Fracturing flow-back fluid cleaning treatment and heavy oil thermal recovery integrated experiment system and method

Abstract

The invention discloses a fracturing flow-back fluid cleaning treatment and heavy oil thermal recovery integrated experiment system and method, and the system mainly comprises a flow-back fluid standing box, a photocatalyst suspension tank, an intermittent peristaltic pump, a solar simulator, a condensing lens, a photoreactor, a photo-thermal cavity, a constant-temperature vaporization furnace, a heat preservation box, a sand filling pipe, a metering container and other components. The invention aims to provide a coupling process of fracturing flow-back liquid degradation treatment and thickened oil hot steam viscosity reduction exploitation for researchers and professional practitioners in related fields, so that the researchers can conveniently explore internal process parameters and a mechanism of structural optimization and enhancement of solar comprehensive utilization or thermal recovery of thickened oil to improve recovery efficiency. And meanwhile, a leading-edge application normal form can be provided for cascade distribution and comprehensive utilization of solar energy in the field of oil-gas field development. The system has the advantages of high integration level, convenience in use, good reliability, low cost and the like.

Description

Technical Field

[0001] The invention belongs to the field of oil and gas field development, and in particular relates to an integrated experimental system and method for clean treatment of fracturing flowback fluid and thermal recovery of heavy oil. Background Art

[0002] In the process of oil and gas well development in the mine, injecting fracturing fluid into the underground rock formation through high-pressure equipment to create cracks is one of the key processes in drilling engineering. The addition of fracturing fluid can increase the internal space and pore structure of the rock formation, reduce the flow resistance of natural gas, oil, etc. in the formation, and at the same time, the proppant components such as sand and alumina mixed in the fracturing fluid can maintain the high gap characteristics in the rock formation, which is conducive to the continuous development of fixed-point gas reservoirs. However, since fracturing fluid usually has the characteristics of high mineralization, high viscosity and high COD, the treatment of fracturing backflow fluid has always been a difficult problem in the oil and gas industry. At present, the main treatment methods for it are external discharge that meets the standards, reinjection and utilization, and standby after treatment. Because there are more organic and inorganic impurities in the backflow fluid and usually more bacteria, whether it is directly discharged or recycled, batch treatment through oxidation process and reducing its COD value and pollution hazards are one of the essential steps.

[0003] Usually, land areas with rich oil and gas reservoirs are located in remote areas with abundant solar energy resources. Solar-driven photocatalytic technology is currently a cutting-edge technology, which has been recognized by many technical experts because of its mild reaction conditions, green and pollution-free, and low cost. Its main principle is to use highly active photocatalysts (such as TiO2, C3N4, CdS, CuZnS, etc.) to produce a large number of highly oxidizing hydroxyl radicals in the solution under the excitation of photons in the ultraviolet and near-infrared regions of solar energy, which can well convert organic matter in pollutant aqueous solutions into low-carbon carbon dioxide, water or other inorganic substances, thereby reducing the COD value in pollutants. This technology is widely used in water purification and oilfield chemical reagents.

[0004] In addition, for the process of oil and gas extraction, oil and gas will be extracted after fracturing. For crude oil with high viscosity, that is, heavy oil with an average viscosity of 100 mPas, the method of heating the main body of the oil layer and greatly reducing its viscosity by injecting water vapor is the most widely used method in heavy oil extraction. However, the development of heavy oil requires a large amount of water vapor, and its cost can account for more than 75% of the entire process cost. Most of the previous methods use direct use of fuel, gas boilers, and grid electricity heating to achieve water gasification, which will be accompanied by a large amount of carbon emissions. And for more arid areas, the source of water resources is still a more difficult problem. Therefore, how to build a green and clean heating method and obtain recyclable water resources on site for continuous and efficient viscosity reduction of heavy oil at the downstream end of the extraction operation is an important technical bottleneck in the field of oil and gas field development. Summary of the invention

[0005] The purpose of the present invention is to provide an integrated experimental system and method for the clean treatment of fracturing return fluid and thermal recovery of heavy oil. While using photocatalytic technology to effectively degrade and purify organic matter, bacteria and deep oil pollution in fracturing return fluid, purified water is directly used as a water source to vaporize water vapor for heating and viscosity reduction of heavy oil. The above light reaction and thermal reaction are just based on the cascade complementary absorption and utilization of solar energy, without the need for additional energy input, which greatly reduces the technical cost of thermal recovery of heavy oil and the pressure of environmental carbon reduction. It can provide a coupling process for the degradation treatment of fracturing return fluid and the coordinated viscosity reduction of heavy oil with hot steam for scientific researchers and practitioners in related fields, which is convenient for researchers to explore the internal process parameters and the structural optimization mechanism of reaction components, and at the same time, it can provide an application paradigm for the cascade distribution and comprehensive utilization of solar energy in oil and gas reservoirs.

