WO2024099465A1

WO2024099465A1 - Microsphere type hydrate inhibitor and use thereof

Info

Publication number: WO2024099465A1
Application number: PCT/CN2023/135894
Authority: WO
Inventors: 龙臻; 张乐欣; 梁德青; 王谨航; 何勇
Original assignee: 中国科学院广州能源研究所
Priority date: 2022-12-30
Filing date: 2023-12-01
Publication date: 2024-05-16
Also published as: CN116041706A

Abstract

Disclosed in the present invention are a microsphere type hydrate inhibitor and the use thereof. The microsphere type hydrate inhibitor comprises polymethylsilsesquioxane microspheres, which are prepared by means of the following steps: adding methyltrimethoxysilane to a hydrochloric acid aqueous solution dropwise at 20-35ºC, and stirring the mixed solution; adjusting the pH value of the mixed solution to 8-9, then stirring the mixed solution; and finally, filtering out sediment from the mixed solution, and washing and drying same, so as to obtain polymethylsilsesquioxane microspheres. The microsphere type hydrate inhibitor provided in the present invention is non-toxic, has relatively high biological safety, and can stably exist on an oil-water interface; and in a water system containing wax oil, the low-temperature rheological property of wax oil is improved, and the microsphere type hydrate inhibitor can cooperate with wax to inhibit the generation of a hydrate, and has a wider use range and conditions.

Description

A microsphere hydrate inhibitor and its application

Technical field:

The present invention relates to the technical field of oil and gas production, and in particular to a microsphere hydrate inhibitor and application thereof.

Background technique:

With the scarcity of conventional fossil resources on land, offshore oil and gas has become the main battlefield for global oil and gas resources. Compared with land and shallow sea, the low temperature, high pressure deep water environment and long-distance submarine pipeline transportation cause serious heat loss, greatly increasing the risk of solid particles (hydrates, wax, asphaltene and minerals, etc.) in the pipeline.

At present, one of the most commonly used methods to prevent hydrate formation is the injection of chemical reagents. The earliest and most mature reagents used in industry are thermodynamic inhibitors (THIs), which mainly change the thermodynamic conditions of hydrate formation and make the operating conditions away from the hydrate stability zone to achieve thorough hydrate formation inhibition. They are generally alcohols and salts, etc. The required dosage is large, up to 20-60wt% (based on the water phase), and they are highly toxic. Another type of alternative reagent, low-dose hydrate inhibitors (LDHIs), allows hydrate formation, but can ensure the safe flow of multiphase fluids in the pipeline at low doses. LDHIs are divided into kinetic inhibitors (KHIs) and inhibitors (AAs). The former inhibits hydrate nucleation or hinders crystal growth by adsorbing functional groups or interfering with hydrogen bonds of water molecules, but will fail under high supercooling conditions (△T _sub >10K). Water-soluble polymers include N-vinylamides, N-isopropyl methacrylamide, etc. The latter are generally surfactants with an amphiphilic structure. They prevent hydrate particles from aggregating in the liquid hydrocarbon phase and are continuously transported in the form of hydrate slurry. The inhibitory effect is not limited by supercooling, so they can play a better role in extreme environments such as deep-sea pipelines. However, most common AAs are traditional surfactants, typical representatives of which include commercial quaternary ammonium salts and dehydrated sorbitol spans. They have disadvantages such as high synthesis costs, difficulties in recycling, and great environmental pollution. Secondly, in waxy oil systems, wax crystals are adsorbed at the water/oil (W/O) interface through a synergistic effect with surfactant-type AAs (such as Span80 and asphalt), reducing the gas-water nucleation reaction area, increasing mass transfer resistance, and hindering hydrate nucleation and growth. But hydrates The particles are more likely to aggregate under the growth, extension and connection of wax crystals, weakening the inhibitory effect of AAs. Therefore, how to effectively prevent the formation of gas hydrates and wax deposition at the same time has become an important but difficult problem that needs to be solved in the oil and gas industry.

