CN-121630349-B - Underground in-situ gasification safe ignition method for high-gas coal seam coal

CN121630349BCN 121630349 BCN121630349 BCN 121630349BCN-121630349-B

Abstract

The invention relates to the technical field of underground in-situ gasification of coal, in particular to a safe ignition method for underground in-situ gasification of high-gas coal seam coal, which accurately divides ignition areas based on data such as trend length, width, coal seam thickness and the like of a gasification channel; meanwhile, the invention adopts a dual monitoring unit setting mode of an ignition area and a gas transmission direction to realize the non-blind area monitoring of the gasification channel, thereby not only meeting the regional monitoring requirement, but also guaranteeing the continuity and the accuracy of parameter acquisition and providing reliable data support for the follow-up pressure maintaining, purging and ignition point selection of the gasification channel. According to the invention, gas is introduced into the gasification channel for pressure maintaining treatment, so that the gas adsorbed in the coal seam cracks can be separated out and mixed with air, the distribution of the gas in the whole channel and a peripheral crack network is more uniform, and meanwhile, the gasification channel is purged after pressure maintaining is matched, so that the gas in the gasification channel can be rapidly discharged, and the gas discharge efficiency is increased.

Inventors

ZHOU ZE
WANG LINGXIA
YANG LEI

Assignees

贵州优驰能源科技有限责任公司

Dates

Publication Date: 20260508
Application Date: 20260203

Claims (8)

