CN101323780A - A low-permeability oilfield thermochemical drainage aid and its application - Google Patents

Abstract

The invention discloses a low-permeability oilfield thermochemical drainage aid and its application in the acidification and fracturing process of oil and water wells in the low-permeability oilfield. This thermochemical drainage aid is made up of A agent and B agent, and A agent is made up of phosphoric acid, sodium nitrite, sodium dodecylbenzene sulfonate, emulsifier, surface active agent and water by certain weight percentage, and B agent is made up of certain weight percentage. Composed of urea, ammonium chloride and water in weight percent. Agent A and agent B undergo a thermochemical reaction under certain conditions, producing a large amount of nitrogen, carbon dioxide and high-temperature hot water, accompanied by a large amount of heat; in addition, nitrogen and carbon dioxide with a certain pressure will form under the action of a high-efficiency active foaming agent Lots of foam helps to push debris back out of the oil well. The thermochemical drainage aid is non-flammable and non-explosive, and is mainly used in the acidification of low-permeability oil and water wells and the drainage technology of the fracturing process to solve the problems of insufficient flowback and reduce the pollution of the remaining working fluid to the reservoir, which can effectively Improve acidizing and fracturing effects.

Description

A low-permeability oilfield thermochemical drainage aid and its application

technical field

The invention relates to a thermochemical drainage aid used in the acidification and fracturing process of oil-water wells in low-permeability oilfields and its application.

Background technique

Acidizing is to inject acid liquid into the formation to dissolve the mineral components of the reservoir rock and the substances that cause the clogging of the reservoir during drilling, completion, workover and oil production, so as to improve and enhance the permeability of the reservoir, thereby increasing the production and production of oil wells. Water well injection; fracturing is to use the surface high-pressure pump group to pump high-viscosity fracturing fluid into the well with a displacement exceeding the absorption capacity of the formation to generate fractures in the formation, and add proppant (such as quartz sand, etc.) to fill the fractures to improve The conductivity of the formation, thereby improving the stimulation of oil wells and water wells.

The above two processes are highly valued and widely used as important production stimulation measures in oilfields, but both of them have the problem of flowback of working residual fluid from the formation after operation. Generally, in the early stage of oilfield development, drainage aids are added to acid fluids and fracturing fluids to reduce the surface tension of acidizing or fracturing working fluids, change the wetting status of formations and facilitate the flowback of working fluids, and rely on formation Its own energy returns the remaining working fluid to the ground; however, as the oilfield develops deeper, the formation pressure gradually decreases, and it is difficult for the residual fluid formed after acidizing and fracturing of the oil-water well to be completely self-sustained only by adding drainage aids. discharge. Especially in low-permeability oilfields, working fluid residues will often block the formation after being precipitated in the fluid channel, causing secondary pollution damage to the formation, which affects the process effect to a certain extent, and the secondary damage is difficult to remove in future construction.

In order to solve the problem of acidification of low-permeability oil layers and flowback of working residual fluid after fracturing, oil pump suction was generally used in the past. As the name implies, the mechanical energy of the oil well pump is used to directly suck and lift the working residual fluid back to the ground, but there is flowback The problem of untimely and corroded oil well pump cannot guarantee the normal operation of the pump and affect the production of the oil well.

In recent years, people have developed techniques such as increased injection of liquid nitrogen and liquid carbon dioxide to aid drainage. Liquid nitrogen and liquid carbon dioxide are injected into acidified or fractured oil and water wells, and the residual fluid in the wellbore is lifted by using the physical energy generated by gas expansion. to the ground. In addition, nitrogen is an inert gas with strong stability, large compressibility, large elastic energy, low viscosity, and strong permeability, which is beneficial to maintain oil layer pressure, replenish formation energy, and improve crude oil fluidity. The role of recovery; carbon dioxide is a gas that is highly soluble in both oil and water. When it is dissolved in a large amount of crude oil, it can expand the volume of crude oil, reduce the viscosity and reduce the interfacial tension, so that the crude oil can be more easily driven out by the oil displacement medium, and improve the sweep coefficient and oil washing efficiency; when it is dissolved in water, it can generate carbonic acid. Carbonic acid reacts with limestone and dolomite in the formation to form water-soluble bicarbonate, which improves the permeability of the formation and expands the swept volume of the oil displacement medium, which is beneficial to the improvement of oil recovery.

In short, nitrogen and carbon dioxide, the two drainage aids, have their own unique advantages, but both have problems such as high cost and low flowback pressure. In addition, because the gasification of liquid substances needs to absorb a large amount of heat energy, the temperature of the surrounding environment is reduced, and the flowback effect on low-permeability oil wells with high crude oil viscosity is even less satisfactory.

