WO2013026421A1

WO2013026421A1 - Underground coal gasification method

Info

Publication number: WO2013026421A1
Application number: PCT/CN2012/082067
Authority: WO
Inventors: 秦勇; 常文玖; 简伟
Original assignee: Qin Yong; Chang Wenjiu; Jian Wei
Priority date: 2011-08-19
Filing date: 2012-09-26
Publication date: 2013-02-28
Also published as: EP2843185A1; CN102287177A; EA201400149A1

Abstract

An underground coal gasification method. The method comprises disposing multiple injection wells (3) and gas collection wells (4) in a gasification operation zone; adding a catalyst and a propping agent into injection wells and gas collection wells by means of a fluid medium; fracturing and reforming the coal layer using a fracturing device to form large areas of fissures and cracks; forming gasification paths in the form of directional wells between the injection wells and gas collection wells; adding a gasification agent, a catalyst, and water through the injection wells to cause coal layer combustions and chemical reactions; collecting at the gas collection wells the gas produced by means of collection devices. The fissure paths between the wells formed by reforming large fractures, and the metal mineral particles used as a propping agent for the paths between wells effectively enable the maintenance of the effective communication in the injection well network for long durations; the metal mineral particles also function as a catalyst and an aggregating agent during gasification, thereby substantially enhancing the coal gasification volume.

Description

Method for underground coal gasification

Technical field

The invention relates to a method for gasification of underground coal, in particular to a gasification method of a coal seam located at a depth of 500 meters to several kilometers below ground.

Background technique

Underground coal gasification is a kind of energy collection method that directly controls the underground coal to be controlled to burn, and the crude syngas is output to the ground through the thermal action and chemical action of coal. It is a well-built well, coal mining and conversion process. As one of the coal development technologies, it is especially suitable for coal seams that cannot be mined or uneconomically produced by conventional methods, and secondary or multiple recovery of coal mines.

The underground coal gasification process requires that the coal seam has a strong gas permeability. However, the natural permeability of the coal seam is very poor, so it is necessary to pass through the gasification passage in the coal seam before the underground coal gasification operation. It is common practice to drill wells in several different directions around the gasifier injection well, then inject high pressure gas into the gasification injection well, observe the amount of gas removed from several wells around the gasification injection well, and select the largest exhaust gas. The direction of the connection between the well and the gasifier injection well is used as the direction of the gasification passage. At least three wells must be drilled by this method to roughly determine the gasification channel, and the cost is high. In addition, the gasification channel determined by this method is inefficient, and there is often a gasification channel that cannot be selected, and the gasification channel needs to be re-determined. The case of going through again.

In view of the above-mentioned problem of determining the cost of passing through the gasification passage and the low penetration efficiency, in CN1014241181A, a method and system for determining and penetrating underground coal gasification passages are disclosed, the method comprising: measuring the coal seam level Ground stress in the direction; determining the development direction of the coal seam crack according to the ground stress in the horizontal direction; determining the direction of the coal gasification channel according to the development direction of the coal seam crack. The defect of this method is to improve the underground gasification and penetration efficiency and save the penetration time. It is also necessary to install the underground gasification passage through device described in CN201802362U, and the gasification reaction area is small and the gasification efficiency is low.

In CN101586915B, a gasification pilot test gasification furnace for underground coal and a process method thereof are disclosed, the method comprising the gas supply system, the gasification furnace, the temperature measurement and pressure measurement component system, the high temperature camera system, the gas purification system. The gasifier shell is lined with refractory material. The gasifier and process are only suitable for use in the original coal mine roadway and cannot be used in coal seams located at a depth of 500m or even 2000m below the surface.

In the underground coal gasification process, the coal gas is first converted into products such as hydrogen and carbon monoxide, and then the synthesis gas is synthesized into methane under the action of a catalyst. Most commonly used catalysts are alkali metal catalysts, such as potassium carbonate, sodium carbonate, or polybasic alkali metal composite catalysts, such as potassium carbonate-sodium carbonate binary catalyst or potassium carbonate-sodium carbonate-lithium carbonate ternary catalyst. Large quantities, high cost, and the need to install recycling equipment for recycling and other issues.

Summary of the invention

In order to overcome the deficiencies of the prior art, the present invention provides a method for underground coal gasification, in particular, a gasification method for a coal seam located at a depth of less than 500 m underground. The method includes:

1. Determine the gasification operation area according to the survey results;

2. Set up several injection wells and gas production wells in the gasification operation area;

3. Forming a gasification channel between the injection well and the gas production well by means of a directional well (which may be a horizontal well or a inclined well);

4. Injecting a gasifying agent, a catalyst and water through the injection well to promote combustion of the coal seam and carry out a chemical reaction;

5. Recover the generated gas in the gas recovery well through the recovery unit.

The above gasification operation area may be more than 0.5 square kilometers, and an isolation area may be provided between the gasification operation areas; the separation area is more than 500 meters;

The distance between the injection well and the gas production well is between 150 meters and 500 meters. After the coalbed methane field is mined, the injection wells and gas production wells can be set up using the original well network to carry out underground coal gasification operations.

