Percussion drilling in old mine workings
Percussion drilling in old mine workings
(OP)
Good day
We are a geotechnical engineering company and we are busy with a project where we will need to do percussion drilling into old bord and pillar coal workings. We are concerned about the possibility of drilling into methane and are concerned that this might cause combustion. Can anyone advise me on the risk of such an occurrence and possibly supply me with some mitigating measures?
I will really appreciate your help.
Regards
We are a geotechnical engineering company and we are busy with a project where we will need to do percussion drilling into old bord and pillar coal workings. We are concerned about the possibility of drilling into methane and are concerned that this might cause combustion. Can anyone advise me on the risk of such an occurrence and possibly supply me with some mitigating measures?
I will really appreciate your help.
Regards
RE: Percussion drilling in old mine workings
RE: Percussion drilling in old mine workings
I am aware of the severity of methane explosions in general.
When doing rotary core drilling, one has drilling fluid/water constantly flowing at the drill-bit, which should prevent ignition. I am concerned about doing percussion drilling into these areas though.
Any mitigating measures to prevent ignition that you can recommend?
Thank you in advance!
RE: Percussion drilling in old mine workings
RE: Percussion drilling in old mine workings
The project is in South Africa in a remote area, so some flyrock won't be a problem. Hangingwall conditions are probably sandstone.
The last mining that took place in the area was in 1980, so we need to determine amongst others the hangingwall conditions (and obtain samples for laboratory testing), general lithology of the area and we want to use some down the hole photography (if possible) to view the current conditions in terms of pillar scaling.
Yes, the specs have been submitted to the drilling contractor, but if we need to change any of this to allow for remote drilling to decrease the consequence in the event of an accident I am sure we will be able to somehow include this.
I have thought of first drilling a rotary core hole and then inserting a methane sensor to at least give us an indication of possible risk.
I would really like to hear your thoughts.
RE: Percussion drilling in old mine workings
RE: Percussion drilling in old mine workings
One of the possibilities we are also considering is to proceed with the first couple of meters with percussion drilling, to about 5m above the workings and then use diamond drilling for the final 5m (with calcium carbonate in our drilling fluid).
This obviously has some logistical implications, but do you think it can work?
RE: Percussion drilling in old mine workings