Method for measuring low-temperature oxidation reaction rate of crude oil by using pressure changes under different atmosphere conditions

Abstract

The invention discloses a method for measuring low-temperature oxidation reaction rate of crude oil by using pressure changes under different atmosphere conditions, and belongs to the technical field of oil reservoir development. According to the technical scheme, a pressure-bearing container is adopted, and an air and high-purity nitrogen parallel contrast experiment is designed, so that the oxidation process of crude oil at low temperature is accurately quantified; the interference of nitrogen on oxygen consumption evaluation is effectively eliminated by accurately monitoring and comparing the change of pressure in the two containers along with time, so that the oxidation reaction of oxygen and crude oil is accurately reflected; and calculating the oxidation reaction rate in combination with a gas state equation. The method has the beneficial effects that the data accuracy can be remarkably improved, the oxidation characteristics of the crude oil can be quickly evaluated, and the production process and safety management are optimized; meanwhile, understanding of an oxidation mechanism is deepened, and development of a kinetic model is promoted. The method is widely applicable to evaluation of oxidation stability of chemicals in the fields of energy, chemical industry and the like, and industrial green transformation and technical innovation are promoted.

Description

Technical Field

[0001] This invention belongs to the field of oil reservoir development technology and relates to a crude oil low-temperature oxidation enhanced oil recovery technology. It is applicable to the method of enhancing oil recovery by using high-pressure air injection at low temperature. Specifically, it relates to a method for determining the low-temperature oxidation reaction rate of crude oil by using pressure changes under high-purity nitrogen injection and air injection conditions. Background Technology

[0002] Air injection is a novel method for enhancing oil recovery. Air has advantages such as wide availability, low cost, no environmental pollution, and no geographical limitations. Air injection not only provides the benefits of general gas injection but also offers additional effects from oxidation. After air is injected into the reservoir, the oxygen in the air undergoes a low-temperature oxidation reaction with the crude oil under reservoir temperature conditions. The resulting carbon monoxide, carbon dioxide, water, and other byproducts mix with nitrogen to form a form of flue gas drive, thereby increasing the oil recovery rate.

[0003] The reaction mechanism of air injection technology for enhanced oil recovery is low-temperature oxidation. Determining the low-temperature oxidation reaction rate of crude oil is fundamental to calculating the kinetic parameters of the crude oil oxidation reaction. Its magnitude not only affects whether the oxygen can be fully consumed before reaching the production well, reducing the oxygen concentration below the critical oxygen concentration to ensure production safety, but also the ease with which the reaction front forms, significantly impacting the improvement in oil recovery.

[0004] Currently, methods for determining oxidation reaction rates under low-temperature oxidation conditions with air injection do not consider the role of nitrogen, assuming that nitrogen is an inert gas and does not react with formation crude oil. However, air contains up to 78% nitrogen, and under certain formation pressures, some nitrogen will infiltrate the crude oil, becoming miscible. This nitrogen infiltrated into the crude oil is mistakenly counted as consumed oxygen in calculations, leading to significant deviations in the determination of low-temperature oxidation reaction rates of crude oil under high-pressure air injection conditions.

[0005] Specifically, when air is injected deep into the formation as an oxidant, its nitrogen component, which accounts for up to 78%, cannot be ignored. With increasing formation pressure, the solubility of nitrogen in crude oil increases significantly, leading to a considerable portion of nitrogen physically mixing with the crude oil, forming a miscible state. This miscibility not only alters the physical properties of the crude oil but may also indirectly affect the kinetics of the oxidation reaction, even though nitrogen itself does not directly participate in the oxidation reaction.

[0006] However, in existing methods for determining the rate of low-temperature oxidation of crude oil, the common practice is to treat the presence of nitrogen as a "non-reactive" state, simply equating the total volume or mass consumed with the amount of oxygen consumed. This approach ignores the actual impact of nitrogen dissolution on the volume, density, and even the partial pressure of oxygen in the reaction system, leading to significant deviations in the calculated oxidation rate. Summary of the Invention

[0007] To address the shortcomings of existing techniques where the measured oxidation reaction rate deviates significantly from the actual value, this invention proposes a method for determining the low-temperature oxidation reaction rate of crude oil using pressure changes under different atmospheric conditions. In this method, air and high-purity nitrogen are used as parallel samples to react with dehydrated crude oil, and the pressure changes are used to calculate a more accurate low-temperature oxidation reaction rate of the crude oil.

