An experimental method for evaluating hydrogen sulfide production during simulated thermal recovery.

Abstract

This invention discloses an experimental method for evaluating hydrogen sulfide production during a simulated thermal recovery process. The evaluation method includes the following steps: S1, placing the sample to be tested in a ceramic container and purging any gases therein, then placing the ceramic container inside a covered, pressure-resistant stainless steel container; S2, heating the covered, pressure-resistant stainless steel container to a set temperature; injecting nitrogen gas into the inside of the covered, pressure-resistant stainless steel container and the top of the ceramic container to the injection pressure of the thermal recovery process, simulating the thermal recovery process; S3, after the thermal recovery process is completed, cooling is performed, nitrogen gas is released, and the gas generated in the ceramic container is detected. This invention effectively separates the reactants from the metal using an aerospace-grade ceramic container, avoiding the influence of the metal container on the experimental results of hydrogen sulfide generation.

Description

Technical Field

[0001] This invention relates to an experimental method for evaluating hydrogen sulfide production during simulated thermal recovery, belonging to the field of heavy oil thermal recovery development technology. Background Technology

[0002] The world's proven reserves of heavy oil are approximately 815 billion tons, accounting for 70% of global remaining oil reserves, making it an important alternative resource for oil production. Due to the high temperature sensitivity of heavy oil viscosity, its development is typically carried out through thermal recovery, primarily using steam injection and steam drive. Heavy oil contains sulfur; the sulfur content in heavy oil from the United States, Canada, and Venezuela is as high as 3%–5%, while in my country, it is generally around 0.5%. During thermal recovery, due to the high temperature and pressure, the sulfur in the heavy oil undergoes a chemical reaction to produce hydrogen sulfide gas, which can harm extraction personnel and equipment. Hydrogen sulfide is a highly toxic and corrosive gas, with a safe critical concentration of 20 ppm (30 mg / m³). 3 Threshold limit: 10 ppm (15 mg / m³) 3 When the hydrogen sulfide concentration reaches 1000 ppm (1500 mg / m³), 3 At high concentrations, hydrogen sulfide can cause death within minutes. Therefore, constant monitoring of hydrogen sulfide concentration changes is crucial during thermal extraction. In conclusion, simulating hydrogen sulfide production patterns during thermal extraction is of paramount importance for guiding actual on-site production.

[0003] Traditionally, a metal drum or quartz tube is placed inside a pressure-resistant stainless steel container, and reactants are then added. Nitrogen gas is introduced to pressurize the container, and a furnace is used for heating to simulate thermal recovery experiments. However, during thermal recovery, the metal in the container catalyzes the thermal decomposition of organosulfur compounds and the thermochemical reduction of sulfates, leading to an increased production of hydrogen sulfide gas and ultimately causing significant errors in the experimental data. Furthermore, nitrogen is an inert gas and is generally considered not to participate in the thermal decomposition of organosulfur compounds and the thermochemical reduction of sulfates. However, the addition of nitrogen may affect the concentration measurement of the produced gases, thus affecting the accuracy of hydrogen sulfide concentration measurements. Simultaneously, the addition of nitrogen significantly dilutes the concentration of the generated gases, hindering interactions and reactions between the generated gases and between gases and liquids, thus affecting the produced hydrogen sulfide concentration.

[0004] In summary, existing methods for simulating hydrogen sulfide production during thermal recovery have shortcomings, such as the involvement of metal (ions) in the experimental reaction within the metal container and the hindering of gas-to-gas and gas-to-liquid interactions by nitrogen. These limitations lead to significant discrepancies between experimental results and actual oilfield thermal recovery processes. There is an urgent need to establish a novel experimental setup and evaluation method for simulating hydrogen sulfide production during thermal recovery processes, free from the influence of external metal (ions) and the obstruction of gas-to-gas and gas-to-liquid interactions by nitrogen. Summary of the Invention

[0005] The purpose of this invention is to provide an experimental method for evaluating hydrogen sulfide production during simulated thermal recovery. By using an aerospace ceramic container, the reactants are effectively separated from the metal, thus avoiding the influence of the metal container on the experimental results of hydrogen sulfide generation.

[0006] The experimental method for evaluating hydrogen sulfide production during simulated thermal recovery provided by this invention includes the following steps:

[0007] S1. Place the sample to be tested in a ceramic container and remove the gas therein, then place the ceramic container in a lidded pressure-resistant stainless steel container.

