A method of upgrading shale oil

Abstract

The application discloses a method for upgrading shale oil, which comprises the following steps: selecting a shale oil block to be upgraded, wherein the shale oil block comprises a shale oil layer and a brittle stratum intercalated in the shale oil layer; drilling a horizontal well on the brittle stratum; performing hydraulic fracturing and carbon dioxide fracturing on the brittle stratum through the horizontal well, so as to fracture the brittle stratum and fill water used in the hydraulic fracturing and carbon dioxide fracturing fluid used in the carbon dioxide fracturing into fractures and matrix pores of the brittle stratum; and the carbon dioxide fracturing fluid carries a set amount of magnesium metal particles or aluminum metal particles. The magnesium / aluminum metal particles react with water in the stratum to generate high-temperature gas and release a large amount of heat, which enters the fractures and matrix pores in the stratum, so that part of the cheese root in the crude oil is cracked into light hydrocarbon, and the crude oil mobility is enhanced, thereby achieving the purpose of upgrading the medium-low maturity shale oil.

Description

Technical Field

[0001] This invention relates to the field of petroleum extraction technology, and more particularly to a method for modifying shale oil. Background Technology

[0002] For medium- to low-maturity shale oil, CN109519158A describes a method where carbon monoxide and oxygen are injected into the formation to produce high-temperature carbon dioxide gas. Extraction relies on the in-situ generated carbon dioxide from the shale, offering strong controllability. Pressure and temperature can be controlled by adjusting the injection volume and flow rate of two producing wells and the oxygen-enriched gas, thus promoting the formation of a carbon dioxide-mixed oil zone for optimal oil displacement and upgrading. CN109100375A describes an evaluation method for nano-adjuvants used in in-situ underground upgrading of shale oil, addressing the technical challenge of characterizing the thermocatalytic process of kerogen by nano-catalysts in existing technologies. CN1676870A describes a method using a surface-based well cluster, connected by fracturing. High-temperature steam (400–700°C) is introduced into the injection wells to exchange heat with the shale oil, heating the formation and causing it to crack and produce shale oil and gas, which is then carried to the surface by low-temperature steam or water. CN110005390A provides a method for in-situ conversion and extraction of shale oil and gas with large well spacing in medium- and low-maturity shale oil. This method has advantages such as large heating well spacing and high heat transfer efficiency through shale oil, and is suitable for the commercial development of shale oil with a thickness greater than 4 meters. CN109113699A provides an in-situ development method for deeper shale oil deposits. It uses preset standards to determine favorable strata and areas, thus providing targets and directions for the in-situ lightweight development of shale oil, reducing exploration and development risks. Further optimization design, such as well placement, is carried out within the favorable areas. Then, a pumping production mode is used to improve the efficiency of in-situ lightweight development of shale oil. Heating is performed according to a preset heating program, and temperature changes are monitored in real time to maximize crude oil production.

[0003] The aforementioned research methods either convert electrical energy into heat and transfer it to the formation through electric heating, or inject high-energy fluids (including water vapor, high-temperature carbon dioxide, carbon monoxide, and oxygen) into the formation to cause kerogen pyrolysis or alter the physical properties of low- to medium-maturity shale oil (oil shale), thereby achieving the goal of upgrading shale oil. However, current development results show unsatisfactory performance, limited industrial application, and low oil recovery rates. Furthermore, these methods require significant electrical energy consumption or the construction of dedicated pipelines to transport high-temperature gases underground, making them less feasible and difficult to promote. Therefore, the industry urgently needs to find new in-situ upgrading methods for low- to medium-maturity shale oil to improve its recovery rate. Summary of the Invention

[0004] The purpose of this invention is to propose a method for refining shale oil, which can increase the mobility of crude oil, thereby achieving the goal of refining medium- and low-maturity shale oil.

[0005] To achieve the above objectives, the present invention provides a method for modifying shale oil, comprising:

[0006] Select a shale oil block to be upgraded, the shale oil block to be upgraded includes a shale oil layer and brittle formations interposed in the shale oil layer;

[0007] Horizontal drilling was performed on the brittle formation.

[0008] The brittle formation is hydraulically and carbon dioxide fracturing is performed through the horizontal drilling to fracture the brittle formation and to fill the fractures and matrix pores of the brittle formation with the water used in the hydraulic fracturing process and the carbon dioxide fracturing fluid used in the carbon dioxide fracturing process; the carbon dioxide fracturing fluid carries a set amount of magnesium or aluminum metal particles.

