CN111022023B - Atomized acid shaft flow simulation device for gas injection development of fracture-cavity oil reservoir and working method thereof - Google Patents
Atomized acid shaft flow simulation device for gas injection development of fracture-cavity oil reservoir and working method thereof Download PDFInfo
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- E—FIXED CONSTRUCTIONS
- E21—EARTH OR ROCK DRILLING; MINING
- E21B—EARTH OR ROCK DRILLING; OBTAINING OIL, GAS, WATER, SOLUBLE OR MELTABLE MATERIALS OR A SLURRY OF MINERALS FROM WELLS
- E21B43/00—Methods or apparatus for obtaining oil, gas, water, soluble or meltable materials or a slurry of minerals from wells
- E21B43/25—Methods for stimulating production
- E21B43/26—Methods for stimulating production by forming crevices or fractures
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- E—FIXED CONSTRUCTIONS
- E21—EARTH OR ROCK DRILLING; MINING
- E21B—EARTH OR ROCK DRILLING; OBTAINING OIL, GAS, WATER, SOLUBLE OR MELTABLE MATERIALS OR A SLURRY OF MINERALS FROM WELLS
- E21B43/00—Methods or apparatus for obtaining oil, gas, water, soluble or meltable materials or a slurry of minerals from wells
- E21B43/16—Enhanced recovery methods for obtaining hydrocarbons
- E21B43/166—Injecting a gaseous medium; Injecting a gaseous medium and a liquid medium
- E21B43/168—Injecting a gaseous medium
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- E—FIXED CONSTRUCTIONS
- E21—EARTH OR ROCK DRILLING; MINING
- E21B—EARTH OR ROCK DRILLING; OBTAINING OIL, GAS, WATER, SOLUBLE OR MELTABLE MATERIALS OR A SLURRY OF MINERALS FROM WELLS
- E21B47/00—Survey of boreholes or wells
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- E—FIXED CONSTRUCTIONS
- E21—EARTH OR ROCK DRILLING; MINING
- E21B—EARTH OR ROCK DRILLING; OBTAINING OIL, GAS, WATER, SOLUBLE OR MELTABLE MATERIALS OR A SLURRY OF MINERALS FROM WELLS
- E21B49/00—Testing the nature of borehole walls; Formation testing; Methods or apparatus for obtaining samples of soil or well fluids, specially adapted to earth drilling or wells
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- E—FIXED CONSTRUCTIONS
- E21—EARTH OR ROCK DRILLING; MINING
- E21B—EARTH OR ROCK DRILLING; OBTAINING OIL, GAS, WATER, SOLUBLE OR MELTABLE MATERIALS OR A SLURRY OF MINERALS FROM WELLS
- E21B49/00—Testing the nature of borehole walls; Formation testing; Methods or apparatus for obtaining samples of soil or well fluids, specially adapted to earth drilling or wells
- E21B49/008—Testing the nature of borehole walls; Formation testing; Methods or apparatus for obtaining samples of soil or well fluids, specially adapted to earth drilling or wells by injection test; by analysing pressure variations in an injection or production test, e.g. for estimating the skin factor
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Abstract
An atomized acid shaft flow simulation platform for gas injection development of fracture-cavity oil reservoirs mainly comprises a double-flow Venturi atomization generating device, a shaft flow simulation device and an atomization evaluation device; the atomization generating device comprises a gas path system, a liquid path system and an atomization generator; the gas path system comprises an air compressor, a gas throttle valve and a gas pressure gauge; the liquid system comprises a high-pressure acid-resistant pump, a liquid throttle valve and a liquid pressure gauge; the simulation shaft is used for connecting the double-flow type Venturi atomization generating device and comprises a vertical shaft, a horizontal simulation stratum and a liquid collection device; the observation system comprises a nanometer laser particle size analyzer. A working method of an atomized acid shaft flow simulation platform for gas injection development of a fracture-cavity oil reservoir. The simulation platform can be applied to an oil field site, injection discharge capacity is controlled through a gas-liquid path system, higher acid liquor atomization rate is kept according to site construction requirements, the acidification effect of a fracture-cavity oil reservoir is improved, and effective communication of fracture-cavity reservoir unit bodies is realized.