[0008] S2. Heat the covered pressure-resistant stainless steel container to a set temperature; inject nitrogen into the inside of the covered pressure-resistant stainless steel container and the upper part of the ceramic container to the injection pressure of the thermal recovery process to simulate the thermal recovery process.

[0009] S3. After the thermal recovery process is completed, the temperature is lowered and nitrogen is released. The gas generated in the ceramic container can then be detected.

[0010] In the above-mentioned evaluation test method, the ceramic container is an aerospace ceramic container with good temperature resistance, pressure resistance and thermal conductivity, and its material is silicon carbide.

[0011] In the above-mentioned evaluation test method, the ceramic container and the pressure-resistant stainless steel container with lid have the same internal size and shape so that they fit together, and the pressure-resistant stainless steel container with lid plays a supporting role.

[0012] In the above-mentioned evaluation experimental method, the bottom of the ceramic container is fitted with an end cap, and the top is sealed by the piston;

[0013] The piston is provided with an exhaust port.

[0014] In the above evaluation experimental method, step S1 is performed according to the following steps:

[0015] Move the piston upwards to close the vent, then invert the ceramic container, open the end cap, place the sample to be tested inside, close the end cap and seal it; open the vent, push the piston downwards to expel the gas, and close the vent.

[0016] In the above-mentioned evaluation experimental method, the conditions for the thermal recovery process are as follows:

[0017] Temperature ranges from 0 to 350℃, pressure from 0 to 15 MPa, and time from 0 to 72 hours.

[0018] In the above evaluation experimental method, in step S3, a gas chromatograph is used to detect the gas, including components such as hydrogen sulfide and sulfur dioxide.

[0019] Unlike existing experimental evaluation methods, the present invention designs an aerospace ceramic container inside a stainless steel container, which has good pressure resistance and heat transfer performance. At the same time, it avoids the catalytic effect of the metal container on the hydrogen sulfide generation experiment, reducing the hydrogen sulfide concentration by 8% to 27%, making the experiment more accurate and closer to the actual formation.

[0020] Unlike existing experimental evaluation methods, the reactants in the sealed container (aerospace ceramic container) no longer come into contact with nitrogen, thus avoiding the dilution and blocking effect of nitrogen on the generated gas. The hydrogen sulfide concentration is increased by about 5%, which improves the accuracy of the experiment and is closer to the actual heavy oil thermal recovery process.

[0021] Unlike existing experimental evaluation methods, the gas generated in the sealed container (aerospace ceramic container) no longer comes into contact with nitrogen. The concentration of hydrogen sulfide in the detected gas has increased from about 0.00005% to about 4%, significantly improving the accuracy of hydrogen sulfide gas detection.

[0022] This invention effectively separates the reactants from the metal using an aerospace ceramic container, avoiding the influence of the metal container on the hydrogen sulfide generation experimental results. The accuracy of the experimental results is improved by 8.11% to 27.03%. In this invention, the gas generated inside the aerospace ceramic container no longer comes into contact with nitrogen, thus avoiding the dilution and blocking effect of nitrogen on the generated gas, resulting in an average increase of 5.41% in hydrogen sulfide concentration. Furthermore, the fact that the gas generated inside the aerospace ceramic container no longer comes into contact with nitrogen increases the hydrogen sulfide concentration from approximately 0.00005% to approximately 4%, significantly improving detection accuracy. Attached Figure Description

[0023] Figure 1 This is a schematic diagram of the structure of the aerospace ceramic container used in the method of the present invention.

[0024] Figure 2 This is the experimental result of Comparative Example 1 of the present invention.

[0025] Figure 3 The results are from Example 1 of this invention.

[0026] Figure 4 This is the experimental result of Comparative Example 2 of the present invention.

[0027] Figure 5 The results are from Comparative Example 3 of this invention. Detailed Implementation

[0028] Unless otherwise specified, the experimental methods used in the following examples are conventional methods.

[0029] Unless otherwise specified, all materials and reagents used in the following examples are commercially available.

[0030] The materials used in the following embodiments and comparative examples are as follows:

[0031] 1. Experimental materials

[0032] The results of elemental composition tests for a crude oil from the Bohai Sea are shown in Table 1.

[0033] Table 1. Organic element analysis results of a crude oil from the Bohai Sea.

[0034]

[0035] The results of the sulfur source distribution test in a crude oil from the Bohai Sea are shown in Table 2.

