Self-heating viscosity-reducing system acting deep within heavy oil, its preparation method and application

Abstract

The application discloses a self-generated heat viscosity reduction system acting on deep thick oil, which is composed of a first medicament and a second medicament, the first medicament is composed of urea, nitrite, a viscosity increasing agent and a solvent, and the second medicament is an acid catalyst wrapped by a temperature control microcapsule. The application further discloses a preparation method of the self-generated heat viscosity reduction system acting on deep thick oil, and the steps are as follows: step (1), dissolving formula amount of urea, formula amount of nitrite and formula amount of the viscosity increasing agent in proper amount of water to form the first medicament with certain viscosity; step (2), adding formula amount of the second medicament into the first medicament obtained in step (1) and stirring uniformly to obtain the self-generated heat viscosity reduction system acting on deep thick oil. The application further discloses application of the self-generated heat viscosity reduction system acting on deep thick oil in thick oil viscosity reduction. The application has the advantages of adjustable reaction delay time, controllable reaction speed, high heat utilization rate and effective viscosity reduction of deep thick oil in the reservoir.

Description

Technical Field

[0001] This invention belongs to the field of heavy oil development technology in oilfields, and specifically relates to a self-generating heat viscosity-reducing system that acts on the deep parts of heavy oil, its preparation method and application. Background Technology

[0002] In heavy oil development, effective viscosity reduction is crucial for improving development efficiency, with thermal viscosity reduction being the most effective method. However, during the development of heavy oil reservoirs using steam injection for thermal viscosity reduction, factors such as heat loss from surface pipelines and wellbore mean that the heat generated by the steam in the reservoir for viscosity reduction is less than 40% of the heat generated by the steam at the surface boiler outlet, resulting in significant energy waste. Furthermore, the low heat and dryness of the steam entering the reservoir lead to a small heat wave range, effectively utilizing only a 30-40m radius around the wellbore.

[0003] The self-generating heating viscosity reduction system involves injecting different chemical substances into heavy oil reservoirs, causing them to react directly within the formation. This generates heat and various gases, and through the synergistic effect of multiple viscosity reduction mechanisms such as thermal viscosity reduction and gas dissolution viscosity reduction, viscosity reduction development of heavy oil reservoirs is achieved. This development method is an in-situ heating viscosity reduction system, avoiding heat loss along the way during steam injection viscosity reduction and improving energy utilization efficiency.

[0004] When reactants in conventional autogenous chemical agents come into contact, a rapid and violent chemical reaction occurs, releasing a large amount of heat in a short period of time. This causes the heat and products generated by the reaction to accumulate in a small area, resulting in a sharp increase in local temperature and pressure in the reservoir. This poses many problems in terms of safety and the extent to which the viscosity reduction zone is affected.

[0005] Currently, in field applications, to prevent chemical reactions from occurring before entering the target reservoir, different reactants are typically prepared into solutions separately. During injection into the reservoir, water sluices are placed between the different reactant solutions. The reactants diffuse freely within the reservoir, and a chemical reaction can only occur if the different reactants come into contact during diffusion. While this method ensures that the chemical reaction occurs within the reservoir, it relies on the free diffusion of reactants in the porous medium of the reservoir. Due to the poor diffusion and transport conditions of reactants in the reservoir, it is difficult to achieve sufficient contact between different reactants, and the reaction mainly occurs near the wellbore. Therefore, this method has consistently suffered from a series of problems in field applications, including low utilization rate of chemical agents, incomplete reaction, and difficulty in effectively reducing viscosity in deep reservoirs. Summary of the Invention

[0006] Purpose of the invention: In view of the shortcomings of the prior art, the present invention provides a self-generating heat viscosity reduction system that acts on the deep part of heavy oil, its preparation method and application. The present invention can solve the problems of large heat loss and small viscosity reduction range in the development of thermal viscosity reduction of heavy oil.

