CN116694316A - High-mineralization-resistant water-based fracturing cross-linking fluid and preparation method thereof - Google Patents

Abstract

The invention discloses a water-based fracturing crosslinking fluid resistant to high salinity and a preparation method thereof, and relates to the field of fracturing fluids, including that the crosslinking agent is composed of the following raw materials in weight percentage: thickener 0.50- 1.50%, drainage aid 0.20-0.80%, clay stabilizer 0.10-0.50%, demulsifier 0.10-0.50%, cross-linking agent 0.20-0.80%, ion stabilizer 0.10-0.30%, and the rest is seawater; Seawater is filtered clean seawater. This method has a good preparation state, realizes self-spraying and drainage after fracturing, and achieves a good fracturing stimulation effect. The restriction that fresh water can be used for configuration on land also reduces the cost of specific applications.

Description

Water-based fracturing cross-linking fluid resistant to high salinity and preparation method thereof

technical field

The invention relates to the field of fracturing fluids, in particular to a water-based fracturing cross-linking fluid resistant to high salinity and a preparation method.

Background technique

In recent years, the exploration and development of offshore low-permeability oil and gas resources have received more and more attention. As an important stimulation measure, hydraulic fracturing technology has been widely used in low-permeability oil and gas reservoirs, and has achieved remarkable results. For the development of offshore high-temperature and low-permeability oil and gas fields, it is difficult to carry out large-scale fracturing operations due to factors such as platform space, formation temperature, operating environment, and operating costs. Fresh water is usually used to prepare fracturing fluid during onshore fracturing construction, but fresh water resources on offshore platforms are relatively scarce.

Since the salinity of seawater is usually high, seawater with high salinity has a great impact on the preparation and crosslinking of fracturing fluids. It is necessary to break through the time limit for the thickener to dissolve and viscous before combining with the continuous mixing device. liquid. If the fracturing fluid remains in the reservoir for too long, it will easily cause the clay to swell and migrate when it encounters water to block the pore throats, reduce the permeability of the reservoir matrix and fractures, and aggravate the damage.

In turn, the existing water-based fracturing cross-linking fluid needs to be configured with fresh water, which is inconvenient to configure on offshore oil platforms where fresh water is scarce. It can only be configured on land, which increases the cost. Joint liquid can easily cause clay to block pore throats, reduce the permeability of reservoir matrix and fractures, and aggravate the problem of damage. Therefore, a water-based fracturing cross-linking fluid resistant to high salinity is proposed.

Contents of the invention

The purpose of the present invention is to provide a water-based fracturing cross-linking fluid resistant to high salinity and its preparation method, which solves the problem that the existing water-based fracturing cross-linking fluid can only be configured with fresh water to increase the cost of use, and at the same time it is easy to cause clay Plugging, which reduces reservoir matrix and fracture permeability, exacerbates the damage problem.

In order to achieve the above object, the present invention provides the following technical proposal: a water-based fracturing cross-linking fluid resistant to high salinity, the cross-linking agent is composed of the following raw materials in weight percentage: thickener 0.50-1.50% , drainage aid 0.20-0.80%, clay stabilizer 0.10-0.50%, demulsifier 0.10-0.50%, crosslinking agent 0.20-0.80%, ion stabilizer 0.10-0.30%, and the rest is sea water;

The seawater is filtered clean seawater.

Preferably, the preparation method of the thickener is:

(1) Acrylamide, acrylic acid, N-vinylpyrrolidone and aminopropyltrimethylammonium chloride are weighed in a certain mass ratio and dissolved in distilled water, and stirred to fully dissolve;

(2) Then carry out heating in a water bath, and add sodium hydroxide solution to adjust the pH value to between 8-10, then feed nitrogen to remove oxygen, then add ammonium persulfate and sodium bisulfite as initiators to start the polymerization reaction;

(3) After reacting for 4 hours under the condition of maintaining nitrogen flow, continue to raise the temperature, and then continue to react for 3 hours;

(4) Finally, the product is dried and pulverized to obtain the thickener.

