Case study - Human Interaction with the Rock Cycle (Natural Gas)

  • Natural gas is a fossil fuel that accounts for 40% of our primary energy demand

  • Formed from decayed animal and plant remains most often in marine environments

  • Over millions of years and due to great heat and pressure, bacteria break down the organic materials (decayed animals and plant remains) into natural gas droplets

  • The natural gas is then squeezed out and travels upwards through permeable rock before eventually meeting a trap (e.g. an anticline with impermeable rock on top)

  • Human interaction:

  1. Geologists first locate anticlines that potentially have gas deposits underneath them

  2. Small explosions are set off, vibrating the ground

  3. These shake the gas, allowing for 3D mapping of the field

  4. If gas is present, further tests are carried out to determine exact size and extent

  • Gas production in Ireland:

  1. Two main sources of gas; both found offshore (under the sea)

  2. The first is the Kinsale Head gas field (Co. Cork); discovered in 1971 and was in production from 1978. Its main platform was located in 100m of water with the gas flowing from 1km below the sea bed. The gas was pumped onshore to Cork Harbour via an underwater pipeline. Two additional gas deposits were later found nearby in the Seven Heads area; they were then connected to the main gas terminal. However, they were not as fruitful as had been hoped and quickly became exhausted. Decommissioning & dismantling began in late 2020, with the entire gas field expected to be closed by the end of 2023

  3. The second is the Corrib gas field (Co. Mayo). It is located approx 70km off the coast where the water is over 300m in depth. The gas field itself