CN112557259A - Rock wettability measuring device and method under stratum water environment - Google Patents
Rock wettability measuring device and method under stratum water environment Download PDFInfo
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- CN112557259A CN112557259A CN202011618791.6A CN202011618791A CN112557259A CN 112557259 A CN112557259 A CN 112557259A CN 202011618791 A CN202011618791 A CN 202011618791A CN 112557259 A CN112557259 A CN 112557259A
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Abstract
The invention discloses a device and a method for measuring rock wettability under a stratum water environment, which relate to the field of oil and gas development research, and the device comprises: the accommodating container is transparent and has a cubic side wall with an upward opening; formation water contained in the containing body; the core slice is arranged in the formation water and extends along the horizontal direction; a support for supporting a core slice; the gas sampling device comprises a first needle tube and a trace gas sample injector connected with the first needle tube and used for injecting trace gas, wherein the outlet end of the first needle tube can extend in the vertical direction; the outlet end of the second needle tube can extend along the horizontal direction; a contact angle measuring instrument comprises a high-definition camera and a high-definition imager. The application can relate to a gas environment, and the contact angle of 'gas-water-rock' is measured, so that the wettability of gas on the surface of a mineral in an aqueous phase environment is obtained, and the wettability of a gas reservoir stratum is further revealed.
Description
Technical Field
The invention relates to the field of oil and gas development and research, in particular to a device and a method for measuring rock wettability under a stratum water environment.
Background
Wettability is the tendency of a phase fluid in a mixed phase fluid to spread or adhere to a solid surface, and is one of the most important properties in the surface characteristics of a solid material. Wetting refers to the phenomenon in which a gas or liquid phase spreads along the surface of a solid phase when the gas or liquid phase contacts the solid phase. The wetting contact angle can be taken as a physical quantity characterizing the degree of wetting of the surface of the mineral particles and the free energy of the surface. Previous studies have found that contact angle can be used as a measure of wettability of the major mineral constituent in oil and gas reservoirs on smooth, homogeneous mineral surfaces. Therefore, the wettability of the mineral can be characterized by measuring the contact angle of gas or liquid phase on the surface of the smooth mineral. The method for representing the wettability by adopting the wetting contact angle is simple to operate, has clear physical significance and is relatively wide in application.
However, because the wettability of reservoir rock is very complex, there has not been a satisfactory method to determine the wettability of reservoir rock under formation conditions.
Disclosure of Invention
Rock wettability measured in a laboratory can be used for estimating the wettability of rock under reservoir conditions, and a common measuring method is a hanging plate method, a self-absorption method and the like.
The rock wettability can be measured by the hanging plate method, fig. 1a is a structural schematic diagram of rock wettability measured by the hanging plate method in a laboratory, and fig. 1b is a structural schematic diagram of rock wettability measured by the hanging plate method in the laboratoryA schematic of the wettability, as shown in FIG. 1a, is first measured for the oil-water interfacial tension σowThen, the change f of the force generated when the rock plate passes through the gas-oil-water interface is measured by the rock plate, and then the cos theta and the theta value are calculated according to the related formula. As shown in FIG. 1a, when the oil-water interface starts moving upwards, the hanger plate assumes an advancing angle θ due to wetting retardation1Theta is shown in FIG. 1b1>θ, so the hanger plate is out of balance, and the force pulling down the hanger plate at this time is:
LσOWcosθ1
wherein L represents the three-phase perimeter length of the hanger plate, cm, sigmaowIndicates the oil-water interfacial tension, dyn/cm.
To rebalance the hanger plate, the balance force applied at the other end of the torsion balance is f1, which is the following according to the instrument characteristics:
f1=φ1Kg
wherein phi is1The number of the grids on the torque dial of the torque scale is shown, K represents the torque constant, namely one grid of the torque dial is equivalent to the mass of a balance weight, and g/grid represents the gravity acceleration.
When the torsion balance is operated to balance the hanging plate again, then:
f1=φ1Kg=Lσowcosθ1
rewriting the above equation then yields:
the right terms of the above formula are all parameters available through the instrument, so:
when the oil-water interface moves downwards, the receding angle of the static wetting hysteresis is theta2In the same way, the following can be obtained:
wherein phi is2The number of the grids on the torque dial when the oil-water interface moves down is shown.
From the above, the hanger plate method can only measure the contact angle of oil-water-rock, cannot relate to the gas environment, cannot measure the contact angle of gas-water-rock, and has certain limitations.
The self-priming method determines the wettability of reservoir rock by measuring the spontaneous suction speed of a wetting phase under the action of capillary pressure and the displacement amount of a non-wetting phase, and is a method for measuring the relative wetting capacity of oil and water to the rock. In order to measure the real wettability of oil reservoir sandstone, a fresh rock sample is used to ensure that the rock sample is polluted as little as possible in the sampling and preparation processes; in addition, the properties of oil and water are simulated in an oil layer as much as possible, and crude oil is diluted by neutral kerosene to prepare experimental oil with the viscosity similar to that of underground crude oil.
