Nano-bubble galloping oil displacement method and system

Abstract

The invention belongs to the technical field of oil and gas field development engineering, and discloses a nanobubble galloping oil displacement method and system.The method comprises the steps that nanobubbles are prepared in the environment matched with reservoir pressure by obtaining target oil reservoir parameters; establishing a particle size-concentration-adsorption loss evaluation chart through an adsorption loss experiment; based on the reservoir starting pressure gradient, pulse injection parameters, including reference pressure, pulse amplitude and frequency, of the nanobubbles are determined through numerical simulation optimization; and executing mine field injection according to the pulse injection parameters, and performing iterative optimization on the nanobubble property and the injection scheme according to the development dynamic monitoring result. Gas is injected into the ground in the form of nano bubbles, so that the interfacial tension is reduced while gas channeling is inhibited, and the oil washing efficiency is improved; a pulse type injection method is adopted, disturbance of injected fluid to the remaining oil of the reservoir is enhanced, and sweep is expanded; the nano-bubble galloping effect is excited through hydraulic pulse, the rock wall surface crude oil stripping rate is increased, and the crude oil recovery rate is increased.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of oil and gas field development engineering, and particularly relates to a nano-bubble fluttering oil displacement method and system. BACKGROUND

[0002] Water flooding is still the main way of crude oil development. After long-term water injection development, most oil reservoirs have entered the high water cut or even ultra-high water cut stage. However, long-term water flooding development leads to the formation of numerous dominant channels in the reservoir, and the remaining oil shows the distribution characteristics of "high dispersion and local enrichment". It is difficult to drive with conventional water flooding, and the problem of ineffective circulation is prominent. In the existing enhanced oil recovery technology, foam flooding and micro-bubble flooding can increase the percolation resistance and expand the swept volume through the "Jamin effect", thereby improving the oil recovery. However, the stability is restricted by high temperature and high salt formation conditions, and water-gas separation easily occurs during migration in porous media, resulting in "channeling" phenomenon. At the same time, due to the size limitation, it is difficult to enter the small pores, and the remaining oil stored therein cannot be effectively produced.

[0003] The existing Chinese patent: a method for improving oil recovery, application number: 202310240731.2, application date: March 14, 2023, the method comprises the following steps: determining the size of micro-nano bubbles and the volume percentage of micro-nano bubbles in the first injection fluid according to the formation characteristics, and then preparing the first injection fluid containing micro-nano bubbles; injecting the first injection fluid containing micro-nano bubbles into the formation to carry out displacement operation.

[0004] The existing Chinese patent: a water-gas dispersion system oil displacement system and method, application number: 201811031150.3, application date: March 9, 2021, the system comprises a micro-bubble generating device, a gas source, an ultrasonic oscillation controller, a protection cylinder, and a support; a first opening is formed at the top end of the protection cylinder for the internal device to enter and exit, and the first opening is sealed by an end cover; a second opening is formed in the side wall of the protection cylinder and communicates with the water injection pipeline for the entry and exit of fluid; the micro-bubble generating device is fixed in the protection cylinder through the support; the gas source is connected with the micro-bubble generating device through a gas pipeline for supplying gas to the micro-bubble generating device; the ultrasonic oscillation controller is connected with the micro-bubble generating device through a signal line for controlling the micro-bubble generating device to generate micro-bubbles.

[0005] However, the above-mentioned technology has two big problems: first, in high water cut and ultra-high water cut reservoirs, the dominant channels in the reservoir are developed, and the dispersed remaining oil is difficult to produce; second, the application effect of foam flooding and micro-bubble flooding and other technologies is limited due to the limitation of reservoir conditions. Therefore, a new oil displacement method is urgently needed.

[0006] Through the above analysis, the problems and defects of the prior art are: the conventional water drive is difficult to operate, the macro displacement efficiency is low, and the micro oil washing efficiency is limited; the foam drive and the micro bubble drive have poor temperature resistance and salt resistance, are prone to gas-liquid separation to cause "channeling", are difficult to effectively drive the remaining oil in the small pores due to size limitation, and have the risk of reservoir damage. SUMMARY

