4.5 What are Oil Sands vs. Oil Shales? Petroleum Geology

Summary

This video explains the differences between oil sands and oil shale, two key sources of unconventional oil. Oil sands, primarily found in Alberta and Venezuela, contain bitumen, a heavy, viscous oil that requires energy-intensive extraction methods like surface mining and in-situ drilling. While oil shale, notably in the Green River Formation, holds vast untapped oil reserves, it faces similar challenges due to its mineral content and high processing costs. Both resources have significant environmental impacts, including land disturbance, water use, and waste disposal issues, making them complex and costly alternatives to conventional oil.

Takeaways

• 😀 Oil sands, also known as tar sands, are mixtures of clay, sand, water, and bitumen, a thick, viscous tar.
• 😀 The term 'sand' is misleading, as oil sand deposits can also be found in shale, limestone, and other materials.
• 😀 Oil sands are more viscous than conventional oil, making extraction more difficult and energy-intensive.
• 😀 The largest oil sands deposits are found in Alberta, Canada, and the Orinoco River region in Venezuela.
• 😀 Extracting oil from oil sands requires methods like surface mining or steam injection to reduce bitumen viscosity.
• 😀 Surface mining of oil sands causes significant land disturbance and requires large amounts of water for processing.
• 😀 Approximately 80% of Alberta’s oil sands are too deep for surface mining and require in-situ extraction methods.
• 😀 In-situ oil extraction uses steam to heat the oil sands, allowing the bitumen to migrate toward production wells.
• 😀 In-situ techniques are expensive, require water, and face challenges related to efficiency and energy costs.
• 😀 Oil shale contains large amounts of untapped oil, with the Green River Formation holding nearly half of the world's reserves.
• 😀 Producing oil from oil shale faces similar challenges as oil sands, including high mining costs, environmental damage, and water usage.

Q & A

What are oil sands, and what is their composition?

Oil sands, also known as tar sands, are mixtures of clay, sand, water, and bitumen, a thick, tar-like oil. The oil is highly viscous and cannot be easily pumped out of the deposits.

How do oil sands differ from conventional oil reservoirs?

The primary difference is the viscosity of the oil. In oil sands, the oil is much more viscous, making it harder to extract compared to conventional oil, which can flow more easily.

Where are the largest oil sand deposits located?

The two largest oil sand deposits are found in the Athabasca oil sands in Alberta, Canada, and the Orinoco River deposit in Venezuela.

How is oil extracted from oil sands?

Oil is extracted through surface mining or in situ recovery. In surface mining, the material is excavated and heated with pressurized steam until the bitumen softens, allowing it to be extracted. In situ recovery involves injecting steam into deep deposits to reduce the viscosity of bitumen.

What are the environmental concerns related to oil sands extraction?

The extraction process causes significant land disturbances, requires large quantities of water, and creates toxic disposal ponds with contaminated water and sediment. Additionally, the energy needed for extraction is substantial.

What is in situ recovery, and what challenges does it face?

In situ recovery involves injecting steam into deep oil sand deposits to reduce the viscosity of the bitumen, making it easier to recover. Challenges include high energy costs, water management issues, and improving recovery efficiency.

How do oil shale deposits differ from oil sands in terms of content?

Oil shale contains large amounts of untapped oil, but the oil is less readily recoverable compared to oil sands. Oil shale is primarily made up of sedimentary layers rich in organic material that can be processed into oil.

What is the estimated oil content in oil shale deposits, and how recoverable is it?

The U.S. Geological Survey estimates that oil shale deposits contain over 3,000 billion barrels of oil. However, only a small percentage of this oil is recoverable with current technology, and this percentage may increase with further advancements.

Where are the world's largest oil shale deposits located?

The Green River Formation, located in Colorado, Utah, and Wyoming in the United States, holds about half of the world's oil shale resources.

What challenges are associated with producing oil from oil shale?

The challenges include high energy costs due to the low energy content of oil shale, environmental concerns related to mining, water usage, and waste disposal, similar to those associated with oil sands extraction.