Gas Permeability Of Coal Seam Research Articles

Research on the Effective Scope of Low-permeability Hard Coalbed Coupling and Enhanced Permeability Technology

Due to poor gas permeability, high gas content, and hard coal quality at the JiuLiShan coal mine, gas extraction is difficult, and hydraulic perforation has limited effect. This study proposes a permeability enhancement method combining loosening blasting and hydraulic perforation to improve coal seam gas permeability and extraction efficiency. Field tests confirm the technology's effectiveness, showing that the combined method significantly enhances the coal body's permeability. The effective influence radius of the 1# test group (small explosives) is 4-6m, while the 2# test group (large explosives) extends this range to 6-8m, leading to a sustained increase in gas extraction. This approach offers an effective solution for enhancing permeability in complex coal mine conditions.

A high-precision and user-friendly triaxial apparatus for the measurement of permeability of gassy coal

The calculation method of coal seam gas permeability is the key starting point for studying a series of mine safety issues. However, the existing apparatuses are complex in operation, inconvenient in sample replacement, single in function, inaccurate in deformation measurement and poor in sealing effect. In this paper, a high-precision and user-friendly triaxial apparatus is developed. The apparatus consists of triaxial pressure and deformation measurement unit, gas filling and control unit, hydraulic loading unit and flow control and acquisition unit. The apparatus has excellent sealing performance and can accurately measure the axial and circumferential deformation of the sample simultaneously. In addition, the apparatus is user-friendly and integrated with the rapid replacement of the sample module. The permeability test of gassy coal in the whole process of deformation and failure is carried out and the results are consistent with previous research results, which proves the validity and reliability of the apparatus.

Progress on the hydraulic measures for grid slotting and fracking to enhance coal seam permeability

A method of hydraulic grid slotting and hydraulic fracturing was proposed to enhance the permeability of low permeability coal seam in China. Micro-structural development and strength characteristics of coal were analysed to set up the failure criterion of coal containing water and gas, which could describe the destruction rule of coal containing gas under the hydraulic measures more accurately. Based on the theory of transient flow and fluid grid, the numerical calculation model of turbulence formed by high pressure oscillating water jet was used. With the high speed photography test, dynamic evolution and pulsation characteristics of water jet water analysed which laid a foundation for mechanism analysis of rock damage under water jet. Wave equation of oscillating water jet slotting was established and the mechanism of coal damage by the impact stress wave under oscillation jet was revealed. These provide a new method to study the mechanism of porosity and crack damage under high pressure jet. Fracture criterion by jet slotting was established and mechanism of crack development controlled by crack zone between slots was found. The fractures were induced to extend along pre-set direction, instead of being controlled by original stress field. The model of gas migration through coal seams after the hydraulic measures for grid slotting and fracking was established. The key technology and equipment for grid slotting and fracking with high-pressure oscillating jet were developed and applied to coal mines in Chongqing and Henan in China. The results show that the gas permeability of coal seam is enhanced by three orders of magnitude, efficiency of roadway excavation and mining is improved by more than 57% and the cost of gas control is reduced by 50%.

Research on mechanism of quantity discharge of firedamp from coal drift of headwork surface reflect coal and gas outburst

The flow of gas in the coal bed is an extremely complex process, and the quantity of gas emission is mainly affected by both gas pressure in coal seam and permeability coefficient of coal seam. The influence factors of quantity discharge of firedamp from coal drift of headwork surface are analyzed, and the characteristics of discharge of firedamp from coal drift of headwork surface are closely related to the factors such as geological structure, gas content, gas pressure and permeability of coal seam. Not only the mathematical and physical model of one-way fluxion of discharge of firedamp from coal drift of headwork surface is established, but also the calculation formula of the quantity discharge of firedamp from coal drift is obtained by applying of variable separation method. According to the formula, the stagnation movement, which is among coal unloading pressure zone of stress, the stress concentration zone and original stress zone stress stagnation and the firedamp package of phenomenon, is analyzed in the coal and gas outburst mine. While the gas permeability of coal seam correspondingly changes variation, the quantity gas discharge also has the corresponding dynamic change. The results show that when the coal body in front of coal drift is in a non equilibrium state in the interaction among the horizontal crustal stress by gravity, gas pressure and mechanical properties of the coal, there is a risk of coal and gas outburst.