[0007] This invention involves dissolving urea, nitrite, and a thickener in a solvent to form a first agent, and then adding a second agent (temperature-controlled microcapsules encapsulating an acidic catalyst) to the first agent to form a self-heating viscosity-reducing system acting on the deep layers of heavy oil. After the self-heating viscosity-reducing system is injected into the reservoir, it migrates to the target depth within the reservoir. The system is gradually heated by the high formation temperature. When its temperature reaches or exceeds the rupture temperature of the temperature-controlled microcapsules, the microcapsules rupture in batches, releasing the acidic catalyst. Under the action of the acidic catalyst, urea and nitrite in the solution undergo an exothermic reaction, generating nitrogen, carbon dioxide, and high-temperature steam, releasing a large amount of heat.

[0008] The generated heat, high-temperature steam, and carbon dioxide reduce the viscosity of heavy oil. The expansion of gases such as nitrogen and carbon dioxide pushes the autogenous heating viscosity-reducing system and reaction products into the depths of the heavy oil reservoir, achieving expanded reach and deep viscosity reduction.

[0009] Technical solution: A self-heating viscosity-reducing system acting deep within heavy oil, consisting of a first agent and a second agent, wherein:

[0010] The mass ratio of the first agent to the second agent is (15-25):1;

[0011] The first reagent is composed of urea, nitrite, thickener and solvent, wherein the mass ratio of urea, nitrite, thickener and solvent is (3-5):(5-7):(0.2-0.5):(88-92);

[0012] The second agent is an acidic catalyst encapsulated in temperature-controlled microcapsules.

[0013] Furthermore, the nitrite is sodium nitrite and / or potassium nitrite.

[0014] Furthermore, the thickener is one of guar gum, hydroxyethyl tannin, and polyacrylamide.

[0015] Furthermore, the solvent is water.

[0016] Furthermore, the temperature-controlled microcapsules are prepared from shellac and low molecular weight polyethylene.

[0017] Furthermore, the mass ratio of shellac to low molecular weight polyethylene is (8-13):1.

[0018] Furthermore, the relative molecular weight of the low molecular weight polyethylene is <10000.

[0019] Furthermore, the elastic modulus of the second agent is 0.78–0.82 Pa.

[0020] Furthermore, the acidic catalyst is at least one of hydrochloric acid, acetic acid, citric acid, and tartaric acid.

[0021] The specific steps for preparing the above-mentioned self-heating viscosity-reducing system that acts on the deep layers of heavy oil are as follows:

[0022] Step (1): Dissolve the prescribed amount of urea, the prescribed amount of nitrite, and the prescribed amount of thickener in an appropriate amount of water to form a first agent with a certain viscosity;

[0023] Step (2): Add the second agent of the formula amount to the first agent obtained in step (1), stir evenly to obtain a self-heating viscosity reduction system that acts on the deep part of heavy oil.

[0024] Furthermore, the viscosity of the first agent in step 1 is 10–30 mPa·s.

[0025] The above-mentioned self-heating viscosity-reducing system that acts deep within heavy oil is applied to the viscosity reduction of heavy oil.

[0026] Furthermore, the specific steps of the above application are as follows:

[0027] The autogenous heating viscosity reduction system, which acts on the deep layers of heavy oil, is pumped into the target depth of the heavy oil reservoir. As the system flows towards the target depth, it is heated by the high temperature of the reservoir. When the temperature of the autogenous heating viscosity reduction system reaches or exceeds the rupture temperature of the temperature-controlled microcapsules, the microcapsules rupture in batches, releasing the acidic catalyst encapsulated within, thus enabling the reaction to occur deep within the reservoir.

[0028] Furthermore, the rupture temperature range of the temperature-controlled microcapsules is 85% to 115% of the reservoir temperature at the target depth in heavy oil reservoirs.

[0029] Furthermore, the rupture temperature range of the temperature-controlled microcapsules is 90% to 110% of the reservoir temperature at the target depth in heavy oil reservoirs.

[0030] Furthermore, the pumping rate is 100–150 L / min.

[0031] Since the rupture temperature of the temperature-controlled microcapsules is within a certain temperature range that is suitable for the target reservoir phase, as the temperature gradually increases, the temperature-controlled microcapsules rupture in batches and release the acidic catalyst encapsulated within them, which plays a role in controlling and slowing down the reaction rate.

