Geochemistry Physics Coursework Example | Topics and Well Written Essays - 750 words

Geochemistry Physics - Coursework Example Mechanical infiltration also plays a vital part in the downward movement of clay sized particles. Carbonate rocks such as limestone are affected by inversion, recrystallisation and grain growth as well. Typical processes that affect carbonate rocks are (sequentially) biochemical degradation, polycondensation and insolubilisation. 2. Why is the smectite to illite transition important in the process of petroleum formation? The smectite to illite transition is an important diagenesis reaction especially for shales with progressive burial. This transformation has the potential to flush hydrocarbons from various shales, accelerating the generation of hydrocarbons, producing high pore fluid pressures and for provision of various cementation agents to different sandstones. 3. How would you expect the alkane/alkene ratio to change as a hydrocarbon mixture matures over geological time, and why? The alkane/alkene ratio would tend to decrease with time as a hydrocarbon mixture matures over geol ogical time. This would take place as the biodegradation process would tend to remove alkanes so that the hydrocarbon mixture moves towards aromatics. 4. ... 5. What is a geochemical fossil? A geochemical fossil is the remains of any organic object that has been transformed by diagenesis into a fossilised state. The resulting fossilised state may not have been able to preserve the original structure of the fossilised object. 6. Explain how crude oils can be grouped based on their sulfur content. Crude oils are classified using sulphur content such that low sulphur content crude oils are known as â€Å"sweet† while high sulphur content crude oils are known as â€Å"sour†. Typically low sulphur content crude oils are preferred because sulphur tends to display acidic behaviour. PART 2. 1. Draw the van Krevelen diagram and explain how it illustrates several important facts concerning the formation of petroleum. A van Krevelen diagram is generally plotted to evaluate the origins and maturity levels of kerogen and petroleum content. The van Krevelen diagram plots the ratio of hydrogen to carbon against the ratio for oxygen to carb on. Figure 1 - van Krevelen diagram sourced from (Monash University, 2008) Looking at the diagram above, it becomes obvious that the van Krevelen diagram differentiates between various hydrocarbon products depending on certain regions on the plot. The formation of liquid petroleum can be seen as resting between oxygenated products and gas products which signifies petroleum formation. Additionally the van Krevelen diagram illustrates the evolution paths of various kerogens through the various paths shown on the plot. The plot above shows four possible paths (I, II, III and IV) that denote increasing burial. Based on this the particular mix of petroleum obtainable is arrived at. 2. What is