getting oil out of the ground was fairly easy. You could find areas that had natural oil seeps that were leaking out of one of those anticline folds and drill into the crest of the fold and you're in the oil business. while some of these deposits were under enough pressure for the oil to flow up the pipe, after a while that pressure was gone and you had to start pumping it out of the ground. Again, this wan't pumping out of a lake of underground oil, it was like stiking a straw into a sponge and pulling the oil towards the end of the drill hole. As the oil became depleted, in order to get as much as they could out of th porus rock, they would inject water back down into the reservoir to try to force the oil towards the well. This works pretty well, but still, have you ever managed to get all the water out of a sponge? this is called the recovery rate, and it is a science and an art unto itself. At best, you might get 90% of the oil out. On average, it is less than that. And if it is not done correctly, that number drops to 30-40 percent.

All of this is easy oil. We've lived on this for a century now, and petroleum geologist and engineers are damn good at getting every drop they can.

they are so good at finding and exploitng these types of deposits that there are not many left. those that remain are in ecologically protected areas, and they are still limited compared to the amount we've tapped.

Which brings us to fracking. Fracking is a way of drilling very long wells that run horizontally through the rock strata, then the well is prussurized with fluids to fracture the surrounding rock to create pathways for the oil and cas to migrate towads the drill hole so that it can be recovered.

But here is the difference from the classic, simple oil reservoir. We are no getting the oil and gas from the Source Rock, the shales that, given time would have yield their hydrocarbon to the process I discussed above. The shales are "tight". If we just sank a drill hole into them they would produce very little. there are no conduits for the oil to flow through to the well. So fracking creates the fractues to allow the hydrocarbons to be pumped out.

The advantage is that we are not waiting for Ma Nature to go through the long process of moving that oil to nice porus rock units, we are getting it directly from the source rocks.

However, the process is expensive, require an enormous amount of water (millions of gallons), and the wells really don't last all that long. In addition, in order to create the high pressures to fracture the shale, all kinds of things are added to the water to increase to effective pressure. What chemicals you ask? Well, that's the thing. Each company has its own propritary mixture, and they are pretty tight lipped about what they are shoving down the wells.

The process also requires a whole lot of sand. The sand is injected into the cracks to keep them from closing up and provide a nice permiable path for the oil and gas. In fact, there is such a huge demand for just the right kind of sand that quarrys are opening all over the place to supply the drillers with what they need.

And yes, injecting fluids under pressure can create earthquakes. This has been known wince the 1960's when the military was disposing oil nerve gas bay pushing it down deep wells north of Denver, which experienced temblors of around 6.0 in magnitude. Now the fluids don't lubricate exisitng faults, but they reduce the pressure needed to allow the fault to fail.

...conclusion to follow...probably tommorrow...