CN113845892B

CN113845892B - Method for long-acting reservoir protection and reservoir permeability improvement

Info

Publication number: CN113845892B
Application number: CN202111210275.4A
Authority: CN
Inventors: 周利华; 武元鹏; 何杨; 苟绍华; 王犁; 李振宇; 向东; 赵春霞; 李辉; 王斌
Original assignee: Southwest Petroleum University
Current assignee: Southwest Petroleum University
Priority date: 2021-10-18
Filing date: 2021-10-18
Publication date: 2022-04-26
Anticipated expiration: 2041-10-18
Also published as: CN113845892A

Abstract

The invention discloses a method for long-acting reservoir protection and reservoir permeability improvement. Polyether diol and halogenating agent are first used to prepare dihalogenated polyether, then alkyl halide and imidazole are used to prepare long-chain alkyl imidazole, and finally the dihalogenated polyether and the long-chain alkyl imidazole are used to perform quaternization reaction to prepare novel polyether bridged alkyl imidazolium salt. The polyether bridged alkyl imidazolium salt prepared by the method can be used as an additive for long-acting reservoir protection and reservoir permeability improvement.

Description

Method for long-acting reservoir protection and reservoir permeability improvement

Technical Field

The invention relates to the technical field of reservoir protection and recovery enhancement of oil fields, in particular to a method for long-acting reservoir protection and reservoir permeability enhancement.

Background

Water sensitivity of hydrocarbon reservoirs has always been a major concern due to swelling and migration of clay minerals. With the development of the knowledge of oil and gas reservoirs, experts have developed a number of clay stabilizers. Himes et al indicate that clay stabilizers should contain appropriate cationic charge, appropriate molecular weight and not alter reservoir wettingThe characteristic of sex. Currently, the most commonly used clay stabilizers are inorganic and organic chloride salts, including KCl, NH₄Cl, tetramethylammonium chloride (TMAC), and choline chloride, which are inexpensive and abundant, effective in most hydrocarbon reservoirs, and have been in use for many years. However, these clay stabilizers have high water solubility and relatively small cations, meaning that they have high fluidity and are easily washed away quickly and fail during a back-flow or back-wash of the working fluid.

In recent years, cationic polymers (COP), which have a plurality of cationic centers capable of reacting with clay minerals, are increasingly used as long-lasting clay stabilizers in the oil and gas industry; but for low or ultra-low permeability formations, there is a risk of plugging the pores and thus limited use. In addition, Patel studies have shown that commonly used long-lasting clay stabilizers, such as COP, oligocationic, polymeric quaternary ammonium salts, and mono-cationic ammonium, all present environmental concerns. The polyether amine clay stabilizer is a polyamine compound (nonionic type) with polyethylene glycol (PEG) or polypropylene glycol (PPG) as the middle part, shows excellent anti-swelling effect through the synergistic action of hydrogen bond and electrostatic attraction, and is environment-friendly; however, most polyetheramines react readily at high temperatures and high pH to produce odorous ammonia gas, limiting their use. An ionic liquid is a compound having excellent thermal stability and having high clay-stabilizing performance, and thus is considered by many experts as a clay stabilizer having potential; however, only a small number of species of the 3-alkyl-1-methylimidazolium salt class have been reported for stabilizing clay minerals. In addition, in the existing several types of ionic liquids, although a waterproof layer can be formed on the clay mineral due to the introduction of the alkyl chain, and the water washing resistance of the clay stabilizer is properly improved, each clay stabilizer molecule only has one cationic positive charge center, so that the clay stabilizer is still easily washed away by high-speed fluid in the processes of water injection, acidification, fracturing and the like, and the long-term stability is lost. Therefore, by combining the characteristics of COP (multiple adsorption sites, water washing resistance), polyether amine (synergy of hydrogen bond and electrostatic interaction) and ionic liquid (good high-temperature stability), it is possible to obtain a clay stabilizer with good performance.

Furthermore, the main functional efficacy of clay stabilizers that have been applied or are still being studied in the field of reservoir protection is to reduce swelling and enhance the washout resistance of clay minerals, while no research has focused on the combination of protecting the reservoir and modifying the reservoir (i.e., only on how to reduce reservoir damage, but no reports of enhancing the permeability of the reservoir). Therefore, a dose of the multi-effect product which can reduce the damage of the reservoir and improve the permeability of the reservoir simultaneously has wide application space.

Disclosure of Invention

The invention aims to provide a method for long-term reservoir protection and reservoir permeability improvement, and provides the following technical scheme for achieving the aim.