[0009] According to a preferred embodiment of the present invention, hydraulic fracturing and carbon dioxide fracturing of the brittle formation through the horizontal drilling includes:

[0010] The hydraulic fracturing is performed first, followed by the carbon dioxide fracturing; or, the carbon dioxide fracturing is performed first, followed by the hydraulic fracturing.

[0011] According to a preferred embodiment of the present invention, the brittle formation includes multiple predetermined sections, and hydraulic fracturing and carbon dioxide fracturing of the brittle formation through the horizontal drilling includes:

[0012] For a specific section of the brittle formation, fracturing is first performed using either hydraulic fracturing or carbon dioxide fracturing, followed by fracturing using the other method, to complete the fracturing of the current section. This process is repeated until all specified sections of the brittle formation are fracturing.

[0013] According to a specific embodiment of the present invention, the brittle formation includes multiple predetermined sections, and hydraulic fracturing and carbon dioxide fracturing of the brittle formation through horizontal drilling includes:

[0014] For multiple designated sections of the brittle formation, one of the hydraulic fracturing and the carbon dioxide fracturing methods is first used to continuously perform multi-stage fracturing, and then the other fracturing method is used to perform fracturing until all designated sections of the brittle formation are fracturing.

[0015] According to one specific embodiment of the present invention, the thermal evolution maturity of the brittle strata ranges from 0.5% to 1.0%.

[0016] Preferably, the molar ratio of water used in hydraulic fracturing to magnesium metal particles in carbon dioxide fracturing is 1 to 3; and the molar ratio of water used in hydraulic fracturing to aluminum metal particles in carbon dioxide fracturing is 2 to 4.

[0017] Preferably, the method involves performing hydraulic fracturing first and then carbon dioxide fracturing, and further includes the following steps before performing carbon dioxide fracturing after hydraulic fracturing:

[0018] A front piston is placed in the horizontal well, then a separation fluid is injected into the well, and then a rear piston is placed in the well. The separation fluid is used to prevent the magnesium or aluminum metal particles from reacting with water before the carbon dioxide fracturing is performed.

[0019] Specifically, the thickness of the shale oil layer is greater than 10 meters.

[0020] Specifically, the brittle strata are carbonate and / or siltstone, the organic carbon content in the brittle strata is greater than 6%, and the thickness of the brittle strata is 3-6 meters.

[0021] According to a preferred embodiment of the present invention, the size of the magnesium metal particles or the aluminum metal particles is at the micro-nano level.

[0022] The beneficial effects of this invention are as follows:

[0023] This invention utilizes the reaction of magnesium / aluminum metal particles with water in the formation to generate high-temperature gas and release a large amount of heat. This gas enters the fractures and matrix pores in the formation, causing some of the kerogen in the crude oil to crack into light hydrocarbons, thereby enhancing the mobility of the crude oil and achieving the purpose of upgrading low-maturity shale oil.

[0024] Furthermore, this method employs a two-stage fracturing process. When hydraulic fracturing is performed first and then carbon dioxide fracturing is performed, in order to prevent magnesium / aluminum metal particles from reacting with water prematurely, a piston is driven into the wellbore after hydraulic fracturing, followed by the injection of a separator fluid (the separator fluid is used to prevent magnesium / aluminum metal particles from reacting with water before carbon dioxide fracturing), and then another piston is added before carbon dioxide fracturing is carried out.

[0025] This method is easy to streamline, and the required raw material, nano-magnesium / aluminum metal, is easy to prepare. It can effectively utilize medium- and low-maturity shale oil and provide a new approach for in-situ shale oil upgrading.

[0026] The present invention has other features and advantages, which will be apparent from or will be set forth in detail in the accompanying drawings and the following detailed description, which together serve to explain the particular principles of the invention. Attached Figure Description

[0027] The above and other objects, features and advantages of the present invention will become more apparent from the more detailed description of exemplary embodiments of the invention in conjunction with the accompanying drawings.

[0028] Figure 1 This is a flowchart of a method for modifying shale oil according to an embodiment of the present invention.

[0029] Figures 2 to 5 A schematic diagram of different steps in a method for modifying shale oil according to Embodiment 1 of the present invention is shown.

[0030] Figures 6 to 9 A schematic diagram of different steps in a method for modifying shale oil according to Embodiment 2 of the present invention is shown.

