] Xinjiang No. 2 extra-heavy oil has almost no fraction below 200°C, and there are only a small amount of fractions in the two distillation temperature ranges of 200-225°C and 225-250°C.

[0121] Due to the limitations of the current rapid compressor on the properties of experimental oils, high-viscosity fuels cannot be experimented with using a rapid compressor. For the other narrow fraction oils of Xinjiang No. 2 extra-heavy oil that cannot be experimented with by a rapid compressor, an adiabatic accelerating calorimeter (ARC) was used to study the lumped characteristics of oxidation kinetics.

[0122] To ensure the continuity and comparability of the research, first, for the narrow fraction oils of ordinary heavy oil with three-stage oxidation characteristics, under the same temperature and pressure control conditions, comparative experiments were carried out using ARC and a rapid compressor, and the same three-stage oxidation phenomenon was obtained. After confirming the comparability of the two experimental devices for crude oil experiments, ARC experiments were carried out on the 425-450°C fraction with a distillation yield greater than that of Xinjiang No. 2 extra-heavy oil, the residue oil with a distillation temperature greater than 505°C, and the crude oil.

[0123] Figure 12 - Figure 14 They are the ARC experimental results of the 425-450°C fraction, residue oil, and crude oil respectively. All three groups of oils showed three-stage oxidation characteristics. Among them, the 425-450°C fraction had low-temperature heat release at 150-180°C, high-temperature heat release started at 200°C, and there was a weak ignition delay phenomenon between 180-200°C, and the continuous temperature range of the ignition delay phenomenon was relatively narrow; the residue oil had a strong low-temperature reaction and a strong ignition delay phenomenon, and obvious high-temperature reaction was only seen after 350°C. The low-temperature oxidation heat release of the crude oil was at 170-230°C, while the high-temperature heat release started at 350°C, and the continuous temperature range of the ignition delay phenomenon was relatively wide.

[0124] Through the analysis of Figure 2a - Figure 14 it can be known that:

[0125] (1) The ignition characteristics of common heavy oil, extra-heavy oil and their narrow fractions taken from 2 oil regions and 3 different oil reservoirs vary greatly.

[0126] (2) Among the 15 groups of oil samples for which experiments have been carried out, the experimental results of 8 groups show oxidation characteristics of a three-stage / three specific processes.

[0127] (3) A large number of mechanism experiments have clarified the universality of NTC in the oxidation process of crude oil, that is, there are three reaction intervals in the oxidation process of crude oil - low-temperature oxidation interval, high-temperature oxidation interval and negative temperature coefficient oxidation interval. Therefore, the oxidation process of crude oil is divided into low-temperature oxidation process, negative temperature coefficient oxidation process and high-temperature oxidation process. The negative temperature coefficient oxidation process is the critical turning point between the low-temperature oxidation process and the high-temperature oxidation process. The negative temperature coefficient oxidation process is the oxidation process in the ignition delay interval where the system reaction rate decreases with the increase of temperature.

[0128] S4. Conduct oxidation kinetic tests on the oxidation of the crude oil to be evaluated, and obtain the reaction equation occurring in the crude oil to be evaluated through simulation analysis; preferably, obtain the reaction equation occurring in the crude oil to be evaluated through simulation analysis by Chemkin software;

[0129] S5. Judge the oxidation activity of the crude oil to be evaluated according to the correlation between the reaction equation occurring in the crude oil to be evaluated and the reaction equations occurring in the respective three specific processes.

[0130] In step S1 of the present invention, the multiple groups of crude oil include at least one of common heavy oil, super heavy oil and extra-heavy oil.

[0131] In order to make the experimental results more accurate, the embodiments of the present application have respectively carried out oxidation kinetic tests on common heavy oil, super heavy oil and extra-heavy oil.

[0132] In step S2 of the present invention, a rapid compressor and / or an accelerating calorimeter are used to carry out oxidation kinetic tests on the multiple groups of crude oil;

[0133] Preferably, a rapid compressor and / or an accelerating calorimeter are used to carry out oxidation kinetic tests on each group of crude oil and / or the narrow fractions of each group of crude oil with different distillation ranges.

[0134] The present invention obtains an oxidation reaction process curve by testing the oxidation process of the multiple groups of crude oil; wherein, the oxidation reaction process curve includes a pressure change curve at different temperatures and a change curve of the heating rate with temperature.