The invention provides polyether bridged alkyl imidazolium salts and a preparation method thereof; the compound can be used as a clay mineral stabilizing additive, solves the problems of poor anti-swelling effect and poor scouring resistance effect of the existing clay stabilizer, and achieves the effect of long-acting reservoir protection; meanwhile, the compound can also be used as an additive for increasing the permeability of a reservoir, so that the oil-water relative permeability ratio and the gas-water relative permeability ratio are improved, and the oil-gas recovery ratio is further improved; the compound has the advantage of one dose with multiple effects.

The structural general formula of the polyether bridged alkyl imidazolium salt provided by the invention is shown as the formula (1):

in the formula (1), n is an integer of 0-17, m is a positive integer of 1-99, X is one of Cl and Br, R is H, CH₃R' is H, CH₃One kind of (1).

The preparation of the polyether bridged alkyl imidazolium salt provided by the invention comprises the following steps:

s1, halogenating hydroxyl groups at two ends of polyether glycol by adopting a halogenating reagent to prepare dihalogenated polyether, wherein the synthetic route is shown as a formula (2):

in the formula (2), the polyether glycol is one of hydroxyl-terminated polyethylene glycol, polypropylene glycol and poly (ethylene glycol-propylene glycol) copolymer, the polymerization degree is 2-100, and the halogenating reagent comprises one of chlorine, liquid bromine, thionyl chloride, N-bromosuccinimide, N-chloroisopropylamine, N-chlorosuccinimide, phosphorus trichloride and phosphorus pentachloride;

s2, preparing alkyl imidazole by using halogenated alkane and imidazole as raw materials, wherein the synthetic route is shown as formula (3):

in the formula (3), n is an integer of 0-17, and X is one of Cl, Br and I;

s3, carrying out quaternization on the alkyl imidazole by adopting the dihalogenated polyether, and purifying to prepare the polyether bridged alkyl imidazolium salt, wherein the synthetic route is shown as a formula (4):

in the formula (4), n is an integer of 0-17, m is a positive integer of 1-99, and X is one of Cl and Br.

The quaternization reaction in the step S3 is carried out at 100-120 ℃, and the purification method in the step S3 is that the solvent is removed through reduced pressure distillation, and then methyl tert-butyl ether and ethyl acetate are sequentially used for washing.

The polyether bridged alkyl imidazolium salt provided by the invention can be used as a stable clay mineral additive (namely a clay stabilizer, a shale inhibitor and an anti-swelling agent) and used for petroleum yield increasing processes such as acidification, fracturing, acid fracturing, water injection and the like. When the polyether bridged alkyl imidazolium salt is used as a clay stabilizer, the anti-swelling effect is better than that of a clay stabilizer commonly used in oil fields; the oil field is alwaysThe clay stabilizer is KCl or NH₄Cl, tetramethylammonium chloride, choline chloride and the like.

The polyether bridged alkyl imidazolium salt provided by the invention is used as a long-acting reservoir protection additive for petroleum yield increasing processes such as acidification, fracturing, acid fracturing and water injection. Through the synergy of the hydrophobic effect of the tail chain, the electrostatic attraction effect of the imidazolium salt and the clay mineral and the hydrogen bond effect of the bridging group and the clay surface, the polyether bridged alkyl imidazolium salt is difficult to wash away from the clay mineral surface by the subsequent construction fluid, and the excellent water washing resistance and long-acting performance are shown.

Meanwhile, the polyether bridged alkyl imidazolium salt provided by the invention is used as an additive for improving the permeability of a reservoir and is used for petroleum yield increasing processes such as acidification, fracturing, acid fracturing, water injection and the like. (1) After the polyether-bridged alkyl imidazolium salt is adsorbed on the rock croup surface, the hydration capacity of the rock croup surface can be weakened, the thickness of a hydration film is reduced, and the effective gap radius of the rock core to water, oil and gas is increased; the permeability of rock for water, oil and gas is increased, and the effective permeability is improved. (2) When the polyether bridged alkyl imidazolium salt is adsorbed on the surface of a rock pore roar, the hydrophobic tail is towards the outside, so that the hydrophilicity of the rock pore roar is weakened, but the effective air gap radius of the rock to gas is increased, which is shown in the fact that the gas permeability of the rock core is enhanced more obviously than the water permeability, namely the gas-water permeability ratio of the rock core is increased. (3) After the polyether bridged alkyl imidazolium salt is adsorbed on the surface of the rock croup, the hydrophobic tail chain faces the outside, so that the hydrophilicity of the rock croup is weakened, the lipophilicity is increased, and the oil permeability of the rock core is obviously enhanced compared with the water permeability, namely the oil-water permeability ratio of the rock core is increased.

