WO2023078085A1 - 中低熟富有机质页岩自生热原位转化开发方法 - Google Patents

中低熟富有机质页岩自生热原位转化开发方法 Download PDF

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WO2023078085A1
WO2023078085A1 PCT/CN2022/126034 CN2022126034W WO2023078085A1 WO 2023078085 A1 WO2023078085 A1 WO 2023078085A1 CN 2022126034 W CN2022126034 W CN 2022126034W WO 2023078085 A1 WO2023078085 A1 WO 2023078085A1
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medium
rich shale
zone
self
organic
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PCT/CN2022/126034
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English (en)
French (fr)
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郭威
孙友宏
朱超凡
李强
邓孙华
王元
刘召
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吉林大学
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    • E—FIXED CONSTRUCTIONS
    • E21—EARTH OR ROCK DRILLING; MINING
    • E21C—MINING OR QUARRYING
    • E21C41/00—Methods of underground or surface mining; Layouts therefor
    • E21C41/16—Methods of underground mining; Layouts therefor
    • E21C41/24—Methods of underground mining; Layouts therefor for oil-bearing deposits
    • E—FIXED CONSTRUCTIONS
    • E21—EARTH OR ROCK DRILLING; MINING
    • E21B—EARTH OR ROCK DRILLING; OBTAINING OIL, GAS, WATER, SOLUBLE OR MELTABLE MATERIALS OR A SLURRY OF MINERALS FROM WELLS
    • E21B43/00—Methods or apparatus for obtaining oil, gas, water, soluble or meltable materials or a slurry of minerals from wells
    • E21B43/25—Methods for stimulating production
    • E21B43/26—Methods for stimulating production by forming crevices or fractures
    • E—FIXED CONSTRUCTIONS
    • E21—EARTH OR ROCK DRILLING; MINING
    • E21B—EARTH OR ROCK DRILLING; OBTAINING OIL, GAS, WATER, SOLUBLE OR MELTABLE MATERIALS OR A SLURRY OF MINERALS FROM WELLS
    • E21B43/00—Methods or apparatus for obtaining oil, gas, water, soluble or meltable materials or a slurry of minerals from wells
    • E21B43/295—Gasification of minerals, e.g. for producing mixtures of combustible gases
    • E—FIXED CONSTRUCTIONS
    • E21—EARTH OR ROCK DRILLING; MINING
    • E21B—EARTH OR ROCK DRILLING; OBTAINING OIL, GAS, WATER, SOLUBLE OR MELTABLE MATERIALS OR A SLURRY OF MINERALS FROM WELLS
    • E21B43/00—Methods or apparatus for obtaining oil, gas, water, soluble or meltable materials or a slurry of minerals from wells
    • E21B43/30—Specific pattern of wells, e.g. optimising the spacing of wells

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  • the invention belongs to the field of in-situ mining of medium-low maturity organic-rich shale, and specifically relates to an in-situ transformation and development method of medium-low maturity organic-rich shale by self-generated heat.
  • source rocks with a maturity of less than 1% are called medium-low maturity organic-rich shale, in which the retained liquid hydrocarbons account for less than 25% of the total oil generation, and more than 40% of the organic matter has not undergone thermal evolution of hydrocarbon generation. Dry distillation can obtain oil and gas products.
  • the medium-low maturity organic-rich shale with a maturity of less than 0.5% is called oil shale, and its retained liquid hydrocarbons are less than 10%.
  • China's low-mature organic-rich shale has great potential for in-situ conversion.
  • the technically recoverable oil resources are about 70-90 billion tons, and the natural gas resources are about 6-65x10.4 billion cubic meters.
  • the oil shale oil contained in oil shale The resources are about 47.644 billion tons. Although there are huge resources of medium-low maturity organic-rich shale in my country, only a small amount of oil shale less than 100 m deep can be developed through ground carbonization technology, and this technology is harmful to the environment.
  • the in-situ mining technology is a development method in which the solid kerogen inside the shale is cracked into oil and gas in situ by artificially heating the oil shale reservoir, and combined with the oil recovery process to extract it to the ground. This technology has not yet reached the level of industrial development, but when the technology is mature, it has the advantages of environmental protection, small footprint, low development cost and the ability to develop medium-deep shale resources. It is an important trend in the development of medium-low maturity organic-rich shale industry.
  • in-situ mining of medium-low maturity organic-rich shale is mainly realized through physical heating methods, including conduction heating technology, convective heating technology and radiation heating technology.
  • Conduction heating technology (refer to patent CN87100890) is the most mature in-situ conversion technology at present by setting a large number of high-power electric heaters in unfractured formations and heating the formations through slow heat conduction.
  • Mine tests have been successfully carried out in the Green River Basin of the United States and Jordan, and the energy-output-input ratio is about 3.1.
  • Convective heating technology injects fluids such as high-temperature water vapor, inert gas and supercritical CO 2 into the fractured formation, mainly convectively heating the formation through high-temperature fluid, and the heating speed is relatively fast.
  • Radiation heating technology (refer to patent application document CN106640010A) heats formation water through underground radio frequency transmitters, so that oil shale cracks to produce oil and gas, dissolves into near-critical water, and circulates to the surface through a circulation system. This technology has high heating efficiency and uniform heating. The speed is fast, the thermal inertia is small, the chemical reaction is catalytic, and the loss of heat is small during the transmission to the bottom of the well, but the downhole equipment is complex and the heating range is limited.
  • An underground open combustion convective heating method proposes to send gas and combustion-supporting gas into the well casing through pipelines respectively, and the mining After being mixed, it is burned in the downhole burner, and the high-pressure air isolates the flame to generate a mixed heating medium to heat the formation.
  • the heat source is in direct contact with the heated material, omitting the heat exchange process, and reducing the heat loss in the wellbore.
  • the solid carbon as a by-product, is reused in the form of waste heat after oil shale production ends.
  • a biochar-assisted method of heating oil shale to extract shale oil and gas proposes to inject a proppant mixed with a certain proportion of biochar and ignition agent into underground fractures along with the fracturing fluid during the fracturing process , and then use oil shale in-situ local chemical method to extract shale oil and gas.
  • the object of the present invention is to propose an in-situ transformation and development method of medium-low maturity organic-rich shale.
  • Local preheating is carried out near the injection well in the mature organic-rich shale formation, and normal-temperature air is injected into the preheated formation to stimulate and establish a chemical reaction zone consisting of a residue zone, a self-generating heat zone, a thermal cracking zone, and a preheating zone.
  • the residue produced by kerogen thermal cracking undergoes an oxidation reaction to release heat, which realizes convective heating of medium-low maturity organic-rich shale formations.