[0135] In step S3 of the present invention, according to the oxidation reaction progress curve, the oxidation mode of the crude oil is divided into three specific processes: low-temperature oxidation process, negative temperature coefficient oxidation process, and high-temperature oxidation process. As Figure 1 shown, it is a three-stage oxidation mode distribution diagram of the crude oil including three specific processes: low-temperature oxidation process, negative temperature coefficient oxidation process, and high-temperature oxidation process proposed in an embodiment of the present invention; from Figure 1 it can be seen that the negative temperature coefficient oxidation process is the critical turning point between the low-temperature oxidation process and the high-temperature oxidation process. The negative temperature coefficient oxidation process is the oxidation process in the ignition delay interval where the system reaction rate decreases with the increase of temperature. If the three-stage oxidation characteristics are obvious, that is, the negative temperature coefficient oxidation process lasts longer and the ignition delay phenomenon is obvious.

[0136] In step S4 of the present invention, the oxidation process of the crude oil to be evaluated is tested, and the oxidation reaction occurring in the oxidation process is obtained through simulation analysis by Chemkin software;

[0137] In step S5 of the present invention, the process of judging the oxidation activity of the crude oil to be evaluated includes the following situations:

[0138] If the crude oil to be evaluated undergoes reactions ①-⑩, it is judged that the crude oil to be evaluated is type I oil. Among them, the type I oil has three specific processes: low-temperature oxidation process, negative temperature coefficient oxidation process, and high-temperature oxidation process. The oxidation activity of the type I oil is medium and it is easy to catch fire;

[0139] If the crude oil to be evaluated undergoes reactions ①-⑧, and reactions ②-⑧ occur repeatedly and then stop; or reactions ⑨ and ⑩ occur after reactions ②-⑧ occur repeatedly, it is judged that the crude oil to be evaluated is type II oil. Among them, the type II oil has three specific processes: low-temperature oxidation process, negative temperature coefficient oxidation process, and high-temperature oxidation process. The oxidation activity of the type II oil is strong and the ignition delay time is long;

[0140] If the crude oil to be evaluated undergoes reactions ① and ②, then enters reactions ⑨ and ⑩, and then stops, and reactions ① and ② and reactions ⑨ and ⑩ must be raised to a higher temperature again before they can occur again, it is judged that the crude oil to be evaluated is type III oil. Among them, the type III oil does not have three specific processes. The oxidation activity of the type III oil is weak and it is difficult to catch fire.

[0141] In the present invention, type I oil is defined as "good oil"; type II oil is defined as "non-good oil"; type III oil is defined as "non-good oil".

[0142] The evaluation method of the present invention can be used to judge the oxidation process of crude oil, and the actual crude oil exploitation process can be guided according to the judgment result. Therefore, it is particularly important to judge whether the oxidation activity of the crude oil in the oil production well meets the above three specific processes and whether it has the oxidation activity to cross the ignition delay interval to successfully enter the high-temperature oxidation process before exploitation.

[0143] Furthermore, on the basis of clarifying that the negative temperature coefficient oxidation process is the oxidation process in the ignition delay interval where the system reaction rate decreases with the increase of temperature, the exploitation conditions are controlled by the requirements that whether the oxidation process of the crude oil in the oil production well meets the three specific processes and whether it has the oxidation activity to cross the ignition delay interval to successfully enter the high-temperature oxidation process, so as to improve the exploitation efficiency of crude oil.

[0144] The second aspect of the present invention provides a method for improving the oxidation activity of crude oil, and the method includes:

[0145] Judge the oxidation activity of crude oil according to the evaluation method described in any one of the foregoing;

[0146] According to the judgment result of the oxidation activity of the crude oil, take corresponding measures to improve the oxidation activity of the crude oil.

[0147] The judgment of the oxidation activity of crude oil has been described in detail in the foregoing evaluation method, and will not be repeated here. For details, please refer to the description of the evaluation method for the oxidation activity of crude oil provided in the first aspect of the present invention.

[0148] According to the judgment result of the oxidation activity of the crude oil, take corresponding measures to improve the oxidation activity of the crude oil.

[0149] In some embodiments, when the crude oil to be tested is type I oil in the judgment result, since the oxidation activity of type I oil is medium and it is easy to catch fire, that is, it belongs to "good oil", no additional measures need to be taken.

[0150] In other embodiments, when the crude oil to be tested is type II oil in the judgment result, that is, "non-good oil", the measure is to increase the heat of the crude oil to be tested. For type II oil, since the oxidation activity of type II oil is strong and the ignition delay time is long, the way of increasing heat can be adopted to shorten the ignition delay time and improve the oxidation activity of crude oil.

[0151] The present invention does not limit the way of applying heat. In principle, as long as it can increase the system heat, it can be used in the present invention.

