5. Depositional environment II

6. Depositional environments III A petroleum company has found a prospective reservoir unit. It seems to be a sedimentological trap, so only sedimentological considerations are needed in order to estimate its size. Based on a test drilling, the company knows that the reservoir unit is composed of ooid sand. The seismic data indicates a sedimentary system in the surrounding that transits from shallow-marine to deep-marine environments. The coastline is estimated to lie in an E-W direction with the land in the south and the deep-marine area in the north.

4. Depositional environment I The log below is from an outcrop of Triassic deposits in Germany. Suggest a depositional environment based on the log description. Explain your suggestion. Circles with arrows indicate measured current directions. In the grain-size legend, f= very fine to fine, m = medium, g = coarse to very coarse (barely readable). 4a. Describe the 3-dimentional morphological shape that you would assume the reservoir to have. Explain why you suggest that shape. 4b. In which compass direction(s) from the test drill would you continue looking for the reservoir unit? Why? 4c. What rock type(s) would you expect to limit the reservoir laterally (the answer "limestone" is too unspecific)? Why?

5. Depositional environment II Interpret the depositional environment for this sedimentological sequence of North American Ordovician deposits. Explain how the sedimentary environment has changed through time and what makes you suggest the specific environmental change(s).

3. Stratigraphy Assume that the five wells A to E are from a siliciclastically dominated basin. The horizontal distance between each well is few kilometeres. For each well, the left curve is a gamma-ray log and the right one is a sonic log. Fluvial deposits are dotted and shallow-marine ones are white. The black line is a marker bed that has been defined as a time horizon with palaeontological data. 3a. Correlate the wells lithostratigraphically. 3b. Mark positions of discordances. 3c. Can any of the fluvial sediment bodies be used as time markers? If yes, which one(s)? Explain your answer.

1. Water Assume that you live in a house very close to the seashore in a coastal area. Suddenly you notice that the tap water has a salty taste. Explain the change in water taste.

2. Maturity of coal A coal company has found a thick horizon of anthracite. The company wants to estimate the maturity of the coal in more detail. 2a. How would you expect the chemical composition to vary in general from less to more mature coal? 2b. The company wants to combine chemical investigations with an independent method to get more reliable results on the maturity of the anthracite. Suggest an alternative method and explain how it works.