JP6782290B2 - Measuring device and measuring method for structural change of pelitic silt reservoir structure in sea area by CT technology - Google Patents

Description

The present invention relates to the geological field, and more particularly to an apparatus capable of measuring the process of movement of pelitic silt porous medium fine particles in a sea area storing natural gas hydrate by a substitution medium by CT.

The muddy silt reservoir in the sea area that stores natural gas hydrate is not consolidated, has a low penetration rate, has a large detour rate in the structural space of the pore throat, and has a small coordination number. It has multiple features of. Submarine pelitic silt deposits in common natural gas hydrate reservoirs have a median diameter of 2.60-28.96 μm and an average median diameter of 12 μm, mainly siliceous (53%) and carbonate minerals. It is composed of (16%) and clay minerals (26% -30%), and the clay minerals mainly composed of montmorillonite and illite have a high content and an immobile water saturation rate of more than 65%. To varying degrees, very fine particles are present in the reservoir as disjointed particles on the pore wall or the inner surface of the particles, and the pores become narrower as the fluid moves in the porous medium (throat). Aggregates in, causing clogging and significantly reducing the permeability of the reservoir, although the magnitude of permeability directly determines the daily output level of the single well.

However, due to the framework-free nature of the pelitic silt reservoir, conventional core holders used in industry laboratories cannot fill such samples, and the reservoir Since the particle size of the porous medium particles in the layer is extremely small, it is not possible to effectively observe the particle distribution after the movement of the muddy silt fine particles by the conventional experimental method, and experiments on the flow velocity sensitivity of the porous medium are conducted. Effectively performing and understanding and understanding the permeation characteristics and the law of change in permeation rate of multiphase fluids in silts has become a major issue.

Therefore, by researching and developing a measuring device that can observe the migration process in the pelitic silt reservoir, we tried an experiment to measure the displacement of fine particles in a hydrated porous medium in the sea area, and under different substitution pressures and fluid flow rate conditions. It is possible to grasp information on the movement law of fine particles in a porous medium, the process of change in microstructure, and the characteristic of change in permeability.

An object of the present invention is to provide an apparatus capable of measuring the movement process of fine particles of muddy silt porous medium in a sea area under a replacement medium by CT.

In particular, the present invention provides a measuring device for structural changes in the pelitic silt reservoir structure in the sea area by CT technology.
A hollow transparent reaction tube made of a non-magnetic material and a chock plug that seals the openings at both ends of the reaction tube are included, and a through hole communicating with the inside of the reaction tube is provided in the chock plug to provide the volume of the reaction tube. With a holder that can be stored at least in the detection space of the CT device,
A supply device for accommodating a replacement medium for test samples,
A connector that connects the supply device and the chock plug at one end and controls the replacement medium so as to enter the reaction tube.
A measuring device connected to the chock plug at the other end and measuring the amount of replacement medium discharged from the reaction tube,
A CT apparatus having a detection space for scanning the holder and acquiring a change state diagram of the sample as the replacement medium passes through the sample in the reaction tube.
It is equipped with a control system that acquires data in the measurement process, analyzes the measurement data in real time, and at the same time outputs the corresponding measurement results.

In one embodiment of the invention, the chock plug includes a hollow medium joint and a metal seal tube, the medium joint includes a limiting portion and an introduction portion integrally formed of a non-magnetic material, and the outer diameter of the limiting portion is It is equal to or less than the inner diameter of the reaction tube, the diameter of the introduction portion is larger than the outer diameter of the reaction tube, the restriction portion is inserted into the inside of the reaction tube and then blocked by the introduction portion, and the metal seal tube is formed. It is attached so as to seal the connection between the reaction tube and the introduction portion, the through hole is installed in the introduction portion, and the distance between the two limiting portions is a space for accommodating the measurement sample.

In one embodiment of the present invention, ring-shaped concave rings for attaching male screws and seal rings are installed at both ends of the reaction tube, and the metal seal tube is screwed into the reaction tube at one end facing the restriction portion. The female screw to be used is installed, the other end is a sliding channel whose diameter is smaller than the diameter of the female screw portion, and a limiting ring projecting outward is installed at an end close to the limiting portion of the introduction portion, and the medium. The metal seal tube installed in the joint is restricted by the restriction ring and cannot slide in the direction of the restriction portion, and at the same time, the introduction portion has a C-shaped retainer that restricts the retreat of the metal seal tube. Will be installed.
In one embodiment of the present invention, a non-magnetic adjusting tube for adjusting the size of the space is attached in the space for accommodating the sample, and the outer diameter of the adjusting tube is equal to or less than the inner diameter of the reaction tube and is inside. A channel through which the replacement medium passes is installed, and a flow guide groove for diversion of the replacement medium is installed on the contact end face between the adjusting tube and the sample.

In one embodiment of the invention, the reaction tube, medium joint and adjustment tube are made of non-magnetic polyimide material.

In one embodiment of the present invention, a diametrical seal ring is installed on the outer circumference of one end near the housed sample of the restricted portion.

In one embodiment of the present invention, a metal net and a filter paper that suppress the passage of the sample are installed at one end of each of the two restricted portions near the sample, and the mesh of the metal net and the filter paper is at least smaller than the particle size of the sample.

