Research on prevention technology and device of oil-gas disaster in the coal-oil-gas coexisting mine
1. Introduction
The oil-gas in surrounding rocks has become a new hidden disaster –inducing factor for the safe and efficient exploitation of coal-oil-gas coexisting mines. Taking the Ordos basin as an example, most of the main coal mining areas are the coal-oil-gas coexisting mines, and many abnormal and sudden oil-gas emerged from the surrounding rocks, which has posed a serious threat to the safe production of the mine. As the occurrence of oil-gas is different from coal seam gas and the gas mixed with oil-gas increases the explosion risk, its occurrence, emission, and prevention cannot be effectively solved by using existing theories and technical methods, and the difficulty of mine gas management increases and the situation is grim.
The photo of the oil-gas emerges from the mine floor（Huangling mining area）
1. Solution
The project takes Huangling mining area (Huangling No. 2 Coal Mine), which has serious oil-gas disaster in the Huanglong Jurassic coal field in Ordos basin, as the research object. The project used data collation and analysis, on-site detection and testing, indoor laboratory analysis, and numerical simulation. Also it comprehensively used the knowledge of oil and gas geology, coal geology, gas geology, mining engineering, geochemistry and so on. Through the research, a set of theoretical and technical systems for coal mine oil and gas exploration, prediction, and prevention have been formed; technologies and equipment for accurate and rapid coring of underground oil-gas exploration were integrated and innovated, and the pattern of distribution, occurrence, and gush of oil and gas reservoirs have been identified , the mechanism of oil and gas hazards has been revealed. A multi-factor coupling regional prediction technology for oil and gas occurrence and a quantitative analysis method for gas source in coal-oil-gas coexisting goaf were proposed, and three-dimensional comprehensive extraction technology of the long directional boreholes was created.
Work situation
Work content | workload | ||
| unit | Complete workload | ||
Data collection | Coal geological survey data, oil mine data, geology report, oil-gas outburst and measures data, shift report and journal | 260 | |
Record note | Oil and gas extraction data, pressure observation, inspection in the mine, journal etc. | 40 | |
Underground coring and drilling exploration project | Coring | 21 | |
Drilling length | meter | 1468 | |
Coring length | meter | 1402 | |
Core catalog | meter | 1402 | |
Ground survey project | Survey drilling | 6 | |
Geological drilling | meter | 3846 | |
Coring | meter | 624 | |
Geological catalog | meter | 3846 | |
| Mine test | 6 | ||
Directional drilling long three-dimensional drainage engineering | Length of coal seam hole | m | |
Length of rock formation | m | ||
Tight oil-gas reservoir anti-reflection project | Number of fracturing holes | ||
| Pumping pressure | |||
Tracking observation | Intensity data of oil-gas outburst | 560 | |
Data of oil-gas extraction | set | 480 | |
Sample collection and test analysis | Carbon isotope, hydrogen isotope, organic matter maturity, permeability, gas content, etc. | 1900 | |
Parameter test on site | Oil-gas pressure | 5 | |
| Natural gas emission of drilling oil | 5 | ||
| Coal seam gas pressure | 1 | ||
Influence radius of coal seam gas drainage | set | 3 | |
Influence radius of surrounding rock borehole gas drainage | set | 1 | |
Specific interpretation of 3D surface seismic data | km2 | 5.796 | |
2D underground seismic exploration | m | 1152 | |
Specific reinterpretation of surface oil well data | 9 | ||
Analytical material | Drawing | 223 | |
| Analytical form | 75 | ||
Underground working site and the observation and description of the cores
（1）Achieved accomplishment
Comprehensive regional prediction of oil and gas (gas) in the study area were made, and the occurrence of oil and gas in the study area was divided into levelⅠ, level Ⅱ, and level Ⅲ. The key areas for oil and gas prevention and control were pointed out, and the oil and gas defense area was reduced by 30%; 8.28km2 that cannot be mined due to oil- gas threats and 40 million tons of coal resources were liberated, and the output value increased by 12 billion yuan.
Simulation of thermal evolution history in Huangling area | Identification of oil and gas genesis |
(a)Oil and gas in the roof
(b)Oil and -gas in the floor
The division of comprehensive prediction of oil and gas in the roof and the floor of No. 2 coal seam
（2）Through the implementation of directional drilling layer optimization, drilling arrangement, and rock chip formation identification, breakthroughs in drilling depths of 770m for the top and bottom floors and 654m for coal seam hole were achieved, and the optimization technology of long directional boreholes and the technology of drilling operation were initially formed. The technology of three-dimensional comprehensive exploration and extraction of mine oil and gas through long directional boreholes was achieved.
Three-dimensional comprehensive extraction model of coal - oil - gas coexisting mine
（3）Through technical research and application, continuous mining operation is achieved to avoid the stop of the production and drivage caused by abnormal oil and gas emerge. The gas concentration in the return air flow at the heading face of Huangling No. 2 Coal Mine is below 0.25% and the oil and gas (gas) extraction rate up to 64%. The gas concentration in the air-return working face is lower than 0.6%, which provides the safe and efficient stoping of oil-gas outflow of the working face.
Comparison of fractured and unfractured boreholes before extraction and pressure relief drainage
（4）The project research formed a mature oil-gas treatment technology system, which effectively eliminated the oil-gas threat in coal mine production. With the development of the project and the continuous application of the results, Huangling No. 2 Coal Mine has achieved zero oil and gas (gas) overrun for 5 years, which ensured the miners’ life and the safe and efficient mine production .
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