CN111794726A - Device and method for accurately representing change of pore structure of rock of steam huff and puff reservoir based on CT (computed tomography) in-situ experiment - Google Patents
Device and method for accurately representing change of pore structure of rock of steam huff and puff reservoir based on CT (computed tomography) in-situ experiment Download PDFInfo
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- IJGRMHOSHXDMSA-UHFFFAOYSA-N Atomic nitrogen Chemical compound N#N IJGRMHOSHXDMSA-UHFFFAOYSA-N 0.000 claims description 6
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- E21B43/00—Methods or apparatus for obtaining oil, gas, water, soluble or meltable materials or a slurry of minerals from wells
- E21B43/16—Enhanced recovery methods for obtaining hydrocarbons
- E21B43/24—Enhanced recovery methods for obtaining hydrocarbons using heat, e.g. steam injection
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Abstract
The invention relates to a device and a method for accurately representing the change of a rock pore structure of a steam huff and puff reservoir based on a CT (computed tomography) in-situ experiment, belonging to the field of research on the seepage law of a thermal recovery reservoir, and comprising a constant-speed constant-pressure pump, a steam generator, a CT special core holder, a hand-operated pump a, a hand-operated pump b, a reservoir sand filling model, a condenser, a collector and an X-ray CT scanning device; the X-ray CT scanning device is used for carrying out CT scanning on a rock core in the rock core holder, and the six-way valve a, the pressure gauge a, the special rock core holder for CT, the six-way valve b, the pressure gauge b and the reservoir sand filling model are all arranged in the constant temperature box. The invention adopts CT scanning nondestructive in-situ experiment and digital core technology to establish a core dimension steam huff and puff physical simulation experiment method based on CT scanning, accurately represents the change of the pore structure of the core before and after steam huff and puff, and enables the micro description of the reservoir structure at a certain stage in the steam huff and puff process to be possible.
Description
Technical Field
The invention relates to a device and a method for accurately characterizing the pore structure change of a steam huff and puff reservoir rock based on a CT (computed tomography) in-situ experiment, in particular to a nondestructive testing process and an accurate characterization method for the pore structure change characteristics of the reservoir rock in the steam huff and puff process of a heavy oil reservoir based on the CT in-situ experiment, and belongs to the technical field of research on the seepage rule of a thermal recovery reservoir.
Background
With the acceleration of the exploration and development of low-grade oil and gas resources in China and the vigorous development of the marine oil and gas industry, the efficient development of heavy oil fields on land and at sea occupies a very important position. The thick oil has large viscosity and poor fluidity, and compared with foreign countries, the thick oil in China is buried deeply and stored in a loose sandstone layer, and sand is easy to generate in the development process, so the comprehensive development cost is high. The heavy oil reservoir development mainly uses different thermal recovery modes such as steam huff and puff, steam flooding, hot water flooding and the like to enlarge the development scale and improve the economic benefit. In the steam huff and puff process, reservoir particles are moved to block reservoir pores due to loose rock cementation, heavy oil carrying, steam scouring and the like. The high temperature can change the particle cementation condition and mineral components, directly cause the change of the porosity and permeability of a reservoir, and irreversibly change the pore structure characteristics of the reservoir of the heavy oil reservoir and the rock mineral composition. This has important effects on fluid flow laws, crude oil (heavy oil) production levels, etc., and directly affects the accuracy of numerical simulation results and the formulation of reservoir development schemes. Therefore, the method has important significance in researching the change of the pore structure of the reservoir rock in the heavy oil thermal recovery process.
The conventional steam huff-and-puff experiment is mainly used for researching macroscopic extraction degree and temperature field change, and cannot be used for micro-description of a reservoir structure at a certain stage in different thermal extraction processes, if a model is taken out in the middle of the test, the pore structure and the fluid occurrence state of loose rock can be damaged, and the experiment must be terminated, so that the conventional method cannot be used for the nondestructive analysis of continuous change of the pore structure characteristics in the steam huff-and-puff process of the loose sandstone heavy oil reservoir, and therefore, the nondestructive in-situ test method is particularly important.
