CN102093880B - Water control agent for oil well and preparation method thereof - Google Patents

Abstract

The invention relates to an oil well water control agent and a preparation method thereof. The continuous phase is formed by mixing sorbitan oleate, a hydrophobic monomer and an oil phase solvent; The acid is a comonomer, ammonium persulfate is added as an oxidant, and they are dissolved in water together to form a dispersed phase. The dispersed phase is added to the continuous phase to form an inverse emulsion, and the reducing agent sodium bisulfite is gradually added dropwise to the inverse emulsion. Polymerized, the resulting terpolymer can be used as oil well water control agent. As oil well water control fracturing thickener. The preparation process of the product of the invention is simple, and the reaction conditions are easy to control, and is especially suitable for controlling water and increasing oil in reservoirs near water or high water content and low permeability.

Description

A kind of oil well water control agent and preparation method thereof

technical field

The invention relates to an oil well water control agent and a preparation method thereof, in particular to an oil well water control agent or a fracturing water control agent for near water or high water content and low permeability reservoirs.

Background technique

It has always been a difficult problem to implement water control or production stimulation measures and effectively control water production in near-water and high water-cut reservoirs. Production wells produce a large amount of water, which usually leads to a rapid decline in oil production and increased energy consumption for oil production. A large amount of water treatment increases production costs, and also causes other problems such as sand production, corrosion, and scaling. The well was forced to shut down early and stop production due to no economic value of exploitation. Since 1997, the United States has carried out fracturing and stimulation measures for wells with a water content greater than 60% using treatment fluids that change the relative permeability characteristics to Pernran Basin, Kansas, Argentina and other formations, effectively reducing water output and increasing The oil yield is improved, and the post-processing cost is reduced, and the benefit is remarkable. At present, most of the eastern oilfields in my country have entered the middle and late stages of development, and the oil wells are in a state of high water cut; and among the newly explored oil and gas resources, the proportion of oilfields with edge-bottom water and low permeability is increasing. In the process of fracturing and stimulation of such oil reservoirs, fractures often become circulation channels for invalid injection water or edge and bottom water. After fracturing, the water cut rises sharply or even floods, which will bring great risks to oil well fracturing and stimulation.

Carrying out "oil stabilization and water control" is an important way to improve oilfield development benefits. Selecting an efficient water control agent is the key to implementing water control and oil stabilization measures in oil wells. Relevant foreign institutions have been committed to the research and application of interpenetration improvement and water control technology. At present, most of the interpenetration improvement systems are high molecular weight polymers, surfactants (wetting inversion) or polymer cross-linking systems (gel or weak gel), and have been applied in high permeability oilfields, and have a certain degree of water control. Effect. However, in the process of using low-permeability oilfields, there are mainly the following problems: (1) Low-permeability reservoirs have poor physical properties, strong sensitivity, and start-up pressure gradients, while polymers or cross-linked systems have high viscosity and injection pressures High, easy to block crude oil seepage channels and cause reservoir damage; (2) Wetting reversal technology has high construction costs, short water control period, and the effect is difficult to control; (3) Most of the research on relative permeability improvement systems at home and abroad focuses on high-permeability reservoirs Selective water shutoff and field or indoor test effect evaluation.

CN101476452A (CN200910020940.6) discloses a water-controlled fracturing stimulation method for oil and gas wells. During fracturing construction, a plugging layer is formed underground by chemical degradation and covering plugging. It is characterized in that: chemical reaction weight ratio It is: 1000 parts of water, 20-40 parts of paraffin or microcrystalline wax, 180-360 parts of British sand, 3-4 parts of thickener, 7-9 parts of cross-linking agent, 0.29-6.6 parts of additives, (2) construction process The steps are: ①. Heat and melt 50#～70# paraffin wax or microcrystalline wax in the coating machine, add paraffin wax or microcrystalline wax to the quartz sand according to the weight ratio of paraffin wax or microcrystalline wax:quartz sand=1:4.5～18 2. Add a certain amount of water into a container with a pump circulation or agitator, then turn on the pump circulation or agitator, and slowly add the thickener. After adding the additives, continue pumping or stirring for 30 minutes to fully mix the liquid and form a mixed solution. ③. Mix the mixed solution formed in step ② with the cross-linking agent according to the volume ratio of 100:0.7 to form a pre-gel solution. ④. Mix the jelly pre-fluid formed in step ③ with the coated proppant formed in step ① at a weight ratio of 100:30, stir evenly, and pump them into the destination layer.

