An in-situ cracking and upgrading method for preparing nanocatalysts downhole

Abstract

The application provides an in-situ cracking and modification method for preparing nanometer catalysts in a well, which comprises the following steps: sending a nanometer catalyst precursor into a gas burner while the gas burner is heating a stratum; under the high-temperature condition generated by the gas burner, using the principle of generating nanometer crystals by a gas phase method to make the nanometer catalyst precursor react to generate nanometer catalysts which can promote the conversion of organic matter in shale and low-mature shale into light oil; and under the driving of tail gas generated by the gas burner, the generated nanometer catalysts are carried into the oil shale layer together with the tail gas to catalyze the conversion of the organic matter. The preparation method belongs to a heating method which can save energy, improve the energy utilization rate of low-mature shale oil and oil shale, and reduce the cost. The catalyst particles prepared by the gas phase method are small, the in-situ synthesis has good carrying property, and the use of water in the traditional fracturing fluid carrying process is avoided.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of downhole heating, in particular to an in-situ cracking and upgrading method for preparing nanometer catalyst in a downhole. BACKGROUND

[0002] In recent years, the dependence on foreign oil has gradually increased, and it is urgent to increase the domestic oil supply. The resource potential of continental shale oil in China is huge, especially the medium and low mature shale oil and oil shale.

[0003] Oil shale, also known as oil mother shale, is a high-ash solid combustible organic mineral. Low-temperature dry distillation can obtain shale oil with an oil content of >3.5% and a high organic matter content, and its calorific value is generally ≥4187J / g. More than 90% of the organic components inside the oil shale are immature kerogen organic matter. In China, the oil shale oil resource reserves are very rich. From 2003 to 2006, China conducted the first domestic evaluation of oil shale resources, and found that the geological resources were 7199 million tons, equivalent to 476 million tons of cracking oil (1000 meters or less).

[0004] Academician Zhao Wen-zhi defines oil shale oil with Ro of 0.5%~1% and unconverted organic matter of 40%~80% as medium and low mature shale oil, which has considerable overlap with traditional oil shale resources. Based on laboratory data and existing geological data, the Exploration and Development Research Institute of PetroChina estimates that the technically recoverable oil resources of continental shale oil in China are about (700-900) × 108t, which is 3-4 times the total amount of technically recoverable resources of conventional oil. It is mainly distributed in the Ordos Basin, Songliao Basin and Junggar Basin three large depression-type sedimentary basins.

[0005] Oil shale is usually processed into oil shale oil by dry distillation. The most mature oil shale mining process in industry is oil shale dry distillation on the ground, but compared with in-situ conversion technology, the mining cost of dry distillation on the ground is high, the land occupation is large, and the environmental pollution is large, while the in-situ conversion technology is a relatively environmentally friendly process with better oil quality. Because the organic matter of medium and low mature shale oil is low in maturity, it contains a large amount of solid kerogen and asphaltene, which must be heated for a long time to make kerogen and asphaltene crack and upgrade into light oil. Therefore, oil shale and medium and low mature shale oil need to use in-situ conversion technology for large-scale development.

[0006] In-situ conversion technology refers to the direct in-situ conversion and extraction of organic matter in underground oil shale or medium- to low-maturity shale oil reservoirs, without the need to mine the oil shale ore to the surface. The development of in-situ oil shale technology can be divided into two stages. The first stage, from the 1950s to the 1980s, primarily focused on combustion heating technology. In the 1990s, international oil companies, led by Shell, launched a second wave of research into in-situ oil shale technology, this time primarily focusing on in-situ physical heating of oil shale. Early in-situ combustion heating technology for oil shale obtained the heat required for in-situ pyrolysis by burning a portion of the organic matter in the oil shale. Based on whether in-situ mining was required, the in-situ conversion processes at that time could be divided into two main categories: True In Situ and Modified In Situ. The TIS method does not require mining; after drilling on the surface, relevant processes are used to improve formation permeability, then the oil shale is heated to induce a pyrolysis and combustion reaction, and finally, the pyrolyzed oil and gas are extracted from the production well. The MIS method requires mining techniques to create voids in the ore layer, followed by blasting to break up the remaining oil shale, thus increasing the layer's permeability. A pyrolysis reaction is then achieved through heating and ignition, ultimately extracting the pyrolyzed oil and gas from the well. Later, Shell proposed the In-Situ Conversion Process (ICP) technology. This technology involves drilling vertical holes into the oil shale formation, then using electric heaters to heat the oil shale underground to 650–700℉ (340–370℃). In commercial mining, ICP technology requires 3–6 years to heat the formation to pyrolysis temperature, allowing pyrolysis oil to be extracted from the formation. The pyrolysis products are collected during extraction in the heated zone. Electrofrac™ technology was proposed by ExxonMobil in 1990. It involves hydraulic fracturing the oil shale, filling the resulting fractures with a conductive proppant to form an electrically heated body. Heat is transferred to the oil shale through a proppant, producing oil and gas which are extracted using conventional methods. Geothermic Fuel Cell (GFC) technology, proposed by Independent Energy Partners (IEP), utilizes the reaction heat of a high-temperature fuel cell stack to directly heat the oil shale formation, producing oil and gas products, which are then transported to the surface through production wells. Some of the gas is purified, reformed, and reinjected into the production wells, while the remainder can be sold. LLNL radio frequency technology, proposed in the late 1970s by the Illinois Institute of Technology, is a method for heating oil shale using radio frequency technology, later developed by Lawrence Livermore National Laboratory. This technology initially utilizes combined electrodes to heat deep oil shale formations.

