Low-maturity shale oil conversion method based on in-situ electrochemical hydrocracking
By constructing a conductive catalytic network and utilizing formation water electrolysis to generate active hydrogen, combined with Joule thermal-assisted catalytic hydrocracking, the problems of high energy consumption and poor oil quality in the in-situ upgrading process of low-maturity shale oil have been solved, achieving low-temperature, rapid, and efficient shale oil conversion.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- XI'AN PETROLEUM UNIVERSITY
- Filing Date
- 2026-04-03
- Publication Date
- 2026-05-12
AI Technical Summary
In existing technologies, the in-situ upgrading process of low-maturity shale oil suffers from high energy consumption, poor oil quality, and lack of hydrogen source, resulting in low energy return rate, unstable products, and easy pore blockage.
By constructing a deep conductive catalytic network and using formation water as a hydrogen source, active hydrogen is produced by electrolysis under the action of a DC electric field. Combined with Joule heating-assisted catalytic hydrocracking, rapid hydrogenation conversion at low temperature is achieved.
It reduces the reaction activation energy, improves oil quality, reduces energy consumption, avoids pore blockage, and achieves efficient, low-cost, high-quality shale oil conversion.
Smart Images
Figure CN122012139A_ABST
Abstract
Description
Technical Field
[0001] This invention belongs to the field of oil and gas extraction technology, and particularly relates to a method for converting low-maturity shale oil based on in-situ electrochemical hydrocracking. Background Technology
[0002] Currently, in-situ refining (ICP) technology for low-maturity shale oil (Ro < 0.7%) mainly relies on electric heating rods for simple thermal cracking (Pyrolysis) to generate light oil and gas. However, this technology generally suffers from the following three major drawbacks: ① High temperature and high energy consumption: It requires heating to 300-500℃. Shale has slow thermal conductivity, and it takes several years to reach production capacity, resulting in an extremely low energy return on investment (EROI); ② Poor oil quality and heavy coking: Pure thermal cracking is a "dehydrogenation and carbonization" process, resulting in high olefin content in the products, instability, and a tendency to generate coke in the formation, clogging pores; ③ Lack of hydrogen source: There is no hydrogen underground, making hydrorefining impossible, resulting in high API weight and poor fluidity of the crude oil.
[0003] Therefore, there is an urgent need for a method to achieve low-cost, high-quality in-situ conversion of low-maturity shale oil. Summary of the Invention
[0004] Based on the above analysis, this application discloses a method for converting low-maturity shale oil based on in-situ electrochemical hydrocracking. It utilizes formation water / injected water as a hydrogen source and constructs a deep reaction bed through conductive catalytic fracturing fluid. Under the action of a DC electric field, it achieves a three-in-one synergistic effect of "electrolysis to produce active hydrogen + Joule heating assistance + catalytic hydrocracking", reducing the reaction activation energy by more than 50% and realizing low-temperature (<250℃), rapid, high-quality in-situ conversion of low-maturity shale oil.
[0005] To achieve the above objectives, this application discloses a method for converting low-maturity shale oil based on in-situ electrochemical hydrocracking, comprising the following steps:
[0006] S1. Constructing a deep conductive catalytic network: At least two fractured horizontal wells are set up in the target shale formation, one as an injection well and the other as a production well. A connected fracture network is formed in the reservoir of the two wells through a segmented fracturing process. A bifunctional conductive catalytic fracturing fluid is injected into the fracture network through the injection well and remains in the fractures to form a connected three-dimensional conductive catalytic network.
[0007] S2. Apply in-situ electric field: Using the casing of the injection well as the anode and the casing of the production well or the surface on the side of the production well as the cathode, connect a high-voltage DC power supply to establish an electric field on the three-dimensional conductive catalytic network.
[0008] S3. In-situ hydrocracking reaction: The electric field formed in S2 causes the formation water in the three-dimensional reaction network to undergo an electrochemical reaction, generating active hydrogen in situ; the active hydrogen serves as a hydrogen source and undergoes an in-situ hydrocracking reaction with kerogen in the low-maturity shale oil in the target shale section to generate light hydrocarbon oil and gas reaction products.
[0009] S4. Product Displacement and Extraction: The reaction products are extracted via the production well.
[0010] Furthermore, the bifunctional conductive catalytic fracturing fluid described in S1 includes a conductive proppant, a hydrogen evolution-cracking bifunctional catalyst, and an electrolyte. The addition amounts of each component in the bifunctional conductive catalytic fracturing fluid are as follows, by mass percentage: conductive proppant: 5%-15%; hydrogen evolution-cracking bifunctional catalyst: 0.5%-3%; electrolyte: 1%-5%.
