WO2021077660A1

WO2021077660A1 - Supercritical hydrothermal combustion-type downhole steam generator for heavy oil thermal recovery

Info

Publication number: WO2021077660A1
Application number: PCT/CN2020/079100
Authority: WO
Inventors: 王树众; 崔成超; 李艳辉; 蒋卓航; 徐海涛; 任萌萌
Original assignee: 西安交通大学
Priority date: 2019-10-22
Filing date: 2020-03-13
Publication date: 2021-04-29

Abstract

A supercritical hydrothermal combustion-type downhole steam generator for heavy oil thermal recovery, mainly composed of a top end cover (6), a middle end cover (9), a backflow stable combustion zone housing (12), a main reaction zone housing (15) and a blending zone housing (16) which are connected and assembled in sequence; the top end cover is provided with a swirler fuel inlet (1) and a heating rod (5), a heating rod insertion hole runs through the center of the middle end cover, the middle end cover is provided with a main combustion hole jet fuel inlet (2), a main combustion hole jet oxidant inlet (7), a cooling water inlet (8) and a swirl nozzle (10), the swirl nozzle is in communication with the swirler fuel inlet, the backflow stable combustion zone housing has an inner side circumferentially wrapping a combined spiral wall (13), and a bottom end provided with a main combustion nozzle structure (14), the inner wall of the main reaction zone housing is a spiral cooling wall (4), and the main combustion hole jet oxidant inlet, the main combustion hole jet fuel inlet and the cooling water inlet are in communication with the main combustion nozzle structure and the spiral cooling wall by means of inner, middle and outer channels of the combined spiral wall, respectively. The steam generator achieves efficient steam generation directly in the formation, avoiding heat loss during steam delivery.

Description

A supercritical hydrothermal combustion type downhole steam generator for thermal recovery of heavy oil

Technical field

The invention belongs to the technical field of heavy oil exploitation, and in particular relates to a supercritical hydrothermal combustion type downhole steam generator for heavy oil thermal recovery.

Background technique

At present, the oil field mainly uses steam injection boilers to generate steam on the ground, and injects into the downhole combined with steam huff and puff, steam flooding and steam assisted gravity drainage (SAGD) three heavy oil thermal recovery technologies to exploit heavy oil. The above methods mainly have the following bottlenecks, ( 1) Large heat loss. The exhaust smoke loss of the surface steam generator is about 20%, the heat loss of the surface gas pipeline is about 15%, and the heat loss of the injection wellbore is about 10% per kilometer. The overall thermal efficiency is low; (2) the depth of the reservoir is limited. In addition to steam huff and puff, the application depth reaches 1800 meters, and the steam flooding and SAGD technology with higher recovery efficiency are mainly used in oil reservoirs with a depth of less than 1200 meters. (3) The ground steam generator occupies a large area. The inability to be deployed on offshore oil exploration platforms with limited space limits the exploitation of offshore heavy oil.

Supercritical hydrothermal combustion refers to a new type of combustion method in which fuel or a certain concentration of organic waste and oxidant undergo a violent oxidation reaction in a supercritical water (T≥374.15℃ and p≥22.12MPa) environment. The flame is supercritical. Water heat flame. The supercritical hydrothermal flame is usually above 800℃, and the local high temperature in the hydrothermal flame area will significantly accelerate the degradation of organic matter (most organic matter can be degraded within 100 milliseconds), release a lot of heat, and can even be used as a means of energy harvesting. This combustion method has a number of significant advantages, (1) it has a millisecond-level reaction rate. (2) The reactor has high heat exchange efficiency and compact structure, and is especially suitable as a source of downhole steam. (3) The reaction products are only CO ₂ and water vapor, no pollution, and CO ₂ can be active to reduce viscosity, further improve the development effect, and realize 100% utilization of the product. Multi-element thermal fluid oil recovery technology refers to the injection of fuel and oxidant into the downhole multi-element thermal fluid generator, burning in a high-pressure closed environment to vaporize water, _{and using the synergistic effect of gas (N 2} and CO ₂ ) and steam to reduce viscosity through gas dissolution , Gas pressurization, heating viscosity reduction, and gas-assisted crude oil gravity drive mechanism to extract crude oil. Compared with traditional surface boiler gas injection, this technology has the advantages of low pollution, high thermal efficiency, and high recovery efficiency.