The polyether bridged alkyl imidazolium salt provided by the invention can improve the gas-water permeability ratio and the oil-water permeability ratio of rock, properly reduce the return displacement of the fracturing fluid after volume fracturing, provide energy for a stratum, increase the yield of petroleum and natural gas and improve the oil-gas recovery ratio.

For conventional hydraulic fracturing systems, such as slickwater fracturing fluids, it is desirable to add water-soluble linear polymers containing anions to improve sand-carrying capacity. When the polyether bridged alkyl imidazolium salt provided by the invention is added, a reversible three-dimensional network can be formed among linear polymer molecules, the sand carrying capacity of the fracturing fluid is improved, and the high requirement of fracturing on the discharge capacity of pump equipment is reduced.

Compared with the prior art, the polyether bridged alkyl imidazolium salt provided by the invention has the following benefits as an additive for modifying an oil and gas reservoir:

(1) the polyether bridged alkyl imidazolium salt provided by the invention has the advantages of reliable method principle, simple and convenient operation, higher yield and environmental protection; (2) the polyether bridged alkyl imidazolium salt provided by the invention has an efficient effect of stabilizing clay minerals; (3) the polyether bridged alkyl imidazolium salt provided by the invention has a long-acting clay mineral stabilizing effect; (4) the polyether bridged alkyl imidazolium salt provided by the invention can improve the effective pore radius of a stratum and enhance the fluid seepage capability; (5) the polyether bridged alkyl imidazolium salt provided by the invention can enhance the sand carrying capacity of a fracturing fluid containing an anionic polymer.

Additional advantages, objects, and features of the invention will be set forth in part in the description which follows and in part will become apparent to those having ordinary skill in the art upon examination of the following or may be learned from practice of the invention.

Drawings

FIG. 1 is a general structural diagram of a polyether bridged alkyl imidazolium salt;

FIG. 2 is a reaction scheme of the compound PO4-DImC 12;

FIG. 3 is an IR spectrum of compound PO4-DImC 12;

FIG. 4 is a graph of the amount of adsorption of compound PO4-DImC12 on sandstone;

figure 5 is a graph of sandstone wettability after treatment with compound PO4-DImC 12;

FIG. 6 is a graph of the displacement pressure of the core before and after treatment with compound PO4-DImC 12.

Detailed Description

The principles and features of this invention are described below in conjunction with the following drawings, which are set forth by way of illustration only and are not intended to limit the scope of the invention. The examples, in which specific conditions are not specified, were conducted under conventional conditions or conditions recommended by the manufacturer. The reagents or instruments used are not indicated by the manufacturer, and are all conventional products available commercially.

EXAMPLE 1 preparation of a polyether bridged alkylimidazolium salt

The polyether bridged alkylimidazolium salts of the present invention have the structure shown in FIG. 1. In FIG. 1, n is an integer of 0-17, m is a positive integer of 1-99, X is one of Cl and Br, R is H, CH₃R' is H, CH₃One kind of (1).

In this embodiment, n is 11, m is 3, X is Cl, and R is CH₃R' is CH₃The corresponding compound is exemplified by PO4-DImC12, the chemical structure of which is shown in formula (5), and the synthesis method and the characterization thereof are described in detail.

The reaction scheme of the compound PO4-DImC12 of this example is shown in FIG. 2, and the specific preparation method is as follows.

Preparation of PO4-Cl

The preparation method of PO4-Cl of the present example comprises the following steps:

(1) weighing a certain amount of PO4-OH (polypropylene glycol terminated by hydroxyl and having a polymerization degree of 4) and pyridine, dissolving in toluene, wherein the molar ratio of PO4-OH to pyridine is 1: 1.0-1.5, and the volume of the toluene is 2.0-3.0 times of the volume sum of PO4-OH and pyridine.

(2) Keeping the mixture in the three-neck flask at the constant temperature of 50-80 ℃ for 10 min.

(3) At 50-80 ℃, the SOCl diluted by toluene₂Slowly adding dropwise into a three-neck flask, wherein PO4-OH and SOCl are added₂The molar ratio is 1: 1.0-1.5, and the volume of the toluene is SOCl₂The volume is 1.0-2.0 times, and the dropping speed is controlled to be 10-15 seconds per drop.

(4) And after the dropwise addition is finished, continuously reacting for 16-24 hours.

(5) After the reaction, the reaction mixture was cooled to room temperature, and a 1.0mol/L hydrochloric acid solution was added to the reaction mixture to adjust the reaction mixture to neutral or weakly acidic.

