Unconventional fossil fuels - shale gas and tight oil (Week 9, Lecture 1)

Summary

This lecture explores unconventional fossil fuels, such as shale gas, tight oil, and tar sands, highlighting their extraction methods and environmental challenges. It contrasts these with conventional fossil fuels, explaining the use of horizontal drilling and hydraulic fracturing to release oil and gas from low-permeability rock. The environmental impacts include rapid production decline rates, methane migration risks, wastewater disposal concerns, and induced seismic activity. Additionally, the lecture addresses the risks of gas flaring and transportation accidents, such as those related to pipelines and rail, emphasizing the growing role and environmental concerns surrounding unconventional fossil fuels in modern energy production.

Takeaways

• 😀 Unconventional fossil fuels are those that haven't migrated to a trap like conventional oil and gas, and are found in the source rock itself.
• 😀 Unconventional fossil fuels include shale gas, tight gas, tight oil, tar sands, oil shale, and methane hydrate, each with unique characteristics.
• 😀 Horizontal drilling and hydraulic fracturing (fracking) are used to extract unconventional fuels, as petroleum is tightly held in low-permeability rocks.
• 😀 Horizontal drilling allows oil and gas production with a small surface footprint but large subsurface reach, tapping into many layers of rock.
• 😀 Shale gas and tight oil have become increasingly important in U.S. energy production, with shale gas accounting for 80% of U.S. natural gas production by 2018.
• 😀 The U.S. is now a net exporter of natural gas and a small net importer of oil, with tight oil contributing significantly to U.S. oil production.
• 😀 Shale gas and tight oil production is highly concentrated in specific regions, with Texas, Pennsylvania, Oklahoma, and Louisiana leading the U.S. in production.
• 😀 The production from unconventional wells declines rapidly, requiring drilling of more wells to maintain output, which increases energy usage and environmental impact.
• 😀 Environmental concerns with hydraulic fracturing include chemical contamination, methane migration into groundwater, wastewater disposal, and induced seismic activity.
• 😀 Flaring of natural gas, primarily in North Dakota and Texas, wastes resources and releases greenhouse gases, contributing to climate change.
• 😀 Transportation of tight oil via rail poses risks, including spills and explosions, especially in regions like the Bakken shale oil fields in North Dakota.

Q & A

What are unconventional fossil fuels?

Unconventional fossil fuels are energy resources that remain in the source rock, such as shale or tight sandstone, instead of migrating to a trap like conventional oil and gas.

How do unconventional fossil fuels differ from conventional fossil fuels?

Unlike conventional fossil fuels, which accumulate in easily accessible pockets (traps), unconventional fossil fuels are trapped in source rocks with low porosity and permeability, requiring advanced extraction techniques.

What are the primary methods used to extract unconventional fossil fuels?

The primary methods are horizontal drilling and hydraulic fracturing. Horizontal drilling allows access to multiple layers of rock, while hydraulic fracturing fractures the rock to release gas or oil.

What is hydraulic fracturing, and why is it important for extracting unconventional fossil fuels?

Hydraulic fracturing, or fracking, involves injecting a mixture of water, sand, and chemicals at high pressure to fracture rock and release trapped oil or gas. It is crucial because it makes it possible to extract petroleum from tightly held sources like shale and tight sandstones.

What are some environmental concerns associated with hydraulic fracturing?

Environmental concerns include water contamination from methane migration, seismic activity due to fluid injection, high levels of methane emissions from flaring, and the risk of spills during transportation of oil.

What is the significance of shale gas and tight oil production in the U.S.?

Shale gas and tight oil production have significantly increased U.S. energy output, making the U.S. a net exporter of natural gas and reducing oil imports. By 2019, tight oil accounted for about 63% of total U.S. crude oil production.

How does horizontal drilling work, and what are its advantages?

Horizontal drilling involves drilling vertically to a target depth and then turning the drill bit horizontally to access multiple layers of petroleum. This method increases the subsurface area tapped while minimizing surface impact, allowing for more efficient extraction.

What is methane migration, and why is it a concern?

Methane migration occurs when gas or fluids escape from wells or fractures and contaminate groundwater. It is a concern because it can lead to permanent water pollution, affecting drinking water sources and ecosystems.

What is induced seismic activity, and how is it related to hydraulic fracturing?

Induced seismic activity refers to earthquakes caused by human activities, such as the injection of wastewater deep underground. This process has been linked to small earthquakes in areas like Oklahoma and Ohio, where high volumes of wastewater are injected into the ground.

What are the risks associated with the transportation of tight oil?

The transportation of tight oil, especially from regions like the Bakken, poses risks such as spills, explosions, and accidents, particularly when the oil is transported by rail through populated areas.