Contents of the invention

Aiming at the shortcomings of the prior art, the invention provides an oil well water control agent and a preparation method thereof.

Technical scheme of the present invention is as follows:

An oil well water control agent is prepared from the following raw materials:

A, continuous phase: prepared by dissolving sorbitan oleate (Span80) and hydrophobic monomer in oil phase solvent, the mass volume ratio of hydrophobic monomer to oil phase solvent is 1.0-5.0%, the unit is g/ milliliter; the mass volume ratio of sorbitan oleate and oil phase solvent is 5.0-8.0%, and the unit is g/ml;

The hydrophobic monomer is selected from N, N-dimethylacrylamide, methyl acrylate, methyl methacrylate, N-vinylacetamide, N-vinyl-N-methylacetamide, N-vinyl Formamide or N-vinyl-2-pyrrolidone;

B. Disperse phase: acrylamide and 2-acrylamide-2-methylpropanesulfonic acid are used as comonomers, and ammonium persulfate is used as an oxidant, and they are dissolved in water together; acrylamide and 2-acrylamide-2 - The mass ratio of methylpropanesulfonic acid is (85-95): (5-15).

The volume ratio of the oil phase in the above-mentioned continuous phase to the water in the dispersed phase is 3: (2-5);

Add the dispersed phase to the continuous phase to stir and emulsify to obtain an inverse emulsion, adjust the pH value of the inverse emulsion to 7-8, add the reducing agent sodium bisulfite, raise the temperature to 30-70°C to initiate polymerization, and the reaction time is 5-12h. In the polymerization system, the total concentration of acrylamide and 2-acrylamide-2-methylpropanesulfonic acid monomer accounts for 10-40% of the solution mass concentration, and the total mass concentration of ammonium persulfate and sodium bisulfite redox initiator is 10-40%. 0.05-0.5% of the total mass of the above-mentioned monomers.

Finally, the resulting terpolymer is collected from the reactants and is used as an oil well water control agent.

According to the present invention, preferably, the oil phase is kerosene or white oil. The molar ratio of the reducing agent sodium bisulfite to the oxidizing agent ammonium persulfate added in the dispersed phase is 1: (3-6).

The inventive method product terpolymer has following structure:

The contents of the hydrophobic group and the hydrophilic group in the above-mentioned terpolymer are obtained by an elemental analysis method. Among them, preferably, the mass percentages of hydrophobic groups and hydrophilic groups are 3-4% and 7-8%, respectively.

According to the present invention, a kind of preparation method of oil well water control agent comprises the following steps:

1. Mix sorbitan oleate, hydrophobic monomer and oil phase solvent in proportion to form a continuous phase; pass nitrogen gas to remove oxygen for 1-5 hours;

2. Dissolve 2-acrylamido-2-methylpropanesulfonic acid in water, then add acrylamide, add ammonium persulfate as an oxidant, and dissolve in water together to form a dispersed phase; deoxygenate with nitrogen for 1-5 hours;

3. Gradually drop the dispersed phase into the continuous phase and stir rapidly at a speed of 800-1200r/min to form an inverse emulsion, and adjust the pH value of the inverse emulsion to 7-8;

4. Transfer the inverse emulsion system into a constant temperature water bath, stir quickly at a speed of 800-1200r/min for 20-30min, then adjust the speed to 400-600r/min, and add the reducing agent dropwise to the inverse emulsion system while stirring Sodium bisulfite is heated to 30-70°C to initiate polymerization, and the reaction time is 5-12 hours to obtain a white latex-like reaction product terpolymer, which is used as a liquid product of oil well water control agent.

Further, wash the white latex reaction product obtained above with ethanol or acetone for 3-5 times until the weight of the washed product no longer decreases, and finally dry it in vacuum at 40°C for 5-10 hours to obtain a terpolymer powder, which is the oil well water control agent solid product.

Preferably, the above-mentioned reducing agent sodium bisulfite is formulated into an aqueous solution with a mass concentration of 0.1-0.5%. The oxidizing agent ammonium persulfate is prepared into an aqueous solution with a mass concentration of 1-3%.