Fig. 2a is a schematic structural diagram of rock wettability measurement by a self-priming method in a laboratory, and fig. 2b is a schematic structural diagram of rock wettability measurement by a self-priming method in a laboratory, if the rock is hydrophilic, as shown in fig. 2b, a rock sample of saturated oil is placed in a water absorption instrument. Then, under the action of capillary force, water will automatically penetrate into the pores of the rock sample and displace oil in the pores. The displaced oil floats to the top of the water absorption instrument, and the volume of the oil can be read from the scales on the upper part of the water absorption instrument. The rock sample absorbs water, which means that the rock has certain hydrophilic capacity. If the rock is oleophilic, as shown in fig. 2a, a rock sample saturated with water is immersed in the oil suction instrument, then under the action of capillary force, the oil will automatically penetrate into the pores of the rock sample and displace the water in the pores. The displaced water sinks to the bottom of the oil absorption instrument, and the volume of the displaced water can be read from the scales at the bottom of the oil absorption instrument. The oil absorption of the rock sample indicates that the rock has certain oleophilic capacity.
In actual operation, similar rock samples are parallelly subjected to water absorption, oil displacement, oil absorption and water displacement experiments, and due to the wetting heterogeneity of the rock, the rock usually absorbs water and oil, so that if the water absorption is greater than the oil absorption, the rock sample is considered to be hydrophilic; on the contrary, if the oil absorption is larger than the water absorption, the rock sample is considered to be oleophilic; if the water absorption and oil absorption are similar, the rock sample is considered to be neutral and wet.
The method has the advantages of less used experimental instruments and simple experimental operation, can better reflect the actual condition of the oil layer, but can only qualitatively determine the wettability of the oil layer rock. The self-absorption method can only qualitatively judge the wettability of 'oil-water-rock', can not measure the contact angle, can not relate to the gas environment to measure the 'gas-water-rock' contact angle, and has great limitation.
In order to overcome the defects in the prior art, embodiments of the present invention provide a device and a method for measuring rock wettability in a formation water environment, which can relate to a gas environment, and measure and obtain a contact angle of "gas-water-rock", so as to obtain wettability of gas on a mineral surface in a water phase environment, thereby revealing wettability of a gas reservoir.
The specific technical scheme of the embodiment of the invention is as follows:
a device for measuring wettability of rock in stratum water environment comprises:
the accommodating container is transparent and has a cubic side wall with an upward opening;
formation water contained in the containing body;
a core slice disposed in the formation water, the core slice extending in a horizontal direction;
a support for supporting the core slice;
the device comprises a first needle tube and a trace gas injector connected with the first needle tube and used for injecting trace gas, wherein the outlet end of the first needle tube can extend in the vertical direction and can be arranged below the lower surface of the core slice, the trace gas injector can generate trace gas and discharge a bubble through the first needle tube, and the bubble floats upwards and is adsorbed on the lower surface of the core slice;
the outlet end of the second needle tube can extend along the horizontal direction and can be arranged below the lower surface of the core slice, and the water injector discharges formation water through the second needle tube so as to flush the bubbles away from the lower surface of the core slice;
the contact angle measuring instrument comprises a high-definition camera and a high-definition imager, wherein the high-definition camera can shoot a high-definition image of the contact between the lower surface of the core slice and the bubbles in the horizontal direction outside the accommodating container and display the high-definition image through the high-definition imager, so that the focal length and the lens position of the high-definition camera are continuously adjusted to obtain a clear contact angle formed by the bubbles and the lower surface of the core slice.
Preferably, the containment vessel comprises a cuvette made of quartz.
Preferably, when the micro gas injector generates micro gas and discharges a bubble through the first needle tube, the distance between the outlet end of the first needle tube and the lower surface of the core slice is between 3mm and 5 mm.
Preferably, the precision of the trace gas injector is equal to or higher than 0.1 uL.
Preferably, the first needle cannula is substantially U-shaped and the second needle cannula is substantially L-shaped.
Preferably, the core slice is made of a natural core of a core section corresponding to the gas reservoir gas-bearing horizon depth.