In one embodiment of the invention, the measuring device includes an electronic balance and a container for containing the discharged replacement medium, the chock plug is connected to the container via piping.

In one embodiment of the invention, the supply device comprises a material storage tank for providing gas or liquid, a regulator for adjusting the supply pressure of the material storage tank, and a liquid tank for accommodating a replacement medium. The supply end is connected to the regulator, the discharge end is connected to the connector, and the regulator adjusts the gas or liquid discharged by the supply device to enter the liquid tank based on the required measurement pressure. , The replacement medium in the liquid tank is facilitated to enter the reaction tube after passing through the connector, and the connector is provided with two supply interfaces and one shared discharge interface connected to the gas source and the liquid source, respectively. At the same time, the current supply amount and pressure value of the replacement medium are output to the control system via the circuit.

In one embodiment of the present invention, a fixed base is attached to one end away from the restricted portion of the introduction portion of the medium joint, and a storage groove for accommodating the mounting sheet of the CT device is provided on the bottom surface of the fixed base. An adjusting screw twisted in the axial direction is installed around the radial direction of the fixed base to fix the fixed base and the above-mentioned mounting sheet.

In one embodiment of the invention, a corresponding amount of sample is selected according to the requirements of the test, then placed in a small reaction tube made of non-magnetic material, and the placement position of the sample is adjusted with the chock plugs at both ends. And then the test devices are connected so that the reaction tube is located in the detection space of the CT device.
First, the control system acquires each initial data before measurement, selects the test pressure and test flow rate, then opens the liquid tank and injects distilled water at a predetermined flow rate into the reaction tube under the set pressure, and the measuring device In step 200, the amount of distilled water discharged after the sample has passed is recorded, and the permeation rate when the sample of distilled water is passed is calculated based on the amount of distilled water discharged per unit time.
When the flow velocity of the distilled water received by the measuring device stabilizes, the experiment is temporarily stopped to keep the current state in the reaction tube stationary, and then the sample in the reaction tube is sampled by the CT device using the radiation source. Step 300 of scanning at 360 degrees, acquiring and saving the image of the sample scanned this time, and then continuing the experiment.
As the experiments continue, the current test pressures are changed, steps 200 and 300 are repeated until a predetermined number of experiments, then data summarization is performed on the images acquired for each scan, and the pressures of the current samples are different. Structural changes in the marine mud silt reservoir, including step 400, which captures the movement of fine particles at flow rates and thereby provides conditions to be met when actually mining natural gas hydrates in the corresponding geological formations. Provided is a measuring method of an apparatus for measuring.

In one embodiment of the invention, the criteria for changing the current test pressure changes based on changes in the pressure gradient, specifically, the initial test pressure is 10 kpa, and the test pressure in each subsequent experiment is sequential. It is 30 kPa, 50 kPa, 75 kPa, 100 kPa.

In one embodiment of the invention, the sample is filled into the reaction tube so that it is in close contact with the inner wall surface of the reaction tube so that distilled water does not flow through both contact sites during the experiment.

In one embodiment of the present invention, as for the movement of fine particles at different pressures and flow rates of the current sample, the rock reservoir sample composed of pelitic silt has a higher penetration rate as the replacement time increases. Deterioration occurs at each replacement point in time, eventually forming a cake that increases permeation resistance around the wells, increasing the time required to stabilize production in the low pressure section and significantly reducing geological energy in the high pressure section. It has the property of having a tendency to.

In one embodiment of the present invention, when calculating the permeation rate, the current flow velocity is first measured, and then the permeation rate is obtained by the following formula.

(In the formula, ΔP is the pressure difference, Q is the flow velocity, μ is the viscosity of the injection solution, l is the core length, A is the cross-sectional area of the core, and K is the permeation rate.)

According to the present invention, the holder can be miniaturized and the reaction tube can be manufactured from a non-magnetic material to satisfy the observation requirements at the time of the experiment, and the sample can be moved at different pressures by being mounted on a CT device and scanned. From conventional methods that capture images of the situation, provide strong support on what parameters to adopt to mine natural gas hydrate under the formation, and estimate mining results based solely on theory. Is also clear and certain.

It is a connection schematic diagram of the measuring apparatus by one Embodiment of this invention. It is a concrete structural schematic diagram of the holder in FIG. It is a schematic diagram of the CT image at different pressures in the experimental process of a sample according to one embodiment of the present invention. It is a schematic diagram of the process of the measurement method by one Embodiment of this invention. It is a flow velocity analysis chart at the time of experiment of the sample by one Embodiment of this invention. It is a penetration rate analysis figure at the time of experiment of the sample by one Embodiment of this invention. It is a schematic diagram of a non-Darky penetration curve. It is a schematic diagram of the infiltration curve of the hydrated mud silt reservoir in the northern part of the South Sea.

As shown in FIG. 1, the measuring device for the structural change of the muddy silt reservoir in the sea area by the CT technique according to the embodiment of the present invention is generally a holder 10, a supply device 30, a connector 40, a measuring device 50, and the like. It includes a CT device 60 and a control system 20.