[0007] In view of the problems in the prior art, such as displacement phase channeling along high permeation channels, serious inefficient circulation, limited application effect under high temperature and high salt reservoir conditions, and low remaining oil production efficiency, the present application provides a nano bubble vibration driving oil method and system, and the technical solution is as follows: The present application is implemented in the following manner: a nano bubble vibration driving oil method, which excites the vibration effect of nano bubbles through periodic hydraulic pulse, specifically includes the following steps: S1, parameter acquisition: determining target reservoir parameter, well deployment condition and development dynamic; S2, preparing nano bubbles according to target reservoir conditions: determining nano bubble preparation environment pressure, nano bubble preparation pressure difference according to target reservoir temperature and pressure conditions, and completing nano bubble preparation; S3, nano bubble performance evaluation: calculating nano bubble adsorption loss, determining the minimum concentration value under different particle sizes, and establishing a particle size-concentration-adsorption loss evaluation chart; determining whether the nano bubble particle size, concentration and stability meet the expected performance requirements; if not, adjusting the nano bubble preparation pressure difference; S4, pulse injection parameter optimization: based on the starting pressure gradient of the target reservoir, the injection reference pressure, pulse amplitude and frequency of the periodic hydraulic pulse are determined through numerical simulation optimization; S5, pulse oil displacement and optimization: performing nano bubble field injection with the optimized pulse injection parameters, and when the water cut rises to 98%, triggering iterative optimization of the nano bubble properties and pulse injection parameters.

[0008] In step S1, the target reservoir parameter includes: target reservoir porosity, permeability, temperature, salinity, formation pressure, formation fracture pressure, crude oil viscosity and crude oil density.

[0009] In step S2, the nano bubbles are prepared by converting gas into nano bubbles existing in water through membrane dispersion.

[0010] Further, the nano bubble preparation environment pressure is equal to the target reservoir pressure.

[0011] In step S3, the particle size-concentration-adsorption loss evaluation chart is established, including: High-resolution CT scanning equipment was used to scan the core samples and SPG membrane of the target reservoir, extracting their respective pore distribution curves and obtaining the median pore diameter of the core samples. Porosity ,density Compared with macroscopic pore specific surface area and the median pore diameter of the SPG membrane Among them, the macroscopic pore size is greater than 200 nm; Median pore diameter of SPG membrane As the lower limit of the average particle size of nanobubbles The median pore diameter of the SPG membrane As the upper limit of the average particle size of nanobubbles Within the upper and lower limit range, eight values ​​were selected logarithmically to represent the average particle size of the nanobubbles. Five injection concentrations were set for each target particle size. They are respectively: , , , , Nanobubbles with different average particle sizes and concentrations were prepared.

[0012] Furthermore, the nanobubble particle size, concentration, and stability were determined to meet the expected performance requirements. This included conducting single-core nanobubble injection experiments with an injection volume of 10 PV. Samples were taken every 0.1 PV in the PV range of 0-3 PV, every 0.2 PV in the PV range of 3-6 PV, and every 0.5 PV in the PV range of 6-10 PV, to obtain the nanobubble concentration in the produced fluid at different injection volumes. Calculate the adsorption loss of nanobubble concentration for different injection volumes in each experimental group. ; ; In the formula, The concentration of nanobubbles before injection. The concentration of nanobubbles in the extracted fluid; Plotting the injection volume on the x-axis and adsorption loss on the y-axis, curves showing the relationship between the injection volume and adsorption loss for various average particle sizes and concentrations were generated. If the adsorption loss gradually decreases below 5% with increasing injection volume, then the concentration at that particle size meets the requirements for nanobubble vibration-driven oil displacement. If the adsorption loss consistently exceeds 5%, then the concentration at that particle size does not meet the requirements for nanobubble vibration-driven oil displacement. This process allows for the determination of the minimum concentration values ​​required to satisfy nanobubble vibration-driven oil displacement for different particle sizes. Establish a particle size-concentration-adsorption loss evaluation chart.

[0013] Determining the average particle size of nanobubbles and concentration average particle size satisfy ,concentration Based on the particle size-concentration-adsorption loss evaluation chart, it meets the requirements. ; The nanobubbles were aged for 24 hours under the target reservoir, temperature, and salinity conditions. The concentration and particle size of the nanobubbles were measured again, and the nanobubble stability factor was calculated. The expression is: ; In the formula, Factors affecting the concentration change of nanobubbles Factors affecting the variation of nanobubble particle size This represents the concentration of nanobubbles after aging. The average particle size of the nanobubbles after aging.

[0014] In step S4, the injection reference pressure, pulse amplitude, and frequency of the periodic hydraulic pulse are determined, including: The initiation pressure gradient of the target reservoir was obtained based on core displacement experiments. A numerical simulation model of the reservoir was established based on real geological parameters; different injection reference pressures were set. Pulse amplitude and frequency Orthogonal experiments were conducted, and the selection of the injection reference pressure and pulse amplitude satisfied the following formula: ; In the formula, For formation fracture pressure, The original formation pressure, To initiate pressure; The statistical maximum pressure gradient is greater than Number of grids Number of grids with pressure fluctuations and the total number of grids for the target reservoir Calculate the pressure-pulse spread coefficient of nanobubble vibration-driven oil. The expression is: ; In the formula, For pressure expansion weighting coefficients, This is the pulse spread factor; Pressure-pulse spread coefficient of nanobubble vibration-driven oil Maximum injection reference pressure Pulse amplitude and frequency As actual production injection parameters.