  • the oil and gas products generated by kerogen thermal cracking enter the production well through fractures and are lifted to the ground. Because the oil shale in-situ conversion technology only needs local preheating near the injection well, and only a small amount of external heat or combustible injection is required, its development cost is relatively low.
  • the present invention is realized through the following technical scheme: a method for in-situ conversion and development of medium-low maturity organic-rich shale by autogenous heat, which is characterized in that the method includes the following steps:
  • Step 1 Determine the target area for self-generated heat in-situ transformation and development of medium-low maturity organic-rich shale.
  • the oil content of rock formations is greater than 5%
  • the thickness of medium-low maturity organic-rich shale formations is greater than 15 meters
  • the water content of medium-low maturity organic-rich shale formations is less than 5%
  • the burial depth of medium-low maturity organic-rich shale formations is less than 3,000 meters;
  • Step 2 Arrange a development well pattern in the target area described in step 1.
  • the development well pattern adopts a reverse nine-point well pattern, and the ratio of injection wells to production wells in the well pattern is 3:1;
  • Step 3 Reservoir stimulation is carried out on the medium-low maturity organic-rich shale formation to form a fracture network, and the fracture-to-matrix permeability ratio is less than 10,000, and the fracture spacing is less than 0.5 meters;
  • Step 4 After reservoir stimulation, local preheating is carried out near the injection well in the medium-low maturity organic-rich shale formation, the preheating temperature reaches 300°C, and the preheating radius around the injection well reaches 2 meters;
  • Step 5 After preheating, inject normal temperature air into the injection well, control the bottom hole pressure of the injection well to be less than 20MPa, and ensure that the bottom hole pressure of the production well is the same as the formation fluid pressure.
  • the medium-low maturity organic-rich shale formation between the injection well and the production well forms a chemical reaction zone sequentially composed of a residue zone, a self-generating heat zone, a thermal cracking zone, and a preheating zone. Oxidation reaction of the residual residues releases heat, which realizes convective heating of low-mature organic-rich shale formations. Oil and gas products produced by kerogen thermal cracking enter production wells through fractures and are lifted to the ground.
  • medium-low maturity organic-rich shale formation is thicker than 50 meters, vertical wells are used; for the medium-low maturity organic-rich shale formation thickness is less than 50 meters, horizontal wells are used.
  • the reverse nine-point well pattern includes at least one well unit, and each well unit includes a production well located at the center of the rectangle, and an injection well located at the four vertices of the rectangle and the centers of the four sides of the rectangle.
  • the well spacing of the reverse nine-point well pattern is less than 50 meters.
  • step S3 the process of performing reservoir stimulation on the medium-low maturity organic-rich shale formation described in step S3 to form a fracture network is: sequentially adopt volume fracturing method and shock wave fracturing method to perform medium-low maturity organic-rich shale formation
  • the reservoir is stimulated to form a fracture network.
  • the preheating method for local preheating near the injection well of the medium-low maturity organic-rich shale formation is to inject high-temperature inert gas preheating, steam preheating, electric heating preheating or combustible gas injection Combustion and air mixture preheating, the preheating time is less than three days, therefore, only a small amount of external heat or combustible and air mixture injection is required, and its development cost is low.
  • the residue zone, self-generating heat zone, thermal cracking zone and preheating zone are divided according to the temperature profile and oxygen concentration difference during the advancing process of the reaction zone.
  • step 5 the air injection rate is greater than 140m 3 /(h ⁇ m), and the air injection time is until the temperature of the production well reaches normal temperature.
  • step 5 when the volume fraction of CO 2 in the production well is less than 5%, the air injection rate needs to be increased to 560m 3 /(h ⁇ m).
  • step 5 when the oil and gas products in the medium-low maturity organic-rich shale formation are blocked, high-temperature air over 300° C. is injected into the injection well to remove the plug.
  • the in-situ transformation and development method of low-mature organic-rich shale provided by the present invention has the following advantages:
  • the heat source required for heating the formation mainly comes from the shale itself, that is, the oxidative heat release of organic matter remaining after thermal cracking of kerogen, which has a low demand for external energy, so the energy utilization rate is high;
  • Fig. 1 is a schematic diagram of the in-situ transformation of authigenic heat of medium-low maturity organic-rich shale
  • Fig. 2 is a distribution map of well locations for authigenic heat in-situ conversion of medium-low maturity organic-rich shale
  • Fig. 3 is a diagram of the cumulative oil and gas production of medium-to-low maturity organic-rich shale in-situ conversion of self-generated heat;
  • Fig. 4 is a diagram of energy return rate for in-situ conversion of self-generated heat of medium-low maturity organic-rich shale
  • Fig. 5 is a self-generating reaction oil yield diagram under different air injection flow rates
  • Figure 6 is a diagram of the energy efficiency of self-generating heat reaction under different air injection flow rates
  • Fig. 7 (a) is the structural representation of the experimental device in the embodiment of the present invention 3.
  • Figure 7(b) is a cross-sectional view of the sample after the one-dimensional self-generating heat in situ conversion simulation reaction in Example 3 of the present invention.
  • Fig. 8 is a schematic diagram of the evolution of the temperature field of the one-dimensional self-generating heat in situ conversion in Example 3 of the present invention.
  • a self-generated heat in-situ conversion development method of medium-low maturity organic-rich shale mainly uses local preheating near the injection well 2 of medium-low maturity organic-rich shale formation with well-reformed reservoirs, and Inject normal-temperature air into the preheated formation to stimulate and establish a chemical reaction zone consisting of residue zone 3, self-heating zone 4, thermal cracking zone 5, and preheating zone 6, and oxidize residues generated after thermal cracking of kerogen The reaction releases heat to achieve convective heating of the low-mature organic-rich shale formation, and the oil and gas products produced by kerogen thermal cracking enter the production well 1 through fractures and are lifted to the ground.
  • Fig. 1 the schematic diagram of in-situ conversion of medium-low maturity organic-rich shale by autogenous heat.
  • the in-situ conversion and development method of self-generated heat of medium-low maturity organic-rich shale includes:
  • the hydrocarbon-generating potential, burial depth, thickness, and sealing of medium-low maturity organic-rich shale formations determine the oil yield and energy return rate of self-generating heat in-situ conversion technology. Fully understanding and selecting target blocks and formations is the key to medium-low maturity and rich shale formations.
