CN111978939B - A polyionic liquid as a surface hydration inhibitor and a water-based drilling fluid system - Google Patents

Abstract

The invention discloses a polyion liquid used as a surface hydration inhibitor and a water-based drilling fluid system. The inhibitor used by the water-based drilling fluid is polyion liquid, and the polyion liquid comprises thiazole compounds, 4-chloromethyl styrene, azo compounds and methanol as synthetic raw materials; the drilling fluid comprises the polyionic liquid. The polyion liquid is used as a surface hydration inhibitor, has good compatibility with drilling fluid, has excellent inhibition performance, can effectively inhibit the hydration expansion of shale gas shale, obviously reduces the shale expansion rate, and prevents borehole collapse, drilling sticking and the like, thereby strengthening the borehole stability and reducing the complex conditions in the well.

Description

A polyionic liquid as a surface hydration inhibitor and a water-based drilling fluid system

technical field

The invention relates to the technical field of oil and gas field drilling, in particular to a polyionic liquid as a surface hydration inhibitor and a water-based drilling fluid containing the inhibitor.

Background technique

The exploration and development of clean energy shale gas has now become an important strategic task to ensure my country's alternative oil and gas resources. One of the key technologies for shale gas exploration and development is horizontal well drilling. The stability of mud shale in horizontal well sections and the instability of mud shale in conventional oil and gas wells have always been the most common and difficult problems in drilling engineering worldwide. Drilling fluid technology is one of the key technologies to ensure fast and safe drilling.

At present, the commonly used drilling fluid systems include water-based drilling fluid and oil-based drilling fluid. Oil-based drilling fluids are mainly used for drilling fluids in shale gas horizontal wells. Oil-based drilling fluid is a multi-phase dispersion system in which organic soil is dispersed in oil as a continuous phase. Therefore, oil-based drilling fluid has the characteristics of good shale inhibition, wellbore stability, good thermal stability, and excellent lubricity. However, the high cost, high circulation loss and environmental protection requirements of oil-based drilling fluids limit the use of oil-based drilling fluids. However, the current water-based drilling fluids still have problems in inhibiting the surface hydration of mudstone or strongly water-sensitive shale formations. The essence of shale hydration is the hydration of clay minerals in shale. The hydration of clay minerals is divided into: surface hydration and osmotic hydration. Commercial inhibitors at this stage can inhibit osmotic hydration swelling and prolong hydration time. For the inhibition of surface hydration, there is no targeted and effective method. The principle of activity balance is mainly used to inhibit the surface hydration of clay minerals. Generally, saturated cesium formate and potassium formate are used to achieve, but saturated formate solubility is very large. The use of large amounts of formate is not only expensive, but also has a serious impact on the rheology of the drilling fluid. Therefore, it is urgent to invent a new inhibitor to effectively improve the inhibitory property of water-based drilling fluids.

Ionic liquids are liquid organic salts composed of cations and anions at or near room temperature. Ionic liquids have many excellent properties, such as high thermal stability; structural designability, ionic liquids composed of different anions and cations have good solubility for inorganic salts, water, and organic substances; no volatility, etc. Due to these special properties, ionic liquids have shown incomparable advantages of traditional methods in many aspects such as organic synthesis, separation technology, electrochemistry, aerospace lubricants, and heat storage materials, and some of them have been successfully applied in industrial fields. Using polyionic liquids as surface hydration inhibitors and used in water-based drilling fluids to solve problems such as wellbore stability and reservoir pollution is the key technology of shale gas drilling at present, and it is also the development trend of shale drilling at home and abroad.

