CN116925719B - Composite plugging system of foam coated particles and preparation method and application thereof - Google Patents

Abstract

The invention discloses a composite plugging system of foam-coated particles, a preparation method and an application thereof. The raw materials include, by weight, 1 to 5 parts of a heat-resistant and salt-resistant foaming agent, 5 to 10 parts of coated particles and 100 parts of water. During the preparation, organic silicon resin and graphene oxide in a mass ratio of 1:1 are mixed and dissolved in water, and ultrasonicated to obtain a coating mixture; the particles to be coated are pretreated; the coating mixture and the particles to be coated are mixed, stirred and impregnated, dried, cooled and sieved to obtain coated particles; the heat-resistant and salt-resistant foaming agent solution stirred at 5000 rpm to 8000 rpm for 2 hours is mixed with the coated particles to obtain a composite plugging system of foam-coated particles, wherein the coated particles include a coating layer mixed with organic silicon resin and graphene oxide and the particles to be coated include PVC particles and/or wood particles. The plugging system of the invention has low cost, heat and salt resistance, and simple preparation process, and solves the problems of high cost, complex preparation and unstable performance of existing fracture-cavity oil reservoir sealing systems.

Description

A composite plugging system of foam-coated particles and its preparation method and application

Technical Field

The invention belongs to the technical field of oil and gas reservoir development, and specifically belongs to a composite plugging system of foam-coated particles and a preparation method and application thereof.

Background Art

Carbonate oil and gas reservoirs are the most important component of global oil and gas. my country's carbonate oil reservoirs are mainly fracture-cavity carbonate rocks, which are not only ultra-deep, high-temperature, and high-mineralization, but also have a fracture-cavity structure with diverse shapes, large differences in size, and uneven distribution, and are highly heterogeneous. The main contradiction in the mid-term development is the crossflow problem in the dominant channel caused by the shape, distribution, and connection mode of the fractures and caves.

The existing technical solutions to the above problems are as follows:

1) Mechanical plugging technology: Use downhole tools such as packers and bridge plugs in oil wells to block water in high-water layers to prevent water in high-water layers from entering the oil wells. When dealing with multi-layer mining problems, mechanical plugging is the main method to solve the contradiction between layers. However, for fracture-cavity carbonate reservoirs with diverse storage spaces and complex oil-water relationships, it is difficult to implement mechanical water plugging. After the production section is flooded, the water content will rise rapidly. Due to the strong heterogeneity of the oil layer permeability, the edge and bottom water will invade from high-permeability channels such as fractures.

2) Chemical plugging technology: Chemical agents or solid particles are injected into the channeling layer of the oil well, and the gel or solid particles generated by the chemical agent reaction are used to block the channeling channel. However, this technology has high requirements on the performance of the plugging agent, especially it is difficult to meet the high-strength plugging and high-temperature and high-salinity environment requirements of carbonate fracture-cavity oil and gas reservoirs. The plugging system is mainly divided into three types according to the plugging agent type: high-temperature resistant polymer gel system, solid phase particle system and high-temperature foam profile control system, among which:

Non-solid plugging materials such as gels cannot meet the ultra-high temperature reservoir conditions due to their own stability. They can have a strong water plugging effect in fracture-dissolution pores and small caves in fracture-cavity reservoirs, but their plugging ability for large-scale wide fractures and large caves is significantly weakened; at the same time, for water intrusion problems with large water bodies and sufficient energy, the effective period is still relatively short, especially after multiple cycles of continuous plugging, the effect becomes worse.

Solid granular plugging agents have stable chemical properties and good compression resistance and plugging performance. Currently, there are mainly cement-based inorganic granular plugging agents and curable granular plugging agents, but both have the characteristic of poor injectability, so they cannot reach deep into the formation to achieve the purpose of plugging.

Foam fluid has a good application in the development process of oil and gas fields. Since foam is stable when it meets water, defoams when it meets oil, and its plugging ability increases with the increase of permeability, it can play a good role in fluidity control and can effectively adjust the crossflow problem of heterogeneous formations. The main factor restricting the current use of foam in high-temperature reservoirs is the research and development of temperature-resistant and salt-resistant foam systems. Foam is a thermodynamically unstable system. Conventional high-temperature foam systems have poor stability under large-scale fracture conditions, and their plugging performance needs to be further improved and enhanced.

