Energy Resources

Energy Resources

you must paraphrase in your own words from these sources; do not simply copy and paste from the source.

Natural Gas and the Marcellus Shale

Parts of this activity were modified from Sid P. Halsor, Wilkes University

Geogal: “When I was a the fitness center the other day I overheard someone say that a friend of theirs had been offered $2,000 an acre by a natural gas company”

Geoguy (while examining a hand sample of shale): “Wow, last I heard top dollar was around $1700 an acre. Can you imagine if you owned a couple hundred-acre farm in rural northeast Pennsylvania and you were offered this kind of money? And this is just to lease your land. You’d also get a percentage of the value of any gas that was produced.”

Geogal (noting the parting in the shale specimen): “Considering many farmers are just barely making it, I can see that a gas lease offer would be highly attractive. It might be the only way that farmers can survive and keep them from selling their land. After all, family farms are an essential part of Pennsylvania’s rural landscape.”

Geoguy: “But how will gas wells and the production and transmission of gas impact the land? Will a farm still look like a farm?”

Geogal: “I’ve heard that advances in technology have reduced the environmental impact of fossil fuel drilling. Still, given the vast area of land that lies above the Marcellus Shale, the landscape would surely be changed.

Geoguy (puzzled look on his face): So, how do they get the gas out of a fine-grained impermeable shale anyway??

I. Background. There is much talk about drilling the Marcellus Shale. So much so, that one would think it was a newly discovered mega-source of natural gas that could sustain our country’s needs for decades. In reality, the Marcellus has been known a gas reservoir for more than 75 years. In the late 1800s, natural gas was discovered in shale in western Pennsylvania. By the beginning of the twentieth century, just about every backyard and manufacturing plant within a mile of the Lake Erie shore in Pennsylvania had at least one gas well that kept the house or business reasonable well lighted and heated. The gas wells were shallow, generally less than 1,000 ft. and many were producing from as shallow as 25 or 30ft. The gas supply was often interrupted by variable pressure however, many of the backyard wells are still providing gas to residents of Erie County.

According to the Maryland Department of the Environment, “The Marcellus Shale has long been known as an organic-rich shale in the Appalachians, occurring at the surface and in the subsurface from New York to eastern Tennessee. Marcellus shale produces natural gas. The Marcellus Shale in Maryland is found in Washington, Allegany and Garrett Counties. The locations that have attracted the most interest for gas extraction are in Allegany and Garrett Counties. The Marcellus Shale in Western Maryland is found at depths of 3,500 to 7,000 feet.”

1. Many Pennsylvania residents have private water wells but imagine having your own natural gas well. Describe the concerns as well as the benefits of having your own natural gas well.

II. Marcellus Shale. The shale that defines the Middle Devonian Marcellus Formation is a black, organic-rich, detrital sedimentary rock. The dark color and high organic content are the result of anaerobic decay of marine organisms that accumulated with the fine-grained sediment. Organic decay occurred at depth where elevated pressure and temperature converted the carbon into natural gas. Devonian black shales are common to western Maryland bedrock and often occur with marginally organic-rich gray shales and siltstones in sequences that can be several thousand feet thick.

2. In conventional reservoirs of fluids (groundwater, crude oil, natural gas), the fluid resides in rocks that are both porous and permeable.

a) Define the geologic meaning of porous here:

b) Define the geologic meaning of permeable here:

3. Sandstones are both porous and permeable. Give an example of a sedimentary rock that is porous but not permeable.

4. What is the average grain size of a shale?

III. Shale as a reservoir rock. Black, organic-rich shale is a conventional source rock for crude oil and natural gas but an unconventional reservoir rock.

5. Look up and define the meaning of source rock here:

6. Look up and define the meaning of reservoir rock here:

Crude oil and natural gas form from a carbon-rich source at depth. Due to their lower density compared to the surrounding rock, the fluids rise up and accumulate in porous and permeable rock (a reservoir) that is capped by an impermeable layer. The impermeable cap prevents the accumulated oil and/or gas to be dispersed through the crust and lost from the reservoir. In conventional exploration, deep wells are drilled through the cap and accumulated crude oil and/or natural gas is extracted from the reservoir.