SUMMARY OF THE INVENTION

Aiming at the problem of wellbore instability caused by the deficiency of the current conventional inhibitors, the present invention provides a polyionic liquid as a surface hydration inhibitor, which can effectively prevent shale hydration and expansion, thereby achieving the purpose of stabilizing the wellbore. And developed a new water-based drilling fluid that can be used in shale formations instead of oil-based drilling fluids, which can solve problems such as wellbore stability and reservoir pollution. In order to achieve the above object, the technical scheme of the present invention is: a polyionic liquid is used as a surface hydration inhibitor and a water-based drilling fluid system, and the raw materials of the polyionic liquid inhibitor include thiazole compounds, 4-chloromethylbenzene Ethylene, azo compounds, methanol, the preparation steps of the polyionic liquid inhibitor are as follows:

Synthesis of ionic liquid: Weigh 4-chloromethylstyrene and thiazole compounds respectively and place them in the reactor and stir for 1-2 h to make them fully mixed, and then condense them under heating and stirring conditions at 60-70 °C. Reflux for 15-20h. After the reaction is completed, it is naturally cooled to 20-30° C., and the product is repeatedly washed with 10-15 mL of ethyl acetate for 3-5 times to obtain an ionic liquid.

Synthesis of polyionic liquid: Weigh ionic liquid and azo compounds in the reactor respectively, pass in inert gas nitrogen for 30-40min, add 30-40mL of methanol into the reactor and stir for 1-2h, so that the two substances are Fully contact and mix in methanol, and then react under the condition of heating at 60-70 ° C for 24-30 h, and finally obtain a polyionic liquid.

The thiazole compounds are 2-methylthiazole, 4-methylthiazole, 5-methylthiazole, 2,4-dimethylthiazole, 2,5-dimethylthiazole and 4,5-dimethylthiazole one of the

The azo compound is one of azobisisobutyronitrile and azobisisoheptanenitrile.

Another object of the present invention is to provide a water-based drilling fluid added with the polyionic liquid inhibitor of the present invention.

Based on the weight of water, the composition of the drilling fluid is as follows: clay is 3%-5%, plugging agent is 1%-5%, inhibitor is 0.5%-2%, and weighting agent is 0%-300% %, 0.5%-1% for tackifier, 1%-5% for lubricant, 1%-5% for viscosity reducer, 1%-5% for fluid loss reducer, 1%-5% for flocculant .

The clay includes one or more of bentonite, sepiolite and attapulgite; the plugging agent is one or more of asphalt, sulfonated asphalt, nano-silica and nano-barite; The surface hydration blocking agent is the polyionic liquid inhibitor; the weighting agent is barite and/or iron ore powder; the tackifier is high-viscosity polycationic cellulose, high-viscosity carboxymethyl fiber one or more of sodium salt, acrylate and acrylamide copolymer and hydroxyethyl cellulose; the lubricant is plastic pellets and/or graphite; the viscosity reducing agent used includes sulfomethyl tannin, One or more of sulfomethyl tannin extract, sulfonated styrene-maleic anhydride copolymer and vinyl acetate-maleic anhydride copolymer; Described fluid loss agent is carboxymethyl cellulose sodium salt , one or more of lignite lye, sodium nitro humate, chromium humic acid and carboxymethyl starch; the flocculant is acrylonitrile copolymer potassium salt, acrylamide and sodium acrylate copolymer and composite ionic type One or more of the high molecular weight polymers.

The beneficial effects of the present invention are as follows:

As a surface hydration inhibitor, the polyionic liquid prepared by the invention has a strong inhibitory effect on the hydration expansion and dispersion of shale gas shale, can obviously reduce the shale expansion rate, prevent well wall collapse, stuck drill, etc., and strengthen the well. Wall stability and reduce downhole complications, is an excellent inhibitor.

The water-based drilling fluid of the present invention is a water-based drilling fluid for shale gas and shale, which can effectively inhibit the hydration expansion and dispersion of shale gas shale, reduce the expansion rate of shale, and further prevent the wellbore from collapsing. stuck, and it can also enhance wellbore stability and reduce downhole complications.

Detailed ways

The technical solutions of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the protection scope of the present invention. In this embodiment, unless otherwise specified, the parts described are all parts by weight.

Example 1:

1. Synthesis of polyionic liquid inhibitors:

(1) Synthesis of ionic liquid: Weigh 1.8 g of 4-chloromethylstyrene and 1 g of 2-methylthiazole, respectively, and place them in the reactor and stir for 1.5 h to make them fully mixed, and then make them at 60° C. Under heating and stirring conditions, the mixture was condensed and refluxed for 16h. After the reaction was completed, it was naturally cooled to 22° C., and the product was repeatedly washed three times with 12 mL of ethyl acetate to obtain an ionic liquid.

