CN103790563B - A kind of oil shale in-situ topochemistry method extracts the method for shale oil gas - Google Patents

Abstract

The invention discloses a method for extracting shale oil and gas by in-situ local chemical method of oil shale. The method utilizes hot mixed gas to form a local chemical reaction zone in underground oil shale layer; during the whole process, injection and recovery are controlled The concentration of the hot mixed gas induces a series of "chain reactions". As the temperature of the reaction zone gradually increases and the scope gradually expands, the porosity and permeability of the oil shale layer continue to increase, and finally realize the chemical heat-enhanced reaction treatment 1. Gradually autocatalytically crack the oil shale layer from the inside to the outside to generate shale oil and fuel gas. After the chain reaction is over, continue to use the hot mixed gas to promote the reaction of fixed carbon in the rock formation to produce low calorific value gas, and recycle the high waste heat in the area where the cracking reaction is completed, so as to realize energy self-sufficiency and maximum utilization of oil shale cracking. The invention reduces mining costs, environmental hazards and business risks.

Description

A method for extracting shale oil and gas by in-situ local chemical method of oil shale

technical field

The invention relates to an oil shale mining technology, in particular to a method for extracting shale oil and gas by in-situ local chemical reaction of oil shale. Chemical reaction is used to crack the organic matter in oil shale to extract shale oil and fuel gas, and high waste heat is recycled to the area where the cracking reaction is completed. It is a method that can realize energy self-sufficiency and heat utilization rate maximization of in-situ cracking of oil shale. This technical method can be widely used in in-situ mining of solid or condensed mineral fuels (oil shale, coal, heavy oil).

Background technique

Over the past two decades, the global demand for energy has grown rapidly, and oil prices have repeatedly hit new highs. In 2012, the global consumption of crude oil reached 89.05 million barrels per day. The U.S. Energy Administration predicts that by 2030, the world’s crude oil production will reach its peak and then decline rapidly. By 2050, the recoverable crude oil will gradually exhausted. China's energy situation is more urgent, and the production capacity of major oil fields has begun to decline gradually. In 2012, the dependence on oil has reached 57%, which seriously threatens my country's energy security. Searching for alternative energy has become a top priority, and oil shale has become a key area of energy development in countries all over the world due to its huge reserves.

Oil shale is a solid combustible organic sedimentary rock with high mineral content. It contains immature organic matter-kerogen. After pyrolysis (low temperature dry distillation), oil shale oil and oil shale gas can be obtained. During the pyrolysis process, a series of physical and chemical reactions will occur. The bound water will be distilled at the initial stage of heating, and then the kerogen will be heated and converted into bitumen. The hot bitumen will be further decomposed into fuel gas of shale oil, and finally the residual organic matter and inorganic minerals will be gradually decomposed. How to control the physical and chemical reactions in the pyrolysis process to make the energy output and consumption ratio of oil shale pyrolysis most reasonable has become a key factor for technical feasibility.

At present, the technologies for extracting shale oil and gas from oil shale are mainly divided into two categories: surface carbonization technology and in-situ conversion technology. Surface carbonization technology has been widely used in Estonia, the United States, China, Canada and Brazil. However, there are many disadvantages in the production of shale oil by surface dry distillation: heavy excavation workload and high cost; easy to form gobs, leading to land subsidence; difficult to deal with a large amount of residue, large accumulation, easy to cause secondary pollution; discharge a large amount of waste gas and Sewage pollutes the environment greatly; water consumption is large, etc. Compared with the in-situ conversion technology, the underground pyrolysis mining of oil shale is realized by in-situ heating of the underground ore body, without damaging the surface, no goaf, and no waste residue accumulation on the surface, no pollution to the environment, and can be used It is a method to develop and utilize hydrocarbon-bearing solid mineral resources with broad prospects. At present, there are many methods for underground in-situ cracking of oil shale. The well-known Shell Underground Conversion Process (ICP) (Patent No. CN87100890) and ExxonMobil’s ElectrofracTM technology (Patent No. CN18975168A) both heat the underground oil shale layer in situ through conduction heating to realize the exploitation of shale oil and gas , this method needs to transport a large amount of heat to the ground, the heating speed is slow, it is easy to cause a large amount of heat loss, and the cost is high, and due to the thermal expansion of oil shale, some cracks are closed, which reduces the permeability of oil shale, resulting in The low oil and gas pressure leads to low oil and gas recovery rate (Reference: Natural Gas Industry, Volume 29, 2009, "Progress in In-Situ Exploitation Technology of Oil Shale in the World").