[0007] Numerous scholars have studied in-situ conversion technology for oil shale, finding that conductive heating results in slow heat transfer, long heating time, low conductivity, high cost, and significant impact from groundwater on the process. In contrast, fluid heating methods such as combustion and convection offer advantages such as high heating efficiency, high extraction rate, and easy production of oil and gas products, leading to high economic benefits and ease of implementation. Therefore, fluid heating is a more efficient method. Currently, fluid heating technologies include:

[0008] EGL technology, developed and patented by EGL Corporation, primarily utilizes convection and reflux heat transfer to heat oil shale formations. It consists mainly of a heating system and a production system. This technology employs a closed-loop circulation system, eliminating the injection of fluids into the formation, thus improving energy efficiency and reducing environmental impact. Chevron's Crush technology uses fluid convection heating, which first requires fracturing the shale formation, using high-temperature CO2 to heat the oil shale, and then extracting oil and gas products through vertical wells. However, the EGL technology has not yet addressed the dehydration issues before and during carbonization. The Crush technology may cause internal fractures in the heated oil shale to close more easily. Furthermore, both technologies suffer from significant heat loss during extraction, requiring substantial fuel reserves to achieve extraction goals.

[0009] Therefore, there is an urgent need to design an in-situ pyrolysis and modification method for preparing nanocatalysts downhole to solve the problems mentioned above. Summary of the Invention

[0010] The purpose of this invention is to provide an in-situ pyrolysis and upgrading method for preparing nano-catalysts downhole. This gas combustion heating system can use fluid to heat the formation and promote the pyrolysis of organic matter through catalysts. It is an in-situ pyrolysis and upgrading method for medium- and low-maturity shale oil and oil shale.

[0011] To achieve the above objectives, the present invention is implemented through the following technical solution: an in-situ pyrolysis and modification method for preparing nano-catalysts downhole, comprising the following steps: while heating the formation in a gas burner, a nano-catalyst precursor is fed into the gas burner. Under the high temperature conditions generated by the gas burner, the principle of generating nano-scale crystals by gas phase method is used to cause the nano-catalyst precursor to react and generate a nano-scale catalyst that can promote the conversion of organic matter in shale and medium-low maturity shale into light oil. The generated nano-scale catalyst is transported to the oil shale layer along with the exhaust gas generated by the gas burner, catalyzing the conversion of organic matter.

[0012] An apparatus for preparing nanocatalysts downhole includes a main shell, a mixing and inlet pipe, a casing, an igniter, a water collector, a drain pipe, a tail gas recovery pipe, a nanocatalyst precursor delivery pipe, a burner nozzle, and a flame monitoring electrode. The mixing and inlet pipe is located inside the main shell and is covered by a casing. A mixing and combustion chamber is enclosed between the main shell and the casing. An igniter is located inside the mixing and combustion chamber. A water collector is located at the top of the mixing and combustion chamber, and a drain pipe flows into the water collector. A burner nozzle is located at the bottom of the mixing and combustion chamber and is connected to the output end of the mixing and inlet pipe. The nanocatalyst precursor delivery pipe and the tail gas recovery pipe, which lead into the mixing and combustion chamber, are located inside the main shell.

[0013] Preferably, a flame monitoring electrode is provided inside the mixing combustion chamber.