[0031] Attached icon number

[0032] 1-Shale oil layer; 2-Brittle formation; 3-Horizontal drilling; 4-Water; 5-Nano magnesium / aluminum metal particles; 6-Heat and high-temperature gas; 7-Oil and gas molecules; 8-Front-mounted piston Detailed Implementation

[0033] The embodiments of the present invention will be described in detail below with reference to the accompanying drawings and examples, thereby enabling a full understanding of how the present invention uses technical means to solve technical problems and achieve technical effects, and allowing for implementation accordingly. It should be noted that, as long as there is no conflict, the various embodiments and features in each embodiment of the present invention can be combined with each other, and the resulting technical solutions are all within the protection scope of the present invention.

[0034] The purpose of this invention is primarily to address the problems of low-to-medium maturity shale oil, such as its high proportion of solid organic matter, high viscosity, low gas-oil ratio, and poor fluidity. This invention proposes a method for upgrading shale oil using the reaction products of magnesium / aluminum metal particles and water. The reaction of magnesium / aluminum metal particles with water generates a large amount of heat and high-temperature gaseous products. These products enter formation fractures and matrix pores, thereby altering the physical properties of low-to-medium maturity shale oil. This promotes the cracking of some kerogen into light hydrocarbons, enhancing the oil's mobility and achieving the goal of upgrading low-to-medium maturity shale oil.

[0035] To achieve the above objectives, one embodiment of the present invention provides a method for modifying shale oil, referring to... Figure 1 The method includes:

[0036] Select a shale oil block to be upgraded, the shale oil block to be upgraded includes a shale oil layer and brittle formations interposed in the shale oil layer;

[0037] Horizontal drilling was performed on the brittle formation.

[0038] The brittle formation is hydraulically and carbon dioxide fracturing is performed through the horizontal drilling to fracture the brittle formation and to fill the fractures and matrix pores of the brittle formation with the water used in the hydraulic fracturing process and the carbon dioxide fracturing fluid used in the carbon dioxide fracturing process; the carbon dioxide fracturing fluid carries a set amount of magnesium or aluminum metal particles.

[0039] In an optional example, performing hydraulic fracturing and carbon dioxide fracturing on the brittle formation through the horizontal drilling includes: performing hydraulic fracturing first and then carbon dioxide fracturing; or performing carbon dioxide fracturing first and then hydraulic fracturing.

[0040] In a specific example, the brittle formation includes multiple designated sections. The hydraulic fracturing and carbon dioxide fracturing of the brittle formation by the horizontal drilling includes: for one of the designated sections of the brittle formation, fracturing is first performed using one of the hydraulic fracturing and carbon dioxide fracturing methods, and then fracturing is performed using the other fracturing method to complete the fracturing of the current designated section. The above steps are repeated until all designated sections of the brittle formation are fracturing.

[0041] In another specific example, the brittle formation includes multiple designated sections. The hydraulic fracturing and carbon dioxide fracturing of the brittle formation by the horizontal drilling includes: for the multiple designated sections of the brittle formation, firstly, using one of the fracturing methods, hydraulic fracturing and carbon dioxide fracturing, to continuously perform multi-stage fracturing, and then using the other fracturing method, until all designated sections of the brittle formation are fracturing.

[0042] In a preferred embodiment, the thermal evolution maturity of the brittle strata ranges from 0.5% to 1.0%.

[0043] In a preferred embodiment, the molar ratio of water used in hydraulic fracturing to magnesium particles in carbon dioxide fracturing is 1 to 3; and the molar ratio of water used in hydraulic fracturing to aluminum particles in carbon dioxide fracturing is 2 to 4.

[0044] In an optional embodiment, the method employs hydraulic fracturing followed by carbon dioxide fracturing. Before performing carbon dioxide fracturing after hydraulic fracturing, the method further includes: placing a front piston in the horizontal well, injecting a release fluid into the well, and then placing a rear piston in the well. The release fluid is used to prevent the magnesium or aluminum metal particles from reacting with water before performing carbon dioxide fracturing.

[0045] In the preferred embodiment, the thickness of the shale oil layer is greater than 10 meters.

[0046] In a preferred embodiment, the brittle stratum is carbonate and / or siltstone, the organic carbon content in the brittle stratum is greater than 6%, and the thickness of the brittle stratum is 3-6 meters.

[0047] In a preferred embodiment, the size of the magnesium or aluminum metal particles is at the micro-nano level.

[0048] This invention utilizes the reaction of magnesium / aluminum metal particles with water in the formation to generate high-temperature gas and release a large amount of heat. This gas enters the fractures and matrix pores in the formation, causing some of the kerogen in the crude oil to crack into light hydrocarbons, thereby enhancing the mobility of the crude oil and achieving the purpose of upgrading low-maturity shale oil.

