CN108519399B - Device for researching fluid phase change generation between pores by combining nuclear magnetic resonance technology - Google Patents

Device for researching fluid phase change generation between pores by combining nuclear magnetic resonance technology Download PDF

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CN108519399B
CN108519399B CN201810374567.3A CN201810374567A CN108519399B CN 108519399 B CN108519399 B CN 108519399B CN 201810374567 A CN201810374567 A CN 201810374567A CN 108519399 B CN108519399 B CN 108519399B
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CN108519399A (en
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姚艳斌
雷欣
陆程
闻志昂
罗万静
马钰骅
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China University of Geosciences Beijing
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    • G01NINVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
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Abstract

The invention discloses a device for researching fluid phase change generation between pores by combining a nuclear magnetic resonance technology, which comprises an injection system, a nonmagnetic rock sample holder with an annular temperature isolating ring, a gas-liquid separator, an electronic balance, a gas flow measurer and a control system, wherein the front end of the rock sample holder is connected with the injection system, the tail end of the rock sample holder is connected with a back pressure valve, the other end of the back pressure valve is connected with the gas-liquid separator, a water path of the gas-liquid separator is connected with the electronic balance, and a gas path of the gas-liquid separator is connected with the. The device keeps the coexistence of the solid state and the molten state in the same core for experiment, ensures that the molten surface exists in the core and researches the change rule of the molten surface; the non-magnetic rock sample holder with the annular temperature isolating ring can clearly distinguish information such as porosity, pore structure change and the like of a part of a melting face by combining nuclear magnetic imaging and layered nuclear magnetic imaging; the experiment of the influence of the depressurization mode on the hydrate decomposition rule can be implemented, and the dynamic change rule of the hydrate deposit rock core under the condition of changing the external temperature and pressure condition is obtained.

Description

Device for researching fluid phase change generation between pores by combining nuclear magnetic resonance technology
Technical Field
The invention belongs to the technical field of natural gas hydrate reservoir exploration and research, and particularly relates to a device for researching the phase change of fillers or fluids among pores by combining a nuclear magnetic resonance technology.
Background
Natural gas hydrate is a transparent crystal formed by embedding gas molecules into a water cage under the conditions of low temperature and high pressure. Has attracted people's attention because of its huge reserves and environmental friendliness. Because the stable existence of hydrate crystals has strict limits on temperature and pressure conditions, hydrate deposits are found in frozen soil zones and wide shallow sea areas. Both the increase in temperature and the decrease in pressure cause the hydrate to decompose, which is an endothermic reaction that causes the ambient temperature to decrease, and the low temperature in turn limits the decomposition of the hydrate and forms a secondary hydrate. The existing exploitation method mainly comprises the steps of temperature rise, pressure reduction and chemical substance injection excitation, the economic benefit of raising the temperature in a reservoir and injecting a heat source is low, and the bottom pumping and pressure reduction exploitation is limited by the temperature. Therefore, in actual production, due to the influence of stratum factors, the range of the bottom hole hydrate which can be dissolved during production is limited, and only the part which can be dissolved can form the production. In order to determine the melting area range of the hydrate, the transition rule of the melting surface when the external temperature and pressure change becomes a key factor for determining the exploitation limit of the reservoir. At present, the research in the industry focuses on the static formation and decomposition rule of the hydrate, and the research on the transition rule of the melting surface during pressure reduction or temperature rise is not deep.
The low-field nuclear magnetic technology can monitor the water content in the measured rock core in real time, and the layered nuclear magnetic technology can detect the water content in a certain section of the volume in the rock core. And (3) putting the measured hydrate core into a low-field magnetic field, judging the molten part and the non-molten part by utilizing a nuclear magnetic imaging technology and a layered nuclear magnetic technology, and deducing the position of a molten surface, so that the law of the movement change of the molten surface is observed in a subsequent temperature rise or pressure drop experiment.
The invention provides a two-chamber temperature-controlled holder, which is used for adjusting the temperature of two chambers according to the situation of applied pressure until a part of hydrate in a rock core is in a solid state and a part of hydrate is in a molten state, wherein a dissolving surface just exists. The change and shift process of the melting surface can be researched under the condition of reducing pressure or raising temperature by combining the layered nuclear magnetic technology. Meanwhile, different gases can be injected into the rock core to carry out a displacement experiment, and the relation between the change of the melting surface and the porosity and permeability of the rock core is observed.
