CN115960598B - Application method of micro-nano fly ash particle reinforced foam system - Google Patents
Application method of micro-nano fly ash particle reinforced foam system Download PDFInfo
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Abstract
The invention belongs to the field of petroleum exploitation, and particularly provides an application method of a micro-nano fly ash particle reinforced foam system. According to the invention, the viscosity of the foam system is adjusted by selecting the corresponding solid phase particle size range, polymer molecular weight and polymer concentration according to the stratum permeability, so that the self-suspension of the solid phase particles is realized, and the solid phase particles with different particle diameters are enabled to present different regular sedimentation and migration through the self-suspension of the solid phase particles, thereby further playing a role in the stratum. By adopting the method, the service life of the foam can be prolonged, the stability of the foam can be enhanced, and meanwhile, the migration depth of a foam system can be improved according to different oil reservoirs.
Description
Technical Field
The invention relates to an application method of a micro-nano fly ash particle reinforced foam system, and belongs to the technical field of oil and gas field development engineering.
Background
In the background of double carbon, with the development of CCUS technology in China, the energy structure is continuously optimized in recent years, and the enhancement of carbon capture and utilization is necessary for optimizing oil and gas energy. Fly ash produced by coal-fired power plants is solid waste listed in the clear of China, and the utilization amount of the fly ash is far less than the production amount, so that a large amount of accumulation is generated, and the environment is greatly damaged. For example, since the excessive accumulation of fly ash contaminates groundwater, the fly ash also forms micro-particles in the air that can be inhaled into the human body, so that the utilization rate of the fly ash is very urgent.
In the oil gas exploitation process, the foam flooding is an efficient method for improving the recovery ratio, and the foam is unstable in gas diffusion, liquid film precipitation and the like in the stratum, so that the stability of the foam is poor, and the stability of the foam restricts the application of the foam flooding in an oil reservoir. In oil fields with harsh environmental conditions, such as high temperature, high pressure, high mineralization and fracture-cavity type oil reservoir foam with large pore scale variation are more difficult to stabilize, thereby influencing the exploitation of the oil reservoir. At present, the resource utilization of the fly ash particles is a focus of attention of a plurality of scholars, and the scholars propose that the fly ash particles are used as a stabilizer for strengthening the foam, so that the foam stability can be greatly improved.
Chinese patent CN 109971443A discloses a three-phase foam channeling-blocking agent and a preparation method thereof, wherein the thickened oil exploitation blocking-adjusting method consists of a foaming agent, starch, a polymer, an initiator, a cross-linking agent, a control agent and solid phase particles, a foam system has better temperature resistance, but the required materials are various, the components are more complex, more workload is increased, sedimentation is easy to occur in the field use process of an oil field, the system is not easy to store for a long time, layering phenomenon can be generated when the system moves for a short distance in a stratum, the particles are settled and gas-liquid fluid is continuously moved forwards due to the action of gravity difference, the foam is broken, the stratum is possibly blocked due to non-homogeneity in the stratum, and the effect of efficiently utilizing the foam cannot be achieved.
Chinese patent CN102977872 a discloses a foam system composed of anionic surfactant, nonionic surfactant, water-soluble high molecular polymer, etc. for enhanced oil recovery of tertiary oil recovery, wherein the thickener has no foaming capacity, and the oil-displacing agent has good displacement effect but the residue after foam displacement may pollute the stratum.
Chinese patent CN109943313 a discloses a preparation device and method for supercritical carbon dioxide microemulsion and fly ash particle compound dispersion, the particle size range of fly ash captured from a power plant is wider, the uniformity of particle size is improved by grinding when large particle size is used, and the non-uniformity of particle size causes obvious sedimentation phenomenon of particles in foam solution. The particles generally need to be ground before being configured into foam, and the particle size range after grinding is narrowed. The uniformity of the particle size is achieved by grinding, the cost of work is increased intangibly, the construction is inconvenient, and secondary dust is generated in the grinding process. At present, few people pay attention to the influence of the viscosity of a system on the stabilization of foam by particles, so that the effective action amount of the foam is reduced, most of particles sink to the bottom in the production process of the foam, only a small part of particles contribute to the stability of the foam, and the overall stability of the foam is poor.
Chinese patent CN110984933 a discloses a method for strengthening multiphase compound profile control by using fly ash in ultra-high water cut period in oil field, and the profile control effect can be improved by using foam slugs. The profile control and flooding mode consists of fly ash reinforced foam, surfactant foam, microemulsion and water. The three components act to increase the profile control effect, change the heterogeneity of the reservoir and improve the development value of the oil reservoir, but do not consider the influence of the gravity differentiation on the solid phase particles on the aspects of resource utilization and environmental protection, so that the method has a large lifting space.