[0152] As a preferred embodiment, the way of increasing the heat of the crude oil to be tested is the self-heating material for in-situ heat generation underground. For example, the self-heating material is a substance whose key components contain reduced iron powder, activated carbon and salt.

[0153] In still other embodiments, when in the determination result, the crude oil to be tested is Class III oil, that is, "non-good oil", the measure is to add a first additive rich in active components and / or a second additive that can promote the chain reaction for generating active groups to the crude oil to be tested. For Class III oil, due to its weak oxidation activity and difficulty in ignition, it is very difficult to improve its oxidation activity by simply applying heat. The method of adding additives can be adopted to improve the oxidation activity of the crude oil.

[0154] The first additive rich in active components added in the present invention promotes combustion mainly by increasing the form of active groups. The active components mainly refer to OH free radicals, and the specific form is not limited. In principle, any substance that can increase OH free radicals can be selected.

[0155] In some preferred embodiments, the first additive is a substance containing rich active groups.

[0156] Further preferably, the first additive is selected from at least one of a substance containing an OH group, a substance that can release an OH group upon heating, and a substance that can release an OH group upon reaction, so as to increase the OH groups in the reaction.

[0157] In some preferred embodiments, the second additive is a substance that can promote the chain reaction for generating active groups in the crude oil to be tested.

[0158] The present invention does not specifically limit the second additive. Any substance that can promote the chain reaction for generating active groups in the crude oil to be tested can be selected. For example, hydrogenation catalysts, isomerization catalysts, etc. In the present invention, the chain reaction for generating active groups can be a reaction that occurs during the oxidation process of the crude oil, such as reactions ② - ⑦ in the aforementioned reactions ① - ⑩. Among them, reactions ② - ④ are the primary oxygen addition and isomerization reactions of the fuel group R', generating aldehydes, ketones, ethers, and one OH active group. In reactions ⑤ - ⑦, R"OOH undergoes secondary oxygen addition and isomerization reactions to generate ketones and 2 OHs, which belong to chain branching reactions and can accelerate the system reaction.

[0159] The first additives that meet the above conditions include, but are not limited to: hydrogen peroxide, a mixture of ferrocene and hydrogen peroxide, a mixture of isooctyl nitrate and dimethylaminferrocene, etc.

[0160] Based on clarifying the chemical kinetic mechanism in the process of heavy oil oxidation enhanced oil recovery, the present invention divides the crude oil oxidation process into three specific processes. Based on this, by analyzing the oxidation activity of the crude oil at the production site, it is determined whether its oxidation activity meets the conditions that its oxidation reaction process conforms to the three specific processes and whether it has the ability to cross the ignition delay interval to successfully enter the high-temperature oxidation process as the reservoir screening conditions. Thus, a targeted control production method is achieved, and pore blockage is avoided, as well as ignition failure caused by too long ignition delay time. A general control strategy for the conversion from low-temperature oxidation to high-temperature oxidation is established to improve the efficiency of air injection enhanced oil recovery.

[0161] To further understand the present invention, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the protection scope of the present invention.

[0162] Unless otherwise specified, the reagents involved in the embodiments of the present invention are all commercially available products and can be obtained through commercial channels.

[0163] In the following embodiments:

[0164] The 1# crude oil from a well in Xinjiang, ordinary heavy oil, with a viscosity of 210 mPa·s;

[0165] The 2# crude oil from a well in Xinjiang, ordinary heavy oil, with a viscosity of 670 mPa·s;

[0166] The 3# crude oil from a well in Xinjiang, ordinary heavy oil, with a viscosity of 910 mPa·s.

[0167] According to the analysis results of the oxidation kinetic curves of the three groups of crude oils in the aforementioned Liaohe and Xinjiang oil regions, the oxidation mode of the crude oil is divided into three specific processes: low-temperature oxidation process, negative temperature coefficient oxidation process, and high-temperature oxidation process; and the reaction equations occurring in each of the three specific processes are obtained through simulation analysis by Chemkin software. For details, reference can be made to the foregoing, and it will not be elaborated here. Based on this, the following embodiments are used to evaluate the crude oil to be tested.

[0168] Example 1

[0169] Taking the 1# crude oil from a well in Xinjiang as the crude oil to be tested, evaluating the 1# crude oil according to the above method, and taking corresponding measures to improve the oxidation activity of the crude oil according to the evaluation results, including the following steps:

[0170] Step 1: Conduct oxidation kinetics tests on the 1# crude oil, and through simulation and analysis using Chemkin software, obtain the oxidation reactions occurring during the oxidation process of the 1# crude oil: Reactions ① - ⑧ occurred, and after repeating reactions ② - ⑧ multiple times, it stopped, or after repeating reactions ② - ⑧ multiple times, reactions ⑨ and ⑩ occurred.