Before the directional drilling, the above-mentioned gasification channel uses a fracturing device to fracturing the coal seam, and injects a fluid medium into the injection well and the gas production well to add a catalyst and a proppant, and the injection pressure is greater than the fracture pressure of the formation to form a large The area cracks, together with the gasification channels formed by directional drilling, constitute a gasification channel system.

Smaller particles of catalyst and proppant may be injected into the cracks described above, such as particles having a diameter of 1-2 mm, in which larger particles of catalyst and proppant are injected into the gasification passage, such as particles having a diameter of 10-20 mm.

The above catalyst and proppant may be a substance such as metal ore particles, and it is preferred to select lower cost iron ore particles. The metal ore particles have both a catalytic action and a support for the gasification passage.

The above injection wells can be divided into gas injection wells, water injection wells, and water injection wells located between the gas injection wells and the gas production wells.

The above gasifying agent may be air or oxygen.

The above-mentioned gas injection wells, water injection wells and gas production wells can be arranged in a square queue, and the gas injection wells at the edge are arranged in sequence. In the mining project, after the initial gas injection well is burned, the injection well and the gas production well are gradually advanced with the combustion zone advancement. Converted to gas injection wells and water injection wells.

The above-mentioned gas injection wells, water injection wells and gas production wells may be arranged in queues of other shapes, such as plum-shaped piles, rings, and the like.

For the mining area with multiple coal seams, it is best to first mine the bottom coal seam and then, in turn, to the upper layer for mining.

The invention adopts a relatively closed underground coal seam as a whole gasification reaction vessel, and utilizes drilling engineering technology and new directional drilling, fracturing transformation and other engineering techniques as a coal seam transformation, injection and matching supporting technology, and changes the existing technology to a small area. The shortcomings of low displacement efficiency reflect the characteristics of mining technology with large area, high efficiency and high calorific value, so as to achieve efficient and comprehensive development of coal resources. The specific advantages are as follows:

1. The patented technology coal gas conversion process is completed underground, and will not cause environmental pollution caused by dust and toxic and harmful gases formed by traditional processes on the ground.

2. It is possible to develop coal resources that are difficult to exploit and use in deep burial (500-kilometres), so that the development of difficult-to-use coal resources can be effectively implemented, which will play a demonstration role in the comprehensive development of such coal resources in the future.

3. The invention adopts large-scale fracturing transformation to form primary and secondary fracture channels, and directional injection channels formed by directional drilling, that is, combined with the fluid medium, fracturing, orientation and other harvesting technologies used in the development of the mine field. It will form the largest ripple effect and displacement effect, which can transform coal resources to the greatest extent and avoid waste of resources.

4. The invention adopts the method of injecting water and oxygen in the underground coal seam, and the high-efficiency injection-production connecting well network utilized, and the coal-fired gas produced under the action of high temperature and high pressure is higher than the prior art. The combustion value has been greatly increased, which has played a good role in energy conservation and consumption reduction for resource utilization and downstream production.

5. In the invention, the coal fracture cracking transformation utilizes the inter-well crack channel formed by the large-scale fracturing transformation, and the metal mineral particles are used as the inter-well channel proppant, which can effectively maintain the long-term effective communication between the injection-production well networks, and the long-term large-area Scale mining plays a good production base; and metal mineral particles can play a catalytic polymerization role in the gasification process, which has a significant effect on increasing coal gas production.

6. The invention adopts a gasification channel as a gasification reaction zone, omitting a special gasifier equipment, and saving cost;

7. The invention separately injects a gasification agent and a water injection well by separately injecting a gasification agent and water, which is beneficial to the gasification reaction of the coal seam;

8. The invention has an isolation zone between the gasification operation zones, which effectively prevents the surface from collapsing due to gasification operations.

DRAWINGS

Figure 1 is a schematic view of a gasification working area and an isolation area of the present invention;

2 is a schematic view showing the distribution mode 1 of the injection well and the gas production well in the gasification operation area of the present invention;

3 is a schematic view showing the distribution mode 2 of the injection well and the gas production well in the gasification operation area of the present invention;

4 is a schematic view showing the distribution mode 3 of the injection well and the gas production well in the gasification operation area of the present invention;

Figure 5 is a schematic view of the gas injection well injection device of the present invention;

Figure 6 is a schematic view of the water injection well injection device of the present invention;

Figure 7 is a schematic view of a gasification passage between an injection well and a gas production well according to the present invention;

Figure 8 is a schematic view of the gas recovery well recovery device of the present invention;

Figure 9 is a flow chart of the ground recycling process of the present invention.

detailed description

Specific embodiments of the present invention will be further described in detail below with reference to the accompanying drawings.