Chinese patent CN105238380 a discloses a new type inorganic fine particle reinforced foam system for oil and gas field and its preparation method, the reinforced foam system is composed of foaming agent, new type inorganic fine particles and nitrogen, carbon dioxide or air. The reinforced foam system can change waste into valuable, utilizes novel inorganic fine particles, reduces pollution of the novel inorganic fine particles to the air environment, and reflects efficient utilization of resources, but the system is not involved in the aspect of particle size separation.
Chinese patent CN109943307 a discloses a foam solution for profile control and plugging in thickened oil thermal recovery process, a preparation method thereof, a foam system and a profile control and plugging method. The foam system consists of foaming agent, oil-containing sludge, coal-mixed combustion ash, dispersing agent and the like. The foam system realizes the integral recycling of the oily sludge from the source to the final product, reduces the coal consumption, and does not relate to the particle size selection of solid phase particles in the foam.
The above techniques are differentiated during application without regard to particle size uniformity. In the migration process, the sedimentation rule of the solid-phase particles with non-uniform particle size is different under the influence of gravity. As the particles continue to settle during transport, the stability of the foam decreases. The continual settling of particles during deep migration (deep referring to the distance in the radial direction of the working well) results in fly ash plugging during field use. A series of problems such as incompatibility with the reservoir or sedimentation during migration have limited the promotion of fly ash, and therefore, it is necessary to provide a low cost foam system having a higher foam life that is largely composed of various particle size ranges of fly ash.
Disclosure of Invention
The invention provides an application method of a micro-nano fly ash particle reinforced foam system aiming at the problems. The invention selects the corresponding solid phase particle size range, polymer molecular weight and polymer concentration according to the stratum permeability to adjust the viscosity of the foam system, realizes the self-suspension of solid phase particles, ensures that large solid phase particles and small solid phase particles present different regular sedimentation and migration through the self-suspension, and further plays a role in the stratum. By adopting the method, the service life of the foam can be prolonged, the stability of the foam can be enhanced, and the regenerability and migration depth of a foam system can be improved according to different oil reservoirs.
In order to achieve the above purpose, the technical scheme adopted by the invention is as follows:
an application method of a micro-nano fly ash particle reinforced foam system,
the foam system comprises: nonionic surfactant, solid phase particles, and polymer.
According to the invention, the viscosity of the foam system is changed by adjusting the molecular weight of the polymer, so that solid-phase particles with different particle diameters can be stably dispersed in the foam system, and the foam stabilizing performance of the solid-phase particles is improved.
For permeabilities of greater than 1000 x 10 -3 μm 2 Selecting solid phase particle size of the oil reservoirA foam system with a viscosity of 150 mPa.s-300 mPa.s and a thickness of 23-53 μm;
for a permeability of 100X 10 -3 μm 2 ~1000×10 -3 μm 2 Selecting a foam system with solid-phase particle size of 6.5-23 mu m and viscosity of 100-150 mPa.s;
for a permeability of 10X 10 -3 μm 2 ~100×10 -3 μm 2 Selecting a foam system with solid phase particles with the particle size of 500 nm-6.5 mu m and the viscosity of 50 mPas-100 mPas.
The viscosity is regulated by the concentration and molecular weight of the polymer.
Preferably, the permeability is greater than 1000X 10 -3 μm 2 The oil reservoir of the foam system is characterized in that solid-phase particles with the particle diameter of 23-53 mu m, the concentration of 0.07-0.3 wt% and the molecular weight of 1000-1500 ten thousand are selected for compounding and combining;
for a permeability of 100X 10 -3 μm 2 ~1000×10 -3 μm 2 The oil reservoir of the foam system is prepared by selecting solid-phase particles with the particle diameter of 6.5-23 mu m, the concentration of 0.02-0.07 wt% and the molecular weight of 700-1000 ten thousand for compounding and combining;
for a permeability of 10X 10 -3 μm 2 ~100×10 -3 μm 2 The oil reservoir is characterized in that a foam system is prepared by compounding and combining solid-phase particles with the particle diameter of 500 nm-6.5 mu m, the concentration of the solid-phase particles is 0.01-0.02 wt% and the molecular weight of the solid-phase particles is 500-700 ten thousand.
For complex oil reservoirs with pores of different dimensions coexisting, different foam systems are pumped according to different permeability of stratum by adjusting viscosity of the foam systems. Aiming at the stratum with high permeability, the high molecular weight polymer and the large particle size solid phase particles form better compatibility, the foam system is thickened, and the thicker foam system enters the corresponding stratum for operation through the pumping action. Correspondingly, aiming at the stratum with small permeability, a better compatibility effect is formed by the polymer with small molecular weight and the solid phase particles with small particle size, the viscosity of a foam system is reduced, and the polymer enters the corresponding stratum for operation through the pumping effect. Different particle sizes are suspended in the same stratum through foam systems with different consistencies to the specified corresponding positions.
