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?