High-selectivity solid dispersion type emulsion plugging agent and application thereof

Abstract

The invention provides a high-selectivity solid dispersion type emulsion plugging agent and application thereof.According to the plugging agent, hydrophobic particles serve as a solid dispersion and are blended through a surfactant to form a water-based emulsion, the particle size of the hydrophobic particles is 1-10 microns, the particle size distribution D90 is smaller than or equal to 5 microns, the hydrophobic particles are combinations of multiple irregular shapes, and the hydrophobic particles are mixed with the surfactant to form the high-selectivity solid dispersion type emulsion plugging agent. The working solution concentration of the solid dispersion in the water-based emulsion is 5-30%, the mass percent of the surfactant in the water-based emulsion is 5-10%, the mass percent of water in the solvent is 30-50%, and the balance is the oily solvent. The plugging agent takes hydrophobic particles as a solid dispersion, forms a water-based emulsion through blending of the surfactant and the solvent, has excellent plugging effect and high-temperature-resistant stability, is suitable for high-temperature and high-salinity reservoir conditions, realizes effective plugging of large pore channels of an oil well, and improves the recovery rate of the oil well.

Description

Technical Field

[0001] The invention relates to the technical field of oilfield exploitation, and relates to a highly selective solid dispersion type emulsion plugging agent. The invention also relates to the application of the highly selective solid dispersion type emulsion plugging agent in oilfields. Background Art

[0002] The high water content problem in oil fields, represented by water production from oil wells, consumes energy and reduces the oil recovery rate, and increases the load of produced fluid treatment, resulting in secondary problems such as corrosion, scaling, and environmental pollution. The effective development of high-water-content oil fields is not only the key research direction of conventional production in major oil fields, but also the basic guarantee for increasing reserves and production. Therefore, water control in oil wells is of great significance. Mechanical water plugging and chemical water plugging are important means of water control in oil wells. The application of mechanical water plugging technology needs to meet certain tubing conditions and water-producing layer requirements, which is not conducive to controlling water from deep in the reservoir, and its effect has certain limitations. Especially for reservoir conditions where the sleeve cannot be opened and closed normally, the oil layer thickness is limited, or there is no natural interlayer, it is impossible to plug water in the oil well through mechanical plugging.

[0003] Chemical water plugging technology usually relies on the performance of plugging agents and supporting processes. It achieves formation water plugging by squeezing plugging agents into the target reservoir, thereby reducing the water content of the produced fluid and achieving the purpose of oil well water plugging. Especially for non-selective plugging agents, higher requirements are placed on the judgment of the water outlet position of the oil well. For example, if too much plugging agent enters the oil layer, it will be difficult to restore production capacity after mistaken plugging, resulting in serious losses. Selective chemical plugging agents achieve the purpose of plugging water inside the reservoir without plugging oil through different mechanisms of action, but they have disadvantages such as poor temperature resistance and high construction risks in engineering applications. Therefore, the supporting process of chemical water plugging technology has a significant impact on the effect of oil well water plugging engineering applications.

[0004] Therefore, in view of the high water content problem in oil wells and the current technological development status, it is necessary to develop a highly selective solid dispersion emulsion plugging agent. Summary of the invention

[0005] The purpose of the present invention is to provide a highly selective solid dispersion emulsion plugging agent, which provides a physical and chemical combination plugging agent system for oil field water plugging control, and can effectively plug large pores in oil wells and improve recovery. The present invention also provides the use of the highly selective solid dispersion emulsion plugging agent in oil field water plugging.

[0006] The technical solution adopted by the present invention to solve the above technical problems is: a highly selective solid dispersion emulsion plugging agent, the plugging agent uses hydrophobic particles as solid dispersion, and is formulated by surfactant to form a water-based emulsion, the particle size of the hydrophobic particles is 1-10um, and the particle size distribution D90≤5um, the mass percentage of the solid dispersion in the water-based emulsion is 5-30%, the mass percentage of the surfactant in the water-based emulsion is 5-10%, the mass percentage of water in the solvent is 30-50%, and the balance is an oily solvent.