Disclosure of Invention
In order to solve the problems that the melting rule and the process of a hydrate reservoir are complex, the change rule of a melting surface is not clear, the melting limit of a hydrate is uncertain and the like, the invention provides a device for researching the phase change of fluid between pores by combining a nuclear magnetic resonance technology, which is used for researching the change rule of the melting surface when the temperature and the pressure change occur in a hydrate rock core.
In order to achieve the aim, the invention adopts the following technical scheme:
a device for researching fluid phase change generation among pores by combining a nuclear magnetic resonance technology comprises hardware and software, wherein the hardware comprises an injection system, a non-magnetic rock sample holder with an annular heat isolating ring, a gas-liquid separator, an electronic balance, a gas flow measurer and a control system; the control system comprises a computer and software, wherein the software comprises a communication acquisition module, a data processing module, a data display module, a data recording module, an experimental process control module and a data export module.
The nonmagnetic rock sample holder with the annular temperature insulating ring is a core component of the device, and consists of a pressure source inlet, a pressure source outlet, an upstream metal holder, a downstream metal holder, an upstream metal plug, a downstream metal plug, an upstream radial sealing ring, a downstream radial sealing ring, an upstream metal baffle ring, a downstream metal baffle ring, a left half cavity confining pressure and cooling liquid inlet conduit, the device comprises a left half cavity confining pressure and cooling liquid outlet, a right half cavity confining pressure and cooling liquid inlet guide pipe, a right half cavity confining pressure and cooling liquid outlet, a rock core cavity, a left half cavity pressure-bearing cavity, a right half cavity pressure-bearing cavity, a left half cavity annular piston, a left half cavity supporting structure, a radial left and right half cavity heat insulation separating ring, a right half cavity annular piston, a right half cavity supporting structure, a pressure-bearing rubber sleeve and two sections of PEEK filling plungers; the core is fixed from left and right sides respectively to two sections PEEK filling plungers, and the pressure-bearing gum cover wraps up in the core and the PEEK filling plunger outside, the holder is half chamber on a left side and half chamber on a right side by the middle part separation of core cavity, and the coolant liquid of two kinds of temperature differences is followed the coolant liquid circulation entry injection in half chamber on a left side respectively, right side respectively, and the export is discharged to there is the steady difference in temperature between the left and right half chamber in order to guarantee.
The annular temperature insulating ring is arranged at the upper stream of the nonmagnetic rock sample holder, a connecting port is reserved at the upper stream of the nonmagnetic rock sample holder, the lower stream of the nonmagnetic rock sample holder is connected with a back pressure valve, and the other end of the back pressure valve is connected with a gas-liquid separator. During the experiment, the rock core is placed into the rock core cavity, the rock core phase change product enters the back pressure valve through the lower reaches of the non-magnetic rock sample holder with the annular heat insulating ring, then enters the gas-liquid separator through the other end of the back pressure valve, the gas enters the gas flowmeter through the drying device, the gas flow is monitored in real time through the control system, and the liquid flows into the beaker with the electronic balance at the lower part for weighing.
The nonmagnetic rock sample holder with the annular temperature isolating ring can be placed in a low-field nuclear magnetic resonance instrument, maintains the nonuniform temperature in the rock core holder, and can measure the phase change of fillers among water gaps in the rock core in real time. The specific application method is as follows: the method comprises the steps of placing a nonmagnetic rock sample in a low-field nuclear magnetic resonance instrument, keeping the pressure of a left cavity and a right cavity same in real time, keeping the initial circulating temperature of the two cavities at a low temperature which can keep the pore fillers of the rock core solid, testing an initial nuclear magnetic signal after the pressure is stable, raising the temperature of the right cavity (close to the downstream cavity) to change the fillers in the pore of the downstream rock core into a mixed state of gas and water, testing the nuclear magnetic signal, carrying out a depressurization experiment after determining proper temperature (the half of the rock core can be in the solid state and the half can be in a gas-liquid mixed state), operating according to a set pressure gradient, and testing the pore, gas and water distribution conditions of the rock core through a nuclear magnetic spectrometer.
The annular heat insulating ring is arranged in a pressure-bearing space of the nonmagnetic rock sample holder and is divided into a left half cavity and a right half cavity which are separated by an annular rubber ring, and a left half cavity piston ring and a right half cavity piston ring are respectively arranged on two sides of the annular rubber ring.