[0008] To achieve the above objectives, the present invention provides the following technical solution:

[0009] A method for determining the low-temperature oxidation rate of crude oil using pressure changes under different atmospheric conditions, comprising the following steps:

[0010] S1. Dehydrate the crude oil to be tested;

[0011] S2. Take two pressure-bearing reaction devices of the same size as reaction vessels, and label them as container 1 and container 2. Inject high-pressure air into empty container 1 and container 2 respectively to make the containers pressurized. Let the containers stand and verify that the airtightness of the reaction vessels is good. Then, purge the air and open the containers for use.

[0012] S3. Fill containers #1 and #2 with the same volume of dehydrated crude oil, and keep containers #1 and #2 at a constant temperature.

[0013] S4. Inject high-pressure air into container #1 at a constant reaction temperature until its pressure reaches the reaction pressure. Inject high-pressure, high-purity nitrogen into container #2 at a constant reaction temperature until its pressure reaches the same reaction pressure as container #1. After the pressure stabilizes, record the time t0, the pressure P1 of container #1, and the pressure P2 of container #2 respectively.

[0014] S5. Under constant reaction temperature conditions, record the time t and the pressure P of container #1 at regular intervals. 1t Pressure P of container #2 2t Continue until the pressure in the container no longer changes, indicating that the reaction is complete;

[0015] S6. After the reaction is complete, samples of the gas in containers 1 and 2 are taken respectively, and the components of the gas after the reaction are analyzed.

[0016] S7. Calculate the low-temperature oxidation reaction rate through data processing.

[0017] Furthermore, the calculation method for step S7 is as follows:

[0018] S7.1. Using the pressure drop method, and ignoring the influence of nitrogen, calculate the oxygen consumption n1 during the reaction of air and crude oil as a reference value;

[0019] S7.2 Calculate oxygen consumption under different pressure differences when eliminating the influence of nitrogen. At the same time, there is a pressure difference ΔP between container #1 and container #2. The pressure difference ΔP increases continuously with time t. Assuming that the volume of gas and crude oil does not change during the reaction, we can obtain from the gas state equation PV=nRT: under constant temperature T and volume V, the amount of substance n is directly proportional to the pressure P. That is, the oxygen consumption is in a one-to-one correspondence with the change in pressure difference ΔP. Therefore, the oxygen consumption n2 during the reaction can be calculated, and n2<n1.

[0020] S7.3. Differentiate the oxygen consumption n2 during the reaction process and divide it by the crude oil volume to obtain the low-temperature oxidation reaction rate of the crude oil during the entire reaction process.

[0021] Furthermore, in step S1, the crude oil to be tested is dehydrated using a dehydration instrument, and the crude oil is then used after passing the dehydration test.

[0022] Furthermore, in step S2, after the pressure remains unchanged after the container has been left to stand for 3 hours, and the airtightness of the reaction container is verified, the air is released and the container is opened for use.

[0023] Furthermore, in step S3, containers #1 and #2 containing the injected dehydrated crude oil are placed in a constant temperature device for constant temperature operation.

[0024] Furthermore, containers #1 and #2, which were injected with dehydrated crude oil, were placed in a constant temperature device and kept at the reaction temperature for more than 3 hours.

[0025] Furthermore, in step S4, air is injected into the reaction vessel using a high-pressure air bottle.

[0026] Furthermore, the high-pressure air cylinder has a pressure of 12MPa-15MPa.

[0027] Furthermore, in step S5, until P 1t and P 2t If no further changes occur for more than 4 hours, the reaction is considered complete.

[0028] Furthermore, in step S6, the reacted O2, N2, CO, CO2, Cl, C2, C3, and C in containers #1 and #2 are respectively...6+ Component analysis was performed using H2.