The holder 10 includes a hollow transparent reaction tube 11 made of a non-magnetic material and a chock plug 12 that seals the openings at both ends of the reaction tube 11, and the chock plug 12 communicates with the inside of the reaction tube 11. A through hole is installed. The transparency of the reaction tube 11 makes it easy to observe the placement position of the sample inside and the adjustment scanning point, and by using a non-magnetic material, the detected radiation of the CT device 60 is passed through, and finally a clear image is obtained. Can be formed. One purpose of this proposal is to observe the movement of the sample, and in order to achieve such a purpose, a high-precision CT machine (for example, a resolution satisfying 0.5 μm accuracy) is used instead of a low-resolution CT machine. ) Is required, and the conventional high-precision CT machine has a detection space for accommodating a sample, and the volume of the reaction tube 11 is limited by the space. Therefore, in this embodiment, the reaction tube 11 The volume meets at least the requirements of the detection space of the CT device. Specifically, polyimide can be used as a non-magnetic material.

The supply device 30 is for accommodating a replacement medium for a test sample, for example, a gas tank 31 accommodating a gas and / or a liquid tank 32 accommodating a liquid, and when conducting an experiment, a specific experimental requirement is met. Correspondingly, the corresponding gas tank 31 or liquid tank 32 can be used.

The connector 40 is an adapter, plays a role of adjusting the supply pressure and the supply digital information, and is connected to the gas tank 31 and the liquid tank 32 of the supply device 30 by the corresponding connection joints, and at the same time in the reaction tube 11 by the discharge joint. It is connected to the chock plug 12 at one end where the replacement medium enters. After deciding to use gas or liquid as the replacement medium, the changeover switch switches the connection joint so that it communicates with the discharge joint.

The measuring device 50 is used to measure the amount of replacement medium discharged after passing through the sample in the reaction tube 11, and calculates the flow velocity of the replacement medium at the current pressure. The measuring device 50 may be a measuring instrument for calculating the passing amount in a unit time, or may be a weight measuring instrument for measuring the weight of the discharged amount. An electronic balance 51 is used as the measuring device in the present embodiment, and the electronic balance 51 has a container 52 capable of accommodating the discharged replacement medium and one end communicating with the discharged replacement medium of the reaction tube 11 and the other end being a container. Place a connecting pipe that extends within 52.

The CT device 60 is not involved in the experimental process, is operated independently in the steps of the experimental process, has a detection space in which radiation is installed and stores the holder 10, and the placed holder 10 is placed at 360 degrees. By scanning, a phase diagram can be generated as the replacement medium in the reaction tube 11 passes through the sample. Specifically, as the CT apparatus 60, a conventional high-precision CT, for example, a Sanying Micro-CT can be used.

The control system 20 serves as an experimental core, has a function of receiving experimental data before measurement and each data during the experimental process, and analyzes in real time on the basis of the data acquisition to provide a corresponding analysis form, curve diagram, etc. Can provide results. An industrial computer or a PC computer can be used.

In the present embodiment, when conducting an experiment, first, the sealability of the holder 10, the chock plug 12, and each pipeline system is detected, and then the holder 10 is attached. That is, first, the chock plug 12 at one end of the reaction tube 11 is attached, and then the muddy silt formation sample is divided into a plurality of times until the sample completely fills the sample accommodating area of a predetermined length in the reaction tube 11. The sample and the inner wall surface of the reaction tube 11 are brought into close contact with each other so as to prevent the subsequent substitution medium from flowing through the contact surface and affecting the passage effect in the sample. Finally, the chock plug 12 at the other end of the reaction tube 11 is attached.

2. In this embodiment, since distilled water is used as a replacement medium, data for sequentially connecting the liquid tank 32 and the connector 40, the connector 40 and the reaction tube 11, the reaction tube 11 and the measuring device 50, and collecting information on each device at the same time. The line and the control system 20 are connected.

Third, the connector 40 is closed, the liquid pump 32 is opened, and the supply pressure of the liquid pump 32 is adjusted to stabilize the pressure required for the experiment.

4. The control system 20 records the initial weight of the container 52 in the electronic balance 51, sets the sampling interval of the system, opens the switch of the discharge joint of the connector 40, and the distilled water passes through the chock plug 12 and the reaction tube 11 Distilled water enters the sample and is discharged from the chock plug 12 at the other end to the container 52 of the measuring device 50. In that process, the control system 20 records the volume of increased fluid in the vessel 52, calculates the volume of increased flow rate in the vessel at the sampling interval time, and the flow rate of distilled water that has passed through the sample at that interval time. To get.

Fifth, CT has two types of scanning methods. 1. 1. The reaction tube after connection is directly located in the detection space of the CT apparatus 60, and then the experiment is normally performed, and the direct scanning is performed when scanning is performed in the experimental process. 2. Since the reaction tube is not located in the detection space of the CT device 60, when scanning is to be performed, the piping at both ends of the reaction tube is sealed and removed, and the CT device 60 is detected while maintaining the basic state of the reaction tube. The scan is performed in a space, and after the scan is completed, the piping is reconnected to the reaction tube to continue the experiment.

With either mounting method, the following must be met before scanning: When the set pressure is kept constant, scanning can be performed only when the flow velocity of distilled water does not change. Taking the case where the reaction tube is removed and scanning is performed independently, first, the chock plugs 12 at both ends of the reaction tube 11 are sealed, the connecting pipe is removed, and the internal state of the reaction tube 11 is maintained. The reaction tube 11 is removed and transferred to the three-dimensional motion detection platform in the CT apparatus 60, the radiation source is adjusted, the data acquisition software is activated, and each scanning parameter is adjusted to obtain a steady state of the sample structure in the reaction tube 11. When it stops changing, a 360 degree scan of the reaction tube is initiated.

