scholarly journals Experimental Study on the Gas Flow Characteristics and Pressure Relief Gas Drainage Effect under Different Unloading Stress Paths

Geofluids ◽  
2020 ◽  
Vol 2020 ◽  
pp. 1-10 ◽  
Author(s):  
Chaolin Zhang ◽  
Jiang Xu ◽  
Enyuan Wang ◽  
Shoujian Peng
Keyword(s):  
Coal Seam ◽  
Gas Flow ◽  
Flow Characteristics ◽  
Gas Production ◽  
Gas Pressure ◽  
Coal Seam Gas ◽  
Pressure Relief ◽  
Gas Drainage ◽  
Coal Temperature ◽  
Drainage Effect

Coal seam gas is a critical substance because it can be a source of a large quantity of clean energy as well as a dangerous source of risk. A pressure relief gas drainage is an effective and widely used method for coal seam gas recovery and gas disaster control in coal mines. A series of pressure relief gas drainage experiments were conducted using large-scale coal samples under different unloading stress paths in this study to explore the unloading stress paths. From the experimental results, the dynamic evolutions of gas pressure, coal temperature, and gas production were analyzed. The trends of gas pressure and coal temperature during pressure relief gas drainage were similar: dropping rapidly first and then slowly with time. Correspondingly, gas production was fast in the early stage of pressure relief gas drainage and became stable thereafter. Meanwhile, gas flow characteristics were significantly affected by the unloading stress paths. Gas pressure and coal temperature had the maximum descent by unloading stress in three directions simultaneously, and the unloading stress of the Z direction had the minimal impact when only unloading in one direction of stress. However, the influence of unloading stress paths on gas production was complex and time dependent. The difference coefficient parameter was proposed to characterize the influence degree of unloading stress paths on the pressure relief gas drainage effect. Eventually, the selection of unloading stress path under different situations was discussed based on time, which is expected to provide the basis for pressure relief gas drainage.

Numerical Simulation on the Influence of Mining-Induced Fractures Field on Gas Drainage and its Application

2011 ◽  
Vol 90-93 ◽  
pp. 477-484
Author(s):  
Shu Jing Zhang ◽  
Yong Wei Peng ◽  
Yong Jiang Yu
Keyword(s):  
Numerical Simulation ◽  
Coal Seam ◽  
Gas Flow ◽  
Underground Mining ◽  
High Strength ◽  
Gas Pressure ◽  
Comsol Multiphysics ◽  
Coal Seam Gas ◽  
Gas Drainage ◽  
Induced Fractures

In order to study the influence of mining-induced fractures field on gas drainage,the paper adopts software of numerical simulation COMSOL Multiphysics to simulate gas drainage of coal seam under the condition of high-strength underground mining. The main aspects can be seen as the following: (1) In the case without considering the fractures, gas drainage in single hole, the gas pressure distribution showed a funnel-type distribution in space along the drainage holes around. (2) The orientation and direction of fractures play a major role on the flow field of gas. In the region that exits fractures, the distribution of gas pressure has a clear fluctuation and adjustment.(3) The numerical simulation of coal seam gas drainage that considered the fracture of coal mining, was closer to the true gas flow.

Case study of the effects on coal seam gas well production with installation of well head compression (oil-flooded rotary screw type): early outcomes of an Australian trial of four wells in the Bowen Basin

2017 ◽  
Vol 57 (2) ◽  
pp. 629
Author(s):  
Terrance Presley ◽  
Evilia Kurnia ◽  
Basia Wronski
Keyword(s):  
Coal Seam ◽  
Gas Flow ◽  
Lower Surface ◽  
Gas Production ◽  
Coal Seam Gas ◽  
Potential Wells ◽  
Energy Field ◽  
Operational Issues ◽  
Rotary Screw

This paper discusses the early outcomes of a trial of well head compression on coal seam gas (CSG) wells to lower surface pressure at the well head. This is a case study of four Johnson Controls Frick rotary screw compressor packages that were installed on CSG wells in an Origin Energy field in the Bowen basin and the early effects of lower well pressures on increased gas production due to the installation of compression. In mid-2016 Johnson Controls installed four compressor packages on Origin Energy wells with different characteristics (age, flow pressure), with a view of determining uplift of gas flow over the remaining life of the well, as well as operational issues with having well head compression. The expected versus actual uplift is compared for the different wells, with a view of providing some guidance on future potential wells that will benefit from this type of compression. Operational issues, such as effects on water flow, effect of oil and overall design considerations for well head compression, are also discussed.

scholarly journals Pressure Relief and Permeability Enhancement with Carbon Dioxide Phase Transition Blasting: Fracture, Seepage, and Practice

Lithosphere ◽  
2021 ◽  
Vol 2021 (Special 4) ◽  
Author(s):  
Zhongshun Chen ◽  
Yong Yuan ◽  
Wenmiao Wang ◽  
Cheng Zhu ◽  
Zhenghan Qin ◽  
...  
Keyword(s):  
Phase Transition ◽  
Carbon Dioxide ◽  
Gas Flow ◽  
High Energy ◽  
Gas Pressure ◽  
Coal Seams ◽  
Multiple Fractures ◽  
Pressure Relief ◽  
Permeability Enhancement ◽  
Drainage Effect