Disclosure of Invention
Aiming at the characteristics and the defects of the existing hot water drive/steam drive physical simulation experiment technology, the invention provides a device and a method for accurately representing the change of the pore structure of a steam huff-puff reservoir rock based on a CT (computed tomography) in-situ experiment, adopts the CT scanning nondestructive in-situ experiment and the digital core technology, establishes a core scale steam huff-puff physical simulation experiment method based on the CT scanning, and accurately represents the change of a microscopic reservoir structure and the characteristics of the seepage rule in the steam huff-puff process, in order to explore the change of the reservoir rock pore structure and the influence of the change on the seepage rule in the steam huff-puff process of a heavy oil reservoir and provide theoretical and technical support for a steam huff-puff injection and production scheme in the development process of the.
The invention adopts the following technical scheme:
a device for accurately representing the change of a pore structure of a rock of a steam huff and puff reservoir based on a CT (computed tomography) in-situ experiment comprises a constant-speed constant-pressure pump, a steam generator, a special core holder for CT, a hand pump a, a hand pump b, a reservoir sand filling model, a condenser, a collector and an X-ray CT scanning device;
the ring pressure interface of the special core holder for CT is communicated with a hand-operated pump a through a pipeline, the A end of the special core holder for CT is respectively connected with a six-way valve a and a condenser through pipelines, a constant-temperature constant-pressure pump is connected with the six-way valve a through a steam generator, the condenser is connected with a collector, the six-way valve a controls the inflow of fluid, and the condenser is used for cooling the fluid flowing out of the outlet of the A end of the core holder after the steam handling is finished;
the B end of the core holder special for CT is connected with the upper inlet end of the reservoir sand filling model through a pipeline, and the lower annular pressure interface of the reservoir sand filling model is communicated with the hand pump B through a pipeline;
the six-way valve a is connected with a pressure gauge a, a switch a is arranged on a pipeline between the six-way valve a and the end A of the special core holder for CT, and a switch b is arranged on a pipeline between the end A of the special core holder for CT and the condenser; a six-way valve b is arranged on a pipeline between a ring pressure interface of the core holder special for CT and the hand pump a, and the six-way valve b is connected with a pressure gauge b; a switch c is arranged on a pipeline between the end B of the special core holder for CT and the inlet end at the upper part of the reservoir sand filling model, a six-way valve c is arranged on a pipeline between the lower annular pressure interface of the reservoir sand filling model and the hand pump B, and the six-way valve c is connected with a pressure gauge c;
the X-ray CT scanning device is used for carrying out CT scanning on the rock core in the rock core holder to obtain rock core images before and after steam huff and puff of the rock core, and a pore phase and a solid phase can be extracted to analyze the influence of the steam huff and puff on the pore structure of the rock core by combining a digital rock core technology;
the six-way valve a, the pressure gauge a, the CT special core holder, the six-way valve b, the pressure gauge b and the reservoir sand filling model are all arranged in the constant temperature box.
In the invention, the A end of the core holder special for CT is a double interface and is respectively connected with two pipelines, one pipeline is connected with a six-way valve a, the other pipeline is connected with a condenser, a switch a is opened and a switch b is closed in the injection process, the switch a is closed and the switch b is opened during the exploitation after the well is closed;
the condenser is used for cooling the produced liquid at the outlet end so that the produced liquid can better flow into the collector.
The collector is used for collecting the produced liquid which is huff and puff by steam, can accurately measure the produced liquid amount and provides parameters for the calculation of the subsequent recovery ratio.