[0029] The beneficial effects of this invention are:

[0030] Compared with existing technologies, the method for determining the low-temperature oxidation reaction rate of crude oil using pressure changes under different atmospheric conditions, as described in this invention, employs a pressure vessel to conduct parallel comparative experiments with air and high-purity nitrogen. When air reacts with crude oil, oxygen in the air is consumed in the oxidation reaction, while nitrogen in the air mixes with the crude oil under high pressure, with some nitrogen dissolving into the crude oil and being consumed. Their combined effect causes the pressure to continuously decrease and eventually stabilize. When high-purity nitrogen reacts with crude oil under the same air and crude oil conditions, only the nitrogen that mixes with the crude oil and dissolves into it is consumed, leading to a pressure decrease and eventually stabilization. The difference in pressure changes between these two gases reflects the consumption of oxygen solely in the oxidation reaction with crude oil, thus eliminating the influence of nitrogen in the air on oxygen consumption. The relationship between oxygen consumption and pressure difference is obtained using the gas law, thereby measuring the low-temperature oxidation reaction rate of the entire reaction process. This provides fundamental data for calculating the kinetic parameters of crude oil oxidation and comparing the reactivity of different crude oils.

[0031] In addition, the present invention has the following significant advantages and technological innovations:

[0032] (1) Precise quantification of oxidation reaction process: By precisely controlling experimental conditions and using high-purity nitrogen as a reference, this method can quantify the oxidation reaction process between oxygen in the air and crude oil with great precision, avoiding the estimation error of oxygen consumption caused by nitrogen mixing in the traditional method, thereby improving the accuracy and reliability of the data.

[0033] (2) Efficient screening of crude oil quality: Based on the measured low-temperature oxidation reaction rate, the oxidation reaction activity of different crude oil samples can be quickly evaluated, providing a scientific basis for the selection of raw materials, process optimization and safety management in the oil industry in crude oil extraction, processing, storage and transportation. In particular, it has important application value in assessing crude oil stability and predicting potential oxidation risks.

[0034] (3) Promoting Oxidation Kinetics Research: This method not only provides an effective means for the direct determination of kinetic parameters of crude oil oxidation reaction, but also promotes a deeper understanding of the crude oil oxidation mechanism. By comparing the reaction rates under different conditions, the influence of factors such as temperature, pressure, and crude oil composition on the oxidation reaction can be further studied, laying the foundation for constructing a more accurate oxidation kinetic model.

[0035] (4) Dual protection of environmental protection and safety: Strict control of experimental conditions in the laboratory environment reduces the environmental pollution and safety risks that may be caused by crude oil oxidation during actual production. At the same time, by optimizing reaction conditions, effective ways to reduce the generation of oxidation byproducts can be explored, promoting the green development of the petroleum industry.

[0036] (5) Expanding application areas: This invention is not only applicable to the study of the oxidation reaction of crude oil, but can also be extended to the oxidation stability assessment of other liquid hydrocarbons, fuel oils and related chemicals, providing technical support for research and development in multiple fields such as energy, chemical industry, and materials science. Attached Figure Description

[0037] To more clearly illustrate the technical solutions of the embodiments of the present invention, the present invention will be described in detail below with reference to the accompanying drawings and detailed embodiments. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort. Wherein:

[0038] Figure 1 This is an experimental flowchart of the present invention for determining the low-temperature oxidation reaction rate of crude oil using pressure changes under conditions of high-purity nitrogen injection and air injection.

[0039] Figure 2a This is a schematic diagram of the pressure change of air and high-purity nitrogen in the original reaction in Example 1 of the present invention;

[0040] Figure 2b This is a graph showing the change in oxygen consumption and oxidation reaction rate in Example 1 of the present invention;

[0041] Figure 3a This is a schematic diagram of the pressure change of air and high-purity nitrogen in the original reaction in Example 2 of the present invention;

[0042] Figure 3b This is a graph showing the change in oxygen consumption and oxidation reaction rate in Example 2 of the present invention. Detailed Implementation

[0043] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention. The following description, in conjunction with the accompanying drawings... Figure 1-3b The method for determining the low-temperature oxidation reaction rate of crude oil using pressure changes under different atmospheric conditions is further explained.