[0007] Furthermore, it is preferred that the solid dispersion has super hydrophobic and lightweight properties, an initial contact angle of ≥150°, and a density of 0.35-0.85 g / cm 3 .

[0008] Furthermore, it is preferred that the solid dispersion has a relatively high surface energy and a certain hollow structure, with a specific surface area of ​​200-800 m2 / g and a porosity of 50-80%.

[0009] Furthermore, the solid dispersion preferably has excellent high temperature stability, with a thermogravimetric loss of less than 2% at 200° C., and is fully suitable for high temperature reservoir conditions.

[0010] Furthermore, it is preferred that the solid dispersion does not decompose or degrade, and has a shelf life of ≥ 1 year.

[0011] Furthermore, it is preferred that the surfactant is at least one of a polyoxyethylene salt anionic surfactant and a quaternary ammonium salt cationic surfactant.

[0012] The present invention also provides an application of a highly selective solid dispersion emulsion plugging agent in an oil well, comprising the following implementation steps:

[0013] Step 1, determining the particle size and hollow structure of the dispersion particles according to the reservoir permeability, porosity and pore size parameters of the target single well;

[0014] Step 2, determining the surfactant composition of the dispersion emulsion according to the reservoir temperature, formation water salinity, and formation water quality composition of the target single well;

[0015] Step 3, the emulsion plugging agent is diluted with on-site liquid preparation water to prepare a water-based emulsion working fluid of a certain concentration, and the working fluid is squeezed into the target layer from the wellhead using a chemical pump. After being squeezed into the reservoir, the dispersed particles are pushed into the deep reservoir along with the displacement fluid. With the action of high-temperature, high-mineralization formation water and the seepage shearing action of the working fluid, the working fluid demulsifies and releases the dispersed particles. The particles are physically blocked and chemically agglomerated at the pore throats to transform the large pores of the reservoir, forming a hydrophobic and oil-permeable selective partition.

[0016] When the permeability of the target single well reservoir is greater than 100mD and is above 500mD, the water-based emulsion working fluid prepared in step 3 can be directly applied to the target single well; when the permeability of the target single well reservoir is 100-500mD, there is a risk of direct injection on the surface, and appropriate artificial fracture creation or rock expansion technology should be selected through physical model experiments for combined application.

[0017] In step 3, the concentration (mass percentage) of the water-based emulsion type working solution is 5-30%, and water is used to adjust the dilution to the target concentration.

[0018] The present invention has at least the following beneficial effects: the present invention utilizes the material properties of small-sized, high-surface-energy solid particles, and uses a variety of surfactants to prepare a water-in-oil micro-nano emulsion system according to the on-site construction requirements of the oil field. The particles are carried by the emulsion into the target position of the reservoir, and the functional particles are released after the emulsion breaks and becomes unstable. The functional particles undergo physical blockage and chemical agglomeration at the pore throats to transform the large pores of the reservoir, forming a hydrophobic and oil-permeable selective partition. This breaks through the technical idea of ​​high-strength cross-linking and curing required by traditional chemical water plugging technology. At the same time, combined with the supporting implementation process, selective water control measures are carried out for oil wells to achieve the selective water control requirements of "controlling but not killing" the reservoir, and improve the safety and stability of the engineering application of this technology. DETAILED DESCRIPTION

[0019] The technical solution of the present invention is further described below through specific embodiments.

[0020] A highly selective solid dispersion emulsion plugging agent, the plugging agent uses hydrophobic particles as solid dispersions, and is formulated with a surfactant to form a water-based emulsion, the hydrophobic particles have a particle size of 1-10um, a particle size distribution D90≤5um, and are a combination of multiple irregular shapes, the mass percentage of the solid dispersion in the water-based emulsion is 5-30%, the mass percentage is 5-10%, 5-15%, 5-20%, 5-25%, 5-30%, 10-15%, 10-20%, 10-30%, 15-20%, 15-20%, 15-30%, 20-25%, 20-30%, 25-30%, etc., the mass percentage of the surfactant in the water-based emulsion is 5-10%, such as the mass percentage is 5%, 6%, 7%, 8%, 9%, 10%, etc.; the mass percentage of water in the solvent is 30-50%, and the balance is an oily solvent. The water-based emulsion carries the hydrophobic particles into the target reservoir in the form of an emulsion, and realizes the oil-wet and hydrophobic transformation of the reservoir through the dual plugging effects of chemical selective plugging and physical blocking.