[0006] In order to achieve the above object, the present invention adopts the following technical solution: The fracturing return fluid clean treatment and heavy oil thermal recovery integrated experimental system includes a return fluid still box, an axial flow pump is arranged at the downstream end of the return fluid still box, a differential pressure flowmeter is arranged at the downstream end of the axial flow pump, a photocatalyst suspension tank is arranged at the downstream end of the differential pressure flowmeter, an intermittent peristaltic pump is arranged downstream of the photocatalyst suspension tank, and a photoreactor is arranged downstream of the intermittent peristaltic pump; a sapphire window is arranged on the middle top layer of the photoreactor, and an array prism is arranged on the bottom layer; a separation tank is arranged at the downstream end of the photoreactor, and a solar simulator is arranged on the top of the photoreactor and a focusing lens; a diaphragm pump is arranged downstream of the separation tank, the diaphragm pump is directly connected to the photothermal cavity, a first state monitor is arranged at the downstream end of the photothermal cavity, a constant temperature vaporization furnace is arranged at the downstream end of the first state monitor, and a mixing buffer cavity is arranged at the downstream end of the constant temperature vaporization furnace; a high-pressure nitrogen bottle and an explosion-proof gas flowmeter are arranged at the upstream end of the mixing buffer cavity respectively; a second state monitor is arranged at the downstream end of the mixing buffer cavity, a sand filling pipe is arranged at the downstream end of the second state monitor, the sand filling pipe is placed inside the insulation box, and a metering container is arranged at the tail of the sand filling pipe.

[0007] A further improvement of the present invention is that the fracturing flowback fluid retrieved from the oil field site is left to stand in a flowback fluid standing box for 1 hour to ensure that solid impurities in the flowback fluid are removed.

[0008] A further improvement of the present invention is that a TiO2 photocatalyst particle water suspension with a concentration of 1 mg / mL is placed in the photocatalyst suspension tank, an axial flow pump draws the supernatant of the backflow liquid standing box into the pipeline, and a differential pressure flow meter selects to compound different volume ratios of backflow liquid and photocatalyst particle suspension according to actual degradation performance.

[0009] A further improvement of the present invention is that the solar photons emitted by the solar simulator are further transmitted to the sapphire window through the focusing effect of the focusing lens, and the focusing ratio is above 100; the intermittent peristaltic pump is used to control the flow rate of the backflow liquid and the photocatalyst particle mixed liquid flowing from the photocatalyst suspension tank, and at the same time, the start and stop time ratio of the intermittent peristaltic pump is controlled according to the actual degradation performance feedback; the height of the array prism in the photoreactor is 5mm, which is used to form a local micro-turbine environment when the mixed liquid flows through the array prism.

[0010] A further improvement of the present invention is that the mixed liquid that completes the photoreaction in the photoreactor completes the solid-liquid separation process in the downstream separation tank, the supernatant after degradation treatment completes the vaporization process in the photothermal chamber, and the diaphragm pump needs to control the flow rate below 20mL / min; a black carbon gel film is placed at the bottom of the photothermal chamber to enhance the photothermal absorption and thermal conversion effects; the first state monitor is used to monitor the temperature, pressure and water content information of the steam in the photothermal chamber in real time.

[0011] A further improvement of the present invention is that the photoreactor and the photothermal cavity form a complementary relationship in the utilization of the solar energy spectrum, and absorb the spectrum ranges of 250nm-500nm and 500nm-2500nm respectively.

[0012] The invention is further improved in that the constant temperature vaporization furnace is used to further adjust the temperature and pressure of the steam according to the experimental parameter requirements; the core compressed by quartz sand is used in the sand filling tube to simulate the underground rock formation, and the core treated with saturated water and saturated oil is placed in the sand filling tube, and the heat preservation box is used to simulate the real-time temperature of the underground environment in situ, and the temperature range that can be set is 25 o C-1000 o Between C.