Preferably, the reservoir sand filling model is used for simulating a real reservoir of a steam huff and puff heavy oil reservoir, the reservoir sand filling model is a container with a piston in the middle, an oil-containing sand body is filled at the upper part of the piston, the mineral composition, the oil saturation and the permeability of the oil-containing sand body are all consistent with those of a core in a core holder, the lower part of the piston is filled with water, and a lower annular pressure interface is connected with a hand pump b and used for applying confining pressure to the reservoir sand filling model;
in the reservoir sand filling model, a wet filling method is adopted as the sand filling method, and the reservoir sand filling model with larger volume is connected with the core sand filling model because the core size is too small and the steam throughput cannot be effectively simulated, so that the steam throughput state in the real reservoir can be simulated. Because the piston capable of sliding and sealing is arranged in the sand filling model, the piston can slightly move along with the pressure change in the steam injection process, and the oil-containing sand body can expand along with the injection, so that the characteristics of reservoir pressure and volume change in an action range in the steam injection process are better met.
The hand pump b is used for pressurizing the reservoir sand filling model, and water is injected into the bottom of the reservoir sand filling model by the hand pump b according to the hydraulic principle so as to control the pressure of the sand filling model to be the simulated reservoir pressure.
Preferably, the constant-speed constant-pressure pump is used for supplying injected water to the steam generator and controlling the displacement speed, the injection speed range can be 0.001-60 mL/min, and the pressure range is 0.001-60 MPa.
Preferably, the steam generator is used for heating water injected by the constant-speed constant-pressure pump until steam at a required temperature is obtained, and discharging the steam, wherein the steam temperature is 300 ℃ at most.
Preferably, the core holder special for CT is a polyetheretherketone (PEEK material) core holder specially suitable for an X-ray CT scanner, the PEEK cutting performance is excellent, the high temperature resistance is realized, the mechanical performance is good, the ray transmission performance is realized, and the core can be installed in the core holder and scanned by X-ray CT, so that the micro-pore structure characteristics of the core can be obtained. The core holder is used for fixing the core and directly carrying out X-ray CT scanning on the core before and after the steam huff and puff process of the core.
Further preferably, the ranges of the pressure gauge a, the pressure gauge b and the pressure gauge c are all 50MPa, and the precision is all 0.20 MPa.
Further preferably, the X-ray CT scanning device is Zeiss MCT-400CT, and is connected with a computer to display a scanned image of the rock core.
Further preferably, the collector is an oil-water separator.
An experimental method of the device for accurately characterizing the pore structure change of the rock of the steam huff and puff reservoir based on the CT in-situ experiment comprises the following steps:
(1) selecting liquid nitrogen to freeze and drill a prepared core, loading the core into a core holder special for CT without any treatment under the condition of keeping an initial pore structure unchanged, and filling oil-containing sand into a reservoir sand filling model by adopting a wet filling method;
(2) the hand-operated pump a and the hand-operated pump b respectively carry out confining pressure on the CT special core holder and the reservoir sand filling model, and the confining pressure reading is read through a pressure gauge b and a pressure gauge c;
the initial confining pressure is generally in the range of 1.5-2MPa, and the confining pressure needs to be continuously adjusted in the experimental process so as to keep the time higher than the upstream inlet pressure by 1.5-2 MPa;
(3) fixing the core holder special for CT and the sample position, starting an X-ray CT scanning device, and setting scanning parameters to obtain an initial CT scanning image of the core;
(4) carrying out image processing such as filtering and segmentation on the CT scanning image, and establishing a digital core image before steam huff and puff to obtain an initial core pore structure;
(5) opening the constant temperature box, adjusting the temperature to the simulated reservoir temperature, wherein the temperature of the common constant temperature box can be adjusted to 100-200 ℃;
(6) opening a constant-speed constant-pressure pump, setting a certain pressure and flow rate to supply liquid into a steam generator, wherein the pressure is generally 1-4.5 MPa, and the pressure is selected according to the principle that the pressure needs to be higher than saturated steam pressure, so that the dryness of the steam generated by the steam generator can be one hundred percent, and the flow rate is generally 0.01mL/min-0.8 mL/min;
(7) opening a steam generator, and adjusting the temperature of the steam generator to a certain temperature, wherein the temperature can be room temperature to 300 ℃;
(8) opening a switch a and a switch c, closing a switch b, injecting steam into the CT special core holder with the core and the reservoir sand-packed model, observing the reservoir sand-packed model, reservoir pressure in the steam injection process and volume change characteristics in the action range to simulate the steam throughput state in the real reservoir;
(9) after injecting steam into a certain PV number, closing the constant-speed constant-pressure pump and the steam generator, and closing the switch a;
the PV number refers to a Pore Volume (Pore Volume), and can be calculated according to the properties of the core and the size of the core, and the specific calculation method is as follows: PV (total volume) is multiplied by porosity, the number of PV injected in the experiment can be set according to requirements, and the pore structure of the core is changed only when steam flooding is generally over 100 PV;
(10) opening a switch b after a certain time (usually 6-8 hours), so that the produced liquid is obtained from the collector through the cooling effect of the pipeline and the condenser, and measuring the flow rate and the total amount of oil and water at the outlet end;
(11) closing the switch c after the outlet end does not discharge liquid any more, repeating the steps (3) and (4), and comparing the change of the pore structure of the rock core before and after steam huff and puff to obtain a change rule;
(12) and (4) ending the experiment, closing the constant temperature box, relieving the pressure of the hand-operated pump a and the hand-operated pump b to 0MPa, and taking out the rock core from the rock core holder special for CT.