Description
Technical Field
The invention relates to an atomized acid shaft flow simulation device for gas injection development of a fracture-cavity oil reservoir and a working method thereof, belonging to the technical field of oil-gas reservoir production increasing measures.
Background
The acidification can effectively remove the pollution and the blockage of a reservoir near a shaft, improve the connectivity between the shaft and the reservoir and recover or improve the oil gas yield, and is a main technical measure for developing a low-porosity and low-permeability carbonate reservoir. In the acidification, the acid etching results can be divided into surface etching, wormhole etching and uniform etching according to different etching forms. The main factor influencing the carbonate karst corrosion form in the acidification process is H+Mass transfer rate and surface reaction rate. When the mass transfer speed is lower than the surface reaction speed, the corrosion form is surface corrosion, otherwise, the corrosion form is uniform corrosion, and wormhole corrosion can be formed only when the mass transfer speed is similar to the surface reaction speed. The mass transfer speed and the surface reaction speed are respectively influenced by the acid liquid injection speed and the injection mode. Therefore, in order to improve the acidification construction effect, the acid liquor injection speed must be reasonably controlled, and the acid liquor injection mode is preferably selected.
The fracture-cavity type oil reservoir develops solution cavities besides a plurality of structural fractures and solution cavities with complex structures and extremely irregular geometric shapes. When the conventional acid is used for acidification, the injected acid liquid may be accumulated in a large amount in the fracture-cavity storage unit, so that the waste of the acid liquid is caused, and the expected target is difficult to achieve. Once the acid liquor enters the cavern, the cavern is expanded, so that the earthworm hole extension is stopped, and the acid liquor is not beneficial to cave penetration. While the acid rock reaction rate of the gelled acid, crosslinked acid, gelled acid is relatively less affected by flow rate than conventional acids, flow rate cannot be ignored. As the flow rate increases, the acid rock reaction rate decreases, and uniform erosion occurs if the difference between the two is large. On the contrary, a lower flow rate can result in a higher acid rock reaction speed, and as the reaction proceeds, the acid rock reaction speed is greatly reduced due to the reduction of the acid liquor concentration, which is not beneficial to the expansion of the acid liquor in the rock. As the depth of the acidizing well increases, the formation temperature increases. The high temperature formation environment brings a series of problems to the temperature resistance of the construction liquid, especially the slowing and filtration of the acid liquor. Under the environment of a high-temperature stratum, the reaction speed of acid rocks is greatly increased, so that the stratum near the well is over-acidified, the deep part is not sufficiently acidified, and even the acidification operation fails when the deep part is serious. When the reservoir is acidized and reformed, liquid acid flows in a shaft, a crack and a pore space, and the reaction has obvious heat exchange with a stratum, so that the temperature of the system is greatly changed. The temperature change inevitably affects the rheological property of the liquid and the acid rock reaction rate, and finally affects the geometric dimension of earthworm holes, the effective acting distance of acid liquor and the like, thereby affecting the acidification effect. In addition, when carrying out conventional acidizing and acid injection construction, the construction rubs and hinders great, and is very high to construction equipment requirement, has restricted construction discharge capacity, has influenced effective earthworm hole working distance.
In order to solve the problems existing in the conventional acid acidification operation of the fracture-cavity oil reservoir and combine the characteristics of the common gas injection exploitation mode of the fracture-cavity oil reservoir, a construction method for acidifying the fracture-cavity oil reservoir by using atomized acid is provided. Compared with conventional acid, atomized acid is more beneficial to acidification of fracture-cavity oil reservoirs: (1) the leakage of the atomized acid is less, and the consumption of the acid liquid is far less than that of the liquid acid; (2) the atomized acid is more beneficial to wormhole perforation; (3) the reaction rate of the atomized acid rock is not influenced by the flow rate basically; (4) the high temperature condition is favorable for maintaining the stability of atomization; (5) when injecting acid, the atomized acid has small friction.