[0013] A further improvement of the present invention is that inert nitrogen is used as a carrier gas to be injected into the sand filling tube; an explosion-proof gas flow meter is used to control the high-pressure nitrogen released from the high-pressure nitrogen bottle, and the mixed gas of nitrogen and water vapor enters the rear end together after being evenly mixed in the mixing buffer chamber; a second state monitor is used to detect the gas pressure and temperature at the inlet end of the sand filling tube.

[0014] A further improvement of the present invention is that the volume flow rate of heavy oil thermal recovery is obtained according to a metering container, and the thermal recovery performance under characteristic parameter conditions is measured by comparing the produced oil volume with the total saturated oil volume.

[0015] Fracturing flowback fluid clean treatment and heavy oil thermal recovery integrated experimental methods, including: A 1 mg / mL TiO2 photocatalyst particle water suspension is placed in a photocatalyst suspension tank and stirred continuously. The fracturing backflow fluid retrieved from the site is poured into the backflow fluid standing box as an experimental sample and left to stand for more than 24 hours to ensure that the gravel in it is completely settled. For the experimental core, 40-100 mesh silica particles are compressed as simulated cores, which are then saturated with water and oil and placed in a sand filling tube, and the total oil content in the simulated core is recorded. When the system starts running, the backflow fluid is The fracturing backflow liquid in the static box is pumped into the photocatalyst suspension tank by an axial flow pump, and the volume ratio and corresponding concentration of the two liquids are adjusted by a differential pressure flowmeter; the mixed liquid is transported to the photoreactor through an intermittent peristaltic pump to participate in the photochemical reaction, and the array prisms set therein form a local micro-turbulence environment when the mixed liquid flows through the array prisms; the solar simulator emits a full-band spectrum, and the emitted full-band photons are concentrated by a focusing lens and radiated to the reaction suspension through a sapphire window, and the ultraviolet light and part of the visible light photons are Under the excitation, the photocatalyst TiO2 generates holes and correspondingly generates hydroxyl radicals in the base liquid; the reaction liquid after the reaction enters the separation tank for static separation, and after the photocatalyst settles, the diaphragm pump pumps the supernatant in the separation tank into the photothermal cavity for photothermal conversion, and uses the unused spectrum of the photoreactor to drive the photothermal conversion, and converts low-flow liquid water into water vapor. The first state monitor is used to monitor the temperature and pressure state of this test section; the constant temperature vaporization furnace further adjusts the temperature and pressure range of the steam according to the test requirements of the experiment; At the same time, the nitrogen stored in the high-pressure nitrogen bottle enters the mixing buffer chamber after passing through the explosion-proof gas flowmeter and mixes with the hot steam to serve the purpose of carrier gas and pressurization; the mixed gas coming out of the mixing buffer chamber is directly injected into the sand filling pipe, and the insulation box controls the temperature range of the sand filling pipe; the second state monitor monitors the temperature and pressure of the mixed gas at the inlet of the sand filling pipe. After the steam heating and viscosity reduction treatment, the heavy oil pre-filled in the sand filling pipe is continuously displaced, and the volume of the displaced heavy oil is measured in the metering container, and the performance under different operating parameters is compared.

[0016] Compared with the prior art, the present invention has at least the following beneficial technical effects: 1. The present invention realizes the clean photocatalytic treatment of oil and gas reservoir fracturing return fluid and the stable vaporization of purified water through the cascade distribution of solar energy and uses it in the thermal recovery and displacement process of heavy oil. The whole experiment forms resource complementarity, greatly reduces the cost of heavy oil thermal recovery and solves the problem of return fluid treatment.

[0017] 2. The system of the present invention can be used for a wide range of experimental studies, not limited to a specific type of photocatalyst. The regions and downhole conditions of the fracturing backflow fluid are allowed to differ, the simulated underground core properties and the state of the steam used can be simultaneously regulated in a wide range of parameters, and the system has strong adaptability.

[0018] 3. The system of the present invention directly simulates the efficient use of solar energy, and uses the spectral absorption differences of light reaction and thermal conversion to form a complementary integrated system, thereby improving the comprehensive utilization efficiency of solar energy and expanding the technical application of solar energy in the field of oil and gas field development, greatly alleviating the carbon emission pressure in actual oil and gas field development. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] In order to more clearly illustrate the specific implementation methods of the present invention or the technical solutions in the prior art, the drawings required for use in the specific implementation methods or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are some implementation methods of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0020] Figure 1 It is a schematic diagram of the process flow of the experimental system of the present invention; Figure 2 It is a schematic diagram of the local structure of the photoreactor in the experimental system of the present invention.