The invention is not described in detail, reference is made to the prior art.
The invention has the beneficial effects that:
according to the invention, through a CT (computed tomography) in-situ experiment-based testing process for the pore structure and the seepage rule of the reservoir rock, the microstructure change and the seepage rule characteristics of the reservoir stratum of the unconsolidated sandstone heavy oil reservoir are accurately represented in the steam huff and puff process on the premise of not damaging the pore structure of the core. The problem that the pore structure change characteristics in the steam huff-and-puff process of the unconsolidated sandstone heavy oil reservoir cannot be tested by a conventional method is solved, and the micro description of the reservoir structure at a certain stage in the steam huff-and-puff process becomes possible.
Drawings
FIG. 1 is a schematic structural diagram of a device for accurately characterizing the pore structure change of a rock of a steam huff and puff reservoir based on a CT in-situ experiment;
FIG. 2 is a CT scan image of a core in an initial state;
FIG. 3 is a pore phase image of the core of FIG. 2;
FIG. 4 is a pore phase image of the core of FIG. 2 after steam throughput;
in the figure, 1-a constant-speed constant-pressure pump, 2-a steam generator, 3-a six-way valve a, 4-a pressure gauge a, 5-a switch a, 6-a special core holder for CT, 7-a six-way valve b, 8-a pressure gauge b, 9-a hand pump a, 10-a switch c, 11-a reservoir sand filling model, 12-a six-way valve c, 13-a pressure gauge c, 14-a hand pump b, 15-a switch b, 16-a condenser, 17-a collector and 18-an X-ray CT scanning device.
The specific implementation mode is as follows:
in order to make the technical problems, technical solutions and advantages of the present invention more apparent, the following detailed description is given with reference to the accompanying drawings and specific examples, but not limited thereto, and the present invention is not described in detail and is in accordance with the conventional techniques in the art.
