Induced stress evolution of hydraulic fracturing in an inclined soft coal seam gas reservoir near a fault

Aiming at the difficulty of gas drainage by drilling along the seam in soft coal seam, the permeability of coal seam was increased by hydraulic fracturing test in the field, and the permeability and gas drainage parameters of coal seam before and after fracturing were studied. The results show that: ① The fracture initiation pressure of 3# coal seam in Guojiahe coal mine is 15~20MPa. When the water injection is 30~40m3, the fracturing radius is 15m, when the water injection is 50 ~ 60m3, the fracturing radius can reach 20m, when the water injection reaches 70m3, the fracturing radius can reach 30m; ② Driven by high pressure water, the gas in the fractured area migrates to the unfractured area, and the gas content in the fractured area decreases; ③ The attenuation coefficient of natural gas flow after fracturing is reduced by 50% compared with that before fracturing, and the permeability coefficient of coal seam after fracturing is increased by 50 times compared with that of original area; ④ The recovery concentration after fracturing is much higher than that before fracturing.

Download Full-text

Utilizing Current Technologies to Understand Permeability, Stress Azimuths and Magnitudes and their Impact on Hydraulic Fracturing Success in a Coal Seam Gas Reservoir

10.2118/133066-ms ◽

2010 ◽

Cited By ~ 11

Author(s):

Raymond L. Johnson ◽

Brent Glassborow ◽

Michael P. Scott ◽

Zachariah John Pallikathekathil ◽

Ashish Datey ◽

...

Keyword(s):

Coal Seam ◽

Hydraulic Fracturing ◽

Coal Seam Gas ◽

Gas Reservoir

Download Full-text

The Adaptation Analysis of the Fully Mechanized Coal Mining Face of Huopu Mine’s Third Soft Coal Seam

Advanced Materials Research ◽

10.4028/www.scientific.net/amr.1049-1050.335 ◽

2014 ◽

Vol 1049-1050 ◽

pp. 335-338 ◽

Cited By ~ 1

Author(s):

Fa Quan Liu ◽

Xue Wen Geng ◽

Yong Che ◽

Xiang Cui

Keyword(s):

Coal Seam ◽

Coal Mining ◽

Geological Condition ◽

Soft Coal ◽

Working Face ◽

Mining Face ◽

Soft Coal Seam ◽

Working Resistance

To get the maximum coal in front of the working face of the 17# coal seam, we installed a longer beam which is 1.2m in length in the leading end of the original working face supports ZF3000/17/28, and know that working face supports’ setting load and working resistance are lower .We changed the original supports with shield supports ZY3800/15/33 that are adaptable in the geological condition and got the favorable affection.

Download Full-text

Permeability Enhancement Properties of High-Pressure Abrasive Water Jet Flushing and Its Application in a Soft Coal Seam

Frontiers in Energy Research ◽

10.3389/fenrg.2021.679623 ◽

2021 ◽

Vol 9 ◽

Author(s):

Xinzhe Zhang ◽

Piotr Wiśniewski ◽

Sławomir Dykas ◽

Guojie Zhang

Keyword(s):

High Pressure ◽

Coal Seam ◽

Water Jet ◽

Gas Pressure ◽

Theory And Practice ◽

Abrasive Water Jet ◽

Gas Drainage ◽

Permeability Enhancement ◽

Soft Coal ◽

Soft Coal Seam

High-pressure abrasive water jet flushing (HPAWJF) is an effective method used to improve coal seam permeability. In this study, based on the theories of gas flow and coal deformation, a coupled gas-rock model is established to investigate realistic failure processes by introducing equations for the evolution of mesoscopic element damage along with coal mass deformation. Numerical simulation of the failure and pressure relief processes is carried out under different coal seam permeability and flushing length conditions. Distributions of the seepage and gas pressure fields of the realistic failure process are analyzed. The effects of flushing permeability enhancement in a soft coal seam on the gas drainage from boreholes are revealed by conducting a field experiment. Conclusions can be extracted that the gas pressure of the slotted soft coal seam is reduced and that the gas drainage volume is three times higher than that of a conventional borehole. Field tests demonstrate that the gas drainage effect of the soft coal seam is significantly improved and that tunneling speed is nearly doubled. The results obtained from this study can provide guidance to gas drainage in soft coal seams regarding the theory and practice application of the HPAWJF method.

Download Full-text

Research on Control of Rib Spalling Disaster in the Three-Soft Coal Seam

Shock and Vibration ◽

10.1155/2021/2404218 ◽

2021 ◽

Vol 2021 ◽

pp. 1-15

Author(s):

Feng Cui ◽

Tinghui Zhang ◽

Xiaoqiang Cheng

Keyword(s):

Coal Seam ◽

Field Experiments ◽

Simulation Experiment ◽

Current Status ◽

Soft Coal ◽

Grouting Pressure ◽

Working Face ◽

Coal Wall ◽

Soft Coal Seam ◽

Seam Mining

Rib spalling disaster at the coal mining faces severely restricted the safe and efficient output of coal resources. In order to solve this problem, based on the analysis of the current status of rib spalling in the three-soft coal seam 1508 Working Face of Heyang Coal Mine, a mechanical model of sliding-type rib spalling was established and the main influencing factors that affect rib spalling are given. The mechanism of grouting technology to prevent and control rib spalling has been theoretically analyzed. A similarity simulation experiment is used to analyze the change law of roof stress under the condition of three-soft coal seam mining. The optimal grouting pressure is determined by a numerical simulation experiment. And, silicate-modified polymer grouting reinforcement materials (SMPGMs) are used in field experiments. After twice grouting operations in the 1508 Working Face, the coal wall was changed from the original soft and extremely easy rib spalling to a straight coal wall and the amount of rib spalling has been reduced by 57.45% and 48.43, respectively. And, the mining height has increased by 0.16 m and 0.23 m, respectively. The experimental results show that the rib spalling disaster of the three-soft coal seam has been effectively controlled.

Download Full-text