System and method for measuring physical property parameters of porous medium fluid

Abstract

The invention discloses a system and method for measuring the physical property parameters of porous medium fluid, and the system comprises a core device which comprises at least two first-class core modules and a plurality of second-class core modules which are located between the at least two first-class core modules and are connected in series; the injection device is used for injecting a first experimental gas during pore volume calibration and respectively injecting a second experimental gas and a fluid sample in a constant mass expansion experimental stage; the confining pressure device is used for providing simulated confining pressure for the rock core device; the experiment control device is used for controlling the on-off state of a pipeline between adjacent core modules, the pore volume of each core is calibrated according to the recorded balance pressure when the first experiment gas sequentially passes through different core modules, and then the pore volume of each core is calibrated when the fluid sample is controlled to saturate the first core module of the first type; and recording the balance pressure when the fluid sample is diffused to different core modules in sequence, and obtaining the physical property parameters of the formation fluid sample.

Description

Technical Field

[0001] The invention relates to the technical field of fluid phase state experiments in oil and gas field development, and in particular to a system and method for measuring physical property parameters of porous medium fluid. Background Art

[0002] The physical properties of oil and gas reservoir fluids are important basic data that are indispensable for determining the type of oil and gas reservoirs, calculating reserves, researching reservoir engineering and oil production technology, and formulating development plans. Usually, the method for obtaining the physical properties of oil and gas reservoir fluids is mainly based on the experimental methods formulated in the national standard "Analysis Methods for Physical Properties of Oil and Gas Reservoir Fluids" (GB / T26981-2020). However, with the continuous development of science and technology, experimental technology, experimental equipment, and experimental methods are constantly improving. Today, scholars have gradually discovered that the high-pressure physical properties of formation fluids in porous media in reservoirs are significantly different from the values ​​measured in conventional PVT cylinders, and the difference between the two increases with the decrease of the pore size in the porous media of the reservoir.

[0003] In the prior art entitled "Calculation Method and System for Fluid Phase State in Porous Media" (CN201910549893.8), based on the experimental results, a phase equilibrium calculation model was established that takes into account the capillary pressure effect, critical temperature and critical pressure offset, and pore size distribution in porous media. It was proposed that when the pore size is less than 100nm, the porous medium will have a significant impact on the phase state of the formation fluid. However, since the PVT phase state experiment is a high-temperature, high-pressure, and space-confined environment, it is extremely difficult to clarify the true phase characteristics of the formation fluid in the core.

[0004] In the prior art entitled "A device for monitoring phase changes of fluids in porous media" (CN201410315992.7), a device for monitoring phase changes of fluids in porous media is designed, and the phase changes of fluids at the end faces of the core can be directly observed through the perspective windows at both ends of the core holder. However, the problem with this device is that the fluid seen through the perspective window is no longer the state of the fluid in the porous medium of the core, but the state of the fluid entering the bulk phase space (the same as the state in the PVT cylinder).

[0005] In the prior art entitled “Device and Experimental Method for Fluid Phase Test in Porous Media” (CN201810297660.9), a device integrating ultrasonic detection, microscopic visualization and multi-point pressure monitoring methods was designed to study the phase characteristics of fluids in porous media. However, the fluid observed by the visualization technology in the device is no longer the state of the fluid in the porous medium of the core, but the state of the fluid entering the bulk phase space (the same as the state in the PVT cylinder). However, due to the very small amount of saturated fluid in the core, the ultrasonic detection technology causes extremely serious noise interference and cannot detect the sound wave signal of the fluid itself. Therefore, it is also difficult to clarify the phase characteristics of the fluid in the porous medium using this device.

[0006] In addition, in the prior art entitled "A system and method for measuring the bubble point pressure of crude oil in porous media" (CN201910185767.9), a system and method for measuring the bubble point pressure of crude oil in porous media was designed by connecting a long core holder in series with a PVT tube. However, the problem with this method is that the core and the PVT tube belong to two different media, and the phase states of the fluid in the two media are different. After the series connection, the bubble point measured by the PVT tube is no longer the phase state characteristic of the fluid in the porous medium of the core.

[0007] In summary, most of the current research devices and methods for the fluid phase state in porous media have some problems, which leads to great limitations in the experimental results and cannot reflect the true situation of the fluid phase state in the core. Summary of the invention

[0008] The purpose of the present invention is to provide a solution for determining the physical property parameters of formation fluids that can reflect the true state of the fluid phase in the core.

[0009] In order to solve the above technical problems, an embodiment of the present invention provides a system for measuring physical parameters of porous medium fluid, comprising: a core device, which includes at least two first-type core modules and a plurality of second-type core modules connected in series between the at least two first-type core modules, wherein the core size of the first-type core module is larger than the core size of the second-type core module; an injection device, which is used to inject a first experimental gas during pore volume calibration, and to inject a second experimental gas and a fluid sample respectively during a constant-quality expansion experiment; a confining pressure device, which is used to provide a simulated confining pressure to the core device; an experimental control device, which is used to control the on-off state of pipelines between adjacent core modules, wherein the pore volume of each core is calibrated according to the recorded equilibrium pressure when the first experimental gas passes through the core modules at different positions in turn, and then, under the condition that the fluid sample is controlled to saturate the first first-type core module, the equilibrium pressure when the fluid sample diffuses to the core modules at different positions in turn is recorded, and the physical parameters of the formation fluid sample are obtained in combination with the pore volume of each core.

[0010] Preferably, the injection device comprises: a double-cylinder plunger pump, which is used to transfer pressure to a piston container through a pressurized medium; a piston container, which is used to utilize the pressure power provided to inject the first experimental gas or the second experimental gas or the fluid sample into the first first-type core module, wherein the first experimental gas is preferably helium and the second experimental gas is preferably natural gas.

[0011] Preferably, the first / second type core module comprises: a first / second type core, a core holder and a core casing, the size range of the first type core is a core diameter of 10 cm and a core length of 3-15 cm, and the size range of the second type core is a core diameter of 1.8-3.8 cm and a core length of 1-15 cm.

[0012] Preferably, the core casing is a heating casing, wherein the system further comprises: a temperature control device, wherein the temperature control device is used to provide simulated formation temperature to the core device.

[0013] Preferably, the confining pressure device is connected to the core sidewalls in each of the core modules, and the confining pressure device adopts a double-cylinder plunger pump.

[0014] Preferably, the core modules are connected in series through a high-pressure series pipeline, wherein a corresponding connecting valve is provided at the end of each core module, and a pressure sensor for measuring the equilibrium pressure is provided at each connecting valve, wherein the system also includes a back pressure device hung at the outlet of the first first-type core module.

[0015] Preferably, the experimental control device carries out a calibration experiment of the core pore volume according to the following steps: controlling the confining pressure device to apply confining pressure to each core module; controlling the connecting valve arranged on the end face of each core module to open, thereby evacuating all cores; controlling the connecting valve for connecting the core modules in series to close; controlling the injection device to inject the first experimental gas from the inlet of the core device, and recording the volume of gas injected into the first core, and the first equilibrium pressure after the pressure stabilizes; controlling the connecting valve for connecting the first core and the second core to open, and recording the current first equilibrium pressure after the pressure stabilizes, thereby recording the first equilibrium pressure after the pressure stabilizes by sequentially controlling the connecting valve for connecting the core modules in series to open; obtaining the pore volume of each core according to the first equilibrium pressure recorded in different time periods.