6. After scanning is complete, the reaction tube 11 is removed from the inside of the CT device and reconnected to the measurement system, the test pressure and / or flow rate is adjusted, and steps are taken until the experimental process at a predetermined different test pressure is completed. 4. Repeat step 5 to carry out the experiment.

Seven, CT scanning is performed for each test pressure, the primitive state of the core before the start of the experiment is also scanned, reconstruction is performed for each scanning data, and a three-dimensional reconstructed image of each sample is acquired. Organize all three-dimensional reconstructed images, create analytical maps, tables, and reports based on experimental data, and finally get them under different mining conditions when actually mining the formation where the sample is currently located. Acquire the mining result data that can be done.

FIG. 3 is a comparative schematic diagram of CT scanned images in each process from the primitive state of the internal reservoir structure at different test pressures of the selected sample to the passage of a series of pressures, and the first line is an actual experiment. Schematic diagram of 3D state at the time of operation, the second row is a schematic cross-sectional view of the same position of the reservoir structure corresponding to the first row, and the third row is the axial direction of the same position of the reservoir structure corresponding to the first row. It is a cross-sectional schematic diagram.

In the present embodiment, as a result of conducting an experiment using the above apparatus, since the sample of the muddy silt reservoir itself does not have a framework, the deformation is more severe than that of the core with the framework, and as the replacement time increases, At the time of each replacement, the sample penetration rate deteriorates, the cake finally becomes a cake, and the cake is becoming thicker, the internal gap structure gradually disappears, the penetration resistance around the well increases due to the formation of the cake, and the low pressure section If it is not preferable, the production pressure difference must be continuously increased in order to improve the flow rate, and the production output drops sharply as the pressure difference is increased. Invite risk. Due to the severe deformation of the reservoir and the tendency for geological energy to decrease significantly in the high pressure region, it may not be possible to increase production even with increased pressure.

As mentioned above, in the submarine silt silt reservoir of natural gas hydrate, the pressure gradient for developing hydrate is greater than 3-5 MPa / m (corresponding experimental parameter is 30-50 kpa / cm). , The gap structure of the porous medium of the mud silt reservoir is greatly deformed, and the velocity sensitivity phenomenon of the reservoir becomes serious. As a result, the permeability of the reservoir drops sharply, which adversely affects the gas output. And the movement of silt granules forms a "cake" structure that adversely affects gas production in the well region.

In the present embodiment, the holder is downsized and the reaction tube is manufactured of a non-magnetic material to satisfy the observation requirements at the time of the experiment, and the sample can be mounted on a CT device for scanning, so that the sample can be sampled at different pressures. A prior art method that takes images of movements, provides strong support for what parameters are used to mine natural gas hydrates beneath the formation, and estimates mining results based solely on theory. Clearer and more reliable than.

As shown in FIG. 2, in one embodiment of the present invention, the chock plug 12 includes a erected hollow medium joint 122 and a metal seal tube 121, the medium joint 122 being a port of a closed reaction tube 11. The limiting portion 1222 inserted inside the reaction tube 11 and the introducing portion 1221 for connecting to and introducing the replacement medium are included, and the outer diameter of the limiting portion 1222 is the reaction tube 11. It is equal to or less than the inner diameter, the diameter of the introduction portion 1221 is larger than the outer diameter of the reaction tube 11, and the limiting portion 1222 is blocked by the introduction portion 1221 after being inserted into the inside of the reaction tube 11. The metal seal tube 121 is installed at the connection portion between the reaction tube 11 and the introduction portion 1222 to increase the connection strength between the reaction tube 11 and the medium joint 122 to avoid disconnection or leakage of both under high pressure. A corresponding seal ring can be installed between the metal seal tube 121 and the medium joint 122. Similarly, a corresponding seal ring 125 can be installed on the outer circumference of the limiting portion 1222 to further prevent leakage on both contact surfaces after the limiting portion 1222 has been inserted into the reaction tube 11.

The through hole 124 connected to the supply line of the replacement medium may be installed in the introduction portion 1221 and may be installed on the circumference of the introduction portion 1221 or at the end of the introduction portion 1221. The joint of the supply line may be a male thread joint for stable screwing. The length of the limiting portion 1222 in the two chock plugs 12 can be determined according to the storage capacity of the sample, that is, the distance between the two limiting portions 1222 is the space 15 for accommodating the measurement sample, and thus the limiting portion 1222. The storage capacity of the sample can be adjusted by adjusting the length.

In order to prevent the limiting portion 1222 inserted inside the reaction tube 11 from affecting the CT scanning effect, the limiting portion 1222 is integrally formed with the introduction portion 1221 and is also manufactured of a non-magnetic material, and is specifically manufactured. The non-magnetic material may be polyimide.

