CN105885817A - Clean fracturing fluid gel breaker and application of fracturing fluid in low permeability-ultra-low permeability oil and gas reservoirs - Google Patents

Abstract

The invention discloses a clean fracturing fluid gel breaker and the application of the fracturing fluid in low-ultra-low permeability oil and gas reservoirs, belonging to the petrochemical field. Aiming at the shortage of existing clean fracturing fluids, a clean fracturing fluid gel breaker with controllable gel breaking and good gel breaking performance, suitable for low-permeability-ultra-low permeability oil and gas reservoirs at a temperature of 20-90°C and its application is provided . The gel breaker for the clean fracturing fluid, relative to the total mass of the fracturing fluid, the added mass of the gel breaker is 0.03-2.00%, and the gel breaker is lauric acid; the clean fracturing fluid is composed of components expressed in mass fractions : Thickener 0.80-4.00%, cross-linking agent 0.50-2.00%, gel breaker 0.03-2.00%, regulator 0.02-1.00%, and the balance is dosing water. This clean fracturing fluid can be used in oil and gas wells with a formation temperature between 20 and 90°C. It has good gel breaking performance, and the solution after gel breaking is clear without residue and emulsification; the gel breaking time is 60 to 300 minutes , which can meet the sand-carrying requirements of fracturing fluid.

Description

Application of a clean fracturing fluid gel breaker and its fracturing fluid in low-ultra-low permeability oil and gas reservoirs

technical field

The invention belongs to the petrochemical field, and in particular relates to a gel breaker for clean fracturing fluid and the application of the fracturing fluid in low-permeability-ultra-low-permeability oil and gas reservoirs.

Background technique

In the fracturing process, the agent that can break the gel of the clean fracturing fluid in a controlled manner, and can break the gel of the jelly fracturing fluid is called a gel breaker. The ideal gel breaker should maintain Ideally high viscosity, once the pumping is complete, the liquid immediately breaks into water. Gel breakers are the main components in fracturing fluids. The gel breakers commonly used in the field can be classified into the following categories: 1 Peroxides, such as ammonium persulfate, potassium persulfate, etc., the use temperature is above 50°C, when the use temperature is lower than 50°C, it releases free oxygen The speed of the fracturing fluid slows down or stops, and it does not play or partially break the gel in the fracturing fluid, and it is a non-specific reactant, which can react with any reactant encountered such as tubing, formation matrix and hydrocarbons, etc. , to generate pollutants that are incompatible with the formation, causing formation damage; 2. Enzyme, which can be used to break the gel at a lower temperature, but must be maintained at a low pH value when used, so that the enzyme can break the gel. The use conditions and expensive cost restrict its large-scale application; 3-capsule gel breaker is a delayed gel breaker, suitable for high temperature fracturing fluid gel breaker.

Clean fracturing fluid is a non-residue fracturing fluid system that has emerged in recent years. At present, the gel breaking method of clean fracturing fluid is mainly a large amount of formation water or oil (hydrocarbon), but it is difficult to break gel in practical application. Disadvantages such as flowback and sand spitting, poor production increase effect, etc. Chinese patent 200910208522.X discloses a low-cost water-based clean fracturing fluid and gel-breaking fluid for fracturing. When the water-based clean fracturing fluid is used at a low concentration, the fracturing fluid cannot be completely broken. When the concentration is high, the gel breaking speed is too fast, and the sand carrying requirement cannot be met.

Low-molecular-weight alcohols currently on the market, such as n-pentanol and n-octanol, have a gel-breaking effect on clean fracturing fluids. If the fluid breaks the gel too quickly, it cannot meet the requirements of sand carrying, that is, there is a defect that the gel breaking time cannot be controlled, and it cannot meet the requirements of on-site fracturing construction.

In the study of clean fracturing fluids in oilfields, commonly used oxidative breakers ammonium persulfate and surfactant sulfonates were used as breakers. The viscosity of the fracturing fluid decreases by different values, but the gel breaking effect is too fast, and the viscosity of the fracturing fluid can be reduced to a constant value within 30 minutes.

Chinese patent 201310571931.2, A Viscoelastic Surfactant Cleaning Fracturing Fluid Breaker and Its Application Although the breaker is disclosed as a mixture of lauric acid and alkylphenol polyoxyethylene ether, lauric acid alone is used as a breaker When in use, since lauric acid is insoluble in viscoelastic clean fracturing fluid, the gel breaking is not complete or the gel breaking effect cannot be achieved. Therefore, it is necessary to add other ingredients to the gel breaker to improve the gel breaking performance.

Contents of the invention

The object of the present invention is to address the above defects, to provide a clean fracturing fluid with controllable gel breaking and good gel breaking performance, suitable for a temperature of 20-90°C and its application in low-ultra-low permeability oil and gas reservoirs.

The invention provides a gel breaker for clean fracturing fluid. Relative to the total mass of the fracturing fluid, the added mass of the gel breaker is 0.03-2.00%, and the gel breaker is lauric acid.