[0016] Preferably, the experimental control device carries out the constant quality expansion experiment according to the following steps: controlling the connecting valve arranged at the end face of each core module to open, so as to evacuate all the cores; controlling the connecting valve for connecting the core modules in series to close; controlling the injection device to inject the second experimental gas from the inlet of the core device, and raising the pressure of the first core to the preset formation pressure by controlling the adjustment of the back pressure device; controlling the injection device to inject the fluid sample from the inlet of the core device, so that the fluid sample displaces the first core and completes the formation fluid saturation; controlling the valve arranged at the inlet of the core device to close; controlling the connecting valve for connecting the first core and the second core to open, so that the formation fluid in the first core diffuses to the second core, and recording the current second equilibrium pressure after the pressure stabilizes, and so on, by sequentially controlling the connecting valves for connecting the core modules in series to open, respectively recording the second equilibrium pressure after the pressure stabilizes; calculating the physical properties of the formation fluid sample according to the second equilibrium pressures at different time periods and the pore volume of each core.

[0017] Preferably, the physical property parameters include saturation pressure, wherein the step of calculating the saturation pressure of the formation fluid sample includes: drawing a curve characterizing the relationship between pressure and pore volume during the core expansion process, thereby obtaining the saturation pressure of the formation fluid sample by identifying the inflection point in the current pressure and pore volume relationship curve.

[0018] Preferably, the length of the high-pressure serial pipeline is 3-5 cm, wherein the pore volume of each core is also deducted from the volume of the high-pressure serial pipeline located at the front end of the corresponding core.

[0019] Preferably, the experimental control device is also used to configure the number of the first type core modules and the second type core modules according to the following step flow: conduct a PVT phase experiment on the formation fluid sample, determine the dissolved gas-oil ratio of the formation fluid in the PVT tube, the saturation pressure based on the PVT experiment and the pressure-volume relationship curve, and determine the porosity and permeability of the first type core sample and the second type core sample by a core analysis method; calculate the pressure drop value corresponding to each increase in unit core pore volume of the formation fluid sample according to the PV relationship in the pressure-volume relationship curve in which the pressure is greater than the saturation pressure based on the PVT experiment, and based on this, calculate the number of the second type core samples required to drop from the actual formation pressure to the saturation pressure based on the PVT experiment; calculate the number of the first type core samples required to drop from the saturation pressure based on the PVT experiment to the final pressure, wherein the final pressure is the pressure corresponding to 3 times the initial fluid volume required to saturate the first type core sample.

[0020] Preferably, the back-pressure device comprises: a back-pressure pump and a back-pressure valve, and the back-pressure pump is a single-cylinder plunger pump.

[0021] Preferably, the system also includes an oil and gas recovery device hung at the outlet of the first first-type core module, the oil and gas recovery device includes an oil and gas separation bottle and a gas meter, wherein the experimental control device is also used to obtain gas-oil ratio data from the oil and gas recovery device, and determine the timing of completing formation fluid saturation according to the changing state of the gas-oil ratio data.

[0022] On the other hand, a method for determining physical parameters of porous medium fluid is provided, the method is implemented by the system as described above, wherein the method comprises: constructing a core device, the core device comprising at least two first-type core modules and a plurality of second-type core modules connected in series between the at least two first-type core modules, wherein the core size of the first-type core module is larger than the core size of the second-type core module; a confining pressure device provides simulated confining pressure to the core device; an injection device injects a first experimental gas during pore volume calibration; an experimental control device controls the gap between adjacent core modules by adjusting the pressure between adjacent core modules; The pipeline on-off state is controlled, and the equilibrium pressure when the first experimental gas passes through the core modules at different positions in turn is continuously recorded, so as to calibrate the pore volume of each core; the injection device injects the second experimental gas and the fluid sample respectively in the constant quality expansion experiment stage; the experimental control device controls the pipeline on-off state between adjacent core modules while controlling the fluid sample to saturate the first first-type core module, and continuously records the equilibrium pressure when the fluid sample diffuses to the core modules at different positions in turn, and obtains the physical properties of the formation fluid sample in combination with the pore volume of each core.

[0023] Compared with the prior art, one or more embodiments of the above scheme may have the following advantages or beneficial effects:

[0024] The present invention proposes a system and method for measuring the physical property parameters of porous medium fluid. The system and method are mainly composed of a plurality of full-diameter cores and short cores connected in series, and are used to simulate the process of constant mass expansion of formation fluid in the reservoir, and determine the saturation pressure of the formation fluid and its related high-pressure physical property parameters by measuring the pressure and the corresponding volume of the fluid in the expansion process in the core. Therefore, the present invention can directly measure the relationship between the pressure and the corresponding volume of the formation fluid in the actual reservoir porous medium during expansion, accurately obtain the high-pressure physical property parameters such as the saturation pressure, deviation coefficient, compression coefficient and volume coefficient of the fluid in the core, clarify the real phase characteristics of the formation fluid in the reservoir porous medium, and provide objective basic parameters for the development plan design, reserve calculation and oil test and production of low-porosity and low-permeability oil and gas reservoirs, which has extremely wide promotion and application value.

[0025] Other features and advantages of the present invention will be described in the following description, and partly become apparent from the description, or understood by practicing the present invention. The purpose and other advantages of the present invention can be realized and obtained by the structures particularly pointed out in the description, claims and drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] The accompanying drawings are used to provide a further understanding of the present invention and constitute a part of the specification. Together with the embodiments of the present invention, they are used to explain the present invention and do not constitute a limitation of the present invention. In the accompanying drawings:

[0027] Figure 1 This is a schematic diagram of the overall structure of a system for measuring physical property parameters of porous medium fluid according to an embodiment of the present application.

[0028] Figure 2 This is a schematic diagram of the specific structure of a system for measuring physical property parameters of porous medium fluid according to an embodiment of the present application.

[0029] Figure 3 Schematic diagram of the implementation process of the system for measuring physical property parameters of porous medium fluid according to an embodiment of the present application.

[0030] Figure 4 It is a schematic diagram of the comparison effect of the PV relationship curve measured by the system for measuring the physical property parameters of porous medium fluid according to the embodiment of the present application and the traditional PVT cylinder.

[0031] Figure 5 It is a schematic diagram of the comparison effect of the inflection point in the PV relationship curve measured by the system for measuring the physical property parameters of porous medium fluid according to the embodiment of the present application and the traditional PVT cylinder.

[0032] Figure 6 Schematic diagram of the steps of a method for determining physical property parameters of a porous medium fluid according to an embodiment of the present application. DETAILED DESCRIPTION

[0033] The following will describe the implementation methods of the present invention in detail with reference to the accompanying drawings and embodiments, so that the implementation process of how the present invention applies technical means to solve technical problems and achieve technical effects can be fully understood and implemented accordingly. It should be noted that as long as there is no conflict, the various embodiments of the present invention and the various features in the embodiments can be combined with each other, and the technical solutions formed are all within the protection scope of the present invention.

[0034] In addition, the steps shown in the flowchart of the accompanying drawings can be executed in a computer system such as a set of computer executable instructions. Also, although a logical sequence is shown in the flowchart, in some cases, the steps shown or described can be performed in a sequence different from that here.