Further, in order to improve the connection strength between the reaction tube 11 and the metal seal tube 12, male screws 111 and ring-shaped concave rings for attaching the seal rings are installed at both ends of the reaction tube 11. A female threaded portion screwed into the reaction tube 11 is installed at one end of the metal seal tube 121 facing the restricted portion 1222, and the other end of the metal seal tube 121 is a sliding channel whose diameter is smaller than the diameter of the female threaded portion. A limiting ring 1223 protruding outward is installed at an end close to the limiting portion 1222 of the introduction portion 1221 of the medium joint 122, and the metal seal tube 121 uses a female threaded portion when installed in the medium joint 122. The limiting ring 1223 is screwed into the end of the reaction tube 11 and limits the metal seal tube 121 so that it cannot slide in the direction of the limiting portion 1222, whereby the metal seal tube 121 is restricted to the reaction tube 11. A larger screwing force can be applied. In order to prevent the inserted metal seal tube 121 from coming off in the erection direction, a C-shaped retainer that limits the retreat of the metal seal tube may be attached to the introduction portion 122.

Further, the size of the sample storage space may be adjusted by installing an adjustment tube in the space 15 for storing the sample of the reaction tube 11, and the adjustment tube (not shown) has a channel installed at the axis. It has a tubular structure, the outer diameter is less than or equal to the inner diameter of the reaction tube 11, a channel for the replacement medium to pass through is installed inside, and the required sample amount is from the space 15 between the two limiting regions 1222. If it is small, an adjusting tube having a length corresponding to one end or both ends of the space 15 can be placed to reduce the volume of the space 15. As the replacement medium flows into space 15, it enters the sample via a channel in the regulating tube. The adjusting pipe can not only adjust the size of the space 15, but also control the flow rate by adjusting the diameter of the channel.

Further, in order to prevent the replacement medium from directly entering the contact point with the sample after being discharged from the adjustment tube, a flow guide groove for dividing the replacement medium is provided at one end face of the adjustment tube in contact with the sample. May be good. When the replacement medium is discharged from the channel of the regulating tube, it first flows along the guide groove and then enters the contacted sample, and such a structure makes the replacement medium in the sample more uniform. Therefore, more accurate movement results can be obtained. Specifically, the flow guide groove may be a ring-shaped concave groove centered on a channel, and each ring-shaped concave groove communicates with each other via a radial channel, so that the replacement medium can be rapidly used. Moreover, it can flow uniformly over the entire end face.

Similarly, the adjusting tube is also made of a non-magnetic polyimide material.

In one embodiment of the present invention, in order to prevent the sample from entering the medium joint 122, a filter paper (not shown) for blocking the passage of the sample is installed at one end of each of the two limiting portions 1222 near the sample. The mesh of the filter paper may be at least smaller than the particle size of the sample, but does not affect the passage of the replacement medium. When arranging, the filter paper is first placed on the end face of the restricted portion 1222 into which one end is inserted, then the sample is filled, and after the sample filling is completed, the filter paper at one end is placed again, and then the restricted portion at this one end. Install 1222. Also, when attaching the adjustment tube, similarly place the corresponding filter paper between the adjustment tube and the sample.

In one embodiment of the invention, the supply device 30 further connects the storage tanks 31 and 32, which provide driving power for gas and liquid, and the two storage tanks 31 and 32, respectively, to supply pressure of the storage tanks 31 and 32. The regulator 34 for adjusting the pressure and the medium tank 33 containing the replacement medium may be installed. In the medium tank 33, the supply end is connected to the regulator 34 and the discharge end is connected to the connector 40.

In this embodiment, the medium in the storage tanks 31 and 32 is used as a power source for driving the replacement medium, that is, the replacement medium is driven by using a dedicated drive source instead of using the pressure of the replacement medium itself as the drive source. Since the storage tanks 31 and 32 output pressure when opened and the medium tank 33 itself does not have any supply pressure, the magnitude of the applied pressure of the storage tanks 31 and 32 becomes the magnitude of the supply pressure of the medium tank 33. Equivalent to. The regulator 34 can request the medium tank 33 to supply gas or liquid at a specified pressure for the adjusted storage tanks 31 and 32 according to the measured pressure, and the replacement medium in the medium tank 33 passes through the connector 40. Promotes entry into reaction tube 11.

In this process, the regulator 34 can visually control the supply pressure, the connector 40 can adjust the supply pressure more accurately, and at the same time, the current analog pressure signal is converted into an electronic signal and output to the control system 20. Let the control system 20 perform the processing directly.

In one embodiment of the present invention, in order to easily attach the holder 10 to the inside of the CT device 60, a fixed base 14 is attached to one end of the introduction portion of the medium joint 122 away from the limiting portion 1222, and the fixed base 14 is attached. A storage groove for accommodating the mounting sheet of the CT device 60 may be installed on the bottom surface, and at the same time, an adjusting screw twisted in the axial direction may be installed around the radial direction of the fixed base 14. When the holder 11 is stored in the storage space of the CT device 60, the fixed base 14 can be locked to the mounting sheet in the storage space, and then the fixed base 14 is stably fixed to the mounting sheet by the adjusting screw. The entire holder 11 rotates 360 degrees together with the mounting sheet to support the acquisition of a complete scanned image by CT scanning.

As shown in FIG. 4, in one embodiment of the present invention, a measuring method for measuring a sample using the above-mentioned measuring device is provided, and specifically, such a member is the same as described above. Since it is only necessary to refer to the members and the reference numerals, detailed description of the structure will be omitted here, and only the corresponding effects of each member will be described. The substitution medium used in this embodiment is a liquid, specifically distilled water. When a gas is used as a replacement medium, the experimental equipment is the same, but the data to be collected when performing the experiment needs to be adjusted accordingly.