[0021] Description of reference numerals: 1 is a back-drainage still box, 2 is an axial flow pump, 3 is a differential pressure flow meter, 4 is a photocatalyst suspension tank, 5 is an intermittent peristaltic pump, 6 is a solar simulator, 7 is a focusing lens, 8 is a sapphire window, 9 is a photoreactor, 10 is a photothermal cavity, 11 is a separation tank, 12 is a diaphragm pump, 13 is a first state monitor, 14 is a constant temperature vaporization furnace, 15 is a high-pressure nitrogen bottle, 16 is an explosion-proof gas flow meter, 17 is a mixing buffer cavity, 18 is a second state monitor, 19 is an insulation box, 20 is a sand-filling tube, 21 is a metering container, and 22 is an array-type prism. DETAILED DESCRIPTION

[0022] In the following, only some exemplary embodiments are briefly described. As those skilled in the art will appreciate, the described embodiments may be modified in various ways without departing from the spirit or scope of the present invention. Therefore, the drawings and descriptions are considered to be exemplary and non-restrictive in nature.

[0023] In the description of the present invention, it should be understood that the terms "center", "longitudinal", "lateral", "length", "width", "thickness", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside", "clockwise", "counterclockwise", "axial", "radial", "circumferential" and the like indicate orientations or positional relationships based on the orientations or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the referred device or element must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be understood as limiting the present invention.

[0024] In addition, the terms "first" and "second" are used for descriptive purposes only and should not be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features. Therefore, the features defined as "first" and "second" may explicitly or implicitly include one or more of the features. In the description of the present invention, the meaning of "plurality" is two or more, unless otherwise clearly and specifically defined.

[0025] In the present invention, unless otherwise clearly specified and limited, the terms "installed", "connected", "connected", "fixed" and the like should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection, an electrical connection, or a communication; it can be a direct connection, or an indirect connection through an intermediate medium, it can be the internal connection of two elements or the interaction relationship between two elements. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0026] In the present invention, unless otherwise clearly specified and limited, a first feature being "above" or "below" a second feature may include that the first and second features are in direct contact, or may include that the first and second features are not in direct contact but are in contact through another feature between them. Moreover, a first feature being "above", "above" and "above" a second feature includes that the first feature is directly above and obliquely above the second feature, or simply indicates that the first feature is higher in level than the second feature. A first feature being "below", "below" and "below" a second feature includes that the first feature is directly above and obliquely above the second feature, or simply indicates that the first feature is lower in level than the second feature.

[0027] It should also be understood that the terms used in the present specification are only for the purpose of describing specific embodiments and are not intended to limit the present invention. As used in the present specification and the appended claims, unless the context clearly indicates otherwise, the singular forms "a", "an" and "the" are intended to include plural forms.

[0028] It should be further understood that the term "and / or" used in the present description and the appended claims refers to any and all possible combinations of one or more of the associated listed items, and includes these combinations.

[0029] Various structural schematic diagrams of the embodiments disclosed in the present invention are shown in the accompanying drawings. These figures are not drawn to scale, and some details are magnified and some details may be omitted for the purpose of clear expression. The shapes of various regions and layers shown in the figures and the relative sizes and positional relationships therebetween are only exemplary, and may deviate in practice due to manufacturing tolerances or technical limitations, and those skilled in the art may additionally design regions / layers with different shapes, sizes, and relative positions according to actual needs.

[0030] The embodiments of the present invention are described in detail below with reference to the accompanying drawings.