(6) And after the pH value is adjusted, separating liquid, taking the upper layer organic solution, and removing the toluene removing solvent by rotary evaporation to obtain transparent oily liquid, namely PO 4-Cl.

Preparation of C12Im

The preparation method of C12Im of this example includes the following steps:

(1) imidazole was weighed and dissolved in a round bottom flask with the ultra dry solvent Tetrahydrofuran (THF) at a ratio of imidazole mass (g) to THF volume (mL) of 1.0: 2.0 to 5.0.

(2) Weighing bromododecane, slowly dropwise adding the bromododecane into the flask, and uniformly mixing, wherein the molar weight ratio of imidazole to bromododecane is 1.0: 0.8 to 1.2.

(3) And (3) stirring and reacting for 24 hours under the reflux condition to obtain a reaction crude product.

(4) And (3) after removing the solvent from the crude product by rotary evaporation, repeatedly washing with water to remove excessive imidazole, removing disubstituted imidazole by using methyl tert-butyl ether, and finally removing the solvent by rotary evaporation to obtain pure colorless liquid C12 Im.

Preparation of PO4-DImC12

The preparation method of PO4-DImC12 of the embodiment comprises the following steps:

(1) weighing a certain amount of C12Im into a three-neck flask, and dissolving the mixture with toluene, wherein the volume ratio of the C12Im to the toluene is 1: 1-2.

(2) Keeping the three-mouth bottle at the constant temperature of 100-120 ℃ for 10 min.

(3) Diluting a certain amount of PO4-Cl with toluene at 100-120 ℃, and slowly dripping the diluted solution into a three-necked bottle, wherein the volume ratio of PO4-Cl to toluene is 1.0: 1.0 to 1.5.

(4) After the completion of the dropwise addition, the reaction was continued under reflux for 48 hours.

(5) Adding methyl tert-butyl ether for washing, wherein the volume ratio of the methyl tert-butyl ether to the toluene is 0.8-1.5: 1.0, repeat the operation 3 times.

(6) Adding ethyl acetate, and washing at 50 ℃, wherein the volume ratio of ethyl acetate to toluene is 0.8-1.5: 1.0, the residual content of alkylimidazole is determined by thin-layer chromatography (methanol as developing solvent).

(7) Drying in a vacuum oven at 50 ℃ for 24h to obtain yellow liquid PO4-DImC 12.

Example 2 structural characterization of a polyether bridged alkylimidazolium salt

IR characterization of the polypropylene glycol bridged alkylimidazolium salt representative PO4-DImC12 prepared in example 1 was performed.

IR characterization of PO4-DImC12

The PO4-DImC12 prepared in the above examples was IR characterized. The sample prepared in example 1 was selected and characterized by the KBr pellet method using the WQF-510A Fourier transform infrared spectrometer with the IR spectrum as shown in FIG. 3 for the structure of PO4-DImC 12.

As can be seen in FIG. 3, 3539cm^-1Indicating that the sample absorbs a certain amount of moisture in the air in the sample preparation process, 3132cm^-1And 3062cm^-12924cm for C-H stretching vibration on imidazole ring^-1And 2856cm^-1is-CH₂-and-CH₃C-H stretching vibration of 1639 and 1562cm^-11458cm for telescopic vibration of imidazole ring^-1And 1356cm^-1is-CH₂and-CH₃C-H bending vibration of 1161cm^-1Is C-N telescopic vibration of imidazole ring, 1118cm^-1C-O in the middle polyether is subjected to stretching vibration. Based on this, it can be concluded that PO4-DImC12 is consistent with the target design chemistry.

Example 3 anti-swelling Properties test of a polyether-bridged alkyl imidazolium salt

The PO4-DImC12 prepared in example 1 above was tested for anti-swelling properties. The sample prepared in the embodiment 1 is selected, and the anti-swelling performance of the sample is evaluated by referring to the petroleum industry standard SYT 5971-2016 oil and gas field fracturing acidification and water injection clay stabilizer performance evaluation method, and the specific operation is as follows:

(1) respectively preparing 0.45mol/L KCl solution and 0.45mol/L NH₄Cl solution and 0.10mol/L PO4-DImC12 solution were used as the clay stabilizer solution.