Example 1:
a device for accurately representing the change of a pore structure of a rock of a steam huff and puff reservoir based on a CT (computed tomography) in-situ experiment comprises a constant-speed constant-pressure pump 1, a steam generator 2, a special core holder 6 for CT, a hand pump a 9, a hand pump b14, a reservoir sand filling model 11, a condenser 16, a collector 17 and an X-ray CT scanning device 18, wherein the constant-speed constant-pressure pump 1 is connected with the steam generator 2;
the ring pressure interface of the special core holder 6 for CT is communicated with a hand pump a 9 through a pipeline, the end A of the special core holder 6 for CT is respectively connected with a six-way valve a3 and a condenser 16 through a pipeline, the constant temperature and constant pressure pump 1 is connected with the six-way valve a3 through a steam generator 2, the condenser 16 is connected with a collector 17, the six-way valve a3 controls the inflow of fluid, and the condenser 16 is used for cooling the fluid flowing out of the outlet of the end A of the core holder 6 after the steam throughput is finished;
the end B of the CT special core holder 6 is connected with the upper inlet end of the reservoir sand filling model 11 through a pipeline, and the lower annular pressure interface of the reservoir sand filling model 11 is communicated with a hand pump B14 through a pipeline;
the six-way valve a3 is connected with a pressure gauge a 4, a switch a 5 is arranged on a pipeline between the six-way valve a3 and the end A of the CT special core holder, and a switch b 15 is arranged on a pipeline between the end A of the CT special core holder and the condenser 16; a six-way valve b 7 is arranged on a pipeline between a ring pressure interface of the core holder 6 special for CT and the hand pump a, and the six-way valve b 7 is connected with a pressure gauge b 8; a switch c10 is arranged on a pipeline between the B end of the special core holder for CT and the upper inlet end of the reservoir sand filling model 11, a six-way valve c 12 is arranged on a pipeline between the lower annular pressure interface of the reservoir sand filling model 11 and the hand pump B14, and the six-way valve c 12 is connected with a pressure gauge c 13;
the X-ray CT scanning device 18 is used for carrying out CT scanning on the rock core in the rock core holder to obtain rock core images before and after steam huff and puff of the rock core, and can extract pore phases and solid phases to analyze the influence of the steam huff and puff on the pore structure of the rock core by combining a digital rock core technology;
the six-way valve a3, the pressure gauge a 4, the CT special core holder 6, the six-way valve b 7, the pressure gauge b 8 and the reservoir sand filling model 11 are all arranged in a constant temperature box.
In the invention, the A end of the core holder special for CT is a double interface and is respectively connected with two pipelines, one pipeline is connected with a six-way valve a3, the other pipeline is connected with a condenser 16, a switch a is opened and a switch b is closed in the injection process, and the switch a is closed and the switch b is opened during the production after closing the well;
the condenser 16 is used to cool the production fluid at the outlet end to allow better flow of the production fluid to the collector.
The collector 17 is used for collecting the produced liquid which is taken in and out by steam, and can accurately measure the produced liquid amount and provide parameters for the calculation of the subsequent recovery ratio.
Example 2:
a device for accurately representing the change of a pore structure of a steam huff-puff reservoir rock based on a CT (computed tomography) in-situ experiment is shown in example 1, and is different from the prior art that a reservoir sand filling model 11 is used for simulating a real reservoir of a steam huff-puff heavy oil reservoir, the reservoir sand filling model is a container with a piston in the middle, an oil-containing sand body is filled at the upper part of the piston, the mineral composition, the oil-containing saturation and the permeability of the oil-containing sand body are all kept consistent with those of a rock core in a rock core holder, the lower part of the piston is filled with water, and a lower annular pressure interface is connected with a hand pump b and used for applying;
in the reservoir sand filling model, a wet filling method is adopted as the sand filling method, and the reservoir sand filling model with larger volume is connected with the core sand filling model because the core size is too small and the steam throughput cannot be effectively simulated, so that the steam throughput state in the real reservoir can be simulated. Because the piston capable of sliding and sealing is arranged in the sand filling model, the piston can slightly move along with the pressure change in the steam injection process, and the oil-containing sand body can expand along with the injection, so that the characteristics of reservoir pressure and volume change in an action range in the steam injection process are better met.
The hand pump b14 is used for pressurizing the reservoir sand filling model, and the hand pump b14 injects water into the bottom of the reservoir sand filling model by using a hydraulic principle so as to control the pressure of the sand filling model to be the simulated reservoir pressure.
Example 3:
the structure of the device is shown in embodiment 1, except that a constant-speed and constant-pressure pump 1 is used for supplying injected water to a steam generator and controlling the displacement speed, the injection speed range is 0.001-60 mL/min, and the pressure range is 0.001-60 MPa.
Example 4:
the device for accurately representing the pore structure change of the rock of the steam huff and puff reservoir based on the CT in-situ experiment is structurally shown as example 1, except that a steam generator 2 is used for heating water injected by a constant-speed constant-pressure pump until steam at a required temperature is obtained, and discharging the steam, wherein the steam temperature is 300 ℃ at most.