Preferably, the temperature of the water bath heating in (1) is 45°C, and the temperature of the heating in (3) is 65°C.

Preferably, the ratio of ammonium persulfate added in (2) to sodium bisulfite is 1:1.

A preparation method of a water-based fracturing cross-linking fluid resistant to high salinity, comprising the following steps:

Step 1: Measure a certain volume of filtered seawater in the mixer, add thickener in proportion under stirring conditions, and continue stirring for a certain period of time;

Step 2: After the stirring is completed, continue to add clay stabilizer, drainage aid, and ion stabilizer in proportion, and continue to stir to prepare seawater-based fracturing fluid base fluid.

Step 3: Then add the cross-linking agent in proportion to dissolve in the fracturing fluid base fluid, adjust and reduce the speed and continue stirring to configure the sea-based fracturing fluid.

Preferably, the stirring condition of the step 1 is 1000r/min, and the stirring time is 10min.

Preferably, the stirring condition in step 2 is 1000r/min, and the stirring time is 10min.

Preferably, the stirring condition in step 3 is 500r/min, and the stirring time is 5min.

Compared with related technologies, a water-based fracturing cross-linking fluid resistant to high salinity provided by the present invention has the following beneficial effects:

The invention provides a water-based fracturing cross-linking fluid resistant to high salinity and a preparation method. A new thickening agent is configured and used as the main treatment agent, and a set of other treatment agents such as cross-linking agents is used to construct a set. The high temperature and high salinity seawater-based fracturing fluid system makes the water-based fracturing cross-linking fluid prepared by this thickener have good temperature and shear resistance, salt resistance, suspended sand performance, filtration performance and The gel-breaking performance, and the damage of the gel-breaking fluid to the matrix permeability of the natural rock core of the reservoir is small, which can meet the needs of offshore oilfield fracturing construction. Fluid drainage has achieved good fracturing stimulation effects, and at the same time, it can also be configured with seawater, avoiding the restriction that the existing water-based fracturing cross-linking fluid can only be configured with fresh water on land, and also reduces the specific The cost of using.

Description of drawings

Fig. 1 is the rheological curve of the seawater-based fracturing fluid of the present invention.

Detailed ways

The technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only some of the embodiments of the present invention, not all of them; based on The embodiments of the present invention and all other embodiments obtained by persons of ordinary skill in the art without making creative efforts belong to the protection scope of the present invention.

Embodiment one:

The invention provides a technical solution: a water-based fracturing cross-linking fluid resistant to high salinity, the cross-linking agent is composed of the following raw materials by weight percentage: 0.50% thickener, 0.20% drainage aid, clay 0.10% stabilizer, 0.10% demulsifier, 0.20% crosslinker, 0.10% ion stabilizer, and the rest is sea water;

Seawater is filtered clean seawater.

The preparation method of thickener is:

(1) Acrylamide, acrylic acid, N-vinylpyrrolidone and aminopropyltrimethylammonium chloride are weighed in a certain mass ratio and dissolved in distilled water, and stirred to fully dissolve;

(2) Then carry out heating in a water bath, and add sodium hydroxide solution to adjust the pH value to between 8-10, then feed nitrogen to remove oxygen, then add ammonium persulfate and sodium bisulfite as initiators to start the polymerization reaction;

(3) After reacting for 4 hours under the condition of maintaining nitrogen flow, continue to raise the temperature, and then continue to react for 3 hours;

(4) Finally, the product is dried and pulverized to obtain the thickener.

(1) The temperature of the water bath heating is 45°C, and the temperature of the heating in (3) is 65°C.

(2) The ratio of ammonium persulfate and sodium bisulfite added is 1:1.

Embodiment two:

The invention provides a technical solution: a water-based fracturing cross-linking fluid resistant to high salinity, the cross-linking agent is composed of the following raw materials by weight percentage: 0.80% thickener, 0.50% drainage aid, clay 0.30% stabilizer, 0.20% demulsifier, 0.50% crosslinker, 0.20% ion stabilizer, and the rest is sea water;

Seawater is filtered clean seawater.