For example, the oil reservoir is injected with water and gas for a plurality of times of huff and puff or long-time flushing, and the pore space near the injection well is larger than the original pore space. In the foam injection process, the near well region is a large pore stratum and has larger average permeability relative to the far well region, the far well region is a small pore stratum and has smaller average permeability, the stratum is in a heterogeneous state, the shearing action of foam just injected into the stratum is weaker, the pore throat is larger, the necking phenomenon is worse, the foam stability is rapidly reduced after the foam is injected for a certain distance, the foam continues to migrate to generate gas-liquid separation, and the subsequent deep migration cannot be performed. In order to solve the problem, a foam system with larger solution viscosity is selected to carry large solid-phase particles into the stratum according to the stratum permeability in the early injection period, the large solid-phase particles are transported to a near well region without blocking pores, and sedimentation of the solid-phase particles is generated in the process of stabilizing the foam. Later in the injection, a foam system with smaller solution viscosity is selected for reinjection, and the solution carries smaller solid-phase particles to continue deep migration.
Wherein the nonionic surfactant comprises: higher fatty alcohol polyoxyethylene ether (AEO), dodecylphenol polyoxyethylene ether (OP-10), alkylphenol Polyoxyethylene Ether (APEO).
The polymer is polyacrylamide, and the molecular weight is 500-1500 ten thousand. The polymer firstly thickens a foam system to suspend solid phase particles, a nonionic surfactant is adsorbed on the surfaces of the positively charged solid phase particles, the surface potential of the solid phase particles is full, and a sphere with uncharged groups outside and charged groups wrapped is formed. The non-ionic surfactant spheres which wrap the solid phase particles are mutually exclusive, so that the solid phase particles can be stably dispersed in the solution, and the whole foam system is more stable.
The solid phase particles are fly ash, and the solid phase particles of the fly ash are distributed according to mass fraction: 47.83% of oxygen, 11.48% -31.14% of silicon, 6.40% -22.91% of aluminum, 1.90% -18.51% of iron and 0.3% -25.1% of calcium. The density of the fly ash is 1.9-2.9 g/cm 3 The bulk density is 0.531-1.261 g/cm 3 Is thatLow cost and high yield. The particle size of the solid phase particles is 500 nm-53 mu m.
According to the invention, the viscosity of the solution is regulated by regulating the molecular weight and the concentration of the polymer, so that the suspension stability of solid-phase particles in a foam system is improved, and the foam stabilizing capacity of the solid-phase particles is exerted and enhanced; according to the invention, corresponding solid-phase particles are selected according to different pore scales, so that the solid-phase particles form bridging based on a bridging theory, and quick and effective plugging is realized.
Preferably, the solid phase particles selected for use in the present invention have a particle size of less than one third of the pore throat diameter. When the particle size of the solid phase particles is smaller than one third of the pore throat diameter, the solid phase particles cannot be accumulated and blocked in the flowing process in the pore throat; if the particle size of the solid phase particles is more than one third of the pore throat diameter, the flow of the solid phase particles in the pore throat is accumulated and blocked, so that the subsequent foam system cannot be pumped continuously, and the flow of the solid phase particles is influenced.
More preferably, the concentration of the solid phase particles in the foam system is not less than 5wt%, and when the concentration of the solid phase particles reaches 5wt%, the solid phase particles can effectively bridge and block the leakage channel.
The invention also provides a preparation method of the foam system, which comprises the following steps:
step S1, adding a surfactant into deionized water to prepare surfactant aqueous solution;
step S2, screening the solid-phase particles according to stratum conditions, and screening out solid-phase particles with corresponding mesh numbers;
step S3, adding the solid phase particles and the corresponding polymers into the surfactant aqueous solution prepared in the step S1, and fully stirring to obtain a first mixed solution;
s4, performing 500-1000W ultrasonic dispersion on the first mixed solution obtained in the step S3 for 1-3 hours to obtain a second mixed solution;
step S5, dispersing the second mixed solution obtained in the step S4 at a high speed to obtain a third mixed solution;
and S6, stirring and foaming the third mixed solution obtained in the step 5 by adopting a Waring Blender method to obtain the fly ash particle reinforced foam system for improving the deep migration stability.
In the step S1, the surfactant is a nonionic surfactant, and the concentration is 0.1-0.7wt%.
In the step S2, the solid-phase particles are fly ash, the concentration is 5-20wt%, and the particle size range is 500 nm-53 mu m.
In the step S3, the concentration of the polymer is 0.01-0.3wt%, and polyacrylamide is added to increase the viscosity of the foam system, so that the dispersion of solid phase particles in the foam system is more stable.