[0032] Under the action of the released acidic catalyst, urea and nitrite in the self-heating viscosity-reducing system react to generate nitrogen and carbon dioxide and release heat, while simultaneously forming high-temperature steam. The reaction equation is as follows:

[0033]

[0034] Among them, CO(NH2)2 is urea. It is nitrite, H + It is an acidic catalyst;

[0035] Heat, high-temperature steam, and carbon dioxide can reduce viscosity through thermal and dissolution processes, working synergistically with the viscosity-reducing effect of the thickener in the first agent to lower the viscosity of heavy oil.

[0036] Meanwhile, nitrogen and carbon dioxide have a good expansion effect in the reservoir, which can push the autogenous heating viscosity reduction system and reaction products into the deep part of the reservoir, thereby expanding the reach and reducing viscosity in the deep part.

[0037] Beneficial effects: This invention features adjustable reaction delay time (adjustable within the range of 0 to 25 min), controllable reaction rate (1℃ / min to 6.5℃ / min), high heat utilization rate, and effective viscosity reduction for heavy oil in deep reservoirs, solving a series of problems in the process of using conventional self-generating thermochemical agents for viscosity reduction of heavy oil. Attached Figure Description

[0038] Figure 1 This is a flowchart of the preparation method of the self-heating viscosity-reducing system that acts on the deep part of heavy oil, as disclosed in this invention. Detailed Implementation

[0039] The specific embodiments of the present invention are described in detail below.

[0040] The endpoints and any values ​​of the ranges disclosed herein are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of the various ranges, the endpoint values ​​of the various ranges and individual point values, and individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed herein.

[0041] To enable those skilled in the art to understand the technical solution of the present invention, the preparation process of the second agent is briefly described below:

[0042] The preparation steps of the second agent:

[0043] S1. From bottom to top, the reaction vessel consists of a cold water layer, a hot water layer, and a membrane material layer, wherein:

[0044] The temperature of the cold water in the cold water layer is controlled at 10℃;

[0045] The temperature of the hot water in the hot water layer is controlled at 95℃;

[0046] The coating material layer is composed of shellac and low molecular weight polyethylene in a mass ratio of (8-13):1, wherein the relative molecular weight of the low molecular weight polyethylene is <10000.

[0047] S2. After heating until the coating material layer is molten, droplets of acidic catalyst with a diameter of about 800 nm are dropped into the container through a nozzle 1.5 cm above the container. The acidic catalyst droplets first pass through the top coating material layer of the container, and their outer periphery is coated with a coating layer with a thickness of about 100 nm. As the droplets continue to fall, they are adjusted into a spherical shape in the hot water layer, and after entering the cold water layer, they are condensed and hardened to obtain temperature-controlled microcapsules.

[0048] The microcapsule rupture temperature can be controlled by adjusting the ratio of shellac to low molecular weight polyethylene (relative molecular weight <10000).

[0049] The temperature control performance of the second agent was verified using the method described above. All other parameters remained unchanged, except for the ratio of shellac to low molecular weight polyethylene in the coating material layer, as detailed below:

[0050] Mass ratio of shellac to low molecular weight polyethylene Coating material layer 1 8:1 Coating material layer 2 10:1 Coating material layer 3 13:1

[0051] Under simulated reservoir temperature of 83℃ and reservoir pressure of 19MPa, the temperature control performance of the temperature-controlled microcapsules composed of coating material layers 1-3 was tested:

[0052] Temperature at which cracking begins (°C) Temperature at which complete rupture occurs (°C) Coating material layer 1 89.9 112.2 Coating material layer 2 81.1 98.9 Coating material layer 3 70.3 93.1

[0053] The temperature control performance of the temperature-controlled microcapsules composed of coating material layers 1-3 was tested separately:

[0054] Elastic modulus (Pa) Coating material layer 1 0.82 Coating material layer 2 0.78 Coating material layer 3 0.8

[0055] Example 1

[0056] The target heavy oil reservoir has a reservoir temperature of 70℃ and a crude oil viscosity of 1244 mPa·s under reservoir conditions.

