Gas Exploration close to Reservoir Dam...? 1

[NGiLuzzu]

Dear All,
I live in a small village in Northern Italy called Lugagnano, in the valley of a small river called Arda, between Piacenza and Parma (at about: latitude 44.8 N, longitude 9.8 E). Maybe Veleia (Roman city) and Castell'Arquato (Middle-Age castle and town) are the most famous places in the area.
Just to give you an idea, the local landscape (the hills half-way between the Po plain and the Apennine mountains) is characterized by argil outcrops called "Calanchi", where you can find many marine fossils, including shells and whale bones. For this a geological era was also called "Piacenziano" (a subdivision of the Pliocene era).

A few miles South, i.e. upstream respect to Arda river, there is a big dam that provides the whole valley with both drinkable and irrigation water (the place is called Mignano, within the municipal territory of Vernasca). At the moment I can't say exactly how many tens of meters the dam wall is high or how many millions of cubic meters of water the artificial reservoir may contain... For sure I know that, at least on the surface, there are not hard rocks and the area is frequently subject to landslips.

Now it seems that, in the next months, the drilling of a 3,000 m deep gas exploration well will be started, not far from the dam itself.

At the web-page

http://www.bg-group.com/international/int-italy.htm

you can read:

" EXPLORATION

BG Group has concentrated its Italian exploration and production activity on high potential oil and gas exploration acreage in the Sicily Channel and the Po Valley. The portfolio consists of ten exploration permits (five of which are BG Group-operated) and four applications (three of which are BG Group-operated).
(...)
A three year onshore exploration programme is underway in the Po Valley, with two seismic acquisition programmes, including an innovative sparse 3D technique, acquired in 2003/2004. The first operated well is scheduled to be drilled starting in early 2005, subject to the granting of environmental approvals..."

As I'm not very confident about our local Politicians who have to decide about that "environmental approvals" ;-) my question is: if gas is found and extraction begins, could that be dangerous for the dam (and pond) stability? Would be possible that something moves underground?

Such a location for a gas well sounds very unusual to me, but I'm not in the business and so I may be wrong... can anyone provide some other examples of gas or oil wells close to dams, reservoirs or lakes?

Many thanks and best regards to All,
'NGL

 

[cvg]

I'm not an expert in drilling, but would guess that when the wells are drilled, that the interface with the aquifer would be sealed to keep the groundwater out of the gas well.

 

[JedClampett]

I'm not an expert on anything, but I saw a case on "Engineering Disasters" on the History Channel where a dam lining failed in California in the 60's and drilling for oil close by was thought to be a contributing factor. The dam had an asphalt liner that cracked either due to an earthquake fault or oil drillers injecting very high pressure water in the wells to push out the oil (or maybe both factors). The pressure might have cracked the asphalt. When the liner cracked, a leak developed and the dam failed.
It's worth an independent study of how the drilling will impact the dam.

 

[cvg]

to answer the original question would require a lot of data and engineering analysis. You have not provided enough information to answer the question. I would do some probing to find out if failure of the dam or reservoir has been considered and if such a study has been done.

 

[NGiLuzzu]

Cvg, JedClampett,
many THANKS for your replies!

It's true, I didn't provide any engineering data... but the fact is that no data were published!!
We've been hearing rumors for months, without precise information; I learned about the name of the Company and the depth of the well only by reading a letter to a local newspaper from a environmentalist self-organized Citizen's council.
In fact, no communication campaign was seen, no information about risk analysis was given, no public explanation meeting was announced, so far...

Of course, a serious analysis would take in account many critical aspects and would need a lot of detailed information... but at the moment I would be satisfied even with general considerations only (as I'm now speaking as a Citizen, more than as an Engineer).

In any case, any information about the "disaster" you mention could be interesting.

Best Regards, 'NGL

P.S.: Please take also a look at Thread470-108931.

 

[JedClampett]

Try:

http://www.osti.gov/energycitations/product.biblio.jsp?osti_id=5596621

 

[flamby]

I have no idea of gas explorations but if you go deep enough, it is nearly certain you will be going below the ground water table, whether there is a dam in the vicinity or not. I do not think there is big issue if the dam is close by. Afterall, there are big gas explorations taking place below the sea bed!!

 

[Bouma]

I worked on a BLM mine closure in New Mexico; it was a potash mine located 1 mile (1.6 km) underground; it extended 17 miles (27.2 km) horizontally. Soils above were sedimentary. The mineworks were typically about 6' (2 m) high, followed the potash seam wherever it went. In some cavernous places pillars were left in place to compress (the potash is a salt seam and relatively plastic). Subsidence effects at the ground surface above the mined area affected roadways, breaking the asphalt and posing driving hazards, even at some distance away.
I would be very concerned about what is being proposed in your situation.