Example 5:
the structure of the device is shown in embodiment 1, and is different from that the special core holder 6 for CT is a Polyetheretherketone (PEEK) core holder specially suitable for an X-ray CT scanner, the PEEK cutting performance is excellent, the device is high-temperature resistant, the mechanical performance is good, the device has ray transmission performance, and a core can be installed in the core holder and scanned by X-ray CT, so that the microscopic pore structure characteristics of the core are obtained. The core holder is used for fixing the core and directly carrying out X-ray CT scanning on the core before and after the steam huff and puff process of the core.
Example 6:
the structure of the device for accurately representing the pore structure change of the rock of the steam huff and puff reservoir based on the CT in-situ experiment is shown in embodiment 1, and the difference is that the measuring ranges of a pressure gauge a 4, a pressure gauge b 8 and a pressure gauge c 13 are all 50MPa, and the precision is all 0.20 MPa.
Example 7:
the structure of the device for accurately representing the change of the pore structure of the rock of the steam huff and puff reservoir based on the CT in-situ experiment is shown in embodiment 1, except that an X-ray CT scanning device 18 is Zeiss MCT-400CT and is connected with a computer to display a scanned image of a rock core;
the collector 17 is an oil-water separator.
Example 8:
an experimental method of the device for accurately characterizing the pore structure change of the rock of the steam huff and puff reservoir based on the CT in-situ experiment in embodiment 1 comprises the following steps:
(1) selecting liquid nitrogen to freeze and drill a prepared core, loading the core into a core holder 6 special for CT without any treatment under the condition of keeping an initial pore structure unchanged, and filling oil-containing sand into a reservoir sand filling model by adopting a wet filling method;
(2) the hand-operated pump a 9 and the hand-operated pump b14 respectively perform confining pressure on the CT special core holder and the reservoir sand filling model, and the confining pressure reading is read through a pressure gauge b 8 and a pressure gauge c 13;
setting the initial confining pressure to be in the range of 1.5-2MPa, and continuously adjusting the confining pressure in the experimental process to keep the time higher than the upstream inlet pressure by 1.5-2 MPa;
(3) fixing the core holder 6 special for CT and the position of a sample, starting an X-ray CT scanning device 18, and setting scanning parameters to obtain an initial CT scanning image of the core;
(4) carrying out image processing such as filtering and segmentation on the CT scanning image, and establishing a digital core image before steam huff and puff to obtain an initial core pore structure;
(5) opening the constant temperature box 8, and adjusting the temperature to the temperature of the simulated reservoir;
(6) opening the constant-speed constant-pressure pump 1, and setting a certain pressure and flow rate to supply liquid into the steam generator, wherein the pressure is generally 2MPa, and the flow rate is generally 0.1 mL/min;
(7) turning on the steam generator 2, and adjusting the temperature of the steam generator to room temperature;
(8) opening a switch a 5 and a switch c10, closing a switch b 15, injecting steam into the CT special core holder 6 with the core and the reservoir sand-filled model 11, observing the reservoir sand-filled model, reservoir pressure in the steam injection process and volume change characteristics in the action range to simulate the steam throughput state in the real reservoir;
(9) after steam is injected into a certain PV number, the constant-speed constant-pressure pump 1 and the steam generator 2 are closed, and the switch a 5 is closed;
(10) after 7 hours, opening a switch b 15 to obtain the produced liquid from a collector 17 through the cooling action of a pipeline and a condenser 16, and measuring the flow rate and the total amount of oil and water at the outlet end;
(11) closing the switch c10 after the outlet end does not discharge liquid any more, repeating the steps (3) and (4), and comparing the change of the pore structure of the rock core before and after steam huff and puff to obtain a change rule;
(12) and (4) ending the experiment, closing the constant temperature box 8, relieving the pressure of the hand pump a 9 and the hand pump b14 to 0MPa, and taking out the rock core from the rock core holder special for CT.