Contents of the invention

The technical problem to be solved by the present invention is to provide a thermochemical drainage aid suitable for acidizing and fracturing processes of oil and water wells in low-permeability oilfields in view of the above-mentioned deficiencies in the prior art. The use of this thermochemical drainage aid can fully combine the advantages of nitrogen and carbon dioxide as a drainage aid, and at the same time solve the problems of insufficient flowback and high construction costs of the two, and reduce the pollution of the remaining working fluid to the reservoir, effectively Improved acidizing and fracturing effects.

In order to solve the above-mentioned technical problems, the technical solution adopted in the present invention is: a low-permeability oilfield thermochemical drainage aid, characterized in that it is composed of A agent and B agent, and the raw material composition and weight percentage of the A agent are: phosphoric acid 0 ～5%, sodium nitrite 10～30%, sodium dodecylbenzene sulfonate 0.1～1%, emulsifier 0.1～2%, surfactant 0.001～0.1%, balance is water, and described emulsifier is Polyoxyethylene octylphenol ether, the surfactant is a fluorosurfactant.

The preparation method of the A agent is: first add a certain amount of water into the container, and then add the above-mentioned weight percentage of sodium nitrite, sodium dodecylbenzenesulfonate, emulsifier polyoxyethylene octylphenol ether, fluorine surface The active agent and phosphoric acid are stirred evenly to make Agent A.

The raw material composition and weight percentage of the agent B are: 5-20% of urea, 10-20% of ammonium chloride and 60-85% of water.

The preparation method of the B agent is as follows: put the urea and ammonium chloride in the above weight percentage in another container, add the water in the above weight percentage, stir evenly, and prepare the B agent after it is completely dissolved.

Another object of the present invention is to provide the application of a low-permeability oilfield thermochemical drainage aid in the acidizing and fracturing process of oil-water wells in low-permeability oilfields.

The technical principle on which the present invention is based:

After the thermochemical drainage aid is injected into the formation, under certain conditions in the formation, the chemical reaction of the thermochemical drainage aid will be triggered, and a large amount of nitrogen and carbon dioxide will be generated at the same time accompanied by a large amount of heat. Relying on the thermal energy of these chemical reactions and the physical energy of gas expansion, supplement Formation energy and discharge working residual fluid.

Its chemical reaction equation is:

CO(NH ₂ ) ₂ +NH ₄ ⁺ +3NO ₂ ^- +2H ⁺ →3N ₂ ↑+CO ₂ ↑+5H ₂ O+Q (heat).

Phosphoric acid in agent A of the present invention plays a role in catalyzing the reaction of sodium nitrite, ammonium chloride and urea. The content of phosphoric acid plays an important role to the thermochemical reaction rate of both, if the selected phosphoric acid consumption exceeds the scope of the present invention, all can't receive good reaction effect. It is worth pointing out that phosphoric acid does not need to be used as an initiation catalyst in the acidification process, because the acid in the acidification working fluid can catalyze the reaction. In addition, various chemical additives other than sodium nitrite and phosphoric acid cooperate with each other to achieve the effect of high-efficiency active foaming, which cannot be achieved by a single component. The content range of each component in this formula is also the optimized result obtained after many tests, and only within this proportion range can a satisfactory effect be achieved.

The mixed use of urea and ammonium chloride in agent B of the present invention is the optimization result after comprehensively considering the efficiency of thermochemical reaction to generate heat and the optimal volume ratio of reaction product nitrogen and carbon dioxide, so their content percentage has a great impact on the effect of drainage. It plays a key role and is also the result of multiple test screenings.

Compared with the prior art, the present invention has the following advantages: the thermochemical drainage aid of the present invention is composed of agent A and agent B, and agent A and agent B undergo a thermochemical reaction under certain conditions to produce a large amount of nitrogen, carbon dioxide and high-temperature hot water , accompanied by a large amount of heat; in addition, nitrogen and carbon dioxide with a certain pressure will form a large amount of foam under the action of a high-efficiency active foaming agent, which helps to return the residual liquid residue to the oil and water well. The thermochemical drainage aid is non-flammable and Non-explosive, complete flowback, no pollution to the formation.

The technical solutions of the present invention will be described in further detail below through examples.

Detailed ways

Each raw material of the following examples is by weight percentage.

Example 1

Preparation of agent A: first add 78.68% water to the container, then add 21% sodium nitrite, 0.15% sodium dodecylbenzenesulfonate, 0.15% emulsifier polyoxyethylene octylphenol ether, 0.02% The fluorosurfactant is made into agent A after stirring evenly.