The specific steps are as follows.
For step 100, select the corresponding amount of sample according to the test requirements, then place it in a small reaction tube made of non-magnetic material, and adjust the placement position of the sample with the chock plugs at both ends to limit it. Then connect each test device.

Here, as a sample, it is possible to use an actual muddy silt raw material taken directly from the corresponding stratum, which has been subjected to the corresponding heat dehumidification treatment. The amount of sample affects the passage time and the amount of passage of distilled water, and in general, the larger the sample thickness (that is, the distance through which the distilled water passes), the longer the permeation time in the experiment. The corresponding sample amount can be determined according to the experiment time.

When placing the sample, it must be consolidated in lots and compacted with each filling, while at the same time being in full contact with the inner sidewall of the reaction tube to prevent distilled water from passing directly through the sidewalls. ..

The specific sample amount can be limited by the length of the limiting area in the chock plug, and if the required sample amount is less than the distance between the two limiting areas, the mounting space can be reduced by arranging the adjusting tube. ..
Since it is necessary to avoid leakage at the connection and disconnection under pressure after the connection between the chock plug and the reaction tube and the connection between the devices, a screw connection structure can be used as much as possible.
For step 200, the control system first acquires each initial data before measurement, selects the test pressure and test flow rate, then opens the liquid tank and fills the reaction tube with distilled water at a predetermined flow rate under the set pressure. Inject, record the amount of distilled water discharged after the sample has passed in the measuring device, and calculate the flow velocity after passing the sample of distilled water based on the amount of distilled water discharged per unit time.

Prior to the experiment, it is necessary to completely remove the water in the pipeline, at the same time record each basic data and select the initial test pressure and the corresponding test flow rate based on normal mining experience. After the start of the experiment, distilled water enters the sample under test pressure, penetrates the sample through the gaps in the sample, and then is injected into the container on the measurement balance.
The average flow velocity of distilled water during this period may be calculated from the length of time and the total amount of distilled water.

Regarding step 300, when the flow velocity of the distilled water received by the measuring device becomes stable, the chock plugs at both ends of the reaction tube are sealed, and the reaction tube is used as the detection space of the CT device while maintaining the current state in the reaction tube. When the sample is moved to and allowed to stand until the structure of the sample does not change, the sample in the reaction tube is scanned at 360 degrees using a radiation source, the sample image scanned this time is acquired and saved, and then the reaction tube is taken out. And connect again.
As the distilled water passes through the sample, it drives and moves the fine particles of the corresponding sample, thereby changing the existing gap, but after a predetermined time, the new gap state is temporarily fixed. This can be confirmed from the stable flow rate of distilled water discharged.
The removed holder has an independent switch valve installed in the chock plug or the pipeline connected corresponding to the chock plug, and when CT scanning is required, the internal state can be changed by directly closing the switch valves at both ends. It may be held stably.

When performing CT scanning, scanning may be performed only on the holder. Further, since the CT scan is a static scan, it is necessary to leave the newly removed holder for a while and perform the CT scan after the internal flow phenomenon becomes stable.

The CT scanning process is performed entirely in the system of the CT device itself, including controlling the clamp tube to rotate 360 degrees in the radial direction, storing images for each angle, and late compositing of the scanned images. .. In this embodiment, a high-precision CT apparatus capable of observing the movement of fine particles on a micron scale and the corresponding gaps formed is used.

For step 400, changing the current test pressure, steps 200 and 300 are repeated until a predetermined number of experiments are reached, then data summarization is performed on the images acquired for each scan, and the pressures of the current samples are different. And the movement of fine particles at the flow rate is obtained, thereby providing the conditions to be met when actually mining natural gas hydrate in the corresponding formation.

A stable flow process can be obtained with one test pressure, but different test pressures have different effects on the movement of fine particles, so this method selectively tests multiple pressures during normal mining. It will be. Specifically, the test pressure can be selected based on the change in the pressure gradient. In the present embodiment, the initial test pressure is 10 kpa, and the test pressures of each subsequent experiment are sequentially 30 kPa, 50 kPa, 75 kPa, and 100 kPa. The entire test process ends when the test at all test pressures is complete.

At the time of analysis, an integrated analysis is performed based on the sample CT three-dimensional image acquired for each test pressure, and finally displayed in a table or graph that is easy to see.

In this method, as a result of osmotic sensitivity experiment of the porous medium of the reservoir by the stepwise pressure boosting method, the sample of the pelitic silt rock reservoir itself has no framework, so it is deformed compared to the core with the framework. Violently, as the replacement time increased, the permeation rate deteriorated at each replacement point, and finally the cake became thicker, and the permeation resistance around the wells increased due to the formation of the cake, and the yield in the low pressure section. The time required for stabilization becomes longer, and in such a state, there is no choice but to continuously increase the production pressure difference in order to improve the output, but the output drops sharply as the pressure difference increases. We have come to the conclusion that due to the risk and the severe deformation of the reservoir, the geological energy tends to decrease significantly in the high pressure region, and it may not be possible to increase the production even if the pressure is increased.

