CN113216910B - A kind of chemical heat generating agent for natural gas hydrate exploitation and its application - Google Patents

Abstract

The invention discloses a chemical heat generating agent for natural gas hydrate exploitation and application thereof, wherein the heat generating agent comprises: a main agent I, a main agent II and an auxiliary agent; the main agent I comprises the following components in percentage by mass and volume: 10 to 32% of NaNO ₂ 1-7.5% of foaming agent, 2-7.5% of foam stabilizer and the balance of water; the foaming agent is cationic Gemini quaternary ammonium salt; the foam stabilizer is nano-particles; the auxiliary agent is acid gas selected from CO ₂ And/or SO ₂ And the volume ratio of the main agent I to the auxiliary agent is 1: 4-40, mixing the main agent I and the auxiliary agent according to the volume ratio to obtain foam liquid; the main agent II is NH ₄ Aqueous Cl solution. The chemical heat generating agent system can release a large amount of heat, can regulate and control the release speed of the heat, and meets the requirement of deep energy transmission of a reservoir stratum in the exploitation of the natural gas hydrate.

Description

A kind of chemical heat generating agent for natural gas hydrate exploitation and its application

technical field

The invention relates to a chemical heat generating agent, in particular to a chemical heat generating agent for natural gas hydrate exploitation and its application.

Background technique

Natural gas hydrate is a solid compound similar to ice formed by natural gas (the main component methane) and water under certain high pressure and low temperature conditions. The natural gas hydrate production process is a strong endothermic process. During the production process, the temperature of the hydrate layer decreases rapidly, resulting in problems such as reduced gas production rate and pore blockage.

In order to solve the above problems, the current conventional solution is to use hot water injection, steam injection and other methods for heating. However, these methods have a very common problem, that is, most of the heat of the thermal fluid is consumed in the near-wellbore area. This leads to insufficient heat supply for the decomposition of hydrates in the deep reservoir, which ultimately affects the overall recovery effect of hydrates. In order to improve the heat supply in the process of hydrate extraction, it is proposed to use chemical biothermal agent to carry heat to the far end of the formation in the form of chemical energy. Improves heat supply deep in the reservoir.

The nitrite and ammonium chloride exothermic systems have been widely used in many industries. For example, the common autogenous fracturing fluid system at home and abroad is the nitrite and ammonium salt system, which can occur under acidic conditions. The chemical reaction generates a lot of heat and generates friendly and stable gases such as _N2 . However, the current autogenous systems all have difficulties in controlling the peak temperature. Studies have shown that the most important factor affecting the heat generation capacity of chemical biothermal systems is the concentration of chemical agents. The higher the concentration, the stronger the heat generation capacity of the reaction and the greater the heat generation. However, increasing the concentration of the chemical agent will lead to an increase in the heat release rate, and this rapid heat release is extremely unfavorable for the heat transfer to the deep reservoir. How to balance the two is a key issue in the application of chemical biothermal systems. In recent years, extensive research has been carried out on the temperature control of autogenous fluids at home and abroad. For example, Chinese patent CN11849451A discloses a peak-controllable autogenous fracturing fluid and its preparation method and application. It is composed of self-generated heat fracturing fluid base fluid and activator solution mixed according to the mass ratio (18-22): (0.8-1.2). At 0.04%, the time to reach the peak temperature is adjustable from 1 to 5 hours, and the peak temperature can reach 48 to 105 °C. Chinese patent CN112322270A discloses a continuous self-generating heat generation system for a little fracturing fluid and its preparation method. The patent forms an emulsifier with catalyst hydrochloric acid, cyclohexane and Span-80 emulsifier to achieve the purpose of slowing down the heat generation of the reaction. The continuous autogenous heat of the system can be maintained above 50°C within 40min. Chinese patent CN109281643A discloses a system for delaying autogenous heat. The system is composed of an aqueous ammonium chloride solution and water-in-oil sodium nitrite. By preparing a water-in-oil emulsion from sodium nitrite, the system can slow down the contact between the two. Purpose.

