Borehole bubbling - any ideas? 1

[ac4u2nv]

Dear all

Was rotary coring into good quality mudstone interbedded with siltsotne
And sandstone. Recovery dropped and then the water rose to almost ground level and started bubbling!
We thought we either hit a service but felt it was unlikely 5 m down into bedrock. Or we’d hit a void and this was releasing gas. Gas readings on monitor and PID all indicated 0 readings. After leaving it for a day the level has dropped to 1.6mbgl similar to nearby borehole level.
Any ideas what this could be?
No history of coal mining either in area

https://files.engineering.com/getfi...trim.5F411FB6-9808-4FF2-9215-A65DDB43F696.MOV

 

[EireChch]

Maybe you just hit a small artesian aquifer, there was only a small amount of pressure which has dissipated?

I hit one artesian well before while in sand. It kept flowing and flowing. We had to have the well re-drilled and grouted with bentonite to seal it.

 

[Ron]

Agree with EireChch....you likely hit an artesian pocket

 

[oldestguy]

We hit a few of those situations and on one installed a well for possible future use at a bridge. Years later it still was running.

 

[Ron]

There is one at a roadside near Orange City, Florida that has been running for at least 50 years that I know of.

 

[fattdad]

we had a methane bubble that ran for a few months. There was adjacent sand drains and preloading.

I was working along the Gunnison River (Colorado) and saw a geyser on the other side of the river. Next day went over there and it was old drill timbers encased in travertine. Apparently, it was a carbon dioxide find from decades earlier (hopeful dry ice plant?).

In the Coastal Plain of Virginia, we have a lot of confined layers with artesian head. So, that makes sense.

In the Valley and Ridge, we have uplifted sediments and can also see holes making water. No doubt the bubbles are going along for the ride.

I once did a water supply job and we had to worry about well head protection and the water source. That was interesting! We did water sampling over time - ran the samples through a filter with the goal of seeing if we could find insect parts and other signs of surface-water interaction.

No clear answer, but it's all interesting!

f-d

ípapß gordo ainÆt no madre flaca!