The application of the oil well water control agent of the present invention is used as a thickener for oil well water control or fracturing water control in oil reservoirs near water or high water content and low permeability.

The preparation process of the product of the present invention is simple, the reaction conditions are easy to control, and the oil-water phase permeability characteristics of the reservoir can be changed or the water-oil ratio can be partially blocked to control the water-oil ratio. At the same time, the product has a fast dissolution rate and has good shear resistance, thermal stability, It has the characteristics of salinity, adsorption and low friction, and is especially suitable for water control and oil production measures in near-water or high water-cut and low-permeability reservoirs.

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

1. The yield of the terpolymer produced by the method of the present invention is as high as 70-95%, and the content of hydrophobic groups and hydrophilic groups in the product can be adjusted in a large range according to needs. The content of hydrophobic groups and hydrophilic groups can be adjusted by adding the hydrophobic monomer in step 1 of the water control agent preparation method and the addition ratio of 2-acrylamido-2-methylpropanesulfonic acid in step 2.

2. The white latex-like reaction product obtained in step 4 of the preparation method of the oil well water control agent in the present invention has a fast dissolution rate and can be directly used in on-site water control measures.

Detailed ways

The present invention will be further described below in conjunction with specific examples, but the protection scope of the present invention is not limited to the scope involved in the examples. The percentage concentrations of ammonium persulfate solution and sodium bisulfite solution in the embodiments are all mass percentages.

Example 1

Add 40ml of kerosene, 3.2g of Span80 and 0.6g of methyl acrylate into a 250ml four-neck flask equipped with a stirrer, dropping funnel, nitrogen tube, and thermometer. After the dissolution is complete, nitrogen is used to remove oxygen for 5 hours to prepare a continuous phase.

Put the beaker into the ice-water mixture, measure 60ml of deionized water and pour it into the beaker, weigh 0.3g of 2-acrylamido-2-methylpropanesulfonic acid into the beaker and stir until it is completely dissolved, adjust the pH value 7-9, then weigh 11.1g of acrylamide and add it to the beaker and stir until it is completely dissolved. Measure 0.9ml of 2% ammonium persulfate solution and add it to the beaker, stir to make it evenly mixed, and deoxygenate with nitrogen for 5 hours to prepare a dispersion Mutually.

Under the condition that the stirring speed is 1000-1200r/min, the dispersed phase is added dropwise to the continuous phase, and the dropwise addition is completed within 10-30 minutes to form a reverse phase emulsion, and the pH value is adjusted to 7-9.

Transfer the inverse emulsion system into a constant temperature water bath at 40°C, continue to stir rapidly at 1000r/min for 30min, then adjust the speed to 400r/min, and add 4ml of 0.1% sodium bisulfite solution to the system, the reaction starts, and the reaction temperature is 40°C , The reaction was stopped after 6h to obtain a viscous milky white latex.

Add the obtained latex drop by drop into 300ml of acetone, stir for 30min, then let it stand at room temperature for 5h, collect the precipitate after the precipitation is complete, put it in a vacuum oven for 72h at 30°C, and obtain a white copolymer powder, which is the present invention The product oil well water control agent.

The product yield is close to 95%, and the intrinsic viscosity of the product is 543ml/g.

A small amount of white copolymer powder was taken to obtain the content of hydrophobic groups and hydrophilic groups in the product by elemental analysis. The results showed that the mass percentages of hydrophobic groups and hydrophilic groups in the product in this example were 2.5% and 7.5%, respectively.

Example 2

As described in Example 1, the difference is that 1.2ml 2% ammonium persulfate solution is added, and 6ml 0.1% sodium bisulfite solution is added to obtain a product yield of 72%, and the product intrinsic viscosity is 343ml/g. Elemental analysis shows that the mass percentages of hydrophobic groups and hydrophilic groups in the product are 3.0% and 7..2%, respectively.

Example 3

As described in Example 1, the difference is that the reaction temperature is 50°C. The yield of the final product was 80%, and the intrinsic viscosity of the product was 843ml/g. Elemental analysis showed that the mass percentages of hydrophobic groups and hydrophilic groups in the product were 3.4% and 7.6%, respectively.

