ORCID Profile
0000-0001-7230-9849
Current Organisation
CSIRO
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Publisher: SPE
Date: 14-10-2022
DOI: 10.2118/210647-MS
Abstract: Horizontal boreholes have been routinely applied to coal seams as a cost-effective way to maximize coal seam gas production. However, these wells can encounter severe instability issues during field development due to significant horizontal stress loss and change in deviatoric stresses acting on the borehole. In this work, a general dual-porosity dual-permeability model is established and assigned to a coupled gas flow and coal deformation numerical model to investigate permeability change and borehole break-out regarding different in-situ stress regimes around a horizontal borehole. Mohr-Coulomb failure criterion is used in this model. The results show that drilling parallel to the maximum horizontal stress direction neither achieves the best stability of the borehole nor maximizes the permeability ratio. Drilling along the minimum horizontal stress direction would maximize the permeability ratio, but it has the worst stability. The optimal drilling direction window considering both permeability ratio and borehole stability is recommended to be between 45– 60°.
Publisher: Elsevier BV
Date: 09-2009
Publisher: Elsevier BV
Date: 10-2023
Publisher: Elsevier BV
Date: 10-2015
Publisher: Elsevier BV
Date: 04-2023
Publisher: Elsevier BV
Date: 09-2012
Publisher: Elsevier BV
Date: 11-2023
Publisher: Elsevier BV
Date: 03-2022
Publisher: Elsevier
Date: 2017
Publisher: American Chemical Society (ACS)
Date: 17-08-2022
Publisher: EAGE Publications BV
Date: 11-06-2018
Publisher: Elsevier BV
Date: 12-2021
Publisher: Elsevier BV
Date: 09-2015
Publisher: Elsevier BV
Date: 03-2019
Publisher: MDPI AG
Date: 27-04-2022
DOI: 10.3390/MIN12050543
Abstract: A thorough understanding of mining-induced overburden deformation characteristics and the associated stress redistributions are essential to effectively manage complex safety and environmental issues that arise from underground mining. This is particular for mining in deep environments. This paper presents a numerical modelling study on a kilometer-deep longwall coal mine where a thick sandstone aquifer is situated approximately 200 m above the working seam. The mine adopts a special mine layout with narrow and wide pillars between longwalls and areas to manage water inrush and coal burst risks. The modelling results show that overburden deformation stops at a certain height, above which the displacement profile over multiple longwall panels become nearly flat. Increasing panel width and extraction height lead to a greater extent of the fractured zone and a larger magnitude of surface subsidence. An extraction height of more than 7 m may breach the thick aquifer. Stress concentration on the wide pillar can undergo up to 5 times increase in the in-situ stress, posing high risks of coal burst. Adjusting mining parameters such as panel width and extraction height can facilitate an effective strategy to minimize water inrush and coal burst risks in such a mining condition.
Publisher: Elsevier BV
Date: 10-2015
Publisher: Elsevier BV
Date: 02-2016
Publisher: Elsevier BV
Date: 09-2022
Publisher: Elsevier BV
Date: 2020
Publisher: MDPI AG
Date: 10-04-2022
DOI: 10.3390/MIN12040463
Abstract: The dynamics of stress, deformation and pore pressure in the surrounding strata of underground mines are of fundamental importance to groundwater and gas emission management. Compared to numerous studies on the overlying strata, there are significantly fewer investigations concerning the underlying strata, particularly involving large-scale field monitoring. This paper presents a comprehensive field monitoring study conducted at two longwall panels with a depth of around 800 m and an inclination angle of 21°. The monitoring program focused on the floor strata within 50 m below the mining operation, but also covered the roof strata close to the longwall roadway. The purpose was to characterise the favourable zone for gas extraction from the floor coal seams. A combination of stressmeters, extensometers and piezometers were deployed and installed underground. The monitored results demonstrated that the stress change exhibited a three-stage variation—increase, decrease and recovery—during which the strata deformed and the pore pressure changed correspondingly. Strata expansion in the floor occurred primarily in the region 0–35 m behind the longwall face and vertically to at least 42 m below. Some predictive methods of the depth of the failure zone used in shallow mines were analysed to determine if they were still applicable for mining at a depth of around 800 m.
Publisher: MDPI AG
Date: 23-05-2022
DOI: 10.3390/EN15103828
Abstract: Coal seam permeability is a critical factor in coal seam gas extraction and gas outburst control. In Australian coal mines, coal seam permeability is normally estimated using a packer test or drill stem test. In contrast, Chinese coal mines generally estimate a parameter called the “gas conductivity coefficient” by measuring natural gas flow rates from an underground borehole drilled through a coal seam. With this method, it has been frequently reported that the permeability of many Chinese coal seams is between 0.0001 mD and 0.01 mD, which is extremely low compared to that of Australian coal seams (1–100 mD). It is therefore natural to wonder how closely the Chinese method measures permeability. Resolving this question will allow knowledge and experience in outburst management to be shared between Australian and Chinese coal mines. This question is investigated by the numerical modelling of gas desorption and flow through a seam of known permeability and by using the model’s borehole gas flow rate to estimate the permeability using the Chinese method. A total of 126 simulations were run with various input reservoir parameters. The results suggest that the Chinese method estimates permeability at an accuracy of 85% to 100%, which is adequate for mine pre-drainage design and outburst control. For the high diffusion rate (e.g., high gas content and short desorption time) and low Darcy flow rates (e.g., low permeability), these errors are reduced.
Publisher: Elsevier BV
Date: 09-2016
Location: Australia
No related grants have been discovered for Qingdong Qu.