Seepage law and permeability calculation of coal gas based on Klinkenberg effect

Focused on the Klinkenberg effect on gas seepage, the independently developed triaxial experimental system of gas seepage was applied to conduct research on the seepage characteristics of coal seam gas. By means of experimental data analysis and theoretical derivation, a calculation method of coal seam gas permeability was proposed, which synthesized the respective influences of gas dynamic viscosity, compressibility factor and Klinkenberg effect. The study results show that the Klinkenberg effect has a significant influence on the coal seam gas seepage, the permeability estimated with the method considering the Klinkenberg effect is correct, and this permeability can fully reflect the true seepage state of the gas. For the gas around the standard conditions, the influences of dynamic viscosity and compressibility factor on the permeability may be ignored. For the gas deviating far away from the standard conditions, the influences of dynamic viscosity and compressibility factor on the permeability must be considered. The research results have certain guiding significance in forming a correct understanding of the Klinkenberg effect and selecting a more accurate calculation method for the permeability of coal containing gas.

Study on Pressure Sensitive Effect of Permeability of Raw Coal with Containing Gas and Low Permeability

Based on the low permeability raw coal samples of coal seams of Daichiba coal mine of Guangwang group, we study the change of permeability under different stress states by a self-developed three-axis penetration device. It is proved by experiments that the permeability of coal sample increases rapidly along with the growing of the pressure at the procedure of loading at lower actual stress levels whose rules of changes is the function of negative exponent. In the process of unloading, rate of permeability increase slowly with the reduction of effective stress. It will greatly improved when the effective stress drops to a certain level, and this conformed to power function law. As the influence of coal seam gas permeability solid coupling factors is very complex, the normalized treatment for the factors has done by defining pressure-sensitive effect coefficient of coal samples permeability. Based on the results of the test to establish the relationship between pressure sensitive effect index and effective stress, this relationship reflects the trend of the coal sample permeability changes in the effective stress. And derive a functional relationship based on the coal sample of the pressure-sensitive effect index of permeability and effective stress.

Study on Original Coal Seam Permeability Coefficient

In the case of gas radial flowing in layer-though boring, use the method of draining water gathering gas measured the Gas flow of borehole that there is water flow out from drilling Sometimes,the coal seam gas permeability coefficient is calculated using"Radial Flow Method"and"Optimizing Method,found out the range of 5-3 original coal seam Hongmiao coal mine permeability coefficient is0.007~0.008 m2/(MPa2·d).

New method to calculate coal-seam gas permeability. Technical note : Sun, P Min Sci TechnolV11, N1, July 1990, P101–105

New method to calculate coal-seam gas permeability. Technical note : Sun, P Min Sci TechnolV11, N1, July 1990, P101–105

A new method to calculate coal-seam gas permeability

Coal-seam gas permeability is one of the fundamental parameters in the study of coal gas dynamics and mine gases. A simple, rapid and accurate method is presented for the calculation and determination of the permeability.

地山炭層のガス透過率を評価するための一手法

There are practical and financial difficulties to measure gas permeability of coal seams. So we tried to evaluate gas permeability of a coal seam using permeabilities of small lump coal samples.From the results of measurement it was shown that; 1) Gas permeabilities of coal samples are distributed between very wide range, i.e. 10-7-100 darcy. 2) They fit to log-normal distribution. 3) In parallel or perpendicular direction of a seam, gas flow range has not significant difference.From the results it was unsuitable to estimate coal seam gas permeability by using arithmetic mean of these permeabilities. So we used two and three-dimensional model of coal seam consisted of random elements whose permeabilities are distributed as in samples. We made simulating calculation about gas flow in the model.Gas permeabilities of coal seams which were gained in this way are nearly same values with logarithmic means of sample permeabilities and showed good agreements with easiness of gas drainage in the colliery and values measured by other persons.