[0011] Furthermore, the conductive support agent includes at least one or a combination of nano-graphite powder, multi-walled carbon nanotubes, and modified petroleum coke powder.
[0012] Furthermore, the hydrogen evolution-cracking bifunctional catalyst comprises at least one or a combination of nano-sized molybdenum sulfide or nickel-cobalt alloy.
[0013] Furthermore, the electrolyte is a potassium chloride solution or a sodium bicarbonate solution.
[0014] Furthermore, the applied electric field described in S2 results in an effective electric field strength of 0.5 ~ 2.0 V / cm in the formation.
[0015] Furthermore, the formation temperature during the reaction described in S3 is 150-250℃.
[0016] Furthermore, the duration of maintaining the applied electric field, as described in S2, is 3-6 months.
[0017] Furthermore, the target rock stratum described in S1 is a shale stratum with a vitrinite reflectance Ro < 0.7%.
[0018] And, a system for implementing the above-described conversion method, comprising:
[0019] Injection wells with casing as the anode, and production wells with casing or the surface as the cathode;
[0020] An injection device is used to inject conductive catalytic fracturing fluid into the injection well;
[0021] The high-voltage DC power supply has its positive and negative output terminals connected to the injection well and the production well respectively via cables.
[0022] Beneficial effects:
[0023] 1. Achieved "in-situ hydrogen supply": By cleverly utilizing formation water (pore water, primary water, etc. in the formation, which are regarded as "wastewater" in the processing), the problem of "hydrogen deficiency" in the traditional shale oil upgrading process is solved. No ground hydrogen injection facilities are required, and the safety is high.
[0024] 2. Breakthrough in "energy consumption bottleneck": By introducing an electrochemical catalytic mechanism, the starting temperature of kerogen pyrolysis is reduced by more than 100°C, significantly reducing heating energy consumption (estimated energy savings of 40%-60%).
[0025] 3. Improved "oil quality": The reaction mechanism has changed from "thermal cracking" to "hydrocracking," resulting in products with high saturated hydrocarbon content and low olefin and gum content. The oil is lighter and less prone to coking in the formation.
[0026] 4. A "three-dimensional reaction bed" was constructed: using nanofluid fracturing technology, electrodes and catalysts are made to penetrate deep into the micropores of the matrix, and the reaction contact area is thousands of times larger than that of traditional heating rod technology. Attached Figure Description
[0027] To more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings used in the description of the embodiments of the present invention will be briefly introduced below. 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.
[0028] Figure 1 This is a schematic geological profile of the three-dimensional conductive catalytic network described in this application;
[0029] Figure 2 This is a diagram of the in-situ hydrocracking reaction process of this application. Detailed Implementation
[0030] To make the technical problems solved, the technical solutions, and the beneficial effects 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.
[0031] Example 1: A method for converting low-maturity shale oil based on in-situ electrochemical hydrocracking, comprising the following steps:
[0032] S1. Constructing a deep conductive catalytic network: such as Figure 1As shown, at least two fractured horizontal wells are set in the target shale section 3 (i.e., the low-maturity shale layer containing low-maturity shale oil), one designated as injection well 4 and the other as production well 5. A connected fracture network 7 is formed in the reservoir of the two wells through a staged fracturing process. A bifunctional conductive catalytic fracturing fluid is injected into the fracture network through the injection well and remains in the fractures, forming a connected three-dimensional conductive catalytic network (the bifunctional conductive catalytic fracturing fluid shown can be pumped into injection well 4 by injection pump 2).
[0033] S1. Constructing a deep conductive catalytic network: As shown in Figure 1, at least two fractured horizontal wells are set in the target shale section 3, one designated as an injection well 4 and the other as a production well 5. A connected fracture network 7 is formed in the reservoir of the two wells through a segmented fracturing process. A bifunctional conductive catalytic fracturing fluid 15 is injected into the fracture network 7 through the injection well 4 and remains in the fractures, forming a connected three-dimensional conductive catalytic network.
[0034] The fractured horizontal well can be obtained through a segmented fracturing process for horizontal wells.
[0035] In this embodiment, the bifunctional conductive catalytic fracturing fluid includes a conductive proppant, a hydrogen evolution-cracking bifunctional catalyst, and an electrolyte. The conductive proppant includes at least one or a combination of nano-graphite powder, multi-walled carbon nanotubes, and modified petroleum coke powder, which acts to penetrate the fracture network and build microscopic conductive bridges. The hydrogen evolution-cracking bifunctional catalyst includes at least one or a combination of nano-molybdenum sulfide or nickel-cobalt alloy, which acts as a hydrogenation catalyst to improve hydrogen activity (HER) under electrochemical reactions. The electrolyte is a potassium chloride solution or a sodium bicarbonate solution; preferably, a high-concentration electrolyte solution is used to ensure formation conductivity. The combination of these components gives the bifunctional conductive catalytic fracturing fluid the dual properties of "hydrogen evolution activity" and "CC bond shearing activity."