The two confining pressure half-cavities are not necessarily separated when not confining pressure is applied, but are completely separated when pressurized. The annular heat insulation ring is positioned in the middle of the confining pressure cavity of the holder, corresponds to the middle part of the rock core after the rock core is placed into the rock core cavity, and extrudes the rubber ring by pistons in the two half cavities when the left half cavity and the right half cavity are filled with cooling liquid for pressurization, so that the rubber ring is pressed and deformed, and the two half cavities are completely separated.
And the left and right half-cavity supporting structures positioned below the rock core cavity and on two sides of the piston structure can support the rock core cavity. Some loosely cemented hydrate cores can deform and gather towards the middle in the experimental process, so that rubber sleeves wrapping the cores are bent downwards, and a certain supporting force is needed to ensure that the positions of the cores are not changed. The supporting device below the core cavity is a nonmagnetic supporting ring with the thickness just equal to the distance from the outer wall of the holder to the rubber sleeve, and the supporting ring only occupies about one fourth of the circumference on the longitudinal section, so that the supporting function can be achieved on one hand, and the pressure transmission is not influenced on the other hand.
And the inlets of the two confining pressure half cavities are respectively provided with a flow guide pipe, the injected cooling liquid is firstly conveyed to the position near the rock core, and is discharged from the confining pressure and cooling liquid outlet after undergoing cooling circulation. The design ensures that the path of the cooling liquid is as full as possible around the core, and the core cannot be cooled sufficiently due to the fact that the cooling liquid enters the confining pressure cavity and is discharged nearby.
A connecting port is reserved at the upstream of the non-magnetic-tape annular heat-insulating ring holder, and the downstream is connected with a back pressure valve. The pressure of the back pressure valve is reduced, gas and water in the rock core can be pumped out from the downstream, so that the downstream pressure of the rock core is reduced, the pore filler close to the downstream is subjected to phase change, the pore structure and the porosity of the rock core are changed, and the nuclear magnetic signal is changed accordingly. Along with the reduction of the pressure of the back pressure valve, the melting surface is close to the upstream, more solids in the core pore substances are melted, and the nuclear magnetic signals are further changed.
A connecting port is reserved at the upstream of the non-magnetic-tape annular heat-insulating ring holder and can be used for carrying out experiments on several groups of parallel artificial cores. The specific application method is as follows: taking several groups of artificial rock cores with the same conditions of porosity, permeability, particle components and the like, adjusting the temperature of each rock core to a proper temperature (half of the rock core can be in a solid state and half is in a gas-liquid mixed state), raising the temperature of the right half cavity to different temperature limits, reducing the pressure to the same pressure value, simultaneously carrying out nuclear magnetic monitoring, and comparing nuclear magnetic data of the several groups of artificial rock cores to obtain the influence of the temperature raising conditions on the dissolution of the pore filler when the pressure is reduced to the same limit.
The instrument can be used for carrying out two experimental operations, namely testing the state change rule of the reservoir rock core when the pressure changes and the reaction rule of the melting surface of the artificial rock core under the influence of the temperature rise limit on the depressurization measure.
The operation flow of the instrument for testing the phase state change of the reservoir core when the pressure changes is as follows:
1) placing the reservoir rock core into a nonmagnetic rock sample holder with an annular temperature isolating ring, placing the rock sample holder into a low-field nuclear magnetic resonance instrument, and connecting an outlet back pressure valve; pressurizing the cooling liquid by using a confining pressure pump; respectively opening inlets of the cooling groove of the left half cavity and the cooling groove of the right half cavity, and injecting low-temperature liquid with the same temperature for cooling;
2) after the core pore filler can be kept in a solid state and the temperature and the pressure are stable, heating the right cavity to dissolve the pore filler from the rightmost end, and heating until a pore filler molten surface just exists in the core to perform nuclear magnetic signal measurement;
3) reducing the pressure of the back pressure valve, reducing the downstream pressure of the clamp to a fixed value, and carrying out nuclear magnetic signal measurement;
4) and after the downstream pressure is stable, continuously reducing the pressure of the back pressure valve, reducing the downstream pressure of the clamp to a fixed value, carrying out nuclear magnetic signal measurement, observing the change of the total porosity, and observing the change of the gas concentration through nuclear magnetic imaging, thus completing the nuclear magnetic signal measurement under each pressure gear according to the set pressure change gear.