A method for measuring rock wettability in a stratum water environment adopts any one of the devices for measuring rock wettability in the stratum water environment, and comprises the following steps:
performing linear cutting on the natural core to obtain a core slice with a flat and smooth end surface;
injecting formation water into the containment body until the top end of the support is submerged;
placing the core slice on a bracket in a containing body, and enabling the formation water to submerge the core slice, wherein the core slice extends along the horizontal direction;
arranging an outlet end of a first needle tube to extend along the vertical direction and be 3mm to 5mm below the lower surface of the core slice;
starting a trace gas sample injector to generate trace gas and discharging a bubble through the first needle tube, wherein the bubble floats upwards and is adsorbed on the lower surface of the core slice;
after standing, the bubbles, the formation water and the core slices form a stable gas-water-rock three-phase environment;
shooting a high-definition image of the contact between the lower surface of the core slice and the bubbles along the horizontal direction outside the accommodating body by using a high-definition camera in a contact angle measuring instrument, displaying the high-definition image by using the high-definition imager, and continuously adjusting the focal length and the lens position of the high-definition camera to obtain a clear contact angle formed by the bubbles and the lower surface of the core slice;
measuring the angle of the contact angle in a high-definition graph with a clear contact angle by using angle measurement software to obtain a value of the angle of the contact angle;
starting a water injector to discharge water through the second needle tube so as to flush the bubbles away from the lower surface of the core slice, and repeating the process to obtain a plurality of groups of effective contact angle values;
and judging the wettability of the rock core according to the average value of the multiple groups of effective contact angle values, wherein if the contact angle value is between 0 and 75 degrees, the rock core is hydrophilic, if the contact angle value is between 75 and 105 degrees, the rock core is middle-wet, and if the contact angle value is between 105 and 180 degrees, the rock core is oleophilic.
Preferably, the trace gas injector is activated to generate a trace amount of gas, the volume of the trace amount of gas being 5 uL.
Preferably, the contact angles in the high-definition figure with clear contact angles are two, respectively located on the left and right sides of the bubble.
Preferably, the natural core is subjected to line cutting and then is polished by abrasive paper to obtain a core slice with a flat and smooth end surface.
The technical scheme of the invention has the following remarkable beneficial effects:
1. according to the method, the natural core is selected as the core slice, and the contact angle of gas on the surface of the core slice in a stratum water environment is measured, so that the wettability of the gas on the surface of a mineral in a water phase environment is known, and reference is provided for disclosing the wettability of a gas reservoir.
2. According to the invention, small bubbles are injected into the lower part of the rock core slice which is kept in a stratum water environment through the first needle tube and the trace gas sample injector, the bubbles on the lower surface of the rock core slice are focused and amplified by using a high-definition camera in the contact angle measuring instrument and displayed on a high-definition imager, and the included angle formed by the tangent line of the bubbles and the phase interface, namely the size of the contact angle, is accurately measured by using software for measuring the angle professionally, so that the contact angle between gas, stratum water and rock can be measured, and the technical problem that the gas-water-rock contact angle is difficult to measure is solved.
Specific embodiments of the present invention are disclosed in detail with reference to the following description and drawings, indicating the manner in which the principles of the invention may be employed. It should be understood that the embodiments of the invention are not so limited in scope. The embodiments of the invention include many variations, modifications and equivalents within the spirit and scope of the appended claims. Features that are described and/or illustrated with respect to one embodiment may be used in the same way or in a similar way in one or more other embodiments, in combination with or instead of the features of the other embodiments.
Drawings
The drawings described herein are for illustration purposes only and are not intended to limit the scope of the present disclosure in any way. In addition, the shapes, the proportional sizes, and the like of the respective members in the drawings are merely schematic for facilitating the understanding of the present invention, and do not specifically limit the shapes, the proportional sizes, and the like of the respective members of the present invention. Those skilled in the art, having the benefit of the teachings of this invention, may choose from the various possible shapes and proportional sizes to implement the invention as a matter of case.
FIG. 1a is a schematic structural diagram of rock wettability measurement by a hanging plate method in a laboratory;
FIG. 1b is a schematic diagram of a structure for measuring rock wettability by a hanger plate method in a laboratory;
FIG. 2 is a schematic structural diagram of rock wettability measurement by a self-priming method in a laboratory;
FIG. 3 is a schematic structural diagram of a rock wettability measuring device in a formation water environment in an embodiment of the application;
FIG. 4a is an angular measurement schematic of the contact angle of the bubble with the left side of the lower face of the core slice;
FIG. 4b is a schematic angular measurement of the contact angle of the bubble with the right side formed by the lower end face of the core slice;
FIG. 5 is a graph plotting multiple sets of contact angle values.
Reference numerals of the above figures:
1. air bubbles; 2. formation water; 3. core slicing; 4. a support; 5. a first needle tube; 6. a second needle tube; 7. a container body; 8. a trace gas sample injector; 9. a water injector; 10. a contact angle measuring instrument; 101. a high-definition camera; 102. a high-definition imager; 11. a computer.
Detailed Description
The details of the present invention can be more clearly understood in conjunction with the accompanying drawings and the description of the embodiments of the present invention. However, the specific embodiments of the present invention described herein are for the purpose of illustration only and are not to be construed as limiting the invention in any way. Any possible variations based on the present invention may be conceived by the skilled person in the light of the teachings of the present invention, and these should be considered to fall within the scope of the present invention. It will be understood that when an element is referred to as being "disposed on" another element, it can be directly on the other element or intervening elements may also be present. When an element is referred to as being "connected" to another element, it can be directly connected to the other element or intervening elements may also be present. The terms "mounted," "connected," and "connected" are to be construed broadly and may include, for example, mechanical or electrical connections, communications between two elements, direct connections, indirect connections through intermediaries, and the like. The terms "vertical," "horizontal," "upper," "lower," "left," "right," and the like as used herein are for illustrative purposes only and do not denote a unique embodiment.
Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs. The terminology used herein in the description of the present application is for the purpose of describing particular embodiments only and is not intended to be limiting of the application. As used herein, the term "and/or" includes any and all combinations of one or more of the associated listed items.
In this application, a device for measuring wettability of rock in a formation water environment is provided, fig. 3 is a schematic structural diagram of the device for measuring wettability of rock in a formation water environment in the embodiment of this application, and as shown in fig. 3, the device for measuring wettability of rock in a formation water environment may include: the accommodating container 7 with an upward opening and a cubic transparent side wall; formation water 2 contained in the containing body 7; the core slice 3 is arranged in the formation water 2, and the core slice 3 extends along the horizontal direction; a support 4 for supporting the core slice 3; the device comprises a first needle tube 5 and a trace gas injector 8 connected with the first needle tube 5 and used for injecting trace gas, wherein the outlet end of the first needle tube 5 can extend in the vertical direction and can be arranged below the lower surface of the core slice 3, the trace gas injector 8 can generate trace gas and discharge a bubble 1 through the first needle tube 5, and the bubble 1 floats upwards and is adsorbed on the lower surface of the core slice 3; the outlet end of the second needle tube 6 can extend along the horizontal direction and can be arranged below the lower surface of the core slice 3, and the water injector 9 is connected with the second needle tube 6 and can discharge formation water 2 through the second needle tube 6 so as to flush the bubbles 1 from the lower surface of the core slice 3; the contact angle measuring instrument 10 comprises a high-definition camera 101 and a high-definition imager 102, wherein the high-definition camera 101 can shoot a high-definition image of the contact between the lower surface of the core slice 3 and the bubbles 1 in the horizontal direction outside the accommodating container 7 and display the high-definition image through the high-definition imager 102, so that the focal length and the lens position of the high-definition camera 101 are continuously adjusted to obtain a clear contact angle formed by the bubbles 1 and the lower surface of the core slice 3. The device for measuring the rock wettability under the water environment of the local layer can relate to a gas environment, and a contact angle of 'gas-water-rock' is measured, so that the wettability of gas on the surface of a mineral in the water environment is obtained, and the wettability of a gas reservoir is further revealed.
In order to better understand the rock wettability measuring device in the formation water environment in the present application, it will be further explained and illustrated below. As shown in fig. 3, the rock wettability measuring apparatus in formation water environment may include: the device comprises a containing body 7, formation water 2, a core slice 3, a bracket 4, a first needle tube 5, a trace gas sample injector 8, a second needle tube 6, a water injector 9 and a contact angle measuring instrument 10.
As shown in fig. 3, the container 7 may be a transparent container with an upward opening and a transparent sidewall. The contact angle measuring instrument 10 can clearly photograph the inside of the accommodating body 7 through the transparent side wall. Therefore, in order to reduce the dimensional deviation of the inside of the accommodating container 7 imaged by the contact angle measuring instrument 10 due to the reflection and scattering of light caused by the curved side surface, since the size of the bubble 1 itself is very small, the accommodating container 7 needs to be a container in which the side walls of the cube are flat, so that the accuracy and the definition of the imaged bubble 1 can be ensured, and the dimensional deviation is not caused. As a practical matter, the receiving container 7 can be a cuvette made of quartz.
As shown in fig. 3, the formation water 2 is contained in the containing body 7. The formation water 2 is the formation water 2 which is taken from an underground gas reservoir on the actual production site of the gas field and is used for creating a water environment, so that the water phase environment in the storage layer of the actual gas reservoir can be simulated.
As shown in fig. 3, a holder 4 may be provided at the bottom center inside the receiving container 7 for holding the core slice 3, thereby making the core slice 3. The formation water 2 is contained to a depth of approximately 2cm or so over the top of the rack 4. The top of support 4 is used for placing core slice 3, can make core slice 3 extend along the horizontal direction moreover, and core slice 3 need keep the level as far as possible promptly, just so can make the contact angle that later stage bubble 1 and core slice 3 lower surface produced all the same basically at each angle. If the core slice 3 is not flat, the contact angle between the bubble 1 and the lower surface of the core slice 3 is larger in one direction and smaller in the other opposite direction, and the contact angles in the other directions gradually change from the maximum value in one direction to the minimum value in the other direction, so that a relatively large error may exist in the contact angle in one direction photographed by the contact angle measuring instrument 10 at a later stage.