When atomized acid acidification operation is carried out on an oil field site, an atomization generating device is required to be used for atomizing acid liquor, and the atomization generating device with wider application can be divided into 2 types according to the atomization principle, namely an ultrasonic atomization generating device and a Venturi atomization generating device. The venturi atomization generating device has the main mechanism of a venturi injection principle, namely when fluid is injected, the flow speed of the high-speed fluid is sharply increased after the high-speed fluid passes through the venturi tube with variable diameter, the pressure is reduced, the diameter of a water mist cone sprayed out of the nozzle is gradually increased until the diameter of the water mist cone is equal to the inner diameter of the injection pipe, the water mist piston is changed into a cylindrical water mist piston due to the constraint of the injection pipe, and the water mist piston moves at a high speed along the injection pipe along with the spraying of the water mist from the nozzle and is sprayed out from an injection outlet at a high speed. Under the mutual action of liquid surface tension, viscous force and air resistance, the liquid is gradually changed from liquid drops to smooth flow and wavy flow, and finally mist flow is formed. Compared with other atomization generating devices, the venturi atomization generating device has the following advantages: (1) stable atomization effect: the atomized particles are fine and uniform, and the size of the atomized particles is stable in the whole liquid amount variation range; (2) the energy is remarkably saved: stable atomization can be realized under lower air pressure and water pressure, and energy consumption is low compared with a pressure jet type atomization generating device; (3) larger fluid flow adjustment range: by adjusting the pressure of liquid and gas, the amount of the spraying liquid can be continuously adjusted from zero to the maximum designed flow so as to adapt to frequent variable spraying working conditions; (4) excellent anti-clogging properties: the aperture of the nozzle is large, and the nozzle has good adaptability to impurity particles; (5) the product is purely mechanical, has no movable part, low failure rate, low cost and maintenance cost and long service life.
CN206596555U discloses a double-flow variable spray control device, which comprises a gas port, a nozzle, a liquid port, a liquid flowmeter, a liquid pressure gauge, a one-way valve, a liquid throttle valve, a water pump, a medicine chest, a liquid motor, a gas motor, an air compressor, a pressure regulating valve, a gas throttle valve, a gas pressure gauge, and a gas flowmeter. The device has gas circuit system and liquid circuit system, gas circuit system has air compressor, air-vent valve, gas throttle valve, gas pressure gauge, gas flowmeter, liquid system has medical kit, water pump, liquid throttle valve, check valve, liquid pressure gauge, liquid flowmeter, liquid motor connects in the liquid throttle valve, gas motor connects in the air-vent valve. The device is installed on the test platform, can carry out stable effectively spraying.
At present, the double-flow type venturi atomization device at home and abroad is mostly applied to the industries of medical treatment, agriculture, automobiles and the like, and the double-flow type pesticide spraying device disclosed in the Chinese patent document CN206596555U is applied to agricultural pesticide spraying. The principle of the device is similar to that of a double-flow type Venturi atomization generating device for acidizing fracture-cavity oil reservoirs, but the device is different in size and matched systems due to the difference between the agricultural environment and the oil field environment. The oil and gas well environment has the characteristics of high temperature and high pressure, so that the atomization generating device used in the oil field site is required to be capable of bearing larger temperature and pressure. In addition, the atomization generating device is applied to an acidification process of an oil field site, so that the atomization generating device has certain acid resistance, and HB series Hastelloy is selected as a material. The higher molybdenum and chromium content in the hastelloy enables the hastelloy to resist chloride ion corrosion, and the tungsten element further improves the corrosion resistance, so that the hastelloy has good acid resistance. The gas and liquid discharge capacity of the atomization generating device for the oil field is far higher than that of an agricultural atomization generating device, the melting point of the Hastelloy is 1300 ℃, the maximum pressure bearing can exceed 300MPa, and in actual field construction, the formation temperature of the well depth of 6000m is about 200 ℃, and the injection pressure of a well mouth is 30MPa, so that the atomization generating device made of the Hastelloy can bear larger gas and liquid discharge capacity. A atomizing generating device nozzle exit linkage well head for the oil field, atomizing acid flows to the target layer from top to bottom in the pit shaft, considers the problem of acidizing fluid wall built-up, and the device passes through venturi's cavitation, and broken liquid drop can reduce well bottom liquid deposit volume, improves the atomization rate.
Disclosure of Invention
In order to overcome the defects of the prior art, the invention provides an atomized acid shaft flow simulation device for gas injection development of a fracture-cavity oil reservoir and an evaluation method using the device.