Water control experiment:

The products obtained in Examples 1-3 are used for the water control effect of oil wells, and the oil-water permeability in the pores of reservoir rocks before and after injection of the water control agent can be tested according to the SY/T5358-94 sandstone formation core static flow test program of the People's Republic of China Petroleum and Natural Gas Industry Standard Changes are obtained, and the relevant data are shown in Table 1:

Table 1

As can be seen from Table 1, the product of the present invention can greatly reduce the water phase permeability, reaching more than 70%, but has little influence on the oil phase permeability, and the decline rate is controlled within 20%, and has a good water control effect.

Claims (7)

1. A water control agent for oil wells, characterized in that it is prepared from the following raw materials: A, continuous phase: made by dissolving sorbitan oleate and hydrophobic monomer in oil phase solvent, the mass volume ratio of hydrophobic monomer and oil phase solvent is 1.0-5.0%, unit is gram/ml; The mass volume ratio of sorbitan oleate to the oil phase solvent is 5.0-8.0%, and the unit is g/ml; the hydrophobic monomer is methyl acrylate or methyl methacrylate; B. Disperse phase: acrylamide and 2-acrylamide-2-methylpropanesulfonic acid are used as comonomers, and ammonium persulfate is used as an oxidant, and they are dissolved in water together; acrylamide and 2-acrylamide-2 -The mass ratio of methylpropanesulfonic acid is (85-95): (5-15); The volume ratio of the oil phase in the above-mentioned continuous phase to the water in the dispersed phase is 3: (2-5); Add the dispersed phase to the continuous phase, stir and emulsify to obtain an inverse emulsion, adjust the pH value of the inverse emulsion to 7-8, add the reducing agent sodium bisulfite, raise the temperature to 30-70°C to initiate polymerization, and the reaction time is 5-12h; In the polymerization system, the total concentration of acrylamide and 2-acrylamide-2-methylpropanesulfonic acid monomer accounts for 10-40% of the solution mass concentration, and the total mass concentration of ammonium persulfate and sodium bisulfite redox initiator is 10-40%. 0.05-0.5% of the total mass of the monomers; the terpolymer is collected from the reactants and is an oil well water control agent. 2. The oil well water control agent according to claim 1, characterized in that the oil phase is kerosene or white oil. 3. The oil well water control agent according to claim 1, characterized in that the molar ratio of the reducing agent sodium bisulfite to the oxidizing agent ammonium persulfate in the dispersed phase is 1: (3-6). 4. the preparation method of the described oil well water control agent of any one of claim 1-3, comprises the steps: (1) Mix sorbitan oleate, hydrophobic monomer and oil phase solvent in proportion to form a continuous phase; feed nitrogen gas to remove oxygen for 1-5 hours; (2) Dissolving 2-acrylamido-2-methylpropanesulfonic acid in water, then adding acrylamide, adding ammonium persulfate as an oxidizing agent, and dissolving in water together to form a dispersed phase; passing nitrogen to remove oxygen for 1-5 hours; (3) Gradually drop the dispersed phase into the continuous phase and stir rapidly at a speed of 800-1200r/min to form an inverse emulsion, and adjust the pH value of the inverse emulsion to 7-8; (4) Transfer the inverse emulsion system into a constant temperature water bath, stir rapidly at a speed of 800-1200r/min for 20-30min, then adjust the speed to 400-600r/min, and dropwise add the reducing agent to the inverse emulsion system while stirring Add sodium bisulfite as an agent, raise the temperature to 30-70°C to initiate polymerization, and the reaction time is 5-12 hours to obtain a white latex-like reaction product terpolymer, which is a liquid product of oil well water control agent. 5. The preparation method of oil well water control agent as claimed in claim 4, is characterized in that further, the obtained white latex reaction product is washed 3-5 times with ethanol or acetone until the weight of the washed product no longer decreases, and finally 40 ℃ vacuum Dry for 5-10 hours to obtain terpolymer powder, which is a solid product of oil well water control agent. 6. The preparation method of the oil well water control agent as claimed in claim 4, characterized in that the reducing agent sodium bisulfite is formulated into an aqueous solution with a mass concentration of 0.1-0.5% and added. 7. The preparation method of the oil well water control agent as claimed in claim 4, characterized in that said oxidant ammonium persulfate is added in an aqueous solution having a mass concentration of 1-3%.