(2) Synthesis of polyionic liquid: Weigh 2 g of ionic liquid and 0.08 g of azobisisobutyronitrile respectively, and place them in the reactor. After passing in inert gas nitrogen for 30 min, add 30 mL of methanol to the reactor and stir for 1.5 h, the two substances were fully contacted and mixed in methanol, and then reacted under the condition of heating at 60 °C for 24 h, and finally the polyionic liquid inhibitor 1 was obtained.

2. Configuration of water-based drilling fluid:

Measure 128g of deionized water and heat it to 70°C, add 4.0g of bentonite under low-speed electric stirring at 500r/min and stir for 10min, then add 2.0g of the polyionic liquid inhibitor prepared in Example 1 and stir for 10min, and then add 2.6g of nanometer The silica was stirred for 10 min, 3.6 g of graphite was added and stirred for 10 min, and finally 2.8 g of sulfomethyl tannin was added and stirred for 10 min to obtain water-based drilling fluid 1.

Example 2:

1. Synthesis of polyionic liquid inhibitors:

(1) Synthesis of ionic liquid: Weigh 2.0 g of 4-chloromethylstyrene and 1.3 g of 5-methylthiazole, respectively, and place them in the reactor and stir for 1.8 h to make them fully mixed, and then make them at 65° C. Under the condition of heating and stirring, it was condensed and refluxed for 18h. After the reaction, it was naturally cooled to 25° C., and the product was repeatedly washed with 14 mL of ethyl acetate for 5 times to obtain an ionic liquid.

(2) Synthesis of polyionic liquid: 2.2 g of ionic liquid and 0.1 g of azobisisoheptanenitrile were weighed and placed in the reactor, and 38 mL of methanol was added to the reactor after inert gas nitrogen was introduced for 40 min and stirred. For 1.8 h, the two substances were fully contacted and mixed in methanol, and then reacted under the condition of heating at 65° C. for 28 h, and finally the polyionic liquid inhibitor 2 was obtained.

2. Configuration of water-based drilling fluid:

Measure 100g of deionized water and heat it to 70°C, add 3.3g of sepiolite and stir for 10min under low-speed electric stirring at 500r/min, then add 2.0g of the polyionic liquid inhibitor prepared in Example 2, stir for 10min, add 2.5g The asphalt was stirred for 10 minutes, 100.0 g of iron ore powder was added and stirred for 10 minutes, and finally 0.8 g of light ethyl cellulose was added and stirred for 10 minutes to obtain water-based drilling fluid 2.

Example 3:

1. Synthesis of polyionic liquid inhibitors:

(1) Synthesis of ionic liquid: Weigh 2.2 g of 4-chloromethyl styrene and 1.4 g of 2,5-dimethylthiazole respectively, and place them in the reactor and stir for 2 h to make them fully mixed, and then make them in Condensed and refluxed for 20h under heating and stirring conditions at 70°C. After the reaction was completed, it was naturally cooled to 30° C., and the product was repeatedly washed 5 times with 15 mL of ethyl acetate to obtain an ionic liquid.

(2) Synthesis of polyionic liquid: 2.6 g of ionic liquid and 0.12 g of azobisisoheptanenitrile were weighed and placed in the reactor, and 40 mL of methanol was added to the reactor after inert gas nitrogen was introduced for 40 min and stirred. For 2 h, the two substances were fully contacted and mixed in methanol, and then reacted under the condition of heating at 70° C. for 30 h, and finally polyionic liquid inhibitor 3 was obtained.

2. Configuration of water-based drilling fluid:

Measure 120.0g of deionized water and heat it to 70°C, add 3.8g of bentonite under low-speed electric stirring at 500r/min and stir for 10min, then add 2.0g of the polyionic liquid inhibitor prepared in Example 3 and stir for 10min, add 3.0g of sulfonic acid The asphalt was mixed and stirred for 10 minutes to obtain water-based drilling fluid 3.

