CN108148568A - A kind of cross-linking agent for liquid preparation of oilfield produced water and preparation method thereof - Google Patents

Abstract

The invention discloses a cross-linking agent for oil field produced water liquid preparation and a preparation method thereof, wherein the cross-linking agent comprises, by weight, 8% -15% of sorbitol, 12% -25% of cationic polystyrene sulfonate, 10% -20% of a solvent, 3% -5% of an initiator, 3% -5% of a catalyst and the balance of water. The preparation method comprises the steps of adding sorbitol and cationic polystyrene sulfonate according to the formula amount into a reactor, adding solvent and initiator according to the formula amount, adding catalyst according to the formula amount, stirring and heating under the condition of water vacuumizing, and reacting for 3-6 hours to obtain colorless transparent liquid. The cross-linking agent prepared by the invention has stronger salt resistance, simultaneously takes certain oil resistance into consideration, so that the cross-linking agent can be suitable for preparing fracturing fluid from various oilfield produced water, has good sand carrying property compared with a gel type fracturing fluid system, and can meet the requirement of high sand carrying property in the practical application process.

Description

A kind of cross-linking agent for liquid preparation of oilfield produced water and preparation method thereof

technical field

The invention relates to the field of petroleum exploitation, in particular to a crosslinking agent for liquid preparation of oilfield produced water and a preparation method thereof.

Background technique

Hydraulic fracturing technology is a key technology for low-permeability reservoir reconstruction. Hydraulic fracturing needs to consume a large amount of fresh water, which has an impact on local water resources, especially in water-scarce areas. At present, domestic environmental protection requirements have been significantly improved.

With the deepening of oilfield development, the comprehensive water content gradually increases, and the cost of harmless treatment of a large amount of produced water is high and the efficiency is low. If the produced water can be used to prepare fracturing fluid, it is of great significance for the green development of the oilfield and cost reduction and efficiency increase.

Oilfield produced water generally has the characteristics of "high bacterial content, high salinity, and high mechanical impurities", and its composition is complex. The thickener synthesized to prepare fracturing fluid for oilfield produced water has a side chain structure of hydrophobic groups, and has a specific viscosity response only under the action of a specific surfactant. Conventional surfactants have certain limitations in promoting the cross-linking of hydrophobic associations to form a spatial network structure, and some surfactants lose their activity in the specific high-salt, oil-containing, and bacteria-containing water environment of produced water. As the amount of different surfactants increases, the apparent viscosity of the solution tends to increase, but when the amount of surfactant is too large, the viscosity will decrease. The reason is that the low concentration of surfactants forms micelles, and the hydrophobic side chains are entangled in the micelles to form a dense supramolecular structure and a spatial network structure, resulting in an increase in the apparent viscosity. The number of micelles formed increases, the average number of hydrophobic units in each micelle decreases, and the spatial network structure is destroyed, so that the viscosity of the solution decreases macroscopically.

Contents of the invention

Aiming at the problems existing in the above-mentioned prior art, the present invention discloses a crosslinking agent for liquid preparation of oilfield produced water with salt resistance, oil resistance, certain suspended matter resistance and strong adaptability to strata and a preparation method thereof.

The technical scheme adopted in the present invention is as follows:

A crosslinking agent for liquid preparation of oilfield produced water, which is composed of the following components in weight percent: sorbitol 8%-15%, cationic polystyrene sulfonate 12%-25%, solvent 10-20%, initiator 3% to 5%, catalyst 3% to 5%, and the rest is water.

The substance ratio of the sorbitol to the cationic polystyrene sulfonate is 1: (1.5-3.5).

The cationic polystyrene sulfonate is a light amber liquid with a molecular weight of 100,000-200,000.

The cationic polystyrene sulfonate is one of polystyrene sulfonic acid, sodium polystyrene sulfonate and potassium polystyrene sulfonate.

Described solvent is a kind of in methanol, ethylene glycol, ether, glycerol.