And in the step S5, high-speed dispersion is carried out by adopting a high-speed dispersing instrument, wherein the high-speed dispersion is intermittent dispersion with the rotating speed of 15000-25000 r/min, the dispersing time is 1-3 min, the standing time is 20-40S, and the dispersing-standing-dispersing process is carried out.
In the steps S4 and S5, through ultrasonic dispersion and high-speed dispersion, the surfactant is fully contacted and fully reacted with the solid phase particles, so that the surfactant is adsorbed on the solid phase particles to play a role in dispersing the solid phase particles, and meanwhile, the foam system can be thickened.
The stirring speed of the Waring Blender method in the step S6 is 7000-9000 rpm, the stirring time is 2-5 min, and the air source in the stirring process is air or nitrogen.
The foam system can form a longer stability period, the half life of the foam system can last for 20 days, the long-term stability of the foam system benefits from the fact that solid phase particles forming a three-phase foam system exist between liquid films of the foam, liquid in the foam is separated out along with the time, separated out liquid carries part of particles to flow into another liquid film tissue, the flow of the solid phase particles bridges in the foam liquid film, and gas diffusion is hindered, so that the liquid film tissue is firmer; the addition of the polymer can ensure that the solid-phase particles can be uniformly and stably dispersed in the solution to a great extent, and the suspension capacity of the solid-phase particles is improved by changing the interfacial tension of the liquid.
Compared with the prior art, the invention has the following beneficial effects:
(1) According to the invention, the viscosity of the foam system is adjusted by selecting the size range of the solid phase particles, the molecular weight of the polymer and the concentration of the polymer according to the stratum permeability, so that the self-suspension of the solid phase particles is realized, and the large solid phase particles and the small solid phase particles are enabled to present different regular sedimentation and migration through the self-suspension of the solid phase particles, so that the foam system further plays a role in the stratum.
(2) The foaming volume of the foam system provided by the invention is 415mL by using 100mL foaming liquid under the stirring of a Waring Blender method, the half-life period of the generated foam solution is 4894s, and the foam stability of the foam system can be maintained for an ultra-long time at normal temperature and normal pressure.
(3) The invention provides a gas, liquid and solid three-phase foam system, wherein nonionic surfactant in the three-phase foam system and positively charged solid particles can generate synergistic effect through mutual adsorption of charges.
(4) In the preparation process of the foam system provided by the invention, the surfactant is more stably adsorbed on the surface of the solid phase particles, so that the hydrophobicity of the solid phase particles is changed; the solid phase particles in the liquid film are mutually staggered to form a framework similar to a bridge, the mechanical strength of the liquid film is increased due to the existence of the solid phase particles, the solid phase particles play a role in protecting the outside of the liquid film and the boundary layer of the liquid film to delay the thinning of the liquid film, and the stability of a foam system is greatly improved; after the foam is destroyed in the stratum, the pollution of the solid phase particles to the stratum is small, and part of the solid phase particles can be adsorbed to the surface of the stratum, so that the wettability of the reservoir is changed, and the recovery ratio is improved.
(5) The foam system provided by the invention has wide development prospect, greatly reduces the cost, and realizes environment-friendly operation of turning harm into valuable.
Detailed Description
In order to make the technical problems, technical solutions and advantages to be solved by the present invention more apparent, the following detailed description will be given with reference to specific embodiments.
The experimental materials and steps described above were used in the examples and comparative examples, and the materials, reagents, etc. used in the examples were all commercially available and the experimental methods were conventional unless otherwise specified.
Example 1
The foam system comprises the following components in percentage by weight: the nonionic surfactant AEO concentration was 0.3wt%; the molecular weight of the polymer polyacrylamide is 1200 ten thousand, and the concentration is 0.07 weight percent; the particle size of the solid-phase particle fly ash is 38 mu m (400 meshes), and the concentration is 10wt%; adding deionized water to supplement to 100wt%;
a method of making a foam system comprising:
step S1, adding a surfactant into deionized water to prepare surfactant aqueous solution;
step S2, screening the solid-phase particles according to stratum conditions, and screening out solid-phase particles with corresponding mesh numbers;
step S3, adding the solid-phase particles and the polymer into the surfactant aqueous solution prepared in the step S1, and fully stirring to obtain a first mixed solution;
step S4, performing 800W ultrasonic dispersion on the first mixed solution in the step S3 for 2 hours to obtain a second mixed solution;
and S5, performing high-speed dispersion on the second mixed solution obtained in the step S4 to obtain a third mixed solution, wherein the high-speed dispersion is intermittent dispersion with the rotating speed of 20000r/min (wherein the dispersion time is 2min and the standing time is 30S, and the process of dispersion-standing-dispersion is performed).