[0057] The self-heating viscosity-reducing system, which acts deep within heavy oil, consists of a first agent and a second agent, wherein:

[0058] The mass ratio of the first agent to the second agent is 25:1;

[0059] The first reagent is composed of urea, nitrite, thickener and solvent, wherein the mass ratio of urea, nitrite, thickener and solvent is 5:7:0.5:92;

[0060] The second agent is an acidic catalyst encapsulated in temperature-controlled microcapsules.

[0061] Furthermore, the nitrite is sodium nitrite.

[0062] Furthermore, the tackifier is guar gum.

[0063] Furthermore, the solvent is water.

[0064] Furthermore, the temperature-controlled microcapsules are prepared from shellac and low molecular weight polyethylene.

[0065] Furthermore, the mass ratio of shellac to low molecular weight polyethylene is 13:1. This ratio is compatible with the reservoir temperature of the target heavy oil reservoir at 70°C.

[0066] Furthermore, the relative molecular weight of the low molecular weight polyethylene is <10000.

[0067] Furthermore, the elastic modulus of the second agent is 0.8 Pa.

[0068] Furthermore, the acidic catalyst is hydrochloric acid.

[0069] The specific steps for preparing the above-mentioned self-heating viscosity-reducing system that acts on the deep layers of heavy oil are as follows:

[0070] Step (1): Dissolve the prescribed amount of urea, the prescribed amount of nitrite, and the prescribed amount of thickener in an appropriate amount of water to form a first agent with a certain viscosity;

[0071] Step (2): Add the second agent of the formula amount to the first agent obtained in step (1), stir evenly to obtain a self-heating viscosity reduction system that acts on the deep part of heavy oil.

[0072] Furthermore, the viscosity of the first agent in step 1 is 18 mPa·s.

[0073] The above-mentioned self-heating viscosity-reducing system that acts deep within heavy oil is applied to the viscosity reduction of heavy oil.

[0074] Furthermore, the specific steps of the above application are as follows:

[0075] The autogenous heating viscosity-reducing system, which acts on the deep layers of heavy oil, is pumped into the target depth of the heavy oil reservoir. As the system flows towards the target depth, it is heated by the high temperature of the reservoir. When the temperature of the autogenous heating viscosity-reducing system reaches or exceeds the rupture temperature of the temperature-controlled microcapsules, the microcapsules rupture in batches, releasing the acidic catalyst encapsulated within, thereby causing a reaction to occur deep within the reservoir, wherein:

[0076] The pumping rate is 150 L / min.

[0077] After subsequent testing, the self-heating viscosity reduction system prepared in Example 1, which acts on the deep part of heavy oil, has an enthalpy utilization rate of 84.2%, achieving effective viscosity reduction within a 75m range of the oil well.

[0078] Example 2

[0079] The target heavy oil reservoir has a reservoir temperature of 80℃ and a crude oil viscosity of 2170 mPa·s under reservoir conditions.

[0080] The self-heating viscosity-reducing system, which acts deep within heavy oil, consists of a first agent and a second agent, wherein:

[0081] The mass ratio of the first agent to the second agent is 20:1;

[0082] The first reagent is composed of urea, nitrite, thickener and solvent, wherein the mass ratio of urea, nitrite, thickener and solvent is 4:6:0.3:90;

[0083] The second agent is an acidic catalyst encapsulated in temperature-controlled microcapsules.

[0084] Furthermore, the nitrite is potassium nitrite.

[0085] Furthermore, the thickener is hydroxyethyl phthalate powder.

[0086] Furthermore, the solvent is water.

[0087] Furthermore, the temperature-controlled microcapsules are prepared from shellac and low molecular weight polyethylene.

[0088] Furthermore, the mass ratio of shellac to low molecular weight polyethylene is 10:1. This ratio is compatible with the reservoir temperature of the target heavy oil reservoir at 80°C.