Summary of the invention

In order to solve the problems existing in the prior art, the present invention provides a composite plugging system of foam-coated particles and a preparation method and application thereof, which has low cost, is heat and salt resistant, and has a simple preparation process, thereby solving the problems of high cost, complex preparation, and unstable performance of the existing fracture-cavity oil reservoir sealing system.

To achieve the above-mentioned purpose, the present invention provides the following technical solution: a composite plugging system of foam-coated particles, wherein the raw materials include, by weight, 1 to 5 parts of a heat-resistant and salt-resistant foaming agent, 5 to 10 parts of coated particles and 100 parts of water, wherein the coated particles include a coating layer and particles to be coated, the coating layer is made of a mixture of silicone resin and graphene oxide, and the particles to be coated are PVC particles and/or wood particles.

Furthermore, the heat-resistant and salt-resistant foaming agent has a temperature resistance greater than 120°C and a salt resistance greater than 200,000 mg/L; the density of the PVC particles is 0.95-1.13 g/cm3, and the particle size is 1-5 mm; the density of the wood particles is 0.16-0.20 g/cm3, and the particle size is 1-5 mm.

The present invention also provides a method for preparing a composite plugging system of foam-coated particles, the specific steps of which are as follows:

S1: dissolving silicone resin and graphene oxide in a mass ratio of 1:1 in water, and ultrasonicating to obtain a coating mixture;

S2 pre-treats the particles to be coated;

S3: mixing the coating mixture prepared in step S1 with the particles to be coated in step S2, stirring and impregnating, drying, cooling, and sieving to obtain coated particles;

S4: mixing the heat-resistant and salt-resistant foaming agent solution stirred at 5000 rpm to 8000 rpm with the coated particles obtained in step S3 to obtain a composite plugging system of foam-coated particles.

Furthermore, in step S1, the mass fraction of the silicone resin and the graphene oxide is 1% to 10%, the graphene oxide is industrial grade, has a purity of >97%, a thickness of <5nm, and a diameter of 2μm to 8μm; and the ultrasonic time is 30min to 60min.

Furthermore, in step S2, the pretreatment is to heat the particles to be coated to 80°C to 100°C.

Furthermore, in step S3, the stirring time is 5 minutes, and the immersion time is 15 minutes to 30 minutes.

Furthermore, the drying is performed under constant temperature vacuum drying at 50°C.

Furthermore, in step S4, the mass fraction of the temperature-resistant and salt-resistant foaming agent solution is 1% to 5%.

Furthermore, in step S4, the mixing method is to spread and flatten the foam of the heat-resistant and salt-resistant foaming agent after stirring for 2 hours, and then evenly place the coated particles on the surface of the foam.

The present invention also provides an application of a composite plugging system of foam-coated particles. When the particles to be coated are wood particles and PVC particles, the composite plugging system of foam-coated particles is used to perform all-round plugging of the formation; when the particles to be coated are wood particles, the composite plugging system of foam-coated particles is used to plug high parts of the formation; when the particles to be coated are PVC particles, the composite plugging system of foam-coated particles is used to plug low parts of the formation.

Compared with the prior art, the present invention has at least the following beneficial effects:

The present invention provides a composite plugging system of foam-coated particles, which improves the performance of particle plugging agents through coating technology. The silicone resin in the coating layer can increase the strength of the particle plugging agent, ensuring that the particles can play a consolidation role in harsh fracture-cavity oil reservoirs; the graphene oxide in the coating layer can increase the dispersibility of the particle plugging agent in the foam, because the particles themselves are hydrophobic, and the graphene oxide has a strong hydrophilicity, which can reduce the contact angle of water on the particle surface. Although the graphene oxide in the coating layer is easy to fall off, the fallen graphene oxide can play a role in stabilizing the foam to a certain extent. At the same time, the foam has high viscosity and strong suspension ability, which can ensure that PVC particles can achieve long-distance migration in the cracks and reach a distant target layer. In low-angle cracks, the foam has obvious advantages in carrying particles with a larger density, and the particle migration time is short, so it can reach the target layer quickly, effectively plug the fracture-cavity oil reservoir, and improve the oil recovery rate.