The preparation method of thickener is:

(1) Acrylamide, acrylic acid, N-vinylpyrrolidone and aminopropyltrimethylammonium chloride are weighed in a certain mass ratio and dissolved in distilled water, and stirred to fully dissolve;

(2) Then carry out heating in a water bath, and add sodium hydroxide solution to adjust the pH value to between 8-10, then feed nitrogen to remove oxygen, then add ammonium persulfate and sodium bisulfite as initiators to start the polymerization reaction;

(3) After reacting for 4 hours under the condition of maintaining nitrogen flow, continue to raise the temperature, and then continue to react for 3 hours;

(4) Finally, the product is dried and pulverized to obtain the thickener.

(1) The temperature of the water bath heating is 45°C, and the temperature of the heating in (3) is 65°C.

(2) The ratio of ammonium persulfate and sodium bisulfite added is 1:1.

Embodiment three:

The invention provides a technical solution: a water-based fracturing cross-linking fluid resistant to high salinity, the cross-linking agent is composed of the following raw materials by weight percentage: 1.50% thickener, 0.80% drainage aid, clay 0.50% stabilizer, 0.50% demulsifier, 0.80% crosslinker, 0.30% ion stabilizer, and the rest is sea water;

Seawater is filtered clean seawater.

The preparation method of thickener is:

(1) Acrylamide, acrylic acid, N-vinylpyrrolidone and aminopropyltrimethylammonium chloride are weighed in a certain mass ratio and dissolved in distilled water, and stirred to fully dissolve;

(2) Then carry out heating in a water bath, and add sodium hydroxide solution to adjust the pH value to between 8-10, then feed nitrogen to remove oxygen, then add ammonium persulfate and sodium bisulfite as initiators to start the polymerization reaction;

(3) After reacting for 4 hours under the condition of maintaining nitrogen flow, continue to raise the temperature, and then continue to react for 3 hours;

(4) Finally, the product is dried and pulverized to obtain the thickener.

(1) The temperature of the water bath heating is 45°C, and the temperature of the heating in (3) is 65°C.

(2) The ratio of ammonium persulfate and sodium bisulfite added is 1:1.

Embodiment four:

A preparation method of a water-based fracturing cross-linking fluid resistant to high salinity, comprising the following steps:

Step 1: Measure a certain volume of filtered seawater in the mixer, add the thickener in proportion under the stirring condition of 1000r/min, and continue stirring for 10 minutes;

Step 2: After the stirring is completed, continue to add clay stabilizer, drainage aid, and ion stabilizer in proportion, and continue to stir for 10 minutes under the stirring condition of 1000r/min to prepare seawater-based fracturing fluid base fluid.

Step 3: Then add the cross-linking agent in proportion to dissolve in the fracturing fluid base fluid, adjust the speed to 500r/min and continue stirring for 5 minutes to configure the sea-based fracturing fluid.

Comparative example one

Please refer to Figure 1, the applicant made the following experiments with the water-based fracturing cross-linking fluid prepared with the relevant raw material percentages in Example 2, to verify its related performance:

(1) Cross-linking performance: according to the temperature condition of the reservoir, the pH value is adjusted between 8 and 9, the amount of other raw materials added is kept constant according to Example 2, and the amount of cross-linking agent is controlled so that the added mass fraction is 0.20-0.80%, the cross-linking time is adjusted between 10-60s, the jelly after cross-linking is complete, tough and easy to hang.

(2) Temperature resistance and shear resistance: According to the "Water-based Fracturing Fluid Performance Evaluation Method" (SY/T5107-2005), use the HAAKEMARS rheometer to test the fracturing fluid formula under the condition of 170s-'.80℃ Temperature resistance test. Figure 1 of the specification shows the rheological curve of seawater-based fracturing fluid. It can be seen that the viscosity of this formula remains at about 140 mPa·s after shearing at 80 °C for 90 min, which can fully meet the requirements of on-site fracturing construction.

(3) Residue content: The residue content of fracturing fluid has a great influence on the effect of fracturing stimulation to increase production. The water-based fracturing fluid system configured by this method has a small residue content (the average residue content is 323mg/L), which meets the water-based fracturing fluid system. Requirements for residue content in general technical indicators of gel-based fracturing fluid.