The present invention also provides a clean fracturing fluid containing the above-mentioned gel breaker, which is composed of components recorded in mass fraction:

Thickener 0.80～4.00%,

crosslinking agent 0.50～2.00%,

Breaker 0.03～2.00%,

Regulator 0.02～1.00%,

The balance is the dosing water.

The thickener is cetyltrimethylammonium chloride or octadecyltrimethylammonium chloride.

The crosslinking agent is sodium salicylate.

The regulator is caustic soda (sodium hydroxide).

Further, the present invention provides the application of the above-mentioned clean fracturing fluid breaker in low-ultra-low permeability oil and gas reservoirs for fracturing oil and gas wells with a formation temperature of 20-90°C.

Furthermore, the present invention provides the application of the above-mentioned clean fracturing fluid in low-ultra-low-permeability oil and gas reservoirs, for fracturing oil and gas wells with a formation temperature of 20-90°C.

The specific method of using the fracturing fluid of the present invention is as follows: at the application site, slowly add a thickener and a crosslinking agent in the liquid preparation water according to the mass percentage, stir and mix evenly, add a regulator to adjust the pH value of the mixed solution to 8-10, stir evenly, Then it is mixed with a fracturing proppant to form a sand mixing fluid. During fracturing construction, the gel breaker is conically added to the sand mixing fluid. The fracturing proppant is a conventional reagent in the field.

The present invention has following beneficial effect:

The clean fracturing fluid of the present invention can be used in oil and gas wells in low-permeability-ultra-low-permeability oil and gas reservoirs where the formation temperature is between 20 and 90°C, and has good gel breaking performance, and the solution after gel breaking is clear without residue and emulsification; the present invention The gel breaking time of the clean fracturing fluid is 60-300 minutes, which is controllable and can meet the sand-carrying requirements of the fracturing fluid during fracturing construction.

Description of drawings

Fig. 1 is the viscosity curve of the fracturing fluid with different concentrations of gel breakers added in Example 5 at 30°C;

Fig. 2 is the viscosity curve of the fracturing fluid with different concentrations of gel breakers in Example 6 at 35°C;

Fig. 3 is the fracturing fluid viscosity-temperature curve of ammonium persulfate as gel breaker in embodiment 7;

Fig. 4 is the fracturing fluid viscosity-temperature curve of the sulfonate used as the breaker in Example 7.

detailed description

The present invention will be further described by the specific examples given below, but not as a limitation of the present invention.

In all the following embodiments of the present invention, formation water is selected as the dosing water.

Example 1

The fracturing fluid of the present invention is made up of the composition of mass fraction record:

Thickener 0.80%,

crosslinking agent 0.50%,

Lauric acid 0.03%,

Regulator 0.02%,

The balance is formation water.

The thickener is cetyltrimethylammonium chloride or octadecyltrimethylammonium chloride.

The crosslinking agent is sodium salicylate.

The regulator is caustic soda (sodium hydroxide).

When the fracturing fluid is applied to the site, slowly add thickener and crosslinking agent to the formation water according to the mass percentage, stir and mix evenly, add a regulator to adjust the pH of the mixed fluid to 8-10, stir evenly, and then mix with the fracturing support Mixing agent to form a sand mixing fluid, and the gel breaker is conically added to the sand mixing fluid during fracturing construction.

Example 2

The fracturing fluid of the present invention is made up of the composition of mass fraction record:

Thickener 1.50%,

crosslinking agent 0.80%,

Lauric acid 1.25%,

Regulator 0.03%,

The balance is formation water.

The thickener is cetyltrimethylammonium chloride or octadecyltrimethylammonium chloride.

The crosslinking agent is sodium salicylate.

The regulator is caustic soda (sodium hydroxide).

When the fracturing fluid is applied to the site, slowly add thickener and crosslinking agent to the formation water according to the mass percentage, stir and mix evenly, add a regulator to adjust the pH of the mixed fluid to 8-10, stir evenly, and then mix with the fracturing support Mixing agent to form a sand mixing fluid, and the gel breaker is conically added to the sand mixing fluid during fracturing construction.

Example 3

The fracturing fluid of the present invention is made up of the composition of mass fraction record:

Thickener 1.50%,

crosslinking agent 0.80%,

Lauric acid 1.10%,

Regulator 0.025%,

The balance is formation water.

The thickener is cetyltrimethylammonium chloride or octadecyltrimethylammonium chloride.

The crosslinking agent is sodium salicylate.

The regulator is caustic soda (sodium hydroxide).

When the fracturing fluid is applied to the site, slowly add thickener and crosslinking agent to the formation water according to the mass percentage, stir and mix evenly, add a regulator to adjust the pH of the mixed fluid to 8-10, stir evenly, and then mix with the fracturing support Mixing agent to form a sand mixing fluid, and the gel breaker is conically added to the sand mixing fluid during fracturing construction.

Example 4

The fracturing fluid of the present invention is made up of the composition of mass fraction record:

Thickener 4.00%,

crosslinking agent 2.00%,

Lauric acid 2.00%,

Regulator 1.00%,

The balance is formation water.