[0015] In step S5, iterative optimization of the properties of the nanobubbles and the pulse injection parameters is triggered, including: exciting the nanobubbles to vibrate by using the hydraulic pulse, and using a periodic nanobubble high-low pressure alternating injection mode: in the high pressure injection stage, the injection pressure is , the injection time is , in the low pressure injection stage, the injection pressure is , and the injection time is .

[0016] Another object of the present application is to provide a nanobubble vibration oil displacement system, which is realized by the nanobubble vibration oil displacement method, and the system comprises: A parameter acquisition module is configured to determine target reservoir parameters, well deployment conditions and development dynamics. A nanobubble preparation module is configured to prepare nanobubbles according to target reservoir conditions: according to the target reservoir temperature and pressure conditions, the nanobubble preparation environment pressure and the nanobubble preparation pressure difference are determined, and the preparation of the nanobubbles is completed. A performance evaluation module is configured to calculate the adsorption loss of the nanobubbles, determine the minimum concentration value under different particle sizes, and establish a particle size-concentration-adsorption loss evaluation chart; whether the particle size, concentration and stability of the nanobubbles meet the expected performance requirements is determined; if not, the nanobubble preparation pressure difference is adjusted. An injection parameter optimization module is configured to determine the injection reference pressure, pulse amplitude and frequency of the periodic hydraulic pulse by numerical simulation optimization based on the starting pressure gradient of the target reservoir. A field injection scheme execution and optimization module is configured to execute the nanobubble field injection with the optimized pulse injection parameters, and when the water cut rises to 98%, iterative optimization of the properties of the nanobubbles and the pulse injection parameters is triggered.

[0017] In combination with all the technical solutions described above, the present application has the following beneficial effects: Firstly, the present application uses physical means such as membrane dispersion and mechanical shearing to convert gas into nanoscale bubbles existing in water, which has the characteristics of long existence time, strong temperature and salt resistance, large specific surface area, etc., and after being injected into the underground, it is adsorbed on the rock wall surface and the oil-water interface, combined with the pulse injection method, the disturbance of the injected fluid to the remaining oil in the reservoir is enhanced and the sweep is expanded, at the same time, the nanobubble vibration effect is excited, which makes the nanobubbles slip at the interface and accelerate the oil stripping rate of the rock wall surface, thereby improving the oil washing efficiency. This method can effectively improve the development effect of high and ultra-high water cut reservoirs and further improve the oil recovery rate in the late water flooding development.

[0018] Secondly, the application injects gas in the form of nanobubbles into the underground, suppresses "gas channeling", reduces interfacial tension, and improves oil washing efficiency; the pulse injection method is adopted to enhance the disturbance of the injected fluid to the remaining oil in the reservoir and expand the sweep; the nanobubbles are excited by the hydraulic pulse to generate the vibration effect, so that the nanobubbles slip at the interface and the oil stripping rate of the rock wall is accelerated, and the oil recovery is further improved. Based on the interfacial effect generated by the unique physical and chemical properties of the nanobubbles and the dynamic effect generated by the intermittent pulse injection of the external fluid, the oil displacement efficiency is synergistically enhanced, the oil washing effect of the reservoir is significantly improved, and the theoretical basis and technical support can be provided for the field application of the technology.

[0019] Thirdly, the application excites the vibration effect of the nanobubbles by the hydraulic pulse to form the nanobubble vibration oil displacement technology, which can effectively improve the oil recovery of the high water cut reservoir. The indoor physical simulation experiment results show that the recovery rate can be increased by more than 10% in the block with a water content of more than 90%; compared with the conventional chemical flooding technology, the operation cost of the technology is significantly reduced, and there is no risk of chemical residue and formation damage, so the technology has a wide application prospect in the development, quality improvement and efficiency improvement of high water cut oilfields. The application first combines the interface regulation and the seepage field regulation of the nanobubbles with the vibration effect excited by the hydraulic pulse to propose a new method of nanobubble vibration oil displacement, so as to synergistically expand the swept volume and improve the oil washing efficiency, and effectively improve the recovery of the high water cut reservoir.