[0031] Example 1 like Figure 1 and Figure 2 As shown, the fracturing backflow fluid clean treatment and heavy oil thermal recovery integrated experimental system provided by the present invention includes a backflow fluid static box 1, an axial flow pump 2 is arranged at the downstream end of the backflow fluid static box 1, a differential pressure flowmeter 3 is arranged at the downstream end of the axial flow pump 2, a photocatalyst suspension tank 4 is arranged at the downstream end of the differential pressure flowmeter 3, an intermittent peristaltic pump 5 is arranged downstream of the photocatalyst suspension tank 4, and a photoreactor 9 is arranged downstream of the intermittent peristaltic pump 5. The middle top layer of the photoreactor 9 is provided with a sapphire window 8, and the bottom layer is provided with an array prism 22. A separation tank 11 is arranged at the downstream end of the photoreactor 9, and a solar simulator 6 and a focusing lens 7 are arranged on the top of the photoreactor 9. A diaphragm pump 12 is arranged downstream of the separation tank 11, and the diaphragm pump 12 is directly connected to the photothermal chamber 10, and a first state monitor 13 is arranged at the downstream end of the photothermal chamber 10, a constant temperature vaporization furnace 14 is arranged at the downstream end of the first state monitor 13, and a mixing buffer chamber 17 is arranged at the downstream end of the constant temperature vaporization furnace 14. A high-pressure nitrogen bottle 15 and an explosion-proof gas flow meter 16 are respectively provided at the upstream end of the mixing buffer chamber 17. A second state monitor 18 is provided at the downstream end of the mixing buffer chamber 17, and a sand filling pipe 20 is provided at the downstream end of the second state monitor 18. The sand filling pipe 20 is placed inside the heat preservation box 19, and a measuring container 21 is provided at the tail of the sand filling pipe 20.

[0032] In this embodiment, the fracturing backflow fluid retrieved from the oil field site needs to be left in the backflow fluid standing tank 1 for 1 hour to ensure that solid impurities such as gravel in the backflow fluid are removed. A TiO2 photocatalyst particle water suspension with a concentration of 1 mg / mL is placed in the photocatalyst suspension tank 4, and the axial flow pump 2 extracts the supernatant from the backflow fluid standing tank 1 into the pipeline. The differential pressure flowmeter 3 needs to select different volume ratios of backflow fluid and photocatalyst particle suspension according to the actual degradation performance.

[0033] In this embodiment, the solar photons emitted by the solar simulator 6 are further transmitted to the sapphire window 8 through the focusing effect of the focusing lens 7, and the focusing ratio is above 100. The optical transmittance of the sapphire window 8 is above 98%. The intermittent peristaltic pump 5 can control the flow rate of the backwash liquid and the photocatalyst particle mixed liquid flowing from the photocatalyst suspension tank 4. At the same time, the start-stop time ratio of the intermittent peristaltic pump 5 needs to be controlled according to the actual degradation performance feedback. The height of the array prism 22 in the photoreactor 9 is 5 mm. Its main function is to form a local micro-turbine environment when the mixed liquid flows through the array prism 22 to avoid the aggregation and sedimentation of the photocatalyst particles.

[0034] In this embodiment, the mixed liquid that completes the photoreaction in the photoreactor 9 completes the solid-liquid separation process in the downstream separation tank 11, and the supernatant after degradation treatment completes the vaporization process in the photothermal chamber 10. The diaphragm pump 12 needs to control the flow rate below 20mL / min. A black carbon gel film is placed at the bottom of the photothermal chamber 10 to enhance the photothermal absorption and thermal conversion effects. The first state monitor 13 can monitor the temperature, pressure, water content and other information of the steam in the photothermal chamber 10 in real time.

[0035] In this embodiment, the photoreactor 9 and the photothermal chamber 10 form a complementary relationship in the utilization of the solar energy spectrum, and the absorption spectrum ranges are 250nm-500nm and 500nm-2500nm respectively. The constant temperature vaporization furnace 14 can further adjust the temperature and pressure of the steam according to the experimental parameter requirements. In the sand filling tube 20, the core compressed with quartz sand can be used to simulate the underground rock formation. The core treated with saturated water and saturated oil is placed in the sand filling tube 20. The insulation box 19 can simulate the real-time temperature of the underground environment in situ. The temperature range that can be set is 25 o C-1000 o Between C.

[0036] In this embodiment, in order to improve the injection capacity of water vapor, inert nitrogen is used as a carrier gas to inject it into the sand filling tube 20. The explosion-proof gas flow meter 16 can control the high-pressure nitrogen released from the high-pressure nitrogen bottle 15, and the mixed gas of nitrogen and water vapor enters the rear end together after being evenly mixed in the mixing buffer chamber 17. The second state monitor 18 can detect the gas pressure and temperature at the inlet end of the sand filling tube 20.

[0037] In this embodiment, the volume flow rate of heavy oil thermal recovery can be obtained according to the metering container 21, and the thermal recovery performance under the characteristic parameter conditions can be measured by comparing the produced oil volume with the total saturated oil volume.