[0021] Since the permeability range of the main oil field is 10-1000mD, the porosity distribution is 2-35%, and the overall porosity is medium-high and medium-high permeability; therefore, the hydrophobic particles selected by the plugging agent of the present invention are 1-10um, such as particle sizes of 1-2um, 1-3um, 1-5um, 1-8um, 1-10um, 2-3um, 2-5um, 4-5um, 4-6um, 4-8um, 4-10um, 5-8um, 5-10 um, 6-8um, 6-10um, 7-9um, 7-10um, 8-9um, 8-10um, etc. The hydrophobic particles with this particle size are pushed into the deep reservoir with the displacement fluid after being squeezed into the reservoir. With the action of high-temperature and high-mineralization formation water and the shearing action of the working fluid seepage, the hydrophobic particles can be better released by the working fluid. The particles are physically blocked and chemically agglomerated at the pore throat to transform the large pores of the reservoir, forming a hydrophobic and oil-free selective partition. The size of the hydrophobic particles carried by the emulsion should not be too small, otherwise it is difficult to form an effective blockage in the seepage channel; and, as far as chemical measures in the industry are concerned, the injectability of the agent is the basis for the success or failure of the measures, so the particle size should not be too large to avoid construction risks caused by failure to pump.

[0022] In some specific embodiments, the solid dispersion is super hydrophobic, lightweight, has an initial contact angle of ≥150°, and a density of 0.35-0.85 g / cm 3 The solid dispersion has good oleophilic and hydrophobic properties, which can realize the selective water control function under reservoir conditions.

[0023] In some specific embodiments, the solid dispersion has a relatively high surface energy and a certain hollow structure, a specific surface area of ​​200-800 m2 / g, and a porosity of 50-80%. The higher the porosity of the solid dispersion, the larger the specific surface area; the larger the specific surface area, the higher the specific surface energy. Materials with high specific surface energy exhibit extremely strong agglomeration performance and agglomeration strength.

[0024] In some specific embodiments, the solid dispersion has excellent high temperature stability, with a thermogravimetric loss of less than 2% at 200° C., and is fully applicable to high temperature reservoir conditions, ensuring a lasting plugging effect.

[0025] In some specific embodiments, the solid dispersion does not decompose or degrade, and has a shelf life of ≥ 1 year, thereby ensuring a lasting plugging effect.

[0026] In some specific embodiments, the surfactant is at least one of a polyoxyethylene salt anionic surfactant and a quaternary ammonium salt cationic surfactant. The specific surfactant is selected to achieve a better activation effect on the plugging agent and better form a stable water-in-oil micro-nano emulsion system.

[0027] The present invention also provides an application of a highly selective solid dispersion emulsion plugging agent in an oil well, comprising the following implementation steps:

[0028] Step 1: Determine the particle size and hollow structure of the dispersed particles according to the reservoir permeability, porosity and pore size parameters of the target single well; derive the radius estimation relationship from Darcy's law; that is, convert the roar radius size according to the actual parameters of the target block (including permeability, porosity, pore size, etc.); and then determine the specific particle size of the dispersed particles in combination with the theoretical calculation results to ensure injectability and erosion resistance.

[0029] Step 2, determining the surfactant composition of the dispersion emulsion according to the reservoir temperature, formation water salinity, and formation water quality composition of the target single well;

[0030] Step 3, dilute the emulsion plugging agent with on-site liquid preparation water to prepare a water-based emulsion working fluid with a certain concentration, the concentration of the water-based emulsion working fluid is 5-30%, and the dilution water is determined to be clean water or production water according to the pumping time.

[0031] A chemical pump is used to squeeze the working fluid from the wellhead into the target formation. After being squeezed into the reservoir, the dispersed particles are pushed into the deep reservoir along with the displacement fluid. With the action of high-temperature, high-mineralization formation water and the seepage shearing action of the working fluid, the working fluid demulsifies and releases the dispersed particles. The particles are physically blocked and chemically agglomerated at the pore throats to transform the large pores of the reservoir, forming a hydrophobic and oil-permeable selective partition.