As shown in fig. 3, the core slice 3 is disposed in the formation water 2 and supported by the support 4, the formation water 2 submerges the entire core slice 3, and the core slice 3 extends in a horizontal direction. In the process of drilling a gas well, a core section corresponding to the depth of a gas reservoir gas-containing layer position is selected from a natural core taken by a core drill bit, and a small cylindrical core with the diameter of 2.5cm and the length of 6cm can be drilled along the radial direction by utilizing a small core drilling device and perpendicular to the circumference of the side surface of the natural core. The cylinder core slice 3 with the thickness of 1cm is cut from the end face of the small core, the small core needs to be subjected to linear cutting in the cutting process, so that the core slice 3 with the thickness of 1cm is complete and free of damage, and after the linear cutting, the cutting end face of the core slice 3 is more flat and smooth, the real and accurate measuring result can be obtained, and then the core slice 3 can be polished by abrasive paper, so that the enough flatness and smoothness are ensured.
As shown in FIG. 3, the outlet end of the first syringe 5 can extend in a vertical direction and be directed upward. The outlet end of the first needle tube 5 can be arranged below the lower surface of the core slice 3. In order to facilitate the penetration of the first needle 5 from the surface of the formation water 2 containing the receptacle 7 and to enable its outlet end to extend in a vertical direction and to be arranged below the lower surface of the core slice 3, the first needle 5 may preferably be substantially U-shaped.
As shown in fig. 3, the micro gas injector 8 is connected to the first needle 5, and the micro gas injector 8 is used for injecting a micro gas. The precision of the micro gas injector 8 is 0.1uL or more. For example, the total volume of the micro gas injector 8 may be 5. mu.L, that is, 5. mu.L, with 50 scales in total, with an accuracy of 0.1. mu.L. The exit end of first needle tubing 5 can set up in the below of the lower surface of core slice 3, and trace gas injector 8 can produce trace gas and through a bubble 1 of first needle tubing 5 discharge, bubble 1 come-up and adsorb in core slice 3 lower surface to form a upper end for being close planar small bubble 1, the diameter of this bubble 1 is about 1 mm. When trace gas injector 8 produced trace gas and discharged a bubble 1 through first needle tube 5, the distance of the exit end of first needle tube 5 and 3 lower surfaces of core slice is between 3mm to 5mm, just so can realize the control to discharge bubble 1, make it can come up and adsorb in 3 lower surfaces of core slice as far as possible under the action of gravity, avoid escaping and can't adsorb 3 lower surfaces of core slice from the side of core slice 3.
In addition, the small-size air bubbles can greatly reduce the upward floating force of the air bubbles in water. If the bubble is great, the bubble can be extruded and deformed because of the blocking and buoyancy effects of the core slice on the upper part of the bubble after floating in water, namely the bubble can be flattened, so that the contact angle between the bubble and the core slice is reduced, and the measuring result is inaccurate. Therefore, the influence of the buoyancy of the bubbles cannot be ignored, and the very small bubbles can greatly reduce the upward buoyancy of the bubbles in water, so that the influence of external factors on the measurement precision is reduced, and the scientificity and the practicability of the invention are ensured. The conventional gas generating device is difficult to generate bubbles with the small volume, and the micro gas sample injector is adopted in the invention, so that the problems are effectively solved, and the small bubbles can be generated, thereby meeting the design requirements of the invention and realizing the design purpose of the invention.
As shown in fig. 3, the outlet end of the second needle 6 can extend horizontally and can be disposed below the lower surface of the core slice 3, with the outlet end of the second needle 6 facing the point where the bubble 1 contacts the lower surface of the core slice 3. After a clear contact angle of one bubble 1 with the lower surface of the core slice 3 is obtained by the contact angle measuring instrument 10, the water injector 9 can be used to discharge the formation water 2 through the second needle 6 to flush the bubble 1 off the lower surface of the core slice 3 so that the next set of measurements can be performed. In order to facilitate the penetration of the second needle 6 from the surface of the formation water 2 containing the receptacle 7 and to enable its outlet end to extend horizontally and below the lower surface of the core slice 3, the second needle 6 may preferably be substantially L-shaped.
As shown in fig. 3, the contact angle measuring instrument 10 may include a high-definition camera 101 and a high-definition imager 102, and the high-definition camera 101 may photograph a high-definition image of the lower surface of the core slice 3 in contact with the bubbles 1 in the horizontal direction outside the accommodating container 7 and display the high-definition image by the high-definition imager 102. Because the diameter of the bubble 1 is very small, generally about 1mm, the display of the high-definition imager 102 can be magnified and displayed, and at the moment, the position and the focal length of the lens of the high-definition camera 101 can be finely and finely adjusted according to the clarity after the magnified display, so that the focal length and the lens position of the high-definition camera 101 are continuously adjusted to obtain the most clear contact angle formed by the bubble 1 and the lower surface of the core slice 3, and the preparation is made for obtaining the optimal and accurate measurement result in the later period. Of course, the contact angle measuring device 10 may be connected to the computer 11, so that the computer 11 can acquire and store the high-definition image captured by the contact angle measuring device 10.
