@Clutch do you have a professional background in oil, or are you just well clued up on Shale gas? I have a couple of questions.
1. Doesn't the extraction process pollute the local water table?
2. In the UK several sites have been shut down due to them causing earthquakes. Isn't this a risk in Pakistan too?
1. Yes and no. The issue is that when you hydraulically fracture a well you
can cause well integrity issues. What that means is you can cause micro channelling behind the cement and casing (steel pipe) of gas to the potable ground water.
However, this is largely mitigated by making sure you have multiple layers of pipe and cement protecting the ground water. 1. A cemented surface casing, 2. A cemented production casing 3. You temperture log (think of it as running a scanner) after the hydraulic fracture you don't have gas migrating up to the ground water.
If you follow those best practices (and some more details I haven't listed to keep this simple) you will protect the ground water. There are thousands of shale hydraulically fractured wells... And only very few of them leak to the groundwater.. and it's mostly because the company cut corners
not because shale gas wells are particularly prone to this.
2. Yes, earthquakes are an undeniable risk for the hydraulic fracturing. More so in certain jurisdictions thanks others. The main mechanism is due to pore pressure increase of hydraulic fracture fluids causing existing stress faults into slipping. What that means... The earth has faults ("cracks") and these faults are held together under stress. Think of a jigsaw puzzle you are holding up and pushing together from all sides making sure it doesn't fall apart. Now when you fracture you "lubricate" that fault it will slip. Something akin to you holding your hands clapped together with alot of pressre and I come along and pour oil between those hands... They will slip.
So what about Pakistan...
These faults are more prevalent in mountain making regions. .They run parallel to mountain making regions. In Pakistan the Himalayas run approx east-west in the north and some what north-south in the western region of Pakistan. This causes a complex stress regime and possible a lot of natural fractures. Pakistan is already known for being an active seismic region. My guess is (I don't know too much about Pakistan's geology) Pakistan is at particularly high risk... More so than the North American region I'm from.
But almost all earthquakes recoded because of hydraulic fracturing have been "small". The maximum ever recorded was about ~4 on the Richter scale. Usually a completions company is required to have real time monitoring when they stimulate (fracture) the well. And immediately shut-in if they cause a induced seismic event.
Hydraulic fracturing has risks. But if done right with proper regulations has been proven to be a viable technical.
Don't believe everything you hear in the media. A lot of it based on fear and misinformation or just pure scientific ignorance.
