Friday, January 27, 2012

Lecture 9 Summary and Notes

Some important concepts for the day...

1. Fracking (short for hydraulic fracturing) is a technique that allows for the exploitation of petroleum reservoirs that would otherwise not be economically recoverable due to low permeability in the source or reservoir rock. Discussion of fracking in the MSM are usually associated with natural gas but is also used extensively in tight oil resources like the Bakken formation in ND.

2. Fracking generally involves the following steps:

a. drill to the depth of a horizontal or sub-horizontal, organic-rich source rock or tight (low-permeability) reservoir rock then drill horizontally (concordantly) through the middle of the source or reservoir rock layer.

b. seal the annulus of the well to prevent interaction between the relatively shallow water table and fluids in the relatively deep source rock layer.

c. use directed explosives to induce fracturing within the source rock

d. inject fracking fluid at extremely high pressures to expand the fractures in the source rock (enhanced permeability)

e. remove fracking fluid from the well leaving behind proppants (usually sand) to keep the cracks dilated once the pore fluid pressure returns to normal

f. collect natural gas as it flows out of the source rock and into the well pipe.

The link to the interactive animation, which I would encourage you to watch on your own can be found here.

2. The composition of fracking fluid is specific to the drilling company and, while the materials that are present are generally known there are laws that prevent companies from having to disclose the precise amounts of the chemicals present (trade secrets). The components of fracking fluid can be characterized as:

a. water (mostly),

b. proppants (sand is a good one),

c. lubricants, preservatives, and viscosity enhancers, and

d. anti-corrosive agents (because many of the lubricants, preservatives, and viscosity enhancers are corrosive.

3. Fracking fluid is not regulated as a hazardous waste at the federal level; this makes disposal much more convenient and inexpensive but also presents potential problems (more on this on Monday). Fracking fluid can be recycled (not reused) to some degree and is even re purposed as a road deicer in some areas. Recycling practices are on the rise in most areas and are largely (entirely?) voluntary.

4. According to the EIA AEO 2011 and the AEO 2012 Early Release Overview, natural gas production will increase substantially in in the next few decades and this increase will come from shale gas and tight gas- both of which require the fracking technique to be technical, energetic, and economic recoverable

5. Natural gas and oil form in similar ways from similar materials in similar geologic settings but once they come out of the ground, there are some important differences:

a. NG is cheap enough that, when it occurs in combination with an oil reserve, sometimes it is cheaper to dispose of the NG than to capture and sell it. The NG is disposed of through flaring. To my knowledge, no one burns waste oil on purpose.

b. NG is more difficult to transport by truck or boat (is has to be pressurized into a liquid) and so pipeline infrastructure is more important with NG than with oil

c. The difficulty of cheaply and practically transporting NG without pipeline infrastructure means that very little NG is imported to or exported from the USA; ~60% of oil consumed in the USA, on the other hand comes from imports.

Slides from lecture are on Sakai. I will be around this weekend to provide assistance with the homework assignment that is due on Monday. Your "reading" assignment for Monday is episode 440 (originally aired 07.08.2011) of the Public Radio International Documentary Show This American Life called "Game Changer" about fracking in PA. You can stream the program for free on any computer with an internet connection (or you can download it for $.99). If you would prefer to read instead of listening, the transcript cam be found here.

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