(2) 0.50g of sodium bentonite is weighed,accurately to 0.01g, placing into 10mL centrifuge tube, adding 10mL clay stabilizer solution, shaking thoroughly, standing at room temperature for 2h, placing into centrifuge, centrifuging at rotation speed of 1500r/min for 15min, reading volume V of swelled sodium bentonite₁. Note: considering that the upper end surface of the sodium bentonite in the centrifugal pipe is inclined after centrifugation, the average value of the maximum value and the minimum value of the inclined surface is taken as the volume V of the sodium bentonite after expansion₁。

(3) Weighing 0.50g of sodium bentonite, accurately weighing to 0.01g, placing into a 10mL centrifuge tube, adding 10mL deionized water, shaking thoroughly, standing at room temperature for 2h, placing into a centrifuge, centrifuging at a rotation speed of 1500r/min for 15min, reading out the volume V of the swelled sodium bentonite₂. Note: considering that the upper end surface of the sodium bentonite in the centrifugal pipe is inclined after centrifugation, the average value of the maximum value and the minimum value of the inclined surface is taken as the volume V of the sodium bentonite after expansion₂。

(4) Weighing 0.50g of sodium bentonite, accurately weighing to 0.01g, loading into a 10mL centrifuge tube, adding 10mL kerosene deionized water, fully shaking, standing at room temperature for 2h, loading into a centrifuge, centrifuging at a rotation speed of 1500r/min for 15min, and reading out the volume V of the expanded sodium bentonite₀. Note: considering that the upper end surface of the sodium bentonite in the centrifugal pipe is inclined after centrifugation, the average value of the maximum value and the minimum value of the inclined surface is taken as the volume V of the sodium bentonite after expansion₀。

(5) The anti-swelling rate of the clay stabilizer solution was calculated according to the following formula (1):

b is the anti-swelling rate (%) of the anti-swelling agent to the bentonite;

V₀-post swelling volume (mL) of bentonite in kerosene;

V₁-is the swollen volume solution (mL) in the sample of bentonite;

V₂bentonite volume after swelling in distilled water (mL).

The swelling volume of 0.5g bentonite in deionized water was found to be 5.50mL and the swelling volume in kerosene was found to be 0.42 mL. The calculated PO4-DImC12 anti-swelling rate is shown in Table 1.

TABLE 1 Antiswelling Effect of different types of Compounds

As can be seen from Table 1, the swelling prevention rate of 91.85% can be achieved by 0.10mol/L PO4-DImC12 solution.

Example 4 Water Wash resistance test of polyether bridged alkylimidazolium salts

The PO4-DImC12 prepared in example 1 was tested for scouring resistance. Selecting the sample prepared in the embodiment 1, and performing water washing resistance evaluation on the sample by referring to a petroleum industry standard SYT 5971-2016 oil and gas field fracturing acidizing and water injection clay stabilizer performance evaluation method, wherein the specific operations are as follows:

(1) preparing a clay stabilizer solution, wherein the clay stabilizer solution comprises 0.45mol/L KCl solution and 0.45mol/L NH₄Cl solution and PO4-DImC12 solution of 0.10 mol/L.

(2) Weighing 0.50g of sodium bentonite, accurately weighing to 0.01g, loading into a 10mL centrifuge tube, adding 10mL kerosene deionized water, fully shaking, standing at room temperature for 2h, loading into a centrifuge, centrifuging at a rotation speed of 1500r/min for 15min, and reading out the volume V of the expanded sodium bentonite₀. Note: considering that the upper end surface of the sodium bentonite in the centrifugal pipe is inclined after centrifugation, the average value of the maximum value and the minimum value of the inclined surface is taken as the volume V of the sodium bentonite after expansion₀。

(3) Weighing 0.50g of sodium bentonite, accurately weighing to 0.01g, loading into a 10mL centrifuge tube, adding 10mL of clay stabilizer solution, shaking thoroughly, standing at room temperature for 2h, loading into a centrifuge, centrifuging at 1500r/min for 15min, pouring out the upper water layer, and reading out the volume V of the expanded sodium bentonite₁. Note: considering that the upper end surface of the sodium bentonite in the centrifugal pipe is inclined after centrifugation, taking the maximum value and the minimum value of the inclined surfaceThe average value of (A) is taken as the volume V of the sodium bentonite after expansion₁。

(4) Weighing 0.50g of sodium bentonite, accurately weighing to 0.01g, placing into a 10mL centrifuge tube, adding 10mL deionized water, shaking thoroughly, standing at room temperature for 2h, placing into a centrifuge, centrifuging at a rotation speed of 1500r/min for 15min, reading out the volume V of the swelled sodium bentonite₂. Note: considering that the upper end surface of the sodium bentonite in the centrifugal pipe is inclined after centrifugation, the average value of the maximum value and the minimum value of the inclined surface is taken as the volume V of the sodium bentonite after expansion₂。

