Gas injection apparatus with controllable gas injection point, gas injection process, and gasification method

Abstract

A gas injection apparatus with a controllable gas injection point, a gas injection process, and a gasification method. The gas injection apparatus comprises a directional well channel, where a continuous oil pipe is provided in the directional well channel. The continuous oil pipe is connected to an oxygen/oxygen-rich gas pipeline. An annular gap between the continuous oil pipe and the directional well channel is connected to an auxiliary gasification agent pipeline and a vapor pipeline. A gas injection wellhead is provided at the start end of the continuous oil pipe, and a nozzle is provided at the tail end. In the present invention, based on directional drilling and continuous oil pipe technologies, the movement of a gas injection point is implemented by using a manner of combining directional drilling and a continuous oil pipe; meanwhile, by using a principle of controlling reverse combustion by adjusting a gasification agent injection parameter, the movement of a working surface position and a combustion speed of a flame are regulated, so as to achieve the objective of ignition and gasification for reverse combustion of an underground coal layer.

1 . A gas injection apparatus with controllable gas injection point, which comprises directional well channel; the directional well channel is disposed with coiled tubing; the coiled tubing is connected with oxygen/oxygen-enriched gas line; the annular space between the coiled tubing and the directional well has connection to an auxiliary gasification agent line and a steam line; the start end of the coiled tubing is disposed with gas injection well head and the terminal end is disposed with nozzle. 
     
     
         2 . A gas injection process using the gas injection apparatus according to  claim 1 , wherein the oxygen/oxygen-enriched gas is delivered by the coiled tubing deposited within the directional well channel; the oxygen/oxygen-enriched gas, and auxiliary gasification agent delivered through the annular space between the coiled tubing and the directional well wall are uniformly mixed at the nozzle at the terminal end of the coiled tubing; the mixed gasification agent enters a predetermined gasification location of the coal seam through a directional well channel or pore channels within the coal seam. 
     
     
         3 . The gas injection process according to  claim 2 , wherein the directional well channel is formed by using directional drilling method; the directional drilling method preferably employ any of directional well technology, horizontal well drilling technology, lateral drilling technology, radial horizontal well technology, multilateral well technology, cluster wells technology and extended reach well technology in oil or coal-bed gas drilling technologies;
 preferably, the directional well channel is longer than 10 meters;   preferably, the pore channels within the coal seam is formed by using artificial drilling or fracturing process, or formed by coal seam under thermal effect of burning.   
     
     
         4 . The gas injection process according to  claim 2 , wherein the directional well channels are unsupported channel or supported channel;
 preferably, the supported channel employs sieve tube support and/or casing-tube support, more preferably sieve tube support or the combination of sieve-tube support and casing-tube support;   preferably, materials for the support tube are combustible material, more preferably organic materials, most preferably glass fiber reinforced plastics or PE pipe material;   preferably, the oxygen/oxygen-enriched gas is provided by the gasification agent production system; preferably, the oxygen-enriched gas is a mixed gas of oxygen with one or both of nitrogen and carbon dioxide, wherein the concentration by volume of oxygen is more than 21%;   preferably, the auxiliary gasification agent is one selected from nitrogen, carbon dioxide and water or the mixture thereof; preferably, the nitrogen is provided by the nitrogen production device; preferably, the carbon dioxide is provided by the decarbonization device.   
     
     
         5 . A gasification method with controllable gas injection point using the gas injection apparatus according to  claim 1 , wherein the gas injection point segmentally move to the predetermined gasification position by moving the coiled tubing at several times, then the gas injection process parameter is adjusted for reverse burning, gasification channel process and gasification production. 
     
     
         6 . The gasification method according to  claim 5 , which comprises the following steps:
 1) according to the parameters such as thickness and reserves of gasifiable coal seam in gasification area, segmentally moving coiled tubing according to the gas injection process to make the gas injection point position segmentally move to the predetermined gasification position;   2) adjusting the pressure and flow rate of a single gas and controlling the parameters such as flow rate, pressure and oxygen concentration of the injected gasification agent; segmentally moving the flame working face to the predetermined gasification position in the manner of reverse burning and making gasification channel process at the same time;   3) after completing the ignition and process of the gasification channel, improving intensity of the gasification agent injection, enhancing the gasification of underground coal and conducting gas production of underground gasification on a large scale;   4) when the coal seam gasification of the predetermined gasification position is done, determining stopping or reducing gasification agent injection according to the consumed amount of the gasification coal, and heat value and composition of coal gas, and starting the injector head to move the oxygen/oxygen-enriched gas injection point to the next predetermined gasification position;   5) conducting the next segment gasification channel process according to step 2), and completing the underground gasification of the predetermined coal seam area according to step 3) and 4); repeating those steps until the gasification mining of coal resource around the directional well channel is completed.   
     
     
         7 . The gasification method according to  claim 6 , wherein the distance traveled each time for the gas injection point is 10˜150 m;
 preferably, the flow rate of the gasification agent at the gasification channel ignition and processing is controlled within 300˜3000 m 3 /h; 
 preferably, the oxygen concentration by volume in the gasification agent is 21˜55%. 
 
     
     
         8 . A gasification method with controllable gas injection point using the gas injection apparatus according to  claim 1 , wherein the coiled tubing is continuously or intermittently lifted to make the gas injection point continuously move to the predetermined gasification position, then the gas injection process parameters are adjusted for reverse burning, gasification channel processing and gasification production. 
     
     
         9 . The gasification method according to  claim 8 , which comprises the following steps:
 1) according to the parameters such as thickness and reserves of gasifiable coal seam in gasification area, and continuously or intermittently lifting coiled tubing according to the gas injection process to make the gas injection point move to the predetermined gasification position;   2) adjusting the pressure and flow rate of a single gas and controlling the parameters such as flow rate, pressure and oxygen concentration of the injected gasification agent; achieving continuously processing gasification channel and gas production on a large scale in a manner of reverse burning.   3) adjusting the gasification agent injection parameters whenever necessary, to guarantee relative stable status of coal gas composition and heat value;   4) when the coal seam in the predetermined gasification area is gasified completely, controlling movement speed of coiled tubing according to burning speed of the flame, heat value and composition of coal gas, and the storage situation of the coal seam, until the coal resource around the directional well channel is gasified completely.   
     
     
         10 . The gasification method according to  claim 9 , wherein the flow rate of the gasification agent of step 2) is set to larger than 2000 m 3 /h; preferably, the oxygen concentration by volume of the gasification agent is 21˜95%;
 preferably, when the oxygen concentration by volume is more than 60%, water steam or water can be injected to adjust temperature and coal gas quality in the cavity.