Example 4:

1. Synthesis of polyionic liquid inhibitors:

(1) Synthesis of ionic liquid: Weigh 1.6 g of 4-chloromethylstyrene and 1.2 g of 4,5-dimethylthiazole respectively, place them in the reactor and stir for 1.6 h, mix them well, and then make them Under the condition of heating and stirring at 66°C, the mixture was condensed and refluxed for 16h. After the reaction, it was naturally cooled to 26° C., and the product was repeatedly washed 4 times with 12 mL of ethyl acetate to obtain an ionic liquid.

(2) Synthesis of polyionic liquid: Weigh the ionic liquid and the azo compound in the reactor respectively, pass in the inert gas nitrogen for 35 min, add 35 mL of methanol to the reactor and stir for 1.6 h, so that the two substances are in methanol fully contacted and mixed in the medium, and then reacted under the condition of heating at 66 °C for 26 h, and finally obtained the polyionic liquid inhibitor 4.

2. Configuration of water-based drilling fluid:

Measure 100g of deionized water and heat it to 70°C, under low-speed electric stirring at 500r/min, add 4.6g of bentonite and stir for 10min, then add 2.0g of the polyionic liquid inhibitor prepared in Example 4 and stir for 10min, then add 4.0 g of bentonite and stir for 10min. g nano barite was stirred for 10 min, 4.0 g of graphite was added and stirred for 10 min, and finally 4.0 g of sulfomethylated gel was added and stirred for 10 min to obtain water-based drilling fluid 4.

In order to further illustrate the effect of the polyionic liquid inhibitor prepared by the present invention in the configuration of water-based drilling fluids, the shale expansion rate measurement experiments were carried out on the inhibitors synthesized in Examples 1 to 4, respectively, and the water-based drilling fluid 1 - Water-based drilling fluid 4 is tested for rheological properties.

1. Shale expansion experiment

According to the formulation of the water-based drilling fluid in the aforementioned examples 1-4, the polyionic liquid inhibitors added in the four examples were replaced respectively, and the weight of the water in each example was still used as the standard, and 0%, 0.5%, 1.0%, and 1.5% of polyionic liquid inhibitors, and shale expansion tests were performed on them respectively. The test results are shown in Table 1.

Table 1 Shale expansion rate

From the shale expansion ratios of Examples 1-4 in Table 1, it can be seen that the polyionic liquid inhibitor synthesized by the present invention has excellent effect, can significantly inhibit the hydration expansion of shale gas shale, and can significantly reduce the shale expansion ratio. In addition, when the addition amount of the polyionic liquid inhibitor is 1.0%, the inhibitory effect is the best, which can reduce the cost of drilling fluid.

2. Rheological property test of water-based drilling fluid

The rheological properties of the water-based drilling fluids configured in Example 1-Example 4 were tested, and all water-based drilling fluids were heated at a temperature of 105 ° C for 16 hours to test their rheology before and after hot rolling. parameters, and the test results are shown in Table 2.

Table 2 Performance parameters of water-based drilling fluid

It can be seen from the above table that the rheological parameters of the four polyionic liquids prepared by Example 1, Example 2, Example 3 and Example 4 as surface hydration inhibitors have little change before and after hot rolling. , indicating that the synthetic inhibitor of the present invention has little influence on the rheological properties after adding the drilling fluid. In addition, its YP/PV values are in the range of 0.36-0.48. At this time, the flow type of drilling fluid in the annulus is flat laminar flow, which is characterized by high rock-carrying ability at low viscosity. The scouring effect on the borehole wall is small, so the water-based drilling fluid has good rheology.

The above are only preferred embodiments of the present invention, and do not limit the present invention in any form. Although the present invention has been disclosed above with preferred embodiments, it is not intended to limit the present invention. Technical personnel, within the scope of the technical solution of the present invention, can make some changes or modifications to equivalent embodiments of equivalent changes by using the technical content disclosed above, but any content that does not depart from the technical solution of the present invention, according to the present invention Any simple modifications, equivalent changes and modifications made to the above embodiments still fall within the scope of the technical solutions of the present invention.