In addition, the ambient temperature is also an important factor affecting the heat generation rate. However, most of the current patents are aimed at fracturing systems, which are mainly used to solve the problem of cold damage to the bottom layer by fracturing fluid, and the reaction temperature is 30-50°C. However, the formation temperature of natural gas hydrate is generally below 20°C, and the temperature during the production process may even drop below zero. However, there has been no report on the invention of a method for controlling the exothermic rate of hydrate under low temperature conditions.

SUMMARY OF THE INVENTION

The purpose of the present invention is to provide a chemical heat generating agent for natural gas hydrate exploitation and its application, which solves the problem that the heat of the existing chemical heat generating agent is uncontrollable, and the chemical heat generating agent can be released under low temperature conditions. A large amount of heat can meet the heating capacity, and can also control the heat release rate, slow down the heat generation rate, and meet the requirements of deep reservoir energy transportation in natural gas hydrate exploitation.

In order to achieve the above object, the present invention provides a chemical heat generating agent for natural gas hydrate exploitation, the heat generating agent comprises: main agent I, main agent II and auxiliary agent; wherein, the main agent I is composed of the following quality Component composition by volume percentage: 10-32% NaNO ₂ , 1-7.5% foaming agent, 2-7.5% foam stabilizer, and the balance is water; the foaming agent is a cationic Gemini quaternary ammonium salt, the cationic Type Gemini quaternary ammonium salt is selected from diquaternary ammonium salt adipate; the foam stabilizer is nanoparticles; the auxiliary agent is an acid gas, and the acid gas is selected from CO ₂ and/or SO ₂ , and the main agent is The volume ratio of I and the auxiliary agent is 1:4 to 40. The main agent I and the auxiliary agent are mixed according to the volume ratio to obtain a foam liquid; the main agent II is an NH ₄ Cl aqueous solution, and the molar concentration of the NH ₄ Cl aqueous solution It is equal to the molar concentration of sodium nitrite in the foam liquid, and the volume of the aqueous NH ₄ Cl solution is equal to the volume of the foam liquid.

The chemical biothermal agent for natural gas hydrate exploitation of the present invention is a novel self-generating heat system using acid gas as a catalyst. The system uses acid gas and solution to form foam liquid, and the exothermic reaction process is as follows. _CO2 gas is used as the For example, as follows:

First, _CO2 reacts with water to form a weak acid,

Secondly, sodium nitrite and ammonium chloride undergo an exothermic reaction in the condition of an acidic catalyst,

Since the above two reactions are series reactions, the final exothermic rate is determined by the reaction equation (1) and the reaction equation (2), and the two work together to achieve the purpose of slowing down the reaction rate.

Preferably, the nanoparticles are nano-silica particles.

Another object of the present invention is to provide the application of the chemical heat generating agent in the exploitation of natural gas hydrate.

Preferably, the auxiliary agent and the main agent I are mixed at a pressure of 4-6 MPa to form a foam liquid; an equal volume of the foam liquid and the main agent II are injected into the hydrate layer at the same time to carry out the hydrate thermal recovery process .

The chemical heat generating agent for natural gas hydrate exploitation and its application of the present invention solves the problem of uncontrollable heat of the existing chemical heat generating agent, and has the following advantages:

The chemical heat generating agent for natural gas hydrate exploitation of the present invention can not only satisfy the function of releasing a large amount of heat in a low temperature environment, but also control (delay) the release rate of heat, so as to satisfy the energy transport in deep reservoirs in natural gas hydrate exploitation requirements. At the same time, when using the chemical heat generating agent provided by the present invention for hydrate mining, it only needs to be injected at room temperature without heating the solution in advance, which greatly reduces the consumption of heat.

Description of drawings

Fig. 1 is the comparison chart of the heat release rate in the process of hydrate exploitation with the chemical heat generating agent of the present invention (Example 1) and the acetic acid catalyst heat generating system.

FIG. 2 is a comparison diagram of the heat release rate in the process of hydrate extraction with the chemical heat generating agent of the present invention (Example 3) and the acetic acid catalyst heat generating system.

