ENV 100 Chap.10 Energy Resources and Future Choices
Energy Resources and Future Choices
This chapter compares the geological chains behind coal, oil and gas, and geothermal energy. Formation, burial, maturation, migration, reservoir, seal, heat, fractures, fluid circulation, and reinjection determine what is available. Life-cycle boundaries then expose trade-offs in emissions, reliability, land, water, imports, and local geology.
What this chapter covers
- 01
Coal formation and rank
- 02
Petroleum systems
- 03
Reservoirs and seals
- 04
Geothermal heat and permeability
- 05
Production and reinjection
- 06
Energy-transition trade-offs
Worked example · free
Screen a geothermal prospect
- +1Confirm an accessible heat source.
- +1Test fractures and fluid pathways.
- +1Assess chemistry and drilling risk.
- +1Evaluate reinjection and induced effects.
Key terms
- Coal rank
- Coal rank describes the degree of transformation of buried plant material with heat and pressure.
- Source rock
- A source rock contains organic matter capable of generating hydrocarbons during burial and heating.
- Reservoir rock
- A reservoir rock has pore space and connectivity that can store and transmit fluids.
- Geothermal system
- A geothermal system combines accessible heat, fluid, and permeability.
- Reinjection
- Reinjection returns produced geothermal fluid to the subsurface to manage pressure and disposal.
Energy Resources and Future Choices FAQ
Why is sedimentary geology important for fossil fuels?
Organic-rich source material, burial history, migration pathways, porous reservoir rock, and an effective seal must align. The presence of sedimentary rock alone does not establish a petroleum system.
What controls a geothermal resource?
Temperature, depth, permeability, fractures, fluid supply, chemistry, drilling access, and reinjection behaviour jointly control production. Strong heat with poor connectivity can remain difficult to use.
How should energy options be compared?
Define the service and include extraction, construction, transport, operation, emissions, reliability, water, land, and closure. Labels such as renewable or fossil do not replace a consistent life-cycle boundary.
Why does a petroleum system need a seal?
Generation and migration do not guarantee an accumulation. A connected reservoir must receive the fluids, and a sufficiently low-permeability seal must impede further movement. Timing and geometry also matter because the trap must be available when migration occurs.
What is the purpose of reinjection?
Returning produced geothermal fluid can manage disposal and support reservoir pressure, but it must be designed around permeability, chemistry, temperature, and fracture response. Monitoring is needed for cooling, pressure change, mineral deposition, and possible induced effects over continued operation.
Assessment move
Draw three distinct geological systems before comparing energy labels. For coal, trace plant material through burial, compaction, heating, and changing rank, and relate the resource to the sedimentary setting in which seams form. For oil and gas, build a complete petroleum-system diagram containing organic-rich source rock, maturation, migration pathway, porous reservoir, connected pore space, and effective seal.
Remove one element at a time and explain why the system may fail. For geothermal energy, sketch heat, fluid, fractures or permeability, production, surface use, and reinjection. Mark the measurements that establish temperature and those that establish deliverability; heat alone is not a flow test.
Build a common comparison table with service delivered, geological requirement, extraction or drilling, construction, operation, emissions, reliability, land, water, waste, imported inputs, closure, and local risk. Keep the boundary identical across coal, hydrocarbons, and geothermal options so a favourable label does not hide a stage.
Add time scale and location because a resource that is technically present may not be accessible, economic, or acceptable under the stated conditions. Retrieval practice should use conditional cases. Given a porous rock without a seal, diagnose the petroleum problem. Given high heat with poor permeability, state which evidence is missing. Given a renewable classification, list the life-cycle observations still required.
Practise distinguishing resource from reserve and formation from production. Write one paragraph that explains a geological chain and another that evaluates a choice; these are different tasks and need different evidence. For reinjection, trace pressure support, fluid disposal, cooling, chemistry, and possible induced effects rather than calling it automatically sustainable.
Before the test, redraw all three systems from blank paper and annotate one failure point in each. Then write a symmetric comparison that uses the same service unit and indicators. Finish with a local-conditions audit: depth, heat, pore space, connectivity, fluid, chemistry, seal, water setting, and monitoring.
The conclusion should state what makes an option feasible, what limits it, and which observation could change the judgement.