[0020] Fourthly, in view of the development problems of the high water cut reservoir, such as the development of the dominant channel, the dispersion of the remaining oil and the difficulty in effective utilization, and the application effect of the existing technologies such as foam flooding and microbubble flooding is limited due to the restriction of the reservoir conditions, the application proposes to excite the vibration effect of the nanobubbles by the periodic hydraulic pulse, fully play the role of the nanobubbles in the interface regulation and the seepage field regulation, combine the enhanced utilization mechanism of the vibration effect on the remaining oil, expand the swept volume and improve the oil washing efficiency, and realize the effective utilization of the remaining oil in the high water cut reservoir. BRIEF DESCRIPTION OF DRAWINGS

[0021] The accompanying drawings, which are incorporated into and form part of the specification, illustrate embodiments consistent with the present disclosure and, together with the specification, serve to explain the principles of the present disclosure; Figure 1 is a flow chart of the nanobubble vibration oil displacement method provided by the embodiment of the application; Figure 2 is a line diagram of the nanobubble vibration oil displacement method provided by the embodiment of the application; Figure 3 is a schematic diagram of the particle size-concentration-adsorption loss evaluation chart provided by the embodiment of the application; Figure 4 is a water content curve diagram of the core displacement comparison experiment provided by the embodiment of the application; Figure 5 is a recovery curve diagram of a core displacement contrast experiment provided by an embodiment of the present application. DETAILED DESCRIPTION

[0022] In order to make the above objectives, characteristics and advantages of the present application more apparent, specific embodiments of the present application are described in detail below with reference to the accompanying drawings. In the following description, a large number of specific details are set forth in order to provide a thorough understanding of the present application. However, the present application can be implemented in many different ways than those described herein, and those skilled in the art can make similar improvements without departing from the scope of the present application, so the present application is not limited to the specific implementations disclosed below.

[0023] The innovation of the present application is that the present application proposes a new oil displacement method based on the "nano-bubble galloping effect", which excites the periodic oscillation, migration and non-steady growth of nano-bubbles through an external force field (an alternating pressure field generated by pulse injection), and generates micro-jets and local high temperature, thereby effectively stripping the crude oil film attached to the rock surface and promoting the emulsification of crude oil, and then improving the flowability of crude oil and increasing the recovery rate; a physical oil displacement system of pulse injection and nano-bubble synergistic effect is constructed, realizing the organic combination of macroscopic sweep range regulation and microscopic oil washing efficiency enhancement, and without adding chemical agents in the process of nano-bubble preparation and oil displacement, effectively avoiding the reservoir damage and environmental problems caused by chemical agents, and providing a feasible enhanced oil recovery technology approach for high-temperature, high-salinity and high-water-cut reservoirs.

[0024] In Example 1, as shown in Figure 1 and Figure 2 , the nano-bubble galloping oil displacement method provided by the embodiment of the present application includes the following steps: S1, parameter acquisition: determining the target reservoir parameter, well deployment condition and development dynamic; The target reservoir porosity is 21.4%, the permeability is 343x10 3 μm 2 , the core sample density is 2.60g / cm 3 , the formation temperature is 82℃, the salinity is 12000mg / L, the formation pressure is 24.3MPa, the formation fracture pressure is 39MPa, the starting pressure is 2.26MPa, the crude oil viscosity is 25mPa·s, and the crude oil density is 0.84g / cm 3 .

[0025] S2, preparing nano-bubbles according to the target reservoir condition: determining the nano-bubble preparation environmental pressure and the nano-bubble preparation pressure difference according to the target reservoir temperature and pressure condition, and completing the preparation of nano-bubbles; Nanobubbles were prepared by membrane dispersion. The membrane used was a tubular SPG membrane with an outer diameter of 5 mm, a thickness of 0.4 mm, and a length of 100 mm. The ambient pressure during preparation was 24.3 MPa, and the pressure difference during nanobubble preparation was 0.08 MPa.

[0026] S3, Nanobubble Performance Evaluation: Calculate the adsorption loss of nanobubbles, determine the minimum concentration value under different particle sizes, and establish a particle size-concentration-adsorption loss evaluation chart; determine whether the nanobubble particle size, concentration, and stability meet the expected performance requirements; if not, adjust the nanobubble preparation pressure difference; Typical permeability adsorption loss experiments were conducted in the target reservoir using nanobubbles. The adsorption loss of nanobubbles was calculated, the minimum concentration value under different particle sizes was determined, and a particle size-concentration-adsorption loss evaluation chart was established.

[0027] High-resolution CT scanning equipment was used to scan the core samples and SPG membrane of the target reservoir, extract the pore distribution curves of each sample, and measure the median pore diameter of the core samples. 800nm, porosity The specific surface area of ​​macroscopic pores (greater than 450 nm) is 21.4%. It is 19.47cm 2 / g, median pore diameter of SPG membrane The lower limit of the average particle size of nanobubbles is 100 nm. The upper limit of the average particle size of nanobubbles is 100 nm. The target average particle size of the nanobubbles is 800 nm. Within this range, eight values ​​are selected logarithmically and uniformly as the average particle size of the nanobubbles. The particle sizes were 100nm, 134.59nm, 181.15nm, 243.80nm, 328.13nm, 441.64nm, 594.40nm, and 800nm, with five injection concentrations set for each target particle size. They are respectively: , , , , Nanobubbles with different average particle sizes and concentrations were prepared. The concentrations corresponding to each particle size are shown in Table 1.