The initiator is one of ammonium persulfate, sodium persulfate and sodium perbromate.

The catalyst is one of sodium hydroxide, potassium hydroxide and sodium bicarbonate.

The preparation method of the cross-linking agent for the liquid preparation of a kind of oilfield produced water is that the specific operation steps of the preparation method are as follows: add the sorbitol and cationic polystyrene sulfonate of the formula amount into the reactor, and add the formula A certain amount of solvent and initiator, and add a formula amount of catalyst, under the condition of water vacuum, stir and heat up to 180-190°C, and react for 3-6 hours to obtain a colorless and transparent liquid, which is to prepare fracturing with oilfield produced water liquid crosslinking agent.

The beneficial effects of the present invention are:

1. the charged ionic group (comprising ether group, methylene group, sulfonic acid group) in cationic polystyrene sulfonate and sorbitol in the cationic polystyrene sulfonate and sorbitol of the present invention prepares the fracturing fluid cross-linking agent monomer , vinyl, etc.) The electrostatic repulsion and attraction compete and cooperate with each other, which can promote the mutual association of hydrophobic groups, make the macromolecular chains produce intramolecular or intermolecular associations, and form a supramolecular network structure with a higher degree of aggregation. Compared with jelly-based fracturing fluid systems, it has better sand-carrying properties and can meet the high sand-carrying requirements in practical applications;

2. The crosslinking agent of the present invention for preparing fracturing fluids in oilfield produced water has strong salt resistance due to the attraction of sulfonic acid groups to cations, and at the same time, polar groups can absorb a certain amount of crude oil and take into account appropriate oil resistance properties, so that It can be applied to prepare fracturing fluid with produced water in various oilfields;

3. The cross-linking agent used to prepare fracturing fluid for oilfield produced water of the present invention has good compatibility with fracturing fluid, and no precipitation is formed when adding a cross-linking agent with a volume concentration of 0.3% in the fracturing base fluid;

4. The raw materials used in the present invention are readily available, and the preparation process of the crosslinking agent is simple.

Detailed ways

The present invention is described in detail below by specific embodiment:

Example 1

The invention discloses a crosslinking agent for liquid preparation of oilfield produced water and a preparation method thereof. The crosslinking agent is composed of the following components in weight percent: sorbitol 8% to 15%, cationic polystyrene sulfonate 12% %-25%, solvent 10-20%, initiator 3-5%, catalyst 3%-5%, and the rest is water.

The specific operation steps of the preparation method of the crosslinking agent are as follows: add the sorbitol and the cationic polystyrene sulfonate of the formula quantity in the reactor, add the solvent and the initiator of the formula quantity simultaneously, and add the catalyst of the formula quantity, water Under vacuum conditions, stir and heat up to 180-190°C, react for 3-6 hours, and obtain a colorless and transparent liquid, which is the cross-linking agent for oilfield produced water.

The cross-linking agent prepared by the invention has strong salt-resistant performance, and at the same time takes into account certain oil-resistant and suspended matter-resistant properties, making it suitable for preparing fracturing fluids with produced water from various oil fields.

Example 2

On the basis of Example 1, sorbitol is used to react with cationic polystyrene sulfonic acid or polystyrene sulfonate, the ratio of the two substances is 1: (1.5～3.5), and 10-20% solvent is added at the same time And 3-5% initiator, add 3%-5% catalyst, under the condition of water vacuum, stir and heat up to 180-190°C, react for 3-6 hours, and obtain a colorless transparent liquid, which is oilfield produced water Cross-linking agent for solution.

The cationic polystyrene sulfonate is a light amber liquid with a molecular weight of 100,000-200,000; the cationic polystyrene sulfonate is polystyrene sulfonic acid, sodium polystyrene sulfonate, polystyrene One of the potassium sulfonates.

Described solvent is a kind of in methanol, ethylene glycol, ether, glycerol.

The initiator is one of ammonium persulfate, sodium persulfate and sodium perbromate.