The present invention also provides an application of the composite plugging system of the foam carrying coated particles in oil field development. The foam carries particles of different densities according to actual needs. The composite plugging system of the foam carrying coated particles is injected in a uniform state. After entering the deep formation, the flow rate of the injection system slows down. Due to the density difference, stratification will occur. The density of wood particles is much smaller than that of water. Even after adding a coating layer, they can still float on the upper layer of water and can be easily carried by foam to the middle and high parts of the formation for effective plugging. The density of PVC particles is similar to that of water. After adding a coating layer, their density is slightly larger than that of water, so they can be easily carried by foam to the middle and low parts of the formation for effective plugging.

The preparation method of the present invention adopts ultrasonic dispersion to make the organic silicon resin and graphene oxide disperse more evenly and not easy to settle; when preparing the coated particles, the coating mixed liquid and the particles to be coated are stirred and mixed, so that the coating mixed liquid can penetrate into the internal microstructure of the particles to be coated, and the coating effect is better. After stirring, the particles are dried by a vacuum drying method to prevent some chemical reactions and the mixing of pollutants, and the use of vacuum drying can effectively shorten the drying time. In comparison, the general drying takes a long time; after the coated particles are taken out, they are sieved through a standard sieve to obtain uniform particles that meet the size; a vigorous stirring and mixing method is adopted for the heat-resistant and salt-resistant foaming agent solution, and the generation of foam requires sufficient mixing of gas and liquid and requires a certain amount of energy. Vigorous stirring can produce more stable and dense foam, and the liquid film on the surface of the obtained foam has high viscosity and can carry particles, and the foam of the heat-resistant and salt-resistant foaming agent is extended and flattened, and then the coating particles are evenly placed on the foam surface. This mixing method makes the system uniform, the isotropic force of the foam can be kept stable, and is convenient for subsequent overall control, including adjusting the density, and delaying the occurrence of blockage caused by sedimentation.

BRIEF DESCRIPTION OF THE DRAWINGS

Fig. 1 is a diagram showing the mechanism of action of the coating layer;

Figure 2 Schematic diagram of the composite plugging system with foam carrying coated particles.

FIG3 is a graph showing the relationship between the injection volume, water production rate and recovery rate of the composite plugging system prepared in Example 1.

FIG. 4 shows the plugging rate of the composite plugging system prepared according to an embodiment of the present invention.

DETAILED DESCRIPTION

The present invention will be further described below in conjunction with the accompanying drawings and specific embodiments.

The invention provides a composite plugging system of foam carrying coated particles, comprising the following components in parts by weight: 1 to 5 parts of a heat-resistant and salt-resistant foaming agent, 5 to 10 parts of coated particles, and 100 parts of water.

Preferably, the heat-resistant and salt-resistant foaming agent has a temperature resistance greater than 120° C. and a salt resistance greater than 200,000 mg/L.

Preferably, the water is deionized water.

Preferably, the coated particles are coated PVC (polyvinyl chloride) particles and/or coated wood particles.

Further preferably, the density of the PVC particles is 0.95-1.13 g/cm3, and the particle size is 1-5 mm; the density of the wood particles is 0.16-0.20 g/cm3, and the particle size is 1-5 mm, wherein both the PVC particles and the wood particles can be purchased from the market.

Preferably, as shown in FIG. 1 , the coating layer of the coated particles is made of a mixture of silicone resin and graphene oxide.

Further preferably, the organic silicone resin is in liquid state and has certain adhesion and hydrophobicity; the graphene oxide is of industrial grade, with a purity of >97%, a thickness of <5 nm, and a diameter of 2 to 8 μm.

On the other hand, the present invention also provides a method for preparing a composite plugging system of foam carrying coated particles, comprising the following steps:

Step 1: Take 1% to 10% of silicone resin and 1% to 10% of graphene oxide in a mass ratio of 1:1, mix them in 100 parts of water, and ultrasonically disperse them for 30 to 60 minutes to obtain a coating mixture that is more evenly dispersed and not easy to settle.

Step 2: Place the PVC particles and/or wood particles to be coated into a crucible, heat it to 80-100° C. using a muffle furnace, and maintain a constant temperature using a thermostat.

