Group 3 - Coal, Petroleum and Petrology (1)

Coal, Petroleum, and Petrology

What Is Coal?

  • Definition: Coal is a black, rock-like material that can burn.

  • Formation: Formed from ancient plants/vegetations buried under dirt and rock for millions of years.

    • Coalification: A combustible sedimentary rock formed through a process known as coalification.

  • Uses: Commonly used as fuel for electricity and heat, but produces pollution when burned.

Coalification Process

  • Definition: The transformation process of plant material into coal.

    • Steps: Plant matter is buried under layers of rock and soil, where heat and pressure initiate chemical changes that compress plant material into peat, which eventually turns into coal.

Stages of Coalification

  • Stages:

    1. Peat

    2. Lignite

    3. Sub-bituminous

    4. Bituminous

    5. Anthracite

Coal Layers or Seams

  • Composition: Mainly carbon, with hydrogen, oxygen, nitrogen, sulfur, and small amounts of other materials including water and rock fragments.

Types of Coal

  • Brown Coal:

    • Forms at an earlier stage of coalification.

    • Lower energy content due to lower carbon content and higher moisture content.

    • Produces more smoke and pollutants when burned.

    • Cheaper but less efficient than black coal.

  • Black Coal:

    • Harder than brown coal with higher energy content.

    • Used primarily in thermal (steaming) power generation and metallurgical (coking) processes.

    • Attracts higher prices due to low sulphur and phosphorus contents and relative scarcity.

Similarities and Differences of Brown and Black Coal

  • Similarities:

    • Both are fossil fuels derived from ancient plant remains.

    • Both serve as energy sources mined from underground or surface deposits.

    • Both are non-renewable resources.

  • Differences:

    • Age and composition; black coal is harder and more energy-dense than brown coal.

Coal Reserves

  • Definition: Coal reserves are discovered through exploration involving geophysical surveys.

  • Mining Methods:

    • Underground Mining:

      • Accounts for 60% of world production; involves deep-seated tunnels or shafts to extract coal.

      • Higher risks with cave-ins and gas explosions but lower surface footprint.

    • Open Cut Mining:

      • Economic when deposits are near the surface; known as open-pit mining.

      • Removes large amounts of overburden to expose coal seams, leading to habitat destruction and pollution, but poses fewer risks to miners.

Petroleum

  • Definition: Mineral oil that is an inflammable liquid composed mainly of hydrocarbons.

    • Crude Petroleum: Consists of a mixture of hydrocarbons including paraffin and its derivatives.

Utilization of Petroleum

  • Mainly used for motive power and transportation.

  • Easily transported, emits minimal smoke, and leaves no ash.

  • Serves as raw materials for various petrochemical products.

Origin and Occurrence of Petroleum

  • Derived from the breakdown of organic materials, primarily found in sedimentary basins and shallow depressions.

  • Most reserves are linked to anticlines and faults in sedimentary rock layers.

Pre-requisite Conditions of Oil Reservoirs

  • Porosity: To hold a sufficient amount of oils.

  • Permeability: For discharging oil/gas when a well is drilled.

  • Trapping: Oil must be trapped in rocks with small spaces and covered to prevent leakage.

Petroleum Reserves and Production

  • Historical Estimates:

    • 1982: Estimated reserves at 468 million tons.

    • 1984: Reserves increased to 500 million tons.

    • 2002: Only about 25% of hydrocarbon reserves confirmed.

  • Current Estimates: India's hydrocarbon resource base is estimated at 28 billion tons (70% oil, 30% gas).

Refining and Imports

  • Crude oil requires refining to eliminate impurities.

  • First refinery established in 1901 in Digboi, Assam; refined products include kerosene, diesel, petrol, lubricants, and bitumen.

  • Domestic consumption has constantly outpaced production, necessitating imports.

Petrology

  • Definition: From the Greek “petra” meaning rock and “logos” meaning study; a branch of geology focusing on rocks' origin, composition, and structure.

Branches of Petrology

  • Igneous Petrology: Studies composition and texture of igneous rocks like granite and basalt.

  • Sedimentary Petrology: Focuses on sedimentary rocks like sandstone and limestone.

  • Metamorphic Petrology: Examines metamorphic rocks such as slate and marble.

  • Experimental Petrology: Uses high pressure and temperature apparatus to analyze geochemistry.

Types of Rock

  • Igneous Rock: Formed from cooled magma.

  • Sedimentary Rock: Formed from compressed and hardened sediment.

  • Metamorphic Rock: Formed under high temperature and pressure inside the earth.

Rock Cycle

  • Process:

    • Igneous rock erodes into sediment, forming sedimentary rock.

    • Sedimentary rock transforms into metamorphic rock under heat and pressure.

    • Metamorphic rock becomes magma, erupts, and cools into Igneous rock.

What Is Magma?

  • Definition: Molten or semi-molten rock found beneath the Earth's surface, with temperatures from 700 to 1,300 degrees Celsius.

  • Lava: Magma that reaches the Earth's surface.

Composition and Formation of Magma

  • Composed primarily of silicate minerals, along with elements like aluminum, iron, calcium, sodium, potassium, and magnesium, formed through heating and pressure in the earth's mantle.

Types of Magma

  • Basaltic Magma: Contains iron and magnesium; darker in color.

  • Andesitic Magma: Thicker, more silica, potentially explosive.

  • Rhyolitic Magma: Highly viscous, contributes to explosive eruptions.

Classification of Magma

  • Varies by composition and temperature, affecting viscosity and potential for eruptions.