[0038] Example 2 like Figure 1 and Figure 2As shown, the present invention provides an integrated experimental method for fracturing flowback fluid clean treatment and heavy oil thermal recovery, comprising: First, before the experimental system is operated, it is necessary to prepare a water suspension of TiO2 photocatalyst particles with a concentration of 1 mg / mL and place it in the photocatalyst suspension tank 4, and stir it continuously. In addition, the fracturing backflow liquid retrieved from the site is poured into the backflow liquid standing box 1 as an experimental sample, and is left to stand for more than 1 hour to ensure that the gravel therein is completely settled. For the experimental core, silica particles between 40 mesh and 100 mesh can be compressed and used as simulated cores, and then saturated with water and saturated with oil are placed in the sand filling tube 20, and the total oil content in the simulated core is recorded. When the system starts running, the fracturing backflow liquid in the backflow liquid standing box 1 is pumped to the photocatalyst suspension tank 4 by the axial flow pump 2, and the volume ratio and corresponding concentration of the two liquids can be adjusted by the differential pressure flowmeter 3. Furthermore, the mixed liquid is transported to the photoreactor 9 through the intermittent peristaltic pump 5 to participate in the photochemical reaction, wherein the arrayed prisms 22 provided therein can form a local micro-turbulence environment when the mixed liquid flows through the arrayed prisms, thereby avoiding the aggregation and sedimentation of the photocatalyst particles. The solar simulator 6 can emit a full-band spectrum, and its own light intensity can also be adjusted by its corresponding controller. The emitted full-band photons are converged by the focusing lens 7 and radiated to the reaction suspension through the sapphire window 8. Under the excitation of ultraviolet light and some visible light photons, the photocatalyst TiO2 will produce abundant holes and correspondingly produce hydroxyl radicals with extremely strong oxidizing properties in the base liquid, which can oxidize and degrade organic matter and bacteria in the backwash liquid into non-toxic and harmless low-carbon molecules or inorganic substances. After the reaction, the reaction liquid enters the separation tank 11 for static separation. After the photocatalyst settles, the diaphragm pump 12 pumps the supernatant of the separation tank 11 into the photothermal chamber 10 for photothermal conversion. The unused spectrum of the photoreactor 9 is used to drive the photothermal conversion, and the low-flow liquid water is converted into water vapor. The first state monitor can be used to monitor the temperature and pressure state of this test section. The constant temperature vaporization furnace 14 can further adjust the temperature and pressure range of the steam according to the test requirements of the experiment. At the same time, the nitrogen stored in the high-pressure nitrogen bottle 15 enters the mixing buffer chamber 17 after the explosion-proof gas flowmeter 16 and mixes with the hot steam to serve the purpose of carrier gas and pressurization. The mixed gas coming out of the mixing buffer chamber 17 is directly injected into the sand filling tube 20, and the insulation box 19 can control the temperature range of the sand filling tube 20. The second state monitor can be used to monitor the temperature and pressure of the mixed gas at the inlet of the sand filling pipe 20. After the steam heating and viscosity reduction treatment, the heavy oil pre-filled in the sand filling pipe 20 will be continuously displaced, and the volume of the displaced heavy oil is measured in the metering container 21, and the performance under different operating parameters is compared.

[0039] The above shows and describes the basic principles and main features of the present invention and the advantages of the present invention. It is obvious to those skilled in the art that the present invention is not limited to the details of the above exemplary embodiments, and the present invention can be implemented in other specific forms without departing from the spirit or basic features of the present invention. Therefore, no matter from which point of view, the embodiments should be regarded as exemplary and non-restrictive. The scope of the present invention is defined by the attached claims rather than the above description, and it is intended that all changes falling within the meaning and scope of the equivalent elements of the claims are included in the present invention. Any figure mark in the claims should not be regarded as limiting the claims involved.

[0040] In addition, it should be understood that although this specification is described in accordance with the implementation modes, not every implementation mode contains only one independent technical solution. This description of the specification is only for the sake of clarity. Those skilled in the art should regard the specification as a whole. The technical solutions in each embodiment can also be appropriately combined to form other implementation modes that can be understood by those skilled in the art. The above content is only to illustrate the technical idea of ​​the present invention, and cannot be used to limit the protection scope of the present invention. Any changes made on the basis of the technical solution according to the technical idea proposed by the present invention shall fall within the protection scope of the claims of the present invention.