FIG. 3 is a comparison diagram of the heat release rate of the heat generating agent of the present invention, hot water and conventional acetic acid heat generating systems.

Detailed ways

The technical solutions in the embodiments of the present invention will be described clearly and completely below. 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.

Example 1

A chemical heat generating agent for natural gas hydrate exploitation, the main agent I of the heat generating agent comprises the following components in mass volume percentage (W/V, g/mL): 1% foaming agent, 2% foam stabilizer agent, 10% sodium nitrite, and the balance water; wherein, the foaming agent is selected from diquaternary ammonium salt adipate, and the foam stabilizer is selected from nano-silicon dioxide particles. The auxiliary agent of the heat generating agent is CO ₂ , the volume ratio of the main agent I to CO ₂ is 1:4, and the main agent I and the auxiliary agent are mixed according to the volume ratio to obtain a foam liquid. The main agent II of the heat generating agent is an NH ₄ Cl aqueous solution, and the molar concentration of the NH ₄ Cl aqueous solution is equal to the molar concentration of sodium nitrite in the foam liquid.

The preparation of main agent I is: adding part of water into reaction vessel I, heating to 60° C., then adding 100g NaNO ₂ and 10g diquaternary ammonium salt adipate surface activity to reaction vessel I successively under stirring conditions agent and 20 g of silicon dioxide particles, add the remaining water to a total volume of 1000 mL, and continue stirring at 60° C. for 1 h after the addition is completed until the components are uniformly dissolved to obtain the main agent I.

The preparation of main agent II is as follows: according to the concentration of NaNO ₂ in the foam liquid, an aqueous NH ₄ Cl solution is prepared, water is added to the reaction vessel II, heated to 60° C., and then NH ₄ Cl is added to the reaction vessel II under stirring conditions. , and after the addition was completed, stirring was continued at 60° C. for 1 h to obtain the main agent II.

The method for using the above chemical biothermal agent in the hydrate mining process comprises: under the pressure of 4-6MPa, vigorously mixing _CO2 gas with the main agent I according to a predetermined volume ratio through a mixing pump to form a foam liquid; The high-pressure pump simultaneously pumps the same volume of foam liquid and the main agent II into the hydrate layer at the same time, and the hydrate thermal recovery process can be carried out.

The mixing situation of the main agent I of the present embodiment 1 and the auxiliary agent is as follows:

Add 300 mL of main agent I to the high-pressure sapphire kettle, feed 1200 mL of _CO gas under constant stirring, the pressure is 4-6 MPa, read the foam volume after stirring for 30 min, let it stand, and then record the change with time corresponding to it volume of foam. Through research, it was found that in Example 1, the time for the bottom liquid of the foam liquid to appear 1/4 of the height was 2.5h; while the half-life of the foaming agent composed of Span 80 and Tween 80 with the same concentration The time is 0.5h, indicating that the foaming agent of the present invention has excellent foaming effect.

Example 2

A chemical heat generating agent for natural gas hydrate exploitation, the main agent I of the heat generating agent comprises the following components in mass volume percentage (W/V, g/mL): 7.5% foaming agent, 7.5% foam stabilizer agent, 32% sodium nitrite, and the balance water; wherein, the foaming agent is selected from diquaternary ammonium salt adipate, and the foam stabilizer is selected from nano-silica particles. The auxiliary agent of the heat generating agent is CO ₂ , the volume ratio of the main agent I to CO ₂ is 1:40, and the main agent I and the auxiliary agent are mixed according to the volume ratio to obtain a foam liquid. The main agent II of the heat generating agent is an NH ₄ Cl aqueous solution, and the molar concentration of the NH ₄ Cl aqueous solution is equal to the molar concentration of sodium nitrite in the foam liquid.

The preparation of main agent I is: adding part of water into reaction vessel I, heating to 60° C., then adding 320g NaNO ₂ and 75g diquaternary ammonium salt adipate surface activity to reaction vessel I successively under stirring conditions agent and 75 g of silica particles, add the remaining water to a total volume of 1000 mL, and continue stirring at 60° C. for 1 h after the addition is completed until the components are uniformly dissolved to obtain the main agent I.