[0028] Table 1. Experimental pressure-pulse spread coefficient for each group.

[0029] Based on the above parameters, different average particle sizes and different concentrations of nanobubbles are prepared, and based on the target reservoir temperature, pressure and salinity conditions, single-core nanobubble injection experiments are carried out, the injection amount is 10 PV, when the injection PV interval is 0-3 PV, sampling is taken every 0.1 PV, when the injection PV interval is 3-6 PV, sampling is taken every 0.2 PV, and when the injection PV interval is 6-10 PV, sampling is taken every 0.5 PV, and the concentration of nanobubbles in the produced fluid at different injection amounts is obtained , the nanobubble concentration adsorption loss of each group experiment at different injection amounts is calculated : ; In the formula, is the concentration of nanobubbles before injection, 10 7 per mL; is the concentration of nanobubbles in the produced fluid, 10 7 per mL; With the injection amount as the horizontal coordinate and the adsorption loss as the vertical coordinate, the relationship curve between the nanobubble injection amount and the adsorption loss under each average particle size and each concentration is drawn, if the adsorption loss gradually decreases below 5% as the injection amount increases, the concentration under the particle size meets the nanobubble cavitation oil displacement requirement, if the adsorption loss amount is always greater than 5%, the concentration under the particle size does not meet the nanobubble cavitation oil displacement requirement, and accordingly the minimum concentration value that meets the nanobubble cavitation oil displacement under different particle sizes is determined , an evaluation chart of particle size-concentration-adsorption loss is established, see Figure 3 .

[0030] Determine whether the nanobubble particle size, concentration and stability meet the expected performance requirements; if not, adjust the nanobubble preparation pressure difference .

[0031] Determine the average particle size of the prepared nanobubbles is 255 nm and the concentration is 5.78×10 9 per mL, the average particle size meets , according to the particle size-concentration-adsorption loss evaluation chart, the minimum concentration value corresponding to the 255 nm particle size is 4.61×10 9 per mL, which meets .

[0032] The prepared nanobubbles are aged for 24 hours under the target reservoir, temperature and salinity conditions, the average particle size is 279 nm, the concentration is 5.24×10 9 per mL, and the nanobubble stability factor is: ; In the formula, The factor affecting the concentration change of nanobubbles is 0.8 here; The factor affecting the variation of nanobubble particle size is 0.2 here; The concentration of nanobubbles after aging is 10. 7 cells / mL; The average particle size of the nanobubbles after aging meets the following requirements. .

[0033] In summary, the prepared nanobubble particle size, concentration, and stability all meet the performance requirements.

[0034] S4, Pulse Injection Parameter Optimization: Based on the starting pressure gradient of the target reservoir, the injection reference pressure, pulse amplitude, and frequency of the periodic hydraulic pulse are determined through numerical simulation optimization. The initiation pressure gradient of the target reservoir was obtained based on core displacement experiments. A numerical simulation model of the reservoir was established based on real geological parameters; different injection reference pressures were set. Pulse amplitude and frequency Orthogonal experiments were conducted, and the selection of the injection reference pressure and pulse amplitude satisfied the following formula: ; In the formula, For formation fracture pressure, The original formation pressure, To initiate pressure; The statistical maximum pressure gradient is greater than Number of grids Number of grids with pressure fluctuations and the total number of grids for the target reservoir Calculate the pressure-pulse spread coefficient of nanobubble vibration-driven oil. The expression is: ; In the formula, For pressure expansion weighting coefficients, The pulse spread factor; Pressure-pulse spread coefficient of nanobubble vibration-driven oil Maximum injection reference pressure Pulse amplitude and frequency As an injection parameter in actual production.

[0035] Under the target reservoir temperature and pressure conditions, based on the target reservoir core, carry out core constant pressure displacement experiment, stepwise pressure increase, with 0.002 MPa / m as the step length, gradually increase the inlet pressure, and record the stable flow rate after 30 minutes of each pressure With differential pressure , until the flow rate increases linearly with the pressure, draw the flow rate With pressure gradient The horizontal axis intercept is the threshold pressure gradient , which is 0.01 MPa / m.

