Liquid energetic material composed of non-dangerous chemical raw materials and preparation method thereof

Abstract

The invention discloses a liquid energetic material composed of non-dangerous chemical raw materials and a preparation method of the liquid energetic material, the liquid energetic material is formed by mixing an oxidizing agent concentrated solution and glycerin in proportion, and the oxidizing agent concentrated solution is obtained by mixing calcium ammonium nitrate, ammonium carbonate and water in proportion and then conducting filtration and vacuum concentration. According to the invention, the prior art is greatly improved, and the three raw materials are all non-dangerous chemicals, so that the traffic and storage safety in the long-time land and marine transportation process in the offshore oilfield operation can be greatly improved; the mode of obtaining the liquid energetic material on site is simple, and seamless butt joint operation with existing liquid gunpowder deflagration fracturing can be achieved; the influence of temperature on solubility is overcome, the composition proportion is moderate, the system can be completely dissolved after being prepared, the operation water adding amount is reduced by utilizing crystal water in the raw materials, and the preparation method is suitable for the environment in shortage of water resources.

Description

Technical Field

[0001] This invention belongs to the field of reservoir stimulation technology of liquid explosive combustion fracturing (or liquid explosive high-energy gas fracturing), specifically relating to a liquid energetic material composed of non-hazardous chemical raw materials and its application method. Background Technology

[0002] The efficient development of low-permeability reservoirs is a crucial long-term challenge for offshore oilfields, with increasingly prominent issues of reserve degradation. In recent years, proven reserves in deep formations, deep water, high-temperature and high-pressure reservoirs, low-porosity and low-permeability reservoirs, buried hills, and lithological reservoirs have accounted for 83% of total reserves. To overcome this challenge, offshore oilfields have continuously innovated and developed fracturing technologies such as hydraulic fracturing, pressure drive, and deflagration fracturing. Among these, deflagration fracturing technology is a low-cost technology suitable for the stimulation of near-water, low-permeability reservoirs. Through nearly a decade of research, offshore oilfields have pioneered 12 original technologies in three categories: deflagration fracturing efficiency enhancement, deflagration fracturing with different well completion methods, and safety control of deflagration fracturing on offshore platforms. These technologies have been assessed as reaching international advanced levels and have successfully restored production to 24 low-yield, low-efficiency wells and long-term shut-in wells, resulting in a cumulative increase of 284,000 cubic meters of oil and 102,600 cubic meters of injection, representing an 8.6-fold increase in production. Construction safety was 100%, and the effectiveness and safety of these technologies have been verified, with further expansion of their application planned.

[0003] Currently, offshore oilfield deflagration fracturing technology mainly uses solid explosives, which faces challenges such as limited modification range (burning within 1 second, 3-8 fractures, single fracture length 1-15m), high peak pressure (60-120MPa), and high qualification requirements (transportation, design). Liquid explosive fracturing technology uses liquid explosives to generate high-temperature, high-pressure gas in the wellbore or formation to fracture and enhance formation production. Depending on the type of liquid explosive and the construction method, it can be divided into "liquid explosive fracturing," "liquid explosive deflagration (or liquid explosive high-energy gas fracturing)," and "intra-formation explosion" technologies. Taking liquid explosive deflagration as an example, it has advantages such as a large modification range (pressure duration up to 40-50s), moderate peak fracturing pressure (50-80MPa), low cost, safety, and wide adaptability. Domestic scholars consider it the only fracturing production enhancement technology comparable to hydraulic fracturing or a strategic and forward-looking innovative technology.

[0004] In the 1990s, scholars such as Wang Anshi and Liu Faxi from Xi'an Petroleum University began to develop a new generation of liquid explosives composed of ammonium nitrate, glycerol, and water. The more reasonable ratio of ammonium nitrate to glycerol is (3.17~4.0):1, and the water content should be maintained within the range of 20% to 30% (see “Wang Anshi, Liu Faxi. Theoretical formulation optimization design of liquid explosives for high-energy gas fracturing [J]. Journal of Xi'an Petroleum Institute (Natural Science Edition), 1994, 9(4): 4-6.”; “Wang Anshi. Research on ignition and combustion of liquid explosives for high-energy gas fracturing [J]. Journal of Xi'an Petroleum Institute (Natural Science Edition), 1995, 10(3): 55-57.”; “Tian Hejin, Zhang Xinqing, Zhang Jie, et al. Liquid explosive high-energy gas fracturing technology [J]. Natural Gas Industry, 2004, 24(9): (75-79) and was first successfully tested in the Xin 257 exploratory well of Jilin Oilfield in 1992. Field application began in Xinjiang Oilfield, Liaohe Oilfield, Zhongyuan Oilfield, Changqing Oilfield, and Daqing Oilfield in 1998, with successful results. Statistics show that the technology was successfully applied in 17 wells in Zhongyuan Oilfield, with a 100% success rate and an implementation efficiency of 93.5%. Before construction, the average fluid production was 6.92 t / d and the average oil production was 2.89 t / d; after construction, the average fluid production was 15.71 t / d and the average oil production was 7.17 t / d, with an average effective period of 132 days and an input-output ratio of 1:6.35. It possesses technical advantages such as low cost and good stimulation effect in the future low-permeability development of offshore oilfields, and is considered an important technical direction for future research.