  • the formation conditions of the target area are:
  • Vitrinite reflectance of low-mature organic-rich shale formations is less than 1;
  • the thickness of medium-low maturity organic-rich shale formation is greater than 15 meters;
  • the water content of medium-low maturity organic-rich shale formations is less than 5%;
  • the burial depth of medium-low maturity organic-rich shale is less than 3000 meters.
  • the stratum of the present invention has a wider scope of application, not only for low-maturity oil shale formations (vitrinite reflectance less than 0.5), but also for medium-maturity shale oil reservoirs (vitrinite reflectance of 0.5 -1).
  • the present invention does not need to completely drain the formation water, and the development upper limit of the formation water content is 5%, and the existence of a small amount of formation water is beneficial to heat transfer and kerogen catalytic pyrolysis.
  • wells In order to prevent the intrusion of formation water outside the target block and the loss of oil yield caused by the flow of oil and gas products outside the target block during the in-situ conversion of self-generated heat, wells should be deployed in the form of well groups.
  • the medium-low maturity organic-rich shale self-generated heat in-situ conversion development method is an inverted nine-point well pattern, see Figure 2, the well location distribution diagram of the medium-low maturity organic-rich shale self-generated heat in-situ conversion,
  • the reverse nine-point well pattern includes at least one well unit, and each well unit includes a production well 1 located at the center of a rectangle, and an injection well 2 located at the four vertices of the rectangle and the centers of the four sides of the rectangle.
  • the thickness of the medium-low maturity organic-rich shale formation is greater than 50 meters, vertical wells should be used, and if the thickness of the medium-low maturity organic-rich shale formation is less than 50 meters, horizontal wells should be used.
  • the interval between wells in the well group in the development method for self-generated heat in-situ conversion of medium-low maturity organic-rich shale is less than 50 meters.
  • the present invention adopts reverse nine-spot well pattern, and the ratio of injection and production wells is 3:1 to ensure sufficient air injection and displacement power, and to ensure the rapid advancement of the formation reaction area.
  • the in-situ transformation of medium-low maturity organic-rich shale proposed by the present invention preferably has a relatively large well spacing, and a single well group has a wide control range, reducing development costs.
  • Medium-low maturity organic-rich shale has extremely poor conductivity, so the formation needs to be fully stimulated before the in-situ transformation of self-generated heat, so as to ensure sufficient oxygen supply and smooth flow channels of oil and gas products.
  • the in-situ transformation of self-generated heat of medium-low maturity organic-rich shale has high requirements for reservoir stimulation, and there is a limit excitation compatibility relationship between fractures and matrix conductivity.
  • the medium-to-large flow rate of gas is quickly carried away, resulting in the inability of the matrix temperature to be maintained at the reaction temperature. Therefore, there is a threshold value for the extremely poor permeability between the fracture and the matrix.
  • the medium-to-low maturity organic-rich shale formation reservoir reconstruction sequentially performs volume fracturing and shock wave fracturing on the formation, and both the volume fracturing technology and the shock wave fracturing technology are existing methods of existing reservoir fracturing technology , belongs to the prior art, and the specific process of volume fracturing and shock wave fracturing will not be explained in detail here.
  • the fracture-to-matrix permeability ratio of the medium-low maturity organic-rich shale reservoir after reconstruction is less than 10,000.
  • the interval between fractures of the medium-low maturity organic-rich shale reservoir after reconstruction is less than 0.5 meters.
  • large-scale hydraulic fracturing i.e. large-scale volume fracturing
  • shock wave fracturing are used successively to form large cracks (crack openings greater than 1cm) and micro-fractures (fracture opening less than 1cm), forming multi-scale flow channels in the reservoir, reducing thermal short circuit and oil-gas displacement efficiency during in-situ conversion, and greatly improving formation oil yield.
  • the medium-to-low maturity organic-rich shale self-generated heat in-situ conversion formation preheating method includes: preheating by injecting high-temperature inert gas, steam, electric heating, and injecting combustible gas and air mixture for combustion preheating.
  • the preheating temperature near the wellbore 2 of the medium-low maturity organic-rich shale autogenerated heat in situ conversion reaches 300°C.
  • the preheating radius of the medium-to-low maturity organic-rich shale self-generating heat in situ conversion injection well 2 reaches 2 meters.
  • the present invention only needs 300°C and 2 meters for the formation preheating temperature and range, which reduces the external heat input in the early stage and reduces the development cost.
  • the thermal cracking zone 5 at the front end along the displacement direction has no oxygen to reach it, and only heat can reach it through convective heat transfer, so that the thermal cracking of kerogen produces oil and gas in an oxygen-free environment, while the residual carbon remains in solid form, which is self-generated heat
  • Zone 4 provides the heat generating donor for the oxidation reaction.
  • the thermal cracking temperature of kerogen is between 300-450°C, so the temperature in the thermal cracking zone 5 is generally within this temperature range, and there is a temperature range between room temperature and 300°C at the front edge of the thermal cracking zone 5, and no reaction occurs in this reaction zone.
  • the reaction only has a preheating effect on the formation, and this area becomes the preheating zone 6.
  • the kerogen residue zone 3 is the inorganic matter left after the carbon residue is completely oxidized. There is no heat generating donor in this zone, and no exothermic reaction can occur.
  • the bottom hole pressure of the injection well 2 is lower than 20 MPa for the self-generating heat in-situ transformation of the medium-low maturity organic-rich shale.
  • the pressure at the bottom of the production well 1 is the same as that of the formation fluid for self-generating heat in-situ conversion of the medium-low maturity organic-rich shale, so as to prevent the formation water from flowing out from the production well 1 .
  • the air injection rate of the medium-to-low maturity organic-rich shale into the injection well 2 is greater than 140 m 3 /(h ⁇ m).
  • the volume fraction of CO 2 in production well 1 is less than 5% for self-generating heat in-situ conversion of medium-low maturity organic-rich shale, and the air injection rate should be increased to 560m 3 /(h ⁇ m) to prevent the self-generating reaction from stopping underground.
  • the pressure of medium-low maturity organic-rich shale self-generated in situ conversion injection well 2 continues to rise, indicating that oil and gas products in the formation are clogged, and high-temperature air over 300°C needs to be injected to remove the clogging.
  • the anti-nine-point well group was selected as the development well pattern, including eight injection wells 2 and one production well 1.
  • the burial depth of the medium-low maturity organic-rich shale formation is 500 m, and the well spacing is 10 m.
  • Figure 2 shows. Due to the tightness of medium-low maturity shale formations and extremely poor conductivity, large-scale volume fracturing and shock wave fracturing must be performed on the formation before development. The spacing is 0.1m.
