THE EFFICIENCY COMPARISON OF DEGASSING POROUS ENVIRONMENT BY TWO DIFFERENT OPTIONS OF DEGASSING USING MODELLING AND SIMULATION

References: 12th International Multidisciplinary Scientific GeoConference, www.sgem.org, SGEM2012 Conference Proceedings/ ISSN 1314-2704, June 17-23, 2012, Vol. 2, 511 - 518 pp

ABSTRACT

One of the problems encountered in the areas with abandoned mining activities in coal
underground mines is emergence of methane from residual parts of the coal seams.
The article responds to the need for knowledge of natural processes in the given area,
and therefore deals with the simulation and modelling of methane flow from
underground to the surface through the rock massif. Model of the natural environment
corresponds to our knowledge of the realistic situation and possibilities of tools used for
creating the models. In the model explored, the massif is composed of two types of
rocks with different gas permeability and one degassing borehole. In the first case, we
deal with a borehole with casing and with perforations; in the latter case, the given
borehole without casing along the whole length in the rock environment. Our task is to
compare differences in the methane flow in the borehole area and in the abovementioned
boreholes as well as during changes in barometric pressure.
Exclusivity of this original approach is the effort to visualize and demonstrate how the
gas behaves in a porous environment in the model examples that we tested. Without the
use of numerical flow technology, commonly referred to as CFD programs
(Computational Fluid Dynamics) [1], we can practically never visualize and learn the
situation in flowing through porous compact rock which is unaffected by human
activities except for the exploratory borehole. Thanks to the use of the Fluent program,
we are able to theoretically simulate and subsequently learn how ambient influences
may alter and act upon the flow from underground to the surface and change the
immediate conditions affecting this flow.
To create a geometric model of the working area, we used the Gambit software tool; for
modelling the gas flow, we used the CFD Fluent software, ANSYS, Inc. [2]

Keywords:
rock degassing, CFD program, Fluent software, degassing borehole,
modelling and simulation, flow of gases, borehole with and without casing