If formation water is dropped on a core slice in a gas environment, the water drop is magnified and photographed by an optical system or a microscope, and the contact angle can be measured on the photograph. However, for the hypertonic core slice, the dropped water drops are quickly absorbed into the core slice, and the stable water drops are difficult to capture, so that the contact angle cannot be measured. Based on the practical situation, the measuring device is invented in the application, and the contact angle of the bubbles on the rock surface in the water phase environment is measured. The device solves the technical problem that the contact angle cannot be measured due to the fact that water drops on the high-permeability core slice are sucked in a gas environment, is suitable for both the high-permeability core and the low-permeability core, and has universality and universality.
Based on the device for measuring the wettability of the rock in the stratum water environment, the application also provides a method for measuring the wettability of the rock in the stratum water environment, which comprises the following steps:
and performing linear cutting on the natural core to obtain a core slice 3 with a flat and smooth end surface. The selection and processing of the natural core into core slices 3 may be as described above and will not be described in detail here.
The core slice 3 is placed on a holder 4 in a receptacle 7 and the core slice 3 is flooded with formation water 2, the core slice 3 extending in a horizontal direction. Specifically, the core slice 3 is placed on the holder 4 and its end face is ensured to be horizontal.
The outlet end of the first needle tube 5 is arranged to extend along the vertical direction and is positioned between 3mm and 5mm below the lower surface of the core slice 3. Specifically, connect first needle pipe 5 and trace gas injector 8, ensure that the junction is sealed perfect gas-tight, make first needle pipe 5 be along the exit end that vertical direction extends place the lower surface of core slice 3 in towards the top to make the syringe needle of first needle pipe 5 exit end and 3 lower surfaces of core slices keep the interval between 3mm to 5 mm. In the process, the second needle tube 6 and the water injector 9 can be connected to ensure that the joint is sealed and watertight, so that the outlet end of the second needle tube 6 extends along the horizontal direction and is arranged below the lower surface of the core slice 3.
The micro gas injector 8 is started to generate micro gas and discharge a bubble 1 through the first needle tube 5, and the bubble 1 floats upwards and is adsorbed on the lower surface of the core slice 3. Specifically, the microsyringe is started to generate trace gas, the trace gas is upwards discharged through the outlet end of the first needle tube 5 and then conveyed to the lower surface of the core slice 3, the volume of the trace gas generated by the microsyringe is about 5 mu L, the trace gas is discharged from the needle head of the first needle tube 5, and the trace gas automatically floats upwards in formation water 2 by virtue of buoyancy and is adsorbed on the lower surface of the core slice 3 to form a micro bubble 1 with the diameter of about 1 mm.
After standing, the bubbles 1, the formation water 2 and the core slice 3 form a stable gas-water-rock three-phase environment. Specifically, after the bubbles 1 are adsorbed on the lower surface of the core slice 3, standing is carried out for a period of time, so that the bubbles 1, the formation water 2 and the core slice 3 form a stable three-phase environment of 'gas-water-rock', and a more real and more accurate measurement result can be obtained at a later stage.
A high-definition image of the contact between the lower surface of the core slice 3 and the bubbles 1 is shot in the horizontal direction outside the accommodating container 7 by using a high-definition camera 101 in the contact angle measuring instrument 10 and is displayed by a high-definition imager 102, and the focal length and the lens position of the high-definition camera 101 are continuously adjusted to obtain a clear contact angle formed by the bubbles 1 and the lower surface of the core slice 3. Specifically, after a stable "gas-water-rock" three-phase environment is obtained, the contact angle measuring instrument 10 is activated, for example, the contact angle measuring instrument 10 may be a contact angle measuring instrument 10 of type E5637-C manufactured by Sanchez Technologies, france. The position and the focal length of a lens of the high-definition camera 101 are adjusted, so that the bubbles 1 on the lower surface of the core slice 3 and the lower end surface of the core slice 3 can present a high-definition amplified picture on a high-definition imager 102 of the contact angle measuring instrument 10. In the process, according to the clarity of the amplified display of the bubble 1 on the high-definition imager 102, fine adjustment is performed on the position and the focal length of the lens of the high-definition camera 101, so that the clearest high-definition amplified picture of the bubble 1 can be obtained, and the optimal and accurate measurement result can be obtained in the later stage.
The angle of the contact angle in the high-resolution plot with clear contact angle was measured using the measurement angle software to obtain the contact angle value. Specifically, the high-definition map obtained as described above is derived from the contact angle measuring instrument 10, stored in the computer 11, and the contact angle is measured by using the professional measurement angle software PicPick, where the bubble 1 forms two left and right contact angles with the lower end surface of the core slice 3, fig. 4a is a schematic view of angle measurement of the left contact angle formed by the bubble with the lower end surface of the core slice, and fig. 4b is a schematic view of angle measurement of the right contact angle formed by the bubble with the lower end surface of the core slice, so that in order to reduce the measurement error and obtain more accurate measurement results, as shown in fig. 4a and 4b, one picture needs to measure two left and right contact angles formed by the microbubble 1 with the lower end surface of the core slice 3.
