Lesson 09 – Earth Materials & Energy Resources (Core Notes)

Energy is portrayed as a foundational driver of social‐economic advancement.
- Enables industrial production, transportation, communication, modern medicine, and overall quality of life.
Key guiding question raised: “How do we ensure self-sufficiency for current and future generations?”
- Implies strategies such as diversified energy mix, technological innovation, sustainable resource management, and policy planning.

Fossil fuels are fuels formed by natural anaerobic decomposition of buried dead organisms.
Geological timescale: often millions (sometimes >650 million) years old.
Characterized by high carbon content.
Primary examples: coal, petroleum, natural gas.
- Common derivatives: kerosene, propane.

Coal = combustible black or brownish-black sedimentary rock occurring in layers/veins called coal beds or coal seams.
Harder varieties (e.g., anthracite) may be considered metamorphic due to later heat/pressure exposure.
Elemental composition: chiefly carbon plus variable $\text{H},\;\text{S},\;\text{O},\;\text{N}$ .

\text{>300} million years ago: large, swamp-based plants die and accumulate.
Buried under water and sediments (dirt, rocks) → oxygen-poor environment.
Ongoing burial → increasing heat & pressure convert plant debris → peat → lignite → sub-bituminous → bituminous → anthracite.
- This progressive transformation is coalification (aka bituminization / carbonification).

Optimal coal formation: Carboniferous Period $\left(360-290\;\text{Ma}\right)$ .
Continued but lesser formation:
- Permian $\left(290-250\;\text{Ma}\right)$ ,
- Mesozoic Era $\left(250-65\;\text{Ma}\right)$ ,
- Tertiary Era \left(<65\;\text{Ma}\right) (yields less-mature lignite).
Special cases:
- Paleocene coals $\left(65-55\;\text{Ma}\right)$ — Colombia, Venezuela.
- Miocene coal $\left(~20\;\text{Ma}\right)$ — Indonesia (high geothermal gradient → near-surface anthracite).
- Moscow Basin: remains at lignite stage (insufficient heat).
- Modern peat deposits $\left(0-0.01\;\text{Ma}\right)$ still recognizable as plant debris.

Anthracite: $86-98\%$ carbon, $8-3\%$ volatile matter.
- Highest energy density; domestic heating.
Bituminous: $79-86\%$ carbon, $46-31\%$ volatiles.
- Source for coke in metallurgy.
Sub-bituminous: $70-76\%$ carbon, $53-42\%$ volatiles.
- Industrial boilers.
Lignite: $65-70\%$ carbon, $63-53\%$ volatiles; high moisture.
- Low-grade industrial fuel.
Peat: <60\% carbon; entirely volatile matter.
- Technically not coal; historically briquetted for heating (e.g., Ireland).

Derived from dead plants & animals (esp. plankton + plant debris) in marine / large-lake environments.
Majority of organic matter recycled; only $\approx0.1\%$ escapes and becomes buried mud → potential source rock.

Continuous sediment accumulation adds weight → pushes source rock downward (subsidence) by a few $\text{m}$ to hundreds of $\text{m}$ per million years.
Produces sedimentary basins with layered strata.

At $\sim2000\;\text{m}$ depth, $T\approx100\;^{\circ}\text{C}$ : kerogen begins to release hydrocarbons.
Between $2000-3800\;\text{m}$ (“oil window”): kerogen → oil; deeper/ hotter conditions increasingly favor gas generation.
Composition trends:
- Predominantly animal kerogen ⇒ more oil than gas.
- Predominantly plant kerogen ⇒ more gas than oil.
With average sedimentation of $50\;\text{m}$ /Ma, takes $\approx60\;\text{Ma}$ for buried organic matter to become liquid hydrocarbons → underscores non-renewable status.

Hydrocarbons are lighter than formation water → migrate upward through pore spaces.
Two phases:
- Primary migration: expulsion from source rock into adjacent carrier beds.
- Secondary migration: ascent toward shallower strata until trapped or leaked at surface (seeps).

Must be porous (high void space) and permeable (interconnected pores) to store and transmit oil/gas.
Ex: sandstones, certain limestones, fractured carbonates; pumice is cited as a porous analogue.

Overlying layer of impermeable rock (shale, salt, dense limestone) prevents further vertical/lateral escape.
Absence of cap rock ⇒ hydrocarbons reach surface, oxidize, biodegrade; no commercial accumulation.

Hydrocarbons accumulate in closed spaces large enough for economic viability.
Two principal trap classes:
1. Structural Traps
- Caused by tectonic deformation (folding, faulting).
- Most common: anticlinal (dome-shaped) traps.
1. Stratigraphic Traps
- Formed by variations in sedimentation, without tectonic folding (e.g., pinch-outs, unconformities, reef buildups).
Contents & vertical arrangement
- Water at base (densest) → Oil layer → Gas at top (lightest).
- Possible scenarios: oil with dissolved gas; gas with condensate; oil + free gas cap.

Dissolved gas recovered as LPG (liquefied petroleum gas) → heating, transport fuel.
Condensate refined → naphtha (petrochemical feedstock) or kerosene (aviation fuel).

Even within traps, hydrocarbons may degrade via:
- Biodegradation (bacterial action) if fresh water intrudes.
- Oxidation along leakage pathways.
- Thermal cracking if temperature rises past oil stability window (oil → gas).

Involves three major energy conversions:
1. Chemical → Thermal: combustion of fuel raises steam.
2. Thermal → Mechanical (Kinetic): high-pressure steam drives turbine blades.
3. Mechanical → Electrical: turbine rotor spins electromagnetic generator → electricity.
Efficiency & environmental considerations link back to energy independence, economic viability, and the push for cleaner alternatives.