[0171] Step 2: Based on the correlation between the oxidation reactions of the 1# crude oil and the reaction equations in the aforementioned three specific processes, determine the oxidation activity of the 1# crude oil: Reactions ① - ⑧ occurred, and after repeating reactions ② - ⑧ multiple times, it stopped, indicating that high-temperature reactions could not occur due to a long ignition delay time; if reactions ① - ⑧ occurred, and reactions ② - ⑧ were repeated multiple times, and reactions ⑨ and ⑩ occurred after repeating reactions ② - ⑧ multiple times, it indicates that there are three specific processes, but the fire delay time is long. Therefore, it is determined that the 1# crude oil is Class II oil with a long ignition delay time.

[0172] Step 3: According to the judgment result of Step 2, apply heat to the 1# crude oil by adding self-heating materials for in-situ underground heat generation to increase the system heat. The self-heating materials include 50 - 55% reduced Fe powder, 17 - 25% moisture, 5 - 8% NaCl, 3 - 9% activated carbon, 3 - 15% vermiculite, and 1 - 5% superabsorbent resin.

[0173] After testing, by applying heat, the ignition delay time of the 1# crude oil was shortened, and the oxidation activity of the 1# crude oil was improved.

[0174] Example 2

[0175] Taking the 2# crude oil from a certain well in Xinjiang as the crude oil to be tested, evaluate the 2# crude oil according to the above method, and a method for taking corresponding measures to improve the oxidation activity of the crude oil includes the following steps:

[0176] Step 1: Conduct oxidation kinetics tests on the 2# crude oil, and through simulation and analysis using Chemkin software, obtain the oxidation reactions occurring during the oxidation process of the 2# crude oil: Reactions ① - ⑩ occurred directly.

[0177] Step 2: Based on the correlation between the oxidation reactions of the 2# crude oil and the reaction equations in the aforementioned three specific processes, determine the oxidation activity of the 2# crude oil: Reactions ① - ⑩ occurred directly, indicating that three specific processes occurred and the ignition delay time was appropriate. It is determined that the crude oil is Class I oil with good oxidation activity and good ignition. There is no need to take corresponding measures to improve the oxidation activity of the 2# crude oil.

[0178] Example 3

[0179] Taking the 3# crude oil from a certain well in Xinjiang as the crude oil to be tested, evaluate the 3# crude oil according to the above method, and a method for taking corresponding measures to improve the oxidation activity of the crude oil includes the following steps:

[0180] Step 1: Conduct oxidation kinetics tests on the No. 3 crude oil, and through simulation and analysis using Chemkin software, obtain the oxidation reactions occurring during the oxidation process of the No. 3 crude oil: Reactions ① and ② occur, then enter Reactions ⑨ and ⑩, and then stop. It is necessary to raise the temperature again before Reactions ① and ②, and Reactions ⑨ and ⑩ can occur again.

[0181] Step 2: Judge the oxidation activity of the No. 3 crude oil based on the correlation between the oxidation reactions of the No. 3 crude oil and the reaction equations in the aforementioned three specific processes: Reactions ① and ② occur, then enter Reactions ⑨ and ⑩, indicating that the negative temperature coefficient oxidation process does not occur. Then stop, and it is necessary to raise the temperature again before Reactions ① and ②, and Reactions ⑨ and ⑩ can occur again, indicating that the reaction activity of the crude oil is weak and it is difficult to catch fire. Then it is judged that the crude oil is Class III oil, with low oxidation activity and difficult ignition.

[0182] Step 3: According to the judgment result of Step 2, add an additive rich in active ingredients to the No. 3 crude oil to increase the OH groups and improve the oxidation activity of the crude oil. The additive added is a mixture of isooctyl nitrate and dimethylaminodicyclopentadienyliron.

[0183] After testing, by adding the additive, the No. 3 crude oil also has three specific processes, and the oxidation activity of the No. 3 crude oil is improved.

[0184] The preferred embodiments of the present invention have been described in detail above. However, the present invention is not limited thereto. Within the scope of the technical concept of the present invention, various simple modifications can be made to the technical solutions of the present invention, including any other suitable combination of each technical feature. These simple modifications and combinations should also be regarded as the content disclosed by the present invention and fall within the protection scope of the present invention.