And S6, stirring and foaming the third mixed solution obtained in the step 5 for 3 minutes by adopting a Waring Blender method at a rotating speed of 8000rpm to obtain the fly ash particle reinforced foam system for improving the deep migration stability.
Example 2
The foam system comprises the following components in percentage by weight: the nonionic surfactant AEO concentration was 0.4wt%; the molecular weight of the polymer polyacrylamide is 1200 ten thousand, and the concentration is 0.07 weight percent; the particle size of the solid-phase particle fly ash is 38 mu m (400 meshes), and the concentration is 10wt%; adding deionized water to supplement to 100wt%;
the foam was prepared in the same manner as in example 1.
Example 3
The foam system comprises the following components in percentage by weight: the nonionic surfactant AEO concentration was 0.5wt%; the molecular weight of the polymer polyacrylamide is 1200 ten thousand, and the concentration is 0.07 weight percent; the particle size of the solid-phase particle fly ash is 38 mu m (400 meshes), and the concentration is 10wt%; adding deionized water to supplement to 100wt%;
the foam was prepared in the same manner as in example 1.
Example 4
The foam system comprises the following components in percentage by weight: the nonionic surfactant AEO concentration was 0.4wt%; the molecular weight of the polymer polyacrylamide is 800 ten thousand, and the concentration is 0.03 weight percent; the particle size of the solid-phase particle fly ash is 15 mu m (900 meshes), and the concentration is 15wt%; adding deionized water to supplement to 100wt%;
the foam was prepared in the same manner as in example 1.
Example 5
The foam system comprises the following components in percentage by weight: the nonionic surfactant AEO concentration was 0.4wt%; the molecular weight of the polymer polyacrylamide is 700 ten thousand, and the concentration is 0.01 weight percent; the particle size of the solid-phase particle fly ash is 2.7 mu m (5000 meshes), and the concentration is 20wt%; adding deionized water to supplement to 100wt%;
the foam was prepared in the same manner as in example 1.
Example 6
The foam system comprises the following components in percentage by weight: the nonionic surfactant AEO concentration was 0.3wt%; the molecular weight of the polymer polyacrylamide is 700 ten thousand, and the concentration is 0.02 weight percent; the particle size of the solid-phase particle fly ash is 6.5 mu m (2000 meshes), and the concentration is 10wt%; adding deionized water to supplement to 100wt%;
the plugging experiment is carried out by adopting a sand filling pipe, wherein the average pore throat diameter of the sand filling pipe is 57 mu m, and the permeability is 35 multiplied by 10 -3 μm 2 。
The operation steps of the plugging experiment are as follows:
(1) Preparing a sand filling model, and filling prepared 200-mesh quartz sand into a sand filling pipe; checking the air tightness, and measuring the dry weight of the sand filling pipe if the air tightness is good;
(2) Will be filled with sandThe tube was evacuated for 4 hours and then was evacuated at 0.5mL min -1 The wet weight of the sand filling pipe after the saturated water is weighed;
(3) Calculating the porosity through the weight difference between the wet weight and the dry weight of the sand filling pipe; according to the darcy equation, the permeability of the sand filling pipe is tested by injecting water with a constant flow rate of 1 mL/min;
(4) Firstly, the solution is treated with 0.5 mL.min -1 Leading water flooding is carried out at the injection rate of 2PV; then nitrogen is used for 1 mL-min -1 Foam system mixed solution 0.5 mL/min -1 Foam flooding is carried out at the injection rate and the ratio of the gas to the liquid of 2:1, and the injection amount of a foam system at the stage is 8PV; finally, the solution is treated with 0.5 mL-min -1 Carrying out subsequent water flooding at an injection rate of 3PV;
(5) And recording the pressure difference at two ends of the sand filling pipe, and judging the plugging effect.
Example 7
The foam system comprises the following components in percentage by weight: the nonionic surfactant AEO concentration was 0.4wt%; the molecular weight of the polymer polyacrylamide is 700 ten thousand, and the concentration is 0.02 weight percent; the particle size of the solid-phase particle fly ash is 2.7 mu m (5000 meshes), and the concentration is 20wt%; deionized water was added to make up to 100wt%.
The plugging experiment is carried out by adopting a sand filling pipe, the sand filling pipe is filled by adopting 200-mesh quartz sand, the average pore throat diameter is 43 mu m, and the permeability is 20 multiplied by 10 -3 μm 2 . The procedure of the plugging experiment was the same as in example 6.