(5) Adding 10mL of deionized water into the centrifugal tube obtained in the step (3), fully shaking up, standing at room temperature for 2h, placing into a centrifugal machine, centrifugally separating at the rotating speed of 1500r/min for 15min, pouring out the upper water layer, and reading out the volume V of the expanded sodium bentonite₃. Note: considering that the upper end surface of the sodium bentonite in the centrifugal pipe is inclined after centrifugation, the average value of the maximum value and the minimum value of the inclined surface is taken as the volume V of the sodium bentonite after expansion₃。

(6) Repeating the step (5)4 times, and respectively recording the volume V of the sodium bentonite after expansion₄、V₅、V₆、V₇。

(7) The anti-swelling rate after washing was calculated according to the following formula (2):

in the formula B_nAfter the nth washing, the anti-swelling rate (%) of the anti-swelling agent to the bentonite is determined;

V₀-post swelling volume (mL) of bentonite in kerosene;

V₂-swelling of bentonite in distilled water to a post-swelling volume (mL);

V_n+2-after the nth water wash, the bentonite expands to volume (mL) in distilled water.

The swelling volume of 0.5g bentonite in deionized water was found to be 5.50mL and the swelling volume in kerosene was found to be 0.42 mL. The calculated water-fast washing effect of PO4-DImC12 is shown in Table 2.

As can be seen from Table 2, 0.45mol/L KCl solution and 0.45mol/L NH₄The Cl solution has poor water washing resistance, the anti-swelling rate is only about 60% after 5 times of water washing, while the PO4-DImC12 solution with the concentration of 0.10mol/L has strong water washing resistance, and the anti-swelling rate is still maintained to be more than 90.0% after 5 times of water washing.

TABLE 2 anti-swelling Effect of different types of Compounds

Example 5 adsorption Performance test of polyether-bridged alkylimidazolium salts in sandstone

The polyether bridged alkyl imidazolium salt represented by PO4-DImC12 prepared in example 1 was selected and the adsorption capacity on sandstone was examined, and the specific operation was as follows:

(1) grinding sandstone to obtain rock powder with particle size less than 200 meshes with a mortar, drying at 105 deg.C for 12h, and recording X-ray diffraction spectrum of rock powder sample with X-ray diffractometer (DX-2700, manufactured by Dandonghao Yuan instruments, Ltd.) to determine that the core contains MMT. The X-ray diffractometer adopts CuK alpha radiation (lambda is 0.15406nm), tube voltage is 40KV, stepping angle is 0.01 degrees, sampling time is 0.04s, and scanning range is 5-80 degrees.

(2) Standard saline (the formula is NaCl: CaCl) is prepared by referring to a standard SY/T5153-2017 oil reservoir rock wettability determination method₂：MgCl₂·6H₂O: water 7: 0.6: 0.4: 92).

(3) The standard saline water is used for preparing treatment solutions with different concentrations of clay stabilizers.

(4) Cutting sandstone into cores with diameter of 2.54cm and length of 5.0cm, and measuring gas permeability and porosity of core with porosity measuring instrument (HKPP-3, Haian county oil research instruments, Ltd.) by using N₂For the test media, the core porosity was determined (about 15% difference between cores) at a confining pressure of 2.0 MPa.

(5) The core was cut into pieces with a thickness of about 5mm, dried at 60 ℃ for 24h, and the dry weight of the pieces was accurately measured.

(6) The rock slices were mixed with 10PV (Pore Volume) treatment fluid, evacuated, and saturated under pressure for 24 h.

(7) And taking out the saturated rock slices, drying at 60 ℃ for 24h, accurately weighing the dry weight of the rock slices, and calculating the mass increment of the rock slice adsorption of unit mass.

The results of the above experiment are shown in FIG. 4. As can be seen from fig. 4, the sandstone adsorption amount tends to increase rapidly and then slowly with the increase of the PO4DImC12 concentration, and it is assumed that sandstone is in an adsorption saturation state at a high PO4DImC12 concentration. At an initial concentration of 40mmol/L, the sandstone had a mass gain of 12.76mg/(g sandstone) more than the standard brine group by 5.86mg/(g sandstone), indicating that the sandstone had a saturation adsorption of 6.90mg/(g sandstone).