Adding pour point depressant (PPD) to crude oil is an effective and simple method to solve the problem of wax crystal deposition. In addition, researchers have found that PPD can also effectively improve the fluidity of wax-hydrate coexistence systems. Pour point depressants generally change the morphology and structure of wax crystals in crude oil through the action of crystal nucleation, eutectic, adsorption, etc., reduce the viscosity and freezing point of crude oil, and thus improve the low-temperature fluidity of crude oil. Existing types of pour point depressants mainly include oil-soluble high molecular polymers such as ethylene-vinyl acetate (EVA) linear copolymers, comb-like homopolymers of high-carbon methacrylate alcohol esters, maleic anhydride copolymers and nitrogen-containing polymers, most of which have long alkane main chains and polar side chains. However, a single type of pour point depressant is highly selective for crude oil and has a limited scope of application. Secondly, it has poor thermal stability, so it is urgent to develop new pour point depressant products to expand the scope of application.

Summary of the invention:

The present invention solves the problems existing in the prior art and provides a microspherical hydrate inhibitor and application thereof. The microspherical hydrate inhibitor provided by the present invention is non-toxic, has high biological safety, has amphiphilicity, and can stably exist on the oil-water interface.

The present invention aims to provide a microsphere hydrate inhibitor, comprising polymethylsilsesquioxane microspheres (PMSQ). The polymethylsilsesquioxane microspheres are prepared by the following steps: at 20°C to 35°C, methyltrimethoxysilane (MTMS) is dripped into a hydrochloric acid aqueous solution, and the mixed solution is stirred for 3 to 5 hours, wherein the volume fraction of the methyltrimethoxysilane in the hydrochloric acid aqueous solution is 2.5% to 5.0%; the pH value of the mixed solution is adjusted to 8 to 9, and the mixed solution is stirred for 4.5 to 5.5 hours; finally, the sediment in the mixed solution is filtered, and the mixed solution is washed and dried to obtain the polymethylsilsesquioxane microspheres.

Preferably, the pH value of the hydrochloric acid aqueous solution is 3.5 to 4.5. The pH value of the mixed solution is adjusted to 8 to 9 with aqueous ammonia.

PMSQ is produced by hydrolysis and condensation of methyltrimethoxysilane (MTMS), and its particle size distribution is around 0.5 to 2 μm.

The specific reaction process equation of PMSQ is shown as follows:

The present invention also protects the application of the microsphere hydrate inhibitor, which is applied to the generation and aggregation of hydrates in a wax-containing oil-water system.

Preferably, when the microspherical hydrate inhibitor is used, the mass ratio of the wax to the oil phase is 1:100 to 5:100, the applicable pressure is 1 to 25 MPa, and the temperature is -25°C to 25°C.

Preferably, the total volume ratio of water to oil and water in the wax-containing oil-water system is 0.1 to 0.5:1.

Preferably, the microspherical hydrate inhibitor in the waxy oil-water system accounts for 0.005 wt% to 0.1 wt% of the oil mass.

Preferably, the wax-containing oil-water system is prepared by the following steps:

(1) first add oil into a container, then add wax and the microspherical hydrate inhibitor into the container, and maintain the container temperature at 55° C. to 65° C. to completely dissolve the wax;

(2) After the microsphere hydrate inhibitor is evenly mixed, the temperature in the container is lowered to 40° C. to 45° C. and stored for 1 to 2 hours;

(3) Add deionized water according to the water content requirement, stir evenly, and then add cyclopentane and stir evenly to obtain a wax-containing oil-water system.

More preferably, the volume ratio of the oil to cyclopentane is 1:1 to 5:3, preferably 5:3.

The invention also protects the use of polymethylsilsesquioxane microspheres in hydrate inhibitors.

Compared with the prior art, the present invention has the following advantages: compared with the current traditional inhibitors, the microspherical hydrate inhibitor proposed by the present invention is non-toxic, has high biosafety, and can stably exist at the oil-water interface; in the wax-containing oil-water system, it improves the rheological properties of the wax oil at low temperatures, and can synergistically act with the wax to inhibit the formation of hydrates.