An atomized acid shaft flow simulation device for gas injection development of a fracture-cavity oil reservoir comprises an atomization generation device, a shaft flow simulation device and an atomization evaluation device;
the atomization generating device comprises a gas path system, a liquid path system, an atomization generator and an observation system, wherein the gas path system, the liquid path system and the atomization generator are communicated in sequence; the atomization generator is a double-flow venturi tube; the gas path system provides gas with adjustable injection speed for the atomization generator; the liquid path system provides acid liquid with adjustable injection speed for the atomization generator; the atomization generator is used for mixing gas-liquid fluid and forming atomized acid;
the shaft flow simulation device comprises a vertical shaft, a horizontal simulation stratum and a liquid collection device; the vertical shaft is connected to the tail end of the atomization generating device, and atomized acid enters the vertical shaft from the tail end of the atomization generating device and vertically falls along the shaft; atomized acid enters a horizontal simulated formation through a vertical shaft and is used for simulating matrix acidification after the atomized acid enters the formation; the acid liquid which is not atomized falls into the accumulated liquid collecting device under the action of gravity, and the accumulated liquid collecting device is used for measuring the volume of the acid liquid which is not atomized; the shaft flow simulation device is connected with the atomization generator;
the atomization evaluation device comprises a nanometer laser particle size analyzer, and the atomization degree of the atomized acid is evaluated by measuring the particle size change of the atomized acid in the vertical shaft section in the simulated shaft.
The height of the atomization generator is 50-200mm, the inner diameter of a gas inlet is 20-40mm, and the diameter of a liquid inlet is 5-15 mm; preferably, the height of the atomization generator is 80-150mm, the inner diameter of the gas inlet is 30-35mm, and the diameter of the liquid inlet is 7-10 mm. The liquid outlet of the atomization generator is provided with 2-10 small holes, preferably 4-8 small holes, the diameter is 0.2-1.0mm, and the preferred diameter is 0.5-0.8 mm; the small hole is obliquely and downwards communicated with the cylindrical cavity. The length-diameter ratio of the double-flow Venturi tube is 3-6: 1; the preferred aspect ratio is 5.5: 1.
according to the optimization of the invention, the gas circuit system comprises an air compressor, a gas throttle valve and a gas pressure gauge, wherein the air compressor is connected with a gas pipeline for the atomization generator, the gas throttle valve and the gas pressure gauge are arranged on the pipeline, the gas throttle valve is used for controlling the gas injection speed, and the gas pressure gauge is used for measuring the gas injection pressure.
According to the invention, the liquid system comprises a high-pressure acid-resistant pump, a liquid throttling valve and a liquid pressure gauge, the high-pressure acid-resistant pump is connected with the air pipeline for the atomization generator, the liquid throttling valve and the liquid pressure gauge are arranged on the pipeline, the liquid throttling valve is used for controlling the acid liquid injection speed, and the liquid pressure gauge is used for measuring the acid liquid injection pressure.
Preferably, according to the invention, the gas inlet of the atomization generator is connected with an air compressor, the liquid inlet is connected with a high-pressure acid-resistant pump, and the double-flow outlet is connected with the well bore. The atomization generator is internally provided with an annular cavity for accumulating acid liquor, and the acid liquor in the annular space enters the central cylindrical cavity through the pores on the wall. When the atomization generator injects fluid, the speed of the high-speed fluid is sharply increased and the pressure is reduced after the high-speed fluid passes through the reducing of the venturi tube; after acid liquor is injected from the liquid injection port, acid mist is formed in the cylindrical cavity under the action of hydrodynamic cavitation, the acid mist is restrained by the cylindrical cavity to form an acid mist piston, and the acid mist piston moves at a high speed in the atomization generator and is finally sprayed out from the double-flow outlet. In the process, under the mutual action of the surface tension, the viscosity and the air resistance of the liquid, the liquid is gradually changed from a smooth flow to a fog flow.