Claims (7)

1. The application of polyion liquid as a surface hydration inhibitor is characterized in that the polyion liquid inhibitor is prepared from thiazole compounds, 4-chloromethyl styrene, azo compounds and methanol by the following steps:

s1 synthesis of ionic liquid: respectively weighing 4-chloromethyl styrene and thiazole compounds, placing the 4-chloromethyl styrene and the thiazole compounds in a reactor, stirring for 1-2 hours, fully mixing the 4-chloromethyl styrene and the thiazole compounds, then condensing and refluxing the mixture for 15-20 hours under the heating and stirring condition of 60-70 ℃, naturally cooling the mixture to 20-30 ℃ after the reaction is finished, and repeatedly washing the product for 3-5 times by using 10-15mL ethyl acetate to obtain ionic liquid;

synthesis of S2 polyion liquid: respectively weighing the ionic liquid and the azo compound into a reactor, introducing inert gas nitrogen for 30-40min, adding 30-40mL of methanol into the reactor, stirring for 1-2h to ensure that 2 substances are fully contacted and mixed in the methanol, and then reacting for 24-30h under the condition of heating at 60-70 ℃ to finally obtain the polyion liquid.

2. The application of the polyion liquid as the surface hydration inhibitor according to claim 1, wherein in the step of synthesizing the S1 ionic liquid, the thiazole compound is one of 2-methylthiazole, 4-methylthiazole, 5-methylthiazole, 2, 4-dimethylthiazole, 2, 5-dimethylthiazole and 4, 5-dimethylthiazole; in the step of synthesizing the S2 polyion liquid, the azo compound is one of azobisisobutyronitrile and azobisisoheptonitrile.

3. The use of polyion liquid as surface hydration inhibitor according to claim 1, wherein in the step of synthesizing the S1 ionic liquid, the molar ratio of thiazole compound to 4-chloromethyl styrene is 1: 1 to 1.25; in the step of synthesizing the S2 polyion liquid, the addition amount of the azo compound is 2-5% of the weight of the ionic liquid.

4. A water-based drilling fluid, wherein the polyionic liquid according to any one of claims 1 to 3 is added as a surface hydration inhibitor.

5. The water-based drilling fluid of claim 4, wherein the drilling fluid comprises the following components: water, clay, blocking agent, surface hydration inhibitor, weighting agent, tackifier, lubricant, viscosity reducer, filtrate reducer and flocculant.

6. The water-based drilling fluid of claim 5, wherein the clay is added in an amount of 3-5%, the blocking agent is added in an amount of 1-5%, and the surface hydration inhibitor is added in an amount of 0.5-2% by weight of water contained in the water-based drilling fluid; the additive amount of the weighting agent is 0-300%, the additive amount of the tackifier is 0.5-1%, the additive amount of the lubricant is 1-5%, the additive amount of the viscosity reducer is 1-5%, the additive amount of the fluid loss additive is 1-5%, and the additive amount of the flocculating agent is 1-5%.

7. The water-based drilling fluid of claim 5, wherein the clay comprises one or more of bentonite, sepiolite and attapulgite; the plugging agent is one or more of asphalt, sulfonated asphalt, nano silicon dioxide and nano barite; the surface hydration blocking agent is the polyion liquid inhibitor; the weighting agent is barite and/or iron ore powder; the tackifier is one or more of high-viscosity polycation cellulose, high-viscosity sodium carboxymethyl cellulose, acrylate and acrylamide copolymer and hydroxyethyl cellulose; the lubricant is plastic pellets and/or graphite; the adopted viscosity reducer comprises one or more of sulfomethyl tannin, sulfomethyl tannin extract, sulfonated styrene-maleic anhydride copolymer and vinyl acetate-maleic anhydride copolymer; the filtrate reducer is one or more of sodium carboxymethyl cellulose, lignite alkali liquor, sodium nitrohumate, chromium humic acid and carboxymethyl starch; the flocculating agent is one or more of acrylonitrile copolymer potassium salt, acrylamide and sodium acrylate copolymer and composite ionic macromolecular weight polymer.