Example 6 determination of the Effect of polyether bridged alkylimidazolium salts on sandstone wettability

The polyether bridged alkylimidazolium salt representative PO4-DImC12 prepared in example 1 was selected and its effect on sandstone wettability was examined. Selecting a sandstone core containing a certain MMT, preparing PO4-DImC12 solutions with different concentrations by using standard brine, vacuumizing, pressurizing and saturating to process sandstone slices, and inspecting the change of wettability of the slices, wherein the specific operation is as follows:

(2) Standard saline (the formula is NaCl: CaCl) is prepared by referring to a standard SY/T5153-2017 oil reservoir rock wettability determination method₂：MgCl₂·6H₂O: water 7: 0.6: 0.4: 92) (ii) a The standard saline water is used for preparing treatment solutions with different concentrations of clay stabilizers.

(3) Cutting sandstone into cores with diameter of 2.54cm and length of 5cm, and measuring gas permeability porosity of core with HKPP-3 modelLimited company) with N₂For the test media, the core porosity was determined (about 15% difference between cores) at a confining pressure of 2.0 MPa.

(4) Cutting the rock core into rock slices with the thickness of about 5mm, and drying at 60 ℃ for 24 h; mixing the rock slices with 10PV treatment fluid, vacuumizing, pressurizing and saturating for 24 hours; the saturated rock slices were taken out and dried at 60 ℃ for 24 h.

(5) And (3) loading the dried rock slices into a measuring chamber, adding kerosene to immerse the rock slices, vacuumizing to-0.1 MPa, and maintaining for 5min to ensure that the kerosene fully wets the surfaces of the rock slices.

(6) An interface parameter integrated measurement system (Kruss DSA30 type, KRUSS company in Germany) is adopted to record the change of 0.35uL standard brine on a sandstone slice (immersed in kerosene), and a corresponding contact angle of 3s after liquid drops are dripped is selected and defined as the wetting angle of the rock slice.

The results of the above experiment are shown in FIG. 5. As can be seen in fig. 5, the initial water contact angle of the core was 48.21 °, indicating that standard brine had better wettability for experimental sandstone than kerosene. With the increase of the concentration of PO4-DImC12, the standard water contact angle of the sandstone is rapidly increased, and when the initial concentration of PO4-DImC12 is 30mmol/L, the contact angle of the sandstone is 73.32 degrees; the initial PO4-DImC12 concentration is further increased, and the increase amplitude of the sandstone contact angle is smaller; at an initial PO4-DImC12 concentration of 40mmol/L, the contact angle of sandstone was 73.71 °, at which point sandstone still showed better affinity for standard brine than kerosene.

Example 7 testing of the Effect of a polyether-bridged alkylimidazolium salt on sandstone permeability

The polyether bridged alkyl imidazolium salt represented by PO4-DImC12 prepared in example 1 was selected, and the performance of compounding the polyether bridged alkyl imidazolium salt with an anionic polymer and the influence on the core permeability were evaluated.

Referring to a standard SY/T5971-2016 clay stabilizer performance evaluation method for fracturing acidification and water injection of oil and gas fields, sandstone containing certain MMT is selected and cut into cores, the cores are respectively replaced by standard saline saturation, clay stabilizer solution displacement, standard saline displacement and kerosene displacement, and the permeability of each stage is measured and used as evaluation of influence of a treatment fluid on the permeability of the cores. The specific operation is as follows:

(1) cutting sandstone into core with diameter of 2.54cm and length of 5cm, drying at 60 deg.C for 48 hr, accurately recording diameter, length and dry weight of core, measuring gas permeability and porosity of core with N₂For the test media, the core porosity (about 15%, with a small difference between cores) was measured at a confining pressure of 2.0 MPa.

(2) Preparing standard saline water, submerging the rock core in the standard saline water, vacuumizing for 30min, pressurizing at 20MPa and saturating for 48 h.

(3) The standard saline is injected positively under the confining pressure of 2.5MPa, the constant flow rate of 0.5mL/min and the temperature of 25 ℃, and the displacement pressure and the displacement equilibrium pressure at different times are recorded.

(4) Preparing treatment fluids with different viscosity stabilizer concentrations by using standard saline, reversely injecting 5PV treatment fluid under the conditions of the confining pressure of 2.5MPa, the constant flow rate of 0.5mL/min and the temperature of 25 ℃, and recording the displacement pressure and the displacement equilibrium pressure at different times. The core was removed and allowed to stand in the corresponding treatment solution for more than 6 hours.

(5) And injecting standard saline water into the container in a positive direction at 25 ℃ under the confining pressure of 2.5MPa and the constant flow rate of 0.5mL/min, and recording the displacement pressure and the displacement equilibrium pressure at different times. And measuring the porosity and the void distribution of the rock core by adopting a high-temperature high-pressure nuclear magnetic resonance rock core displacement device.