The thickener is cetyltrimethylammonium chloride or octadecyltrimethylammonium chloride.

The crosslinking agent is sodium salicylate.

The regulator is caustic soda (sodium hydroxide).

When the fracturing fluid is applied to the site, slowly add thickener and crosslinking agent to the formation water according to the mass percentage, stir and mix evenly, add a regulator to adjust the pH of the mixed fluid to 8-10, stir evenly, and then mix with the fracturing support Mixing agent to form a sand mixing fluid, and the gel breaker is conically added to the sand mixing fluid during fracturing construction.

Example 5

At present, the depth of oil and gas layers in exploration and development oil and gas fields in the Ordos Basin is generally 500-3500m, and the original formation temperature is 20-90°C.

The present invention adopts the fracturing fluid formula obtained in Example 2. Under this formula, the dosage of the gel breaker is selected as 0.50%, 1.00%, 1.50%, and 2.00%, and the viscosity of the fracturing fluid is detected at a temperature of 30°C. Obtain the viscosity change curve with time (Fig. 1).

It can be seen from Figure 1 that the greater the amount of breaker, the shorter the break time. At a temperature of 30°C, when the amount of breaker is 2.0%, the breaking time is still more than 60 minutes; the amount of regulator is about 0.03%, and the amount of breaker should be controlled at about 1.25%.

Example 6

At present, the depth of oil and gas layers in exploration and development oil and gas fields in the Ordos Basin is generally 500-3500m, and the original formation temperature is 20-90°C.

The present invention adopts the fracturing fluid formulation obtained in Example 3. Under this formulation, the fracturing fluid with the addition of gel breaker of 0.50%, 0.80%, 1.00%, and 1.20% is selected to detect the fracturing fluid at a temperature of 35°C. Viscosity can be obtained viscosity versus time curve (Figure 2).

It can be seen from Figure 2 that the greater the amount of breaker, the shorter the break time. At a temperature of 35°C, the dosage of regulator is about 0.025%, and the dosage of breaker should be controlled at about 1.10%.

Example 7

The lauric acid in Example 2 of the present application was replaced with ammonium persulfate and sulfonate, respectively, as the gel breaker for cleaning the fracturing fluid. In the laboratory, 25, 30, 35, and 40°C were selected as the experimental temperature, and the subsequent process was as follows: As described in Example 2, the gel breaking properties of ammonium persulfate and sulfonate at different concentrations can be obtained through experiments, as shown in Figure 3 and Figure 4 .

It can be seen from Figure 3 and Figure 4 that ammonium persulfate and sulfonate are used as gel breakers, and their gel breaking effect is rapid, and the viscosity of clean fracturing fluid can be reduced to a fixed value within 30 minutes. It will lead to sand blockage or the inability to effectively complete the sand-carrying task.

Example 8

Generally, the incompatibility of the fracturing fluid with the formation fluid after the gel breaking and the certain residue after the gel breaking will cause some damage to the oilfield reservoir. The gel breaking agent used in this application has good compatibility with the formation water after the gel breaking. Formation water was mixed according to the volume ratio of 1:2, 1:1, and 2:1. After standing for 24 hours, no precipitation or stratification was found. The results of the residue content measurement also showed that there was no residue. It can be seen that this application has broken the gel The agent has good compatibility.

The above content is a further detailed description of the present invention in combination with specific embodiments, and it cannot be assumed that the specific implementation of the present invention is limited to these descriptions. For those of ordinary skill in the technical field of the present invention, without departing from the concept of the present invention, some simple deduction or replacement can be made, which should be regarded as belonging to the protection scope of the present invention.

Claims (7)

1. a clean fracturing fluid gel breaker, it is characterised in that: relative to the gross mass of fracturing fluid, it is 0.03～2.00% that gel breaker adds quality, and described gel breaker is lauric acid.

2. the clean fracturing fluid containing gel breaker described in claim 1, it is characterised in that: it is grouped into by the one-tenth remembered with mass fraction:

Thickening agent 0.80～4.00%,

Cross-linking agent 0.50～2.00%,

Gel breaker 0.03～2.00%,

Regulator 0.02～1.00%,

Surplus is dosing water.

Clean fracturing fluid the most according to claim 2, it is characterised in that: described thickening agent is hexadecyltrimethylammonium chloride or octadecyl trimethyl ammonium chloride.

Clean fracturing fluid the most according to claim 2, it is characterised in that: described cross-linking agent is sodium salicylate.

Clean fracturing fluid the most according to claim 2, it is characterised in that: described regulator is sheet alkali.

6. clean fracturing fluid gel breaker application in hypotonic-ultra-low penetration oil-gas reservoir described in a claim 1, it is characterised in that: as the well fracturing that formation temperature is 20～90 DEG C.

7. the application in hypotonic-ultra-low penetration oil-gas reservoir of the clean fracturing fluid described in a claim 2, it is characterised in that: as the well fracturing that formation temperature is 20～90 DEG C.