Step 3: Add the coating mixture prepared in step 1 into the crucible, stir rapidly for 5 minutes and then stand for a period of time, so that the PVC particles and/or wood particles to be coated are immersed in the coating mixture for 15 to 30 minutes, so that the coating mixture is formed on the surface of the particle material and in its internal microstructure, and the coating effect is better;

Step 4: Place the crucible in a constant temperature vacuum drying oven at 50°C and vacuum dry for 24 hours.

Step 5: When the coated particles do not contain a liquid phase, the coated particles are taken out, cooled naturally to room temperature, and sieved through a standard sieve to obtain uniform coated particles that meet the size requirements.

Step 6: Take a heat-resistant and salt-resistant foaming agent solution with a mass fraction of 1% to 5%, stir it at 5000rpm to 8000rpm for 1h to 3h to obtain stable and fine foam. The foam of the heat-resistant and salt-resistant foaming agent solution is extended and flattened, and then the coated particles obtained in step 5 are evenly placed on the foam surface. The liquid film on the foam surface has a high viscosity and can carry the coated particles to obtain a composite plugging system of foam-coated particles.

The mixing method of the foam and the coated particles of the present invention makes the system uniform, and the isotropic force of the foam can be kept stable, which is convenient for subsequent overall control, including adjusting the density, and delaying the occurrence of blockage caused by sedimentation.

As shown in Figure 1, starting from the mixing principle of the coated particle material, the coating layer is regarded as a reinforcement system of the particles, and the coated particles can be regarded as a three-phase composite material composed of a base phase (particles), a bonding surface (silicone resin) and a dispersed phase (graphene oxide). Its mechanical properties are restricted and affected by the mechanical properties of the base phase, the bonding surface and the dispersed phase. When the particles are subjected to tensile and bending stresses, the stress transfer mechanism of the coating layer makes it bear most of the stress, reducing the probability of damage to the internal particles, and the addition of the graphene oxide dispersion layer improves the water-soluble dispersion effect of the particles.

As shown in Figure 2, a is the flow stage of the composite plugging system with foam carrying coated particles in the crack hole; b is the foam drainage stage; c is the layered flow stage of each system (coated wood particles, foam, liquid phase, coated PVC particles); d is the composite plugging system plugging different positions according to density. The foam carries the coated wood particles with lower density into the middle and high parts for plugging; the foam carries the coated PVC particles with higher density into the middle and low parts for plugging.

Scope of application: The above-mentioned composite plugging system of foam carrying coated particles is used to improve the recovery of crude oil in the following ways:

(1) Select fracture-cavity reservoirs in the late stage of water injection or gas injection. Such reservoirs have advantageous crossflow channels and the remaining oil saturation is greater than 0.2, which has development potential.

(2) A composite plugging system that uses foam pumped at a certain pressure to carry coated particles. If you need to plug a medium-high position, use coated wood particles; if you need to plug a medium-low position, use coated PVC particles.

(3) As the composite plugging system containing foam-carrying coated particles is injected into the deep formation, stratification will occur under the action of gravity differentiation, plugging different locations.

The present invention improves the performance of the particle plugging agent through coating technology. The present invention determines the foam to carry particles of different densities according to actual needs. The composite plugging system of the foam carrying the coated particles is injected in a uniform state. After entering the deep formation, the injection system flow rate slows down, and stratification occurs due to the density difference. The density of wood particles is much smaller than that of water. Even after adding the coating layer, they can still float on the upper layer of water and can be easily carried by the foam to the middle and high parts of the formation for effective plugging. The density of PVC particles is similar to that of water. After adding the coating layer, its density is slightly greater than that of water, and it is easy to be carried by the foam to the middle and low parts of the formation for effective plugging.

Example 1

A visual physical model of fracture-vuggy reservoirs was established, and water plugging experiments of composite plugging systems were carried out.

A method for preparing a composite plugging system of foam carrying coated particles comprises the following steps:

Step 1: Take 5% by mass of silicone resin and graphene oxide, mix them in a mass ratio of 1:1, dissolve them in 100 parts of water, and perform ultrasonic dispersion for 50 minutes to obtain a coating mixture.

Step 2: Place the PVC particles to be coated and the wood particles into a crucible, heat it to 90°C using a muffle furnace, and maintain a constant temperature using a constant temperature box.