The supercritical hydrothermal combustion downhole steam generation technology formed by combining the multi-thermal fluid oil recovery technology and the supercritical hydrothermal combustion technology can achieve higher recovery efficiency and safety of heavy oil without being limited by the depth of the well, liberating a large number of oil layers, It perfectly solves the development of medium and deep heavy oil, and overcomes the problems of high energy consumption and high pollution caused by the traditional boiler steam generation method. The successful application of supercritical hydrothermal combustion downhole steam generation technology is inseparable from the R&D and design of the supercritical hydrothermal combustion downhole steam generator, mainly because the space in the oil well is limited, and the reactor needs to achieve stable combustion under a certain volume. High-grade temperature and pressure control ensure safe and stable operation.

Summary of the invention

In order to overcome the above shortcomings of the prior art, the purpose of the present invention is to provide a supercritical hydrothermal combustion downhole steam generator for heavy oil thermal recovery, which aims to solve the problem of gas injection boiler in the process of steam injection for heavy oil thermal recovery. The problem of high energy consumption and large pollution is that by combining the multi-element thermal fluid extraction technology and the supercritical hydrothermal combustion technology, it is possible to directly generate steam directly in the formation and avoid the heat loss during the steam transportation process, which is a deep well , Ultra-deep wells and offshore heavy oil production provide a practical means of oil production. The invention specifically refers to a downhole steam generator, which provides a reaction environment for high-pressure fuel and oxidant delivered from the ground, and allows cooling water to enter at the same time, so as to realize the cooling function and generate high-temperature water vapor at the same time.

In order to achieve the above objective, the technical solution adopted by the present invention is:

A supercritical hydrothermal combustion type downhole steam generator for thermal recovery of heavy oil, which is mainly composed of a top end cover, a middle end cover, a reflux stabilizing zone shell, a main reaction zone shell, and a mixing zone shell connected in sequence. Among them, the top end cover is provided with a swirler fuel inlet and an axial heating rod, the heating rod insertion hole penetrates the center of the middle end cover, and the middle end cover is provided with a main combustion hole jet fuel inlet, a main combustion hole jet oxidant inlet, Cooling water inlet and swirl nozzle. The swirl nozzle is connected with the swirler fuel inlet. The inner side of the reflux stabilization zone shell is circumferentially wrapped with the composite spiral wall. The bottom end is provided with a main combustion nozzle structure. The inner wall of the main reaction zone shell is a spiral cooling wall. , The bottom end is provided with an outlet hole, the bottom end of the mixing zone shell is provided with a mixing zone shell outlet, the composite spiral wall has three spiral channels, inner, middle and outer spiral channels, and the main combustion hole jet oxidant inlet passes through the inner spiral channel, The fuel inlet of the main combustion hole jet passes through the middle spiral channel to connect to the main combustion nozzle structure, and the cooling water inlet is connected to the spiral cooling wall through the outer spiral channel. Finally, a backflow stable combustion zone is formed between the swirl nozzle and the main combustion nozzle structure. A main reaction zone is formed between the main combustion nozzle structure and the outlet orifice, and a mixing zone is formed between the outlet orifice and the outer shell of the mixing zone.

The further improvement of the present invention lies in that an annular combustion stabilizing wall made of refractory material is arranged around the swirl nozzle at the top of the reflux stabilization zone, and the annular combustion stabilizing wall is horn-shaped from top to bottom.

The present invention is further improved in that the spiral cooling wall wraps the main reaction zone, and the bottom of the main reaction zone shell shrinks and closes and is provided with a plurality of outlet holes with a certain angle, which are used as the ejection channel of the fluid after the high temperature reaction.

A further improvement of the present invention is that the cooling water inlet communicates with the gap between the mixing zone shell and the spiral cooling wall, and the cooling water is sprayed in a spiral shape through the spiral cooling wall outlet 19, and then mixed with the high-temperature reaction fluid to generate steam.

A further improvement of the present invention is that a variety of throttling and pressure control structures are provided inside the device: the primary fuel entering through the swirler fuel inlet is mixed with the primary oxidizer and then enters the reflux stable combustion zone through the annular combustion stabilizing wall of the sudden expansion structure ; The bottom of the spiral cooling stave is closed with a number of outlet holes at a certain angle; the bottom of the shell of the mixing zone is a closed structure.