[0032] When the target single well reservoir permeability is greater than 100mD and is above 500mD, the water-based emulsion working fluid prepared in step 3 can be directly applied to the target single well; when the target single well reservoir permeability is 100-500mD, it indicates that there is a risk of direct injection, and appropriate artificial fracture creation or rock expansion technology should be selected through physical modeling experiments for combined application.

[0033] Example 1

[0034] A directional well in an offshore oil field, with a production layer section of 2624.10-2640.32 meters, a well inclination of 28°, a perforation of 2630.00-2636.00 meters (6 meters), an average permeability of 321mD, a porosity of 8%-15%, a reservoir temperature of 115℃, a formation water salinity of 40000mg / L, a daily liquid production of 1400 cubic meters, a daily oil production of 70 cubic meters, and a comprehensive water content of about 95%. The oil well has been in stable production for more than 1000 days. It was decided to achieve deep water blocking in the reservoir and further release production capacity through a combination of artificial fracture creation and chemical water blocking.

[0035] In this embodiment, the particle size of the dispersion particles is selected to be 1um, and the type of surfactant is prepared. The surfactant is a polyoxyethylene salt anionic surfactant, and the added amount is 5.5% by mass percentage in the target working fluid; clean water is selected for liquid preparation, and the working fluid concentration is 5%-10%. After static bottle test, its stability time under reservoir conditions is greater than 16 hours. The injection position of the plugging agent is determined to be 2630.00-2636.00 meters (3 meters). Before pumping, the plugging agent is first injected into the main channel through the deflagration fracturing operation, and then squeezed into the formation through a high-pressure pump. The effect of on-site implementation: After the measures, the daily liquid production is 1250 cubic meters, the daily oil production is 100 cubic meters, and the comprehensive water content is about 92%; the daily oil production is 30 cubic meters, and the water content decreases by 3%.

[0036] Example 2

[0037] A directional well in an offshore oil field, with a production layer section of 4610.60-4621.40 meters, a well inclination of 44° (maximum well inclination of 66°), and a perforation of 4610.00-4621.00 meters (3 meters). The oil-water layer section is 4621.40-4624.30 meters, with a permeability of 800-2000mD. Below the oil-water layer section is a natural interlayer, with a reservoir temperature of 125℃ and a formation water salinity of 32700mg / L. The single well has been in production for more than 10 years. Before the measures were taken, it was shut down due to a failure of the electric submersible pump. Before the shutdown, it produced 10,000 barrels of liquid and 190 barrels of oil per day, with a comprehensive water content of about 98%. According to the working conditions of the single well, it was decided to create an artificial baffle at the oil-water interface through a combined process of perforation repair and chemical water plugging to achieve stable oil and water control.

[0038] In this embodiment, the particle size of the dispersion is 1-3um, and clear water is selected for liquid preparation. The surfactant is a polyoxyethylene salt anionic surfactant, and the addition amount is 6% by mass percentage in the target working liquid; the surfactant also includes a quaternary ammonium salt cationic surfactant, and the addition amount is 2% by mass percentage in the target working liquid; the working liquid concentration is 5%-30%, and the working liquid in the static bottle test experiment is stable for more than 20 hours under reservoir conditions. An artificial baffle is selected at 4620.50-4622.50 meters at the oil-water interface, and the double bridge plug process is used to seal the target position before pumping. After the hole filling operation, the plugging agent is squeezed and injected. After the squeezing is completed, it returns to the original perforated layer to resume production. On-site implementation effect: After the measures, the liquid production is limited, with a daily liquid production of 3,500 barrels, a daily oil production of 420 barrels, and a comprehensive water content of about 88%; under the condition of limited liquid production, the daily oil production is increased by 230 barrels, and the water content decreases by 10%.