[0044] To further illustrate the technical means and effects adopted by the present invention to achieve the intended purpose, the following, in conjunction with the accompanying drawings and preferred embodiments, describes the specific implementation methods, steps, features, and effects of the method for determining the low-temperature oxidation reaction rate of crude oil using pressure changes under different atmospheric conditions proposed in accordance with the present invention.

[0045] Please see Figure 1 As shown, Figure 1 This is a flowchart of a method for determining the low-temperature oxidation reaction rate of crude oil using pressure changes under different atmospheric conditions, as per the present invention. The invention involves simultaneously placing two reaction vessels containing dehydrated crude oil into a constant-temperature device. After maintaining this temperature for a certain period, high-purity nitrogen and air are simultaneously injected into the reaction vessels, respectively, to bring both vessels to the same reaction pressure. The reaction is then carried out at the same reaction temperature within the constant-temperature device, and the oxidation reaction rate is calculated by recording the pressure changes. The following examples further illustrate the invention, but are not intended to limit the determination method.

[0046] Example 1

[0047] This embodiment uses the high pour point oil from oilfield A to determine the low-temperature oxidation reaction rate under conditions of 383.15 K, 10.35 MPa, and constant temperature for 172.83 hours.

[0048] (1) The crude oil retrieved from Block A of the oil field is transferred to a dehydration instrument for dehydration treatment. After the crude oil is dehydrated and qualified, it is ready for use.

[0049] (2) Take two pressure-bearing reaction apparatuses of the same size (500ml each) as reaction containers, and label them as container #1 and container #2. Inject air into the reaction containers using a 15MPa high-pressure air bottle until the pressure reaches 12MPa to verify the airtightness of the reaction containers. After standing for 3 hours, if the pressure inside the reaction containers does not change, the airtightness of the reaction containers is considered good. Release the air, open the containers, and set them aside for use.

[0050] (3) Fill 200ml of dehydrated crude oil into container 1 and container 2 respectively, and place container 1 and container 2 containing dehydrated crude oil into a constant temperature device to maintain a temperature of 383.15K for more than 3 hours;

[0051] (4) High-pressure air was injected into container 1 at a constant reaction temperature to make its pressure reach 10.35 MPa. High-pressure high-purity nitrogen was injected into container 2 under the same conditions to make its pressure reach 10.35 MPa. After the pressure stabilized, the time t0, pressure P1 of container 1 and pressure P2 of container 2 were recorded respectively.

[0052] (5) At a temperature of 383.15K, the time t and the pressure P of container #1 were recorded at regular intervals thereafter. 1tPressure P of container #2 2t The reaction ended 172.83 hours later, after the pressure inside the container had remained unchanged for more than 4 hours.

[0053] (6) After the reaction, the gas in containers 1 and 2 were sampled and the composition of the gas after the reaction was analyzed. Table 1 shows the changes in gas composition after low-temperature oxidation of high-pour-point oil in oilfield A under different atmospheres at 110℃.

[0054]

[0055] Table 1. Changes in tail gas components after low-temperature oxidation of high-pour-point oil from Oilfield A under different atmospheric conditions at 110℃.

[0056] (7) Data Processing. 1) First, using the conventional pressure drop method, ignoring the influence of nitrogen, the oxygen consumption of 0.18 mol during the reaction of air and crude oil was calculated as a reference value. 2) To eliminate the influence of nitrogen, the oxygen consumption under different pressure differences was calculated. At the same time, there is a pressure difference ΔP between container #1 and container #2. The pressure difference ΔP increases continuously with time t. Figure 2a This represents the pressure change over time in the reaction of air and high-purity nitrogen with high-pour-point oil from oilfield A. Assuming that the volumes of gas and crude oil remain constant during the reaction, the gas law PV = nRT shows that, under constant temperature T and volume V, the amount of substance n is directly proportional to the pressure P. That is, the oxygen consumption is directly proportional to the change in pressure difference ΔP. Therefore, the oxygen consumption n2 during the reaction can be calculated, and n2 < 0.18 mol. (See...) Figure 2b 3) Differentiating the oxygen consumption n2 during the reaction process and dividing it by the crude oil volume yields the low-temperature oxidation rate of the crude oil throughout the entire reaction process. See [reference needed]. Figure 2b .