[0035] The terms used herein are only for describing specific embodiments and are not intended to limit exemplary embodiments. Unless the context clearly indicates otherwise, the singular forms "one", "one" and "one" used herein are also intended to include plural numbers. It should also be understood that the terms "include" and / or "comprise" used herein specify the existence of stated features, integers, steps, operations, units and / or components, without excluding the existence or addition of one or more other features, integers, steps, operations, units, components and / or combinations thereof.

[0036] The physical properties of oil and gas reservoir fluids are important basic data that are indispensable for determining the type of oil and gas reservoirs, calculating reserves, researching reservoir engineering and oil production technology, and formulating development plans. Usually, the method for obtaining the physical properties of oil and gas reservoir fluids is mainly based on the experimental methods formulated in the national standard "Analysis Methods for Physical Properties of Oil and Gas Reservoir Fluids" (GB / T26981-2020). However, with the continuous development of science and technology, experimental technology, experimental equipment, and experimental methods are constantly improving. Today, scholars have gradually discovered that the high-pressure physical properties of formation fluids in porous media in reservoirs are significantly different from the values ​​measured in conventional PVT cylinders, and the difference between the two increases with the decrease of the pore size in the porous media of the reservoir.

[0037] In the prior art entitled "Calculation Method and System for Fluid Phase State in Porous Media" (CN201910549893.8), based on the experimental results, a phase equilibrium calculation model was established that takes into account the capillary pressure effect, critical temperature and critical pressure offset, and pore size distribution in porous media. It was proposed that when the pore size is less than 100nm, the porous medium will have a significant impact on the phase state of the formation fluid. However, since the PVT phase state experiment is a high-temperature, high-pressure, and space-confined environment, it is extremely difficult to clarify the true phase characteristics of the formation fluid in the core.

[0038] In the prior art entitled "A device for monitoring phase changes of fluids in porous media" (CN201410315992.7), a device for monitoring phase changes of fluids in porous media is designed, and the phase changes of fluids at the end faces of the core can be directly observed through the perspective windows at both ends of the core holder. However, the problem with this device is that the fluid seen through the perspective window is no longer the state of the fluid in the porous medium of the core, but the state of the fluid entering the bulk phase space (the same as the state in the PVT cylinder).

[0039] In the prior art entitled “Device and Experimental Method for Fluid Phase Test in Porous Media” (CN201810297660.9), a device integrating ultrasonic detection, microscopic visualization and multi-point pressure monitoring methods was designed to study the phase characteristics of fluids in porous media. However, the fluid observed by the visualization technology in the device is no longer the state of the fluid in the porous medium of the core, but the state of the fluid entering the bulk phase space (the same as the state in the PVT cylinder). However, due to the very small amount of saturated fluid in the core, the ultrasonic detection technology causes extremely serious noise interference and cannot detect the sound wave signal of the fluid itself. Therefore, it is also difficult to clarify the phase characteristics of the fluid in the porous medium using this device.

[0040] In addition, in the prior art entitled "A system and method for measuring the bubble point pressure of crude oil in porous media" (CN201910185767.9), a system and method for measuring the bubble point pressure of crude oil in porous media was designed by connecting a long core holder in series with a PVT tube. However, the problem with this method is that the core and the PVT tube belong to two different media, and the phase states of the fluid in the two media are different. After the series connection, the bubble point measured by the PVT tube is no longer the phase state characteristic of the fluid in the porous medium of the core.

[0041] In summary, most of the current research devices and methods for the fluid phase state in porous media have some problems, which leads to great limitations in the experimental results and cannot reflect the true situation of the fluid phase state in the core.

[0042] Therefore, in order to solve one or more of the above technical problems, the present application proposes a system and method for determining the physical property parameters of porous medium fluid. The system and method accurately obtain the real high-pressure physical property parameters of the fluid in the porous medium of the reservoir, clarify the real phase characteristics of the fluid in the formation, and thus provide accurate data support for determining the type of oil and gas reservoirs, calculating reserves, and formulating reservoir engineering development plans.

[0043] Figure 1 Schematic diagram of the overall structure of the system for measuring the physical parameters of porous medium fluid according to the embodiment of the present application. Figure 1 As shown, the system for measuring physical property parameters of porous medium fluid (also referred to as "physical property parameter measurement system") described in the embodiment of the present invention includes: a core device A, an injection device B, a confining pressure device C and an experimental control device D.

[0044] The core device A includes: at least two first-type core modules A1 and several second-type core modules A2 connected in series between at least two first-type core modules. In an embodiment of the present invention, each core module is connected in series through a high-pressure series pipeline. First, several second-type core modules A2 are connected in series through a high-pressure series pipeline to form a second-type core module sequence. Then, at least two first-type core modules A1 are respectively arranged at the two end faces of the second-type core module sequence, that is, one first-type core module A1 is arranged at the end face at the entrance of the second-type core module sequence, and the remaining first-type core modules A1 are arranged at the end face at the exit of the second-type core module sequence. Similarly, the first-type core module A1 and its adjacent second-type core module A2 are connected in series through a high-pressure series pipeline. Among them, in an embodiment of the present invention, the end faces of the cores in adjacent core modules are arranged relative to each other.

[0045] In the embodiment of the present invention, the core size of the first type of core module A1 is greater than the core size of the second type of core module A2. The core size includes the core diameter and the core length. Specifically, the core diameter of the first type of core module A1 is greater than the core diameter of the second type of core module A2, and the core length of the first type of core module A1 is greater than the core length of the second type of core module A2.

[0046] The injection device B is connected to the inlet end of the first type of core module A1 in the core device A through a high pressure injection pipeline 22. Figure 2 In addition, if Figure 2 As shown, a high pressure output pipeline 29 is provided at the outlet of the last first type core module A1 in the core device A. The injection device B is used to inject experimental gas in the pore volume calibration stage and to inject formation fluid samples in the constant mass expansion test stage.

[0047] The confining pressure device C is connected to the core side wall in each core module A1, A2 in the core device A. The confining pressure device C is used to provide simulated confining pressure to each core module A1, A2 in the core device A, thereby simulating the squeezing state of the overburden rock pressure actually received by the sample core in the formation.

[0048] The experimental control device D is used to control the on-off state of the pipelines between adjacent core modules A1 and A2. In other words, the experimental control device D is used to control the on-off state of the high-pressure pipelines (including high-pressure series pipelines, high-pressure injection pipelines and high-pressure output pipelines) at the end faces of each core module A1 and A2.

[0049] The experimental control device D controls the on-off state of the pipeline between the adjacent core modules A1 and A2 to continuously record the equilibrium pressure (recorded as the first equilibrium pressure) when the first experimental gas passes through the core modules A1 and A2 at different positions in turn, thereby calibrating the pore volume of each core. In addition, the experimental control device D also controls the on-off state of the pipeline between the adjacent core modules A1 and A2 to continuously record the equilibrium pressure (recorded as the second equilibrium pressure) when the formation fluid sample diffuses to the core modules A1 and A2 at different positions in turn when controlling the formation fluid sample to saturate the first first-type core module A1, and finally obtains the physical property parameters of the formation fluid sample in combination with the pore volume of each core.

[0050] In this way, the present invention achieves accurate measurement of the pressure of a high-pressure fluid sample in a constant-quality expansion process in a rock core and its corresponding pore volume.