As early as the 1970s, the US patent "Shaleoil recovery process using heated oil-miscible fluids" (US Patent No. 3515213) applied by Michael Pats proposed to use hot volatile hydrocarbon steam circulation to heat the underground oil shale formation; in 2004, ExxonMobil applied for the patent " Recovery of hydrocarbons from impermeable oil shale" (Patent No. CN18975168A), proposed to use circulating fluid, mainly hydrocarbons or water or saturated water vapor as heat carrier to heat the oil shale layer; my country's Taiyuan University of Technology also proposed A method for recovering oil and gas by convectively heating oil shale is disclosed; patent CN1676870A discloses heating oil shale deposits by convective transmission of high-temperature superheated steam, and patent CN101122226A discloses using high-pressure and high-temperature hydrocarbon gas as a convective medium. However, these methods of convectively heating oil shale underground with high-temperature water vapor or hydrocarbon gas only use these high-temperature gases as heat carriers, and do not participate in the cracking reaction process of kerogen in oil shale. For porosity and permeability, high liquid injection pressure needs to be applied for a long time, and it is easy to form a short circuit of the fluid, that is, the fluid flow rate is too fast, and it will flow out of the formation without exchanging heat with the oil shale. Moreover, the heat capacity coefficient of water vapor is low, resulting in slow heating, large water consumption, and increased costs; high-temperature hydrocarbon gases have higher requirements for heating, injection equipment, and formation pipelines. In addition, Chevron applied for patent CN200780013312.4 in 2007, proposing to use normal temperature dense-phase fluid to cyclically pressurize and depressurize the injection well to achieve physical crushing and chemical modification of oil shale layers to extract kerogen-based products, among which The dense-phase fluid mainly uses CO ₂ . This method mainly increases the porosity and permeability of the formation through the pressure change and the thermal stress caused by the phase transition of CO ₂ . The cost is high and the technology is difficult.

At the same time, U.S. Patents 4,483,398, 4,552,214, and 4,703,798 disclosed the fire flooding method of burning underground oil shale layers to extract shale oil and gas; many domestic enterprises and universities have also proposed similar methods; The combustible gas and oxygen pipeline arranged in one of the wells transports the gas into the oil shale formation and ignites it at the mouth of the gas pipe to heat the oil shale formation, and the oil shale formation is fractured by pressurizing the two wells; Patent CN102383772A advocates igniting the oil shale layer through horizontal directional wells arranged at the bottom of the oil shale layer, and blowing oxygen-rich gas through different channels to realize forward, reverse and fixed-point gasification of the retorted oil shale layer. And the patents whose application numbers are 201310152389.7 and 201310152533.7 all use the heat generated by igniting the combustible gas and combustion-supporting gas transported underground as the heat source for dry distillation of underground oil shale formations. Although this kind of complete underground combustion can provide a large amount of heat for the cracking of kerogen in oil shale, it is a non-recoverable mining method, and the reaction process is not easy to control. If it is not properly controlled, a large amount of oil may be consumed shale or kerogen, thereby reducing the extraction rate of oil shale, and in addition, in a humid and relatively closed underground environment, there are higher requirements for ignition devices and media.

The above-mentioned underground in-situ oil shale mining methods all have disadvantages such as high cost, low efficiency, and large heat loss.

Contents of the invention

The purpose of the present invention is to provide a method for extracting shale oil and gas with high-efficiency cracking and energy self-balancing in-situ local chemical method of oil shale. The present invention uses hot mixed gas (specific hydrocarbon gas, nitrogen, carbon dioxide, water , oxygen, air, etc.) are injected into the underground oil shale layer to achieve in-situ extraction of shale oil and fuel gas, and the high waste heat in the area where the cracking reaction is completed is recycled. During the whole process, control the concentration of hot gas injected and recovered, as well as all parameters such as gas volume, temperature, pressure, chemical reaction, etc., and induce a series of "chain reactions" by gradually increasing the temperature, and finally realize chemical thermal strengthening Reaction processes, generates and extracts some of the oil and natural gas. This method is a self-catalytic in-situ conversion technology induced by local chemical reactions, which can realize energy self-sufficiency and maximum utilization of oil shale cracking.

The invention utilizes the hot mixed gas to form a local chemical reaction zone in the underground oil shale layer; by controlling and recovering the hot mixed gas injected into the underground oil shale layer and the fuel gas produced by the reaction, a local chain reaction is induced, and the As the temperature of the reaction zone increases gradually, the scope of the reaction zone gradually expands, and finally the oil shale is gradually autocatalytically cracked from the inside to the outside to generate shale oil and fuel gas. After the chain reaction is over, continue to use hot mixed gas to promote reactions such as fixed carbon in the rock formation to produce low calorific value gas, and use the waste heat for secondary use.