Description of the drawings:

FIG. 1 is a TEM image of PMSQ particles synthesized in Example 1.

FIG. 2 is an EDS graph of the PMSQ particles synthesized in Example 1.

FIG. 3 is an IR graph of PMSQ microparticles synthesized in Example 1.

FIG4 is a photograph of Example 2 after adding PMSQ to the waxy oil water.

FIG5 is a curve showing the temperature change during the formation of cyclopentane hydrate after adding 0.1 wt % PMSQ particles under the condition of mineral oil: water: cyclopentane = 5:4:3 (volume ratio).

Detailed ways:

The following examples are provided to further illustrate the present invention, but are not intended to limit the present invention.

Unless otherwise defined, all professional terms used hereinafter have the same meaning as those generally understood by those skilled in the art. The professional terms used herein are only for the purpose of describing specific embodiments and are not intended to limit the scope of protection of the present invention. Unless otherwise specified, the experimental materials and reagents herein are conventional commercial products in the art.

The testing equipment is a visual high-pressure stirring experimental device, the main components of which include a double-view mirror high-pressure reactor, a low-temperature thermostat, a temperature and pressure sensor, a data acquisition instrument, etc. The maximum working pressure of the high-pressure reactor is 30MPa, and the working temperature range is -30℃～100℃. The pressure inside the high-pressure reactor can be freely adjusted by a manual piston booster valve, and the maximum pressure of the pump is 30MPa. The low temperature constant temperature tank can provide -30℃～100℃ refrigerant circulating fluid for the jacket of the high pressure reactor. The data acquisition system collects the temperature in the reactor in real time. The formation and aggregation of hydrates can be comprehensively judged by the temperature change during the reaction and the observation situation through the transparent window.

Specific testing process:

Preparation of wax-containing water-oil system:

(1) First, add 50 mL of mineral oil into a 250 mL beaker, add a certain amount of wax (for example, the mass ratio of wax to oil phase is 5:100, i.e., the wax content is 5 wt%) into the mineral oil and keep it at 60°C to completely dissolve the wax;

(2) To avoid evaporation of cyclopentane (cyclopentane boiling point 49°C), the temperature was lowered to 40°C and kept for 1 hour;

(3) Add a certain amount of deionized water (according to the water content requirement), stir for 5 minutes, then add a certain amount of cyclopentane (the volume ratio of mineral oil to cyclopentane in the following example is 5:3), and continue stirring for 5 minutes. Finally, transfer 120 mL of wax oil water into the reactor and start the test process.

Then, the reactor was placed in a constant temperature water bath (initial water bath temperature 20°C) and stirred at a constant rate of 300 rpm. According to the phase equilibrium curve of cyclopentane hydrate, the water bath temperature was adjusted to below the equilibrium temperature (T _eq = 7.7°C) corresponding to the experimental set pressure (normal pressure 0.1 MPa) (T _o = -2.6°C).

Example 1

PMSQ microspheres (polymethylsilsesquioxane microspheres) were prepared by the following steps: 5 mL of MTMS was added dropwise into 200 mL of aqueous hydrochloric acid solution (pH = 4) at a stirring speed of 500 rpm, and the mixed solution was stirred for 4 h; secondly, the pH value of the mixed solution was adjusted to 8.5 with aqueous ammonia, and the mixed solution was stirred for another 4 h; finally, the sediment in the mixed solution was filtered, washed with ethanol, and dried at 80°C to obtain PMSQ microspheres. The final state of the PMSQ microspheres was white powder.

The obtained PMSQ microspheres were characterized by their structure, as shown in Figures 1-3. It can be seen from Figure 1 that the particle size distribution is relatively uniform. The average particle size is 0.5 μm. It can be seen from Figure 2 that the microparticles contain three elements: Si, O, and C, and the three elements are evenly distributed in the microspheres.