Comparative example 1
The foam system comprises the following components in percentage by weight: the AEO concentration of the nonionic surfactant is 0.3wt percent, and deionized water is added to supplement to 100wt percent;
the preparation method of the foam system comprises the following steps:
step S1, adding the surfactant into water according to a proportion to prepare surfactant aqueous solution;
step S2, performing ultrasonic dispersion on the aqueous solution of the surfactant in the step S1 for 2 hours by using 700W;
step S3, performing high-speed dispersion on the solution subjected to ultrasonic dispersion in the step S2 by using a high-speed dispersing instrument, wherein the high-speed dispersion is intermittent dispersion with the rotating speed of 20000r/min (wherein the dispersing time is 2min, the standing time is 30S, and the dispersion is performed according to the process of dispersing-standing-dispersing);
and S4, stirring and foaming the solution subjected to the high-speed dispersion in the step S3 for 3 minutes by adopting a Waring Blender method at a rotating speed of 8000rpm to obtain a foam system.
Comparative example 2
The foam system comprises the following components in percentage by weight: the AEO concentration of the nonionic surfactant is 0.4wt percent, and deionized water is added to supplement to 100wt percent;
the foam system was prepared in the same manner as in comparative example 1.
Comparative example 3
The foam system comprises the following components in percentage by weight: the AEO concentration of the nonionic surfactant is 0.5wt percent, and deionized water is added to supplement to 100wt percent;
the foam system was prepared in the same manner as in comparative example 1.
Comparative example 4
The foam system comprises the following components in percentage by weight: the AEO concentration of the nonionic surfactant is 0.3wt percent, and deionized water is added to supplement to 100wt percent;
the preparation method of the foam system comprises the following steps:
step S1, adding the surfactant into water according to a proportion to prepare surfactant aqueous solution;
and S2, stirring and foaming the aqueous solution of the surfactant obtained in the step S1 for 3 minutes by adopting a Waring Blender method at a rotating speed of 8000rpm to obtain a foam system.
Comparative example 5
The foam system comprises the following components in percentage by weight: the nonionic surfactant AEO concentration was 0.4wt%; the molecular weight of the polymer polyacrylamide is 1000 ten thousand, and the concentration is 0.07wt%; the particle size of the solid-phase particle fly ash is 23 mu m (600 meshes), and the concentration is 10wt%; deionized water was added to make up to 100wt%.
The plugging experiment is carried out by adopting a sand filling pipe, the sand filling pipe is filled with 200-mesh quartz sand, the average pore throat diameter is 43 mu m, and the permeability of the sand filling pipe is adjusted to be 20 multiplied by 10 -3 μm 2 . The procedure of the plugging experiment was the same as in example 6.
Comparative example 6
The foam system comprises the following components in percentage by weight: the nonionic surfactant AEO concentration was 0.4wt%; the molecular weight of the polymer polyacrylamide is 1200 ten thousand, and the concentration is 0.07 weight percent; deionized water was added to make up to 100wt%.
The plugging experiment is carried out by adopting a sand filling pipe, the sand filling pipe is filled with quartz sand with 200 meshes, the average pore throat diameter is 43 mu m, and the permeability of the sand filling pipe is adjusted to be 20 multiplied by 10 -3 μm 2 . The procedure of the plugging experiment was the same as in example 6.
Comparative example 7
The foam system comprises the following components in percentage by weight: the nonionic surfactant AEO concentration was 0.4wt%; the molecular weight of the polymer polyacrylamide is 800 ten thousand, and the concentration is 0.03 weight percent; adding deionized water to supplement to 100wt%;
the foam system was prepared in the same manner as in example 1.
Comparative example 8
The foam system comprises the following components in percentage by weight: the nonionic surfactant AEO concentration was 0.4wt%; the molecular weight of the polymer polyacrylamide is 800 ten thousand, and the concentration is 0.01 weight percent; the particle size of the solid-phase particle fly ash is 15 mu m (900 meshes), and the concentration is 15wt%; adding deionized water to supplement to 100wt%;
the foam system was prepared in the same manner as in example 1.
The experimental method comprises the following steps:
and (3) putting the foam system obtained by stirring by a method of 100mL Waring Blender into a 500mL measuring cylinder, immediately timing, recording the volume of foam generated in the measuring cylinder as a foaming volume V (mL), standing the foam in the measuring cylinder, observing the time of separating out liquid in the foam, and recording the half-life T(s) of the separating out liquid when the separating out liquid in the foam is 50 mL. The stability and foaming capacity of the foam were verified by the foaming volume and the mass of the analytical half-life reaction foam.
Results and analysis 1:
the data for the foam systems V and T prepared are recorded in Table 1.
TABLE 1
The experimental results show that compared with the system without the solid phase particles in comparative examples 1-4, the foam system prepared in examples 1-4 has a very long foam half-life period due to the addition of the solid phase particles, the viscosity of the solution is improved due to the addition of the solid phase particles, the interfacial tension of a liquid film in the foam system is increased, the foam stability is greatly enhanced, and the foam has very good stability.
Results and analysis 2:
the data record of the plugging experiments are shown in Table 2.