Concrete steps of the present invention are as follows:

1. Drill at least one heat injection well and one production well to the target oil shale formation, and form a hot mixed gas injection channel in the heat injection well; form a gas outflow channel and an oil pumping channel in the production well.

2. Inject 300-450°C hot mixed gas into the well through the injection channel of the heat injection well to initially heat the oil shale layer, so that the formation temperature in the local chemical reaction zone reaches 300-400°C; As the water evaporates, the pores of the rock begin to grow larger, providing channels for the migration of shale oil and fuel gas; kerogen is mainly decomposed into hot bitumen but adsorbed in the pores, and at the same time a small amount of hydrocarbon gas is generated and The produced hydrocarbon gases are separated;

3. As the temperature gradually rises, the mixed hot gas mixed with the separated hydrocarbon gas is introduced into the heat injection well. With the injection of the mixed gas, a chain chemical reaction occurs in the oil shale layer, and the reaction heat is released. , the temperature of the reaction zone reaches 500-600°C, the porosity and permeability of the oil shale layer continue to increase, the reaction zone continues to expand outwards, and finally realizes the chemical heat-enhanced reaction process, and the pyrolytic bitumen is further decomposed into a high-calorie hydrocarbon liquid state Compound and mixed gas, gradually autocatalytic cracking of oil shale formation from inside to outside;

4. Among them, the short-chain combustible gas is discharged from the gas outflow channel in the production well to the surface along with other reacted gases, part of which is used to heat the mixed gas on the surface after separation, and part of which is directly input into the heat injection well to participate in the circulation reaction;

5. After the chain reaction is completed, the temperature of the local chemical reaction area reaches 900-1200°C; at this time, the mixed gas such as hot air and water is introduced into the heat injection well to react with the fixed carbon in the oil shale to generate low calorific value Mixed gas of hydrogen and carbon monoxide;

6. During the reaction, the generated fuel gas is collected through the gas outflow channel of the production well, and the hydrocarbon liquid (shale oil) flows to the bottom of the well, and is pumped out from the oil pumping channel of the production well through a conventional oil production pump;

7. After all the local chemical reactions in the area are completed and the temperature of the rock mass reaches 1000°C, the mixed gas is injected into the heat injection well again, and the circulated hot mixed gas can be directly injected into the new heat injection well to form a chain of full utilization of oil shale energy .

The production wells are distributed in a triangle, a quadrangle, a hexagon or a circle with the heat injection well as the center.

The distance between the heat injection well and the production well and between the production well and the production well is 15-25m.

The heat injection well can increase the porosity of the oil shale formation in the reaction zone by blasting or fracturing, and use proppant to fill the cracks to improve the permeability of the oil shale formation; or directly use horizontal directional wells to connect injection Hot wells and production wells can establish oil and gas passages; horizontal wells and fracturing technology can also be used in combination to perform fracturing between two parallel horizontal wells to expand the area of the reaction zone, etc.;

If fracturing or horizontal well mode is used to increase the pores or channels in the reaction zone, the distance between the heat injection well and the production well is not limited by 15-25m.

Beneficial effects of the present invention:

The invention is a chemical heat strengthening treatment process. During the reaction process, the pores in the rock will continuously increase, and the scope will be gradually expanded, and the reaction is relatively thorough. Completed in the docked well group, the method has strong adaptability and has no requirements for the buried depth of the rock formation. It is suitable for oil shale reservoirs of various depths, greatly reduces the mining cost and commercial risk, and greatly improves the operability . It fundamentally solves the problems caused by surface dry distillation technology and existing in-situ technology, can effectively reduce construction difficulty and cost, and the method does not pollute ground water.

Description of drawings

Fig. 1 is a schematic diagram of the present invention.

Fig. 2 is a schematic diagram of the triangular distribution of the production wells of the present invention with the heat injection well as the center.

Fig. 3 is a schematic diagram of the production wells of the present invention distributed in a quadrilateral with the heat injection well as the center.

Fig. 4 is a schematic diagram showing that the production wells of the present invention are distributed in a hexagonal or circular shape with the heat injection well as the center.