[0089] Furthermore, the relative molecular weight of the low molecular weight polyethylene is <10000.

[0090] Furthermore, the elastic modulus of the second agent is 0.78 Pa.

[0091] Furthermore, the acidic catalyst is acetic acid.

[0092] In another embodiment, the acidic catalyst is citric acid.

[0093] In yet another embodiment, the acidic catalyst is tartaric acid.

[0094] The specific steps for preparing the above-mentioned self-heating viscosity-reducing system that acts on the deep layers of heavy oil are as follows:

[0095] Step (1): Dissolve the prescribed amount of urea, the prescribed amount of nitrite, and the prescribed amount of thickener in an appropriate amount of water to form a first agent with a certain viscosity;

[0096] Step (2): Add the second agent of the formula amount to the first agent obtained in step (1), stir evenly to obtain a self-heating viscosity reduction system that acts on the deep part of heavy oil.

[0097] Furthermore, the viscosity of the first agent in step 1 is 10.2 mPa·s.

[0098] The above-mentioned self-heating viscosity-reducing system that acts deep within heavy oil is applied to the viscosity reduction of heavy oil.

[0099] Furthermore, the specific steps of the above application are as follows:

[0100] The autogenous heating viscosity reduction system, which acts on the deep layers of heavy oil, is pumped into the target depth of the heavy oil reservoir. As the system flows towards the target depth, it is heated by the high temperature of the reservoir. When the temperature of the autogenous heating viscosity reduction system reaches or exceeds the rupture temperature of the temperature-controlled microcapsules, the microcapsules rupture in batches, releasing the acidic catalyst encapsulated within, thus enabling the reaction to occur deep within the reservoir.

[0101] Furthermore, the pumping rate is 100 L / min.

[0102] After subsequent testing, the self-heating viscosity reduction system prepared in Example 2, which acts on the deep part of heavy oil, has an enthalpy utilization rate of 73.2%, achieving effective viscosity reduction within a 68m range of the oil well.

[0103] Example 3

[0104] The target heavy oil reservoir has a reservoir temperature of 95℃ and a crude oil viscosity of 947 mPa·s under reservoir conditions.

[0105] The self-heating viscosity-reducing system, which acts deep within heavy oil, consists of a first agent and a second agent, wherein:

[0106] The mass ratio of the first agent to the second agent is 15:1;

[0107] The first reagent is composed of urea, nitrite, thickener and solvent, wherein the mass ratio of urea, nitrite, thickener and solvent is 3:5:0.2:88;

[0108] The second agent is an acidic catalyst encapsulated in temperature-controlled microcapsules.

[0109] Furthermore, the nitrite is a mixture of sodium nitrite and potassium nitrite in equal mass ratios.

[0110] Furthermore, the thickener is polyacrylamide.

[0111] Furthermore, the solvent is water.

[0112] Furthermore, the temperature-controlled microcapsules are prepared from shellac and low molecular weight polyethylene.

[0113] Furthermore, the mass ratio of shellac to low molecular weight polyethylene is 8:1. This ratio is compatible with the reservoir temperature of the target heavy oil reservoir at 95°C.

[0114] Furthermore, the relative molecular weight of the low molecular weight polyethylene is <10000.

[0115] Furthermore, the elastic modulus of the second agent is 0.82 Pa.

[0116] Furthermore, the acidic catalyst is a mixture of hydrochloric acid, acetic acid, citric acid, and tartaric acid in equal mass ratios.

[0117] The specific steps for preparing the above-mentioned self-heating viscosity-reducing system that acts on the deep layers of heavy oil are as follows:

[0118] Step (1): Dissolve the prescribed amount of urea, the prescribed amount of nitrite, and the prescribed amount of thickener in an appropriate amount of water to form a first agent with a certain viscosity;

[0119] Step (2): Add the second agent of the formula amount to the first agent obtained in step (1), stir evenly to obtain a self-heating viscosity reduction system that acts on the deep part of heavy oil.

[0120] Furthermore, the viscosity of the first agent in step 1 is 29.8 mPa·s.

