Document Type : Research Paper


1 Ph.D. Candidate, School of Engineering, University of Portsmouth, Portsmouth, UK

2 Assistant Professor, School of Engineering, University of Portsmouth, Portsmouth, UK

3 M.S. Student, Faculty of Earth Sciences, Kharazmi University, Tehran, Iran


Since the development bloom in unconventional reservoirs in North America, total organic carbon (TOC) has become a more essential parameter, as the indicator of the efficiency of these reservoirs. In this paper, by using conventional well logs and NMR log data, the TOC content of an unconventional reservoir in West Africa is estimated. Passy’s, Issler’s, and Schmoker’s methods were used as indirect wireline methods to estimate TOC content, along the well paths. Afterward, NMR log data, as a direct method, was used to provide more precise calculations of TOC. Both methods showed almost similar trends, with the NMR method indicating lower values for the TOC. Then, an adjusted Schmoker equation was proposed, which showed the best fit between NMR and conventional well logs results. By using the equation, the TOC content was calculated in three other wells, where NMR data were unavailable. The results were then used to prepare a 3D model of the TOC distribution, within the reservoir.






Main Subjects


Alshakhs, M. and Rezaee, M.R., A New Method to Estimate Total Organic Carbon (TOC) Content, an Example from Goldwyer Shale Formation, The Canning Basin, The Open Petroleum Engineering Journal, Vol. 10, p. 118–133, 2017.
Crain’s Petrophysical Handbook, (Accessed 03.03.19). (Http://Www.Spec2000.Net/11-Vshtoc), 2019.
Gonzalez, J., Lewis, R., Hemingway, J., Grau, J., Rylander, R., and Schmitt, R., Determination of Formation Organic Carbon Content Using a New Neutron-induced Gamma Ray Spectroscopy Service That Directly Measures Carbon, 54th Annual Logging Symposium, New Orleans, Louisiana, 22–26 June, 2013.
Harris, N.B. and Tucker, G.E., The Organic Carbon Record of Lower Cretaceous Rift Lakes, Congo Basin, Africa: A Record of Rift Topography, Soil Development and Topography: GSA Annual Meeting in Seattle, Washington, USA, 2017, DOI: 10.1130/abs/2017AM-299095.
Harris, N.B., Toca Carbonate, Congo Basin: Response to an Evolving Rift Lake, Petroleum Systems of South Atlantic Margins: AAPG Memoir 73, p. 341–360, 2000.
Issler, D.R., Hu, K., Bloch, J.D., and Katsube, J.T., Organic Carbon Content Determined from Well Logs: Examples from Cretaceous Sediments of Western Canada: Geological Survey of Canada, Open File 4362, 2002.
Jarvie, D.M., Hill, R.J., Ruble, T.E., and Pollastro, R.M., Unconventional Shale-gas Systems: the Mississippian Barnett Shale of North-central Texas as One Model for Thermogenic Shale-gas Assessment, American Association of Petroleum Geologists Bulletin, Vol. 91, p. 475–499, 2007.
Ma, Y.Z. and Holditch, S.A., Unconventional Oil and Gas Resources Handbook: Evaluation and Development, Elsevier Science and Technology, 550 p., 2015.
Mahmoud, A.A., Elkatatny, S., Mahmoud, M., Omar, M., Abdulraheem, A., and Ali, A., Determination of the Total Organic Carbon (TOC) