An experimental test device and method for the dynamic resistivity of the combustion zone in in-situ combustion of heavy oil

Abstract

The present invention provides an experimental test device and method for the dynamic resistivity of a combustion zone in in-situ combustion of heavy oil, belonging to the technical field of heavy oil fire flooding recovery. The device includes a double-layer tube body, an inner tube made of high-temperature resistant insulation material, a high-temperature resistant metal outer tube, with the inner tube fitting against the inner wall of the outer tube. Thermocouples are inserted through holes in the side wall of the double-layer tube body. A constant current source is connected to both ends of the double-layer tube body, and end caps are provided at both ends of the double-layer tube body. An igniter, a compressed gas input pipeline, and an input electrode of the constant current source are provided on the input end cap; a gas-liquid output pipeline and an output electrode of the constant current source are provided on the output end cap. The entire tube body is sealed, and all seals are made of high-temperature resistant insulation materials. The present invention can be used to measure the dynamic resistivity of an oil-bearing core under high-temperature combustion conditions, with a temperature resistance of 700 °C and a pressure resistance of 3 MPa. By using the measured dynamic resistivity, the resistivity change curve of the reservoir combustion zone during the fire flooding process can be plotted, realizing the quantitative analysis of the resistivity change characteristics during the in-situ combustion of reservoir lithology.

Description

Technical Field

[0001] The present invention relates to the technical field of heavy oil fire flooding exploitation, and particularly relates to an experimental test device and method for the dynamic resistivity of a combustion zone in in-situ combustion of oil reservoirs. Background Art

[0002] Fire flooding is a heavy oil thermal recovery technology that continuously injects air and ignites the oil reservoir to burn 10% of the difficult-to-produce heavy components, generating multiple displacement effects such as high-temperature modification, combustion flue gas, and water vapor. It has the characteristics of high thermal efficiency, high recovery rate, energy conservation, and environmental protection. The key to its successful implementation is to achieve high-precision monitoring and identification of the combustion front in the oil reservoir, so as to achieve stable and balanced advancement of the fire front through regulation means, thereby achieving a high crude oil recovery rate. Currently, the fire front monitoring technologies include downhole temperature monitoring, produced gas component analysis, microseismic monitoring, and electromagnetic method monitoring, etc. However, they all have certain limitations and cannot be widely promoted and applied on a large scale.

[0003] The theoretical basis for electromagnetic method monitoring of the fire front is that during the high-temperature fire flooding process of the reservoir, there is a dynamically migrating combustion zone, which can be roughly divided into seven zones such as the burned zone, combustion zone, coking zone, steam condensation zone, oil-rich zone, and original oil zone. Affected by temperature, oil saturation, water saturation, and reservoir mineral changes, the resistivity at different positions and times in the combustion zone will change greatly. The actual core sampling results in the oil field also show that the resistivity of the core in the burned zone (burned area) of fire flooding is 10 to 100 times higher than that in the original oil zone. Based on this physical phenomenon, in the oil field, the change of formation resistivity can be measured by geophysical exploration means such as electromagnetic monitoring, and then the distribution pattern and migration direction of the underground combustion zone can be inversely deduced. The current interpretation model for the resistivity change in the burned zone of fire flooding is established through theoretical derivation. When applied, it has a poor coincidence with the actual formation resistivity change, and there is a certain degree of uncertainty in the interpretation results, which affects the interpretation accuracy. The final result needs to be corrected by combining reservoir physical properties and production dynamic data, which limits the popularization and application of this technology.

[0004] The existing core electrical property test devices and test methods can only test the static resistivity of cores from room temperature to within 200°C under normal pressure. However, in the dynamic displacement process of fire flooding, a high-temperature and high-pressure dynamic combustion environment needs to be simulated. The currently used one-dimensional combustion tube physical simulation experimental device can achieve ignition and continuous injection of high-pressure air, and the temperature at the combustion zone can reach 400°C - 700°C. However, the one-dimensional combustion tube structure is a metal tube body, and there is a large amount of water in the cores filled in it. Although the function of temperature resistance and pressure resistance is achieved, the electrical insulation between the test electrode and the tube body cannot be achieved at high temperatures. Therefore, the resistivity change characteristics of each zone in the fire flooding combustion process cannot be measured.

[0005] At present, there is no experimental device and testing method that can withstand high temperature and high pressure and has good electrical insulation during the dynamic displacement process of in-situ combustion, and can measure the resistivity change characteristics of each combustion zone.

[0006] The existing technology has at least the following deficiencies:

[0007] 1. The interpretation model of the resistivity change in the in-situ combustion zone is established through theoretical derivation. When applied, the degree of coincidence with the actual formation resistivity change is poor, and there is a certain degree of uncertainty in the interpretation result, which affects the interpretation accuracy.

[0008] 2. It is impossible to achieve electrical insulation between the test electrode and the pipe body under high-temperature conditions, so it is impossible to measure the resistivity change characteristics of each zone during the in-situ combustion process. Summary of the Invention

[0009] To solve the problems existing in the prior art, the present invention provides an experimental test device and method for the dynamic resistivity of the in-situ combustion zone of in-situ combustion of oil reservoirs. The device includes a double-layer pipe body, which uses a high-temperature-resistant insulating inner pipe and a high-temperature-resistant metal outer pipe. The inner pipe is attached to the inner wall of the outer pipe. Thermocouples are inserted through holes in the side wall of the double-layer pipe body. A constant current source is connected to both ends of the double-layer pipe body. End caps are provided at both ends of the double-layer pipe body. An igniter, a compressed gas input pipeline, and an input electrode of the constant current source are provided on the input end cap; a gas-liquid output pipeline and an output electrode of the constant current source are provided on the output end cap. The outer pipe is sealed with the end cap through a flange, and sealing members are also provided inside the end cap. All sealing members are made of high-temperature-resistant insulating materials. The present invention can be used to measure the dynamic resistivity of an oil-bearing core under high-temperature combustion conditions, with a temperature resistance of 700 °C and a pressure resistance of 3 MPa. Using the measured dynamic resistivity, the resistivity change curve of the reservoir combustion zone during the in-situ combustion process of oil displacement can be drawn, realizing the quantitative analysis of the resistivity change characteristics during the in-situ combustion process of reservoir lithology.

[0010] The present invention provides an experimental test device for the dynamic resistivity of the in-situ combustion zone of in-situ combustion of oil reservoirs, including a double-layer pipe body; the double-layer pipe body includes: an inner pipe and an outer pipe, and the inner wall of the outer pipe is closely attached to the inner pipe;

[0011] The inner pipe is made of high-temperature-resistant insulating material; the outer pipe is made of high-temperature-resistant metal material;

[0012] End caps are provided at both ends of the double-layer pipe body, which are respectively an input end cap and an output end cap, and the end caps are made of high-temperature-resistant metal material;

[0013] A constant current source is connected to both ends of the double-layer pipe body;

[0014] An igniter, a compressed gas input pipeline, and an input electrode of the constant current source are provided on the input end cap;

[0015] A gas-liquid output pipeline and an output electrode of the constant current source are provided on the output end cap;

[0016] Pressure sensors are provided on the gas-liquid output pipeline and the compressed gas input pipeline;

[0017] On one side of the double-layer pipe body, a plurality of equally spaced holes are axially provided, and thermocouples are inserted into the holes;

[0018] A thermocouple housing is provided outside the thermocouple. The thermocouple housing is connected to a voltmeter, and the thermocouple housing is made of high-temperature resistant metal material.

[0019] Preferably, first seals are provided on the inner sides of the input end cover and the output end cover;

[0020] Second seals are provided outside the input electrode and the output electrode of the constant current source, as well as at the igniter interface part, the compressed gas input pipeline and the gas-liquid output pipeline;

[0021] Both the first seal and the second seal are made of high-temperature resistant insulating sealing materials.

[0022] Preferably, the inner pipe is made of quartz material, the outer pipe is made of stainless steel material, and the end cover is made of stainless steel material.

[0023] Preferably, one end of the thermocouple is inserted into the inside of the double-layer pipe body, and the other end is located outside the double-layer pipe body. The thermocouple housing is made of stainless steel material.

[0024] Preferably, internal threads are provided in the holes opened in the outer pipe. By using a compression nut and a third seal, the sealing and electrical insulation between the thermocouple and the outer pipe and the inner pipe are achieved. The third seal is made of high-temperature resistant insulating sealing material.

[0025] Preferably, flange structures are provided at both ends of the outer pipe. The end cover and the outer pipe are hermetically connected to the outer pipe flange through bolts. The outer pipe adopts two tubular structures with semi-circular cross-sections, and the sides are hermetically connected by flanges.

[0026] Preferably, a plurality of holes are opened in the input end cover, which are respectively an igniter interface, a compressed gas input port and an input port of the constant current source;

[0027] A plurality of holes are opened in the output end cover, which are respectively a gas-liquid discharge port and an output port of the constant current source;

[0028] Internal threads are provided in the holes. By using a compression nut and a fourth seal, the sealing and pressure bearing of the corresponding input and output pipelines and components are achieved. The fourth seal is made of high-temperature resistant insulating sealing material.

[0029] Preferably, it further includes a gas-liquid collection device. The compressed gas input pipeline, the gas-liquid output pipeline, and the gas-liquid collection device are all placed on an insulating rubber pad, and there is no current loop between the compressed gas input pipeline and the gas-liquid output pipeline. Electrical isolation is performed between the igniter, the constant current source, the thermocouple, and the voltmeter, and they are grounded separately.

[0030] The present invention provides an experimental test method for the dynamic resistivity of the combustion zone in in-situ combustion, using the above experimental test device for the dynamic resistivity of the combustion zone in in-situ combustion, including the following steps:

[0031] Configure a corresponding oil-bearing and water-bearing saturation simulation core according to the formation conditions to be simulated, load it into the inner tube of the experimental device, and connect the outer tube and the end caps at both ends thereof;

[0032] Insert the thermocouple into the core and seal it firmly, connect the thermocouple wires to the temperature measuring instrument, group two adjacent thermocouples as a set, and use the thermocouple housing as an electrode to connect to the voltmeter;

[0033] Connect the igniter, the compressed gas input pipeline, the gas-liquid output pipeline, the input electrode of the constant current source, and the output electrode of the constant current source to the igniter interface, the compressed gas input port, the gas-liquid discharge port, the input port of the constant current source, and the output port of the constant current source respectively, check the sealing performance and electrical insulation of each connection part, and start the experimental test after confirmation;

[0034] The constant current source is powered on, record the voltage value between the outer shells of two adjacent thermocouples at this time, and calculate the resistivity of the original oil zone based on this data as the reference value for comparison;

[0035] Pass in hot nitrogen for preheating, after reaching the preheating temperature, power on the igniter for heating, and pass in compressed air;

[0036] According to the temperature monitored by the first thermocouple adjacent to the input end, use the control system to adjust the heating power of the igniter, heat the air above the ignition point of the crude oil, and observe the temperature change of the thermocouples at different measurement points;