Claims

1. Fracturing flowback fluid clean treatment and heavy oil thermal recovery integrated experimental system, characterized in that: The invention comprises a backflow liquid still box (1), an axial flow pump (2) is arranged at the downstream end of the backflow liquid still box (1), a differential pressure flow meter (3) is arranged at the downstream end of the axial flow pump (2), a photocatalyst suspension tank (4) is arranged at the downstream end of the differential pressure flow meter (3), an intermittent peristaltic pump (5) is arranged downstream of the photocatalyst suspension tank (4), and a photoreactor (9) is arranged downstream of the intermittent peristaltic pump (5); a sapphire window (8) is arranged on the middle top layer of the photoreactor (9), and an array prism (22) is arranged on the bottom layer; a separation tank (11) is arranged at the downstream end of the photoreactor (9), and a solar simulator (6) and a focusing lens (7) are arranged on the top of the photoreactor (9); a diaphragm pump (12) is arranged downstream of the separation tank (11). ), a diaphragm pump (12) is directly connected to the photothermal chamber (10), a first state monitor (13) is arranged at the downstream end of the photothermal chamber (10), a constant temperature vaporization furnace (14) is arranged at the downstream end of the first state monitor (13), and a mixing buffer chamber (17) is arranged at the downstream end of the constant temperature vaporization furnace (14); a high-pressure nitrogen bottle (15) and an explosion-proof gas flow meter (16) are arranged at the upstream end of the mixing buffer chamber (17); a second state monitor (18) is arranged at the downstream end of the mixing buffer chamber (17), and a sand filling pipe (20) is arranged at the downstream end of the second state monitor (18), the sand filling pipe (20) is placed inside the heat preservation box (19), and a metering container (21) is arranged at the tail of the sand filling pipe (20).

2. The integrated experimental system for fracturing flowback fluid clean treatment and heavy oil thermal recovery according to claim 1, characterized in that: The fracturing flowback fluid retrieved from the oil field is left to stand in the flowback fluid standing box (1) for 1 hour to ensure that solid impurities in the flowback fluid are removed.

3. The integrated experimental system for fracturing flowback fluid clean treatment and heavy oil thermal recovery according to claim 1, characterized in that: A TiO2 photocatalyst particle water suspension having a concentration of 1 mg / mL is placed in the photocatalyst suspension tank (4); an axial flow pump (2) draws the supernatant from the backwash liquid quiescent tank (1) into the pipeline; a differential pressure flow meter (3) selects and mixes backwash liquid and photocatalyst particle suspension in different volume ratios according to actual degradation performance.

4. The integrated experimental system for fracturing flowback fluid clean treatment and heavy oil thermal recovery according to claim 1, characterized in that: The solar photons emitted by the solar simulator (6) are further transmitted to the sapphire window (8) through the focusing effect of the focusing lens (7), and the focusing ratio is above 100; the intermittent peristaltic pump (5) is used to control the flow rate of the backwash liquid and the photocatalyst particle mixed liquid flowing from the photocatalyst suspension tank (4), and at the same time, the start-stop time ratio of the intermittent peristaltic pump (5) is controlled according to the actual degradation performance feedback; the height of the array prism (22) in the photoreactor (9) is 5 mm, which is used to form a local micro-turbulence environment when the mixed liquid flows through the array prism (22).

5. The integrated experimental system for fracturing flowback fluid clean treatment and heavy oil thermal recovery according to claim 1, characterized in that: The mixed liquid that completes the photoreaction in the photoreactor (9) completes the solid-liquid separation process in the downstream separation tank (11), and the supernatant after degradation is vaporized in the photothermal chamber (10). The diaphragm pump (12) needs to control the flow rate to be below 20 mL / min. A black carbon gel film is placed at the bottom of the photothermal chamber (10) to enhance the photothermal absorption and thermal conversion effects. The first state monitor (13) is used to monitor the temperature, pressure and water content information of the steam in the photothermal chamber (10) in real time.

6. The integrated experimental system for fracturing flowback fluid clean treatment and heavy oil thermal recovery according to claim 1, characterized in that: The photoreactor (9) and the photothermal cavity (10) form a complementary relationship in the utilization of the solar energy spectrum, and absorb the spectrum ranges of 250nm-500nm and 500nm-2500nm respectively.