7. Why would shale, like the Marcellus, be considered an unconventional reservoir for natural gas?

IV. The push to explore and develop the Marcellus shale. Rising natural gas prices during the turn of the current century coupled with technological advances spurred interest in the Marcellus shale. Most of the exploratory and development gas wells in the Marcellus are drilled to depths ranging between 5,000 and 8,000 ft.

8. If it costs a gas drilling company about $150 per foot to drill a vertical gas well, how much does it cost to drill a 7,000 ft. vertical well?

9. An average vertical gas well might produce 45,000 cubic feet of natural gas per day. If the wellhead (top of the well before it flows into a pipeline for distribution) price for natural gas is $7.50 per thousand cubic feet, how many years will it take a gas company to recover its cost to drill a 7,000 ft well if they work 365 days a year?

V. Horizontal drilling and hydraulic fracturing. New drilling and stimulating techniques have made the Marcellus shale a viable target for gas extraction. Horizontal drilling allows a vertical well to turn and penetrate a layer of rock. This allows a much greater volume of gas-bearing rock to be intersected by a drill. Furthermore, hydraulic fracturing (“fracking”) is a technique that enhances the recovery of gas and/or crude oil. This technique involves pumping a water-based fluid and sand into a formation under high pressure. The pressure induces cracks in the rock and the sand helps prop open the cracks. Horizontal drilling and hydraulic fracturing triples the cost of drilling a well.

Read the following three short articles on drilling at http://marcelluscoalition.org/. From the website’s homepage, click on the “Information” tab at the top, then click on the “Natural Gas” tab. Read through the following tabs on the left: 1) Drilling, 2) Well Casing, and 3) Hydrologic Fracturing.

Then view a 2- minute simulation of the horizontal drilling / hydraulic fracking process at https://www.youtube.com/watch?v=O0kmskvJFt0

10. Based on your reading and the video, how are shallow aquifers protected from contamination by the drilling process and subsequent extraction of natural gas?

VI. Environmental issues associated with deep gas well drilling. Any process that extracts a natural resource from the earth’s crust impacts the environment (“we can’t get something for nothing”). Although much needed regulations emplaced over the last several decades have lessened the impacts, they have not eliminated them. Conventional vertical well drilling environmental impacts include surface disturbance (access and drilling operation set up, disposal of rock cuttings carried out of the well by a mixture of clay and water, i.e. “drilling mud”, emplacement of infrastructure to move gas into a pipeline network) and “down hole” preventative measures (contamination of groundwater aquifers, management of saline formation waters that can carry toxic chemical compounds).

11. According to the Hydraulic Fracturing article from the marcelluscoalition.org website, what percent of the fracturing fluids is composed of water and sand?

12. Does the Marcellus Drilling Coalition report the composition of the remaining percent of fracturing fluids on that webpage?

Go to https://www.earthworksaction.org/, click on the “Fracking 101” link on the right, and read the sections labeled “Hydraulic Fracturing – What It Is”, “Water Use”, “Sand and Proppants”, “Toxic Chemicals”, “Health Concerns”, “Surface Water and Soil Contamination”, and “Groundwater Contamination”. This website notes that until recently it has been difficult to learn of the chemicals that are used in fracking wells. Keep this website open.

The website http://www.fracfocus.org/ is a chemical disclosure registry for hydraulic fracturing chemicals. Go to this website, click the link “Find a Well” on the right, fill in the search option for State = Pennsylvania, and click “Search”. Click on any of the results and open the PDF. Each results PDF contains chemicals use in the well in question, and a list of the purpose of the chemical in the fracking fluid.

13. Compare the “purpose” results to the list of additive types in the earthworksaction.org website. Approximately how many additives from the list were included in the well you chose? Approximately how many were not used?

14. “Fracking” has been in the media lately, with concerns for environmental health around fracking wells, including groundwater contamination, fracking fluid spills, and fracking causing earthquakes. Read the article regarding Maryland’s ban on fracking at https://insideclimatenews.org/news/23032017/fracking-ban-maryland-larry-hogan . Based on what you read for this discussion, what is your opinion on hydraulic fracturing? Do you agree with the MD ban on fracking? Why or why not?

 

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