The operation flow of the instrument for researching the reaction of the melting surface of the artificial rock core to the depressurization measure under the influence of the temperature rise limit is as follows:
1) a plurality of artificial rock cores with the same porosity, permeability and particle components are respectively placed in a rock core holder without an annular thermal insulation ring and connected with an outlet back pressure valve;
2) pressurizing the cooling liquid by using a confining pressure pump; respectively opening inlets of the cooling groove of the left half cavity and the cooling groove of the right half cavity, and injecting low-temperature liquid with the same temperature for cooling;
3) after the temperature and pressure conditions are stable, the right half cavity is heated up to a certain temperature, and then the two sides are simultaneously subjected to the same-amplitude pressure reduction operation; simultaneously recording nuclear magnetic signals in real time;
4) and when the temperature of each group of rock cores is raised to different temperatures, the situation that the melting surfaces of pore fillers exist in the rock cores and the pressure reduction amplitude is the same is ensured, and the influence of different temperature raising thresholds on the gas flow obtained under the same pressure reduction measure is analyzed by comparing nuclear magnetic signals.
The invention has the advantages and beneficial effects that:
1) the solid state and the molten state can be kept in the same core for carrying out an experiment, the existence of a molten surface in the core can be ensured, and the change rule of the molten surface is researched in the experiment with the design temperature and the pressure as the change conditions;
2) the holder with the annular temperature insulating ring for the non-magnetic rock sample can clearly distinguish information such as porosity, pore structure change and the like of a part of a melting surface by combining layered nuclear magnetism;
3) the experiment of the influence of the depressurization mode on the hydrate decomposition rule can be carried out, and the dynamic change rule of the hydrate deposit rock core under the condition of changing the external temperature and pressure condition is obtained.
Drawings
FIG. 1 is a schematic diagram of the operation of the apparatus of the present invention.
In the figure: 1 is water injection pump, 2 is methane injection pump, 3 is helium injection pump, 4 is gas, liquid admission passage, 5 is the stop valve, 6 is the inlet flowmeter, 7 is the nuclear magnetic reaction cauldron that contains belt ring form heat insulating ring no magnetism rock core holder, 8 is the pump is enclosed to half chamber on the left side, 9 is the pump is enclosed to half chamber on the right side, 10 is temperature control device 1, 11 is temperature control device 2, 12 is the backpressure valve, 13 is vapour and liquid separator, 14 is the desicator, 15 is the soap bubble flowmeter, 16 is liquid graduated flask and electronic balance, 17 is temperature sensor, 18 is computer acquisition data system.
FIG. 2 is a structural diagram of the nonmagnetic rock sample holder with the annular temperature insulating ring.
In the figure, 1 is a pressure source inlet, 2 is an upstream metal holder, 3 is an upstream metal plug, 4 is an upstream radial sealing ring, 5 is an upstream metal baffle ring, 6 is a left half cavity confining pressure and cooling liquid inlet, 7 is a core cavity, 8 is a left half cavity pressure-bearing cavity, 9 is a radial zigzag left half cavity and right half cavity heat-insulating separating ring, 10 is a right half cavity pressure-bearing cavity, 11 is a right half cavity confining pressure and cooling liquid inlet, 12 is a downstream metal baffle ring, 13 is a downstream radial sealing ring, 14 is a downstream metal plug, 15 is a downstream metal holder, 16 is a pressure source outlet, 17 is a pressure-bearing rubber sleeve, 18 is a left half cavity confining pressure and cooling liquid outlet, 19 is a right half cavity confining pressure and cooling liquid outlet, 20 is a PEEK material filling plunger, 21 is a left half cavity confining pressure and cooling liquid inlet conduit, 22 is a right half cavity confining pressure and cooling liquid inlet conduit, 23 is a left half cavity annular piston, 24 is a right half cavity annular piston, and 25 is a left half-cavity supporting structure, and 26 is a right half-cavity supporting structure.
FIG. 3 is a partial view of a structural drawing of the nonmagnetic rock sample holder with the annular temperature insulating ring.
In the figure, 9 is a radial sawtooth-shaped left and right half cavity heat insulation separating ring, 23 is a left half cavity annular piston, and 24 is a right half cavity annular piston.
FIG. 4 is a longitudinal cutting view of the non-magnetic rock sample holder with the annular heat insulating ring.