[0036] Based on real geological parameters, establish a numerical simulation model of the oil reservoir, use time-dependent table function or periodic control keyword to set different injection reference pressure , pulse amplitude And frequency , carry out orthogonal test, define the time step to meet , wherein the injection reference pressure And pulse amplitude Select to meet the following formula: ; Call all grid pressure field history data in the whole simulation period, calculate the maximum pressure gradient value of each grid in the whole simulation history, set the screening condition as "pressure gradient ", use the software condition filtering function to count the number of grids that meet the condition in each group of experiments , define it as pressure effective expansion grid; In the grid that has been determined to be pressure effective expansion, extract the pressure / time sequence data of these grids during the whole injection period, count the pressure peak time interval, calculate the pressure fluctuation period , set the screening condition as "pressure fluctuation period ", count the number of grids that meet the condition in each group of experiments , define it as effective fluctuation grid; And count the number of all grids in the target oil reservoir , calculate the nanobubble pressure-pulse expansion coefficient of each group: ; In the formula, is the pressure expansion weight coefficient, Is the pulse expansion coefficient; Trigger iterative optimization of nanobubble properties and pulse injection parameters, including: using hydraulic pulse to excite the vibration effect of nanobubbles, using periodic nanobubble high-low pressure alternating injection mode: the injection pressure in high pressure injection stage is , the injection time is , the injection pressure in low pressure injection stage is ​, the injection time is .

[0037] The pressure-pulse expansion coefficient of each group of nanobubble relaxation oil displacement As shown in Table 2, when the injection reference pressure is 28 MPa, the pulse amplitude is 1.5 MPa, and the frequency is 0.5 CPH, the pressure-pulse expansion coefficient is 0.758 at most, and the above parameters are taken as the actual injection production parameters of nanobubble relaxation oil displacement.

[0038] The pressure-pulse expansion coefficient of each group of experiments in Table 2

[0039] S5, pulse oil displacement and optimization: performing nanobubble field injection with optimized pulse injection parameters, and when the water cut is monitored to rise to 98%, iterative optimization of the properties of nanobubbles and pulse injection parameters is triggered.

[0040] The nanobubble relaxation effect is excited by hydraulic pulse, and a periodic nanobubble high-low pressure alternating injection mode is specifically adopted: in a complete pulse cycle (2 hours), first, a high-pressure injection stage is performed, the injection pressure is stably controlled at 29.5 MPa, and the injection is continued for 1 hour; then, a low-pressure injection stage is switched, the injection pressure is reduced to 26.5 MPa, and the injection is continued for 1 hour, the high-low pressure process is cyclically performed, a stable pressure fluctuation field is formed, the nanobubble relaxation effect is excited, and through the real-time data acquisition system, key parameters such as injection pressure and flow rate are monitored to ensure that the actual injection curve is consistent with the designed waveform.

[0041] After the nanobubble relaxation oil displacement scheme is implemented, a comprehensive oil reservoir development dynamic monitoring system is established, and the monitoring content includes but is not limited to: the injection pressure and flow rate of the injection well, the oil production, water production, water cut and flow pressure of the production well, and the interwell pressure field response is monitored in real time by using the downhole pressure monitoring equipment, the monitoring data is analyzed and evaluated regularly, if it is found that the oil displacement effect does not reach the expectation, the optimization process is started, that is, returning to step S1, reevaluating the current oil reservoir parameters, and iteratively optimizing steps S2 to S5 in turn: adjusting the particle size and concentration of nanobubbles according to the new oil reservoir conditions, optimizing the pulse injection parameters again through numerical simulation, and updating the field injection scheme.

[0042] In the embodiment 2, the nanobubble relaxation oil displacement system for executing the nanobubble relaxation oil displacement method is provided, and the system comprises: The parameter acquisition module is used for determining target oil reservoir parameters, well deployment conditions and development dynamics. A nano-bubble preparation module is configured to prepare nano-bubbles according to target reservoir conditions, i.e., determining a nano-bubble preparation ambient pressure and a nano-bubble preparation pressure difference according to target reservoir temperature and pressure conditions, and completing preparation of the nano-bubbles; A performance evaluation module is configured to calculate nano-bubble adsorption loss, determine a minimum concentration value at different particle sizes, and establish a particle size-concentration-adsorption loss evaluation chart; to determine whether nano-bubble particle size, concentration and stability meet expected performance requirements; and to adjust the nano-bubble preparation pressure difference if they do not meet the requirements. An injection parameter optimization module is configured to determine an injection reference pressure, a pulse amplitude and a frequency of the periodic hydraulic pulse through numerical simulation optimization based on a start-up pressure gradient of the target reservoir. A field injection scheme execution and optimization module is configured to execute nano-bubble field injection with the optimized pulse injection parameters, and to trigger iterative optimization of nano-bubble properties and pulse injection parameters when the water cut is monitored to rise to 98%.