[0049] Furthermore, this method employs a two-stage fracturing process. When hydraulic fracturing is performed first and then carbon dioxide fracturing is performed, in order to prevent magnesium / aluminum metal particles from reacting with water prematurely, a piston is driven into the wellbore after hydraulic fracturing, followed by the injection of a separator fluid (the separator fluid is used to prevent magnesium / aluminum metal particles from reacting with water before carbon dioxide fracturing), and then another piston is added before carbon dioxide fracturing is carried out.

[0050] This method is easy to streamline, and the required raw material, nano-magnesium / aluminum metal, is easy to prepare. It can effectively utilize medium- and low-maturity shale oil and provide a new approach for in-situ shale oil upgrading.

[0051] Example 1

[0052] Reference Figures 2 to 5 The method will be described below with a specific example.

[0053] In-situ upgrading of low-maturity shale oil in favorable zones of the Ordos Basin:

[0054] 1. For example Figure 2 As shown, the preferred shale oil blocks are those with medium to low maturity, thermal evolution maturity ranging from 0.5% to 1.0%, and organic carbon content greater than 6%, with shale oil layer 1 having a thickness of more than 10m.

[0055] 2. For example Figure 2As shown, a horizontal well 3 was drilled to carry out fracturing operations on the brittle formation 2, which is adjacent to the medium-low maturity shale oil layer and consists of dense carbonate and siltstone. The brittle formation 2 is about 4m thick and is sandwiched in the shale oil layer 1.

[0056] 3. For example Figure 3 As shown, after the horizontal well is completed, the brittle formation 2 is fractured by a segmented hydraulic fracturing method (fracture segment 2 is shown in the figure). At this time, the formation fractures (formed by fracturing) and the matrix are filled with water 4.

[0057] 4. For example Figure 4 As shown, a front piston is placed in the horizontal well 3, and a separator fluid (liquid nitrogen, liquid carbon dioxide, or other liquids that do not react with water) is injected. The separator spacing can be initially set at 100m, followed by the placement of a rear piston. Then, carbon dioxide fracturing is carried out. The carbon dioxide fracturing fluid carries a certain amount of nano-magnesium / aluminum metal particles 5 (powder) and is injected into the fractured formation in stages. The amount of nano-magnesium / aluminum metal particles is determined according to the water volume of the hydraulic fracturing operation. Generally, a metal particle molar ratio to water molar ratio of 1:2 is adopted, that is, 1 mole of nano-magnesium metal particles is mixed with 2 moles of water, and 1 mole of nano-aluminum metal particles is mixed with 3 moles of water.

[0058] 5. For example Figure 5 As shown, in fractured formations, nano-magnesium metal particles react with water, generating a large amount of heat and high-temperature gas 6, which enters the fractured formation and matrix pores. The reaction process is as follows:

[0059] Mg + 2H₂O → Mg(OH)₂ + H₂ (high-temperature gas) + heat

[0060] The reaction between nano-aluminum metal particles and water follows the following process:

[0061] 2Al + 6H₂O = 2Al(OH)₃ + 3H₂ (high-temperature gas) + heat

[0062] The heat generated after the reaction can alter the viscosity of medium- to low-maturity shale oil, while simultaneously promoting the cracking of kerogen into light hydrocarbons. The generated high-temperature hydrogen can enter fractures and matrix pores, effectively reducing shale oil viscosity and driving oil and gas molecules to horizontal drilling, thereby achieving efficient oil recovery and increasing the recovery rate.

[0063] Example 2

[0064] Reference Figures 6 to 9 The method will now be described with another specific example.

[0065] In-situ upgrading of low-maturity shale oil in favorable zones of the Songliao Basin:

[0066] 1. For example Figure 6As shown, the preferred shale oil blocks are those with medium to low maturity, thermal evolution maturity ranging from 0.5% to 1.0%, organic carbon content greater than 6%, and shale oil layer thickness of more than 15m.

[0067] 2. For example Figure 6 As shown, a horizontal well 3 was drilled to carry out fracturing operations on the brittle formations such as carbonate rocks adjacent to the medium-low maturity shale oil. The brittle formation 2 has a single layer thickness of about 5m and is sandwiched in the shale oil layer 1.

[0068] 3. For example Figure 7 As shown, after the horizontal well is completed, the brittle formation 2 is fractured by a segmented carbon dioxide fracturing method. The carbon dioxide fracturing fluid carries magnesium / aluminum metal particles 5 (powder) to fracture the formation. At this time, the formation fractures are filled with magnesium / aluminum metal particles 5.