[0051] Figure 2 This is a schematic diagram of the specific structure of the system for measuring the physical parameters of porous medium fluid according to the embodiment of the present application. Figure 2 , the specific structure of the physical property parameter measurement system described in the embodiment of the present invention is explained.

[0052] like Figure 2 As shown, the first type core module A1 includes: a first type core 2, core holders 1, 10 (full diameter core holders) and a core sleeve 6. In one embodiment, the size range of the first type core is 10 cm in core diameter and 3-15 cm in core length. The second type core module A2 includes: a second type core 4, core holders 3, 5, 7, 8, 9 (short core holders) and a core sleeve 6. In one embodiment, the size range of the second type core is 1.8-3.8 cm in core diameter and 1-15 cm in core length.

[0053] A corresponding connecting valve 11, 13, 15, 16, 17, ... is provided at the end 18 of each core module A1, A2. Specifically, a corresponding connecting valve is provided on each high-pressure series pipeline, high-pressure injection pipeline and high-pressure output pipeline to connect the core modules in series. In the embodiment of the present invention, the connecting valve on each high-pressure series pipeline, high-pressure injection pipeline and high-pressure output pipeline is a three-way valve.

[0054] The full-diameter core holders 1 and 10 are used to clamp the full-diameter core 2. The first type of core 2 is wrapped with a flexible tube (rubber tube or high-pressure heat shrink tubing) 6, leaving only the two end faces of the core. Among them, the full-diameter core 2 in the full-diameter core holder 1 is first used to saturate the high-pressure formation fluid, and then the fluid in the full-diameter core 2 is expanded and diffused to the cores in the other holders. The reason why the first core is selected as the full-diameter core 2 is that the full-diameter core has a large pore volume and a large amount of saturated formation fluid, which is convenient for subsequent expansion. After the full-diameter core 2 in the full-diameter core holder 1 is fully saturated with the formation fluid, it is connected to the connecting valve 13 through a 1 / 16-inch high-pressure series pipeline 12 and then connected to the short core holder 3. The short core holders 3, 5, 7, 8, and 9 are used to clamp the short core 4. The second type of core 4 is also wrapped with a flexible tube (rubber tube or high-pressure heat shrink tubing) 6, leaving only the two end faces of the core. The short core holders 3, 5, 7, 8, 9 are connected in series in sequence through a 1 / 16-inch high-pressure pipeline 12 and a connecting valve 13.

[0055] It should be noted that the present invention does not specifically limit the number of the first type of core modules A1 and the number of the second type of core modules A2. Those skilled in the art can adjust the number of full-diameter cores and short cores according to the experimental pressure (formation pressure and saturation pressure) and the required expansion volume.

[0056] In the embodiment of the present invention, the high-pressure connecting pipeline 12 is preferably a 1 / 16-inch high-pressure pipeline 12. Such pipelines are required to be as short as possible, wherein the length of each high-pressure series pipeline 12 is preferably 3-5 cm to ensure that the volume in the pipeline is as small as possible.

[0057] refer to Figure 2, the injection device B includes: a double-cylinder plunger pump 19 and a piston container 21. Among them, the two plunger pumps in the double-cylinder plunger pump 19 are respectively connected to the two-way storage containers in the piston container 21 through the corresponding two-way valves 20. The double-cylinder plunger pump 19 is used to transfer pressure to the piston container through a pressure medium. The piston container 21 is used to inject the first experimental gas or the second experimental gas or the formation fluid sample into the first first-type core module A1 using the pressure power provided. The first experimental gas is preferably helium. The second experimental gas is preferably natural gas. Specifically, the double-cylinder plunger pump 19 is used to provide displacement power to the piston container 21, and the pressure in the double-cylinder plunger pump 19 is transmitted to the piston container 21 through distilled water as a pressure medium, so that the piston pushes the first experimental gas or the second experimental gas or the formation fluid sample into the full-diameter core clamp 1.

[0058] The confining pressure device C is connected to the side wall of the core in each core module A1, A2. The confining pressure device C is implemented by a double-cylinder plunger pump 28. Specifically, the double-cylinder plunger pump 28 in the confining pressure device C is respectively connected to each core module A1, A2 through a high-pressure injection pipeline 22 connected to the side wall of each core, so that the double-cylinder plunger pump 28 applies pressure to the flexible tube 6 wrapping the core to simulate the extrusion of the overlying rock pressure on the core, wherein the pressure medium is distilled water.

[0059] In addition, the core casing 6 is a heating casing. To this end, the physical property parameter measurement system described in the embodiment of the present invention further includes: a temperature control device 27. The temperature control device is used to provide simulated formation temperature to each core module A1, A2 in the core device A. In one embodiment, the temperature control device is a temperature control box 27. Specifically, the core holder is wrapped by the heating sleeve 6, and the temperature of the heating sleeve is controlled by the temperature control box 27, thereby controlling and adjusting the core temperature so that the temperature of each core matches the actual formation temperature.

[0060] In addition, the physical property parameter determination system described in the embodiment of the present invention also includes a back pressure device (not numbered) hung at the outlet of the first first-type core module A1. The back pressure device includes: a back pressure pump 23 and a back pressure valve 25. The back pressure pump adopts a single-cylinder plunger pump 23. Specifically, the single-cylinder plunger pump 23 is used to provide pressure for the back pressure valve 25, and the pressure at the outlet end of the full-diameter core holder 1 is adjusted by controlling the back pressure valve 25.

[0061] In the embodiment of the present invention, a two-way valve 14 is provided at the front end of the back pressure valve 25. The two-way valve 14 is used to control the connection relationship between the back pressure device and the first first-type core module A1. Specifically, a two-way valve 14 is provided at the front end of the back pressure valve 25, and the experimental control device D controls the two-way valve 14 to further control the switching between the full-diameter core 2 and the three-way valve 13 after the formation fluid is saturated. When the two-way valve 14 is opened, it is used to saturate the full-diameter core 2; when the saturation is completed, the two-way valve 14 needs to be closed.

[0062] Furthermore, the physical property parameter determination system described in the embodiment of the present invention further includes: an oil and gas recovery device (not numbered) hung at the outlet of the first first-type core module A1. The oil and gas recovery device is hung at the rear end of the back pressure valve 25 in the back pressure device. The oil and gas recovery device includes an oil and gas separation bottle 24 and a gas meter 26.

[0063] In addition, at each connecting valve arranged at the end face of each core module A1, A2, a pressure sensor 18 for measuring the equilibrium pressure is arranged, thereby forming a pressure monitoring group. The pressure monitoring group (including pressure sensors connected to three-way valves 11, 13, 15, 16, etc.) is used to measure the pressure at both ends of all full-diameter cores and short cores. Each pressure sensor 18 is connected to the three-way valves 11, 13, 15, 16, 17, etc. at the corresponding position. For example, in an embodiment of the present invention, the switch of the three-way valve 11 only controls the connection of the two (pipeline) connecting ports of the valve, and does not control the connection of the pressure sensor 18, that is, the pressure sensor 18 is always connected to one of the pipeline connecting ports of the three-way valve 11, and is connected to the other pipeline connecting port of the three-way valve 11 after the valve is opened. In this way, the volume of the connecting pipeline between the core clamps can be reduced, thereby ensuring the accuracy of the experimental results.

[0064] Figure 3 The schematic diagram of the implementation process of the system for measuring the physical property parameters of porous medium fluid in the embodiment of the present application. Figure 3 , the specific implementation process of the physical property parameter measurement system described in the embodiment of the present invention is described.