[0005] Meanwhile, ammonium nitrate, as the main oxidizer in the formula, is widely used in fertilizers and industrial explosives. As early as the mid-19th century, Swedish engineers patented a method of using ammonium nitrate and other accelerants to support mixed explosives. Ammonium nitrate has extremely poor stability at high temperatures; above 230 degrees Celsius, its decomposition produces oxygen, posing a fire risk. Further increases in temperature cause the decomposition to become extremely violent, leading to a violent explosion. Since 2001, relevant national departments have classified it as an explosive hazardous chemical, and in 2002, a document was issued prohibiting the direct application of ammonium nitrate in fertilizers. Furthermore, safety accidents caused by ammonium nitrate have been frequent. Therefore, the transportation safety and qualification issues of liquid explosive technology have faced significant challenges, and after 2000, this technology gradually faded from oilfield production.

[0006] Currently, invention patents involving liquid explosives in the fields of deflagration fracturing or high-energy gas fracturing technology mainly concern devices or processes. Examples include CN105064972B "A liquid explosive capsule fracturing projectile for oil and gas field reservoirs and its application process", CN1584288 "Liquid explosive fracturing method and device for oil and gas reservoirs", CN111734384A "A liquid explosive deflagration fracturing method and its application", and CN116816322A "A liquid explosive-explosive synergistic fracturing method for horizontal well oil reservoirs". The main patent involving liquid explosives is CN106748597A "A liquid explosive that can flow in the formation for high-energy gas fracturing". CN106748597A discloses a liquid explosive that can flow in formations for high-energy gas fracturing, comprising the following components in the following weight ratio: ammonium nitrate: potassium nitrate: glycerol: water = 5~6.5: 0~1: 1~2: 2~3 (i.e., covering the new generation of liquid explosives developed by Xi'an Petroleum University in the 1990s with ammonium nitrate, glycerol, and water as components), but its composition still includes ammonium nitrate as the main hazardous chemical. Besides this, existing liquid explosive fracturing technologies mainly include nitroglycerin-based liquid explosives, water-based thickened liquid explosives, and nitroalkane-based liquid explosives. In-formation fracturing technology also uses emulsion explosives or liquid explosives.

[0007] In summary, there is currently a lack both domestically and internationally of liquid explosive detonation fracturing technology that can overcome the limitations of liquid explosives composed of hazardous chemicals such as ammonium nitrate, while simultaneously avoiding safety risks and hazardous chemical qualification issues during land and sea transportation and storage. Summary of the Invention

[0008] This invention is proposed to solve the problems existing in the prior art, and its purpose is to provide a liquid energetic material composed of non-hazardous chemical raw materials and its method of use.

[0009] This invention is achieved through the following technical solution: A liquid energetic material composed of non-hazardous chemical raw materials, wherein the liquid energetic material comprises the following components and the mass fraction of each component: Oxidizing agent concentrate 80.5%~84%; Glycerin 16%~19.5%; The oxidant concentrate comprises the following components and their mass fractions: Calcium ammonium nitrate [5Ca(NO3)2•NH4NO3•10H2O] 27%~30%; Ammonium carbonate [(NH4)2CO3] 2.5%~16.5%; Water balance.

[0010] In the above technical solution, the chemical formula of the ammonium calcium nitrate is 5Ca(NO3)2•NH4NO3•10H2O. Ammonium calcium nitrate is a highly efficient and environmentally friendly green fertilizer, mainly used in greenhouses and field cultivation of grain crops, cash crops, flowers, fruit trees, and vegetables. This product requires the use of a safer ammonium calcium nitrate product [5Ca(NO3)2•NH4NO3•10H2O], avoiding the use of ammonium calcium nitrate products [nNH4NO3•CaCO3]. Ammonium carbonate is mainly used in food as a buffer, neutralizer, leavening agent, and fermentation promoter. Glycerin is mainly used as a sweetener in the food industry and a humectant in pharmaceutical formulations, and is also a liquid propellant in liquid explosive combustion fracturing technology. None of the above three raw materials are listed in the national "List of Hazardous Chemicals".