[0036] In a further embodiment, the bifunctional conductive catalytic fracturing fluid includes a conductive proppant, a hydrogen evolution-cracking bifunctional catalyst, and an electrolyte. The addition amounts of each component in the bifunctional conductive catalytic fracturing fluid, by mass percentage, are: conductive proppant: 5%-15%; hydrogen evolution-cracking bifunctional catalyst: 0.5%-3%; electrolyte: 1%-5%. Specifically, the conductive proppant (5% ~ 15%) has the following lower limit (5%): ensuring the proppant can form a continuous electron transport channel (i.e., penetration threshold) in the fracture, avoiding interruption of the conductive network; and the upper limit (15%): preventing excessively high fracturing fluid viscosity, ensuring good pumpability, and enabling it to penetrate deep fracture networks.
[0037] Hydrogen evolution-cracking bifunctional catalyst (0.5% ~ 3%): Lower limit (0.5%): Ensure sufficient active sites to induce hydrogen production from formation water and kerogen cracking reaction, thereby reducing activation energy; Upper limit (3%): Considering the cost of nano-molybdenum sulfide or nickel-cobalt alloy, and that excessively high concentration may lead to nanoparticle agglomeration, affecting catalytic efficiency.
[0038] Electrolyte (1% ~ 5%): Lower limit (1%): Maintain the basic conductivity of formation water to ensure the smooth progress of the electrolysis hydrogen production reaction; Upper limit (5%): Avoid high concentrations of salts from causing salt precipitation blockage of formation pores or excessive corrosion of metal casing.
[0039] S2. Apply an in-situ electric field: such as Figure 1 The geological profile diagram of the three-dimensional conductive catalytic network shown uses the casing of injection well 4 as the anode (+) and the casing of production well 5 or the surface of the production well side as the cathode (-). A high-voltage DC power supply 1 is connected to establish an electric field on the three-dimensional conductive catalytic network.
[0040] In this embodiment, the applied electric field described in S2 creates an effective electric field strength of 0.5 to 2.0 V / cm in the formation. This electric field strength can both trigger electrochemical reactions and generate moderate Joule heating (an electrothermal effect), which raises and maintains the formation temperature at around 150-250°C.
[0041] It should be noted that the electric field strength mentioned above refers to the effective electric field strength formed in the formation. In practical applications, to achieve this electric field strength, the actual output voltage and current density of the surface power source will vary with factors such as well spacing and fracturing fluid concentration. For example, according to the physical formula E = U / d (electric field strength = voltage / well spacing): if the well spacing d is 100 meters (10,000 cm) and a voltage of 1000V is injected, the average electric field strength of the formation will be 0.1 V / cm.
[0042] Current density is a key metric for measuring the rate of electrochemical reactions (i.e., the speed of hydrogen production). At a given voltage, current density depends on the formation resistivity (determined by the concentration of the conductive fracturing fluid). The current density needs to prevent excessive current from causing overheating of the formation (excessive Joule heating) and wasting energy, while ensuring sufficient active hydrogen production.
[0043] Therefore, in practical engineering applications, the effective electric field strength applied to the three-dimensional conductive catalytic network is preferably 0.5 ~ 2.0 V / cm. To achieve the above effective field strength, the output voltage of the DC power supply needs to be adjusted according to the well distance between the injection well and the production well. Typically, the output voltage is set to 500V ~ 1500V, and the formation current density is controlled to be maintained at 5-10 A / m². Of course, the actual output voltage and current density may also vary depending on the scenario, and those skilled in the art can set them accordingly based on the requirements for achieving the effective electric field strength.
[0044] S3. In-situ hydrocracking reaction: such as Figure 2 As shown, the in-situ hydrocracking reaction specifically involves:
[0045] (1) The electric field generated by S2 causes the formation water in the three-dimensional reaction network to undergo an electrochemical reaction, generating active hydrogen in situ.
[0046] In this reaction process, the conductive support 11 and electrolyte in the bifunctional conductive catalytic cracking solution within the fracture network serve as conductive carriers. Under the action of the hydrogen evolution-cracking bifunctional catalyst 12, the formation water undergoes an electrolytic reduction reaction: 2H₂O + 2e⁻ - →2H + (Active hydrogen atom) + 2OH - (to obtain active hydrogen).