TABLE 2
As a result of the experiment, the foam formed in each of example 6, example 7 and comparative example 6 was better in the foam stabilizing effect of the reinforcing phase particles. Clogging occurred in the passage of comparative example 5.
As shown in comparative examples 6 and 7, according to different permeability of stratum, the solid phase particles are stably dispersed and suspended in the solution by adjusting the particle size of the solid phase particles, the molecular weight and the concentration of the polymer, so as to generate a stable foam system. From comparative examples 7 and 5, the blocking of comparative example 5 is caused by the excessively large particle size of the solid phase particles to block the channels, which may be a phenomenon of accumulation blocking of particles. As is clear from comparative examples 7 and 6, the strength of the foam formed by the reinforcing phase particles is stronger than that formed by the non-reinforcing phase particles, and thus the addition of the solid phase particles effectively enhances the stability of the foam.
Results and analysis 3:
the data for the foam systems V and T prepared are recorded in Table 3 below.
TABLE 3 Table 3
As can be seen by comparing table 3, the addition of the polymer can increase the liquid separation half-life of the foam system; the addition of solid phase particles also increases the stability of the foam, but only by a small amount; only when the polymer is in a suitable ratio to the solid phase particles will a very good synergistic effect be produced and the foam will be very stable.
Application example 1:
because of the problems of long-term exploitation or sand production, the pore throat of the near well zone becomes larger, and the pore throat corresponding to the far well zone is smaller. For such a formation structural feature, the present application example sets the following sand-pack experiment:
(1) Preparing a sand filling model, and filling prepared 200-mesh quartz sand into the second half section of a sand filling pipe; checking the air tightness, and measuring the dry weight of the sand filling pipe if the air tightness is good;
(2) Vacuumizing the sand filling pipe for 4 hours, and then carrying out vacuum filling at the concentration of 0.5 mL.min -1 The wet weight of the sand filling pipe after the saturated water is weighed;
(3) Calculating the porosity through the weight difference between the dry weight and the wet weight of the sand filling pipe; the permeability of the second half of the sand pack was tested to 10X 10 by injecting a constant flow of 1mL/min water according to the Darcy equation -3 μm 2 (average pore throat diameter is 30 μm);
(4) Filling 200-mesh quartz sand into the front half section of the sand filling pipe, repeating the steps (1) - (3), calculating the overall permeability of the sand filling pipe, and calculating to obtain the permeability of the front section of the sand filling pipe as 30 multiplied by 10 through the average permeability -3 μm 2 (average pore throat diameter 52 μm);
(5) Firstly, the solution is treated with 0.5 mL.min -1 Leading water flooding is carried out at the injection rate of 2PV; then nitrogen is used for 1 mL-min -1 The first foam system was 0.5mL min -1 Foam flooding is carried out at the injection rate and the ratio of the gas to the liquid of 2:1, and the injection amount of a foam system at the stage is 4PV;
(6) Then nitrogen is used for 1mL min -1 The second group of foam systems was 0.5mL min -1 Gas-liquid ratio 2:1Performing foam flooding at the injection rate and the ratio of the foam system, wherein the injection amount of the foam system at the stage is 4PV;
finally, the solution is treated with 0.5 mL-min -1 Carrying out subsequent water flooding at an injection rate of 2PV;
(7) Recording the pressure difference between two ends of the sand filling pipe, and judging the plugging effect; the pressure difference in this application example was recorded to be 11MPa, and no clogging occurred.
Wherein, the composition proportion of the first group of foam systems is as follows: the nonionic surfactant AEO concentration was 0.4wt%; the molecular weight of the polymer polyacrylamide is 500 ten thousand, and the concentration is 0.01wt%; the particle size of the solid-phase particle fly ash is 5 mu m, and the concentration is 10wt%;
the composition ratio of the second group of foam systems is as follows: the nonionic surfactant AEO concentration was 0.4wt%; the molecular weight of the polymer polyacrylamide is 700 ten thousand, the concentration is 0.02wt%, the particle size of the solid phase particle fly ash is 2.7 mu m, and the concentration is 15wt%;
the foam system in this application example was prepared in the same manner as in example 1.
The application example adopts solid phase particles with different particle diameters to compound polymers with different concentrations and molecular weights, plays an important role in slowing down sedimentation of the solid phase particles and stabilizing suspension of the solid phase particles, and enables a foam system to flow to the deep part of a stratum. If the solid phase particles are not stably dispersed in the fluid under the action of gravity, the phenomenon of sedimentation of the solid phase particles can be generated, the effective concentration of the solid phase particles in the foam liquid is reduced, the stability of the foam is deteriorated, and further the migration of the foam system in the deep part of the stratum is limited. The solid phase particles can be continuously stabilized only when being suspended in the foam system in the flowing process.