Step 3: Add the coating mixture prepared in step 1 into the crucible, stir rapidly for 5 minutes and then let it stand for a while, so that the PVC particles and wood particles to be coated are immersed in the coating mixture for 20 minutes, so that the coating mixture is formed on the surface of the particle material and in its internal microstructure.

Step 4: Place the crucible in a constant temperature vacuum drying oven at 50°C and vacuum dry for 24 hours.

Step 5: After drying, take out the coated particles, cool them naturally to room temperature, and use a standard sieve with a pore size of 4 mm to sieve out the desired coated particles.

Step 6: Take a 2.5% mass fraction of a heat-resistant and salt-resistant foaming agent solution, stir it at 8000 rpm for 2 hours to obtain stable and fine foam, spread and flatten the foam of 3 parts of the heat-resistant and salt-resistant foaming agent solution, and then evenly place 8 parts of the coated particles obtained in step 5 on the foam surface to obtain a composite plugging system of foam-coated particles.

As shown in Figure 3, the flow rate was controlled at 0.2 mL/min for water flooding, and the water-free oil production period was reached when the injection volume reached 0.2 PV. When the injection volume reached 1.2 PV, the water production rate reached 98%, and the water production rate dropped to 28% when 0.2 PV of the foam-coated particle composite system was injected into the model. When the water flooding was completed, that is, the injection volume reached 3 PV, the final recovery rate increased from 55% to 78%.

Embodiment 2:

In 2019, the composite plugging system of the foam-coated particles of Example 1 was tested in 8 wells in the fracture-cave oil reservoir field of the X Oilfield, and 6 wells were significantly effective, with an efficiency of 75%, and a cumulative oil increase of 2,674 tons, indicating that the system has good applicability for water plugging in oil wells in the X Oilfield.

Example 3

A visual physical model of fracture-vuggy reservoirs was established, and water plugging experiments of composite plugging systems were carried out.

A method for preparing a composite plugging system of foam carrying coated particles comprises the following steps:

Step 1: Take 1% by mass of silicone resin and 10% by mass of graphene oxide, mix them in a mass ratio of 1:1, dissolve them in 100 parts of water, and disperse them by ultrasonic for 30 minutes to obtain a coating mixture.

Step 2: Place the PVC particles to be coated into a crucible, heat it to 80°C using a muffle furnace, and maintain a constant temperature using a constant temperature box.

Step 3: Add the coating mixture prepared in step 1 into the crucible, stir rapidly for 5 minutes and then let it stand for a while, so that the PVC particles to be coated are immersed in the coating mixture for 15 minutes, so that the coating mixture is formed on the surface of the particle material and in its internal microstructure.

Step 4: Place the crucible in a constant temperature vacuum drying oven at 50°C and vacuum dry for 24 hours.

Step 5: After drying, take out the coated particles, cool them naturally to room temperature, and use a standard sieve with a pore size of 4 mm to sieve out the desired coated particles.

Step 6: Take a 1% mass fraction of heat-resistant and salt-resistant foaming agent solution, stir at 5000 rpm for 3 hours to obtain stable and fine foam, spread and flatten the foam of 1 part of the heat-resistant and salt-resistant foaming agent solution, and then evenly place 5 parts of the coated particles obtained in step 5 on the foam surface to obtain a composite plugging system of foam-coated particles.

Example 4

A visual physical model of fracture-vuggy reservoirs was established, and water plugging experiments of composite plugging systems were carried out.

A method for preparing a composite plugging system of foam carrying coated particles comprises the following steps:

Step 1: Take 10% by mass of silicone resin and 1% by mass of graphene oxide, mix them in a mass ratio of 1:1, dissolve them in 100 parts of water, and perform ultrasonic dispersion for 60 minutes to obtain a coating mixture.

Step 2: Place the wood particles to be coated into a crucible, heat it to 100° C. using a muffle furnace, and maintain a constant temperature using a thermostat.

Step 3: Add the coating mixture prepared in step 1 into the crucible, stir rapidly for 5 minutes and then let it stand for a while, so that the wood particles to be coated are immersed in the coating mixture for 30 minutes, so that the coating mixture is formed on the surface of the particle material and in its internal microstructure.

Step 4: Place the crucible in a constant temperature vacuum drying oven at 50°C for vacuum drying.

Step 5: After drying, take out the coated particles, cool them naturally to room temperature, and use a standard sieve with a pore size of 4 mm to sieve out the desired coated particles.