[0047] (2) Next, active hydrogen is used as a hydrogen source to react with kerogen 9 in low-maturity shale oil in the target shale section in an in-situ hydrocracking reaction to generate light hydrocarbon oil and gas reaction products.
[0048] In this reaction, kerogen undergoes hydrogenation (chain transfer): active hydrogen (H+) - The free radical quenching reaction rapidly attacks the fatty chains and heteroatom bonds (CS, CN) at the edge of the kerogen; among them, the hydrogen-cracking bifunctional catalyst 12 lowers the activation energy of CC bond breaking, so that the macromolecular kerogen is cracked into light liquid hydrocarbons 13 at a lower temperature (150-250℃).
[0049] S4. Product Displacement and Production: The reaction products are produced via the production wells: the viscosity of the converted light oil is significantly reduced, and the gas generated by electrolysis (O2, etc., generated at the anode) provides formation energy, assisting the crude oil to flow through the fracture network to the production wells (e.g., Figure 1 (As shown).
[0050] It can be seen that in this reaction process, the presence of hydrogen-cracking bifunctional catalyst and hydrogen ions results in a hydrocracking reaction temperature of 150-250℃ for kerogen, which is much lower than the reaction temperature of over 350℃ for traditional ICP. Furthermore, the electric field applied for 3-6 months as described in S2 of this application is much lower than the 3-5 years for traditional pyrolysis. At the same time, analysis of the reaction products shows that the kerogen conversion rate can reach over 40%, and the API gravity of the produced oil is increased from the original 30 to 40+ (light oil).
[0051] The above-described embodiments are only used to illustrate the technical solutions of the present invention, and are not intended to limit it. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention, and should all be included within the protection scope of the present invention.
Claims
1. A method for converting low-maturity shale oil based on in-situ electrochemical hydrocracking, characterized in that, Includes the following steps: S1. Constructing a deep conductive catalytic network: At least two fractured horizontal wells are set up in the target shale formation, one as an injection well and the other as a production well. A connected fracture network is formed in the reservoir of the two wells through a segmented fracturing process. A bifunctional conductive catalytic fracturing fluid is injected into the fracture network through the injection well and remains in the fractures to form a connected three-dimensional conductive catalytic network. S2. Apply in-situ electric field: Using the casing of the injection well as the anode and the casing of the production well or the surface on the side of the production well as the cathode, connect a high-voltage DC power supply to establish an electric field on the three-dimensional conductive catalytic network. S3. In-situ hydrocracking reaction: The electric field formed in S2 causes the formation water in the three-dimensional reaction network to undergo an electrochemical reaction, generating active hydrogen in situ; the active hydrogen serves as a hydrogen source and undergoes an in-situ hydrocracking reaction with kerogen in the low-maturity shale oil in the target shale section to generate light hydrocarbon oil and gas reaction products. S4. Product Displacement and Extraction: The reaction products are extracted via the production well.
2. The conversion method according to claim 1, characterized in that, The bifunctional conductive catalytic fracturing fluid described in S1 includes a conductive proppant, a hydrogen evolution-cracking bifunctional catalyst, and an electrolyte. The addition amounts of each component in the bifunctional conductive catalytic fracturing fluid, by mass percentage, are: conductive proppant: 5%-15%; hydrogen evolution-cracking bifunctional catalyst: 0.5%-3%. Electrolytes: 1%-5%.
3. The conversion method according to claim 2, characterized in that, The conductive support agent includes at least one or a combination of nano-graphite powder, multi-walled carbon nanotubes, and modified petroleum coke powder.
4. The conversion method according to claim 2, characterized in that, The hydrogen evolution-cracking bifunctional catalyst comprises at least one or a combination of nano-sized molybdenum sulfide or nickel-cobalt alloy.
5. The conversion method according to claim 2, characterized in that, The electrolyte is a potassium chloride solution or a sodium bicarbonate solution.
6. The conversion method according to claim 1, characterized in that, The applied electric field described in S2 results in an effective electric field strength of 0.5 ~ 2.0 V / cm in the formation.
7. The conversion method according to claim 1, characterized in that, The formation temperature during the reaction described in S3 is 150-250℃.
8. The conversion method according to claim 1, characterized in that, The electric field is maintained for 3-6 months as described in S2.
9. The conversion method according to claim 1, characterized in that, The target rock stratum described in S1 is a shale stratum with a vitrinite reflectance Ro < 0.7%.
10. A system for implementing the conversion method according to any one of claims 1-9, characterized in that, include: Injection wells with casing as the anode, and production wells with casing or the surface as the cathode; An injection device is used to inject conductive catalytic fracturing fluid into the injection well; The high-voltage DC power supply has its positive and negative output terminals connected to the injection well and the production well respectively via cables.