Meanwhile, the application example adopts different foam systems for pumping aiming at different pore structures in the same stratum, so that large-particle-size solid-phase particles can be transferred to the large-pore stratum, and small-particle-size solid-phase particles can be transferred to the small-pore stratum, thereby realizing effective plugging of stratum channels.
Claims (6)
1. An application method of a micro-nano fly ash particle reinforced foam system is characterized in that,
the foam system comprises: nonionic surfactant, solid phase particles, and polymers;
the nonionic surfactant is high-carbon fatty alcohol polyoxyethylene ether; the polymer is polyacrylamide; the solid phase particles are fly ash;
for permeabilities of greater than 1000 x 10 -3 μm 2 Selecting a foam system with solid-phase particle size of 23-53 mu m and viscosity of 150-300 mPa.s; the polymer concentration of the foam system is 0.07-0.3wt% and the molecular weight is 1000-1500 ten thousand;
for a permeability of 100X 10 -3 μm 2 ~1000×10 -3 μm 2 Selecting a foam system with solid-phase particle size of 6.5-23 mu m and viscosity of 100-150 mPa.s; the polymer concentration of the foam system is 0.02-0.07 wt% and the molecular weight is 700-1000 ten thousand;
for a permeability of 10X 10 -3 μm 2 ~100×10 -3 μm 2 Selecting a foam system with solid-phase particle size of 500 nm-6.5 mu m and viscosity of 50 mPas-100 mPas; the polymer concentration of the foam system is 0.01-0.02 wt% and the molecular weight is 500-700 ten thousand;
the preparation method of the foam system comprises the following steps:
step S1, adding a nonionic surfactant into deionized water to prepare a nonionic surfactant aqueous solution;
step S2, screening the solid-phase particles according to stratum conditions, and screening out solid-phase particles with corresponding mesh numbers;
step S3, adding the solid phase particles and the corresponding polymers into the surfactant aqueous solution prepared in the step S1, and fully stirring to obtain a first mixed solution;
s4, performing ultrasonic dispersion on the first mixed solution obtained in the step S3 for 1-3 hours by using 500-1000W to obtain a second mixed solution;
step S5, dispersing the second mixed solution obtained in the step S4 at a high speed to obtain a third mixed solution;
step S6, stirring and foaming the third mixed solution obtained in the step S5 by adopting a Waring Blender method to obtain a fly ash particle reinforced foam system for improving the deep migration stability;
wherein the concentration of the nonionic surfactant in the step S1 is 0.1-0.7wt%;
the concentration of the solid phase particles in the step S2 is 5-20wt%;
the polymer concentration in the step S3 is 0.01-0.3wt%.
2. The method for applying the micro-nano fly ash particle reinforced foam system according to claim 1, wherein,
aiming at an oil reservoir with a near-well region being a large-pore stratum and a far-well region being a small-pore stratum, a corresponding high-viscosity foam system is selected to carry large solid-phase particle pumps according to the permeability of the oil reservoir to be injected into the stratum in the early stage of injection, and a corresponding low-viscosity foam system is selected to carry small solid-phase particles in the later stage of injection to be pumped; the permeability of the macroporous stratum is more than 1000 multiplied by 10 -3 μm 2 The method comprises the steps of carrying out a first treatment on the surface of the The permeability of the small pore stratum is 10 multiplied by 10 -3 μm 2 ~100×10 -3 μm 2 The method comprises the steps of carrying out a first treatment on the surface of the The viscosity of the high-viscosity foam system is 150 mPas-300 mPas; the viscosity of the low-viscosity foam system is 50 mPas-100 mPas; the particle size of the large solid-phase particles is 23-53 mu m; the particle size of the small solid phase particles is 500 nm-6.5 mu m.
3. The method for applying the micro-nano fly ash particle reinforced foam system according to claim 1, wherein,
the particle size of the solid phase particles is less than one third of the pore throat diameter.
4. The method for applying the micro-nano fly ash particle reinforced foam system according to claim 1, wherein,
the concentration of the solid phase particles in the foam system is not less than 5wt%.
5. The method for applying the micro-nano fly ash particle reinforced foam system according to claim 1, wherein,
in the step S5, a high-speed dispersing instrument is adopted for high-speed dispersing;
the high-speed dispersion is intermittent dispersion with the rotating speed of 15000-25000 r/min;
the intermittent dispersion is carried out according to the processes of dispersion, standing, dispersion, standing and dispersion, wherein the dispersion time of intermittent dispersion is 1-3 min, and the standing time is 20-40 s.
6. The method for applying the micro-nano fly ash particle reinforced foam system according to claim 1, wherein,
the stirring speed of the Waring Blender method in the step S6 is 7000-9000 rpm, the stirring time is 2-5 min, and the air source in the stirring process is air or nitrogen.
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