Claims

1. An evaluation method for the oxidation activity of crude oil, characterized in that, The evaluation method includes: S1. Collect multiple groups of crude oil; S2. Conduct oxidation kinetics tests on the multiple groups of crude oil respectively to obtain the oxidation kinetics curves of each group of crude oil; S3. According to the oxidation kinetics curves, divide the oxidation process of each group of crude oil into three specific processes: low-temperature oxidation process, negative temperature coefficient oxidation process, and high-temperature oxidation process, and obtain the reaction equations occurring in each of the three specific processes through simulation analysis; the reaction equations occurring in each of the three specific processes include: The following reactions mainly occur in the low-temperature oxidation process: ① RH→H+R’; RH+O2→R’+HO2; ② R’+O2→R’O2; The following reactions mainly occur in the negative temperature coefficient oxidation process: ② R’+O2→R’O2; ③ R’O2→R’’OOH; ④ R’’OOH→olefins, cyclic ethers, aldehydes + OH; ⑤ R’’OOH+O2→O2R’’OOH; ⑥ O2R’’OOH→HOOR’’’OOH; ⑦ HOOR’’’OOH→OR’’’O+2OH; ⑧ R’→small molecules; The following reactions mainly occur in the high-temperature oxidation process: ⑨ H+O2→O+OH ⑩ CO+O→CO2; where R is a fuel molecule, R’ is a fuel radical; R’O2 undergoes hydrogen atom transfer through a transition state and is isomerized to R’’OOH through a primary hydrogenation reaction; O2R’’OOH undergoes a secondary hydrogenation reaction and isomerization to form HOOR’’’OOH; S4. Conduct an oxidation kinetics test on the crude oil to be evaluated, and obtain the reaction equations occurring in the crude oil to be evaluated through simulation analysis; S5. According to the correlation between the reaction equations occurring in the crude oil to be evaluated and the reaction equations occurring in each of the three specific processes, judge the oxidation activity of the crude oil to be evaluated; in step S5, the process of judging the oxidation activity of the crude oil to be evaluated includes: If the crude oil to be evaluated undergoes reactions ①-⑩, it is judged that the crude oil to be evaluated is type I oil. Among them, the type I oil has three specific processes: low-temperature oxidation process, negative temperature coefficient oxidation process, and high-temperature oxidation process. The type I oil has medium oxidation activity and is easy to catch fire; If the crude oil to be evaluated undergoes reactions ①-⑧, and reactions ②-⑧ occur repeatedly and then stop; or reactions ②-⑧ occur repeatedly and then reactions ⑨ and ⑩ occur, it is judged that the crude oil to be evaluated is type II oil. Among them, the type II oil has three specific processes: low-temperature oxidation process, negative temperature coefficient oxidation process, and high-temperature oxidation process. The type II oil has strong oxidation activity and a long ignition delay time; If the crude oil to be evaluated undergoes reactions ① and ②, then enters reactions ⑨ and ⑩, and then stops, and reactions ① and ② and reactions ⑨ and ⑩ must be raised to a higher temperature again to occur, it is judged that the crude oil to be evaluated is type III oil. Among them, the type III oil does not have three specific processes. The type III oil has weak oxidation activity and is difficult to catch fire.

2. The evaluation method according to claim 1, wherein In step S1, the crude oil includes at least one of conventional heavy oil, extra-heavy oil, and super-heavy oil.

3. The evaluation method according to claim 1, wherein, In step S2, a rapid compressor and / or an accelerating calorimeter are used for the oxidation kinetics test; wherein, by using the rapid compressor, the change curve of pressure with time of each group of crude oils at different temperatures is obtained, and by using the accelerating calorimeter, the change curve of the heating rate of each group of crude oils with temperature is obtained.

4. The evaluation method according to claim 3, wherein A rapid compressor and / or an accelerating calorimeter are used to test the oxidation process of each group of crude oils and / or narrow cut oils with different distillation ranges of each group of crude oils.

5. A method for improving the oxidation activity of crude oil, characterized in that, The method includes: Judging the oxidation activity of the crude oil to be tested according to the evaluation method described in any one of claims 1-4; Taking corresponding measures according to the judgment result of the oxidation activity of the crude oil to be tested to improve the oxidation activity of the crude oil to be tested; When in the judgment result, the crude oil to be tested is a type II oil, the measure is to increase the heat of the crude oil to be tested; When in the judgment result, the crude oil to be tested is a type III oil, the measure is to add a first additive rich in active components and / or a second additive that can promote the chain reaction for generating active groups in the crude oil to be tested.

6. The method according to claim 5, wherein The way to increase the heat of the crude oil to be tested is a self-heating material for in-situ heat generation underground.

7. The method according to claim 5, wherein, The first additive is selected from at least one of substances containing OH groups, substances that can release OH groups upon heating, and substances that can release OH groups through reactions.

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