The injector 9 is activated to expel water through the second needle tube 6 to flush the bubbles 1 off the lower surface of the core slice 3, and the process is repeated to obtain multiple sets of effective contact angle values. In particular, because the air bubbles 1 in the rock wettability measuring method under the local layer water environment are very small, the contact angle formed by the contact angle of the contact angle with the lower end surface of the core slice 3 is accidental and is influenced by the outside and different positions of the lower end surface of the core slice 3, in order to reduce the measurement error caused by a single group of measurement results, a stable 'gas-water-rock' three-phase environment needs to be created for a plurality of times by changing the position of the outlet end of the first needle tube 5 on the lower surface of the core slice 3, after a new bubble 1 is generated each time, the position and the focal length of the lens of the high-definition camera 101 need to be adjusted again, so that the new bubble 1 and the lower end surface of the core slice 3 can present a high-definition amplified picture on the high-definition imager 102, therefore, a new high-definition enlarged image is obtained, so that the angle measurement of the contact angle in the high-definition image can be carried out for multiple times to obtain multiple groups of contact angle values. Before a new bubble 1 is generated by the first needle tube 5 each time, a small amount of formation water 2 is injected from one side below the core slice 3 by using the second needle tube 6 connected with the water injector 9, and the bubble 1 generated last time is flushed away from the lower surface of the core slice 3. The purpose of this is to avoid the mutual influence between the bubbles 1 to cause inaccurate measurement results, and also to avoid the influence of a plurality of bubbles 1 on the imaging effect when the high-definition camera 101 of the contact angle measuring instrument 10 is used for shooting a high-definition magnified picture. The whole process needs to be repeated for 5 to 10 times or even more, so as to obtain a plurality of contact angle measurement results.
And judging the wettability of the rock core according to the average value of the multiple groups of effective contact angle values, wherein if the contact angle value is between 0 and 75 degrees, the rock core is hydrophilic, if the contact angle value is between 75 and 105 degrees, the rock core is intermediate-wetting, and if the contact angle value is between 105 and 180 degrees, the rock core is oleophilic.
Specifically, the measurement results of the multiple sets of contact angles including the left and right contact angles can be summarized in table 1, the measurement results of each picture in the table can be plotted as a graph, and fig. 5 is a graph obtained by plotting the multiple sets of contact angle values, as shown in fig. 5.
TABLE 1 summary of contact angle measurements
Comparing the measurement results of each picture, for example, it can be seen from the observation of the curve form that the measurement result of picture number 4 is significantly different from the measurement results of other pictures, and has a large error, and should be regarded as an invalid result and discarded. All valid measurements are then summed and divided by the number of valid samples and averaged. In this embodiment, the result is 43.74 degrees, and the final calculated average value of 43.74 is taken as the effective "gas-water-rock" contact angle, i.e., the "gas-water-rock" contact angle of the core slice 3 is 43.74 degrees. Thus, the measured core was hydrophilic, i.e., water wet.
The device and the method for measuring the rock wettability under the stratum water environment have the following beneficial effects that: 1. according to the method, a natural core is selected as the core slice 3, the gas reservoir accumulation process is carried out in a water environment, and the factor of the water environment is also considered for measuring the wettability, so that the contact angle of gas on the surface of the core slice 3 in the formation water 2 environment of the core slice 3 is measured, the wettability of the gas on the surface of a mineral in a water phase environment is known, the accumulation environment of the gas reservoir can be reduced, the actual condition is better met, and reference is provided for disclosing the wettability of the gas reservoir. 2. According to the invention, small bubbles 1 are injected below a core slice 3 which is kept in a formation water 2 environment through a first needle tube 5 and a trace gas sample injector 8, the bubbles 1 on the lower surface of the core slice 3 are focused and amplified by a high-definition camera 101 in a contact angle measuring instrument 10 and displayed on a high-definition imager 102, and the included angle formed by the tangent line of the bubbles 1 and the phase interface, namely the size of the contact angle, is accurately measured by software for measuring the angle professionally, so that the contact angle between gas, formation water 2 and rock can be measured, and the technical problem that the contact angle of 'gas-water-rock' is difficult to measure is solved.
All articles and references disclosed, including patent applications and publications, are hereby incorporated by reference for all purposes. The term "consisting essentially of …" describing a combination shall include the identified element, ingredient, component or step as well as other elements, ingredients, components or steps that do not materially affect the basic novel characteristics of the combination. The use of the terms "comprising" or "including" to describe combinations of elements, components, or steps herein also contemplates embodiments that consist essentially of such elements, components, or steps. By using the term "may" herein, it is intended to indicate that any of the described attributes that "may" include are optional. A plurality of elements, components, parts or steps can be provided by a single integrated element, component, part or step. Alternatively, a single integrated element, component, part or step may be divided into separate plural elements, components, parts or steps. The disclosure of "a" or "an" to describe an element, ingredient, component or step is not intended to foreclose other elements, ingredients, components or steps.