[0039] The present invention achieves highly selective plugging of large reservoir pores and improves the recovery rate by precisely controlling the particle size, shape and distribution of the solid dispersion and the selection of the surfactant. In addition, the solid dispersion has excellent high temperature resistance and is suitable for high temperature reservoir conditions, ensuring a long-lasting plugging effect. The plugging agent does not decompose or degrade, has a long effective period, and has a simple preparation process and readily available raw materials, thereby reducing production costs. The plugging agent formula and application process are flexibly adjusted according to the target single well conditions, thereby improving the applicability and plugging effect of the plugging agent.

[0040] The above descriptions are merely embodiments of the present invention and are not intended to limit the patent scope of the present invention. Any equivalent structure or equivalent process transformation made using the contents of the present invention specification, or directly or indirectly applied in other related technical fields, are also included in the patent protection scope of the present invention.

Claims

1. A highly selective solid dispersion emulsion plugging agent, characterized in that: The plugging agent uses hydrophobic particles as solid dispersion and is prepared by surfactant and solvent to form a water-based emulsion. The solvent includes water and oily solvent, wherein the oily solvent includes kerosene and diesel. The particle size of the hydrophobic particles is 1-10um, and the particle size distribution D 90 ≤5um, the mass percentage of the solid dispersion in the water-based emulsion is 5-30%, the mass percentage of the surfactant is 5-10%; the mass percentage of water in the solvent is 30-50%, and the remainder is an oily solvent.

2. The highly selective solid dispersion emulsion plugging agent according to claim 1, characterized in that: The solid dispersion is super hydrophobic and lightweight, with an initial contact angle of ≥150° and a density of 0.35-0.85 g / cm 3 .

3. The highly selective solid dispersion emulsion plugging agent according to claim 1, characterized in that: The hydrophobic particles are a combination of various irregular shapes.

4. The highly selective solid dispersion emulsion plugging agent according to claim 1, characterized in that: The solid dispersion has high surface energy and a certain hollow structure, a specific surface area of ​​200-800 m2 / g, and a porosity of 50-80%.

5. The highly selective solid dispersion emulsion plugging agent according to claim 1, characterized in that: The solid dispersion has excellent high temperature stability, with a thermogravimetric loss of less than 2% at 200° C., and is fully suitable for high temperature reservoir conditions.

6. The highly selective solid dispersion emulsion plugging agent according to claim 1, characterized in that: The solid dispersion does not decompose or degrade, and has a shelf life of ≥1 year.

7. The highly selective solid dispersion emulsion plugging agent according to claim 1, characterized in that: The surfactant is at least one of a polyoxyethylene salt anionic surfactant and a quaternary ammonium salt cationic surfactant.

8. Use of the highly selective solid dispersion emulsion plugging agent according to any one of claims 1 to 7 in oil wells, characterized in that: The implementation steps include: Step 1, determining the particle size and hollow structure of the dispersion particles according to the reservoir permeability, porosity and pore size parameters of the target single well; Step 2, determining the surfactant composition of the dispersion emulsion according to the reservoir temperature, formation water salinity, and formation water quality composition of the target single well; Step 3, dilute the emulsion plugging agent with on-site liquid preparation water to prepare a water-based emulsion working fluid of the target degree. After the dispersion particles are squeezed into the reservoir, they are pushed into the deep reservoir with the displacement fluid. With the action of high-temperature, high-mineralization formation water and the seepage shearing action of the working fluid, the working fluid demulsifies and releases the dispersion particles. The particles are physically blocked and chemically agglomerated at the pore throats to transform the large pores of the reservoir, forming a hydrophobic and oil-permeable selective partition to achieve oil well plugging.

9. The use of the highly selective solid dispersion emulsion plugging agent in oil wells according to claim 8, characterized in that: When the target single well reservoir permeability is greater than 100mD and is above 500mD, the water-based emulsion working fluid prepared in step 3 can be directly applied to the target single well; when the target single well reservoir permeability is 100-500mD, first select the appropriate artificial fracture, artificial partition, double bridge plug process or rock expansion process through physical modeling experiments, and then inject the plugging agent.

10. The use of the highly selective solid dispersion emulsion plugging agent in oil wells according to claim 8, characterized in that: In step 3, the concentration of the water-based emulsion type working solution is 5-30%.