The catalyst is one of sodium hydroxide, potassium hydroxide and sodium bicarbonate.

Cationic polystyrene sulfonate and charged ionic groups in sorbitol (comprising ether group, methylene group, sulfonic acid group, ethylene group) The electrostatic repulsion and attraction of groups, etc.) compete and cooperate with each other, which can promote the mutual association of hydrophobic groups, make macromolecular chains produce intramolecular or intermolecular associations, and form a supramolecular network structure with a higher degree of aggregation. The gel-based fracturing fluid system has good sand-carrying properties and can meet the high sand-carrying requirements in the actual application process; and the raw materials used in the present invention are readily available, and the preparation process of the crosslinking agent is simple.

The process of preparing fracturing fluid with the crosslinking agent prepared by the present invention is consistent with the conventional fracturing fluid preparation method, except that the conventional preparation method uses clear water, and the present invention uses oilfield produced water containing oily suspended matter, crude oil, mechanical impurities, etc. The cross-linking agent has good compatibility with the fracturing fluid, and the cross-linking agent with a volume concentration of 0.3% is added to the fracturing base fluid without precipitation.

Example 3

On the basis of the foregoing examples, a three-necked flask with magnetic stirring and a thermometer is placed on a magnetic stirrer temperature control electric heating mantle, and 8% sorbitol and 12% polystyrene sulfonic acid (sorbitol and The material ratio of polystyrene sulfonic acid is 1:1.5), while adding 10% methanol and 3% sodium persulfate, adding 3% sodium hydroxide, 64% water, stirring and heating up under the condition of water vacuum to 180°C, and continuously stirred for 6 hours to obtain a colorless transparent liquid, which is the cross-linking agent for oilfield produced water preparation.

Example 4

The three-necked flask with magnetic stirring and thermometer is placed on the magnetic stirrer temperature control electric heating mantle, adds 11.5% sorbitol and 18.5% sodium polystyrene sulfonate (the content of sorbitol and sodium polystyrene sulfonate) in the three-necked flask The molar ratio of the substance is 1:2.5), while adding 15% ethylene glycol and 4% ammonium persulfate, adding 4% potassium hydroxide, and 47% water; the water is stirred and heated to 183 ° C under vacuum conditions, Continue stirring for 5 hours to obtain a colorless transparent liquid, which is a cross-linking agent for preparing fracturing fluid from oilfield produced water.

Example 5

The three-necked flask equipped with magnetic stirring and thermometer is placed on the magnetic stirrer temperature control electric heating mantle, and 9% sorbitol and 23% sodium polystyrene sulfonate (the content of sorbitol and sodium polystyrene sulfonate) are added to the three-necked flask. The molar ratio is 1:3), while adding 15% ether and 5% sodium perbromate, adding 4% sodium hydroxide, and 44% water; stir and heat up to 188°C under the condition of water pumping, and continue to stir After 3 hours, a colorless transparent liquid is obtained, which is used as a cross-linking agent for oil field produced water to prepare fracturing fluid.

Example 6

The three-necked flask equipped with magnetic stirring and thermometer is placed on the magnetic stirrer temperature control electric heating mantle, and 12% sorbitol and 21% sodium polystyrene sulfonate (the content of sorbitol and sodium polystyrene sulfonate) are added to the three-necked flask. The molar ratio of the substances is 1:1.75), while adding 12% ethylene glycol and 3% ammonium persulfate, adding 4% potassium hydroxide, and 48% water; the water is stirred and heated to 183 ° C under vacuum conditions, Continue stirring for 5 hours to obtain a colorless transparent liquid, which is a cross-linking agent for preparing fracturing fluid from oilfield produced water.