[0036] Table 2. Results of sulfur source distribution test in crude oil (%)

[0037] hashtag Total sulfur content Thiol sulfur Sulfide sulfur Thiophene sulfur Crude oil from a certain oil field in Bohai 0.247 0.0012 0.079 0.1668

[0038] Table 3 shows the XRD characterization analysis results of core samples from the target block in the Bohai Sea in the example.

[0039] Table 3. XRD characterization analysis results of core samples from the target block.

[0040]

[0041] The results of the formation water ion composition test in a certain oilfield in the Bohai Sea are shown in Table 4.

[0042] Table 4 Ion composition of formation water in a Bohai oilfield

[0043]

[0044] The instruments used in the following examples and comparative examples are: vacuum pump, gas chromatograph, sealed stainless steel container and aerospace ceramic container.

[0045] The structural diagram of the aerospace ceramic container is shown below. Figure 1 As shown, its main material is silicon carbide, and its size is the same as the inside of a sealed stainless steel container. One end of the aerospace ceramic container is fitted with an end cap 3 for placing the sample, and the other end is sealed by a piston 1. An exhaust port 2 is provided in the middle of the piston.

[0046] The experimental principles on which the following examples and comparative examples are based are as follows:

[0047] Under high temperature and high pressure conditions, sulfur-containing compounds in crude oil, as well as sulfur-containing ions in formation water and formation cores, undergo thermal cracking and hydrothermal cracking reactions to generate hydrogen sulfide gas.

[0048] The gas chromatography detection conditions in the following examples and comparative examples are as follows:

[0049] The gas generated by the reaction under high temperature and high pressure is passed into a gas chromatograph, which is used to detect the generated gas and compare the concentrations of the generated gas. The generated gas is then converted into the amount of gas generated per gram of crude oil using the Clapeyron equation PV = nRT.

[0050] Comparative Example 1: Using existing methods

[0051] ① Place an open Hastelloy steel container inside a covered pressure-resistant Hastelloy steel container, and put the sample (70% crude oil from a Bohai oilfield + 30% simulated formation water + 15% of the crude oil mass of formation sand, totaling 80g) into the open Hastelloy steel container.

[0052] ② Close the pressure-resistant Hastelloy steel container;

[0053] ③ Evacuate and remove oxygen;

[0054] ④ Introduce a certain amount of nitrogen gas and heat to 250℃. Use the amount of nitrogen gas introduced to control the experimental pressure and adjust the pressure to 5MPa.

[0055] ⑤ Keep at the set temperature for 24 hours.

[0056] ⑥ Lower the temperature to room temperature, and then collect the gas.

[0057] ⑦ Use a gas chromatograph to measure the content of gases such as hydrogen sulfide and sulfur dioxide in the gas.

[0058] Example 1: Using the method of the present invention

[0059] ① First, fabricate an aerospace ceramic container (e.g., one with a lid and pressure-resistant Hastelloy steel) that is the same size as the interior of the container. Figure 1 As shown, the aerospace ceramic container contains an aerospace ceramic piston inside, with an openable vent in the center made of aerospace ceramic material. The bottom of the aerospace ceramic container can be opened for easy sample placement.

[0060] ② First, move the piston up and close the vent. Then, invert the container, open the bottom end cap, and put in the deoxygenated test sample (70% crude oil from a certain oil field in Bohai Sea + 30% simulated formation water + 15% of the crude oil mass of formation sand, totaling 80g). Close the bottom end cap and seal it.

[0061] ③ Open the vent hole on the piston, push the piston downward to expel the gas, and then close the vent hole.

[0062] ④ Heat the stainless steel container to 250℃. Inject nitrogen gas into the upper part of the stainless steel and aerospace ceramic containers, and control the pressure required for the experiment by adjusting the amount of nitrogen injected; adjust the pressure to 5MPa.

[0063] ⑤ Maintain the set temperature for 24 hours. Then lower the temperature to room temperature and slowly release the nitrogen gas from the stainless steel container and the upper part of the aerospace ceramic container.

[0064] ⑥ Slowly release the gas to be tested from the exhaust port of the aerospace ceramic container.

[0065] ⑦ Use a gas chromatograph to analyze the gas to be tested, and analyze the content of components such as hydrogen sulfide and sulfur dioxide.

[0066] Comparative Example 2: A method that isolates the metal but not the nitrogen gas.

[0067] ① First, fabricate an aerospace ceramic container with the same size as the inside of a lidded, pressure-resistant stainless steel container. Inside the aerospace ceramic container is an aerospace ceramic piston with an openable vent in the center. The bottom of the aerospace ceramic container can be opened for easy sample placement.

