Shallow seismic reflection survey for imaging deep-seated coal layer - Case study from Muara Enim coal

Indonesia has a great potential for deep-seated coal resources. To assist and support the deep-seated coal exploration, a shallow seismic reflection method is applicable for this purpose. This study has conducted a shallow seismic reflection method in Musi Banyuasin Regency, South Sumatera Province. The Muara Enim coal target varies from 100 to 500 meters from the surface. The thickness of the coal layer varies from 2 to 10.65 meters. This study uses 48 channels with 14 Hz single geophone and MiniSosie as the energy source. The receiver and source interval is 15 meters. This study uses a fixed receiver and moving source configuration. From the interpreted seismic section, this study identified a deep-seated coal layer target. These layers are Mangus, Burung, Benuang, Kebon and Benakat layers. A simple interpretation is analyzed by combining the seismic amplitude characteristics and the thickness of the coal layer from the borehole data. From the interpreted seismic section, deep-seated coal layer targets have strong amplitude characteristics and are continuous from southwest to the northeast with a down-dip of around 20-30°. This study helps to inform the operator companies who develop the utilization of deep-seated coal (coalbed methane, underground coal gasification and underground coal mining) about the effective and proper geophysical method for imaging deep-seated coal layer.

Features of Borehole Degassing of the Outburst-prone Coal Seams

The conditions and features are given concerning the degassing of outburst-prone coal seams by wells drilled from the underground workings in the plane of the mined seam. Technological schemes for the location of wells in the mining areas during the preparation and development of the coal seams prone to sudden outbursts of coal and gas were substantiated taking into account the coal strength determined using the method of M.M. Protodyakonov. The scheme of coal seams degassing by wells oriented to the working face line is recommended with a coal strength factor f ≥ 1.3, the degassing scheme with crossed wells — at f < 1.3. The wells are drilled parallel to the working face line and oriented to it. The schemes are implemented in the shallow mines of Karaganda (Kazakhstan), Ukraine and China. Degassing of coal seams not unloaded from the rock pressure by crossing wells ensured an increase in methane production from 1 ton of coal by 0.4–4.8 m3 in the conditions of seams with different coal strength. The highest indicators were achieved in the powerful outburst-prone seams with a coal strength factor of f = 0.3–0.8 in the conditions of the mines of Karaganda Basin, where the volumes of methane extraction by crossing wells were 5.0–5.6 m3 per ton of the degassed coal reserves in the working areas. In the conditions of the outburst-prone shallow seams of Ukraine, the volumes of methane extraction from 1 ton of the degassed coal reserves on the medium density seams amounted to 2.5–4.4 m3 with a coal strength factor of f = 0.6–1.1. 2-2.3 m3 of methane was removed from 1 ton of coal at the Dziulishan mine (China) at a strongly crushed coal layer II1 with a strength factor f = 0.3–0.6. The use of degassing schemes for gas-bearing and outburst-prone coal seams ensures an increase in the productivity of working faces and, as a result, high economic indicators.

ASSESSMENT OF MAIN ROOF CA VING INCREMENTS IN WORKING FACE PROCESSING OF TOLMACHEVSKY COAL LAYER WITHIN THE DIP-WORKING PANEL 18-2

This work reviews the study aimed to assess the actual increments of the main roof caving which appear in the course of working face processing of ‘Tolmachevsky ' coal layer in ‘Polysayevskaya' coal mine as the main parameter defining the degree of abutment pressure influence on mine tunnels adjacent to working face.