[0011] In the above technical solution, the temperature of the water is 30℃~45℃; the proportion of water added is adjusted according to different ambient temperatures, and the hot water added is mainly to prevent ammonium nitrate from freezing due to endothermic reaction during the preparation process.

[0012] In the above technical solution, the operating environment temperature for the liquid energetic material used in the deflagration fracturing technology is 18℃~45℃.

[0013] A method for preparing the aforementioned liquid energetic material composed of non-hazardous chemical raw materials includes the following steps: (I) Preparation of ammonium nitrate oxidant solution Add calcium ammonium nitrate and ammonium carbonate to a mixing tank, then add water and stir. Then pump the liquid in the mixing tank into a liquid tank containing a filter to filter out the indirectly generated calcium carbonate precipitate, thus making an ammonium nitrate oxidant solution. (II) Reduced pressure concentration The ammonium nitrate oxidant solution was transferred to a vacuum concentration vessel, the vacuum degree was set to -95 kPa, and the vacuum concentration temperature was 55℃~65℃. During the process, samples were taken to detect the concentration of ammonium nitrate in the solution. When the concentration of ammonium nitrate was ≥65%, the vacuum concentration was stopped to obtain the oxidant concentrate. (III) Preparation of liquid energetic materials The oxidant concentrate is mixed with glycerol to produce a liquid energetic material.

[0014] In the above technical solution, the stirring time after adding water in step (I) is 10 min to 30 min.

[0015] In the above technical solution, the vacuum degree of step (II) concentration is set to -95 kPa and the concentration temperature is 40℃~60℃; mechanical stirring or magnetic stirring is carried out simultaneously during the concentration process, and the stirring speed is 100 rad / min~500 rad / min.

[0016] In the above technical solution, the concentration requirement for ammonium nitrate when stopping vacuum concentration in step (II) is: the mass concentration of ammonium nitrate ≥ 65%.

[0017] In the above technical solution, the method for detecting the concentration of ammonium nitrate in the solution in step (II) adopts the formaldehyde method in 5.1.3 of GB / T2945-2017.

[0018] In the above technical solution, the ambient temperature for steps (I) to (III) is 18℃ to 45℃.

[0019] The beneficial effects of this invention are: This invention provides a liquid energetic material composed of non-hazardous chemical raw materials and its application method. It utilizes three non-hazardous chemical raw materials—calcium ammonium nitrate, ammonium carbonate, and glycerol—for transportation and storage. When operations are required, the calcium ammonium nitrate and ammonium carbonate are mixed with an appropriate proportion of water to indirectly produce a mixture of ammonium nitrate, calcium carbonate, and water. After filtering out the calcium carbonate precipitate, glycerol is added to form the liquid energetic material for liquid explosive fracturing operations. This invention represents a significant improvement over existing technologies. All three raw materials are non-hazardous chemicals, greatly enhancing transportation and storage safety during long-term land and sea transport in offshore oilfield operations. The method for obtaining the liquid energetic material on-site is simple, allowing for seamless integration with existing liquid explosive fracturing operations. It overcomes the influence of temperature on solubility, has a suitable composition ratio, and the system is completely soluble after preparation. Furthermore, it utilizes the crystal water in the raw materials to reduce the amount of water added during operations, making it suitable for environments with water scarcity. Detailed Implementation

[0020] To enable those skilled in the art to better understand the technical solution of the present invention, the technical solution of the present invention will be further described below through specific embodiments.