[0043] To further prove the positive effects of the above embodiments, the present application based on the above technical solutions carries out the following simulation experiments: Analog formation water and nano-bubbles (average particle size 255 nm, concentration 5.78 x 10 9 individuals / mL) are selected to carry out core displacement comparison experiments, the core permeability is 343 x 10 3 μm 2 , the crude oil viscosity is 25 mPa·s, which is consistent with the target reservoir conditions, the back pressure is the formation pressure 24.3 MPa during core displacement, and four groups of displacement experiments are carried out, and the injection schemes are as follows: 1. Pure analog formation water displacement, constant pressure injection, injection pressure is 28 MPa; 2. First, displace to a water cut of 98% with analog formation water, constant pressure injection, injection pressure is 28 MPa, then hydraulic pulse injection of analog formation water, injection reference pressure is 28 MPa, amplitude is 1.5 MPa, and pulse frequency is 0.5 CPH; 3. First, displace to a water cut of 98% with analog formation water, constant pressure injection, injection pressure is 28 MPa, then switch to nano-bubble displacement, constant pressure injection, injection pressure is 28 MPa; 4. First, displace to a water cut of 98% with analog formation water, constant pressure injection, injection pressure is 28 MPa, then switch to nano-bubble displacement, constant pressure injection, injection pressure is 28 MPa; Figure 4 、 Figure 5As shown, compared with pure simulated formation water flooding, the simulated formation water pulse injection can reduce the water cut by 3% and increase the recovery rate by 3%, the nano-bubble flooding can reduce the water cut by 17% and increase the recovery rate by 9%, and the nano-bubble vibration flooding can reduce the water cut by 31% and increase the recovery rate by 18%; compared with the nano-bubble flooding, the nano-bubble vibration flooding can further increase the recovery rate by 9%; compared with the combined effect of the simulated formation water pulse injection and the nano-bubble flooding, the nano-bubble vibration flooding can further increase the recovery rate by 6%.

[0044] The above is only a preferred specific embodiment of the present application, but the protection scope of the present application is not limited thereto, any modification, equivalent replacement and improvement within the technical range disclosed by the present application and within the spirit and principle of the present application should be covered within the protection scope of the present application.

Claims

1. A nano bubble hunting method, characterized by, The method stimulates the nanobubble's running vibration effect through periodic hydraulic pulse, and comprises the following steps: S1, parameter acquisition: determining target reservoir parameter, well deployment situation and development dynamic; S2, preparing nanobubbles according to target reservoir conditions: determining nanobubble preparation environment pressure and nanobubble preparation pressure difference according to target reservoir temperature and pressure conditions, and completing nanobubble preparation; S3, nanobubble performance evaluation: calculating nanobubble adsorption loss, determining minimum concentration value under different particle sizes, and establishing particle size-concentration-adsorption loss evaluation chart; determining whether nanobubble particle size, concentration and stability meet expected performance requirements; if not, adjusting nanobubble preparation pressure difference; S4, pulse injection parameter optimization: based on the starting pressure gradient of the target reservoir, the injection reference pressure, pulse amplitude and frequency of the periodic hydraulic pulse are determined through numerical simulation optimization; S5, pulse oil displacement and optimization: executing nanobubble field injection with the optimized pulse injection parameters, and triggering iterative optimization of nanobubble properties and pulse injection parameters when the water cut rises to 98%.

2. The nano bubble hunting method according to claim 1, wherein In step S1, the target reservoir parameter includes target reservoir porosity, permeability, temperature, salinity, formation pressure, formation fracture pressure, crude oil viscosity and crude oil density.

3. The nano bubble hunting method according to claim 1, wherein In step S2, the nanobubbles are prepared by membrane dispersion to convert gas into nanoscale bubbles in water.

4. The nano bubble hunting method according to claim 3, wherein The nanobubble preparation environment pressure is equal to the target reservoir pressure.

5. The nano bubble hunting method according to claim 1, wherein In step S3, the particle size-concentration-adsorption loss evaluation chart is established, including: The target reservoir core and the SPG membrane are scanned by using a high-resolution CT scanning device, a pore distribution curve of each is extracted, and a median pore diameter of the core sample is obtained , a porosity , a density , a macro-pore specific surface area , and a median pore diameter of the SPG membrane ; wherein the macro-pore is greater than 200 nm; with the median pore diameter of the SPG membrane as the lower limit of the average particle size of the nano-bubbles with the median pore diameter of the SPG membrane as the upper limit of the average particle size of the nano-bubbles in the interval between the upper and lower limits, 8 values are selected as the target average particle size of the nano-bubbles according to the logarithmic uniformity for each target particle size, 5 injection concentrations are set respectively: , , , , different average particle sizes and different concentrations of nano-bubbles are prepared.