  • Nitrogen gas at 500°C was injected in the first stage of in-situ conversion of medium-low maturity organic-rich shale, with an injection rate of 1250m 3 /day and an injection time of 1 day.
  • the bottomhole pressure of production well 1 was controlled at 5MPa.
  • air at normal temperature is injected, and the injection flow rate is still 1250m 3 /day.
  • the injection time is until the temperature of production well 1 returns to normal temperature, and the bottomhole pressure of production well 1 is still controlled at 5MPa.
  • Fig. 3 shows the cumulative oil and gas production diagram of self-generated heat in-situ conversion of medium-low maturity organic-rich shale
  • Fig. 4 shows the energy return rate diagram of self-generated heat in-situ conversion of medium-low maturity organic-rich shale.
  • the oil shale formation conditions, reservoir stimulation and well pattern layout are the same as in Example 1.
  • 500°C nitrogen gas is injected, the injection flow rate is 1250m 3 /day, the injection time is 1 day, and the bottom hole pressure of production well 1 is controlled at 5MPa.
  • the injection flow rate is 1100m 3 /day, 1500m 3 /day, 2000m 3 /day, 4000m 3 /day respectively.
  • the injection time is until the temperature of production well 1 returns to normal temperature, and the bottom hole pressure of production well 1 is controlled Still 5MPa.
  • Figure 5 shows the oil yield diagram of medium-to-low maturity organic-rich shale autogenous heat reaction under different air injection rates
  • Figure 6 shows the energy efficiency diagram of medium-to-low maturity organic-rich shale self-generated heat reaction under different air injection rates .
  • the air inflow and outflow is 1100m 3 /day
  • the self-generating heat reaction cannot be triggered, and the oil yield and energy return rate are extremely low.
  • the flow rate exceeds 1100m 3 /day, the self-heating reaction is successfully triggered, but the oil yield does not increase with the increase of the injection flow rate, both are about 47%.
  • the energy return rate decreases with the increase of the injection flow rate. Since a larger injection flow rate requires a higher injection pressure, increasing the injection of external compression energy for in-situ conversion reduces the energy return rate for in-situ conversion of self-generated heat.
  • the present invention uses a one-dimensional self-generated heat in-situ conversion simulation device to carry out corresponding simulation experiments.
  • the suitable sample size of the simulation device is diameter 100mm, length 500mm, the radial direction of the sample is wrapped by a copper sleeve, the outside of the copper sleeve is filled with perlite for heat insulation treatment, the external pressure of the copper sleeve can be applied, and ten temperature measuring points are set inside the sample along the displacement direction for testing experiments
  • the internal temperature of the sample changes during the self-generated heat in situ conversion process, and the specific structure is shown in Figure 7(a).