[0037] The produced liquid and gas are discharged from the gas-liquid output pipeline;

[0038] From the start of ignition until the end of the experiment, the constant current source is continuously powered on, and the temperature of each thermocouple and the voltage value between the outer shells of the thermocouples are continuously measured;

[0039] Divide different combustion zones according to the temperature data measured by multiple thermocouples during the experiment;

[0040] Calculate the resistivity at different times in different combustion zones according to the following formula;

[0041]

[0042] In the formula,

[0043] ρ is the resistivity, with the unit of Ω·m;

[0044] U is the voltage between the outer shells of two adjacent thermocouples, with the unit of V;

[0045] I is the constant current source current, in A;

[0046] S is the simulated core cross-sectional area, in m 2 ;

[0047] L is the distance between two adjacent thermocouple shells, in meters;

[0048] Based on the calculated resistivity, the resistivity variation curve of different combustion zones in the reservoir during the fire flooding process under the formation conditions was drawn.

[0049] Preferably, different combustion zones are divided according to the measured temperature data: the temperature greater than 400°C is the combustion zone, the temperature between 300°C and 400°C is the coking zone, the temperature between 300°C and the steam saturation temperature under the test conditions is divided into the steam condensation zone, the temperature less than the steam saturation temperature and greater than 100°C is divided into the oil-rich zone, and the temperature less than 100°C is divided into the mixed zone of the oil-rich zone and the original oil zone.

[0050] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0051] (1) The inner tube of the experimental test device for the dynamic resistivity of the combustion zone of the fire oil layer of the present invention is made of quartz material, which is resistant to high temperature insulation, has a temperature resistance of 700°C and a pressure resistance of 3MPa, and can be filled with oil-bearing cores, thus solving the problem that the existing test device cannot take into account high temperature and high pressure and achieve electrical insulation.

[0052] (2) The experimental test device for the dynamic resistivity of the combustion zone of the fire oil layer of the present invention has an inner tube made of quartz material and an outer tube made of stainless steel material. A high-temperature resistant insulating seal is used at the sealing part, and a thermocouple is inserted into the side wall of the double-layer tube body. The dynamic resistivity of the oil-bearing core under high-temperature combustion can be measured, which solves the problem of the existing device using a set of sensors to simultaneously measure temperature and resistivity.

[0053] (3) The present invention provides an experimental test method for the dynamic resistivity of the combustion zone of a fire-burned oil layer. By using the measured dynamic resistivity, a resistivity change curve of the combustion zone of the reservoir during the fire flooding process can be drawn, thereby achieving a quantitative analysis of the resistivity change characteristics of the reservoir lithology during the fire flooding process, and solving the problem that the resistivity interpretation model of the high-temperature zone of fire flooding can only rely on theoretical derivation. BRIEF DESCRIPTION OF THE DRAWINGS

[0054] Figure 1 It is a schematic diagram of an experimental test device for the dynamic resistivity of a combustion zone of a fire oil layer according to an embodiment of the present invention.

[0055] Figure 2 This is a resistivity variation curve of a combustion zone of a reservoir during a fire flooding process according to an embodiment of the present invention.

[0056] In the figure:

[0057] 1. Outer tube, 2. Inner tube, 3. End cap, 4. Simulated core, 5. Thermocouple, 6. Thermocouple housing, 7. Voltmeter, 8. Igniter, 9. Compressed gas input pipeline, 10. Gas-liquid output pipeline, 111. Input electrode of constant current source, 112. Output electrode of constant current source, 12. Constant current source, 13. First seal, 14. Second seal, 15. Third seal, 16. Fourth seal, 17. Compression cap. Detailed implementation manners

[0058] The following will describe in detail the detailed implementation manners of the present invention in conjunction with the accompanying drawings.

[0059] The present invention provides an experimental test device for the dynamic resistivity of the combustion zone in in-situ combustion of oil reservoirs, including a double-layer tube body; the double-layer tube body includes: an inner tube 2 and an outer tube 1, and the inner wall of the outer tube 1 is closely attached to the inner tube 2, playing a pressure-bearing and protective role;

[0060] The inner tube 2 is made of a high-temperature resistant insulating material; the outer tube 1 is made of a high-temperature resistant metal material; during the test, the simulated core 4 is filled into the inner tube 2;

[0061] End caps 3 are provided at both ends of the double-layer tube body, which are respectively an input end cap and an output end cap, and the end cap 3 is made of a high-temperature resistant metal material;

[0062] The constant current source 12 is connected to both ends of the double-layer tube body;

[0063] An igniter 8, a compressed gas input pipeline 9 and an input electrode 111 of the constant current source are provided on the input end cap;

[0064] A gas-liquid output pipeline and an output electrode 112 of the constant current source 10 are provided on the output end cap;

[0065] Pressure sensors are provided on the gas-liquid output pipeline 10 and the compressed gas input pipeline 9;

[0066] A plurality of equally spaced holes are axially opened on one side of the double-layer tube body, and thermocouples 5 are inserted into the holes;

[0067] A thermocouple housing 6 is provided outside the thermocouple 5, and the thermocouple housing 6 is connected to the voltmeter 7. The thermocouple housing 6 is made of a high-temperature resistant metal material. The thermocouple housing 6 is equivalent to an electrode and is connected to the voltmeter 7.

[0068] According to a specific implementation scheme of the present invention, a first seal 13 is provided on the inner sides of the input end cap and the output end cap;

[0069] Second seals 14 are provided on the outer sides of the input electrode 111 and the output electrode 112 of the constant current source, as well as at the interface part of the igniter 8, the compressed gas input pipeline 9 and the gas-liquid output pipeline 10;

[0070] Both the first seal 13 and the second seal 14 are made of high-temperature-resistant insulating sealing materials.