The preparation of main agent II is as follows: according to the concentration of NaNO ₂ in the foam liquid, an aqueous NH ₄ Cl solution is prepared, water is added to the reaction vessel II, heated to 60° C., and then NH ₄ Cl is added to the reaction vessel II under stirring conditions. , and after the addition was completed, stirring was continued at 60° C. for 1 h to obtain the main agent II.

The method for using the above chemical biothermal agent in the hydrate mining process comprises: under the pressure of 4-6MPa, vigorously mixing _CO2 gas with the main agent I according to a predetermined volume ratio through a mixing pump to form a foam liquid; The high-pressure pump simultaneously pumps the same volume of foam liquid and the main agent II into the hydrate layer at the same time, and the hydrate thermal recovery process can be carried out.

The mixing situation of the main agent I of the present embodiment 2 and the auxiliary agent is as follows:

Add 300mL of main agent I to the high-pressure sapphire kettle, feed 12,000mL of _CO2 gas under constant stirring, the pressure is 4-6MPa, read the foam volume after stirring for 30min, let it stand, and then record the change with time corresponding to it volume of foam. Through research, it is found that the half-life time of the foam liquid using diquaternary ammonium salt adipate in Example 2 is 4h; while the half-life time of the foaming agent composed of Span 80 and Tween 80 with the same concentration is 0.8h, indicating that this The inventive foaming agent has excellent foaming effect.

Example 3

A chemical heat generating agent for natural gas hydrate exploitation, the main agent I of the heat generating agent comprises the following components in mass volume percentage (W/V, g/mL): 1% foaming agent, 2% foam stabilizer agent, 10% sodium nitrite, and the balance water; wherein, the foaming agent is selected from diquaternary ammonium salt adipate, and the foam stabilizer is selected from nano-silicon dioxide particles. The auxiliary agent of the heat generating agent is SO ₂ , the volume ratio of the main agent I to SO ₂ is 1:10, and the main agent I and the auxiliary agent are mixed according to the volume ratio to obtain a foam liquid. The main agent II of the heat generating agent is an NH ₄ Cl aqueous solution, and the molar concentration of the NH ₄ Cl aqueous solution is equal to the molar concentration of sodium nitrite in the foam liquid.

The preparation of main agent I is: adding part of water into reaction vessel I, heating to 60° C., then adding 100g NaNO ₂ and 10g diquaternary ammonium salt adipate surface activity to reaction vessel I successively under stirring conditions agent and 20 g of silicon dioxide particles, add the remaining water to a total volume of 1000 mL, and continue stirring at 60° C. for 1 h after the addition is completed until the components are uniformly dissolved to obtain the main agent I.

The preparation of main agent II is as follows: according to the concentration of NaNO ₂ in the foam liquid, an aqueous NH ₄ Cl solution is prepared, water is added to the reaction vessel II, heated to 60° C., and then NH ₄ Cl is added to the reaction vessel II under stirring conditions. , and after the addition was completed, stirring was continued at 60° C. for 1 h to obtain the main agent II.

The method for using the above chemical biothermal agent in the hydrate mining process comprises: under the pressure of _4-6MPa , vigorously mixing SO2 gas with the main agent I according to a predetermined volume ratio through a mixing pump to form a foam liquid; The high-pressure pump simultaneously pumps the same volume of foam liquid and the main agent II into the hydrate layer at the same time, and the hydrate thermal recovery process can be carried out.

Example 4

A chemical biothermal agent for natural gas hydrate exploitation is basically the same as that of Example 3, except that the volume ratio of main agent I to SO ₂ is 1:40.

The performance test is carried out to the chemical heat generating agent of embodiment 1-4, as follows:

The following hydrate mining experiments for heat release performance testing were performed using samples synthesized in situ in the laboratory. The saturation of the hydrate phase in the hydrate sample is 30%, the saturation of the gas phase is 70%, and the sediment is 70-100 mesh quartz sand.