  • the specific steps are as follows: First, select oil shale particles with a mass of 6.5 kg, 30-80 mesh, and an oil content of 14%, and press them into a sample with a diameter of 100 mm and a length of 500 mm through a custom-made device at a pressure of 14 MPa. During the prefabrication process, an internal temperature sensor containing ten temperature measurement points was pressed inside the sample under a pressure of 14MPa.
  • the sample is placed in the self-heating reaction holder (the specific shape and structure need to be given in detail here), the gas in the sample is exhausted through the vacuum pump, and the temperature of the preheater is set to 550 ° C, and the back pressure
  • the valve is set to 5MPa
  • the gas source of the booster pump is switched to nitrogen
  • the pressure is set to 10MPa
  • the flow controller is set to 5L/min.
  • Figure 7(b) shows the profile of the sample after the one-dimensional self-generating heat in situ conversion simulation reaction. After the reaction, the sample is divided into a residual area and an oxidation area.
  • the residual area is mainly inorganic minerals after residual carbon oxidation, and the color is relatively bright Light, while the oxidation zone is mainly composed of residual carbon that has not undergone oxidation reaction, and the color is darker.
  • Figure 8 shows the evolution of the one-dimensional self-generated heat in-situ conversion temperature field. The results show that after the sample end surface was preheated to 300°C for about 5 hours, and then injected with normal temperature air, the temperature of the sample end surface rose sharply, quickly reaching about 500°C, and The temperature gradually increased along the axial direction of the sample, and the local temperature once reached 650 °C, indicating that the oxidation reaction was successfully triggered and the entire sample was heated to the cracking temperature.

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Abstract

一种中低熟富有机质页岩自生热原位转化开发方法，属于中低熟富有机质页岩原位开采领域，该方法主要通过对储层改造良好的页岩地层注入井（2）附近进行局部预热，并向预热地层中注入常温空气，激发并建立起由残渣区（3）、自生热区（4）、热裂解区（5）和预热区（6）组成的化学反应区，利用干酪根热裂解后产生的残留物发生氧化反应释放热量，实现对流加热页岩地层，干酪根热裂解产生的油气产物通过裂缝进入生产井（1），并被举升至地面。由于该油页岩原位转化技术仅需对注入井（2）附近局部预热，无需外部热量或可燃物注入，其开发成本较低。

Description

中低熟富有机质页岩自生热原位转化开发方法 技术领域
本发明属于中低熟富有机质页岩原位开采领域，具体地，涉及一种中低熟富有机质页岩自生热原位转化开发方法。
背景技术
一般将成熟度小于1％的烃源岩称为中低熟富有机质页岩，其滞留液态烃类物质占总生油量少于25％，尚未进行生烃热演化的有机质超过40％，低温干馏可获得油气产物。其中，成熟度小于0.5％的中低熟富有机质页岩被称为油页岩，其滞留液态烃类物质少于10％。我国中低熟富有机质页岩原位转化潜力巨大，技术可采石油资源量约700-900亿吨，天然气资源量约60-65ⅹ10 4亿方，其中，油页岩中蕴含的油页岩油资源量约476.44亿吨。尽管我国中低熟富有机质页岩资源量巨大，但目前仅有少量100m以浅的油页岩可通过地面干馏技术开发，且该技术对环境危害较大。原位开采技术是通过人工加热油页岩储层，原位将页岩内部的固体干酪根裂解成油气，并结合采油工艺开采到地面的开发方式。该技术尚未达到工业化开发水平，但技术成熟后具有绿色环保、占地面积小、开发成本低和可开发中深层页岩资源等优势，是中低熟富有机质页岩工业发展的重要趋势。
按照热量来源和热量传递方式不同，中低熟富有机质页岩原位开采的实现主要通过物理加热方法，包括传导加热技术、对流加热技术和辐射加热技术。传导加热技术(参考专利CN87100890)通过在未压裂地层设置大量大功率电加热器，通过缓慢的热传导方式加热地层，是目前最成熟的原位转化技术，美国壳牌公司开发的小井距电加热技术，已在美国绿河盆地和约旦成功开展矿场试验，能量产出投入比约为3.1左右。对流加热技术(参考专利CN1676870，CN107387052B)将高温水蒸气、惰性气体和超临界CO 2等流体注入压裂过的地层，主要通过高温流体对流加热地层，加热速度较快。辐射加热技术(参考专利申请文件CN106640010A)通过地下射频发 射器加热地层水，使油页岩裂解产生油气，溶解到近临界水中，通过循环系统循环到地表，该技术加热效率高且加热均匀，加热速度快，热惯性小，对化学反应具有催化作用，热量向井底传输过程中损失小，但井下设备复杂，加热范围有限。