The present invention is further improved in that the main combustion nozzle structure is located between the upper composite spiral wall and the lower spiral cooling wall, and two rows of ring holes are opened on it. The upper row of ring holes is the oxidant main combustion hole, and the lower row of ring holes It is the main fuel hole; the upper row of ring holes is connected with the spiral channel in the composite spiral wall, and the lower row of ring holes is connected with the spiral channel in the composite spiral wall. The center lines of the two rows of ring holes meet at one point, and the intersection is located in the main reaction Area.

Compared with the prior art, the beneficial effects of the present invention are:

1. Integrated combustion-pressure control: There are various throttling and pressure control structures inside the equipment, which not only ensure that the supercritical pressure is maintained above the supercritical pressure for hydrothermal combustion, but also a number of adjustments have been made inside the reactor: the bottom of the spiral cooling wall is closed. Sealed, with only a number of small holes, to ensure that the high-temperature product is mixed with the cooling water; the shell of the mixing zone is also closed.

2. High safety: The composite cooling wall separates the fuel, oxidant and cooling water, and at the same time absorbs the heat released by combustion for preheating, which not only saves energy, but also achieves the purpose of protecting the reactor and preventing the reactor from being burnt at high temperature. It even exploded, overcoming the safety problems encountered in the application of conventional multi-element thermal fluid generators.

3. Good flame stability: the fuel flow and the oxidant flow in the reactor are divided into two stages respectively. The swirler fuel is used for ignition and stable combustion, and the main combustion hole jet fuel is used to release energy to evaporate the cooling water; the middle end cover is close to the swirler Refractory material is fixed at the flow nozzle for absorbing heat and stable combustion during the combustion process; a high-power heating rod is installed on the top of the reactor to keep it on during the working process of the reactor to achieve a certain degree of preheating of the material; the nozzle structure can be replaced For other types of nozzles, to ensure that the fuel and the oxidizer are fully mixed and reacted.

4. High thermal efficiency: After the downhole steam generator is fixed at the bottom of the well, after the fuel and oxidant undergo a hydrothermal combustion reaction, the large amount of heat released can directly evaporate the cooling water to achieve high-efficiency steam generation directly in the formation and avoid steam transportation The heat loss in the process provides a practical oil extraction device for deep wells, ultra-deep wells and offshore heavy oil production.

Description of the drawings

Figure 1 is a schematic diagram of the present invention.

Among them: A1-backflow stabilization zone, A2-main reaction zone, 1-cyclone fuel inlet, 2-main combustion hole jet fuel inlet, 3-fixed bolt, 4-helical cooling stave, 5-heating rod, 6- Top end cover, 7-main combustion hole jet oxidant inlet, 8-cooling water inlet, 9-middle end cover, 10-swirl nozzle, 11-annular combustion stabilization wall, 12-return combustion stabilization zone shell, 13-composite spiral Wall, 14-main combustion nozzle structure, 15-main reaction zone shell, 16-mixing zone shell, 17-spiral cooling wall outlet hole, 18-mixing zone shell outlet.

Figure 2 is a partial (upper part) enlarged view of the supercritical hydrothermal flame generator.

Figure 3 is a partial (lower) enlarged view of the supercritical hydrothermal flame generator.

Detailed ways

The following describes the implementation of the present invention in detail with reference to the drawings and examples.

As shown in Figure 1, Figure 2 and Figure 3, a supercritical hydrothermal combustion type downhole steam generator for thermal recovery of heavy oil of the present invention is mainly composed of a top end cover 6, a middle end cover 9, and a backflow stabilization zone. The shell 12, the main reaction zone shell 15 and the mixing zone shell 16 are connected and assembled in sequence by fixing bolts 3.

Among them, the top end cover 6 is provided with a swirler fuel inlet 1 and an axial heating rod 5, the insertion hole of the heating rod 5 penetrates the center of the middle end cover 9, and the middle end cover 9 is provided with a main combustion hole jet fuel inlet 2 The main combustion hole jet oxidant inlet 7, the cooling water inlet 8 and the swirl nozzle 10. The swirl nozzle 10 is in communication with the swirler fuel inlet 1, and a ring-shaped stabilizing wall made of refractory material can be arranged around the swirl nozzle 10 11. The annular combustion stabilizing wall 11 is horn-shaped as a whole from top to bottom. The swirl nozzle 10 can adopt a spiral nozzle, and the fuel part and the oxidant part in the structure can be replaced to achieve coordination.