[0071] According to a specific embodiment of the present invention, the inner tube 2 is made of quartz material, the outer tube 1 is made of stainless steel, and the end cap 3 is made of stainless steel.

[0072] According to a specific embodiment of the present invention, one end of the thermocouple 5 is inserted into the interior of the double-layer tube body, and the other end is located outside the double-layer tube body. The thermocouple housing 6 is made of stainless steel.

[0073] According to a specific embodiment of the present invention, the hole opened in the outer tube 1 is provided with an internal thread. By using the compression nut 17 and the third seal 15, the sealing and electrical insulation between the thermocouple 5 and the outer tube 1 and the inner tube 2 are achieved. The third seal 15 is made of high-temperature-resistant insulating sealing material.

[0074] According to a specific embodiment of the present invention, both ends of the outer tube 1 are provided with flange structures. The end cap 3 and the outer tube 1 are flange-sealedly connected through bolts to the outer tube 1. The outer tube 1 adopts two semi-circular cross-sectional tubular structures, and the sides are flange-sealedly connected.

[0075] According to a specific embodiment of the present invention, a plurality of holes are opened in the input end cap, which are respectively the interface of the igniter 8, the compressed gas input port, and the input port of the constant current source 12;

[0076] A plurality of holes are opened in the output end cap, which are respectively the gas-liquid discharge port and the output port of the constant current source 12;

[0077] The holes are provided with internal threads. By using the compression nut 17 and the fourth seal 16, the sealing and pressure-bearing of the corresponding input and output pipelines and components are achieved. The fourth seal 16 is made of high-temperature-resistant insulating sealing material.

[0078] The existing one-dimensional combustion tube has a metal shell, and all the thermocouple and pressure measurement tube seals adopt metal ferrule seals. The whole is in a short-circuited conductive state and cannot provide insulation conditions for the inserted electrodes. In the present invention, the inner tube 1 adopts a quartz tube, and all the seals (including the first seal 13, the second seal 14, the third seal 15, and the fourth seal 16) are made of high-temperature-resistant insulating materials, providing good insulation conditions for measuring the true core resistivity of the inserted electrodes. Compared with the conventional fire flooding experiment process, the present invention adds a dynamic resistivity measurement link.

[0079] According to a specific embodiment of the present invention, it further includes a gas-liquid collection device, a compressed gas input pipeline 9 and a gas-liquid output pipeline 10. The compressed gas input pipeline 9 and the gas-liquid output pipeline 10 are placed on an insulating rubber pad, and there is no current loop between the compressed gas input pipeline 9 and the gas-liquid output pipeline 10. The igniter 8, the constant current source 12, the thermocouple 5, and the voltmeter 7 are electrically isolated and grounded separately.

[0080] To avoid interference caused by pipeline grounding and between the igniter 8, constant current source 12, thermocouple 5 and the current loop for resistivity measurement, it is required that the compressed gas input pipeline 9, gas-liquid output pipeline 10, and the gas-liquid collection device are all placed on rubber pads with good insulation performance, and a closed current loop cannot be formed between the compressed gas input pipeline 9 and the gas-liquid output pipeline 10. At the same time, reliable electrical isolation and separate grounding are required between the igniter 8, constant current source 12, thermocouple 5 and the resistivity measurement circuit.

[0081] According to a specific embodiment of the present invention, the outer diameter of the inner tube 2 is 160 mm, the wall thickness of the inner tube 2 is 5 mm, and the length of the inner tube 2 is 1000 - 1500 mm;

[0082] According to a specific embodiment of the present invention, the aperture of the holes opened on the wall of the inner tube 2 is 5 mm, and the hole pitch is 50 - 100 mm;

[0083] According to a specific embodiment of the present invention, the outer diameter of the outer tube 1 is 166 mm, the wall thickness of the outer tube 1 is 3 mm, and the length of the outer tube 1 is 1000 - 1500 mm;

[0084] According to a specific embodiment of the present invention, the outer tube 1 is provided with corresponding small holes at the positions corresponding to the openings of the inner tube 2, and the aperture of the small holes is 8 mm;

[0085] According to a specific embodiment of the present invention, the first seal 13, second seal 14, third seal 15 and fourth seal 16 are made of insulating materials such as high-temperature resistant ceramic fiber, asbestos or mica;

[0086] According to a specific embodiment of the present invention, 3 holes are opened on the input end cover, the diameter of each hole is 8 mm, and 2 holes are opened on the output end cover, and the diameter of the holes is 8 mm.

[0087] The present invention provides an experimental test method for the dynamic resistivity of the combustion zone in in-situ combustion of oil reservoirs. Using the above experimental test device for the dynamic resistivity of the combustion zone in in-situ combustion of oil reservoirs, it includes the following steps:

[0088] Configure the corresponding oil-bearing and water-bearing saturation simulated core 4 according to the formation conditions to be simulated, load it into the inner tube 2 of the experimental device, and connect the outer tube 1 and the end caps 3 at both ends thereof;

[0089] Insert the thermocouple 5 into the simulated core 4 and seal it firmly, connect the thermocouple wires of the thermocouple 5 to the temperature measuring instrument, group two adjacent thermocouples 5 as a group, and use the thermocouple housing 6 as an electrode to connect to the voltmeter 7;

[0090] Connect the igniter 8, the compressed gas input pipeline 9, the gas-liquid output pipeline 10, the input electrode of the constant current source, and the output electrode of the constant current source to the interface of the igniter 8, the compressed gas input port, the gas-liquid discharge port, the input port of the constant current source, and the output port of the constant current source respectively. Check the tightness and electrical insulation of each connection part. After confirmation, start the experimental test;

[0091] The constant current source 12 is powered on, and the voltage value between the outer shells 6 of two adjacent thermocouples is recorded at this time. The original oil zone resistivity is calculated based on this data and used as a reference value for comparison to distinguish the low-resistance zone of the condensate zone and the oil-rich zone with slightly higher resistivity. Considering that the temperature of the entire experimental device will increase due to heat conduction and convection after preheating ignition, the reference value measured before ignition can be used to correct and distinguish the steam condensation zone with lower resistivity and the original oil zone.