除此之外，化学加热技术也被应用到油页岩原位开采过程中，一种地下开放燃烧对流加热方法(参考专利CN105840162B)提出将燃气和助燃气体分别经管道送入井套内，开采区处，混合后在井下燃烧器中燃烧，高压空气隔离火焰，产生混合加热介质，加热地层，热源与被加热物质直接接触，省略热交换的过程，减少井筒热量损失。上述技术在矿场实践中或室内实验均已证明了可行性，但是其需要投入大量的外部热量或可燃气体，导致中低熟富有机质页岩原位经济开采经济性较差。与之类似，一种油页岩原位局部化学法提取页岩油气的方法(参考专利CN103790563B)提出将含氧气体与生产井回收的烃类气体加热后混合注入生产井，在油页岩层中形成局部化学反应，诱发局部的链式反应实现油页岩热裂解，生产油气。而固体碳作为一种副产品，在油页岩生产结束后，以余热形式二次利用。此外，一种生物炭辅助加热油页岩提取页岩油气的方法(参考专利CN109184649B)提出在压裂过程中将混有一定比例生物炭和引燃剂的支撑剂随压裂液注入地下裂缝中，再利用油页岩原位局部化学法提取页岩油气。
明显地，已有的技术中原位转化过程中通过注入烃类气体或者生物炭，利用其与氧气反应释放的热量加热低熟富有机质页岩地层，而干酪根热解产生的生物炭仅以余热形式二次利用，并未将固定碳中所蕴含的热值充分发挥。事实上，中低熟富有机质页岩加热至裂解温度后，干酪根大分子发生缩合反应，除了生成油气产物之外，超过40％干酪根转化为固体残碳。该固体产物生油潜力为0，但仍存在大量热值，在含氧气氛下点火可发生燃烧，可产生大量热量，常规的原位转化技术并未考虑该固体物质的作用，将其滞留在地层中，或仅以余热形式二次利用。但如果将其中热值充分利用，可大幅降低中低熟富有机质页岩原位转化外部能量和能源投入。同时，残碳转化为CO 2，提高固相孔渗性质，有利于油气产物的生成。
综上所述，变革中低熟富有机质页岩原位转化工艺，提高能量投入效率和油气最终收率是本领域亟待解决的问题。
发明内容
针对现有技术存在的上述问题，本发明的目的是提出了一种中低熟富有机质页岩自生热原位转化开发方法，该自生热原位开采方法主要通过对储层改造良好的中低熟富有机质页岩地层注入井附近进行局部预热，并向预热地层中注入常温空气，激发并建立起由残渣区、自生热区、热裂解区和预热区组成的化学反应区，利用干酪根热裂解后产生的残留物发生氧化反应释放热量，实现对流加热中低熟富有机质页岩地层，干酪根热裂解产生的油气产物通过裂缝进入生产井，并被举升至地面。由于该油页岩原位转化技术仅需对注入井附近局部预热，仅需少量外部热量或可燃物注入，其开发成本较低。
本发明通过以下技术方案实现：中低熟富有机质页岩自生热原位转化开发方法，其特征在于，所述方法包括如下步骤：
步骤1：确定中低熟富有机质页岩自生热原位转化开发目标区域，所述目标区域的地层条件为中低熟富有机质页岩地层镜质体反射率小于1、中低熟富有机质页岩地层含油率大于5％、中低熟富有机质页岩地层厚度大于15米、中低熟富有机质页岩地层含水率小于5％以及中低熟富有机质页岩地层埋深小于3000米；
步骤2：在步骤1所述的目标区域布置开发井网，所述开发井网采用反九点井网，井网注入井和生产井的比例为3:1；
步骤3：对中低熟富有机质页岩地层进行储层改造，形成裂缝网络，且裂缝与基质渗透率比值小于10000，裂缝间距小于0.5米；
步骤4：经储层改造后，对中低熟富有机质页岩地层注入井附近进行局部预热，预热温度达到300℃，以注入井为中心预热半径达到2米；
步骤5：预热后，向注入井中注入常温空气，控制注入井井底压力小于20MPa，同时确保生产井井底压力与地层流体压力相同，随着常温空气的注入，触发自生热反应，沿驱替方向，在注入井和生产井之间的中低熟富有机质页岩地层形成依次由残渣区、自生热区、热裂解区和预热区组成的化学反应区，利用干酪根热裂解后产生的残留物发生氧化反应释放热量，实现对流加热中低熟富有机质页岩地层，干酪根热裂解产生的油气产物通过 裂缝进入生产井，并被举升至地面。
进一步，所述中低熟富有机质页岩地层厚度大于50米，采用垂直井；中低熟富有机质页岩地层厚度小于50米，采用水平井。
进一步，所述反九点井网包括至少一个井单元，每个井单元包括位于矩形的中心位置的生产井，以及位于矩形的四个顶点位置和矩形的四个边中心位置上的注入井。
进一步，所述反九点井网的井间距小于50米。
进一步，步骤S3中所述的对中低熟富有机质页岩地层进行储层改造，形成裂缝网络的过程为：依次采用体积压裂方法和冲击波致裂方法对中低熟富有机质页岩地层进行储层改造，形成裂缝网络。
进一步，所述步骤4中，对中低熟富有机质页岩地层注入井附近进行局部预热的预热方法为注高温惰性气体预热、水蒸气预热、电加热预热或者是注可燃气体与空气混合物燃烧预热，预热时间小于三天，因此，仅需少量外部热量或可燃物与空气混合物注入，其开发成本较低。
进一步，所述残渣区、自生热区、热裂解区和预热区是根据反应区间向前推进过程中温度剖面和氧气浓度差异划分的。
其中，在自生热区全部氧气与残碳进行反应，沿驱替方向前端的热裂解区无氧气到达，仅有热量通过对流传热到达该区域，使干酪根在无氧环境下发生热裂解产生油气，而残碳以固态形式留下，为自生热区提供氧化反应生热供体；热裂解区温度在300-450℃之间；预热区温度介于室温与300℃的区间，预热能量来自于外部热量或可燃物与空气地下燃烧放热；残渣区是残碳完全氧化后剩余的无机物，该区域不存在生热供体，无法发生放热反应。
进一步，步骤5中，空气注入量大于140m 3/(h·m)，空气注入时间直至生产井温度至常温。
进一步，步骤5中，当生产井中CO 2体积分数小于5％，需将空气注入量增加至560m 3/(h·m)。
进一步，步骤5中，当中低熟富有机质页岩地层中油气产物发生堵塞时，向注入井中注入超过300℃高温空气进行解堵。
与传统的物理加热方式相比，本发明提供的中低熟富有机质页岩自生 热原位转化开发方法具有如下优势：
1、加热地层所需热源主要来自于页岩自身，即干酪根热裂解后残留的有机物氧化放热，对外部能量需求较低，故能量利用率较高；
2、原位开采过程存在气驱作用，故二次裂解作用较弱，热量传递较快；
3、自生热区全部氧气与残碳进行反应，自生热产物CO 2可降低油水的界面张力及黏度，故油收率高。
附图说明
此处的附图说明用来提供对本发明的进一步理解，构成本发明申请的一部分，本发明示意性实施例及其说明用于理解本发明，并不构成本发明的不当限定，在附图中：
图1是中低熟富有机质页岩自生热原位转化原理图；
图2是中低熟富有机质页岩自生热原位转化井位分布图；
图3是中低熟富有机质页岩自生热原位转化累计油气产量图；
图4是中低熟富有机质页岩自生热原位转化能量回报率图；
图5是不同空气注入流量下自生热反应油收率图；
图6是不同空气注入流量下自生热反应能量效率图；
图7(a)是本发明实施例3中的实验装置的结构示意图；
图7(b)是本发明实施例3中的一维自生热原位转化模拟反应后的样品的剖面图；和
图8是本发明实施例3中的一维自生热原位转化温度场演化的示意图。
图中：1-生产井；2-注入井；3-残渣区；4-自生热区；5-热裂解区；6-预热区。
具体实施方式
为使得本发明的目的、特征、优点能够更加的明显和易懂，下面结合本发明的实施例以及图1、图2、图3、图4、图5、图6，对本发明中的技术方案进行清楚完整地描述。显然，本发明不受下述实施例的限制，可根据本发明的技术方案与实际情况来确定具体的实施方式。为了避免混淆本发明的实质，公知的方法、过程和流程并没有详细叙述。
一种中低熟富有机质页岩自生热原位转化开发方法，该自生热原位开采方法主要通过对储层改造良好的中低熟富有机质页岩地层注入井2附近进行局部预热，并向预热地层中注入常温空气，激发并建立起由残渣区3、自生热区4、热裂解区5和预热区6组成的化学反应区，利用干酪根热裂解后产生的残留物发生氧化反应释放热量，实现对流加热中低熟富有机质页岩地层，干酪根热裂解产生的油气产物通过裂缝进入生产井1，并被举升至地面。如图1所示，中低熟富有机质页岩自生热原位转化原理图。
中低熟富有机质页岩自生热原位转化开发方法，包括：