A method for carrying out acid liquor atomization evaluation by using the device comprises the following steps:
(1) controlling gas flow rate by an air compressor and liquid flow rate by a high-pressure acid-resistant pump at normal temperature and normal pressure, injecting fluid and gas with constant flow rate into a double-flow Venturi atomization generator, wherein the volume of the injected liquid in every minute is VlVolume of gas is Vg；
(2) Observing whether an atomized flow is generated at the outlet end of the double-flow type Venturi atomization generator; if no mist flow is generated, continuously changing the gas injection flow velocity range until finding out the flow velocity limit generated by the mist flow, and recording the degree of a gas injection port pressure gauge and the reading of a liquid injection port pressure gauge;
(3) after stable mist flow is generated, collecting liquid in the shaft in unit time T at the bottom of the simulated shaft by using a liquid collection device, and recording the volume as VcCalculating the atomization rate and the liquid-gas mass ratio;
(4) changing the ratio of injected gas to liquid within the flow velocity limit generated by the mist flow, and observing the change of the atomized particle size and the liquid drop coalescence condition in the liquid collection device by using a nano laser particle size analyzer;
(5) in the experimental process, the atomization effect is judged by the atomization particle size, the atomization rate and the liquid drop coalescence accumulated liquid volume.
The HCl solution with the acid liquor concentration of 20 wt% has the relative density of 1.09g/cm3. The liquid and gas with constant flow rate are injected into the double-flow Venturi atomization generator, and the volume V of the injected liquid is measured in unit time t (min)l＝QlX t (mL), gas volume Vg＝Qg×t(m3)，；
Collecting the volume V of the effusion in the shaft in unit time t by the effusion collecting device in the step (3)c＝QcX t (mL), the atomization rate is calculated by the formula
Mass ratio of liquid to gas
In the actual construction process of the oil field, due to the underground high-temperature and high-pressure environment, the acid liquid attached to the pipe wall can be further gasified and enter the stratum, so that the atomization rate of the oil field site needs to be corrected according to the difference between the laboratory condition and the oil field environment. The number of molecules condensed per unit time to the surface of the liquid is expressed in terms of the molecular flux J of the saturated vapor. u is the evaporation rate of the liquid and represents the volume of liquid evaporated from the surface of the liquid per unit time.
Considering saturated steam as ideal gas, the pressure of saturated steam is p, the thermodynamic temperature is T, the average velocity of molecules is v, and the number density of molecules is ngDensity of rhogThe molecular mass is m, the molar mass is mu, and the molecular number density of the acid solution is nlDensity of rholWhere the constant of the universal gas is R, then there are
Therefore, in the actual oilfield field, due to the introduction of the evaporation rate u, the atomization rate of the acid liquid on the field is increased to
According to the invention, the observation system is preferably a nanometer laser particle size analyzer and is used for observing the particle size change of the atomized acid in the vertical shaft section in the simulated shaft. The principle is that when a light beam is blocked by liquid particles, a part of the light is scattered, and the propagation direction of the scattered light forms an included angle theta with the propagation direction of a main light beam. The magnitude of the scattering angle θ is related to the size of the particles, with larger particles producing smaller scattering light angles θ; the smaller the particle, the larger the angle theta of the scattered light produced. The particle size measurement is used for evaluating the atomization acid atomization degree.
The invention has the beneficial effects that:
1. the atomized acid shaft flow simulation platform for gas injection development of the fracture-cavity oil reservoir comprises a double-flow Venturi atomization generating device, a shaft flow simulation device and an atomization evaluation device, and can simulate the process of flow of acid liquid in a near-wellbore zone after the acid liquid is atomized into a shaft in actual operation of an oil field under laboratory conditions;
2. the double-flow type Venturi atomization generating device has a good atomization effect, atomized particles are fine and uniform, stable atomization can be realized under lower air pressure and water pressure, and energy consumption is low; the anti-blocking nozzle has excellent anti-blocking performance, large aperture, good adaptability to impurity particles and low failure rate, and is suitable for various types of well construction operation;
3. the invention controls the injection discharge capacity through a gas-liquid path system, keeps higher acid liquid atomization rate according to the site construction requirement, and evaluates the acid liquid atomization degree by using a nano laser particle size analyzer and an accumulated liquid collecting device;
4. the invention can also add an atomization stabilizer into the acid liquor, reduce the coalescence and deposition of the atomized acid in the karst caves of the fracture-cavity type oil reservoir, improve the atomization effect and fill the blank of acid liquor atomization research in the field of acidification of oil and gas wells.
