Gas prognosis

Anthropogene Anreicherung des Methans in einem gestörten Kohlegesteinmassiv

Prognosemethode der Bereiche mit erhöhtem Gasgehalt und deren Parameterbestimmung

Anwendungsbereich

Diese Norm wird für die Prognose der Bereiche mit erhöhtem Gasgehalt und für die Parameterbestimmung, von den geologischen Abteilungen für Kohleschächte, die aufgrund des Gases gefährlich sind und auch von geologischen Abteilungen von Unternehmen, die sich mit der Förderung des Grubengases beschäftigen, benutzt.

Begriffsbestimmung •Anthropogene Anreicherungen des Methans (AAM) - Methananreicherung in der kluftigen Schicht des unterbauten Kohlegesteinmassivs

•verworfenes Kohlegesteinmassiv – das, durch Unterbau des Gebirgsmassivs, vom Bergdruck entlastete Gesteinmassiv, in dem sich Grubengas bildet

•Grubengasmenge AAM - Methanmenge, die sich in den Schichten des Kohlegesteins nach dem Unterbau gebildet hat.

•Isolinienkarte des AAM Volumenanteils - Isolinien gleicher Grubengasmenge, die auf dem Plan des Grubenraumes abgebildet sind

•Areas with increased gas content (AIG) - areas in the disturbed coal rock with gas content that is higher than the average concentration in the whole massive and the depiction on the contour map

•Parameter of the AIG - size of the AIG on the map and on the vertical section and the average amount of coal mine methane

Forecasting methods and methods for the parameter specification of the AIG 1. For the prognosis of teh gas content and the estimation of the coal mine methan eamount following data are necessary:

- caracteristics of the coal extraction and the available methan eamount in the goaf or the closed mine;

- mine working maps of the mined coal seams on the mining area or in the closed mine, that are considered for methane extraction;

- vertical cross section at strike and dip;

- data sheets of the working area with degasification activities;

- vertical cross section of the explatory borehole of the shafts and other mining areas;

- caracteristics of the coal seams and rocks in the strata above layer;

- information about gas deposit in the mine working area and about the boreholes on the prognosis area.

2. Prognosis procedure

2.1 The borders and the grid of the prognosis area are identified on the mine working map of the mined coal seam.

2.2 On this area the stock and the number of boreholes with the information of the vertical cross section of the layers, lithology, rock characteristics of the gas content, porosity, water content and gas pressure are determined.

2.3 The location of the borehole open end is determined according to the chosen grid for the prognosis.

2.4 For each borehole the coal mine methane amount in sandstones, caol seams and interlayers is estimated.

2.5 The contour map of the coal mine methane amount, the AIG are intergrated in the prognosis area in the mine working map and the parameters are determined.

3. Estimation of the coal mine methane amount in sandstone eaves for the strata of undermined rock layers from the hanging wall in deriction (along the normal) of the hanging wall is calculated using an appropriate formula.

• For each borehole the amount of sandstones is determined.

• For each sandstonethe thickness, the depth, natural porosity and the gas content are determined.

• For each sandstone besides each borehole the anthopogenic gas content in m³ gas referred to m³ of the rock is calculated.

4. Estimation of the coal mine methane amount in undermined coal seams for teh strata of the undermined rocks with a distance of the normale to the hanging wall of teh extracted coal seam in the direction of the rock hanging wall

• For each borehole the number of the coal seams containing gas and interlayers with a thickness > 0,2m is determined. The thickness, layer density and teh natural methane content are determined. • For each coal seam or each rock strata besides each borehole the anthropogenic gas saturation is calculated.

• Coal mine methane amount in undermined coal seams and interlayers for each borehole is determined.

5. Estimation of the coal mine methane amount in the undermined coal massive is the sum of coal mine methane amount in sandstones, coal seams and interlayers for each borehole.

6. Based on the data of the openend of the borehole and the coal mine methane amount for each borehole the contour map of the coal mine methane amount in undermined coal massive of the prognosis area is constructed (with the help of the interpolation method or oterh methods). A coordinate system is plotted on the contour map. The intervals correspond to the mid-distances between the boreholes on the prognosis area. Contour lines of the average coal mine methane amount are aligned on the contour map. The AIG are marked and their parameters are determined.