As can be seen from Figure 3, (1) the medium-wide peak appearing at a wave number of about 3500 cm ^- 1 is the hydroxyl vibration peak, indicating that the hydroxyl groups generated by MTMS after hydrolysis have not been completely dehydrated and polymerized, proving that the microspheres have hydrophilicity and certain thermodynamic inhibitor characteristics. The absorption peak appearing near a wave number of 1600 cm ^-1 is the HOH absorption peak formed by the absorption of water by hydroxyl groups, which is also a characteristic peak that will appear in hydrophilic _SiO2 particles, further proving the hydrophilicity of the synthesized microspheres. (2) The four small peaks appearing at wave numbers of 3000-2800 cm ^-1 are the stretching vibration absorption peaks of saturated methyl C—H, the medium-intensity peak appearing at 1274 cm ^-1 is the bending vibration absorption peak of saturated methyl C—H on the serial Si, and the two continuous small peaks appearing at 1353 cm ^-1 and 1383 cm ^-1 are the bending vibration absorption peaks of saturated methyl C—H on the methoxyl group formed by the hydrolyzed MTMS and the methanol generated by hydrolysis, which indicates the hydrophobicity of the microspheres. (3) The strong broad peak near 1110 cm ^-1 is the stretching vibration absorption peak of Si-O-Si and Si-OC, and the sharp peak at 797-769 cm ^-1 is the stretching vibration absorption peak of Si-C, which are consistent with the target product. The IR graph proves that PMSQ microspheres are amphiphilic.

Example 2 PMSQ-1

A certain concentration (0.1wt%, 0.01wt%, 0.005wt%) of PMSQ was added in step (1) during the preparation of the wax-containing water-oil system to prepare a wax (wax) + PMSQ-1 wax-containing oil-water system, which was then added to the above-mentioned high-pressure reactor to measure the induction time of hydrate formation under the condition of a water content of 33.3vol%. The experimental steps were the same as above, and the experimental results are shown in Table 1.

The specific steps of adding PMSQ in step (1) during the preparation process of the wax-containing water-oil system are as follows: (1) first add 50 mL of mineral oil into a 250 mL beaker, add wax (the mass ratio of wax to oil phase is 5:100, that is, the wax content is 5 wt%) and a certain concentration (0.1 wt%, 0.01 wt%, 0.005 wt%) of PMSQ into the mineral oil, and heat to 60°C to completely dissolve the wax.

The state after adding PMSQ to waxy oil and water is shown in Figure 4. It can be seen from Figure 4 that PMSQ microspheres are stably present in the oil. On the water interface, it is confirmed from the side that the synthesized PMSQ particles are amphiphilic. When hydrate nuclei appear, the liquid phase temperature rises sharply due to the exothermic reaction.

Example 3 PMSQ-2

0.1wt% PMSQ was added in step (3) during the preparation of the wax-containing water-oil system to prepare a 5wt% wax+PMSQ-2 wax-containing oil-water system, which was then added to the above-mentioned high-pressure reactor to measure the induction time of hydrate formation under the condition of a water content of 33.3vol%. The experimental steps were the same as above, and the experimental results are shown in Table 1.

The specific steps of adding PMSQ in step (3) during the preparation process of the wax-water-oil system are as follows: (3) adding deionized water (added at a water content of 33.3 vol%), stirring for 5 minutes, then adding cyclopentane (the volume ratio of mineral oil to cyclopentane is 5:3), continuing to stir for 5 minutes, and then adding 0.1 wt% of PMSQ. Finally, 120 mL of the wax-oil-water was transferred into the reactor to start the test process.

Comparative Example 1 (no wax)

The oil-water system without wax was added into the above autoclave to measure the induction time of hydrate formation under the condition of 33.3 vol% water content. The experimental steps were the same as above, and the experimental results are shown in Table 1.

Comparative Example 2 (containing wax)

A 5 wt% waxy oil/water system without PMSQ microspheres was added to the above autoclave to measure the induction time of hydrate formation under the condition of 33.3 vol% water content. The experimental steps were the same as above, and the experimental results are shown in Table 1.