Step 6: Take a 5% mass fraction of heat-resistant and salt-resistant foaming agent solution, stir at 6500rpm for 1h to obtain stable and fine foam, spread and flatten 5 parts of the foam of the heat-resistant and salt-resistant foaming agent solution, and then evenly place 10 parts of the coated particles obtained in step 5 on the foam surface to obtain a composite plugging system of foam-coated particles.

The blocking rate is defined as the ratio of the difference between the water production rate after the foam-coated particle system is applied under the same conditions and the water production rate before the application to the water production rate before the application, and the blocking rate of the foam-coated particle system in Examples 1, 3, and 4 is obtained, as shown in Figure 4, among which the foam-coated PVC particles + wood particles can block in all directions, with the best effect, and the blocking rate is 62.58%; the foam-coated wood particles can block the middle and upper parts, with the second best effect, and the blocking rate is 34.21%; the foam-coated PVC particles can block the middle and lower parts, with a blocking rate of 25.37%.

Claims (8)

1. The composite plugging system of the foam coated particles is characterized in that the composite plugging system comprises, by weight, 1-5 parts of a temperature-resistant salt-resistant foaming agent, 5-10 parts of coated particles and 100 parts of water, wherein the coated particles comprise a coating layer and particles to be coated, the coating layer is prepared by mixing organic silicon resin and graphene oxide, and the particles to be coated are PVC particles and/or wood particles;

the mass fraction of the temperature-resistant salt-tolerant foaming agent solution is 1% -5%, the temperature resistance of the temperature-resistant salt-tolerant foaming agent is more than 120 ℃, and the salt tolerance is more than 20 ten thousand mg/L;

the mass ratio of the organic silicon resin to the graphene oxide is 1:1, the mass fraction of the organic silicon resin to the graphene oxide is 1% -10%, the graphene oxide is of industrial grade, the purity is more than 97%, the thickness is less than 5nm, and the diameter is 2-8 mu m;

The density of the PVC particles is 0.95 g/cm ³～1.13g/cm³, and the particle size is 1 mm-5 mm; the density of the wood particles is 0.16 g/cm ³～0.20g/cm³, and the particle size is 1-mm mm.

2. The method for preparing the composite plugging system of foam coated particles as defined in claim 1, which is characterized by comprising the following specific steps:

s1, mixing and dissolving organic silicon resin and graphene oxide in a mass ratio of 1:1 in water, and performing ultrasonic treatment to obtain a coating mixed solution;

S2, preprocessing particles to be coated;

s3, mixing, stirring and impregnating the coating mixed solution prepared in the step S1 and the particles to be coated in the step S2, drying, cooling and sieving to obtain coated particles;

and S4, mixing the temperature-resistant salt-tolerant foaming agent solution stirred at 5000-8000 rpm with the coating particles obtained in the step S3 to obtain the composite plugging system of the foam coating particles.

3. The method for preparing a composite plugging system of foam coated particles according to claim 2, wherein in the step S1, the ultrasonic time is 30 min-60 min.

4. The method for preparing a composite plugging system of foam coated particles according to claim 2, wherein in step S2, the pretreatment is to heat the particles to be coated to 80 ℃ to 100 ℃.

5. The method for preparing a composite plugging system of foam coated particles according to claim 2, wherein in the step S3, the stirring time is 5min, and the dipping time is 15 min-30 min.

6. The method for preparing the composite plugging system of foam coated particles according to claim 2, wherein the drying is constant temperature vacuum drying at 50 ℃.

7. The method for preparing a composite plugging system of foam coated particles according to claim 2, wherein in step S4, the mixing is performed by spreading foam of the temperature-resistant and salt-resistant foaming agent stirred for 2 hours, and then uniformly placing the coated particles on the surface of the foam.

8. The use of a composite plugging system of foam coated particles as defined in claim 1, wherein when wood particles and PVC particles are used as the particles to be coated, the composite plugging system of foam coated particles is used for omnibearing plugging of the formation; when the particles to be coated adopt wood particles, the composite plugging system of the foam coated particles is used for plugging high parts in the stratum; when PVC particles are adopted as the particles to be coated, the composite plugging system of the foam coated particles is used for plugging the middle and low parts of the stratum.