[0065] Before the system is built (before the experiment begins), the number of the first type of core modules and the number of the second type of core modules need to be configured using the above-mentioned experimental control device D according to the following steps. Specifically, first, a PVT phase state experiment is performed on the formation fluid sample to determine the dissolved gas-oil ratio of the formation fluid in the PVT tube, the saturation pressure based on the PVT experiment, and the pressure-volume relationship curve, and the porosity and permeability of the first type of core sample and the second type of core sample are determined by the core analysis method; then, according to the PV relationship in which the pressure in the measured pressure-volume relationship curve is greater than the saturation pressure based on the PVT experiment, the pressure drop value corresponding to each increase in the unit core pore volume of the formation fluid sample is calculated, and according to the pressure drop value corresponding to the core pore volume, the number of the second type of core samples required to reduce the actual formation pressure to the saturation pressure based on the PVT experiment is calculated; finally, the number of the first type of core samples required to reduce the saturation pressure based on the PVT experiment to the final pressure is calculated, wherein the final pressure is the pressure corresponding to the volume of the injected fluid sample reaching 3 times the initial fluid volume required to saturate the first type of core sample.

[0066] Specifically, before the experiment begins, it is necessary to conduct a PVT phase state experiment on the formation fluid sample to be tested in accordance with the national standard "Analysis Method for Physical Properties of Oil and Gas Reservoir Fluids" (GB / T26981-2020) to determine the dissolved gas-oil ratio, saturation pressure, and pressure-volume (PV) relationship curve of the formation fluid in the PVT tube. In addition, it is necessary to measure the porosity and permeability of several core samples such as the full-diameter core 2 and short core 4 required in accordance with the national standard "Core Analysis Method" (GB / T 29172-2012). Then, according to the saturation pressure determined based on the PVT experiment, the saturation pressure difference (i.e., the difference between the formation pressure and the saturation pressure) is calculated, and combined with the PV relationship in the pressure-volume (PV) relationship curve of the formation fluid sample, the pressure reduction value corresponding to each increase in the volume of the core pores of the formation fluid sample is calculated, and the number of short cores required to reduce the original formation pressure to the saturation pressure determined based on the PVT experiment (PVT tube measurement) is further calculated. In addition, it is also necessary to calculate the number of cores required when the pressure in the PV curve continues to drop from the saturation pressure to the final pressure (i.e., the pressure corresponding to 3 times the initial fluid volume), which is the number of core samples of the first type.

[0067] It should be noted that when the pressure is greater than the saturation pressure, a short core with as small a pore volume as possible is selected to avoid the pressure from decreasing too quickly due to the pore volume being too large, and directly skipping the saturation pressure; when the pressure is less than the saturation pressure, a short core or a full-diameter core with a large pore volume can be selected to achieve the purpose of quickly reducing to the final pressure. To this end, the embodiment of the present invention carries out a fluid saturation pressure measurement experiment by providing a core device formed by at least two first-type core modules and a plurality of core modules located between the at least two first-type core modules, thereby effectively controlling the speed of pressure change and improving the accuracy of the final measurement result.

[0068] Then, the experiment control device D first controls the experiment of calibrating the pore volume of each core under the confining pressure. The experiment control device D carries out the calibration experiment of the core pore volume according to the following steps:

[0069] Control the confining pressure device C to apply confining pressure to each core module A1 and A2;

[0070] Control the connecting valves arranged on the end faces of each core module A1 and A2 to open, so as to evacuate all the cores;

[0071] Control the connection valves used to connect the core modules A1 and A2 in series to close;

[0072] Controlling the injection device B to inject the first experimental gas from the inlet of the core device A, and recording the volume of the gas injected into the first core and the first equilibrium pressure after the pressure is stabilized;

[0073] Control the connecting valve for connecting the first core and the second core to open, and record the current first equilibrium pressure after the pressure stabilizes;

[0074] Similarly, the first equilibrium pressure after the pressure is stabilized is recorded respectively by sequentially controlling the connecting valves for connecting the core modules in series to open;

[0075] According to the first equilibrium pressure recorded at different time periods, the pore volume of each core was obtained.

[0076] Specifically, S1. The experimental control device D opens all valves controlling the confining pressure of the core holder, so that the pressure generated by the double-cylinder plunger pump 28 is transmitted to each core holder, and the confining pressure is applied to the overlying rock pressure of the formation; S2. The experimental control device D opens and controls all valves 11, 13, 15, 16, etc. set on the end face of each core module; S3. The experimental control device D controls all cores to be vacuumed at the same time from the three-way valves 11 and 17 respectively, until the experimental control device D detects that the readings of the pressure sensors corresponding to all cores are consistent; S4. The experimental control device D closes all valves 13, 15, 16, etc. used to connect the core holders in series, thereby disconnecting the core in each section of the core holder; S5. Under the control of the experimental control device D, the injection device B injects helium at a constant pressure into the full-diameter core 2 from the three-way valve 11, and the experimental control device D records the volume V of helium entering the core 2 at a constant pressure. 1 , and when the pressure at valve 11 is stable, record the pressure P in core 2 1 (pressure at valve 11); S6, the three-way valve 13 is opened by the experimental control device D again until the pressure in the core holders 1 and 3 is stable (i.e., the pressure at the front end of the first core and the second core) and remains consistent. At this time, the experimental control device D records the current equilibrium pressure as P 2 , so through the formula V 2 =Z 2 ·P 1 ·V 1 / (Z 1 ·P 2 )-V 1 (This formula is derived from PV = ZnRT, where Z 1 , Z 2 Respectively represent P 1 and P 2 The deviation factor of helium gas can be obtained by looking up the table), and then the pore volume V of the short core 4 is calculated. 2 Next, S6, open the three-way valve 15 again, repeat the above step S6 and the calculation formula to calculate the core pore volume in the core holder 5, until all the core pore volumes are calculated, and then stop the calibration experiment.

[0077] Next, the experiment control device D continues to control the saturated formation fluid experiment and fluid physical parameter measurement experiment of the full-diameter core 2 under the confining pressure. The experiment control device D carries out the constant quality expansion experiment according to the following steps:

[0078] Control the connecting valves arranged on the end faces of each core module A1 and A2 to open, so as to evacuate all the cores;

[0079] Control the connection valves used to connect the core modules A1 and A2 in series to close;

[0080] Control the injection device B to inject the second experimental gas from the inlet of the core device A, and control the adjustment of the back pressure device so that the pressure of the first core is increased to the preset formation pressure;

[0081] Controlling the injection device B to inject the formation fluid sample from the inlet of the core device A, so that the formation fluid sample displaces the first core and completes the formation fluid saturation;

[0082] Control the valve disposed at the inlet of the core device A to close;

[0083] Controlling the connecting valve for connecting the first core and the second core to open, so that the formation fluid in the first core diffuses to the second core, and recording the current second equilibrium pressure after the pressure stabilizes;

[0084] Similarly, the connecting valves for the core modules A1 and A2 connected in series are controlled to open in sequence, and the second equilibrium pressure after the pressure is stabilized is recorded respectively;

[0085] The high-pressure physical property parameters of the formation fluid sample are calculated based on the second equilibrium pressure at different time periods and the pore volume of each core.