The inner side of the reflux stabilization zone casing 12 is circumferentially wrapped with a composite spiral wall 13, and the bottom end is provided with a main combustion nozzle structure 14. The composite spiral wall 13 adopts a three-layer composite structure and has three spiral passages: inner, middle, and outer. The main combustion nozzle structure 14 is located between the upper composite spiral wall 13 and the lower spiral cooling wall 4, and there are two rows of ring holes on it. The upper row of ring holes is the main fuel hole for oxidant, and the lower row of ring holes is the main fuel hole for fuel. The upper row of ring holes is connected with the spiral channel in the composite spiral wall 13, the lower row of ring holes is connected with the spiral channel in the composite spiral wall 13, and the center lines of the two rows of ring holes meet at one point.

The inner wall of the main reaction zone shell 15 wraps the spiral cooling wall 4 and is fixed in the form of a slot. The bottom is shrunk and closed and is provided with a number of outlet holes 17 with a certain angle, which are used as ejection channels for the fluid after the high temperature reaction. The bottom end of the mixing zone shell 16 is provided with a mixing zone shell outlet 18.

The main combustion hole jet oxidant inlet 7 passes through the inner spiral channel of the composite spiral wall 13, the main combustion hole jet fuel inlet 2 passes through the middle spiral channel of the composite spiral wall 13, and is connected to the main combustion nozzle structure 14, and the cooling water inlet 8 passes through the composite spiral wall. The outer spiral channel of 13 is connected to the gap between the mixing zone shell 16 and the spiral cooling wall 4, and the cooling water is sprayed in a spiral shape through the spiral cooling wall outlet 19, and then mixed with the high-temperature reaction fluid to generate steam.

Finally, a backflow stabilization zone A1 is formed between the swirl nozzle 10 and the main combustion nozzle structure 14, a main reaction zone A2 is formed between the main combustion nozzle structure 14 and the outlet orifice 17, and the outlet orifice 17 and the mixing zone are formed A blending zone A3 is formed between the shell outlets 18. The reflux stabilization zone A1, the main reaction zone A2 and the blending zone A3 are the three main functional areas inside the steam generator, and the annular stabilization wall 11 is located at the top of the reflux stabilization zone A1 , The main reaction zone A2 is wrapped by the spiral cooling wall 4, and the intersection of the center lines of the two rows of annular holes of the main combustion nozzle structure 14 is located in the main reaction zone A2.

The steam generator of the present invention involves a variety of throttling and pressure control structures: the primary fuel entering through the swirler fuel inlet 1 is mixed with the primary oxidant and then enters the reflux stable combustion zone A1 through the annular combustion stabilizing wall 11 of the sudden expansion structure The bottom of the spiral cooling wall 4 is closed and opened with a plurality of outlet holes 17 at a certain angle; the bottom of the shell 16 of the mixing zone is a closed structure.

According to the above structure, the starting method of the present invention: firstly start the high-power heating rod to pre-heat the primary fuel entering from the swirler fuel inlet 1 and control the flow rate as low as possible at this time. The primary fuel atomized and sprayed through the swirl nozzle 10 and the spirally sprayed primary oxidant are mixed and reacted near the annular combustion stabilizing wall 11 to achieve ignition. The higher-flow secondary fuel and secondary oxidant flow through the composite spiral wall 13 via the main combustion hole jet fuel inlet 2 and the main combustion hole jet oxidant inlet 7 respectively. After being ejected from the main combustion nozzle structure 14, they will converge to react. After burning, a lot of heat is released. The cooling water enters the generator through the cooling water inlet 8, and realizes the temperature control of the main reaction zone A2 through the spiral cooling wall 4, and finally flows out from the gap between the mixing zone shell 16 and the spiral cooling wall 4, and mixes with the high-temperature reactants Therefore, a large amount of high-temperature steam is generated, and the obtained high-temperature steam is finally ejected from the outlet 18 of the mixing zone shell.

In summary, the present invention combines the multi-element thermal fluid oil recovery technology with the supercritical hydrothermal combustion technology to achieve high-efficiency steam generation directly in the formation, avoiding heat loss during the steam transportation process, and is suitable for deep wells, ultra-deep wells, and thick offshore wells. Oil production provides high-efficiency and energy-saving heavy oil thermal recovery equipment, which solves the problems of high energy consumption and large pollution in the process of downhole heavy oil thermal recovery of traditional steam injection boilers, and provides high-pressure fuel and oxidant from the ground. The reaction environment, while allowing cooling water to enter, realizes the cooling function and generates high-temperature water vapor downhole at the same time, so as to achieve the purpose of high-efficiency thermal recovery of heavy oil.