[0068] ② First, move the piston up and close the exhaust port. Then, invert the container, open the bottom end cap, put in the deoxygenated sample to be tested (70% crude oil from a certain oil field in Bohai Sea + 30% simulated formation water + 15% of the crude oil mass of formation sand, totaling 80g), close the bottom end cap and seal it.

[0069] ③Then open the vent hole on the piston, push the piston down to expel the gas, and introduce a certain amount of nitrogen. Close the vent hole, place the container in a pressure-resistant stainless steel container with a lid, and close the pressure-resistant stainless steel container.

[0070] ④ Heat the stainless steel container to 250℃. Inject nitrogen gas into the upper part of the stainless steel and aerospace ceramic containers, and control the pressure required for the experiment by adjusting the amount of nitrogen injected; adjust the pressure to 5MPa.

[0071] ⑤ Maintain the set temperature for 24 hours. Then lower the temperature to room temperature and slowly release the nitrogen gas from the stainless steel container and the upper part of the aerospace ceramic container.

[0072] ⑥ Slowly release the gas to be tested from the exhaust port of the aerospace ceramic container.

[0073] ⑦ Use a gas chromatograph to analyze the gas to be tested, and analyze the content of components such as hydrogen sulfide and sulfur dioxide.

[0074] Comparative Example 3: The method using quartz containers

[0075] ① Place an open quartz container inside a pressure-resistant Hastelloy steel container with a lid, and put the sample (70% crude oil from a Bohai oilfield + 30% simulated formation water + 15% of the crude oil mass of formation sand, totaling 80g) into the quartz container.

[0076] ② Close the pressure-resistant Hastelloy steel container;

[0077] ③ Evacuate and remove oxygen;

[0078] ④ Introduce a certain amount of nitrogen gas and heat to 250℃. Use the amount of nitrogen gas introduced to control the experimental pressure and adjust the pressure to 5MPa.

[0079] ⑤ Keep at the set temperature for 24 hours.

[0080] ⑥ Lower the temperature to room temperature, and then collect the gas.

[0081] ⑦ Use a gas chromatograph to measure the content of gases such as hydrogen sulfide and sulfur dioxide in the gas.

[0082] The experimental results of Example 1 and Comparative Examples 2-3 are shown below. Figures 2-5 Tables 5 and 6.

[0083] Table 5. Gas content (%) generated by different evaluation methods

[0084]

[0085] Table 6 Comparison of generated gas content using different evaluation methods

[0086]

[0087]

[0088] Note: The total volume of each reaction is obtained through a flow meter, and the calculation in the table is the amount of gas produced per gram of oil; the inorganic gas does not include the content of carrier gas (nitrogen).

[0089] from Figures 2-5As shown in Tables 5 and 6, the hydrogen sulfide production amounts in Comparative Example 1, Example 2, and Comparative Examples 2-3 were 0.47 mg / g, 0.37 mg / g, 0.35 mg / g, and 0.40 mg / g, respectively. Compared to Comparative Example 1 (stainless steel container + nitrogen pressurization) and Comparative Example 3 (quartz container + nitrogen pressurization), the hydrogen sulfide production amounts in Example 1 (aerospace ceramic container + nitrogen isolation) and Comparative Example 2 (aerospace ceramic container + nitrogen pressurization) were significantly lower. Compared to Comparative Example 1 (stainless steel container + nitrogen pressurization), the hydrogen sulfide production amount in Comparative Example 3 (quartz container + nitrogen pressurization) was smaller, but still higher than that in Example 1 (aerospace ceramic container + nitrogen isolation). This is mainly because under high temperature (250°C) conditions, all water vaporizes, and some of the light components in the crude oil also vaporize and come into contact with the metal. In Comparative Examples 1 and 3, the higher hydrogen sulfide production was mainly due to the contact between the reactants and the metal. Under high temperature and pressure, some of the metal transformed into metal ions. The presence of these metal ions catalyzes the hydrothermal cracking reaction of crude oil, thus increasing the concentration of hydrogen sulfide. In other words, the hydrothermal cracking of sulfur-containing organic matter in heavy oil is not a one-step process but involves a series of reactions, including the breaking of CS bonds, hydrodesulfurization, and water-gas conversion. The addition of metal ions lowers the pH of the solution and increases the H+ concentration. Furthermore, the metal ions react with H+ ions in water molecules. + Complexation occurs, and the resulting complex ions "attack" the sulfur atom, further reducing the CS bond energy. Furthermore, metal ions act as excellent catalysts for hydrodesulfurization and water-gas conversion reactions. Therefore, the addition of metal ions promotes the forward progression of various intermediate reactions in hydrothermal cracking, thereby accelerating the entire reaction process. The hydrogen sulfide concentration will increase significantly.