The embodiments in the present specification are described in a progressive manner, each embodiment focuses on differences from other embodiments, and the same and similar parts among the embodiments are referred to each other. The above embodiments are merely illustrative of the technical ideas and features of the present invention, and the purpose thereof is to enable those skilled in the art to understand the contents of the present invention and implement the present invention, and not to limit the protection scope of the present invention. All equivalent changes and modifications made according to the spirit of the present invention should be covered within the protection scope of the present invention.
Claims (10)
1. The device for measuring the wettability of the rock in the stratum water environment is characterized by comprising the following components in parts by weight:
the accommodating container is transparent and has a cubic side wall with an upward opening;
formation water contained in the containing body;
a core slice disposed in the formation water, the core slice extending in a horizontal direction;
a support for supporting the core slice;
the device comprises a first needle tube and a trace gas injector connected with the first needle tube and used for injecting trace gas, wherein the outlet end of the first needle tube can extend in the vertical direction and can be arranged below the lower surface of the core slice, the trace gas injector can generate trace gas and discharge a bubble through the first needle tube, and the bubble floats upwards and is adsorbed on the lower surface of the core slice;
the outlet end of the second needle tube can extend along the horizontal direction and can be arranged below the lower surface of the core slice, and the water injector discharges formation water through the second needle tube so as to flush the bubbles away from the lower surface of the core slice;
the contact angle measuring instrument comprises a high-definition camera and a high-definition imager, wherein the high-definition camera can shoot a high-definition image of the contact between the lower surface of the core slice and the bubbles in the horizontal direction outside the accommodating container and display the high-definition image through the high-definition imager, so that the focal length and the lens position of the high-definition camera are continuously adjusted to obtain a clear contact angle formed by the bubbles and the lower surface of the core slice.
2. The apparatus of claim 1, wherein the containment vessel comprises a cuvette fabricated from quartz.
3. The device for measuring rock wettability in a formation water environment according to claim 1, wherein when the trace gas injector generates a trace gas and discharges a bubble through the first needle tube, the distance between the outlet end of the first needle tube and the lower surface of the core slice is between 3mm and 5 mm.
4. The device for measuring the wettability of the rock in the formation water environment according to claim 1, wherein the precision of the trace gas sample injector is higher than or equal to 0.1 uL.
5. The device of claim 1, wherein the first needle tube is substantially U-shaped and the second needle tube is substantially L-shaped.
6. The device for measuring rock wettability in the formation water environment according to claim 1, wherein the core slice is made of a natural core of a core section corresponding to the gas reservoir gas-bearing horizon depth.
7. A method for measuring wettability of rock in a formation water environment, which is characterized by adopting the device for measuring wettability of rock in a formation water environment according to any one of claims 1 to 6, and comprises the following steps:
performing linear cutting on the natural core to obtain a core slice with a flat and smooth end surface;
injecting formation water into the containment body until the top end of the support is submerged;
placing the core slice on a bracket in a containing body, and enabling the formation water to submerge the core slice, wherein the core slice extends along the horizontal direction;
arranging an outlet end of a first needle tube to extend along the vertical direction and be 3mm to 5mm below the lower surface of the core slice;
starting a trace gas sample injector to generate trace gas and discharging a bubble through the first needle tube, wherein the bubble floats upwards and is adsorbed on the lower surface of the core slice;
after standing, the bubbles, the formation water and the core slices form a stable gas-water-rock three-phase environment;
shooting a high-definition image of the contact between the lower surface of the core slice and the bubbles along the horizontal direction outside the accommodating body by using a high-definition camera in a contact angle measuring instrument, displaying the high-definition image by using the high-definition imager, and continuously adjusting the focal length and the lens position of the high-definition camera to obtain a clear contact angle formed by the bubbles and the lower surface of the core slice;
measuring the angle of the contact angle in a high-definition graph with a clear contact angle by using angle measurement software to obtain a value of the angle of the contact angle;
starting a water injector to discharge water through the second needle tube so as to flush the bubbles away from the lower surface of the core slice, and repeating the process to obtain a plurality of groups of effective contact angle values;
and judging the wettability of the rock core according to the average value of the multiple groups of effective contact angle values, wherein if the contact angle value is between 0 and 75 degrees, the rock core is hydrophilic, if the contact angle value is between 75 and 105 degrees, the rock core is middle-wet, and if the contact angle value is between 105 and 180 degrees, the rock core is oleophilic.
8. The method for measuring rock wettability in the formation water environment according to claim 7, wherein a trace gas injector is started to generate a trace gas, and the volume of the trace gas is 5 uL.
9. The method for measuring rock wettability in the formation water environment according to claim 7, wherein the number of the contact angles in the high-definition graph with clear contact angles is two, and the two contact angles are respectively located on the left side and the right side of the bubble.
10. The method for measuring rock wettability in the stratum water environment according to claim 7, wherein a natural core is subjected to line cutting and then is ground by using sand paper to obtain a core slice with a flat and smooth end surface.
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