[0057] Example 2

[0058] This embodiment uses the low-temperature oxidation reaction rate of light oil from oilfield B at a temperature of 363.15 K, a pressure of 8.85 MPa, and a constant temperature for 186.33 hours to determine the oxidation rate.

[0059] (1) The crude oil retrieved from Block B of the oil field is transferred to a dehydration instrument for dehydration treatment. After the crude oil is dehydrated and qualified, it is ready for use.

[0060] (2) Take two pressure-bearing reaction apparatuses of the same size (500ml each) as reaction containers, and label them as container #1 and container #2. Inject air into the reaction containers using a 12MPa high-pressure air bottle to a pressure of 10MPa to verify the airtightness of the reaction containers. After standing for 3 hours, if the pressure inside the reaction containers does not change, the airtightness of the reaction containers is considered good. Release the air, open the containers, and set them aside for use.

[0061] (3) Fill containers 1 and 2 with 300ml of dehydrated crude oil of the same volume respectively, and place containers 1 and 2 with the dehydrated crude oil into a constant temperature device and keep them at a constant temperature of 363.15K for more than 3 hours.

[0062] (4) High-pressure air was injected into container 1 at a constant reaction temperature to make its pressure reach 8.85 MPa. High-pressure high-purity nitrogen was injected into container 2 under the same conditions to make its pressure reach 8.85 MPa. After the pressure stabilized, the time t0, pressure P1 of container 1 and pressure P2 of container 2 were recorded respectively.

[0063] (5) At a temperature of 363.15K, the time t and the pressure P of container #1 were recorded at regular intervals thereafter. 1t Pressure P of container #2 2t After 186.33 hours, the pressure inside the container has remained unchanged for more than 4 hours, at which point the reaction inside the container is complete.

[0064] (6) After the reaction was completed, the gas in containers 1 and 2 was sampled and the composition of the gas after the reaction was analyzed. Table 2 shows the changes in the composition of the tail gas after low-temperature oxidation of oilfield B light oil at 90℃ under different atmosphere conditions.

[0065]

[0066] Table 2. Changes in tail gas composition after low-temperature oxidation of oilfield B light oil under different atmospheric conditions at 90℃.

[0067] (7) Data Processing. 1) First, using the conventional pressure drop method, ignoring the influence of nitrogen, the oxygen consumption of 0.089 mol during the reaction of air and crude oil was calculated as a reference value. 2) To eliminate the influence of nitrogen, the oxygen consumption under different pressure differences was calculated. At the same time, there is a pressure difference ΔP between container #1 and container #2. The pressure difference ΔP increases continuously with time t. Figure 3a This represents the pressure change over time in the reaction of air and high-purity nitrogen with thin oil from oilfield B. Assuming that the volumes of gas and crude oil remain constant during the reaction, the gas law PV = nRT shows that, under constant temperature T and volume V, the amount of substance n is directly proportional to the pressure P. That is, the oxygen consumption is directly proportional to the change in pressure difference ΔP. Therefore, the oxygen consumption n² during the reaction can be calculated, and n² < 0.089 mol. (See...) Figure 3b 3) Differentiating the oxygen consumption n2 during the reaction process and dividing it by the crude oil volume yields the low-temperature oxidation rate of the crude oil throughout the entire reaction process. See [reference needed]. Figure 3b .

[0068] The above description is only a preferred embodiment 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 inventive concept of the present invention, should be covered within the scope of protection of the present invention.