[0092] Pass in hot nitrogen for preheating. After reaching the preheating temperature, the igniter 8 is powered on for heating, and compressed air is passed in;

[0093] According to the temperature monitored by the first thermocouple 5 adjacent to the input end, use the control system to adjust the heating power of the igniter 8 to heat the air above the ignition point of the crude oil, and observe the temperature change of the thermocouple 5 at different measuring points; to avoid the adverse effect of low-temperature oxidation caused by passing in low-temperature air, first preheat with nitrogen, and then pass in hot air. After the hot air above the ignition point contacts the crude oil, high-temperature oxidation will occur, and its combustion state is similar to the ignition of a cigarette butt. After ignition, the heat and flue gas generated by the high temperature are used to sweep the cold area downstream, so that the flue gas and part of the oil and water are discharged from the production end.

[0094] The produced liquid and gas are discharged from the gas-liquid output pipeline 10;

[0095] From the start of ignition until the end of the experiment, the constant current source 12 is continuously powered on, and the temperature of each thermocouple 5 and the voltage value between the outer shells 6 of the thermocouple are continuously measured;

[0096] Based on the temperature data measured by multiple thermocouples 5 during the experiment, different combustion zone belts are divided;

[0097] Calculate the resistivity of different combustion zone belts at different times according to the following formula;

[0098]

[0099] In the formula,

[0100] ρ is the resistivity, with the unit of Ω·m;

[0101] U is the voltage between the outer shells of two adjacent thermocouples, with the unit of V;

[0102] I is the current of the constant current source, with the unit of A;

[0103] S is the cross-sectional area of the simulated core, with the unit of m 2 ;

[0104] L is the distance between the outer shells of two adjacent thermocouples, with the unit of m;

[0105] Based on the calculated resistivity, draw the resistivity change curve of different combustion zones in the reservoir during the in-situ combustion process under this formation condition.

[0106] According to a specific implementation of the present invention, dividing different combustion zones according to the measured temperature data is specifically as follows: the temperature greater than 400 °C is the combustion zone, the temperature between 300 °C and 400 °C is the coking zone, the temperature between 300 °C and the steam saturation temperature under the test conditions is divided into the steam condensation zone, the temperature less than the steam saturation temperature and greater than 100 °C is divided into the rich oil zone, and the temperature less than 100 °C is divided into the mixed zone of the rich oil zone and the original oil zone. The present invention proposes specific interval division values for dividing multiple zones according to different temperatures.

[0107] Example 1

[0108] According to a specific implementation of the present invention, in combination with the accompanying drawings, the experimental test device for the dynamic resistivity of the in-situ combustion zone of the present invention will be described in detail.

[0109] The present invention provides an experimental test device for the dynamic resistivity of the in-situ combustion zone, including a double-layer tube body;

[0110] The double-layer tube body includes: an inner tube 2 and an outer tube 1. The inner wall of the outer tube 1 is closely attached to the inner tube 2, playing a pressure-bearing protection role;

[0111] The inner tube 2 is made of high-temperature resistant insulating material; the outer tube 1 is made of high-temperature resistant metal material; in this embodiment, the inner tube 2 is made of quartz material and the outer tube 1 is made of stainless steel material;

[0112] The outer tube 1 adopts two tubular structures with a semicircular cross-section, and the side is sealed and connected by a flange; both ends of the outer tube 1 are provided with flange structures. The end cover 3 and the outer tube 1 are sealed and connected to the flange of the outer tube 1 by bolts. The outer tube 1 adopts two tubular structures with a semicircular cross-section, and the side is sealed and connected by a flange.

[0113] Both ends of the double-layer tube body are provided with end covers, which are respectively the input end cover and the output end cover. The end cover 3 is made of high-temperature resistant metal material. In this embodiment, the end cover is made of stainless steel material;

[0114] The constant current source 12 is connected to both ends of the double-layer tube body;

[0115] The input end cover is provided with an igniter 8, a compressed gas input pipeline 9 and an input electrode 111 of the constant current source; a plurality of holes are opened on the input end cover, which are respectively the interface of the igniter 8, the compressed gas input port and the input port of the constant current source 12;

[0116] A plurality of holes are provided on the output end cover, which are respectively the gas-liquid discharge port and the output port of the constant current source 12; a gas-liquid output pipeline 10 and an output electrode 112 of the constant current source are provided on the output end cover;

[0117] A first seal 13 is provided on the inner sides of the input end cover and the output end cover;

[0118] On the outer sides of the input electrode 111 and the output electrode 112 of the constant current source, as well as at the interface part of the igniter 8, the compressed gas input pipeline 9 and the gas-liquid output pipeline 10, a second seal 14 is provided;

[0119] Both the first seal 13 and the second seal 14 are made of high-temperature resistant insulating sealing materials;

