Geosc 454 Geology of Oil & Gas Lab 8: Neutron density and porosity Objective: To quantify porosity and interpret pore fluids in the Appalachian basin from density logs. In this lab you will examine two sets of well logs from two wells in the Appalachian basin. Please turn in a type-written report answering the questions below. Pardee&Curtin#4: 1. The top of the Oriskany sandstone is at 6914 feet. Calculate the porosity of the Oriskany sandstone assuming the matrix density is 2.65 g/cc and the fluid density is 1.00 g/cc. You may “eyeball” a density for the sandstone, but report the number you choose, and show your work. 2. Is this the same value given by the density porosity log? Explain any difference. 3. Eighty feet of Tully limestone lie between 6280' and 6360'. Using the gamma ray log, define the depth interval of the shaley member of the Tully limestone. Explain the difference in the neutron porosity of the shaley and more carbonate rich portions of the Tully. 4. Use the gamma ray log to identify sandstone beds above the Tully limestone. How many beds do you find, and how many of these beds show the gas effect? What is the total cumulative thickness of these pay zones? If you were to stimulate one sandstone layer for production of gas, which would it be? (Give its depth.) Noxen#1 1. The black shale portion of the Marcellus is found between 7970' and 8265'. The Marcellus has three members from top to bottom: Oatka Creek, Cherry Valley, and Union Springs. Using the gamma ray log, identify the depth intervals for each of these three members. 2. Using the density and neutron porosity logs, determine the lithology of the Cherry Valley member. Explain. 3. Find an equivalent of the Tully limestone, which is greater than 10 feet thick here. At what depth is it located? How does the porosity change from shale to limestone and back to shale? 4. A typical neutron log for an Appalachian basin shale is found with the Hamilton Group at depths between 7200' and 7600'. Using this signal as a shale background, what evidence can you find for a gas charge throughout the upper Devonian section above the Tully limestone? At what depth is the largest gas reservoir above the Tully limestone?

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.