That is a lot, and you are correct about oil wells.. Indeed some I believe have been producing for over 100 years.
1.25 Bncm would be a good result from a well, equivalent to about 3000 barrels of oil per day for 8 years ( or more likely 6000 bopd dropping off due to pressure decline ). Maybe a tadge on the high side, not all wells would be that successful.
100,000 of those .... About 80 trillion dollars worth at current prices.
Say 10 trillion per decade for 80 years squished and you are looking at a boom to the economy in GDP terms of nigh on 50% nationally.
Of course the price of energy would drop through the floor, as it has in the states, though it isn't a zero sum game. Cheap energy equals cheaper and more efficient industry, well paying jobs for your children and miles cheaper utility bills. There are few downsides to cheap energy. If the history of energy prices in the US holds up to be true then still a good 15% of GDP, enough to put the North in general, and Lancashire in particular back where it belongs at the pinacle.
But yes, the impact of all those wells would be considerable, almost 5% of Lancashire by area, not including infrastructure such as roads and whatnot.
So it's a tradeoff between economic growth and environmental protection which as I'm from Lancashire is close to my heart.
Of course there is also the issue of who would benefit most. The drilling companies or the people.
At which point I can't help but plug UKIP's policy of a sovereign wealth fund from fracking profits. Would easily clear the national debt within a decade by my calculations...
I doubt anyone would ever agree on the correct extent or formulation, some would consider a single well to be too many and others ( especially those lovely politicians living in Kensington who once saw the North on tele and didn't like it) wondering why only 100,000 wells.
At the end of the day it is for the locals to weigh up the costs and benefits. Some costs though are generally unforeseen or involve losing things which cannot be replaced. Wildlife habitats, natural beauty and peace and quiet being three I can think of.
As for the unforeseen I would caution anyone with $ signs in their eyes to think again, Norway's oil boom was spectacularly good for their economy and they wisely invested the profits ( as Tony Benn wanted to do with our North Sea Oil ) with only 4% available yearly and the rest into their sovereign wealth fund.
Some of the downsides however were unforeseen. When a seaside shack would sell to an oil company for over $1m it gradually pushed the locals out. Easier to sell up and let them build a warehouse or whatnot than stay and watch your hometown change beyond recognition.
I want the best for Lancashire and I certainly don't know where the balance should lie.