[0120] Pressure sensors are provided on the gas-liquid output pipeline 10 and the compressed gas input pipeline 9;

[0121] On one side of the double-layer tube body, a plurality of equally spaced holes are axially provided, and a thermocouple 5 is inserted into the holes; one end of the thermocouple 5 is inserted into the interior of the double-layer tube body, and the other end is located outside the double-layer tube body;

[0122] Internal threads are provided in the holes opened in the outer tube 1. By using a compression nut 17 and a third seal 15, the sealing and electrical insulation between the thermocouple 5 and the outer tube 1 and the inner tube 2 are achieved. The third seal 15 is made of high-temperature resistant insulating sealing materials;

[0123] Internal threads are provided in the holes. By using a compression nut 17 and a fourth seal 16, the sealing and pressure bearing of the corresponding input and output pipelines and components are achieved. The fourth seal 16 is made of high-temperature resistant insulating sealing materials;

[0124] It further includes a gas-liquid collection device. The compressed gas input pipeline 9, the gas-liquid output pipeline 10, and the gas-liquid collection device are all placed on an insulating rubber pad, and there is no current loop between the compressed gas input pipeline 9 and the gas-liquid output pipeline 10. The igniter 8, the constant current source 12, the thermocouple 5, and the voltmeter 7 are electrically isolated and grounded separately.

[0125] A thermocouple housing is provided outside the thermocouple 5. The thermocouple housing 6 is made of high-temperature resistant metal material. The thermocouple housing 6 is connected to the voltmeter 7. In this embodiment, the thermocouple housing 6 is made of stainless steel material.

[0126] Embodiment 2

[0127] According to a specific implementation scheme of the present invention, in combination with the accompanying drawings, the experimental test device for the dynamic resistivity of the combustion zone in in-situ combustion of oil layers of the present invention is described in detail.

[0128] The present invention provides an experimental test device for the dynamic resistivity of the combustion zone in in-situ combustion of heavy oil, including a double-layer tube body;

[0129] The double-layer tube body includes an inner tube 2 and an outer tube 1. The inner wall of the outer tube 1 is in close contact with the inner tube 2, playing a pressure-bearing and protective role;

[0130] The inner tube 2 is made of a high-temperature resistant insulating material; the outer tube 1 is made of a high-temperature resistant metal material; in this embodiment, the inner tube 2 is made of quartz material and the outer tube 1 is made of stainless steel material;

[0131] The outer diameter of the inner tube 2 is 160 mm, the wall thickness of the inner tube 2 is 5 mm, and the length of the inner tube 2 is 1000 - 1500 mm;

[0132] The outer diameter of the outer tube 1 is 166 mm, the wall thickness of the outer tube 1 is 3 mm, and the length of the outer tube 1 is 1000 - 1500 mm;

[0133] The outer tube 1 adopts two semi-circular tubular structures in cross-section, and the sides are sealed and connected by flanges; the two ends of the outer tube 1 are provided with flange structures, and the end cap 3 is flange-connected to the outer tube 1 through bolts;

[0134] End caps are arranged at both ends of the double-layer tube body, namely an input end cap and an output end cap. The end cap 3 is made of a high-temperature resistant metal material. In this embodiment, the end cap 3 is made of stainless steel material;

[0135] A constant current source 12 is connected to both ends of the double-layer tube body;

[0136] A first seal 13 is provided inside the input end cap and the output end cap;

[0137] An igniter 8, a compressed gas input pipeline 9 and an input electrode 111 of the constant current source are provided on the input end cap; a plurality of holes are opened on the input end cap, namely an interface for the igniter 8, an input port for the compressed gas and an input port for the constant current source 12;

[0138] A gas-liquid output pipeline 10 and an output electrode 112 of the constant current source are provided on the output end cap;

[0139] Pressure sensors are provided on the gas-liquid output pipeline 10 and the compressed gas input pipeline 9;

[0140] Second seals 14 are provided outside the input electrode 111 and the output electrode 112 of the constant current source, as well as at the interface part of the igniter 8, the compressed gas input pipeline 9 and the gas-liquid output pipeline 10;

[0141] Both the first seal 13 and the second seal 14 are made of high-temperature resistant insulating sealing materials. In this embodiment, they are insulating materials such as high-temperature resistant ceramic fiber, asbestos or mica;

[0142] On one side of the double-layer tube body, a plurality of equally spaced holes are axially opened, and a thermocouple 5 is inserted into the holes; one end of the thermocouple 5 is inserted into the interior of the double-layer tube body, and the other end is located outside the double-layer tube body;

[0143] The holes opened in the outer tube are provided with internal threads. By using the compression nut 17 and the third seal 15, the sealing and electrical insulation of the thermocouple 5 with the outer tube 1 and the inner tube 2 are realized. The third seal 15 is made of a high-temperature resistant insulating sealing material, which is an insulating material such as high-temperature resistant ceramic fiber, asbestos or mica in this embodiment; 3 holes are opened on the input end cover, and the diameter of each hole is 8 mm. 2 holes are opened on the output end cover, and the diameter of the holes is 8 mm;

[0144] On the output end cover, a plurality of holes are opened, which are respectively the gas-liquid discharge port and the output port of the constant current source 12; the aperture of the holes opened on the wall of the inner tube 2 is 5 mm, and the hole pitch is 50 - 100 mm; corresponding small holes with an aperture of 8 mm are opened on the outer tube 1 at the corresponding positions of the holes opened on the inner tube 2;

[0145] The holes are provided with internal threads. By using the compression nut 17 and the fourth seal 16, the sealing and pressure bearing of the corresponding input and output pipelines and components are realized. The fourth seal 16 is made of a high-temperature resistant insulating sealing material;

[0146] A thermocouple housing 6 is provided outside the thermocouple 5. The thermocouple housing 6 is made of a high-temperature resistant metal material. The thermocouple housing 6 is connected to a voltmeter. In this embodiment, the thermocouple housing 6 is made of stainless steel.