Comparative Example 3 EVA

0.1 wt% of polyethylene-vinyl acetate (EVA) was added in step (1) (same as the adding step in Example 2) to prepare a 5 wt% wax+EVA wax-water system, which was then added to the above-mentioned autoclave to measure the induction time of hydrate formation under the condition of a water content of 33.3 vol%. The experimental steps were the same as above, and the experimental results are shown in Table 1.

Comparative Example 4 span80

0.1 wt% of span80 was added in step (1) (same as the adding step in Example 2) to prepare a 5 wt% wax+span80 wax-oil-water system, which was then added to the above-mentioned autoclave to measure the induction time of hydrate formation under the condition of a water content of 33.3 vol%. The experimental steps were the same as above, and the experimental results are shown in Table 1.

Table 1

As shown in Figure 5, when the same concentration of inhibitors are added to the same concentration of wax oil, the different order of addition leads to very different inhibition effects, indicating that only the preheated microspherical inhibitor can have a better synergistic effect with the wax to inhibit the nucleation of hydrates.

As can be seen from Table 1, it can be concluded from Examples 2-3 and Comparative Examples 1-4 that, under the same conditions, compared with the traditional pour point depressant EVA and the oil-soluble surfactant span80, the microsphere hydrate inhibitor prolongs the hydrate nucleation induction time, can effectively inhibit hydrate formation, and prevent crystal aggregation.

The above embodiments are only used to help understand the technical solution and core concept of the present invention. It is apparent to those skilled in the art that several improvements and modifications may be made to the present invention without departing from the principles of the present invention, and these improvements and modifications also fall within the protection scope of the claims of the present invention.

Claims

A microsphere hydrate inhibitor, characterized in that it comprises polymethylsilsesquioxane microspheres, wherein the polymethylsilsesquioxane microspheres are prepared by the following steps: at 20°C to 35°C, methyltrimethoxysilane is dripped into a hydrochloric acid aqueous solution, and the mixed solution is stirred for 3 to 5 hours, wherein the volume fraction of the methyltrimethoxysilane in the hydrochloric acid aqueous solution is 2.5% to 5.0%; the pH value of the mixed solution is adjusted to 8 to 9, and the mixed solution is stirred for 4.5 to 5.5 hours; finally, the sediment in the mixed solution is filtered, and the mixed solution is washed and dried to obtain the polymethylsilsesquioxane microspheres.
The microspherical hydrate inhibitor according to claim 1, characterized in that the pH value of the hydrochloric acid aqueous solution is 3.5 to 4.5.
Use of the microspherical hydrate inhibitor according to claim 1.
The use according to claim 3 is characterized in that the microspherical hydrate inhibitor is used for the formation and aggregation of hydrates in a waxy oil-water system.
The use according to claim 4 is characterized in that, when the microspherical hydrate inhibitor is used, the mass ratio of the wax to the oil phase is 1:100 to 5:100, the applicable pressure is 1 to 25 MPa, and the temperature is -25°C to 25°C.
The use according to claim 4 is characterized in that the total volume ratio of water to oil and water in the wax-containing oil-water system is 0.1 to 0.5:1.
The use according to claim 4 is characterized in that the microspherical hydrate inhibitor in the waxy oil-water system accounts for 0.005wt% to 0.1wt% of the oil mass.
The use according to claim 4 is characterized in that the wax-containing oil-water system is prepared by the following steps:

(1) first add oil into a container, then add wax and the microspherical hydrate inhibitor into the container, and maintain the container temperature at 55° C. to 65° C. to completely dissolve the wax;

(2) After the microsphere hydrate inhibitor is evenly mixed, the temperature in the container is lowered to 40° C. to 45° C. and stored for 1 to 2 hours;

(3) Add deionized water according to the water content requirement, stir evenly, and then add cyclopentane and stir evenly to obtain a wax-containing oil-water system.
The use according to claim 8 is characterized in that the volume ratio of the oil to cyclopentane is 1:1 to 5:3.
Application of polymethylsilsesquioxane microspheres in hydrate inhibitors.