[0021] Example 1 A method for preparing a liquid energetic material composed of non-hazardous chemical raw materials includes the following steps: (I) Transportation and storage of raw materials for liquid energetic materials The required weights of the three non-hazardous chemical raw materials—calcium ammonium nitrate, ammonium carbonate, and glycerol—are transported and stored separately. (II) On-site preparation of ammonium nitrate oxidant solution At an ambient temperature of 18℃, 1080 kg of calcium ammonium nitrate (industrial grade) [5Ca(NO3)2•NH4NO3•10H2O] and 1000 kg of water at 30℃ were mixed and stirred for 30 min to form reaction solution A. 490 kg of ammonium carbonate (industrial grade) and 1000 kg of water were mixed and stirred to form reaction solution B. Reaction solution A was poured into reaction solution B, and mechanical stirring was carried out at a speed of 100 rad / min. The addition was completed in 10 min, and stirring was continued for 30 min. Then, the liquid in the stirring tank was pumped into a liquid tank containing a filter to filter out the indirectly generated calcium carbonate precipitate, forming an ammonium nitrate oxidant solution. (III) Reduced pressure concentration The ammonium nitrate oxidant solution was transferred to a vacuum concentration vessel, vacuum degree -95 kPa, magnetic stirring speed 100 rad / min, heating temperature 55℃, to obtain 1060 kg of oxidant concentrate. The ammonium nitrate concentration was 66% by formaldehyde method. (IV) Preparation of liquid energetic materials Take 840 kg of concentrated liquid and mix it with 160 kg of glycerol to make 1000 kg of liquid energetic material. Carry out the construction according to the current liquid explosive combustion fracturing technology.

[0022] Example 2 A method for preparing a liquid energetic material composed of non-hazardous chemical raw materials includes the following steps: (I) Transportation and storage of raw materials for liquid energetic materials The required weights of the three non-hazardous chemical raw materials—calcium ammonium nitrate, ammonium carbonate, and glycerol—are transported and stored separately. (II) On-site preparation of ammonium nitrate oxidant solution At an ambient temperature of 30℃, 810 kg of calcium ammonium nitrate (industrial grade) [5Ca(NO3)2•NH4NO3•10H2O] and 800 kg of water at 40℃ were mixed and stirred for 15 min to dissolve and form reaction solution A. 480 kg of ammonium carbonate (industrial grade) and 910 kg of water were mixed and stirred to dissolve and form reaction solution B. Reaction solution A was poured into reaction solution B, and mechanical stirring was carried out at a speed of 100 rad / min for 15 min. After the addition was completed, stirring was continued for 35 min. Then, the liquid in the stirring tank was pumped into a liquid tank containing a filter to filter out the indirectly generated calcium carbonate precipitate, forming an ammonium nitrate oxidant solution. (III) Reduced pressure concentration The ammonium nitrate oxidant solution was transferred to a vacuum concentration vessel, vacuum degree -95 kPa, mechanical stirring speed 300 rad / min, heating temperature 60℃, to obtain 710 kg of oxidant concentrate. The ammonium nitrate concentration was determined to be 70% by formaldehyde method. (IV) Preparation of liquid energetic materials Take 492 kg of oxidant concentrate and mix it with 108 kg of glycerol to make 600 kg of liquid energetic material. Carry out the operation according to the current liquid explosive combustion fracturing technology.

[0023] Example 3 A method for preparing a liquid energetic material composed of non-hazardous chemical raw materials includes the following steps: (I) Transportation and storage of raw materials for liquid energetic materials The required weights of the three non-hazardous chemical raw materials—calcium ammonium nitrate, ammonium carbonate, and glycerol—are transported and stored separately. (II) On-site preparation of ammonium nitrate oxidant solution At an ambient temperature of 45℃, 1120g of calcium ammonium nitrate (industrial grade) [5Ca(NO3)2•NH4NO3•10H2O] and 1200kg of water at 45℃ were mixed and stirred for 10 minutes to form reaction solution A. 600kg of ammonium carbonate (industrial grade) and 1080kg of water were mixed and stirred to form reaction solution B. Reaction solution A was injected into reaction solution B, and mechanical stirring was carried out at a speed of 100 rad / min. The addition was completed in 25 minutes, and stirring was continued for 40 minutes. Then, the liquid in the stirring tank was pumped into a liquid tank containing a filter to filter out the indirectly generated calcium carbonate precipitate, forming an ammonium nitrate oxidant solution. (III) Reduced pressure concentration The ammonium nitrate oxidant solution was transferred to a vacuum concentration vessel, vacuum degree -95 kPa, magnetic stirring speed 500 rad / min, heating temperature 65℃, to obtain 830 kg of oxidant concentrate. The ammonium nitrate concentration was determined to be 75% by formaldehyde method. (IV) Preparation of liquid energetic materials Take 810 kg of oxidant concentrate and mix it with 190 kg of glycerol to make 1000 kg of liquid energetic material. Carry out the operation according to the current liquid explosive combustion fracturing technology.