Preparation of agent B: put 12% urea and 12% ammonium chloride in another container, add 76% water, stir evenly, and prepare agent B after it is completely dissolved.

Example 2

Preparation of agent A: first add 78.08% water to the container, then add 21% sodium nitrite, 0.15% sodium dodecylbenzenesulfonate, 0.15% emulsifier polyoxyethylene octylphenol ether, 0.02% Fluorosurfactant and 0.6% phosphoric acid, stir well to make A agent.

Preparation of agent B: put 5% urea and 10% ammonium chloride in another container, add 85% water, stir evenly, and prepare agent B after it is completely dissolved.

Example 3

Preparation of agent A: first add 89.6% water to the container, then add 10% sodium nitrite, 0.10% sodium dodecylbenzenesulfonate, 0.10% emulsifier polyoxyethylene octyl phenol ether, 0.001% Fluorosurfactant and 0.199% phosphoric acid are mixed evenly to make Agent A.

Preparation of agent B: put 20% urea and 20% ammonium chloride in another container, add 60% water, stir evenly, and prepare agent B after it is completely dissolved.

Example 4

Preparation of agent A: first add 61.9% water to the container, then add 30% sodium nitrite, 1% sodium dodecylbenzenesulfonate, 2% emulsifier polyoxyethylene octylphenol ether, 0.1% Fluorosurfactant and 5% phosphoric acid, stir well to make Agent A.

Preparation of agent B: put 15% urea and 15% ammonium chloride in another container, add 70% water, stir evenly, and prepare agent B after it is completely dissolved.

Example 5

Preparation of agent A: first add 81.95% water to the container, then add 15% sodium nitrite, 0.5% sodium dodecylbenzenesulfonate, 0.5% emulsifier polyoxyethylene octyl phenol ether, 0.05% Fluorosurfactant and 2% phosphoric acid, stir well to make Agent A.

Preparation of agent B: put 16% urea and 16% ammonium chloride in another container, add 68% water, stir evenly, and prepare agent B after it is completely dissolved.

Example 6

Preparation of agent A: first add 70.33% water to the container, then add 26% sodium nitrite, 0.3% sodium dodecylbenzenesulfonate, 0.3% emulsifier polyoxyethylene octyl phenol ether, 0.07% Fluorosurfactant and 3% phosphoric acid, stir well to make Agent A.

Preparation of agent B: put 10% urea and 10% ammonium chloride in another container, add 80% water, stir evenly, and prepare agent B after it is completely dissolved.

1. For the application of the thermochemical drainage aid of the present invention in the acidizing process of oil and water wells in low-permeability oilfields, it is suggested to carry out the following technical operation procedures: for example, the thickness of the reservoir is 32 meters, the porosity is 12%, and the treatment radius is 3 meters. The total acidification treatment dosage is 130 cubic meters.

When operating, first fully flush the well with hot reinjection water.

1. Squeeze into 10 square meters of agent A, which is composed of the following raw materials in percentage by weight: 21% sodium nitrite, 0.15% sodium dodecylbenzenesulfonate, 0.15% polyoxyethylene octylphenol ether, fluorine surface Active agent 0.02% and water 78.68%;

2. Squeeze 5 squares of spacer liquid, which is an aqueous solution containing 1% potassium chloride;

3. Squeeze in 20 cubic meters of pre-fluid: the pre-fluid is an aqueous solution containing 5% hydrochloric acid and 1% potassium chloride;

4. Squeeze 5 squares of spacer liquid, which is an aqueous solution containing 1% potassium chloride;

5. Squeeze 5 squares of agent B, which is composed of the following raw materials in percentage by weight: 12% urea, 12% ammonium chloride and 76% water;

6. Squeeze 5 squares of spacer liquid, which is an aqueous solution containing 1% potassium chloride;

7. Squeeze 60 cubic meters of main acid: the main acid is 10% hydrochloric acid + 6% hydrofluoric acid + 2% iron ion stabilizer + 1% acidification corrosion inhibitor + 1% mutual solvent + 1% potassium chloride aqueous solution ; The mutual solvent is ethylene glycol monobutyl ether;

8. Squeeze in 20 square meters of displacement liquid: the displacement liquid is an aqueous solution of 0.5% OP10 active agent + 1% potassium chloride;

9. Close the well for 4 to 6 hours;

10. Backwash well to discharge acid: the outlet flowback liquid is tested with pH test paper until the discharged liquid is neutral, and the backflow can be stopped;

11. Pull out the construction pipe string, lower it into the production pipe string, and open the well for production.

The main advantages of the thermochemical drainage aid of the present invention being applied to the acidification process are:

1) The large amount of heat and inert gas generated by the chemical reaction of the thermochemical drainage aid can effectively clean the organic scale in the formation and improve the subsequent acidification efficiency;

2) The heat energy generated by the chemical reaction can reduce the viscosity of colloids and asphaltenes, demulsify the oil-water emulsion, and also have a strong deblocking effect;

3) Nitrogen is an inert gas with strong stability. Under the action of high temperature and high pressure, it can effectively clean the wellbore, remove pollution and blockage near the wellbore, increase its permeability, and effectively improve the fluidity of crude oil; carbon dioxide can make crude oil easier to flow The flooding of the oil-displacement medium increases the sweep coefficient and oil washing efficiency, and at the same time increases the permeability of the formation and expands the swept volume of the oil-displacement medium, which is conducive to improving the recovery of crude oil.

4) Thermochemical drainage is a chemical reaction in the formation, relying on the heat energy of the chemical reaction and the physical method of gas expansion to discharge the residual acid. The generated inert gas and foaming agent components form a large amount of stable foam, reducing the residual acid in the well. The liquid column pressure and frictional resistance can accelerate the residual acid flowback, reduce the pollution of the residual acid to the formation, and strengthen the acidizing effect.

Two, the application of the thermochemical drainage aid of the present invention in the fracturing process of oil-water wells in low-permeability oilfields, taking the total medicament treatment volume of 195 cubic meters as an example, the following technical operation procedures are suggested:

1. Pressure test;

2. Pump in the pre-fluid (the pre-fluid can be water-based jelly fracturing fluid, mainly composed of 95.8% of water, 2% of gelling agent polyacrylamide, 2% of cross-linking agent hexamethylenetetramine and fracturing fluid. Adhesive agent sodium persulfate 0.2% made up): construction pressurization, pressure to open the formation, the pressure gradually decreases, the dosage is 70 cubic meters;

3. Squeeze the sand-carrying fluid (the sand-carrying fluid refers to adding a certain amount of proppant such as quartz sand to the above-mentioned water-based jelly fracturing fluid): after the pressure gradually drops to the working pressure, start adding 10 square meters of sand, The amount of liquid used is 55 cubic meters, and the average sand ratio is 18.2%;

4. Squeeze in 20 square meters of displacement solution (the displacement solution is an aqueous solution of 0.5% OP10 active agent+1% potassium chloride);

5. Squeeze in 20 square meters of thermochemical row-aid A agent, said A agent is made up of the following raw materials in percentage by weight: sodium nitrite 21%, phosphoric acid 0.6%, sodium dodecylbenzene sulfonate 0.15%, polyoxyethylene octyl 0.15% phenol ether, 0.02% fluorosurfactant and 78.08% water;

6. Squeeze 10 cubic meters of spacer liquid, which is an aqueous solution containing 1% potassium chloride;

7. Squeeze in 10 square meters of thermochemical anti-drainage agent B, which is composed of the following raw materials in percentage by weight: 12% urea, 12% ammonium chloride and 76% water;

8. Well shut-in reaction for 2-4 hours;

9. Open the well to discharge and discharge liquid, and use pH test paper to test the discharge liquid at the outlet until the discharge liquid is neutral, then stop the reverse discharge;

10. Pull out the construction pipe string, lower it into the production pipe string, and open the well for production.

The main advantages of the application of the thermochemical drainage aid of the present invention in the fracturing (water-based) process are:

1) Make the water-based jelly break quickly and completely;

2) Corrosion cracks, increase the conductivity;

3) The large amount of heat energy generated can reduce the viscosity and degrade the polymer macromolecules in the fracturing fluid;

4) Partially discharge the pollutants to the ground to reduce secondary pollution and improve the effect of measures.

Claims (2)

1. low pervasion oilfield thermochemical cleanup additive, it is characterized in that forming by A agent and B agent, the raw material of described A agent is formed and weight percent is: phosphoric acid 0～5%, Sodium Nitrite 10～30%, Sodium dodecylbenzene sulfonate 0.1～1%, emulsifying agent 0.1～2%, tensio-active agent 0.001～0.1%, surplus is a water, and described emulsifying agent is a polyoxyethylene octyl phenol ether, and described tensio-active agent is a fluorine surfactant;

The raw material of described B agent is formed and weight percent is: urea 5～20%, ammonium chloride 10～20%, water 60～85%.

2. the application of a kind of low pervasion oilfield thermochemical cleanup additive as claimed in claim 1 in acidifying of low permeability oil field oil and water well and fracturing technology.