Referring to Fig. 1, an isolation zone (2) is provided between the gasification operation zones (1) of the present invention, and an injection well (3) and a gas production well (4) are provided in the gasification operation zone. The width of the isolation zone is above 500m.

Referring to Figures 2 to 4, the injection well (3) of the present invention can be divided into a gas injection well (5) and a water injection well (6), respectively, and the water injection well (6) is located in the gas injection well (5) and the gas production well (4). between. The gas injection well (5), the water injection well (6) and the gas production well (4) may be arranged in a rectangular manner, and the gas injection well (5) located at the edge is arranged in sequence as a water injection well (6) and a gas production well (4), in the mining project. After the initial gas injection well (5) is burned, the injection well (6) and the gas production well (4) are gradually converted into a gas injection well (5) and a water injection well (6) as the combustion zone advances. The gas injection well (5), the water injection well (6) and the gas production well (4) may be arranged in a plum shape, ring shape or other manner.

Referring to Fig. 5, the gasifying agent of the present invention may be air or oxygen, which is passed through a gasifying agent gas injection line (7), a nozzle (8), and a casing (9) on the gas injection well (5). A gasification agent injection device composed of a tubing (10), a packer (11), a valve (12), and a single flow valve (13) is injected into the coal seam.

Referring to Figure 6, the present invention injects water into and near the coal seam combustion zone through a water injection device consisting of a casing (14), a fuel pipe (15), a valve (16), and a check valve (17).

Referring to Figure 7, a gasification passage is provided between the injection well and the gas production well of the present invention.

Referring to Figure 8, the gas produced by the present invention is recovered by a recovery unit consisting of a casing (18), a fuel pipe (19), a valve (20) and a check valve (21).

Referring to Fig. 9, the ground recycling treatment process of the present invention comprises underground mixing of a mixed fluid, separating gases, liquids and solids by means of three separation devices, and further processing by a water treatment device, a desulfurization and dust removal device, and the like.

Claims

1. A method of underground coal gasification comprising the provision of a plurality of injection wells and gas production wells in a gasification operation zone, characterized in that:

(1) forming a gasification passage between the injection well and the gas production well by directional wells;

(2) injecting a gasifying agent, a catalyst and water through the injection well to promote combustion of the coal seam and carry out a chemical reaction;

(3) Recovering the produced gas in the gas recovery well through the recovery unit.

2. A method of underground coal gasification according to claim 1, wherein said gasification passage adds catalyst and proppant to the injection well and the gas production well through the fluid medium before directional drilling, and utilizes pressure. The cracking device transforms the coal seam to form a large-area crack crack, and then forms a gasification passage system by a gasification passage formed by directional drilling.

3. A method of underground coal gasification according to claim 1 or 2, wherein a smaller particle catalyst and proppant are injected into said fracture crack, the particle diameter is 1-2 mm, in the gasification passage. The catalyst and proppant are injected with larger particles, and the particle diameter is 10-20 mm.

4. A method of underground coal gasification as claimed in claim 3 wherein said catalyst and proppant are metal ore particles.

5. A method of underground coal gasification as claimed in claim 4 wherein said metal ore particles are iron ore particles.

6. A method of underground coal gasification according to claim 1, wherein said gasification operation area has an area of more than 0.5 square kilometers, and an isolation area is provided between the gasification operation areas; More than 500 meters.

7. A method of underground coal gasification according to claim 1 or claim 6 wherein the distance between said injection well and the gas production well is between 150 and 500 meters.

8. A method of underground coal gasification according to claim 1, wherein said injection well is divided into a gas injection well and a water injection well, and the water injection well is located between the gas injection well and the gas production well.

9. A method of underground coal gasification according to claim 1 or claim 8 wherein said gasifying agent is air.

10. A method of underground coal gasification as claimed in claim 9 wherein said gasifying agent is oxygen.

11. A method of underground coal gasification according to claim 1, wherein said gas injection well, water injection well and gas production well are arranged in a square shape, and gas injection wells located at the edge are arranged in sequence, in the initial stage of mining. After the gas injection well is burned, the injection well and the gas production well are gradually converted into a gas injection well and a water injection well as the combustion zone advances.

12. A method of underground coal gasification according to claim 1, wherein said gas injection well, water injection well and gas production well are arranged in a plum pile shape.

13. A method of underground coal gasification according to claim 1 wherein said gas injection well, water injection well and gas production well are arranged in a ring.

14. A method of underground coal gasification as claimed in claim 1 wherein the multi-coal mining begins at the bottom and is subsequently carried out in an upward propulsion manner.