[0147] Embodiment 3

[0148] According to a specific implementation scheme of the present invention, by using the experimental test device for the dynamic resistivity of the combustion zone in in-situ combustion of heavy oil of the present invention, the experimental test method for the dynamic resistivity of the combustion zone in in-situ combustion of heavy oil of the present invention is described in detail. It is applied to a certain heavy oil reservoir with an average formation porosity of 25.4%, a permeability of 1000 mD, a viscosity of 800 mPa·S for the degassed crude oil at 50°C, and an oil saturation of 55%.

[0149] The present invention provides an experimental test method for the dynamic resistivity of the combustion zone in in-situ combustion of heavy oil. By using the above-mentioned experimental test device for the dynamic resistivity of the combustion zone in in-situ combustion of heavy oil, the method includes the following steps:

[0150] Configure a corresponding oil-bearing and water-bearing saturation simulation core 4 according to the formation conditions to be simulated, load it into the inner tube 2 of the experimental device, and connect the outer tube 1 and the end caps 3 at both ends thereof;

[0151] Insert the thermocouple 5 into the simulation core 4 and seal and fix it. Connect the thermocouple wires of the thermocouple 5 to the temperature measuring instrument. Group two adjacent thermocouples 5, and use their thermocouple housings 6 as electrodes to connect to the voltmeter 7;

[0152] Connect the igniter 8, the compressed gas input pipeline 9, the gas-liquid output pipeline 10, the input electrode 111 of the constant current source, and the output electrode 112 of the constant current source to the interface of the igniter 8, the compressed gas input port, the gas-liquid discharge port, the input port of the constant current source 12, and the output port of the constant current source 12 respectively. Check the tightness and electrical insulation of each connection part. After confirmation, start the experimental test;

[0153] Power on the constant current source 12, record the voltage value between the outer casings 6 of two adjacent thermocouples at this time, and calculate the resistivity of the original oil area based on this data;

[0154] Introduce hot nitrogen (such as 400 °C) for preheating. After reaching the preheating temperature, power on the igniter 8 for heating and introduce compressed air;

[0155] According to the temperature monitored by the first thermocouple 5 adjacent to the input end, use the control system to adjust the heating power of the igniter 8 to heat the air above the ignition point of the crude oil (such as 500 °C), keep the injection pressure at 1 MPa, maintain the air flow rate at 2.5 L / min, keep the high-temperature combustion state, and observe the temperature changes of the thermocouples 5 at different measuring points;

[0156] The produced liquid and gas are discharged from the gas-liquid output pipeline 10;

[0157] From the start of ignition until the end of the experiment (in this embodiment, when the fire line advances to two-thirds of the length of the combustion tube, introduce nitrogen to extinguish the fire and end the experiment), the constant current source is continuously powered on, and the temperatures of each thermocouple 5 and the voltage values between the outer casings 6 of the thermocouples are continuously measured;

[0158] Divide different combustion zone belts according to the measured temperature data; specifically, divide different combustion zone belts according to the measured temperature data as follows: the temperature greater than 400 °C is the combustion zone, the temperature between 300 °C and 400 °C is the coking zone, the temperature between 300 °C and the steam saturation temperature under the test conditions is divided into the steam condensation zone, the temperature less than the steam saturation temperature and greater than 100 °C is divided into the rich oil zone, and the temperature less than 100 °C is divided into the mixed zone of the rich oil zone and the original oil area;

[0159] Calculate the resistivity of different combustion zone belts at different times according to the following formula;

[0160]

[0161] In the formula,

[0162] ρ is the resistivity, with the unit of Ω·m;

[0163] U is the voltage between the outer casings of two adjacent thermocouples, with the unit of V;

[0164] I is the current of the constant current source, with the unit of A;

[0165] S is the cross-sectional area of the simulated core, with the unit of m 2 ;

[0166] L is the distance between the outer shells of two adjacent thermocouples, with the unit of m;

[0167] Based on the calculated resistivity, plot the resistivity change curve of different combustion zones in the reservoir during the in-situ combustion oil displacement process under this formation condition.

[0168] The above are only the preferred embodiments of the present invention and are not used to limit the present invention. For those skilled in the art, the present invention can have various modifications and changes. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention are included within the protection scope of the present invention.

Claims

1. An experimental test device for the dynamic resistivity of the combustion zone in in-situ combustion of heavy oil, characterized in that, It includes a double-layer tube body; The double-layer tube body includes an inner tube and an outer tube, and the inner wall of the outer tube is closely attached to the inner tube; The inner tube is made of a high-temperature resistant insulating material; the outer tube is made of a high-temperature resistant metal material; End caps are provided at both ends of the double-layer tube body, namely an input end cap and an output end cap respectively, and the end caps are made of a high-temperature resistant metal material; A constant current source is connected to both ends of the double-layer tube body; An igniter, a compressed gas input pipeline and an input electrode of the constant current source are provided on the input end cap; A gas-liquid output pipeline and an output electrode of the constant current source are provided on the output end cap; Pressure sensors are provided on the gas-liquid output pipeline and the compressed gas input pipeline; A plurality of equally spaced holes are axially opened on one side of the double-layer tube body, and thermocouples are inserted into the holes; A thermocouple housing is provided outside the thermocouple, and the thermocouple housing is connected to a voltmeter, and the thermocouple housing is made of a high-temperature resistant metal material; First seals are provided inside the input end cap and the output end cap; Second seals are provided outside the input electrode and the output electrode of the constant current source, as well as at the igniter interface part, the compressed gas input pipeline and the gas-liquid output pipeline; Both the first seal and the second seal are made of a high-temperature resistant insulating sealing material; Internal threads are provided in the holes opened in the outer tube. By using a compression nut and a third seal, the sealing and electrical insulation between the thermocouple and the outer tube and the inner tube are achieved, and the third seal is made of a high-temperature resistant insulating sealing material.