In the figure: 1—heat injection well; 2—production well; 3—non-oil shale layer; 4—oil shale layer; 5—combustible gas; 6—burner; 7—heat exchanger; 8—oil, gas and water treatment device; 9—local chemical reaction zone;

detailed description

Example 1: As shown in Figure 1, it is a double well form, and the specific steps of this embodiment are as follows:

(1) Drilling and Completion:

a. Drill two wells, one well is the heat injection well 1, and the other well is the production well 2, and the distance between the boreholes of the two wells is 25m;

b. Drill two wells with the same technology, the hole diameter is 150mm, the hole diameter is 150mm from 0 to 65m, and a 146mm casing is installed; The direction points to another well, the well is cemented between the casing and the well wall, and the cement base is poured at the bottom of the well;

c. The two wells are connected through hydraulic fracturing fractures, and the production well and the heat injection well can be interchanged during the implementation process;

d. An injection channel should be formed in the heat injection well 1, and a gas outflow channel and an oil pumping channel should be formed in the production well 2;

(2) Equipment installation:

a. Install burners 6, heat exchangers 7, and oil, gas and water treatment devices 8 (including oil pumping equipment, separation equipment, condensing equipment) and corresponding pipelines and facilities on the ground;

b. Install measurement and control data cables along the well wall, and arrange pressure and temperature sensing devices at the bottom of the well;

c. Set up a pressure and temperature separation device in the separation part inside and outside the reaction area;

(3) Reaction stage:

a. Heat the mixed gas on the surface to 300-450°C through the burner 6 and the heat exchanger 7, and inject the hot mixed gas into the underground oil shale layer through the injection channel in the heat injection well 1; the gas injection pressure is lower than that of the overlying formation The self-weight pressure, the pressurized hot air passes through the fracturing channel in the oil shale reaction zone underground, slowly flows into the production well 2, until it is discharged to the surface; finally, the formation temperature in the local chemical reaction zone is heated to 300-400°C;

b. During this process, water will be evaporated, and the kerogen in the well wall layer in contact with the hot mixed gas flow and the oil shale inside the reaction zone will be thermally decomposed to generate hydrocarbon gas, light hydrocarbon components, and hot asphalt ; Increase the pore structure of the rock, but part of the liquid hot bitumen produced is still adsorbed in the pore structure;

c. The gas generated in the well reaches the ground through the gas outflow channel in the production well 2, and is separated;

d. According to a certain ratio, the mixed hot gas mixed with the separated hydrocarbon gas is introduced into the heat injection well 1. With the injection of the mixed gas, a chain chemical reaction occurs in the oil shale layer, and the reaction heat is released;

e. The temperature in the reaction zone reaches 500-600°C, the porosity and permeability of the oil shale layer continue to increase, and the zone temperature expands outward with the reaction;

f. At this time, the adsorbed hot asphalt generates high-calorie hydrocarbon gas;

g. After the chain reaction is completed, the temperature in the local chemical reaction area reaches 900-1200°C;

h. Then pass mixed gas such as hot air and water to the local chemical reaction area of oil shale, and chemically react with fixed carbon in oil shale and shale oil residue to produce low-calorie gas and sediment such as calcium sulfate (gypsum) .

k. Adjust the injection ratio and delivery pressure of hot gas and air in real time; the purpose is to control the reaction speed and temperature rise rate; real-time control the expansion rate of the reaction zone to prevent excessive carbon dioxide and sulfur dioxide in the gas, and reduce the sulfur content in shale oil Ingredients are kept to a minimum;

(4) Post-processing stage

a. The high-temperature gas carried out from the production well 2 in real time undergoes two-stage condensation and separation; first, it passes through the air-cooled heat exchanger for primary cooling, and separates the heavy oil through the gas-liquid separator; the remaining gas passes through the water-cooled heat exchanger Secondary cooling, and shale oil, water and gas are separated through the oil-water-gas three-phase separator, and the gas part is separated into pure fuel gas through the gas separator;

b. Part of the fuel gas is used for the downhole reaction cycle, part is used for the use of the burner, and part is stored or generated;

c. Use conventional oil production methods to pump the shale oil generated by the reaction and condensed at the bottom of the production well to the ground;

d. The oil is stored in the oil storage tank after a simple cooling and oil-water separation device;

e. The cracking reaction of this reaction well group ends, and the in-situ cracking of oil shale in the new area nearby begins. The mixed gas is passed into the heat injection well 1 of this well group, and after the gas passes through the oil shale reaction area, it comes out of the production well 2 and is heated to 400-450°C. This part of the hot mixed gas can be directly injected into the heat injection well 1 of the new well group to heat the oil shale in the new area.