In the figure, 1 is a core hole cavity, 2 is a pressure-bearing rubber sleeve, 3 is a confining pressure cavity (which can be a left half cavity or a right half cavity), 4 is the outer wall of the holder, 5 is a flow guide pipe, and 6 is a rubber sleeve bottom supporting structure.
Detailed Description
The present invention will be further described with reference to the following examples.
Examples
Referring to the attached drawings 1 and 2, the device for researching fluid phase change between pores by combining the nuclear magnetic resonance technology comprises an injection system, a non-magnetic-tape thermal insulation groove rock sample holder, a gas-liquid separator, an electronic balance, a gas flow measurer and a control system; the front end of the non-magnetic rock sample holder with the annular temperature isolating ring is connected with an injection system, the tail end of the non-magnetic rock sample holder is connected with a back pressure valve, the other end of the back pressure valve is connected with a gas-liquid separator, a water path of the gas-liquid separator is connected with an electronic balance, and a gas path is connected with a gas flow measurer; the control system comprises a computer and software, the software comprises a communication acquisition module, a data processing module, a data display module, a data recording module, an experimental process control module and a data export module, and the control system works in cooperation with the device and can be realized by using the prior art.
Referring to the attached figure 2, the nonmagnetic rock sample holder with the annular temperature isolating ring is a core component of the device, and comprises a pressure source inlet (1), a pressure source outlet (16), an upstream metal holder (2), a downstream metal holder (15), an upstream metal plug (3), a downstream metal plug (14), an upstream radial sealing ring (4), a downstream radial sealing ring (13), an upstream metal baffle ring (5), a downstream metal baffle ring (12), a left half cavity confining pressure and cooling liquid inlet (6), a left half cavity confining pressure and cooling liquid inlet conduit (21), a left half cavity confining pressure and cooling liquid outlet (18), a right half cavity confining pressure and cooling liquid inlet (11), a right half cavity confining pressure and cooling liquid inlet conduit (22), a right half cavity confining pressure and cooling liquid outlet (19), a rock core cavity (7), a left half cavity pressure-bearing cavity (8), a right half cavity pressure-bearing cavity (10), The PEEK filling device comprises a left half-cavity annular piston (23), a left half-cavity supporting structure (25), a radial left and right half-cavity heat insulation separating ring (9), a right half-cavity annular piston (24), a right half-cavity supporting structure (26), a pressure-bearing rubber sleeve (17) and two sections of PEEK filling plungers (20); two sections PEEK fill plunger (20) are fixed rock core (7) from left and right sides respectively, and pressure-bearing gum cover (17) wraps up in rock core (7) and PEEK fill plunger (20) outside, the holder is separated by the middle part of rock core cavity (7) and is half chamber (8) on the left side and half chamber (10) on the right side, and the coolant liquid that two kinds of temperatures are different is injected into from coolant liquid circulation entry (6, 11) in left and right half chamber respectively, and export (18, 19) are discharged to there is the steady difference in temperature between the assurance left and right half chamber.
The annular temperature insulating ring is arranged at the upper stream of the nonmagnetic rock sample holder, a connecting port is reserved at the upper stream of the nonmagnetic rock sample holder, the lower stream of the nonmagnetic rock sample holder is connected with a back pressure valve, and the other end of the back pressure valve is connected with a gas-liquid separator. The specific usage is that the rock core is placed in a rock core cavity, a rock core phase change product enters a back pressure valve through the lower stream of the non-magnetic rock sample holder with the annular heat insulating ring, then enters a gas-liquid separator through the other end of the back pressure valve, gas enters a gas flowmeter through a drying device, the gas flow is monitored in real time through a control system, and liquid flows into a beaker with an electronic balance at the lower part for weighing. The non-magnetic rock sample holder with the annular temperature isolating ring is placed in a low-field nuclear magnetic resonance spectrometer, the pressure of a left cavity and a right cavity is kept to be the same in real time, the initial circulating temperatures of the two cavities are both lower temperatures capable of keeping the pore fillers of the rock core solid, after the pressure is stable, an initial nuclear magnetic signal is tested, the temperature of the right cavity (close to the downstream cavity) is raised, the fillers in the pores of the downstream rock core are changed into a mixed state of gas and water, the nuclear magnetic signal is tested, after the proper temperature (the half of the rock core can be in the solid state and the half of the rock core is in the gas-liquid mixed state) is determined, a depressurization experiment is carried out, operation is carried out according to the set pressure gradient, and the.