Claims

1. A method for determining the low-temperature oxidation reaction rate of crude oil using pressure changes under different atmospheric conditions, characterized in that, The steps are as follows: S1. Dehydrate the crude oil to be tested; S2. Take two pressure-bearing reaction devices of the same size as reaction vessels, and label them as container 1 and container 2. Inject high-pressure air into empty container 1 and container 2 respectively to make the containers pressurized. Let the containers stand and verify that the airtightness of the reaction vessels is good. Then, purge the air and open the containers for use. S3. Fill containers #1 and #2 with the same volume of dehydrated crude oil, and keep containers #1 and #2 at a constant temperature. S4. Inject high-pressure air into container #1 at a constant reaction temperature until its pressure reaches the reaction pressure. Inject high-pressure, high-purity nitrogen into container #2 at a constant reaction temperature until its pressure reaches the same reaction pressure as container #1. After the pressure stabilizes, record the time t0, the pressure P1 of container #1, and the pressure P2 of container #2 respectively. S5. Under constant reaction temperature conditions, record the time t and the pressure P of container #1 at regular intervals. 1t Pressure P of container #2 2t Continue until the pressure in the container no longer changes, indicating that the reaction is complete; S6. After the reaction is complete, samples of the gas in containers 1 and 2 are taken respectively, and the components of the gas after the reaction are analyzed. S7. Calculate the low-temperature oxidation reaction rate through data processing.

2. The method for determining the low-temperature oxidation reaction rate of crude oil using pressure changes under different atmospheric conditions as described in claim 1, characterized in that, The calculation method for step S7 is as follows: S7.

1. Using the pressure drop method, and ignoring the influence of nitrogen, calculate the oxygen consumption n1 when air reacts with crude oil as a reference value; S7.2 Calculate oxygen consumption under different pressure differences when eliminating the influence of nitrogen. At the same time, there is a pressure difference ΔP between container #1 and container #2. The pressure difference ΔP increases continuously with time t. Assuming that the volume of gas and crude oil does not change during the reaction, we can obtain from the gas state equation PV=nRT: under constant temperature T and volume V, the amount of substance n is directly proportional to the pressure P. That is, the oxygen consumption is in a one-to-one correspondence with the change in pressure difference ΔP. Therefore, the oxygen consumption n2 during the reaction can be calculated, and n2<n1. S7.

3. Differentiate the oxygen consumption n2 during the reaction process and divide it by the crude oil volume to obtain the low-temperature oxidation reaction rate of the crude oil during the entire reaction process.

3. The method for determining the low-temperature oxidation reaction rate of crude oil using pressure changes under different atmospheric conditions as described in claim 1, characterized in that, In step S1, the crude oil to be tested is dehydrated using a dehydration instrument, and the crude oil is then ready for use after passing the dehydration process.

4. The method for determining the low-temperature oxidation reaction rate of crude oil using pressure changes under different atmospheric conditions as described in claim 1, characterized in that, In step S2, after the pressure remains unchanged after the container has been left to stand for 3 hours, the air tightness of the reaction container is verified to be good. The container is then opened to release the air and is ready for use.

5. The method for determining the low-temperature oxidation reaction rate of crude oil using pressure changes under different atmospheric conditions as described in claim 1, characterized in that, In step S3, containers #1 and #2, into which dehydrated crude oil is injected, are placed in a constant temperature device for constant temperature operation.

6. The method for determining the low-temperature oxidation reaction rate of crude oil using pressure changes under different atmospheric conditions as described in claim 5, characterized in that, Containers #1 and #2, into which dehydrated crude oil was injected, were placed in a constant temperature device and kept at the reaction temperature for more than 3 hours.

7. The method for determining the low-temperature oxidation reaction rate of crude oil using pressure changes under different atmospheric conditions as described in claim 1, characterized in that, In step S4, air is injected into the reaction vessel using a high-pressure air bottle.

8. The method for determining the low-temperature oxidation reaction rate of crude oil using pressure changes under different atmospheric conditions as described in claim 7, characterized in that, The high-pressure air cylinder has a pressure of 12MPa-15MPa.

9. The method for determining the low-temperature oxidation reaction rate of crude oil using pressure changes under different atmospheric conditions as described in claim 1, characterized in that, In step S5, until P 1t and P 2t If no further changes occur for more than 4 hours, the reaction is considered complete.

10. The method for determining the low-temperature oxidation reaction rate of crude oil using pressure changes under different atmospheric conditions as described in claim 1, characterized in that, In step S6, the reacted O2, N2, CO, CO2, Cl, C2, C3, and C in containers #1 and #2 are respectively... 6+ Component analysis was performed using H2.

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