[0086] In one embodiment, the high-pressure physical property parameter includes saturation pressure. Specifically, in the process of calculating the saturation pressure, a curve representing the relationship between pressure and pore volume during the core expansion process is drawn according to the second equilibrium pressure in different time periods and the pore volume of each core, so as to obtain the saturation pressure of the formation fluid sample by identifying the inflection point in the curve of the relationship between the current pressure and the pore volume.

[0087] Specifically, M1. The experimental control device D re-evacuates all the cores in series, and the vacuuming method refers to the above steps S1 to S3; M2. The experimental control device D closes all valves 13, 15, 16, etc. used for connecting the core clamps in series, thereby disconnecting the core in each core clamp; M3. Under the control of the experimental control device D, the three-way valve 11 and the two-way valve 14 are opened, and then the double-cylinder plunger pump 19 is used to inject natural gas into the full-diameter core 2 to fully saturate the natural gas. At the same time, the single-cylinder plunger pump 23 is adjusted by controlling the back pressure valve 25, so that the pressure of the core 2 (according to the pressure at the valve 11) is increased to the formation pressure; M4. Under the control of the experimental control device D, the injection device B injects a formation fluid sample from the three-way valve 11 into the full-diameter core 2, so that the formation fluid displaces the natural gas and completes the saturation of the formation fluid.

[0088] In one embodiment, the experimental control device D is also used to obtain gas-oil ratio data from the oil and gas recovery device, and determine the timing of completing the formation fluid saturation according to the change state of the current gas-oil ratio data. Specifically, when the output gas-oil ratio measured by the oil-gas separation bottle 24 and the gas meter 26 remains unchanged, it is determined that the current formation fluid saturation task is completed.

[0089] Next, M5, when the full-diameter core 2 is saturated with formation fluid, the experimental control device D closes the three-way valve 11 and the two-way valve 14; M6, the experimental control device D opens the three-way valve 13 to allow the formation fluid sample in the full-diameter core 2 to diffuse into the short core 4. When the port pressures of the full-diameter core 2 and the short core 4 are consistent, that is, when the pressure sensor reading at the valve 11 is consistent with the pressure sensor readings at the valves 13 and 15 (at this time, the three-way valve 15 is in a closed state, but the pipeline connection port connected to the pressure sensor is connected to the one-way pipeline connection port connected to the core holder 3, that is, although the valve 15 is in a closed state, the pressure sensor at the valve 15 can still measure the pressure at the outlet of the core holder 3), the experimental control device D records the pressure at this time, which is recorded as the second equilibrium pressure; M7, the experimental control device D opens the three-way valve 15 again to allow the formation fluid sample to diffuse again. The formation fluid sample is dispersed into the core of the core holder 5. When the port pressures of the full-diameter core 2, the short core 4 and the second short core are all consistent, that is, when the pressure sensor readings at the valves 11, 13, 15 and 16 are consistent, the experimental control device D records the pressure at this time, which is recorded as the second equilibrium pressure; M8, repeat the above step M7 again, so that the formation fluid sample diffuses to the next core, and the corresponding second equilibrium pressure is recorded by the experimental control device D until the formation fluid sample enters the last full-diameter core and the second equilibrium pressure is recorded, and the current constant quality expansion experiment ends; M9, according to the (second) equilibrium pressure of the formation fluid expansion in each core obtained in steps M6-M8 and the corresponding core pore volume, the corresponding relationship between the pressure and the pore volume during the expansion of the formation fluid in the core is obtained, and the saturation pressure of the current formation fluid sample in the core is determined by the inflection point of the current pressure-pore volume curve. In addition, the present invention can also calculate other reasonable parameters such as the deviation coefficient, compression coefficient and volume coefficient of the formation fluid sample in the core, wherein the calculation method refers to the national standard "Core Analysis Method" (GB / T 29172-2012).

[0090] Furthermore, since the calibrated pore volume of each core includes the volume of the fluid in the 1 / 16-inch high-pressure serial pipeline 12, although the internal volume of the 1 / 16-inch high-pressure pipeline is very small, it will still affect the measurement results. Therefore, in the embodiment of the present invention, the pore volume of each core will also be subtracted from the (total) volume of the high-pressure serial pipeline located at the front end of the corresponding core, that is, the influence of the volume of the high-pressure serial pipeline on the measurement results needs to be removed.

[0091] Specifically, in the above step M9, when the formation fluid sample enters the nth core, the corresponding actual fluid volume in the core should be the total pore volume of the n cores (the volume calibrated by helium) minus the volume of (n-1) high-pressure series pipelines (the pipeline volume is calculated by measuring the pipeline length).

[0092] The physical property parameter measurement system of the present invention is described below by applying the implementation process of the physical property parameter measurement system of the present invention to a specific oil field:

[0093] The average permeability of a certain oil field reservoir is about 0.11×10 -3 μm 2 The average porosity is 6.8%, which belongs to a tight sandstone reservoir. The formation fluid type is a condensate gas reservoir, the formation temperature is 110°C, and the formation pressure is 32MPa. The phase characteristics of the condensate gas in the reservoir are different from the results measured in the PVT cylinder, so it is necessary to further measure the dew point pressure of the condensate gas in the reservoir.

[0094] (1) Before the experiment, the PVT phase state experiment of the condensate gas sample was carried out according to the national standard "Analysis Method of Physical Properties of Oil and Gas Reservoir Fluids" (GB / T26981-2020), and its dew point pressure was measured to be 26.36 MPa and the dissolved gas-oil ratio was 3934 m 3 / m 3 , and obtained the pressure-volume (PV) relationship curve. In addition, it is also necessary to measure the porosity and permeability of several core samples such as the required full-diameter core and short core in accordance with the national standard "Core Analysis Method" (GB / T29172-2012).

[0095] (2) Calculate the number of core samples required. The ground pressure difference is calculated to be 5.7 MPa based on the dew point pressure. Based on the pressure-volume relationship in the PV relationship curve, 11 cores that meet the required pore volume requirements are selected from the candidate cores, including 3 full-diameter cores and 8 short cores. The specific core parameters are shown in Table 1.

[0096] Table 1 Core parameters

[0097]

[0098]

[0099] (3) Calibrate the pore volume of the core in each core holder under the action of confining pressure. First, open all valves that control the confining pressure of the core holder, and allow the pressure generated by the double-cylinder plunger pump 28 to be transmitted to each core holder, and add confining pressure to the overlying rock pressure of the formation. And open all valves 13, 15, 16, etc. of the core holders in series. Evacuate all cores simultaneously from the three-way valves 11 and 17, respectively, until the pressure sensor readings corresponding to all cores are consistent. Then close all valves 13, 15, 16, etc. of the core holders in series, and disconnect the core in each section of the core holder. From the three-way valve 11, inject helium at a constant pressure of 5MPa into the full-diameter core 2, and record the volume V of helium entering the core 2 at a constant pressure. 1 , when the pressure stabilizes, record the pressure P in core 2 1 Then open the three-way valve 13 until the pressure in the core holders 1 and 3 is stable and consistent, and record the equilibrium pressure at this time as P 2 , through the formula V 2 =Z 2 ·P 1 ·V 1 / (Z 1 ·P 2 )-V 1 , calculate the pore volume V of short core 4 2 Then open the three-way valve 15, repeat the above steps and calculation formula, and calculate the core pore volume in the core holder 5. After all the core pore volumes are calculated, stop the calibration experiment. The core pore volume under the confining pressure after calibration is shown in Table 1.