FIG. 5 is a schematic diagram of the permeation rate change of a sample of a certain parameter with an increasing pressure gradient.

FIG. 6 is a schematic diagram of the permeation rate change of a sample of a certain parameter with an increasing pressure gradient.

In the experiments shown in FIGS. 5 and 6, the sample amount is 6.6 g, the length to be inserted into the holder is 10 mm, the sample diameter is 8 mm, the porosity is 18.6%, and the experimental temperature is 25 ° C.

According to the classical Darky law, the permeation velocity and the pressure gradient have a linear relationship through the origin, and as long as the permeation process deviates from such a linear relationship as shown in FIG. 7, it is "non-Darchy". It is called "penetration". As is clear from the flow velocity sensitivity experiments by the stepwise boosting method of this method, as shown in FIG. 8, the hydrated muddy silt reservoir in the northern part of the South Sea has the above-mentioned classic "non-Darchy" type infiltration curve. Unlike, there is a tendency for the lower limit "non-Darchy" infiltration to deviate from the origin and have a starting pressure and the infiltration rate is significantly too low.

In the present embodiment, the calculated flow velocity is obtained by the equation of the substitution pressure difference, and the equation of the substitution pressure difference is as follows.

After passing, you get:

(In the formula, ΔP is the pressure difference, Q is the flow velocity, μ is the viscosity of the injection solution (1 · mPa · s), l is the core length, A is the cross-sectional area of the core, and K is the permeation rate.)
At the same time that the fluid phase changes continuously like "solid-gas + liquid", the porous medium itself of the muddy silt reservoir also undergoes plastic deformation, and as a result, the entire pore structure tends to reconstruct. Have. Due to the decrease in the pore pressure of the porous medium, the elastic expansion and porosity of the gas and rock decrease, and the gas is discharged from the pores by the action of expansion energy and enters the bottom of the well, and the porosity and permeation of the porous medium. The rate etc. is a function of pressure as follows.

(In the formula, φ is the porosity, P is the pressure, and k is the permeation rate.) The "weak compressible hypothesis" is applied to the conventional non-stationary flow theory, and the following conditions are required for the porous medium.

(In the formula, φ is the porosity, P is the pressure, k is the permeation rate, and Cφ is the porosity compression coefficient.) Unlike the above, the pelitic silt reservoir has a large elastic energy of underground rock and a large expansion energy of gas, so the role played in the infiltration process cannot be ignored, and the "weak compressibility hypothesis" is such a reservoir. Since it cannot be applied to oil and gas development applications in Japan and the plastic deformation of the porous medium is serious, it becomes more difficult to determine the permeability of the reservoir.

After understanding and understanding the information in two directions of the relationship between the permeability sensitivity of the target layer and the flow velocity and pressure gradient, not only the starting pressure gradient exists in the porous medium for exploring the target layer, but also. It has been found that there is a serious lower bound "non-Dracy" osmotic phenomenon-ie, there is a non-linear relationship between flow rate (flow velocity) and pressure gradient.

According to mechanical analysis, the pore structure of the porous medium deforms with changes in pressure gradient and time, the flow velocity sensitivity of the reservoir becomes more serious, the permeability of the reservoir drops sharply, and the flow rate. Has been found to have a clear tendency to decrease, which belongs to the "atypical" "non-Dracy unsteady flow".

To date, those skilled in the art have described in detail a plurality of exemplary embodiments of the invention, but are disclosed in the invention without departing from the spirit and scope of the invention. Based on the content, a plurality of modifications or modifications consistent with the principles of the present invention can be directly conceived or presumed. Therefore, the scope of the invention should be understood and recognized as including all such other modifications or modifications.

Claims (15)