[0090] from Figures 2-5 As shown in Tables 5 and 6, compared with Example 1 (aviation ceramic container + nitrogen isolation), Comparative Example 2 (aviation ceramic container + nitrogen pressurization) generates less hydrogen sulfide gas. This is mainly because during the thermal recovery simulation experiment, some hydrogen sulfide is generated through the thermochemical reduction reaction (TSR) of sulfates. Crude oil decomposes upon heating, thus shortening the length of the hydrocarbon carbon chain; due to SO4... 2- To HSO4 - and [MeSO4] CIP The transformation of SO₄²⁻ lowers the bond energy, making it more susceptible to breakage under attack from hydrocarbon molecules. This results in the production of a certain amount of H₂S and CO₂. Under high-temperature conditions, H₂S can react with free SO₄²⁻. 2- The reaction produces S2O3. 2- S2O3 2- Unstable sulfides can be produced under the action of hydrocarbons. Further action by hydrocarbons or water generates large amounts of H₂S and stable sulfides. The generated H₂S reacts with free SO₄²⁻.2- The reaction continues, producing thiosulfate; this step is known as the autocatalytic effect of H2S. The addition of nitrogen significantly dilutes the concentration of H2S, slowing the chemical reaction and thus reducing the rate of thermochemical reduction of sulfate, resulting in less hydrogen sulfide formation.

[0091] Thermochemical reduction reaction of sulfate:

[0092] SO4 2- +H2S=S2O3 2- +H2O (1)

[0093] S2O3 2- +RCH3+H2O=RSSCH3+2OH - (2)

[0094] RSSCH3 + 2H2 = RCH3 + 2H2S (3)

[0095] In summary, after the metal enters the solution, it generates metal ions. These metal ions catalyze the hydrodesulfurization and water-gas conversion reactions, and react with H+. + The formation of complexes lowers the bond energy of the SC bonds, thereby accelerating the thermochemical reduction of sulfate. The generated hydrogen sulfide further participates in the thermochemical reduction reaction of sulfate, further increasing the concentration of hydrogen sulfide, with an error margin of 8.11%–27.03%. The addition of nitrogen gas dilutes the concentration of hydrogen sulfide, thus slowing down its later autocatalytic effect, with an error margin of up to 5.41%. Therefore, to ensure the reliability of experimental results, the reactants must be isolated from the metal container and the pressurized nitrogen gas.

Claims

1. An experimental method for evaluating hydrogen sulfide production during a simulated thermal recovery process, comprising the following steps: S1. Place the sample to be tested in a ceramic container and remove the gas therein, then place the ceramic container in a lidded pressure-resistant stainless steel container. The bottom of the ceramic container is fitted with an end cap, and the top is sealed by a piston; The piston is provided with an exhaust port; Step S1 is performed as follows: Move the piston upwards to close the vent, then invert the ceramic container, open the end cap, place the sample to be tested inside, close the end cap and seal it; open the vent, push the piston downwards to expel the gas, and close the vent. S2. Heat the covered pressure-resistant stainless steel container to a set temperature; inject nitrogen into the inside of the covered pressure-resistant stainless steel container and the upper part of the ceramic container to the injection pressure of the thermal recovery process to simulate the thermal recovery process. S3. After the thermal recovery process is completed, the temperature is lowered and nitrogen is released. The gas generated in the ceramic container can then be detected.

2. The evaluation experimental method according to claim 1, characterized in that: The ceramic container is a temperature- and pressure-resistant ceramic container.

3. The evaluation experimental method according to claim 1 or 2, characterized in that: The ceramic container is the same size and shape as the lidded pressure-resistant stainless steel container.

4. The evaluation experimental method according to claim 1 or 2, characterized in that: The conditions for the thermal recovery process are as follows: Temperature ranges from 0 to 350℃, pressure ranges from 0 to 15 MPa, and time ranges from 0 to 72 hours.

5. The evaluation experimental method according to claim 1 or 2, characterized in that: In step S3, the gas is detected using a gas chromatograph.

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