1. The underground in-situ gasification safe ignition method for the high-gas coal seam coal is characterized by comprising the following steps of: Injecting air into the gasification channel, and acquiring pressure maintaining parameters of each position through a plurality of monitoring units arranged in the gasification channel; Judging whether the gasification channel meets a stable pressure maintaining state or not based on the pressure maintaining parameters, and executing pressure maintaining treatment on the gas in the channel after the stable pressure maintaining state is met; After the pressure maintaining treatment is finished, introducing air into the gasification channel to purge, and acquiring the air pressure and the gas concentration of each position according to the monitoring time in the purging process; Based on the air pressure and the gas concentration analysis purge performance coefficient, judging whether to adjust the flow of the introduced air according to the purge performance coefficient, and stopping purging when the gas concentration at the air outlet of the gasification channel is lower than a safety standard; determining an ignition area according to arrangement parameters of the gasification channel, and equally dividing the ignition area into a plurality of subareas along the trend of the coal seam; acquiring working condition parameters of a gasification channel, comprehensively scoring each subarea based on the working condition parameters, and selecting the subarea with the highest score as an ignition point of underground in-situ gasification of the coal bed; the specific analysis mode of the purging performance coefficient is as follows: acquiring the air pressure and the gas concentration of each monitoring position at each monitoring moment; Carrying out gradient analysis on the gas concentration of each monitoring position and the gas concentration of the adjacent monitoring position to obtain gas gradient coefficients of each monitoring position, and carrying out mean value calculation on the gas gradient coefficients to obtain average gradient coefficients; Based on the air pressure analysis air pressure fluctuation value of each monitoring position, converting the air pressure fluctuation value into an air pressure influence coefficient between 0 and 1 through normalization processing, and obtaining an average air pressure influence coefficient through an average value calculation mode; performing linear weighted calculation on the average gradient coefficient and the average air pressure influence coefficient to obtain a purging performance coefficient; The judgment standard for stopping purging is as follows: Reading the gas concentration collected at the monitoring position close to the air outlet of the gasification channel, and analyzing the gas fluctuation rate at each monitoring moment; when the gas concentration monitored by the monitoring position is smaller than or equal to a safety standard, reading the gas fluctuation rate at a plurality of monitoring moments before, and obtaining a gas compensation rate through calculation; multiplying the gas safety standard value by the gas compensation rate to obtain a gas compensation quantity, and taking the difference value between the gas safety standard value and the gas compensation quantity as the final safety gas concentration; and stopping purging when the gas concentration monitored by the monitoring position is smaller than the final safe gas concentration.
2. The method for safely igniting the underground in-situ gasification of the high-gas coal seam coal according to claim 1, wherein the monitoring unit is arranged in the following manner: A monitoring unit is arranged in each sub-area of the ignition area; A plurality of monitoring units are uniformly arranged along the gas transmission direction of the gasification channel, and the monitoring units are used for monitoring pressure maintaining parameters of the set position, wherein the pressure maintaining parameters comprise gas pressure and gas concentration.
3. The method for safely igniting the underground in-situ gasification of the high-gas coal seam coal according to claim 1, wherein the judgment conditions for executing the pressure maintaining treatment on the gas in the gasification channel are as follows: Calculating absolute deviation of the pressure value and the mean value of each monitoring position, and taking the ratio of the absolute deviation and the mean value as the pressure deviation degree of the monitoring position; setting a pressure maintaining threshold range and a maximum allowable deviation degree of the gasification channel; when the pressure average value is in the range of the set pressure maintaining threshold value, and the pressure deviation degree of all the monitoring positions is smaller than or equal to the maximum allowable deviation degree, and the preset duration is continued, the gasification channel is judged to be in a proper pressure maintaining state, and the pressure of the gas in the gasification channel is maintained under the current pressure.
4. The method for safely igniting the underground in-situ gasification of the coal in the high-gas coal seam according to claim 3, wherein when the pressure deviation degree of each position exceeds a preset value, the leakage points of the gasification channel are required to be analyzed, and the specific analysis method is as follows: performing difference calculation on the real-time pressure value and the pressure average value of each monitoring unit to obtain pressure residual errors of each monitoring position; Counting all the pressure residual errors, screening out monitoring positions of which the residual error absolute values exceed a preset deviation threshold value, and marking the monitoring positions as pressure abnormality monitoring positions; Reading the space distribution position of the pressure anomaly monitoring position in the gasification channel, judging that a leakage channel exists from the starting monitoring position of the pressure anomaly monitoring position to the channel section corresponding to the ending monitoring position when the pressure residual error of the adjacent monitoring position of the pressure anomaly monitoring position shows a continuous increasing or decreasing trend, and marking the channel section as a pressure leakage area; and (3) scanning the pressure leakage area, determining the specific coordinates of the leakage point and the size of the leakage aperture, and plugging the leakage point by adopting plugging materials.
5. The method for safely igniting the underground in-situ gasification of the coal in the high-gas coal seam according to claim 1, wherein the judgment of whether to adjust the flow of the introduced air according to the purging performance coefficient is as follows: If the purging performance coefficient is greater than or equal to a set qualification threshold, judging that the purging effect is good, and maintaining the current air flow; if the purge performance coefficient is less than the pass threshold, then air is required to be up-regulated.
6. The method for safely igniting the underground in-situ gasification of the high-gas coal seam coal according to claim 1, wherein the specific analysis mode of the ignition area is as follows: Acquiring parameters of the trend length, the channel width and the coal seam thickness of the gasification channel; taking the midpoint of the trend length as the end boundary of the ignition region; Extending a preset safety distance inwards along the direction of the gasification channel by taking the air inlet of the gasification channel as a starting point, and taking an extension end point as a starting boundary of the ignition area, wherein the safety distance is comprehensively determined based on the channel width and the coal seam thickness; the gasification channel section between the start boundary and the end boundary is defined as an ignition region.
7. The underground in-situ gasification safe ignition method for the high-gas coal seam coal according to claim 1 is characterized in that parameters considered for comprehensively scoring each subarea based on the working condition parameters comprise curvature of a passage section where the subarea is located, inclination angle relative to a horizontal plane, distance from a gas injection point and coal seam geological conditions of the area, wherein the specific analysis modes are as follows: Reading the curvature radius of each subarea in the ignition area, screening the subarea with the maximum curvature radius, marking the curvature parameter of the subarea as 1, and marking the curvature parameter of the rest subareas as the ratio of the curvature radius of the corresponding subarea to the maximum curvature radius; reading the inclination of each subarea in the ignition area, screening each subarea with the inclination in the optimal inclination range, recording the inclination parameter as 1, and calculating the inclination parameters of the rest subareas in a mode of calculating the deviation degree of the inclination and the optimal inclination range, and taking the difference value between 1 and the deviation degree as the inclination parameter; Defining an area within a set range from the air inlet as an optimal mixing area, marking the position parameters of all subareas positioned in the optimal mixing area as 1, and determining the position parameters of the rest subareas by adopting an analysis mode of inclination parameters; and analyzing the curvature parameter, the inclination parameter and the position parameter of each subarea to obtain a comprehensive score.
8. The method for safely igniting the underground in-situ gasification of the high-gas coal seam coal according to claim 7, wherein the specific analysis mode of the ignition point is as follows: And the comprehensive scores of all the subareas are arranged in a descending order, and the subarea with the highest score is selected as an ignition point for in-situ gasification under the coal seam.