(4) Gel fluid loss performance: the fluid loss coefficient of the fracturing fluid at room temperature is 2.7×10 ^-4 m ² /min, less than 6.0× ^{10 -4 m 2} /min, which meets the general technology of water-based gel fracturing fluid Requirements of indicators for static filtration coefficient.

(5) Gel-breaking performance: The viscosity of the gel-breaking liquid measured at 30°C is 3.58mPa·s, the surface tension of the gel-breaking liquid is 28.90mN/m after the gel is broken, and its interfacial tension with dehydrated kerosene is 1.27mN /m. After breaking the gel, the fracturing fluid has low viscosity, low surface tension and interfacial tension, which is conducive to rapid and thorough flowback after fracturing.

The core damage evaluation of seawater-based fracturing fluid is carried out, and the experimental results are shown in Table 1. The core damage rate is 18.27%, which is much lower than 30%, and belongs to the low damage system.

Table 1: Results of fracturing fluid core damage experiment

Claims (8)

1. A water-based fracturing cross-linking fluid resistant to high salinity, characterized in that the cross-linking agent consists of the following raw materials in percentage by weight: thickener 0.50-1.50%, drainage aid 0.20- 0.80%, clay stabilizer 0.10-0.50%, demulsifier 0.10-0.50%, crosslinking agent 0.20-0.80%, ion stabilizer 0.10-0.30%, and the rest is sea water; The seawater is filtered clean seawater. 2. a kind of high salinity-resistant water-based fracturing cross-linking fluid according to claim 1, is characterized in that, the preparation method of described thickening agent is: (1) Acrylamide, acrylic acid, N-vinylpyrrolidone and aminopropyltrimethylammonium chloride are weighed in a certain mass ratio and dissolved in distilled water, and stirred to fully dissolve; (2) Then carry out heating in a water bath, and add sodium hydroxide solution to adjust the pH value to between 8-10, then feed nitrogen to remove oxygen, then add ammonium persulfate and sodium bisulfite as initiators to start the polymerization reaction; (3) After reacting for 4 hours under the condition of maintaining nitrogen flow, continue to raise the temperature, and then continue to react for 3 hours; (4) Finally, the product is dried and pulverized to obtain the thickener. 3. A kind of high-salinity-resistant water-based pressure cross-linking liquid according to claim 2, characterized in that, the temperature of the water bath heating in (1) is 45° C., and the heating in the (3) The temperature was 65°C. 4. a kind of high salinity-resistant water-based fracturing cross-linking fluid according to claim 2, is characterized in that, the ratio of ammonium persulfate added in the described (2) and sodium bisulfite is 1 :1. 5. A preparation method of a water-based fracturing crosslinking fluid resistant to high salinity, preparing a kind of water-based fracturing crosslinking fluid resistant to high salinity as claimed in any one of claims 1-4, It is characterized in that, comprising the following steps: Step 1: Measure a certain volume of filtered seawater in the mixer, add thickener in proportion under stirring conditions, and continue stirring for a certain period of time; Step 2: After the stirring is completed, continue to add clay stabilizer, drainage aid, and ion stabilizer in proportion, and continue to stir to prepare seawater-based fracturing fluid base fluid. Step 3: Then add the cross-linking agent in proportion to dissolve in the fracturing fluid base fluid, adjust and reduce the speed and continue stirring to configure the sea-based fracturing fluid. 6. The method for preparing a high-salinity-resistant water-based fracturing cross-linking fluid according to claim 5, wherein the stirring condition in step 1 is 1000 r/min, and the stirring time is 10 min. 7. The method for preparing a high-salinity-resistant water-based fracturing cross-linking fluid according to claim 6, characterized in that, the stirring condition in step 2 is 1000 r/min, and the stirring time is 10 min. 8. The method for preparing a high-salinity-resistant water-based fracturing cross-linking fluid according to claim 7, characterized in that, the stirring condition in step 3 is 500 r/min, and the stirring time is 5 min.