[0069] 4. For example Figure 8 As shown, hydraulic fracturing is performed into the fractured formation. The amount of water used in hydraulic fracturing is determined based on the amount of magnesium / aluminum metal powder in the carbon dioxide-carrying fluid used in the fracturing operation. Generally, a metal particle molar ratio to water molar ratio of 1:2 is used, that is, 1 mole of nano-magnesium metal particles is used with 2 moles of water, and 1 mole of nano-aluminum metal particles is used with 3 moles of water.

[0070] 5. For example Figure 9 As shown, water enters the fractured strata and reacts with nano-magnesium metal particles, generating a large amount of heat and high-temperature gas that enters the fractured strata and matrix pores. The reaction process is as follows:

[0071] Mg + 2H₂O → Mg(OH)₂ + H₂ (high-temperature gas) + heat

[0072] The reaction process with nano-aluminum metal particles is as follows:

[0073] 2Al + 6H₂O = 2Al(OH)₃ + 3H₂ (high-temperature gas) + heat

[0074] The heat generated after the reaction can alter the viscosity of medium- to low-maturity shale oil, while simultaneously promoting the cracking of kerogen into light hydrocarbons. The generated high-temperature hydrogen gas can enter the fractures and matrix pores, effectively reducing the viscosity of shale oil and driving oil and gas molecules into the wellbore for extraction.

[0075] 6. After completing one stage of fracturing, repeat steps 3 to 5 to achieve the goal of upgrading shale oil after multi-stage fracturing and improve the recovery rate.

[0076] In this invention, magnesium / aluminum metal particles react violently with water in the fractures and matrix pores after encountering fracturing. The heat and high-temperature gas generated enter the fractures and matrix pores in the formation, causing changes in the composition of shale oil, which has a low proportion of movable oil, a high proportion of solid organic matter, and a low gas-oil ratio. Driven by the high-temperature gas, the oil enters the horizontal well, achieving the goal of extracting shale oil.

Claims

1. A method for modifying shale oil, characterized in that, The method includes: Select a shale oil block to be upgraded, the shale oil block to be upgraded includes a shale oil layer and brittle formations interposed in the shale oil layer; Horizontal drilling was performed on the brittle formation. The brittle formation is fractured by hydraulic fracturing and carbon dioxide fracturing through horizontal drilling, thereby fracturing the brittle formation and filling the fractures and matrix pores of the brittle formation with water used in the hydraulic fracturing process and carbon dioxide fracturing fluid used in the carbon dioxide fracturing process; the carbon dioxide fracturing fluid carries a predetermined amount of magnesium or aluminum metal particles. The hydraulic fracturing and carbon dioxide fracturing of the brittle formation through the horizontal drilling includes: The hydraulic fracturing is performed first, followed by the carbon dioxide fracturing; or, the carbon dioxide fracturing is performed first, followed by the hydraulic fracturing. The brittle formation includes multiple defined sections, and hydraulic fracturing and carbon dioxide fracturing of the brittle formation through horizontal drilling includes: For multiple designated sections of the brittle formation, one of the hydraulic fracturing and the carbon dioxide fracturing methods is first used to continuously perform multi-stage fracturing, and then the other fracturing method is used to perform fracturing until all designated sections of the brittle formation are fracturing. The thermal evolution maturity of the brittle formation ranges from 0.5% to 1.0%; the molar ratio of water used in hydraulic fracturing to magnesium particles in carbon dioxide fracturing is 1 to 3; and the molar ratio of water used in hydraulic fracturing to aluminum particles in carbon dioxide fracturing is 2 to 4. The method employs hydraulic fracturing followed by carbon dioxide fracturing, and further includes the following steps after hydraulic fracturing and before carbon dioxide fracturing: A front piston is placed in the horizontal well, then a separator fluid is injected into the horizontal well, and then a rear piston is placed in the horizontal well. The separator fluid is used to prevent the magnesium or aluminum metal particles from reacting with water before the carbon dioxide fracturing is performed.

2. The method for modifying shale oil according to claim 1, characterized in that, The thickness of the shale oil layer is greater than 10 meters.

3. The method for modifying shale oil according to claim 1, characterized in that, The brittle strata are carbonate and / or siltstone, the organic carbon content in the brittle strata is greater than 6%, and the thickness of the brittle strata is 3-6 meters.

4. The method for modifying shale oil according to claim 1, characterized in that, The size of the magnesium or aluminum metal particles is at the micro-nano level.

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