Drawings
FIG. 1 is a block diagram of the structure of an atomized acid wellbore flow simulation platform for gas injection development of fracture-cavity reservoirs according to the present invention;
FIG. 2 is a schematic diagram of the construction of the atomizing generator of the present invention;
FIG. 3 is a schematic structural diagram of an improved double-flow venturi atomization generating device;
FIG. 4 is a graph of spray cross-sectional area versus atomization rate.
1. The device comprises an air compressor, 2, a gas throttling valve, 3, a gas pressure gauge, 4, a high-pressure acid-resistant pump, 5, a liquid pressure gauge, 6, a liquid throttling valve, 7, an atomization generating device, 8, a simulation shaft, 9, a horizontal simulation stratum, 10, a liquid accumulation collecting device, 11, a nanometer laser particle size analyzer, 12, a cylindrical cavity, 13, a liquid inlet, 14, an annular cavity, 15, a double-flow outlet, 16, a liquid outlet, 17, a gas inlet, 18, a venturi tube, 19, a liquid inlet with the diameter of 8-phi 0.5mm, 20 and an atomization nozzle.
Detailed Description
The invention is further defined in the following, but not limited to, the figures and examples in the description.
Example 1
An acid liquor atomization-shaft flow simulation platform for deep acidification of a fracture-cavity oil reservoir is shown in figure 1 and comprises a gas path system, a liquid path system, an atomization generator, a shaft flow simulation device and an acid liquor atomization evaluation device.
The gas circuit system comprises an air compressor 1, a gas throttle valve 2 and a gas pressure gauge 3, wherein the air compressor provides gas with adjustable injection speed for the atomization generating device, the gas throttle valve is used for controlling the gas injection speed, and the gas pressure gauge is used for measuring the gas injection pressure.
The liquid path system comprises a high-pressure acid-resistant pump 4, a liquid pressure gauge 5, a liquid throttle valve 6 and an acid-resistant pump, wherein the high-pressure acid-resistant pump provides acid liquid with adjustable injection speed for the double-flow venturi atomization generating device, the liquid pressure gauge is used for measuring liquid injection pressure, and the liquid throttle valve is used for controlling the liquid injection speed.
The height of the atomization generating device is 7mm, the height of the gas inlet part is 32mm, the inner diameter is 28mm, the outer diameter is 32mm, the diameter of the liquid inlet part is 8mm, the diameter of the liquid outlet part is 0.5mm, and the total sectional area is 0.785mm2The inner diameter of the double-flow outlet part is 44mm, and the outer diameter of the double-flow outlet part is 56 mm. The gas inlet is connected with an air compressor, the liquid inlet is connected with a high-pressure acid-resistant pump, and the double-flow outlet is connected with a shaft 8.
The shaft in the simulated shaft flow device is made of a plexiglas pipe, the diameter of the shaft is 30mm, and the length of the shaft is 6 m.
The acid liquor atomization evaluation device uses a nanometer laser particle size analyzer to observe the particle size of the atomized acid in the middle section of the simulated shaft; and measuring the volume of the accumulated liquid in the accumulated liquid collecting device at the bottom of the simulated shaft, and evaluating the atomized acid by the measured data of the two.
Example 2
Setting the initial flow rate of gas to 1.0m3The initial injection speed of the fluid is 40mL/min, and the atomization rate under the conditions is calculated by changing the gas-liquid ratio under different conditions and is shown in the following table 1.
TABLE 1 initial experimental data record table
The serial number 1 is used as an experimental control group, and the liquid flow rate and the gas flow rate are respectively changed by controlling variables. As a result of comparison among the numbers 1, 4 and 7, the gas flow rates were changed to 0.5m when the liquid flow rates were kept constant at 40mL/min3/min、1m3/min、2m3The atomization rate increases from 4.00% to 33.33% with increasing liquid-gas ratio.
Table 1 the atomization effect of the double flow venturi atomization generator is relatively low. Therefore, by the atomization principle of the Venturi tube, the atomization rate of the atomization device can be improved by reducing the sectional area of liquid injection.
The liquid jet cross-sectional area is changed from 0.7850mm2This resulted in 0.3925mm2 and 0.196mm2, and the data obtained in Table 2 are shown.