Referring to fig. 3, fig. 3 is a partially enlarged view of fig. 2. The pressure-bearing space with the annular heat-insulating ring and without the magnetic rock sample holder is divided into a left half cavity and a right half cavity, and two rubber rings are arranged in a confining pressure cavity corresponding to the center of the rock core cavity and are respectively attached to the inner wall and the outer wall of the confining pressure cavity. Two opposite piston rings are arranged on two sides of the two rubber rings. When the two confining pressure half cavities are pressurized, the fluid pushes the piston ring to extrude the rubber ring, so that the rubber ring is deformed, and the effect of separating the left pressure cavity from the right pressure cavity is achieved.
Referring to fig. 4, this is a longitudinal cut through the holder. The supporting device below the core cavity is a nonmagnetic supporting ring with the thickness just equal to the distance from the outer wall of the holder to the rubber sleeve, and the supporting ring only occupies about one fourth of the circumference on the longitudinal section, so that the supporting device can play a role in supporting on one hand and does not influence the pressure transmission on the other hand.
A connecting port is reserved at the upstream of the non-magnetic-tape annular heat-insulating ring holder, and the downstream is connected with a back pressure valve. The pressure of the back pressure valve is reduced, gas and water in the rock core can be pumped out from the downstream, so that the downstream pressure of the rock core is reduced, the pore filler close to the downstream is subjected to phase change, the pore structure and the porosity of the rock core are changed, and the nuclear magnetic signal is changed accordingly. Along with the reduction of the pressure of the back pressure valve, the melting surface is close to the upstream, more solids in the core pore substances are melted, and the nuclear magnetic signals are further changed.
A connecting port is reserved at the upstream of the non-magnetic-tape annular heat-insulating ring holder and can be used for carrying out experiments on several groups of parallel artificial cores. The specific application method is as follows: taking several groups of artificial rock cores with the same conditions of porosity, permeability, particle components and the like, adjusting the temperature of each rock core to a proper temperature (half of the rock core can be in a solid state and half is in a gas-liquid mixed state), raising the temperature of the right half cavity to different temperature limits, reducing the pressure to the same pressure value, simultaneously carrying out nuclear magnetic monitoring, and comparing nuclear magnetic data of the several groups of artificial rock cores to obtain the influence of the temperature raising conditions on the dissolution of the pore filler when the pressure is reduced to the same limit.
Use example 1
The instrument can be used for testing the state change rule of the reservoir rock core when the pressure changes, and comprises the following operation steps:
1) placing the reservoir rock core into a nonmagnetic rock sample holder with an annular temperature isolating ring, placing the rock sample holder into a low-field nuclear magnetic resonance instrument, and connecting an outlet back pressure valve; pressurizing the cooling liquid by using a confining pressure pump; respectively opening inlets of the cooling groove of the left half cavity and the cooling groove of the right half cavity, and injecting low-temperature liquid with the same temperature for cooling;
2) after the core pore filler can be kept in a solid state and the temperature and the pressure are stable, heating the right cavity to dissolve the pore filler from the rightmost end, and heating until a pore filler molten surface just exists in the core to perform nuclear magnetic signal measurement;
3) reducing the pressure of the back pressure valve, reducing the downstream pressure of the clamp to a fixed value, and carrying out nuclear magnetic signal measurement;
4) and after the downstream pressure is stable, continuously reducing the pressure of the back pressure valve, reducing the downstream pressure of the clamp to a fixed value, carrying out nuclear magnetic signal measurement, observing the change of the total porosity, and observing the change of the gas concentration through nuclear magnetic imaging, thus completing the nuclear magnetic signal measurement under each pressure gear according to the set pressure change gear.
Use example 2
The instrument can be used for testing the reaction rule of the melting surface of the artificial rock core under the influence of the temperature rise limit to the pressure reduction measure, and comprises the following steps:
1) a plurality of artificial rock cores with the same porosity, permeability and particle components are respectively placed in a rock core holder without an annular thermal insulation ring and connected with an outlet back pressure valve;
2) pressurizing the cooling liquid by using a confining pressure pump; respectively opening inlets of the cooling groove of the left half cavity and the cooling groove of the right half cavity, and injecting low-temperature liquid with the same temperature for cooling;
3) after the temperature and pressure conditions are stable, the right half cavity is heated up to a certain temperature, and then the two sides are simultaneously subjected to the same-amplitude pressure reduction operation; simultaneously recording nuclear magnetic signals in real time;
4) and (3) heating each group of rock cores to different temperatures (the melting surfaces of pore fillers in the rock cores need to be ensured), reducing the pressure with the same amplitude, and analyzing the influence of different heating thresholds on the gas flow obtained under the same pressure reduction measure by comparing nuclear magnetic signals.