确定中低熟富有机质页岩自生热原位转化开发目标区域；
中低熟富有机质页岩地层生烃潜力、埋深、厚度、封闭性决定自生热原位转化技术油收率和能量回报率，充分了解和优选目标区块和层位是进行中低熟富有机质页岩自生热原位转化的第一步。
所述目标区域的地层条件为：
中低熟富有机质页岩地层镜质体反射率小于1；
中低熟富有机质页岩地层含油率大于5％；
中低熟富有机质页岩地层厚度大于15米；
中低熟富有机质页岩地层含水率小于5％；
中低熟富有机质页岩地层埋深小于3000米。
与现有技术相比，采取上述措施具有以下优点：
1、本发明地层适用范围更广，不仅适用于低成熟度的油页岩地层(镜质体反射率小于0.5)，也适用于中成熟度的页岩油油藏(镜质体反射率0.5-1)。
2、本发明无需将地层水完全排空，地层含水率开发上限为5％，少量地层水存在有利于热量传递和干酪根催化热解。
自生热原位转化过程中为防止目标区块外部地层水的侵入，以及油气产物向目标区块之外流动所造成的油收率损失，应采用井组的方式进行布井。
优选地，所述中低熟富有机质页岩自生热原位转化开发方法中井组为反九点井网，详见图2，中低熟富有机质页岩自生热原位转化井位分布图，所述反九点井网包括至少一个井单元，每个井单元包括位于矩形的中心位 置的生产井1，以及位于矩形的四个顶点位置和矩形的四个边中心位置上的注入井2。
优选地，所述中低熟富有机质页岩地层厚度大于50米，应采用垂直井，中低熟富有机质页岩地层厚度小于50米，应采用水平井。
优选地，所述中低熟富有机质页岩自生热原位转化开发方法的井组中井间距小于50米。
与现有技术相比，采取上述措施具有以下优点：
1、本发明选用反九点井网，注采井比例为3:1，保证充足的空气注入和驱替动力，保证地层反应区域快速推进。
2、本发明所提出的中低熟富有机质页岩自生热原位转化优选井间距较大，单个井组控制范围广，降低开发成本。
中低熟富有机质页岩导流能力极差，在进行自生热原位转化前需对地层进行充分的储层改造，以保证充足的氧气供给和油气产物流动通道通畅。中低熟富有机质页岩自生热原位转化对储层改造要求较高，裂缝与基质导流能力存在极限激发配伍关系，当裂缝渗透率较大时，基质自生热反应产生的大量热量被裂缝中大流量的气体快速携带离开，导致基质温度无法持续维持在反应温度，因此裂缝与基质的渗透率极差存在阈值。
优选地，所述中低熟富有机质页岩地层储层改造依次对地层进行体积压裂和冲击波致裂，体积压裂技术和冲击波致裂技术均为现有储层压裂技术已有的方式，属于现有技术，此处不再详细解释体积压裂和冲击波致裂具体过程。
优选地，所述中低熟富有机质页岩地层储层改造后裂缝与基质渗透率比值小于10000。
优选地，所述中低熟富有机质页岩地层储层改造后裂缝间距小于0.5米。
与现有技术相比，采取上述措施具有以下优点：本发明储层改造中，先后使用大规模水力压裂(即大规模体积压裂)和冲击波致裂，分别形成大缝隙(裂缝开度大于1cm)和微裂缝(裂缝开度小于1cm)，在储层形成多尺度流动通道，降低原位转化过程中热短路和油气驱替效率，大幅提高地层油收率。
中低熟富有机质页岩地层自身发生低温氧化释放热量较少，需通过局部预热注入井2近井地带，将页岩中干酪根热裂解为油气产物和残碳，为自生热反应提供足够的生热供体。
优选地，所述中低熟富有机质页岩自生热原位转化地层预热方法包括：注高温惰性气体预热、水蒸气预热，电加热预热，注可燃气体与空气混合物燃烧预热。
优选地，所述中低熟富有机质页岩自生热原位转化注入井2近井地带预热温度达到300℃。
优选地，所述中低熟富有机质页岩自生热原位转化注入井2预热半径达到2米。
与现有技术相比，采取上述措施具有以下优点：本发明对地层预热温度和范围仅需300℃和2米，减少前期外部热量投入，减低开发成本。
向已预热的注入井2中定流量注入常温空气，触发自生热反应，根据反应区间向前推进过程中温度剖面和氧气浓度差异，地层中建立起由残渣区3、自生热区4、热裂解区5和预热区6组成的化学反应区，其中自生热区4是该技术的核心区域，全部氧气在该区域中与残碳进行剧烈放热反应，产生大量热量。沿驱替方向前端的热裂解区5无氧气到达，仅有热量可通过对流传热到达，使干酪根在无氧环境下发生热裂解产生油气，而残碳以固态形式留下，为自生热区4提供氧化反应生热供体。干酪根热裂解温度在300-450℃之间，因此热裂解区5温度普遍在该温度范围内，热裂解区5前缘存在一个温度介于室温与300℃的区间，该反应区域不发生任何反应，对地层仅存在预热作用，该区域成为预热区6。干酪根残渣区3是残碳完全氧化后剩余的无机物，该区域不存在生热供体，无法发生放热反应。
优选地，所述中低熟富有机质页岩自生热原位转化注入井2井底压力小于20MPa。
优选地，所述中低熟富有机质页岩自生热原位转化生产井1井底压力与地层流体压力相同，以防止地层水自生产井1流出。
优选地，所述中低熟富有机质页岩自生热原位转化注入井2空气注入量大于140m 3/(h·m)。
优选地，当中低熟富有机质页岩自生热原位转化生产井1中CO 2体积 分数小于5％，空气注入量应增加至560m 3/(h·m)，防止自生热反应在地下中止。
优选地，当中低熟富有机质页岩自生热原位转化注入井2压力持续升高，表明地层中油气产物发生堵塞，需注入超过300℃高温空气进行解堵。
实施例
实施例1
本实例选取中国松辽盆地优质页岩为研究对象，运用数值模拟方法对中低熟富有机质页岩自生热原位转化过程进行验证。目标页岩层位原始有效孔隙度为6.40％，平均TOC(总有机碳)为16.9％，地层原始状态100％被地层水填充，基岩的导热系数为1.21×10 5J/(m day℃)，基岩的比热容为1.50×10 6J/(m 3℃)。干酪根中碳元素质量分数和干酪根分子量分别为71％和14.7g/mol，页岩中干酪根孔隙度为22.2％，孔隙中干酪根浓度为6.34×10 4mol/m 3，该地层的总孔隙度为28.65％。
由于地层富有机质层厚度有限，选用反九点井组作为开发井网，包括八个注入井2和一个生产井1，中低熟富有机质页岩地层埋深为500m，井距为10m，如图2所示。由于中低熟页岩地层较为致密，导流能力极差，开发前需对地层进行大规模体积压裂和冲击波致裂，压裂产生的裂缝渗透率为100mDc，基质渗透率为0.01mDc，裂缝间距为0.1m。
中低熟富有机质页岩自生热原位转化第一阶段注入500℃氮气，注入流量为1250m 3/day，注入时间为1天，生产井1的井底压力控制在5MPa。第二阶段注入常温空气，注入流量仍为1250m 3/day，注入时间直至生产井1温度恢复至常温，生产井1的井底压力控制仍为5MPa。
中低熟富有机质页岩自生热反应在上述生产流程中被成功触发，温度场随时间稳定推进，局部温度达到1500℃。同时，干酪根不断转化为油气产物和生热供体，油气产物自生产井1不断产出，而生热供体滞留地层与后续氧气发生氧化反应，释放大量热量。图3示出了中低熟富有机质页岩自生热原位转化累计油气产量图，图4示出了中低熟富有机质页岩自生热原位转化能量回报率图。结果表明，随着自生热原位转化进度的进行，烃类气体、轻质油和重质油先后从生产井1产出。在第27天，轻质油和重质 油生产停止，在第80天，烃类气体生产停止，经计算该实例中最终总油收率达到50％，远高于常规油气田开发效果。原位转化另一个关键指标为能量回报率，在该实例中能量回报率在第18天达到最高值为4.75。
实施例2
与实施例1油页岩地层条件、储层改造和井网布置相同。自生热原位转化第一阶段注入500℃氮气，注入流量为1250m 3/day，注入时间为1天，生产井1的井底压力控制在5MPa。第二阶段注入常温空气，注入流量分别为1100m 3/day、1500m 3/day、2000m 3/day、4000m 3/day，注入时间直至生产井1温度恢复至常温，生产井1的井底压力控制仍为5MPa。