FIG. 2 is a CT scanning image of 350 × 350 × 350 voxels (physical size is 1435 μm × 1435 μm × 1435 μm) taken in the initial state of the core, the temperature is room temperature, the pressure is 0, the flow rate is 0, the scanning time is 4 hours, and the scanning resolution is 4.1 μm;
FIG. 3 is a pore phase image after image segmentation in the state of FIG. 2;
fig. 4 is a CT scan image of the core taken at the same position as in the initial state after steam stimulation. The temperature is 200 ℃, the pressure is 0, the flow is 0, the scanning time is 4 hours, and the scanning resolution is 4.1 mu m;
as can be seen from fig. 3, in the initial state of the core, the core pore development is good, the pore volume is large, and the core pore is a typical pore structure of loose sandstone, as can be seen from fig. 4, the core pore is damaged by the influence of high-temperature steam, the isolated pore becomes more, the pore structure change is obvious, the pore change can be visually observed, the pore microstructure change in the steam huff and puff process of the oil reservoir and the influence thereof on the seepage rule can be explored by combining a graph processing technology, and theoretical and technical support is provided for a hot water flooding injection and production scheme in the process of developing the heavy oil reservoir.
While the foregoing is directed to the preferred embodiment of the present invention, it will be understood by those skilled in the art that various changes and modifications may be made without departing from the spirit and scope of the invention as defined in the appended claims.
Claims (9)
1. A device for accurately representing the change of a pore structure of a steam huff and puff reservoir rock based on a CT (computed tomography) in-situ experiment is characterized by comprising a constant-speed constant-pressure pump, a steam generator, a special core holder for CT, a hand-operated pump a, a hand-operated pump b, a reservoir sand filling model, a condenser, a collector and an X-ray CT scanning device;
the ring pressure interface of the special core holder for CT is communicated with a hand-operated pump a through a pipeline, the A end of the special core holder for CT is respectively connected with a six-way valve a and a condenser through pipelines, a constant-temperature constant-pressure pump is connected with the six-way valve a through a steam generator, the condenser is connected with a collector, the six-way valve a controls the inflow of fluid, and the condenser is used for cooling the fluid flowing out of the outlet of the A end of the core holder after the steam handling is finished;
the B end of the core holder special for CT is connected with the upper inlet end of the reservoir sand filling model through a pipeline, and the lower annular pressure interface of the reservoir sand filling model is communicated with the hand pump B through a pipeline;
the six-way valve a is connected with a pressure gauge a, a switch a is arranged on a pipeline between the six-way valve a and the end A of the special core holder for CT, and a switch b is arranged on a pipeline between the end A of the special core holder for CT and the condenser; a six-way valve b is arranged on a pipeline between a ring pressure interface of the core holder special for CT and the hand pump a, and the six-way valve b is connected with a pressure gauge b; a switch c is arranged on a pipeline between the end B of the special core holder for CT and the inlet end at the upper part of the reservoir sand filling model, a six-way valve c is arranged on a pipeline between the lower annular pressure interface of the reservoir sand filling model and the hand pump B, and the six-way valve c is connected with a pressure gauge c;
the X-ray CT scanning device is used for carrying out CT scanning on the rock core in the rock core holder so as to obtain rock core images before and after steam huff and puff of the rock core;
the six-way valve a, the pressure gauge a, the CT special core holder, the six-way valve b, the pressure gauge b and the reservoir sand filling model are all arranged in the constant temperature box.
2. The device for accurately characterizing the pore structure change of the rock of the steam huff and puff reservoir based on the CT in-situ experiment as claimed in claim 1, wherein the reservoir sand filling model is used for simulating a real reservoir of the steam huff and puff heavy oil reservoir, the reservoir sand filling model is a container with a piston in the middle, an oil-containing sand body is filled at the upper part of the piston, the mineral composition, the oil-containing saturation and the permeability of the oil-containing sand body are all consistent with those of a core in a core holder, the lower part of the piston is filled with water, and a lower ring pressure interface is connected with a hand-shaking pump b for applying confining pressure to the reservoir sand filling model.