Finally, it should be noted that: it should be understood that the above examples are only for clearly illustrating the present invention and are not intended to limit the embodiments. Other variations and modifications will be apparent to persons skilled in the art in light of the above description. And are neither required nor exhaustive of all embodiments. And obvious variations or modifications therefrom are intended to be within the scope of the invention.

Claims (8)

1. A device for researching fluid phase change between pores by combining nuclear magnetic resonance technology is characterized in that: the device comprises an injection system, a non-magnetic rock sample holder with an annular temperature isolating ring, a gas-liquid separator, an electronic balance, a gas flow measurer and a control system, wherein the front end of the non-magnetic rock sample holder with the annular temperature isolating ring is connected with the injection system, the tail end of the non-magnetic rock sample holder with the annular temperature isolating ring is connected with a back pressure valve, the other end of the back pressure valve is connected with the gas-liquid separator, a water path of the gas-liquid separator is connected with the electronic balance, and a gas path of the;
the pressure-bearing space with the annular temperature isolating ring and without the magnetic rock sample holder is divided into a left half cavity and a right half cavity which are separated by an annular rubber ring, and a left half cavity piston ring and a right half cavity piston ring are respectively arranged at two sides of the annular rubber ring;
the non-magnetic rock sample holder with the annular heat insulation ring is composed of a pressure source inlet (1), a pressure source outlet (16), an upstream metal holder (2), a downstream metal holder (15), an upstream metal plug (3), a downstream metal plug (14), an upstream radial sealing ring (4), a downstream radial sealing ring (13), an upstream metal baffle ring (5), a downstream metal baffle ring (12), a left half-cavity confining pressure and cooling liquid inlet (6), a left half-cavity confining pressure and cooling liquid inlet conduit (21), a left half-cavity confining pressure and cooling liquid outlet (18), a right half-cavity confining pressure and cooling liquid inlet (11), a right half-cavity confining pressure and cooling liquid inlet conduit (22), a right half-cavity confining pressure and cooling liquid outlet (19), a rock core cavity (7), a left half-cavity pressure bearing cavity (8), a right half-cavity pressure bearing cavity (10), a left half-cavity annular piston (23), a left half-cavity supporting structure (25), The device comprises a radial left right half cavity heat insulation separating ring (9), a right half cavity annular piston (24), a right half cavity supporting structure (26), a pressure-bearing rubber sleeve (17) and two sections of PEEK filling plungers (20); two sections PEEK fill plunger (20) are fixed rock core (7) from left and right sides respectively, and pressure-bearing gum cover (17) wraps up in rock core (7) and PEEK fill plunger (20) outside, the holder is separated by the middle part of rock core cavity (7) and is half chamber (8) on the left side and half chamber (10) on the right side, and the coolant liquid that two kinds of temperatures are different is injected into from coolant liquid circulation entry (6, 11) in left and right half chamber respectively, and export (18, 19) are discharged to there is the steady difference in temperature between the assurance left and right half chamber.
2. The device for researching fluid phase change between pores in combination with nuclear magnetic resonance technology according to claim 1, wherein: a connecting port is reserved at the upstream of the non-magnetic rock sample holder with the annular temperature insulating ring, the downstream is connected with a back pressure valve, and the other end of the back pressure valve is connected with a gas-liquid separator; during the experiment, the rock core is placed into the rock core cavity, the rock core phase change product enters the back pressure valve through the lower reaches of the non-magnetic rock sample holder with the annular heat insulating ring, then enters the gas-liquid separator through the other end of the back pressure valve, the gas enters the gas flowmeter through the drying device, the gas flow is monitored in real time through the control system, and the liquid flows into the beaker with the electronic balance at the lower part for weighing.
3. The device for studying the phase transition of fluid between pores in combination with the nuclear magnetic resonance technology as claimed in claim 1, wherein: the left half cavity pressure-bearing cavity and the right half cavity pressure-bearing cavity are completely separated when being pressed; the annular heat insulation ring is positioned in the middle of the confining pressure cavity of the holder, corresponds to the middle part of the rock core after the rock core is placed into the rock core cavity, and extrudes the rubber ring by pistons in the two half cavities when the left half cavity and the right half cavity are filled with cooling liquid for pressurization, so that the rubber ring is pressed and deformed, and the two half cavities are completely separated.