如图5所示为不同空气注入流量下中低熟富有机质页岩自生热反应油收率图，如图6所示为不同空气注入流量下中低熟富有机质页岩自生热反应能量效率图。当空气出入流量为1100m 3/day时，自生热反应无法触发，油收率和能量回报率均极低。当流量超过1100m 3/day时，自生热反应被成功触发，但油收率不随注入流量增加而增加，均为47％左右。能量回报率随着注入流量增加而降低，由于较大的注入流量需要较大的注入压力，增加原位转化外部压缩能注入，降低自生热原位转化能量回报率。
实施例3
为了研究本发明提供的中低熟富有机质页岩自生热原位转化开发方法的效果，本发明利用一维自生热原位转化模拟装置进行了相应的模拟实验，该模拟装置适用样品尺寸为直径100mm、长度500mm，样品径向被紫铜套包裹，紫铜套外部充填珍珠岩进行隔热处理，紫铜套外可施加围圧，同时样品内部沿驱替方向设置十个测温点，用以测试实验过程中自生热原位转化过程中样品内部温度变化，具体结构如图7(a)所示。
具体步骤为：首先，选取质量为6.5kg、30-80目、含油率14％的油页岩颗粒，通过定制装置以14MPa压力将其压制成直径为100mm、长度为500mm的样品，且在样品预制过程中将包含十个测温点的内部测温传感器在压力14MPa下压制在样品内部。其次，将该样品放置在自生热反应夹持器(此处需要详细给出具体的形状结构)中，通过真空泵将样品中的气体 排出，并将预热器温度设置为550℃，将回压阀设置为5MPa，增压泵气源切换为氮气，压力设置10MPa，流量控制器设置为5L/min。接着，向样品中注入550摄氏度高温氮气，经过2.5h内部温度传感器第一测温点温度达到300℃。最后，将增压泵气源切换为空气，注入常温空气，在样品内部触发自生热反应，建立起由残渣区-自生热区-裂解区-预热区组成的化学反应区。待样品内部温度降至室温，停止实验。如图7(b)所示为一维自生热原位转化模拟反应后样品剖面图，样品反应后整体分为残余区和氧化区，其中残余区主要为残碳氧化后的无机矿物，颜色较浅，而氧化区主要由未发生氧化反应的残余碳构成，颜色较深。如图8所示为一维自生热原位转化温度场演化，结果显示样品端面在5小时左右预热至300℃后，改注常温空气，样品端面温度陡然上升，快速达到500℃左右，并沿着样品轴向方向逐渐升温，局部温度一度达到650℃，说明氧化反应成功触发，并将整个样品加热至裂解温度。
显然，本发明的上述实施例仅仅是为清楚地说明本发明所作的举例，而并非是对本发明的实施方式的限定，对于所属领域的普通技术人员来说，在上述说明的基础上还可以做出其它不同形式的变化或变动，这里无法对所有的实施方式予以穷举，凡是属于本发明的技术方案所引伸出的显而易见的变化或变动仍处于本发明的保护范围之列。

Claims (10)

  1. 中低熟富有机质页岩自生热原位转化开发方法，其特征在于，所述方法包括如下步骤：
    步骤1：确定中低熟富有机质页岩自生热原位转化开发目标区域，所述目标区域的地层条件为中低熟富有机质页岩地层镜质体反射率小于1、中低熟富有机质页岩地层含油率大于5％、中低熟富有机质页岩地层厚度大于15米、中低熟富有机质页岩地层含水率小于5％以及中低熟富有机质页岩地层埋深小于3000米；
    步骤2：在步骤1所述的目标区域布置开发井网，所述开发井网采用反九点井网，井网注入井和生产井的比例为3:1；
    步骤3：对中低熟富有机质页岩地层进行储层改造，形成裂缝网络，且裂缝与基质渗透率比值小于10000，裂缝间距小于0.5米；
    步骤4：经储层改造后，对中低熟富有机质页岩地层注入井附近进行局部预热，预热温度达到300℃，以注入井为中心预热半径达到2米；
    步骤5：预热后，向注入井中注入常温空气，控制注入井井底压力小于20MPa，同时确保生产井井底压力与地层流体压力相同，随着常温空气的注入，触发自生热反应，沿驱替方向，在注入井和生产井之间的中低熟富有机质页岩地层形成依次由残渣区、自生热区、热裂解区和预热区组成的化学反应区，利用干酪根热裂解后产生的残留物发生氧化反应释放热量，实现对流加热中低熟富有机质页岩地层，干酪根热裂解产生的油气产物通过裂缝进入生产井，并被举升至地面。
  2. 根据权利要求1所述的中低熟富有机质页岩自生热原位转化开发方法，其特征在于：所述中低熟富有机质页岩地层厚度大于50米，采用垂直井；中低熟富有机质页岩地层厚度小于50米，采用水平井。
  3. 根据权利要求1所述的中低熟富有机质页岩自生热原位转化开发方法，其特征在于：所述反九点井网包括至少一个井单元，每个井单元包括位于矩形的中心位置的生产井，以及位于矩形的四个顶点位置和矩形的四 个边中心位置上的注入井。
  4. 根据权利要求1或3所述的中低熟富有机质页岩自生热原位转化开发方法，其特征在于：所述反九点井网的井间距小于50米。
  5. 根据权利要求1所述的中低熟富有机质页岩自生热原位转化开发方法，其特征在于：步骤S3中所述的对中低熟富有机质页岩地层进行储层改造，形成裂缝网络的过程为：依次采用体积压裂方法和冲击波致裂方法对中低熟富有机质页岩地层进行储层改造，形成裂缝网络。
  6. 根据权利要求1所述的中低熟富有机质页岩自生热原位转化开发方法，其特征在于：所述步骤4中，对中低熟富有机质页岩地层注入井附近进行局部预热的预热方法为注高温惰性气体预热、水蒸气预热、电加热预热或者是注可燃气体与空气混合物燃烧预热。
  7. 根据权利要求1所述的中低熟富有机质页岩自生热原位转化开发方法，其特征在于：所述残渣区、自生热区、热裂解区和预热区是根据反应区间向前推进过程中温度剖面和氧气浓度差异划分的；
    其中，在自生热区全部氧气与残碳进行反应，沿驱替方向前端的热裂解区无氧气到达，仅有热量通过对流传热到达该区域，使干酪根在无氧环境下发生热裂解产生油气，而残碳以固态形式留下，为自生热区提供氧化反应生热供体；热裂解区温度在300-450℃之间；预热区温度介于室温与300℃的区间，预热区不发生任何反应，对地层仅存在预热作用；残渣区是残碳完全氧化后剩余的无机物，该区域不存在生热供体，无法发生放热反应。
  8. 根据权利要求1所述的中低熟富有机质页岩自生热原位转化开发方法，其特征在于：步骤5中，空气注入量大于140m 3/(h·m)，空气注入时间直至生产井温度至常温。
  9. 根据权利要求1所述的中低熟富有机质页岩自生热原位转化开发方法，其特征在于：步骤5中，当生产井中CO 2体积分数小于5％，需将空气注入量增加至560m 3/(h·m)。
  10. 根据权利要求1所述的中低熟富有机质页岩自生热原位转化开发方法，其特征在于：步骤5中，当中低熟富有机质页岩地层中油气产物发生堵塞时，向注入井中注入超过300℃高温空气进行解堵。
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CN109736762A (zh) * 2019-03-22 2019-05-10 吉林大学 一种油页岩原位催化氧化法提取页岩油气的方法
CN113236210A (zh) * 2021-05-27 2021-08-10 吉林大学 一种油页岩复合加热原位开采系统及方法
CN114017032A (zh) * 2021-11-03 2022-02-08 吉林大学 中低熟富有机质页岩自生热原位转化开发方法

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