Abstract Coal seams are generally characterized by high pressure, low permeability, and strong adsorption in China. Moreover, carbon dioxide phase transition blasting (CDPTB) is an effective way to achieve pressure relief and permeability enhancement in high-gas pressure coal seams. Multiple fractures can be created in the coal body by CDPTB due to its characteristics of having a great impact stress and high energy efficiency. To determine the dual characteristics of coal fracturing and seepage after CDPTB, this paper developed a fluid solid coupling programme based on CDPTB cracking and permeability enhancement, which unifies the fracture and seepage of CDPTB. FLAC was used to determine the distribution characteristics of the stresses and fractures caused by CDPTB. The results showed fracture propagation from the initial fracture to multiple additional fractures or the main fractures over time. Then, the fractures were introduced into COMSOL software to simulate the characteristics of the gas flow field. The main fracture forms an effective channel for gas flow, which greatly reduces the gas pressure in coal. The successful application of CDPTB in the field induced the increase in the gas drainage effect by 10-20 times.

scholarly journals A numerical simulation on coal seam gas recovery from high temperature reservoir

2020 ◽  
Vol 24 (6 Part B) ◽  
pp. 3971-3978
Author(s):  
Teng Teng ◽  
Xiao-Yan Zhu ◽  
Xiang-Yang Zhang ◽  
Peng-Fei Chen ◽  
Yu-Ming Wang ◽  
...  
Keyword(s):  
High Temperature ◽  
Coal Seam ◽  
Mechanical Model ◽  
Gas Flow ◽  
Gas Production ◽  
Coal Seam Gas ◽  
Production Time ◽  
Gas Recovery ◽  
Coal Deformation ◽  
Fully Coupled

The coal seam gas recovery in deep reservoirs often meets high temperature. The change of temperature can greatly influence gas sorption, and couples heat transfer with coal deformation and gas-flow. This paper modifies the conventional Langmuir adsorption equation into a non-isothermal adsorption equation with a set of experimental data. After then, a fully coupled thermo-hydro-mechanical model of coal deformation, gas-flow and heat transfer is established. By using a finite element approach of COMSOL multi-physics, a numerical simulation of coal seam gas recovery from high temperature reservoir is subsequently implemented. The results show that the gas pressure and temperature decrease with production time and increase with the distance from production well, the reservoir permeability decreases with production time due to the compaction of increasing effective stress to coal fracture network, the cumulative gas production increases with production time exponentially whereas the production efficiency decreases negative exponentially, that the gas production in earlier 10 years accounts for 80% of the total production in 30 years. Our fully coupled thermo-hydro-mechanical model can improve the current understanding of coal seam gas recovery from high temperature reservoirs.

scholarly journals Study on gas drainage effect of hydraulic fracturing in soft coal seam

2020 ◽  
Vol 185 ◽  
pp. 01004
Author(s):  
Liangwei Li
Keyword(s):  
Coal Seam ◽  
Hydraulic Fracturing ◽  
Gas Flow ◽  
Water Injection ◽  
Fracture Initiation ◽  
Gas Content ◽  
Gas Drainage ◽  
Soft Coal ◽  
Drainage Effect ◽  
Soft Coal Seam

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.

scholarly journals Improvement and application of hole-sealing technology across seams in Song Zao coal mine

2018 ◽  
Vol 53 ◽  
pp. 02003
Author(s):  
Rili Yang ◽  
Xiaoxia Zhao ◽  
Lan Yu
Keyword(s):  
Coal Seam ◽  
Coal Mine ◽  
Field Conditions ◽  
Test Results ◽  
Pressure Relief ◽  
Gas Drainage ◽  
Working Face ◽  
Sealing Material ◽  
Drainage Effect ◽  
The Cost

Through the analysis on the drilling hole gas drainage effect(2225 working face crossing seam drainage, K2air way drilling field layout, crossing seam drainage gas in K3b coal seam),it is found that hole sealing technology directly affects gas drainage. Based on the original hole sealing technology and combining with field conditions, an improved drilling scheme for transportation roadway was proposed, considering the drilling layout, sealing material and depth, grouting time, pre-plunging depth. Test results of the scheme showed that, with a rise in the cost and drilling pressure relief time, the pressuring-relief gas drainage amount was greatly increased, the drilling field pre-pumping concentration was enhanced to 4.4times, the drainage efficiency was improved.

Analysis on Sealing Method and Sealing Materials of Gas Drainage Borehole

2013 ◽  
Vol 716 ◽  
pp. 485-489 ◽  
Author(s):  
Qing Ye ◽  
Zhen Zhen Jia ◽  
Yan Pi ◽  
Hai Zhen Wang
Keyword(s):  
Coal Seam ◽  
Gas Flow ◽  
Coal Mines ◽  
Polymer Foam ◽  
Gas Drainage ◽  
Rubber Ring ◽  
Advantages And Disadvantages ◽  
Materials Used ◽  
Drainage Effect ◽  
Sealing Materials

With the increase of gas drainage volume and gas drainage requirement of coal seam in China, more and more attention to gas drainage effect of coal seam is paid. The gas flow law and borehole sealing mechanism are briefly described, the borehole sealing technologies of different materials are analyzed and the requirements are obtained as follows: 1Sealing materials shall have permeability. 2Sealing materials shall have expansion. 3The strength and hardness of sealing material can not be too high. 4Sealing materials are compact; sealing materials shall have certain strength. 5Sealing materials can be obtained easily and their price shall be low. 6Sealing process is simple and is constructed easily. Finally, the high polymer foam sealing technology, the mechanical elastic sealing technology, borehole packer sealing technology, the new pressure grouting hole sealing technology, yellow clay borehole sealing technology and rubber ring (or capsule)-sealing fluid sealing technology are briefly analyzed, the advantages and disadvantages of the borehole sealing method and the sealing materials used in coal mines in China are summed up. The results can provides the reference for selection of borehole sealing methods and sealing materials of gas drainage in coal mines.

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

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.

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