TABLE 2 Experimental data record sheet for atomization generator
By comparing the experimental data table 2 with table 1, it was found that the liquid atomization rate was increased. This is because the fluid ejection area is reduced and the inlet-end liquid pressure is increased, so that the degree of liquid breakup by the gas is increased and the atomization rate is increased.
Therefore, when the acidizing fluid atomization device is used for determining the acidification of the oil field, in order to ensure the atomization rate and the acidizing fluid injection volume at the same time, the optimal limit of the mist flow is that the gas injection speed is 1.0m3/min, and when the liquid injection speed is 20mL/min, the atomization rate is 76.67%, so that the oil field acidification device has relatively good atomization performance. Has the advantages of stable atomization effect, fine atomized particles, large fluid flow adjustment range and good anti-blockage performance.
At a gas flow rate Qg1.0m3/min, acid flow rate QLThe atomization rate at 40mL/min is plotted on the abscissa and the injection cross-sectional area is plotted on the ordinate, and the injection cross-sectional area-atomization relationship curve shown in fig. 4 is obtained.
As can be seen from fig. 4, the atomization rate increases with the decrease of the jet cross-sectional area, because the decrease of the jet cross-sectional area can increase the hydrodynamic cavitation, but the smaller the cross-sectional area is, the better the cross-sectional area is, the too small cross-sectional area will cause the acid liquid injection pressure to be too high, the higher the pressure bearing capacity of the device is required, and the pumping is not beneficial.
Example 3
As can be seen from example 1, the atomization rate can be increased by changing the acid liquid injection cross-sectional area, but the pressure at the acid liquid injection port is also increased, which easily causes damage to the equipment. Therefore, the atomization rate cannot be increased by merely reducing the cross-sectional area of the acid liquid spray, and other methods should be selected to improve the atomization generation device. Example 3 an atomization nozzle was modified by redesigning the acid injection port using a narrower venturi channel.
The improved double-flow Venturi atomization generating device is 120mm high, the gas inlet part is 40mm high, the inner diameter is 20mm, the outer diameter is 32mm, the liquid inlet part is 8mm in diameter, the liquid outlet part is 0.5mm in diameter, and the total sectional area is 1.57mm2The length of the double-flow outlet atomizing nozzle is 53mm, and the inner diameter of the outlet end of the atomizing nozzle is 7 mm.
Compared with the original atomization generating device, the improved double-flow type Venturi atomization generating device has the advantages that the atomization nozzle is added at the double-flow type outlet end, the atomization nozzle is designed to be conical, the cylindrical collider is further added at the top of the conical nozzle, when atomized acid enters the atomization nozzle from the double-flow type outlet, the conical atomization nozzle is gradually reduced due to the fact that the fluid channel is gradually reduced, the flow rate of the fluid inside is gradually increased, after the increased fluid is sprayed out of the atomization nozzle, the cylindrical collider is collided to enable the liquid drops to be further broken into small liquid drops, and the atomization rate at the outlet end is further improved. Meanwhile, the outlet of the cone nozzle is a 30-degree acute angle and extends into the shaft, and atomized acid is sprayed out through the cone nozzle, so that the adhesion of liquid drops on the inner wall of the oil pipe and accumulated liquid at the bottom of the shaft can be reduced, and the stable flow of the atomized acid in the shaft is realized.
Therefore, the double-flow venturi atomization generator redesigned in the embodiment 3 has better atomization effect and coalescence prevention measure, is more suitable for field use, and has good feasibility compared with the original double-flow venturi atomization generator.
The above examples are only for illustrating the technical solutions of the present invention, and are not limited thereto. Although the present invention has been described in detail with reference to the foregoing embodiments, it will be understood by those of ordinary skill in the art that: the technical solutions described in the foregoing embodiments may still be modified, or some technical features may be equivalently replaced; and such modifications or substitutions do not depart from the spirit and scope of the corresponding technical solutions of the embodiments of the present invention.