[0100] (4) The full-diameter core 2 is saturated with formation fluid. First, all the cores in series are vacuumed again. The vacuuming method is as described in step (3). Then, the valves of all the cores in series are closed. The three-way valve 11 and the two-way valve 14 are opened, and the full-diameter core (core number 1 in Table 1) is fully saturated with natural gas using a double-cylinder plunger pump 19. The back pressure valve 25 is adjusted by a single-cylinder plunger pump 23 to raise the core pressure to the formation pressure of 32 MPa. Then, the condensate gas is used to displace the natural gas to complete the saturation of the condensate gas. When the output gas-oil ratio measured by the oil-gas separation bottle 24 and the gas meter 26 remains unchanged, the saturation of the condensate gas is completed.

[0101] (5) Determine the dew point pressure of the condensate gas in the core. When the full-diameter core (core No. 1 in Table 1) is saturated with condensate gas, close the three-way valve 11 and the two-way valve 14. Open the three-way valve 13 to allow the condensate gas in the full-diameter core (core No. 1 in Table 1) to diffuse into the short core (core No. 2 in Table 1). When the pressure sensor reading at valve 11 is consistent with the pressure sensor readings at valves 13 and 15, record the pressure at this time. Then open the three-way valve 15 again to allow the condensate gas to diffuse into the core No. 3 again. When the pressure sensor readings at valves 11, 13, 15 and 16 are consistent, record the pressure value. Then repeat the above steps again to allow the condensate gas to diffuse into the next core. The experiment ends when the condensate gas enters the last full-diameter core (core No. 11 in Table 1).

[0102] Experimental results:

[0103] Table 1 shows the relationship between the core pressure and its corresponding cumulative core pore volume (including the corrected volume after deducting the dead volume in the pipeline) during the constant mass expansion of condensate gas. After plotting the core pressure and the core cumulative corrected pore volume in the same coordinate system, we can obtain: Figure 4 The pressure-volume (PV) curve measured in the core is shown in Figure 1, while the other curve represents the PV curve measured in the PVT tube as a reference for comparison. Figure 4 The inflection points of the two different curves in the figure can be obtained by enlarging the two curves separately. Figure 5 (a) and Figure 5 (b). Figure 5 (a) shows the inflection point of the PV relationship curve measured in the PVT cylinder after being enlarged. The pressure corresponding to the inflection point is the dew point pressure of 26.36MPa measured in the PVT cylinder. Figure 5 (b) is the inflection point corresponding to the amplified PVT relationship curve measured in the core. The pressure corresponding to the inflection point is the dew point pressure of 28.23MPa measured in the core. Comparing the two dew point pressures, it is found that the dew point pressure of condensate gas measured in the core is higher than the value measured in the PVT cylinder, indicating that the presence of porous media can increase the dew point pressure of condensate gas by 7.1%.

[0104] On the other hand, based on the above physical property parameter determination system, the embodiment of the present invention further provides a method for determining physical property parameters of porous medium fluid (also called "physical property parameter determination method"). The physical property parameter determination method is implemented using the above-mentioned physical property parameter determination system.

[0105] Figure 6 Schematic diagram of the steps of the method for measuring the physical property parameters of porous medium fluid according to the embodiment of the present application. Figure 6 As shown, the method for determining physical property parameters according to the embodiment of the present invention comprises the following steps:

[0106] Step S601, constructing a core device, the core device comprising at least two first-type core modules and a plurality of second-type core modules connected in series and located between the at least two first-type core modules, wherein the core size of the first-type core module is larger than the core size of the second-type core module;

[0107] Step S602: the confining pressure device provides simulated confining pressure to the core device;

[0108] Step S603, the injection device B connected to the first first-type core module A1 in the core device A injects the first experimental gas during pore volume calibration;

[0109] Step S604, the experiment control device D controls the on-off state of the pipelines between adjacent core modules, and continuously records the equilibrium pressure when the first experiment gas passes through the core modules at different positions in sequence, thereby calibrating the pore volume of each core;

[0110] Step S605, the injection device B injects the second experimental gas and the fluid sample respectively during the constant mass expansion experiment stage;

[0111] Step S606, the experimental control device D controls the fluid sample to saturate the first type of core module, controls the on-off state of the pipeline between adjacent core modules, continuously records the equilibrium pressure when the fluid sample diffuses to the core modules at different positions in turn, and obtains the physical properties of the formation fluid sample in combination with the pore volume of each core.

[0112] The present invention discloses a system and method for measuring the physical property parameters of porous medium fluid. The system and method are mainly composed of a plurality of full-diameter cores and short cores connected in series, and are used to simulate the process of constant mass expansion of formation fluid in a reservoir, and determine the saturation pressure of formation fluid and its related high-pressure physical property parameters by measuring the pressure and corresponding volume of the fluid in the expansion process in the core. Therefore, the present invention can directly measure the relationship between the pressure and corresponding volume of formation fluid in the actual reservoir porous medium during expansion, accurately obtain the high-pressure physical property parameters such as the saturation pressure, deviation coefficient, compression coefficient and volume coefficient of the fluid in the core, clarify the real phase characteristics of the formation fluid in the reservoir porous medium, and provide objective basic parameters for the development plan design, reserve calculation and oil test and production of low-porosity and low-permeability oil and gas reservoirs, which has extremely wide promotion and application value.

[0113] The above is only a preferred specific embodiment of the present invention, but the protection scope of the present invention is not limited thereto. Any changes or substitutions that can be easily thought of by any person familiar with the technology within the technical scope disclosed by the present invention should be included in the protection scope of the present invention. Therefore, the protection scope of the present invention should be based on the protection scope of the claims.

[0114] In the description of the present invention, unless otherwise specified, "plurality" means two or more than two; the orientations or positional relationships indicated by the terms "upper", "lower", "left", "right", "inner", "outer", "front end", "rear end", "head", "tail", etc. are based on the orientations or positional relationships shown in the drawings, and are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operate in a specific orientation, and therefore cannot be understood as limiting the present invention. In addition, the terms "first", "second", "third", etc. are only used for descriptive purposes and cannot be understood as indicating or implying relative importance.

[0115] In the description of the present invention, it should be noted that, unless otherwise clearly specified and limited, the terms "connected" and "connection" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection or an indirect connection through an intermediate medium. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0116] It should be understood that the embodiments disclosed in the present invention are not limited to the specific structures, processing steps or materials disclosed herein, but should be extended to equivalent substitutions of these features understood by ordinary technicians in the relevant field. It should also be understood that the terms used herein are only used for the purpose of describing specific embodiments and are not meant to be limiting.

[0117] The "one embodiment" or "embodiment" mentioned in the specification means that the specific features, structures or characteristics described in conjunction with the embodiment are included in at least one embodiment of the present invention. Therefore, the phrases "one embodiment" or "embodiment" appearing in various places throughout the specification do not necessarily refer to the same embodiment.

[0118] Although the embodiments disclosed in the present invention are as above, the contents described are only embodiments adopted for facilitating the understanding of the present invention and are not intended to limit the present invention. Any technician in the technical field to which the present invention belongs can make any modifications and changes in the form and details of the implementation without departing from the spirit and scope disclosed in the present invention, but the patent protection scope of the present invention shall still be subject to the scope defined in the attached claims.