3. The device for accurately characterizing the pore structure change of the rock of the steam huff and puff reservoir based on the CT in-situ experiment as claimed in claim 1, wherein the constant-speed and constant-pressure pump is used for supplying injected water to the steam generator and controlling the displacement speed, the injection speed can be in the range of 0.001-60 mL/min, and the pressure is in the range of 0.001-60 MPa.
4. The device for accurately characterizing the pore structure change of the rock of the steam huff and puff reservoir based on the CT in-situ experiment as claimed in claim 1, wherein the steam generator is used for heating the water injected by the constant-speed constant-pressure pump until the steam with the required temperature is obtained, and discharging the steam, and the temperature of the steam is up to 300 ℃.
5. The device for accurately characterizing the pore structure change of the rock of the steam huff and puff reservoir based on the CT in-situ experiment as claimed in claim 1, wherein the special core holder for CT is a polyetheretherketone core holder specially adapted for an X-ray CT scanner.
6. The device for accurately characterizing the pore structure change of the rock of the steam huff and puff reservoir based on the CT in-situ experiment as claimed in claim 1, wherein the pressure gauge a, the pressure gauge b and the pressure gauge c have the range of 50MPa and the accuracy of 0.20 MPa.
7. The device for accurately characterizing the pore structure change of the rock of the steam huff and puff reservoir based on the CT in-situ experiment as claimed in claim 1, wherein the X-ray CT scanning device is Zeiss MCT-400CT, and is connected with a computer for displaying the scanned image of the rock core.
8. The CT in-situ experiment-based device for accurately characterizing pore structure change of rock of a steam huff and puff reservoir according to claim 1, wherein the collector is an oil-water separator.
9. The experimental method of the device for accurately characterizing the pore structure change of the steam huff-and-puff reservoir rock based on the CT in-situ experiment as claimed in claim 1, comprising the following steps:
(1) selecting liquid nitrogen to freeze and drill a prepared core, loading the core into a core holder special for CT without any treatment under the condition of keeping an initial pore structure unchanged, and filling oil-containing sand into a reservoir sand filling model by adopting a wet filling method;
(2) the hand-operated pump a and the hand-operated pump b respectively carry out confining pressure on the CT special core holder and the reservoir sand filling model, and the confining pressure reading is read through a pressure gauge b and a pressure gauge c;
(3) fixing the core holder special for CT and the sample position, starting an X-ray CT scanning device, and setting scanning parameters to obtain an initial CT scanning image of the core;
(4) performing image processing on the CT scanning image, and establishing a digital core image before steam huff and puff to obtain an initial core pore structure;
(5) opening a constant temperature box, and adjusting the temperature to the temperature of the simulated reservoir;
(6) opening the constant-speed constant-pressure pump, and setting a certain pressure and flow rate to supply liquid into the steam generator, wherein the pressure is selected according to the principle that the pressure needs to be higher than the saturated vapor pressure, and the flow rate is 0.01mL/min-0.8 mL/min;
(7) opening the steam generator, and adjusting the temperature of the steam generator to a certain temperature;
(8) opening a switch a and a switch c, closing a switch b, injecting steam into the CT special core holder with the core and the reservoir sand-packed model, observing the reservoir sand-packed model, reservoir pressure in the steam injection process and volume change characteristics in the action range to simulate the steam throughput state in the real reservoir;
(9) after injecting steam into a certain PV number, closing the constant-speed constant-pressure pump and the steam generator, and closing the switch a;
(10) opening a switch b after 6-8 hours, so that the produced liquid is obtained from the collector through the cooling effect of the pipeline and the condenser, and metering the flow rate and the total amount of oil and water at the outlet end;
(11) closing the switch c after the outlet end does not discharge liquid any more, repeating the steps (3) and (4), and comparing the change of the pore structure of the rock core before and after steam huff and puff to obtain a change rule;
(12) and (4) ending the experiment, closing the constant temperature box, relieving the pressure of the hand-operated pump a and the hand-operated pump b to 0MPa, and taking out the rock core from the rock core holder special for CT.
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| CN113092234A (en) * | 2021-03-12 | 2021-07-09 | 中国石油大学(北京) | Pressure monitoring device for core huff and puff experiment |
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