Claims (7)
1. An atomized acid shaft flow simulation device for gas injection development of a fracture-cavity oil reservoir comprises an atomization generation device, a shaft flow simulation device and an atomization evaluation device;
the atomization generating device comprises a gas path system, a liquid path system, an atomization generator and an observation system, wherein the gas path system, the liquid path system and the atomization generator are communicated in sequence; the atomization generator is a double-flow venturi tube; the gas path system provides gas with adjustable injection speed for the atomization generator; the liquid path system provides acid liquid with adjustable injection speed for the atomization generator; the atomization generator is used for mixing gas-liquid fluid and forming atomized acid;
the shaft flow simulation device comprises a vertical shaft, a horizontal simulation stratum and a liquid collection device; the vertical shaft is connected to the tail end of the atomization generating device, and atomized acid enters the vertical shaft from the tail end of the atomization generating device and vertically falls along the shaft; atomized acid enters a horizontal simulated formation through a vertical shaft and is used for simulating matrix acidification after the atomized acid enters the formation; the acid liquid which is not atomized falls into the accumulated liquid collecting device under the action of gravity, and the accumulated liquid collecting device is used for measuring the volume of the acid liquid which is not atomized; the shaft flow simulation device is connected with the atomization generator;
the atomization evaluation device comprises a nanometer laser particle size analyzer, and the atomization degree of the atomized acid is evaluated by measuring the particle size change of the atomized acid in a vertical shaft section in the simulated shaft;
the height of the atomization generator is 50-200mm, the inner diameter of a gas inlet is 20-40mm, and the diameter of a liquid inlet is 5-15 mm;
the atomizing nozzle is conical, the top of the atomizing nozzle is also provided with a cylindrical collider, the flow rate of the acid liquid is gradually increased after the acid liquid enters the atomizing nozzle, and after the acid liquid is sprayed out of the atomizing nozzle, the cylindrical collider is collided to further break the liquid drops into small liquid drops, so that the atomization rate at the outlet end is further improved;
the outlet of the atomizing nozzle forms an included angle of 30 degrees and extends into the shaft, and atomized acid is sprayed out through the nozzle, so that the adhesion of liquid drops on the inner wall of the oil pipe and accumulated liquid at the bottom of the shaft can be reduced, and the stable flow of the atomized acid in the shaft is realized;
the liquid outlet of the atomization generator is provided with 2-10 small holes with the diameter of 0.2-1.0 mm; the small hole is obliquely and downwards communicated with the cylindrical cavity.
2. The apparatus of claim 1, wherein the aerosol generator has a height of 80-200mm, a gas inlet inner diameter of 30-35mm, and a liquid inlet diameter of 7-10 mm.
3. The apparatus of claim 1, wherein the liquid outlet of the atomizing generator has 4-8 orifices with a diameter of 0.5-0.8 mm.
4. The apparatus of claim 1, wherein the double flow venturi has a length to diameter ratio of 3-6: 1.
5. the apparatus of claim 1, wherein the double flow venturi has a length to diameter ratio of 5.5: 1.
6. a method for acid atomization evaluation using the device of any of claims 1-5, comprising the steps of:
(1) controlling gas flow rate by an air compressor and liquid flow rate by a high-pressure acid-resistant pump at normal temperature and normal pressure, injecting fluid and gas with constant flow rate into a double-flow Venturi atomization generator, wherein the volume of the injected liquid in every minute is VlVolume of gas is Vg；
(2) Observing whether an atomized flow is generated at the outlet end of the double-flow type Venturi atomization generator; if no mist flow is generated, continuously changing the gas injection flow velocity range until finding out the flow velocity limit generated by the mist flow, and recording the degree of a gas injection port pressure gauge and the reading of a liquid injection port pressure gauge;
(3) after stable mist flow is generated, collecting liquid in the shaft in unit time T at the bottom of the simulated shaft by using a liquid collection device, and recording the volume as VcCalculating the atomization rate and the liquid-gas mass ratio;
(4) changing the ratio of injected gas to liquid within the flow velocity limit generated by the mist flow, and observing the change of the atomized particle size and the liquid drop coalescence condition in the liquid collection device by using a nano laser particle size analyzer;
(5) in the experimental process, the atomization effect is judged by the atomization particle size, the atomization rate and the liquid drop coalescence accumulated liquid volume.
7. The method of claim 6, wherein the volume of fluid present in the well bore per unit time t collected at the fluid collection device site in step (3) is Vc＝QcX t (mL), the atomization rate is calculated by the formula
Mass ratio of liquid to gas
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