It is a measuring device for structural changes in the pelitic silt reservoir structure in the sea area by CT technology.
A hollow transparent reaction tube made of a non-magnetic material and a chock plug that seals the openings at both ends of the reaction tube are included, and a through hole communicating with the inside of the reaction tube is provided in the chock plug to provide the volume of the reaction tube. With a holder that can be stored at least in the detection space of the CT device,
A supply device for accommodating a replacement medium for test samples,
A connector that connects the supply device and the chock plug at one end and controls the replacement medium so as to enter the reaction tube.
A measuring device connected to the chock plug at the other end and measuring the amount of replacement medium discharged from the reaction tube,
A CT apparatus having a detection space for scanning the holder and acquiring a change state diagram of the sample as the replacement medium passes through the sample in the reaction tube.
Equipped with a control system that acquires data in the measurement process, analyzes the measurement data in real time, and at the same time outputs the corresponding measurement results.
The chock plug includes a hollow medium joint and a metal seal tube, the medium joint includes a limiting portion and an introduction portion integrally formed of a non-magnetic material, and the outer diameter of the limiting portion is equal to or less than the inner diameter of the reaction tube. The diameter of the introduction portion is larger than the outer diameter of the reaction tube, and the restriction portion is blocked by the introduction portion after being inserted into the inside of the reaction tube. A device for measuring changes in silt reservoir structure. Is the previous SL-metal seal tube fitted to seal the connection portion between the introduction portion and the reaction tube, the through hole is disposed on the introducing portion, the spacing distance between two of said restricted portions have a measurement sample The device according to claim 1, wherein the space is to be accommodated. Ring-shaped concave rings for attaching male screws and seal rings are installed at both ends of the reaction tube, and the metal seal tube has female screws screwed into the reaction tube at one end facing the restriction portion. The other end is a sliding channel whose diameter is smaller than the diameter of the female thread portion, and a limiting ring projecting outward is installed at an end close to the limiting portion of the introduction portion, and the metal installed in the medium joint. The seal tube is restricted by the restriction ring and cannot slide in the direction of the restriction portion, and at the same time, a C-shaped retainer that restricts the retreat of the metal seal tube is installed in the introduction portion. The device according to claim 2. A non-magnetic adjusting tube for adjusting the size of the space is attached in the space for accommodating the sample, and the outer diameter of the adjusting tube is equal to or less than the inner diameter of the reaction tube, and a channel for passing the replacement medium inside. The apparatus according to claim 2, wherein a flow guide groove for dividing the replacement medium is provided on the contact end surface between the adjusting tube and the sample. The apparatus according to claim 4, wherein the reaction tube, the medium joint, and the adjusting tube are made of a non-magnetic polyimide material. The device according to claim 2, wherein a diametrical seal ring is installed on the outer circumference of one end near the storage sample of the restricted portion. The second aspect of the present invention is characterized in that a metal net and a filter paper for suppressing the passage of the sample are installed at one end of each of the two restricted portions near the sample, and the mesh of the metal net and the filter paper is at least smaller than the particle size of the sample. The device described. The device according to claim 1, wherein the measuring device includes an electronic balance and a container for accommodating a discharged replacement medium, and the chock plug is connected to the container via piping. The supply device includes a material storage tank for providing gas or liquid, a regulator for adjusting the supply pressure of the material storage tank, and a liquid tank for accommodating a replacement medium, and the liquid tank has a supply end connected to the regulator. The discharge end is connected to the connector, and the regulator adjusts the gas or liquid discharged by the supply device to enter the liquid tank based on the measurement required pressure, and the replacement medium in the liquid tank. Is installed in the reaction tube after passing through the connector, and the connector is provided with two supply interfaces and one shared discharge interface, which are connected to a gas source and a liquid source, respectively, and at the same time, the said via a circuit. The apparatus according to claim 1, wherein the current supply amount and pressure value of the replacement medium are output to the control system. A fixed base is attached to one end away from the restricted portion of the introduction portion of the medium joint, and a storage groove for accommodating the mounting sheet of the CT device is provided on the bottom surface of the fixed base, and is provided around the radial direction of the fixed base. The device according to claim 2, wherein an adjusting screw twisted in the axial direction is installed to fix the fixing base and the above-mentioned mounting sheet. A measurement method using the apparatus according to any one of claims 1-10.
Select the corresponding amount of sample according to the test requirements, then place it in a small reaction tube made of non-magnetic material, adjust and limit the placement position of the sample with chock plugs at both ends, then each Step 100 of connecting the test device so that the reaction tube is located in the detection space of the CT device,
First, the control system acquires each initial data before measurement, selects the test pressure and test flow rate, then opens the liquid tank and injects distilled water at a predetermined flow rate into the reaction tube under the set pressure, and the measuring device In step 200, the amount of distilled water discharged after the sample has passed is recorded, and the permeation rate when the sample of distilled water is passed is calculated based on the amount of distilled water discharged per unit time.
When the flow velocity of the distilled water received by the measuring device stabilizes, the experiment is temporarily stopped to keep the current state in the reaction tube stationary, and then the sample in the reaction tube is sampled by the CT device using the radiation source. Step 300 of scanning at 360 degrees, acquiring and saving the image of the sample scanned this time, and then continuing the experiment.
As the experiment continues, the current test pressure is changed, steps 200 and 300 are repeated until a predetermined number of experiments, then data summarization is performed on the images acquired for each scan, and the pressures of the current samples are different. And step 400, which obtains the movement status of fine particles at a flow rate, thereby providing conditions to be met when actually mining natural gas hydrate in the corresponding formation. A measuring method using the apparatus according to -10. The criteria for changing the current test pressure changes based on the change in the pressure gradient. Specifically, the initial test pressure is 10 kpa, and the test pressures of each subsequent experiment are sequentially 30 kPa, 50 kPa, 75 kPa, and 100 kPa. The measuring method according to claim 11, wherein there is. The claim is characterized in that the sample is brought into close contact with the inner wall surface of the reaction tube and filled in the reaction tube so that distilled water does not flow through the gap between the sample and the reaction tube when performing an experiment. 11. The measuring method according to 11. As for the movement of fine particles at different pressures and flow rates of the current sample by repeating the steps 200 and 300 while changing the current test pressure, the rock reservoir sample composed of muddy silt is As the replacement time increases, deterioration of the permeation rate occurs at each replacement point, and finally a cake that increases the permeation resistance around the well is formed, and the time required for stabilizing the production volume in the low pressure section is long. becomes, and the measuring method according to claim 11, strata energy tends to be significantly reduced in the high pressure section, it is characterized. The measuring method according to claim 11, wherein when calculating the permeation rate, the current flow velocity can be measured first, and then the permeation rate can be obtained by the following formula.
(In the formula, ΔP is the pressure difference, Q is the flow velocity, μ is the viscosity of the injection solution, l is the core length, A is the cross-sectional area of the core, and K is the permeation rate.)