2. The experimental test device for the dynamic resistivity of the combustion zone in in-situ combustion according to claim 1, characterized in that, The inner tube is made of quartz material, the outer tube is made of stainless steel material, and the end caps are made of stainless steel material.

3. The experimental test device for the dynamic resistivity of the combustion zone in in-situ combustion according to claim 2, characterized in that, One end of the thermocouple is inserted into the inside of the double-layer tube body, and the other end is located outside the double-layer tube body, and the thermocouple housing is made of stainless steel material.

4. The experimental test device for the dynamic resistivity of the combustion zone in in-situ combustion according to claim 3, characterized in that, Flange structures are provided at both ends of the outer tube, and the end caps are hermetically connected to the outer tube through bolts and the outer tube flanges. The outer tube adopts two semi-circular cross-section tubular structures, and the sides are hermetically connected by flanges.

5. The experimental test device for the dynamic resistivity of the combustion zone in in-situ combustion according to claim 3, characterized in that, A plurality of holes are opened on the input end cap, namely an igniter interface, a compressed gas input port and an input port of the constant current source; A plurality of holes are opened on the output end cap, namely a gas-liquid discharge port and an output port of the constant current source; Internal threads are provided in the holes. By using a compression nut and a fourth seal, the sealing and pressure bearing of the corresponding input and output pipelines and components are achieved, and the fourth seal is made of a high-temperature resistant sealing and insulating material.

6. The experimental test device for the dynamic resistivity of the combustion zone in in-situ combustion of heavy oil according to claim 1, characterized in that, It further includes a gas-liquid collection device. The compressed gas input pipeline, the gas-liquid output pipeline, and the gas-liquid collection device are all placed on an insulating rubber pad, and there is no current loop between the compressed gas input pipeline and the gas-liquid output pipeline. Electrical isolation is carried out among the igniter, the constant current source, the thermocouple and the voltmeter, and they are grounded separately.

7. An experimental test method for the dynamic resistivity of the combustion zone in in-situ combustion of oil reservoirs, using the experimental test device for the dynamic resistivity of the combustion zone in in-situ combustion of oil reservoirs according to any one of claims 1-6, characterized in that, It includes the following steps: Configure a corresponding oil-bearing and water-bearing saturation simulation core according to the formation conditions to be simulated, load it into the inner tube of the experimental device, and connect the outer tube and the end caps at both ends; Insert the thermocouple into the core and seal it firmly, connect the thermocouple wires to the temperature measuring instrument, group two adjacent thermocouples, and connect the thermocouple housing as an electrode to the voltmeter; Connect the igniter, the compressed gas input pipeline, the gas-liquid output pipeline, the input electrode of the constant current source and the output electrode of the constant current source to the igniter interface, the compressed gas input port, the gas-liquid discharge port, the input port of the constant current source and the output port of the constant current source respectively, check the sealing performance and electrical insulation of each connection part, and start the experimental test after confirmation. The constant current source is powered on, and the voltage value between the shells of two adjacent thermocouples is recorded. The original resistivity of the oil zone is calculated based on this data and used as the reference value for comparison. Hot nitrogen is introduced for preheating. After reaching the preheating temperature, the igniter is powered on for heating, and compressed air is introduced. Based on the temperature monitored by the first thermocouple adjacent to the input end, the heating power of the igniter is adjusted using the control system to heat the air above the ignition point of the crude oil, and the temperature changes of the thermocouples at different measurement points are observed. The produced liquid and gas are discharged from the gas-liquid output pipeline. From the start of ignition until the end of the experiment, the constant current source remains powered on, and the temperatures of each thermocouple and the voltage values between the thermocouple shells are continuously measured. Based on the temperature data measured by multiple thermocouples during the experiment, different combustion zones are divided. The resistivity at different times in different combustion zones is calculated according to the following formula. In the formula, ρ is the resistivity, with the unit of Ω·m; U is the voltage between the shells of two adjacent thermocouples, with the unit of V; I is the current of the constant current source, with the unit of A; S is the cross-sectional area of the simulated core, with the unit of m 2 ; L is the distance between the shells of two adjacent thermocouples, with the unit of m; Based on the calculated resistivity, a resistivity change curve of different combustion zones in the reservoir during the in-situ combustion oil displacement process under this formation condition is plotted.

8. The experimental test method for the dynamic resistivity of the combustion zone in in-situ combustion of heavy oil according to claim 7, characterized in that, The specific division of different combustion zones according to the measured temperature data is as follows: the temperature greater than 400 °C is the combustion zone, the temperature between 300 °C and 400 °C is the coking zone, the temperature between 300 °C and the steam saturation temperature under the test conditions is divided into the steam condensation zone, the temperature less than the steam saturation temperature and greater than 100 °C is divided into the rich oil zone, and the temperature less than 100 °C is divided into the mixed zone of the rich oil zone and the original oil zone.

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