[0024] Compared with the prior art, the present invention: 1. Significantly improved safety: Based on the existing liquid explosive technology composed of "ammonium nitrate (a hazardous chemical), glycerol and water", the liquid energetic material is composed of three non-hazardous chemical raw materials: calcium ammonium nitrate, ammonium carbonate and glycerol, and water. The industrial source is wide, and calcium ammonium nitrate and ammonium carbonate are generally used as green and environmentally friendly agricultural fertilizers. The safety is controllable, which can greatly improve the transportation and storage safety during long-term land and sea transportation in offshore oil field operations.

[0025] 2. Simple and easy construction: During on-site operation, ammonium nitrate and calcium carbonate are mixed with water to indirectly produce a mixture of ammonium nitrate, calcium carbonate and water. The mixture is quickly separated through solid-liquid mode, and the calcium carbonate precipitate is filtered out. The on-site acquisition method is simple. After depressurization and concentration, the semi-finished product of oxidizer ammonium nitrate and water can be obtained, which can be seamlessly connected with the existing liquid explosive deflagration fracturing operation.

[0026] 3. The composition ratio is moderate, and the system can be completely dissolved after preparation. At the same time, the crystal water in the raw materials is used to reduce the amount of water added during operation, which is suitable for environments with scarce water resources: This patent is not a simple improvement on the original liquid explosive technology. In order to overcome the large influence of ambient temperature on the indirect product ammonium nitrate, the effect is evaluated by experiments and through precise calculations, the concentration ratio of the four substances under various temperature conditions is given, so as to achieve complete dissolution of the indirect product ammonium nitrate in water and avoid the impact of ammonium nitrate crystal particles on the operation effect. At the same time, by utilizing the 10 crystal water molecules in calcium ammonium nitrate, a semi-finished product can be formed by adding water appropriately, which greatly reduces the amount of water used and is suitable for environments such as offshore oil fields with scarce fresh water resources.

[0027] The applicant declares that the above description is only a specific embodiment of the present invention, but the protection scope of the present invention is not limited thereto. Those skilled in the art should understand that any changes or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in the present invention fall within the protection and disclosure scope of the present invention.

Claims

1. A liquid energetic material composed of non-hazardous chemical raw materials, characterized in that: The liquid energetic material comprises the following components and the mass fraction of each component: Oxidizing agent concentrate 80.5%~84%; Glycerin 16%~19.5%; The oxidant concentrate comprises the following components and their mass fractions: Calcium ammonium nitrate 27%~30%; Ammonium carbonate 12.5%~16.5%; Water balance.

2. The liquid energetic material composed of non-hazardous chemical raw materials according to claim 1, characterized in that: The chemical formula of the calcium ammonium nitrate is 5Ca(NO3)2•NH4NO3•10H2O.

3. The liquid energetic material composed of non-hazardous chemical raw materials according to claim 1, characterized in that: The temperature of the water is 30℃~45℃.

4. The liquid energetic material composed of non-hazardous chemical raw materials according to claim 1, characterized in that: The operating environment temperature for the liquid energetic material used in the deflagration fracturing technology is 18℃~45℃.

5. A method for preparing a liquid energetic material composed of non-hazardous chemical raw materials as described in any one of claims 1 to 4, characterized in that: Includes the following steps: (I) Preparation of ammonium nitrate oxidant solution Add calcium ammonium nitrate and ammonium carbonate to a mixing tank, then add water and stir. Filter the liquid in the mixing tank to obtain an ammonium nitrate oxidant solution. (II) Reduced pressure concentration The ammonium nitrate oxidant solution was concentrated under reduced pressure until the ammonium nitrate concentration met the requirements, at which point the concentration was stopped to obtain the concentrated oxidant solution. (III) Preparation of liquid energetic materials The oxidant concentrate is mixed with glycerol to produce a liquid energetic material.

6. The method for preparing a liquid energetic material composed of non-hazardous chemical raw materials according to claim 5, characterized in that: The stirring time after adding water in step (I) is 10 min to 30 min.

7. The method for preparing a liquid energetic material composed of non-hazardous chemical raw materials according to claim 5, characterized in that: The vacuum degree of step (II) concentration is set to -95 kPa, and the concentration temperature is 55℃~65℃. During the concentration process, stirring is carried out at a speed of 100 rad / min~500 rad / min.

8. The method for preparing a liquid energetic material composed of non-hazardous chemical raw materials according to claim 5, characterized in that: The required concentration of ammonium nitrate at the point where the vacuum concentration is stopped in step (II) is: the mass concentration of ammonium nitrate ≥ 65%.

9. The method for preparing a liquid energetic material composed of non-hazardous chemical raw materials according to claim 5, characterized in that: The ambient temperature for steps (I) to (III) is 18℃ to 45℃.