Example 7

The three-necked flask with magnetic stirring and thermometer is placed on the magnetic stirrer temperature control electric heating mantle, in the three-necked flask, add 15% sorbitol and 25% potassium polystyrene sulfonate (the mol ratio of sorbitol and potassium polystyrene sulfonate 1:3.5), add 20% glycerol and 5% sodium persulfate at the same time, add 5% sodium bicarbonate, 30% water; stir and heat up to 190 ° C under the condition of water vacuum, continue to stir for 4 hours, The obtained colorless transparent liquid is used as a cross-linking agent for oilfield produced water to prepare fracturing fluid.

Example 8

The thickener synthesized to prepare fracturing fluid for oilfield produced water has a side chain structure of hydrophobic groups, and has a specific viscosity response only under the action of a specific surfactant. Conventional surfactants have certain limitations in promoting the cross-linking of hydrophobic associations to form a spatial network structure, and some surfactants lose their activity in the specific high-salt, oil-containing, and bacteria-containing water environment of produced water. A large number of cross-linking agents have been screened in the laboratory, and the concentration of products with thickening ability is determined. The thickening performance of different types of surfactants is shown in the following table 1:

Table 1 is optimized for the cross-linking agent of produced water preparation thickener

Viscosity changes under different crosslinking agent concentrations in table 2

As the amount of different surfactants increases, the apparent viscosity of the solution tends to increase, but when the amount of surfactants is too large, the viscosity will decrease (as shown in Table 2). The reason is that the low concentration of surfactants Micelles are formed, and the hydrophobic side chains are entangled in the micelles to form a dense supramolecular structure and a spatial network structure, resulting in an increase in the apparent viscosity. With the increase of the dosage, the number of micelles formed by the surfactant increases, and the average The number of hydrophobic units in each micelle is reduced, and the spatial network structure is destroyed, so that the viscosity of the solution decreases macroscopically. Among several types of surfactants, the crosslinking agent of the present invention has the best performance, has a wide application range of concentration, and satisfies the conditions of on-site construction.

Claims (8)

1. a kind of oil field extracted water matches liquid crosslinking agent, it is characterised in that：The crosslinking agent is by following components in percentage by weight Composition：Sorbierite 8%~15%, cation polystyrene sulfonate 12%~25%, solvent 10~20%, initiator 3~ 5%, catalyst 3%~5%, remaining is water.

2. a kind of oil field extracted water according to claim 1 matches liquid crosslinking agent, it is characterised in that：The sorbierite with The amount ratio of the substance of cation polystyrene sulfonate is 1：(1.5-3.5).

3. a kind of oil field extracted water according to claim 1 matches liquid crosslinking agent, it is characterised in that：The cation gathers Styrene sulfonate is light amber liquid, and molecular weight is 10-20 ten thousand.

4. a kind of oil field extracted water according to claim 1 matches liquid crosslinking agent, it is characterised in that：The cation gathers Styrene sulfonate is polystyrolsulfon acid, one kind in kayexalate, polystyrolsulfon acid potassium.

5. a kind of oil field extracted water according to claim 1 matches liquid crosslinking agent, it is characterised in that：The solvent is first One kind in alcohol, ethylene glycol, ether, glycerine.

6. a kind of oil field extracted water according to claim 1 matches liquid crosslinking agent, it is characterised in that：The initiator is One kind in ammonium persulfate, sodium peroxydisulfate, perbromic acid sodium.

7. a kind of oil field extracted water according to claim 1 matches liquid crosslinking agent, it is characterised in that：The catalyst agent For one kind in sodium hydroxide, potassium hydroxide, sodium bicarbonate.

8. match the preparation method of liquid crosslinking agent, feature according to a kind of oil field extracted water of claim 1-7 any one of them It is, the concrete operation step of this method is as follows：The sorbierite of formula ratio is reacted with the addition of cation polystyrene sulfonate In device, while the solvent and initiator of formula ratio are added in, and add in the catalyst of formula ratio, under conditions of water evacuation, stirring 180-190 DEG C is warming up to, is reacted 3-6 hours, obtained colourless transparent liquid is that oil field extracted water matches liquid crosslinking agent.