Description

Underground in-situ gasification safe ignition method for high-gas coal seam coal Technical Field The invention relates to the technical field of underground in-situ gasification of coal, in particular to a safe ignition method for underground in-situ gasification of high-gas coal seam coal. Background Underground in situ gasification of coal is a potential coal resource development, but implementation in high gas coal seams presents serious challenges. Because the high-gas coal seam has the characteristics of easy accumulation of gas, unbalanced pressure distribution, complex geological conditions and the like, the gas is required to be thoroughly discharged before the coal is ignited, so that the gas concentration is reduced to be within a safe range. The existing mode of setting negative pressure extraction is generally adopted to discharge gas from a coal seam, but a large number of cracks and pores exist in an underground in-situ environment, the gas is easy to gather and flow in the complex channels, and meanwhile, the gas is adsorbed in the cracks of the coal seam, so that the existing gas discharge time is long. In addition, the prior art has the defects that (1) the existing monitoring scheme is unreasonable to arrange, or only monitors a local area, or does not combine with the regional requirement of the ignition area, so that the monitoring blind areas exist in key parameters such as gas concentration, gas pressure and the like in the gasification channel. (2) The gas extraction process adopts single extraction pressure to extract gas, the mode easily enables the gas adsorbed in the coal seam cracks or gaps to be not fully extracted, the gas concentration is increased by the gas emission in the later period, and potential safety hazards are caused, meanwhile, whether the gas extraction is stopped is judged only through the single gas concentration, and the gas rebound risk is not considered. (3) The coal bed ignition point is determined empirically, and the structural parameters and the air flow characteristics of the gasification channel are not combined, so that an air flow disturbance area near an air inlet is not avoided, the ignition risk is easily increased due to gas accumulation or air flow fluctuation in the area, and meanwhile, the problems of uneven combustion propagation, low gasification efficiency and the like after ignition are not comprehensively considered due to the influence factors such as channel curvature, gradient, air mixing effect and the like. Disclosure of Invention In order to solve the technical problems, the invention adopts the following technical scheme that the underground in-situ gasification safe ignition method of the high-gas coal seam coal comprises the steps of injecting air into a gasification channel and acquiring pressure maintaining parameters of each position through a plurality of monitoring units arranged in the gasification channel. And judging whether the gasification channel meets a stable pressure maintaining state or not based on the pressure maintaining parameters, and executing pressure maintaining treatment on the gas in the channel after the stable pressure maintaining state is met. After the pressure maintaining treatment is finished, air is introduced into the gasification channel for purging, and the air pressure and the gas concentration of each position are obtained according to the monitoring time in the purging process. And analyzing the purging performance coefficient based on the air pressure and the gas concentration, judging whether to adjust the flow of the introduced air according to the purging performance coefficient, and stopping purging until the gas concentration at the air outlet of the gasification channel is lower than a safety standard. And determining an ignition area according to the arrangement parameters of the gasification channel, and equally dividing the ignition area into a plurality of subareas along the trend of the coal seam. And acquiring working condition parameters of the gasification channel, comprehensively scoring each subarea based on the working condition parameters, and selecting the subarea with the highest score as an ignition point of underground in-situ gasification of the coal seam. Further, the monitoring unit is arranged in a mode that a monitoring unit is arranged in each sub-area of the ignition area. A plurality of monitoring units are uniformly arranged along the gas transmission direction of the gasification channel. The monitoring unit is used for monitoring the air pressure and the gas concentration at the set position. Further, the judgment condition of the pressure maintaining treatment of the gas in the gasification channel is that in the process of injecting air in the gasification channel, the pressure value of each position is obtained in real time, the average value of the pressure values of each position is calculated, the pressure deviation degree of each position is analyzed,