4. The device for studying the phase transition of fluid between pores in combination with the nuclear magnetic resonance technology as claimed in claim 1, wherein: the left half cavity supporting structure and the right half cavity supporting structure are both located below the rock core cavity and on two sides of the piston structure, the supporting structure is a nonmagnetic supporting ring with the thickness just equal to the distance from the outer wall of the clamp holder to the rubber sleeve, and the supporting ring only occupies about one fourth of the circumference on the longitudinal section.
5. The device for studying the phase transition of fluid between pores in combination with the nuclear magnetic resonance technology as claimed in claim 1, wherein: and flow guide pipes are respectively arranged at the inlets of the left half cavity pressure-bearing cavity and the right half cavity pressure-bearing cavity, and the injected cooling liquid is firstly conveyed to the position near the rock core and is discharged from the confining pressure and cooling liquid outlet after undergoing cooling circulation.
6. The device for researching fluid phase change between pores in combination with nuclear magnetic resonance technology according to claim 1, wherein: a connecting port is reserved at the upstream of the non-magnetic clamper with the annular temperature isolating ring, and the downstream is connected with a back pressure valve; the pressure of the back pressure valve is reduced, so that gas and water in the rock core can be pumped out from downstream, the downstream pressure of the rock core is reduced, the pore filler close to the downstream is subjected to phase change, the pore structure and the porosity of the rock core are changed, and the nuclear magnetic signal is changed; along with the reduction of the pressure of the back pressure valve, the melting surface is close to the upstream, more solids in the core pore substances are melted, and the nuclear magnetic signals are further changed.
7. The device for researching fluid phase change between pores by combining with the nuclear magnetic resonance technology as claimed in claim 1, wherein the device can be used for testing and researching the state change rule of the reservoir core when the pressure changes, and the operation process is as follows:
1) placing the reservoir rock core into a nonmagnetic rock sample holder with an annular temperature isolating ring, placing the rock sample holder into a low-field nuclear magnetic resonance instrument, and connecting an outlet back pressure valve; pressurizing the cooling liquid by using a confining pressure pump; respectively opening inlets of the cooling grooves of the left half cavity pressure-bearing cavity and the right half cavity pressure-bearing cavity, and injecting low-temperature liquid with the same temperature for cooling;
2) after the core pore filler can be kept in a solid state and the temperature and the pressure are stable, heating the right cavity to dissolve the pore filler from the rightmost end, and heating until a pore filler molten surface just exists in the core to perform nuclear magnetic signal measurement;
3) reducing the pressure of the back pressure valve, reducing the downstream pressure of the clamp to a fixed value, and carrying out nuclear magnetic signal measurement;
4) and after the downstream pressure is stable, continuously reducing the pressure of the back pressure valve, reducing the downstream pressure of the clamp to a fixed value, carrying out nuclear magnetic signal measurement, observing the change of the total porosity, and observing the change of the gas concentration through nuclear magnetic imaging, thus completing the nuclear magnetic signal measurement under each pressure gear according to the set pressure change gear.
8. The device for researching fluid phase change between pores in combination with the nuclear magnetic resonance technology according to claim 1, wherein the device can be used for researching the reaction of the melting surface of the artificial rock core to the pressure reduction measure under the influence of the temperature rise limit, and the operation process is as follows:
1) a plurality of artificial rock cores with the same porosity, permeability and particle components are respectively placed in a rock core holder without an annular thermal insulation ring and connected with an outlet back pressure valve;
2) pressurizing the cooling liquid by using a confining pressure pump; respectively opening inlets of the cooling grooves of the left half cavity pressure-bearing cavity and the right half cavity pressure-bearing cavity, and injecting low-temperature liquid with the same temperature for cooling;
3) after the temperature and pressure conditions are stable, the right half cavity is heated to a certain temperature, the pressure reduction operation is started, and simultaneously the nuclear magnetic signals are recorded in real time;
4) and when the temperature of each group of rock cores is raised to different temperatures, the situation that the melting surfaces of pore fillers exist in the rock cores and the pressure reduction amplitude is the same is ensured, and the influence of different temperature raising thresholds on the gas flow obtained under the same pressure reduction measure is analyzed by comparing nuclear magnetic signals.
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