Claims

A supercritical hydrothermal combustion type downhole steam generator for thermal recovery of heavy oil, which is characterized in that it is mainly composed of a top end cover (6), a middle end cover (9), a reflux stabilization zone shell (12), and a main The reaction zone shell (15) and the mixing zone shell (16) are connected and assembled in sequence, wherein the top end cover (6) is provided with a cyclone fuel inlet (1) and an axial heating rod (5). The heating rod (5) The insertion hole penetrates the center of the middle end cover (9). The middle end cover (9) is provided with a main combustion hole jet fuel inlet (2), a main combustion hole jet oxidant inlet (7), a cooling water inlet (8) and Swirl nozzle (10), the swirl nozzle (10) is connected with the swirler fuel inlet (1), and the inner side of the reflux stabilization zone casing (12) is circumferentially wrapped with the composite spiral wall (13), and the main combustion nozzle is provided at the bottom end Structure (14), the inner wall of the main reaction zone shell (15) is a spiral cooling wall (4), the bottom end is provided with an outlet hole (17), and the bottom end of the mixing zone shell (16) is provided with a mixing zone shell outlet (18) ), the composite spiral wall (13) has three spiral passages: inner, middle and outer. The main combustion hole jet oxidant inlet (7) passes through the inner spiral passage, and the main combustion hole jet fuel inlet (2) passes through the middle spiral passage to connect Through the main combustion nozzle structure (14), the cooling water inlet (8) is connected to the spiral cooling wall (4) through the outer spiral channel, and finally a backflow stable combustion is formed between the swirl nozzle (10) and the main combustion nozzle structure (14) Zone (A1), the main reaction zone (A2) is formed between the main combustion nozzle structure (14) and the outlet hole (17), and the mixing zone (A2) is formed between the outlet hole (17) and the mixing zone shell outlet (18) Mixed zone (A3).
The supercritical hydrothermal combustion downhole steam generator for heavy oil thermal recovery according to claim 1, characterized in that the swirl nozzle (10) at the top of the reflux stabilization zone (A1) is arranged around refractory materials The annular combustion stabilizing wall (11) is in the shape of a horn from top to bottom.
The supercritical hydrothermal combustion downhole steam generator for heavy oil thermal recovery according to claim 1, wherein the spiral cooling wall (4) wraps the main reaction zone (A2), and the main reaction zone shell (15) The bottom of the) is shrunk and closed and is provided with many small outlet holes (17) with a certain angle, which are used as the ejection channel of the fluid after the high temperature reaction.
The supercritical hydrothermal combustion downhole steam generator for heavy oil thermal recovery according to claim 3, wherein the cooling water inlet (8) communicates with the mixing zone shell (16) and the spiral cooling wall (4). ), the cooling water is sprayed in a spiral shape through the spiral cooling wall outlet (19), and then mixed with the high-temperature reaction fluid to produce steam.
The supercritical hydrothermal combustion downhole steam generator for thermal recovery of heavy oil according to claim 1, characterized in that there are multiple throttling and pressure control structures inside the device: the fuel inlet via cyclone (1) The incoming primary fuel is mixed with the primary oxidant and then enters the reflux stabilization zone (A1) through the annular combustion stabilization wall (11) of the sudden expansion structure; the bottom of the spiral cooling stave (4) is closed and opened with a number of angled The outlet hole (17); the bottom of the shell (16) of the mixing zone is a closed structure.
The supercritical hydrothermal combustion type downhole steam generator for thermal recovery of heavy oil according to claim 1, wherein the main combustion nozzle structure (14) is located in the upper composite spiral wall (13) and the lower spiral wall (13). Between the cooling stave (4), there are two rows of ring holes, the upper row of ring holes is the main oxidizer burning hole, the lower row of ring holes is the fuel main burning hole; the upper row of ring holes and the composite spiral wall (13) inner spiral The channel is connected, the lower row of ring holes is connected to the spiral channel in the composite spiral wall (13), the center lines of the two rows of ring holes intersect at one point, and the intersection is located in the main reaction zone (A2).