Energy Resources

Environmental Geology lecture outline

Content:


Primary energy sources?

Quick background information:

Chart of U.S. energy use from Lawrence Livermore National Laboratory. What is perhaps most surprising as you look at this chart? Source: https://publicaffairs.llnl.gov/news/energy/energy.html#2008

The changing picture for China of energy production. Image source: http://www.eia.doe.gov/emeu/cabs/china/part2.html

USGS site concentrating on hydrocarbon energy sources.


Geology of hydrocarbon formation (3 requirements)

What follows is some of the science behind 'conventional' oil and gas. Oil and gas in tight reservoirs (often shales) and fracking have caused a significant shift in our energy landscape and are now so widely practiced that it is hard to call it unconventional. These are discussed afterward.

The three components of conventional oil and gas:


Tight reservoirs and fracking

Have known for many decades that there was oil and gas trapped in "tight" formations such as the Bakken shale up in North Dakota. Tight means low permeability. However, typical vertical wells could not pump the oil and or gas from these tight rocks. Fracking is part of a 4 part technology that has allowed us to extract this oil and gas. The unconventional deposit became a conventional deposit as technology developed.

Four components of fracking operations:

Image from USGS and US EPA showing a schematic of a fracked oil and gas well. Source: http://water.usgs.gov/owq/topics/hydraulic-fracturing/ .

Other 'unconventional' hydrocarbon energy resources?


Oil and gas from a carbon cycle perspective

Carbon cycle consists of three linked parts:

Carbon cycle diagram (excluding the inorganic) from NASA showing estimates of amounts and fluxes. Oil, gas and coal are part of the "Sediments" reservoir. Source: http://earthobservatory.nasa.gov/Features/CarbonCycle/carbon_cycle4.php

Short and long term carbon cycles together in a box and arrow diagram. The weathering of exposed sedimentary rock, with its carbon in it returns C back to the surface environment and to the short term cycle. That 'weathering' also includes a suite of microbes that eat these organics, producing methane.

Image from USGS showing some transfer estimates between the atmosphere and other carbon sinks that are contributing to carbon dioxide build up in the atmosphere. Image source: http://pubs.usgs.gov/fs/fs137-97/fs137-97.html


Cradle to grave approach

There is a Hindu tale of the three blind wiseman, which basically indicates it is wise to be able to see the whole beast and not just parts. The cradle to grave approach is a systems thinking type of approach, to be ore holistic in one's considerations. It is an excellent way to identify unintended consequences, and true cost effectiveness.

This diagram captures a lot, but one missing component is the production of waste water during the extraction phase. A standard approach is to take what are usually very salty waters (saltier than seawater in some cases) and inject them back down into an old field. This is what can induce seismicity. There are other missing components.

What are exploration techniques for hydrocarbons?

Seismic section image off the coast of California showing sedimentary layering, faults, and other geologic features. Some of the features, especially in the deeper and lower parts, are artifacts of the imaging technique, and it is helpful to be trained in the interpretation of seismic sections. This type of data is crucial and common in oil exploration. Note the vertical scale of depth. Image source: http://walrus.wr.usgs.gov/mapping/csmp/data_collection.html

Extraction and secondary recovery techniques.

Environmental concerns associated with transportation, refinement?

What are larger concerns associated with intense fossil fuel use?


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