Claims

1. A system for measuring physical parameters of porous medium fluid, characterized in that: include: A core device, comprising at least two first-type core modules and a plurality of second-type core modules connected in series and located between the at least two first-type core modules, wherein the core size of the first-type core module is larger than the core size of the second-type core module; An injection device, which is used to inject a first experimental gas during pore volume calibration, and to inject a second experimental gas and a fluid sample respectively during a constant mass expansion experiment stage; A confining pressure device, which is used to provide simulated confining pressure to the core device; An experimental control device is used to control the on-off state of pipelines between adjacent core modules, wherein the pore volume of each core is calibrated according to the recorded equilibrium pressure when the first experimental gas passes through the core modules at different positions in sequence, and then, under the condition that the fluid sample is controlled to saturate the first first-type core module, the equilibrium pressure when the fluid sample diffuses to the core modules at different positions in sequence is recorded, and the physical properties of the formation fluid sample are obtained in combination with the pore volume of each core.

2. The system according to claim 1, characterized in that The injection device comprises: A double-cylinder plunger pump, which is used to transmit pressure to the piston container via a pressurized medium; A piston container is used to inject the first experimental gas or the second experimental gas or the fluid sample into the first first-type core module by using the provided pressure power. The first experimental gas is preferably helium and the second experimental gas is preferably natural gas.

3. The system according to claim 1 or 2, characterized in that: The first / second type core module comprises: a first / second type core, a core holder and a core casing. The size range of the first type core is 10 cm in diameter and 3-15 cm in length. The size range of the second type core is 1.8-3.8 cm in diameter and 1-15 cm in length.

4. The system according to claim 3, characterized in that The core casing is a heating casing, wherein the system further comprises: a temperature control device, wherein the temperature control device is used to provide simulated formation temperature to the core device.

5. The system according to any one of claims 1 to 4, characterized in that: The confining pressure device is connected to the core side wall in each core module, and the confining pressure device adopts a double-cylinder plunger pump.

6. The system according to any one of claims 1 to 5, characterized in that: The core modules are connected in series through a high-pressure series pipeline, wherein a corresponding connecting valve is provided at the end of each core module, and a pressure sensor for measuring the equilibrium pressure is provided at each connecting valve, wherein the system also includes a back pressure device hung at the outlet of the first first-type core module.

7. The system according to claim 6, characterized in that The experimental control device carries out the calibration experiment of the core pore volume according to the following steps: Controlling the confining pressure device to apply confining pressure to each core module; Control the connecting valves arranged on the end faces of each core module to open, thereby evacuating all the cores; Controlling the connecting valves for connecting the core modules in series to close; Controlling the injection device to inject the first experimental gas from the inlet of the core device, and recording the volume of the gas injected into the first core and the first equilibrium pressure after the pressure is stabilized; Controlling the connecting valve for connecting the first core block and the second core block to open, and recording the current first equilibrium pressure after the pressure is stabilized, thereby recording the first equilibrium pressure after the pressure is stabilized by sequentially controlling the connecting valves for connecting the core modules in series to open; The pore volume of each core is obtained according to the first equilibrium pressure recorded at different time periods.

8. The system according to claim 7, characterized in that The experimental control device carries out the constant quality expansion experiment according to the following steps: Control the connecting valves arranged on the end faces of each core module to open, thereby evacuating all the cores; Controlling the connecting valves for connecting the core modules in series to close; Controlling the injection device to inject the second experimental gas from the inlet of the core device, and controlling the adjustment of the back pressure device so that the pressure of the first core is raised to a preset formation pressure; Controlling the injection device to inject the fluid sample from the inlet of the core device so that the fluid sample displaces the first core and completes formation fluid saturation; Controlling the valve disposed at the inlet of the core device to close; Controlling the opening of the connecting valve for connecting the first core and the second core to allow the formation fluid in the first core to diffuse to the second core, and recording the current second equilibrium pressure after the pressure is stabilized. Similarly, by sequentially controlling the opening of the connecting valves for the core modules connected in series, the second equilibrium pressures after the pressure is stabilized are recorded respectively. The physical property parameters of the formation fluid sample are calculated according to the second equilibrium pressure at different time periods and the pore volume of each core.

9. The system according to claim 8, characterized in that The physical property parameter includes saturation pressure, wherein the step of calculating the saturation pressure of the formation fluid sample includes: A curve representing the relationship between pressure and pore volume during the core expansion process is drawn, so as to obtain the saturation pressure of the formation fluid sample by identifying the inflection point in the current pressure-pore volume relationship curve.

10. The system according to any one of claims 6 to 9, characterized in that: The length of the high-pressure serial pipeline is 3-5 cm, wherein the pore volume of each core is also deducted from the volume of the high-pressure serial pipeline located at the front end of the corresponding core.

11. The system according to any one of claims 6 to 10, characterized in that: The experimental control device is further used to configure the number of the first type of core modules and the second type of core modules according to the following steps: Conduct PVT phase state experiments on formation fluid samples to determine the dissolved gas-oil ratio of formation fluid in the PVT tube, the saturation pressure and pressure-volume relationship curve based on the PVT experiment, and determine the porosity and permeability of the first type of core samples and the second type of core samples through core analysis methods; According to the PV relationship in the pressure-volume relationship curve where the pressure is greater than the saturation pressure based on the PVT experiment, the corresponding pressure drop value when the formation fluid sample increases the unit core pore volume is calculated, and based on this, the number of the second type of core samples required to reduce the actual formation pressure to the saturation pressure based on the PVT experiment is calculated; The number of the first type of core samples required to reduce the saturation pressure based on the PVT experiment to the final pressure is calculated, wherein the final pressure is the pressure corresponding to three times the initial fluid volume required to saturate the first type of core samples.

12. The system according to any one of claims 6 to 11, characterized in that: The back pressure device comprises: a back pressure pump and a back pressure valve, and the back pressure pump is a single-cylinder plunger pump.

13. The system according to claim 8, characterized in that The system also includes an oil and gas recovery device hung at the outlet of the first first-type core module, and the oil and gas recovery device includes an oil and gas separation bottle and a gas meter, wherein the experimental control device is also used to obtain gas-oil ratio data from the oil and gas recovery device, and determine the timing of completing formation fluid saturation based on the changing state of the gas-oil ratio data.

14. A method for measuring physical property parameters of porous medium fluid, characterized in that: The method is implemented using a system according to any one of claims 1 to 13, wherein the method comprises: Constructing a core device, the core device comprising at least two first-type core modules and a plurality of second-type core modules connected in series and located between the at least two first-type core modules, wherein the core size of the first-type core module is larger than the core size of the second-type core module; The confining pressure device provides simulated confining pressure to the core device; injecting a first experimental gas by an injection device during pore volume calibration; The experimental control device controls the on-off state of the pipelines between adjacent core modules, and continuously records the equilibrium pressure when the first experimental gas passes through the core modules at different positions in sequence, thereby calibrating the pore volume of each core; The injection device injects the second experimental gas and the fluid sample respectively during the constant mass expansion experiment stage; The experimental control device controls the fluid sample to saturate the first type of core module, and by controlling the on-off state of the pipeline between adjacent core modules, continuously records the equilibrium pressure when the fluid sample diffuses to the core modules at different positions in sequence, and obtains the physical properties of the formation fluid sample in combination with the pore volume of each core.

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