7. The integrated experimental system for fracturing flowback fluid clean treatment and heavy oil thermal recovery according to claim 1, characterized in that: The constant temperature vaporization furnace (14) is used to further adjust the temperature and pressure of the steam according to the experimental parameter requirements; the core compressed by quartz sand is used in the sand filling tube (20) to simulate the underground rock formation, and the core treated with saturated water and saturated oil is placed in the sand filling tube (20); the heat preservation box (19) is used to simulate the real-time temperature of the underground environment in situ, and the temperature range that can be set is 25 o C-1000 o Between C.

8. The integrated experimental system for fracturing flowback fluid clean treatment and heavy oil thermal recovery according to claim 1, characterized in that: Inert nitrogen is used as a carrier gas and is injected into the sand filling tube (20); an explosion-proof gas flow meter (16) is used to control the high-pressure nitrogen released from the high-pressure nitrogen bottle (15); a mixed gas of nitrogen and water vapor is mixed evenly in the mixing buffer chamber (17) and then enters the rear end together; a second state monitor (18) is used to detect the gas pressure and temperature at the inlet end of the sand filling tube (20).

9. The integrated experimental system for fracturing flowback fluid clean treatment and heavy oil thermal recovery according to claim 1, characterized in that: The volume flow rate of heavy oil thermal recovery is obtained according to the metering container (21), and the thermal recovery performance under the characteristic parameter conditions is measured by comparing the produced oil volume with the total saturated oil volume.

10. An integrated experimental method for fracturing flowback fluid clean treatment and heavy oil thermal recovery, characterized in that: The method is based on the integrated experimental system for clean treatment of fracturing flowback fluid and thermal recovery of heavy oil according to any one of claims 1 to 9, comprising: A 1 mg / mL TiO2 photocatalyst particle water suspension is placed in a photocatalyst suspension tank (4) and stirred continuously; the fracturing backflow fluid retrieved from the site is poured into a backflow fluid standing box (1) as an experimental sample and left to stand for more than (1) hour to ensure that the gravel therein is completely settled; for the experimental core, silica particles between 40 mesh and 100 mesh are compressed as a simulated core, which is then saturated with water and saturated with oil and placed in a sand filling pipe (20), and the total oil content in the simulated core is recorded; when the system starts to operate, the fracturing backflow fluid in the backflow fluid standing box (1) passes through the shaft The liquid is pumped into the photocatalyst suspension tank (4) by a flow pump (2), and the volume ratio and corresponding concentration of the two liquids are adjusted by a differential pressure flow meter (3); the mixed liquid is transported to the photoreactor (9) through an intermittent peristaltic pump (5) to participate in the photochemical reaction, wherein the array prism (22) provided therein forms a local micro-turbulence environment when the mixed liquid flows through the array prism; the solar simulator (6) emits a full-band spectrum, and the emitted full-band photons are concentrated by a focusing lens (7) and radiated to the reaction suspension through a sapphire window (8), and under the excitation of ultraviolet light and part of visible light photons, the photocatalyst TiO2 Holes are generated and hydroxyl radicals are generated in the base liquid accordingly; the reaction liquid after the reaction enters the separation tank (11) for static separation, and after the photocatalyst settles, the diaphragm pump (12) pumps the supernatant of the separation tank (11) into the photothermal chamber (10) for photothermal conversion, and uses the unused spectrum of the photoreactor (9) to drive the photothermal conversion, and converts the low-flow liquid water into water vapor. The first state monitor (13) is used to monitor the temperature and pressure state of this test section; the constant temperature vaporization furnace (14) further adjusts the temperature value and pressure value range of the steam according to the test requirements of the experiment; at the same time, the high-pressure nitrogen gas stored in the high-pressure nitrogen bottle (15) The stored nitrogen passes through an explosion-proof gas flow meter (16) and enters a mixing buffer chamber (17) to mix with hot steam, thereby serving as a carrier gas and boosting the pressure. The mixed gas from the mixing buffer chamber (17) is directly injected into a sand filling pipe (20), and a heat preservation box (19) controls the temperature range of the sand filling pipe (20). A second state monitor (18) monitors the temperature and pressure of the mixed gas at the inlet of the sand filling pipe (20). After being heated and treated to reduce viscosity by steam, the heavy oil pre-filled in the sand filling pipe (20) is continuously displaced, and the volume of the displaced heavy oil is measured in a metering container (21), and the performance under different operating parameters is compared.

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