1. Comparison of heat release rate

Using the same concentration of the chemical heat generating agent of the present invention (Example 1) and the acetic acid catalyst heat generating system to carry out a hydrate mining experiment, the heat release rates of the two are compared, and the results are shown in Figure 1. It can be seen from the figure that the peak heat release time of the chemical heat generating agent of Example 1 of the present invention is significantly later than that of the acetic acid catalyst heat generating system, and this characteristic is more conducive to the deep energy supply in the hydrate extraction process.

Using the same concentration of the chemical heat generating agent of the present invention (Example 3) and the sulfuric acid catalyst heat generating system to carry out hydrate mining experiments, the heat release rates of the two are compared, and the results are shown in Figure 2. It can be seen from the figure that the appearance time of the heat release peak of the chemical heat generating agent of Example 3 of the present invention is significantly slower than that of the sulfuric acid catalyst heat generating system, and this characteristic is more conducive to the deep energy supply in the hydrate extraction process.

2. Comparison of temperature changes in hydrate reservoirs under different heat injection modes

The hydrate extraction experiment was carried out using the same concentration of the chemical heat generating agent of the present invention (Example 1), the acetic acid catalyst heat generating system and the hot water. The temperature change in the deep part of the reservoir in the hydrate generation tank is shown in Figure 3. The heat release of Example 3 of the present invention shows an obvious "slow release" effect, and the heating effect is better, which is manifested in the well shut-in stage, Example 3 The chemical heat generating agent can still undergo chemical reaction and gradually reach the exothermic peak, and the temperature increase in the hydrate reservoir is significantly higher than that of the conventional acetic acid catalyst heat generating system and hot water injection method, indicating that the chemical heat generating agent of the present invention It has a very obvious in-situ heating effect in the deep reservoir.

3. Comparison of hydrate recovery efficiency under different injection modes

The hydrate extraction efficiency of Examples 1 to 4 of the present invention, conventional acetic acid catalyst heat generation system and hot water were measured and compared, and the results are shown in Table 1. As can be seen from the table, the exploitation efficiency of Examples 1 to 4 is obviously higher than that of the conventional heat generation system and hot water injection, and the exploitation efficiency of Example 3 is as high as 84%.

Table 1 Hydrate recovery efficiency under the injection mode of different heat generators

While the content of the present invention has been described in detail by way of the above preferred embodiments, it should be appreciated that the above description should not be construed as limiting the present invention. Various modifications and alternatives to the present invention will be apparent to those skilled in the art upon reading the foregoing. Accordingly, the scope of protection of the present invention should be defined by the appended claims.

Claims (4)

1. a chemical heat generating agent for natural gas hydrate exploitation, is characterized in that, this heat generating agent comprises: main agent I, main agent II and auxiliary agent; Wherein, the main agent I is composed of the following components by mass and volume percentage: 10-32% NaNO ₂ , 1-7.5% foaming agent, 2-7.5% foam stabilizer, and the balance is water; the foaming agent It is a cationic Gemini quaternary ammonium salt, and the cationic Gemini quaternary ammonium salt is selected from diquaternary ammonium salt adipate; the foam stabilizer is nanoparticles; The auxiliary agent is an acid gas, and the acid gas is selected from CO ₂ and/or SO ₂ , and the volume ratio of the main agent I and the auxiliary agent is 1:4 to 40, and the main agent I and the auxiliary agent are based on volume. than mixing to obtain foam liquid; The main agent II is an NH ₄ Cl aqueous solution, the molar concentration of the NH ₄ Cl aqueous solution is equal to the molar concentration of sodium nitrite in the foam solution, and the volume of the NH ₄ Cl aqueous solution is equal to the volume of the foam solution. 2 . The chemical biothermal agent for natural gas hydrate exploitation according to claim 1 , wherein the nanoparticles are nano-silica particles. 3 . 3. The application of the chemical heat generating agent as claimed in claim 1 or 2 in the exploitation of natural gas hydrate. 4. The application according to claim 3, wherein the auxiliary agent and the main agent I are mixed at a pressure of 4 to 6 MPa to form a foam liquid; an equal volume of the foam liquid and the main agent II are mixed At the same time, the hydrate layer is injected to carry out the hydrate thermal recovery process.

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