[0014] This invention provides an in-situ pyrolysis and modification method for preparing nanocatalysts downhole. It has the following beneficial effects:

[0015] 1. This preparation method is an energy-saving heating method that can improve the energy utilization rate of medium- and low-maturity shale oil and oil shale, and reduce costs. The gas combustion heating system can use fluid to heat the formation and promote the pyrolysis of organic matter through catalysts. It is an in-situ cracking and upgrading method for medium- and low-maturity shale oil and oil shale. The catalyst particles prepared by the gas phase method are small and have good in-situ synthesis and carrying capacity, avoiding the use of water when carried by traditional fracturing fluid. Attached Figure Description

[0016] Figure 1 This is a schematic diagram of the structure of the present invention;

[0017] Figure 2 for Figure 1 Enlarged structural diagram at point A;

[0018] In the figure: 1 Main shell, 2 Mixing intake pipe, 3 Sleeve, 4 Mixing combustion chamber, 5 Igniter, 6 Water collector, 7 Drain pipe, 8 Exhaust gas recovery pipe, 9 Nano catalyst precursor delivery pipe, 10 Burner nozzle, 11 Flame monitoring electrode. Detailed Implementation

[0019] like Figures 1-2As shown, an in-situ pyrolysis and modification method for preparing nano-catalysts downhole includes the following steps: while heating the formation in a gas burner, a nano-catalyst precursor is fed into the gas burner. Under the high temperature conditions generated by the gas burner, the nano-catalyst precursor reacts to generate a nano-catalyst that can promote the conversion of organic matter in shale and medium- to low-maturity shale into light oil. The generated nano-catalyst is transported to the oil shale layer along with the exhaust gas generated by the gas burner to catalyze the conversion of organic matter.

[0020] An apparatus for preparing nanocatalysts downhole includes a main housing 1, a mixing and intake pipe 2, a casing 3, an igniter 5, a water collector 6, a drain pipe 7, a tail gas recovery pipe 8, a nanocatalyst precursor delivery pipe 9, a burner nozzle 10, and a flame monitoring electrode 11. The mixing and intake pipe 2 is located inside the main housing 1, and the casing 3 covers the outside of the mixing and intake pipe 2. A mixing and combustion chamber 4 is enclosed between the main housing 1 and the casing 3. The igniter 5 is located inside the mixing and combustion chamber 4. The water collector 6 is located at the top of the mixing and combustion chamber 4, and the drain pipe 7 flows into the water collector 6. The burner nozzle 10 is located at the bottom of the mixing and combustion chamber 4 and is connected to the output end of the mixing and intake pipe 2. The nanocatalyst precursor delivery pipe 9 and the tail gas recovery pipe 8 are located inside the main housing 1 and flow into the mixing and combustion chamber 4. The flame monitoring electrode 11 is installed inside the mixing and combustion chamber 4 to monitor the flame combustion.

[0021] In use, the device is lowered into the well via the drill pipe. The nanocatalyst precursor is introduced through the nanocatalyst precursor delivery pipe 9, and a mixture of gas and oxygen or air is introduced through the mixing air intake pipe 2. The igniter 5 ignites the gas, and the burner nozzle 10 begins to spray and heat the gas. Under the high temperature conditions generated by the gas burner, the nanocatalyst precursor reacts to generate nano-sized crystals using the principle of gas-phase generation, which promotes the conversion of organic matter in shale and medium- to low-maturity shale into light oil. The generated nano-sized catalyst is carried by the exhaust gas generated by the gas burner and discharged from the exhaust gas recovery pipe 8 along with the exhaust gas to the oil shale layer to catalyze the conversion of organic matter. The water generated in the mixing combustion chamber 4 is collected by the water collector 6 and discharged through the drain pipe 7.

Claims

1. A method for in-situ pyrolysis and modification of nanocatalysts prepared downhole, characterized in that, The system includes a main housing, an internal mixing intake pipe covered by a sleeve, and a mixing combustion chamber enclosed between the main housing and the sleeve. An igniter is located inside the mixing combustion chamber, a water collector is located at the top of the chamber with a drain pipe leading to it, and a burner nozzle is located at the bottom of the chamber, connected to the output end of the mixing intake pipe. An exhaust gas recovery pipe leading into the mixing combustion chamber is located within the main housing. The main housing also includes a nano-catalyst precursor delivery pipe that directly leads into the mixing combustion chamber. While the gas burner heats the formation, the nano-catalyst precursor is directly fed into the high-temperature region of the mixing and combustion chamber of the gas burner through the nano-catalyst precursor delivery pipe. Under the high-temperature combustion field conditions generated by the gas burner, nano-scale catalyst crystals are generated in situ through gas-phase reaction. This causes the nano-catalyst precursor to react and generate nano-scale catalysts that can promote the conversion of organic matter in shale and medium- to low-maturity shale into light oil. The generated nano-scale catalysts are transported to the oil shale layer along with the exhaust gas generated by the gas burner, achieving simultaneous heating and catalysis, and efficiently catalyzing the conversion of organic matter into light oil.

2. The method according to claim 1, characterized in that, A flame monitoring electrode is installed inside the mixing combustion chamber to monitor the combustion temperature, so as to ensure the stability of the temperature range of the gas-phase reaction of the nanocatalyst precursor.

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