(6) The standard brine in the void was removed by forward injection of 2PV methanol with methanol at a constant flow rate of 0.5mL/min at 25 ℃ under a confining pressure of 2.5 MPa.

(7) Drying the core at 60 deg.C for 48h, submerging with kerosene, vacuumizing for 30min, pressurizing at 20MPa, and saturating for 48 h.

(8) Kerosene is injected into the mixture in the positive direction at the ambient pressure of 2.5MPa, the constant flow rate of 0.5mL/min and the temperature of 25 ℃, and the displacement pressure and the displacement equilibrium pressure at different times are recorded.

The results of the above experiment are shown in FIG. 6. The permeability at each stage was calculated by substituting the equilibrium pressure at the Phase 1 and Phase 3 stages of each treatment solution of fig. 6 into equation (3) according to Darcy's law, and the results are shown in table 3.

K-is the permeability (mD) of the displacement rock core; q-is the injection flow rate (mL/s) of the displacement fluid; l-is the length (cm) of the displacement core; a-is the cross-sectional area (cm) of the displacement core²) (ii) a Delta P-is the pressure difference (MPa) of the inlet end and the outlet end of the displacement rock core; mu-is the apparent viscosity (mPa.s) of the displacement fluid, the viscosity of kerosene is 2.210mPa.s at 25 ℃, and the viscosity of standard saline is 1.05 mPa.s.

As can be seen from table 3, the permeability of the deionized water treated cores (group a) decreased by 10.30% compared to the permeability before and after treatment with the same core treatment fluid (water permeability and water permeability after water treatment). The permeability of the core (group b) treated by the PO4-DImC12 solution is improved by 25.61%, and the PO4-DImC12 solution is presumed to have excellent expansion-proof capability, so that part of clay minerals which expand in the water permeability stage are contracted, and the void volume of the core is more favorable for liquid seepage. Meanwhile, by combining the reduction of the equilibrium displacement pressure before and after the PO4-DImC12 solution treatment (Phase I and Phase III) in fig. 6b, it is shown that the PO4-DImC12 solution has certain effects of reducing pressure and increasing injection, and the supposition is that PO4-DImC12 molecules are adsorbed on the surface of sandstone gaps, so that the thickness of a hydration film on the surface of sandstone is reduced, and the effective seepage capacity of micropores is increased. Meanwhile, PO4-DImC12 molecules are adsorbed on the surface of sandstone gaps, so that the affinity of the rock to kerosene is increased (figure 5), the ratio of the permeability of the kerosene to the permeability of standard brine is increased, and the yield of oil gas after fracturing modification is facilitated and the economic benefit is improved.

TABLE 3 impact of blanks and PO4-DImC12 on sandstone permeability

Although the present invention has been described with reference to a preferred embodiment, it should be understood that various changes, substitutions and alterations can be made herein without departing from the spirit and scope of the invention as defined by the appended claims.

Claims

1. Polyether bridged alkyl imidazolium salts are characterized by the structural general formula:

2. A process for the preparation of the polyether bridged alkyl imidazolium salts according to claim 1, characterized by the following steps:

s1, halogenating hydroxyl groups at two ends of polyether glycol by adopting a halogenating reagent to prepare dihalogenated polyether;

s2, preparing alkyl imidazole by using halogenated alkane and imidazole as raw materials;

and S3, carrying out quaternization on the alkyl imidazole by adopting the dihalogenated polyether, and purifying to obtain the polyether bridged alkyl imidazolium salt.

3. The method of claim 2, wherein the polyether glycol in step S1 is one of hydroxyl terminated polyethylene glycol, polypropylene glycol and poly (ethylene glycol-propylene glycol) copolymer, and the polymerization degree is 2-100.

4. The method of claim 2, wherein said halogenating agent in step S1 is one of chlorine, liquid bromine, thionyl chloride, N-bromosuccinimide, N-chloroisopropylamine, N-chlorosuccinimide, phosphorus trichloride, and phosphorus pentachloride.

5. The method for preparing a polyether bridged alkylimidazolium salt according to claim 2, wherein said quaternization reaction in step S3 is performed at 100-120 ℃.

6. The method for producing a polyether bridged alkyl imidazolium salt according to claim 2, wherein the step S3 is performed by distilling under reduced pressure to remove the solvent and washing with methyl t-butyl ether and ethyl acetate.

7. The polyether bridged alkylimidazolium salt according to claim 1 or prepared according to any of claims 2 to 6, as an additive for long-lasting reservoir protection and for increasing the permeability of reservoirs.