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

 

[DrillerNic]

I doubt very much that the gas well will cause any danger to the dam- in fact, if anything it may the other way round, with the additional weight of the water in the dam possibly causing problems for the well's geomechanics engineers. However, 3000m isn't particularly deep for a gas well, and if it's an exploration well, it will probably be pretty vertical, so there shouldn't be any geomechanics problems.

The only way there might be any danger is if the reservoir rocks are partially supported by the gas pressure in them, resulting in subsidence during production. This happens in a couple of oil fields in the world found in chalk rocks (such as Ekofisk), but I've never, ever heard of it occuring in a gas field.

As oil & gas production has been going on in the Po valley for decades (I bet you didn't know that!), I expect the geological understanding of the area is very good and that the permitting and environmental asessment system is well established, well regulated and functions correctly.

Finally, BG are a reputable company, and, like most big Oil & Gas companies, are terrified of poor publicity and often apply their own, tougher, internal standards and policies if the local laws and regulations are a little 'suspect'.

 

[NGiLuzzu]

DrillerNic,
many THANKS for your reply!

I knew about oil and gas in this area (in both prehistoric and historical periods): the first Italian Oil Refinery was established in Fiorenzuola d'Arda, 15 km from here, and in the same area there is also Cortemaggiore, were Enrico Mattei found some gas in the 50's, at the beginnings of ENI (for just a couple of examples)... but I thought it was not economical anymore to exploit the local deposits.

As I said before, I trust British Gas... but I don't trust our local Politicians!! And, believe me, if one considers (from the environmental point of view) the facts of the last years in this Valley, suspicions are well-grounded.
If I could, I would suggest British Gas to distinguish itself from this "underground" (i.e. secret, hidden) way of managing relations with Citizens and roll out a communication campaign, as many people (comprising me) in the Valley are afraid of what they don't know or, better, of what is not explained!
I think that, in this case, silence is already bad pubblicity!!

I was happy if a renowned Geologist showed, in a public meeting, how and why the gas pressure does not support the rocks and then there will be no subsidence during production, for example; if a Civil Engineer explained calculations and tests demonstrating that vibrations from drilling operations do not affect the dam wall; if a risk analysis was published; and so on...
Do I ask too much?

Sorry if I went off-topic... ;-)

Best Regards, 'NGL

 

[DrillerNic]

Well I don't know what the Italian permitting system is, but in the UK the permitting and Petroleum Operations Notice system is public...so people can read our risk assessments and environmental stuff. One way to get the information from BG would be to buy a share in BG and get attend their AGM. Or write to them in Reading, with your specific questions.

What I can say to put your mind at ease for your specific questions is that the vast majority of reservoir rocks support themselves- the number of reservoirs that compact gloablly as the oil & gas are produced are very, very small; has there been any subsidence associated with gas production from other fields in the Po valley?

Also, on hundreds of platforms worldwide drilling operations proceed a few meters away from the platform foundations without any vibration type problems (and I doubt if BG are planning to drill their wells 15m away from the dam, are they?). True a platform doen't weigh as much as your damn, but a 90,000 tonne platform and topsides supported by 6 legs maybe has a higher loading on each foundation than the loading on the dam's foundations? And surely the dams foundations would include a seismic loading which would probably be more than any vibrations from the drilling operations?

To be honest more of a concern to you should be the standard environmental concerns of drilling operations: are they using Oil or Water Based Muds? What are they doing with their contaminated fluid returns etc- especially if they are planning to use OBM? What are they planning to do with drill cuttings; especially if they are using OBM, or those cuttings contaminated by oil from the reservoir? Are they planning to test the well- if so are they going to flare the gas? How will the well be suspended at the end of operations? If the well is dry, how are they planning to abandon the well? What remediation are they planning to do to the area they cleared for the drill rig if the well is dry? These are more of an issue than the proximity to the dam; and I'd suggest you write to BG and ask them, if you have little faith in Italian regulations and legal systems.

 

[NGiLuzzu]

DrillerNic,
many thanks for your valuable answers!!

I think I'm going to write to "British Gas" as soon as I've got time enough...

Best Regards, 'NGL

 

[JUFR]

I think there will be no threat to the damm.
Gas production takes place through perforated ~8inch steel liners in ~3km depth. Depletion plan will recover as much as possible over serveral years.
Stability of pay formations is given through hydrological influx during gas depletion into the pore space.

Regards
Jürgen

 

[ppata]

I think all of this is a false problem.
Even if we are talking about a chalk reservoir, the efect of a "possible" production well to the surface is minimum (minimum because I do not like to use exact values as "zero").
If we are talking about the vibrations problem, I can give you the same answer you allready have from DrillerNic.
It can be a enviromental problem in the future, but I don't think a big company can risk a bad image and I'm sure they analise the problem.
I don't know about the "local politicians", but that problem is related to BG, so send an e-mail, and, maybe, you will have some answers.

Best regards,
Andrei

 

[NGiLuzzu]

Jürgen, Andrei,
THANKS for Your valuable posts.

In the meantime, I wrote to British Gas and they answered me, saying they followed the applicable Laws and Rules... no objections on this, they played their role; we still are a little bewildered about the Counter-parties' behaviour. But, as You guess, that is no more just a technical problem, but becomes a matter of environmental management and policy.


Best Regards, 'NGL

 

[DrillerNic]

ppata- I wouldn't say that compaction of chalk reservoirs is minimum....look at Ekofisk!

However, in this particular case, worries about surface subsidence due to compaction are negligible: I doubt that it's a chalk reseroir, and I doubt that the possible field is as big or production will be as high as Ekofisk.

The worries are all the usual environmental managment stuff of any onshore drilling activity.

 

[MortenA]

Anegri

There are many considerations when starting exploration (and possible production) close to populated area.

Often - however - public (and media) worrie) consentrate on the more spectacular but extremely unlikely scenarios.

Subsidance (as i belive it is called) is well know from large oil fields (at least in the North sea c.f. the reference to the Ekofisk field given by Drillernic) and I think it is also present at the Danish Gorm field. I dont know if its a problem in gas fields. But think about the large investments allready put into the dam and those to be spend for explaration! I believe that most companies today would do more than required by law in order to protects their own investment.

However - the most likely accident is by far related to the immediate well area. Since this area can be fenced in and supplied with adequate safety equipment accidents here should be containable.

Not long ago there were a big debate in Denmark concerning the establishement of an underground storage facility. The local (and media fueld) worries consentrated on "gas escaping through cracs". Not considering that the UGS was deep down in the groudn and that many hours had been spend surveying and engineering just to prevent this. The much more likely scenario: an accident at the wellhead area received almost no attention.

In the end the gas company had to abandon teir plans.