Example 2: As shown in Figure 4, the group well mode, the specific steps of this embodiment are as follows:

a. According to the distribution and trend of the oil shale layer, select the specific locations of the heat injection wells and production wells, arrange 24 production wells 2 and 7 heat injection wells 1 in the delineated working area, and the plane distribution of the production wells 2 is 7 six 7 heat injection wells 1 are located in the middle of 7 hexagonally distributed production wells 2, the distance between adjacent production wells 2 and production wells 2 is 25m, and the distance between adjacent heat injection wells 1 and production wells 2 The distance is 25m;

b. The production wells 2 are distributed in a hexagon with the heat injection well 1 as the center;

c. Each heat injection well 1 and production well 2 are connected through hydraulic fracturing fractures;

d. A gas injection channel should be formed in the heat injection well 1, and a gas outflow channel and an oil pumping channel should be formed in the production well 2;

e. The implementation steps of equipment installation, local chemical reaction stage and post-processing stage are the same as (2) equipment installation, (3) reaction stage and (4) post-processing stage in the first embodiment.

Claims (4)

1. A method for extracting shale oil and gas by in-situ local chemical method of oil shale, the method utilizes hot mixed gas to form a local chemical reaction zone in the underground oil shale layer; The mixed gas and the fuel gas produced by the reaction induce a local chain reaction. As the temperature of the reaction zone gradually increases, the scope of the reaction zone gradually expands, and finally the oil shale is gradually autocatalytically cracked from the inside to the outside to generate shale oil. and fuel gas; after the chain reaction is over, continue to use the hot mixed gas to promote the fixed carbon reaction in the rock formation to produce low calorific value gas, and use the waste heat for secondary use; The concrete steps of this method are as follows: (1) At least one heat injection well and one production well are drilled to the target oil shale formation, and hot gas mixture injection channels are formed in the heat injection wells; gas outflow channels and oil pumping channels are formed in the production wells; (2) Inject the hot mixed gas at 300-450°C through the injection channel of the heat injection well into the well to initially heat the oil shale layer, so that the formation temperature in the local chemical reaction zone reaches 300-400°C; at this time, the oil shale Combined with the evaporation of water in the medium, the pores of the rock began to become larger, providing channels for the migration of shale oil and combustion gas; the kerogen was mainly decomposed into hot bitumen but adsorbed in the pores, and at the same time a small amount of hydrocarbon gas was generated. And the produced hydrocarbon gas is separated; (3) As the temperature gradually rises, the mixed hot gas mixed with the separated hydrocarbon gas is introduced into the hot injection well. With the injection of the mixed hot gas, a chain chemical reaction occurs in the oil shale layer, The heat of reaction is released, the temperature of the reaction area reaches 500-600 °C, the porosity and permeability of the oil shale layer continue to increase, the reaction area continues to expand outward, and finally realizes the chemical heat-enhanced reaction process, and the pyrolytic bitumen is further decomposed into high-heat Hydrocarbon liquid compounds and mixed gases gradually self-catalyze the cracking of oil shale formations from the inside to the outside; (4) Among them, the short-chain combustible gas is discharged from the gas outflow channel in the production well to the surface along with the gas, part of which is separated and used to heat the mixed gas on the surface, and part of which is directly input into the heat injection well to participate in the circulation reaction; (5) After the chain reaction is completed, the temperature of the local chemical reaction area reaches 900~1200°C; at this time, the mixed gas of hot air and water is introduced into the heat injection well to react with the fixed carbon in the oil shale to generate a low calorific value Mixed gas of hydrogen and carbon monoxide; (6) During the reaction, the generated fuel gas is collected through the gas outflow channel of the production well, and the hydrocarbon liquid flows to the bottom of the well, and is pumped out from the oil pumping channel of the production well through a conventional oil recovery pump; (7) After all local chemical reactions in the area are completed and the temperature of the rock mass reaches 1000°C, the mixed gas is injected into the heat injection well again, and the circulated hot mixed gas reaches 450°C, which can be directly injected into the new heat injection well to form oil Shale energy is fully utilized in the chain. 2. The method for extracting shale oil and gas by in-situ local chemical method of oil shale according to claim 1, characterized in that: the production well takes the heat injection well as the center and is triangular or quadrilateral or hexagonal or circular distribution. 3. the method for extracting shale oil and gas according to a kind of in-situ local chemical method of oil shale according to claim 1 or 2, characterized in that: the heat injection well and the production well and between the production well and the production well The distance is 15~25m. 4. A method for extracting shale oil and gas by in-situ local chemical method of oil shale according to claim 1, characterized in that: the method triggers a local chemical reaction in situ, and no longer requires external continuous delivery of high heat ; The generated combustion gas is used as reaction gas to expand the in-situ reaction zone, to heat the mixed gas, or to store or generate electricity.