[0121] The above-mentioned self-heating viscosity-reducing system that acts deep within heavy oil is applied to the viscosity reduction of heavy oil.

[0122] Furthermore, the specific steps of the above application are as follows:

[0123] The autogenous heating viscosity reduction system, which acts on the deep layers of heavy oil, is pumped into the target depth of the heavy oil reservoir. As the system flows towards the target depth, it is heated by the high temperature of the reservoir. When the temperature of the autogenous heating viscosity reduction system reaches or exceeds the rupture temperature of the temperature-controlled microcapsules, the microcapsules rupture in batches, releasing the acidic catalyst encapsulated within, thus enabling the reaction to occur deep within the reservoir.

[0124] Furthermore, the pumping rate is 135 L / min.

[0125] After subsequent testing, the self-heating viscosity reduction system prepared in Example 3, which acts on the deep part of heavy oil, has an enthalpy utilization rate of 78.2%, achieving effective viscosity reduction within a 72m range of the oil well.

[0126] The embodiments of the present invention have been described in detail above. However, the present invention is not limited to the above embodiments, and various changes can be made within the scope of knowledge possessed by those skilled in the art without departing from the spirit of the present invention.

Claims

1. A self-generating heat viscosity reduction system acting on the deep part of heavy oil, characterized in that, consisting of a first medicament and a second medicament, wherein: the mass ratio of the first medicament to the second medicament is (15-25):1; the first medicament consists of urea, nitrite, tackifier and solvent, wherein the mass ratio of urea, nitrite, tackifier and solvent is (3-5):(5-7):(0.2-0.5):(88-92); the second medicament is an acid catalyst wrapped by temperature-controlled microcapsules, wherein: the tackifier is one of guanidium gum, hydroxyethyl starch and polyacrylamide; the solvent is water; the temperature-controlled microcapsules are prepared from shellac and low-molecular-weight polyethylene; the relative molecular weight of the low-molecular-weight polyethylene is <10000; the acid catalyst is at least one of hydrochloric acid, acetic acid, citric acid and tartaric acid.

2. The self-generating heat deep-acting viscosity reduction system for thick oil according to claim 1, characterized in that, the nitrite is sodium nitrite and / or potassium nitrite.

3. The self-generating heat deep-acting viscosity reduction system for thick oil according to claim 1, characterized in that, the mass ratio of shellac to low-molecular-weight polyethylene is (8-13):

1.

4. The self-generating heat deep-acting viscosity reduction system for heavy oil of claim 1, wherein, the elastic modulus of the second medicament is 0.78-0.82 Pa.

5. The method for preparing the self-generating heat deep-acting viscosity reduction system for heavy oil of any one of claims 1-4, characterized in that, The specific steps are as follows: Step (1), dissolving the formula amount of urea, the formula amount of nitrite and the formula amount of tackifier in an appropriate amount of water to form a first medicament with a certain viscosity; Step (2), adding the formula amount of the second medicament to the first medicament obtained in Step (1) and stirring uniformly to obtain a self-generating heat viscosity-reducing system for deep heavy oil.

6. The method for preparing the self-generating heat deep-acting viscosity reduction system for thick oil according to claim 5, characterized in that, The viscosity of the first medicament in Step (1) is 10-30 mPa.s.

7. The use of the self-generating heat viscosity-reducing system for deep heavy oil in the viscosity reduction of heavy oil.

8. Use according to claim 7, wherein the compound is ###0002### The specific steps of the above use are as follows: pumping the self-generating heat viscosity-reducing system for deep heavy oil into the target depth of heavy oil reservoir.

9. Use according to claim 8, wherein the compound is ###0002### The rupture temperature range of the temperature-controlled microcapsules is 85%-115% of the reservoir temperature at the target depth of heavy oil reservoir.

10. Use according to claim 9, wherein The rupture temperature range of the temperature-controlled microcapsules is 90%-110% of the reservoir temperature at the target depth of heavy oil reservoir.

11. Use according to claim 8, wherein the compound is ###0002### The pumping speed is 100-150 L / min.

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