6. The nano bubble hunting method according to claim 5, wherein Determine whether the nanobubble particle size, concentration and stability meet the expected performance requirements, including: respectively carry out single core nanobubble injection experiment, injection amount is 10PV, injection PV interval is 0-3PV, every 0.1PV sampling once, injection PV interval is 3-6PV, every 0.2PV sampling once, injection PV interval is 6-10PV, every 0.5PV sampling once, obtain the nanobubble concentration in produced fluid at different injection amounts , calculate the nanobubble concentration adsorption loss at different injection amounts of each group experiment ; ； wherein is the concentration of nano-bubbles before injection, is the concentration of nano-bubbles in the produced fluid; With injection amount as abscissa and adsorption loss as ordinate, the relationship curve between nano-bubble injection amount and adsorption loss under each average particle size and each concentration is drawn; if the adsorption loss gradually decreases below 5% with the increase of injection amount, the concentration under the particle size meets the requirement of nano-bubble cavitation driving oil, if the adsorption loss is always greater than 5%, the concentration under the particle size does not meet the requirement of nano-bubble cavitation driving oil, and then the lowest concentration value under different particle sizes meeting the requirement of nano-bubble cavitation driving oil is determined , and the particle size-concentration-adsorption loss evaluation chart is established.

7. The nano bubble hunting method according to claim 6, wherein Also including: Determination of average particle diameter of nanobubbles and concentration , average particle diameter satisfies , concentration according to particle diameter-concentration-adsorption loss evaluation chart ; The nano bubbles are aged for 24 h under the target reservoir, temperature and salinity conditions, and the nano bubble concentration and particle size are determined again, and the nano bubble stability factor is calculated , and the expression is: ； In the formula, is a nano-bubble concentration change influence factor, is a nano-bubble particle size change influence factor, is a nano-bubble concentration after aging, is a nano-bubble average particle size after aging.

8. The nano bubble hunting method according to claim 1, wherein In step S4, the injection reference pressure, pulse amplitude and frequency of the periodic hydraulic pulse are determined, including: Based on core displacement experiment to obtain the target reservoir threshold pressure gradient , based on real geological parameters, establish reservoir numerical simulation model; set different injection reference pressure , pulse amplitude and frequency , carry out orthogonal test, the selection of injection reference pressure and pulse amplitude meets the following formula: ； wherein is the formation fracture pressure, is the original formation pressure, is the kickoff pressure; The number of grids with statistical maximum pressure gradient greater than The number of grids with pressure fluctuation The number of grids with pressure fluctuation The number of all grids in the target reservoir The pressure-pulse propagation coefficient of nanobubble cavitation oil displacement is calculated The expression is: ； wherein is a pressure spread weight coefficient, is a pulse spread coefficient; Pressure-pulse spreading coefficient for nanobubble cavitation oil displacement Maximum injection reference pressure Pulse amplitude And frequency As actual production injection parameters.

9. The nano bubble hunting method according to claim 8, wherein In step S5, iterative optimization of the nano-bubble properties and pulse injection parameters is triggered, including: exciting the nano-bubbles with a hydraulic pulse to excite the nano-bubbles to vibrate, and using a periodic nano-bubble high-low pressure alternating injection mode: the injection pressure in the high-pressure injection stage is , the injection time is , the injection pressure in the low-pressure injection stage is , and the injection time is .

10. A nanobubble resonance oil displacement system, which is achieved by the nanobubble resonance oil displacement method according to any one of claims 1 to 9, characterized by, The system comprises: A parameter acquisition module for determining target reservoir parameter, well deployment situation and development dynamic; A nanobubble preparation module for preparing nanobubbles according to target reservoir conditions: determining nanobubble preparation environment pressure and nanobubble preparation pressure difference according to target reservoir temperature and pressure conditions, and completing nanobubble preparation; A performance evaluation module for calculating nanobubble adsorption loss, determining minimum concentration value under different particle sizes, and establishing particle size-concentration-adsorption loss evaluation chart; determining whether nanobubble particle size, concentration and stability meet expected performance requirements; if not, adjusting nanobubble preparation pressure difference; An injection parameter optimization module for determining the injection reference pressure, pulse amplitude and frequency of the periodic hydraulic pulse through numerical simulation optimization based on the starting pressure gradient of the target reservoir; A field injection scheme execution and optimization module for executing nanobubble field injection with the optimized pulse injection parameters, and triggering iterative optimization of nanobubble properties and pulse injection parameters when the water cut rises to 98%.

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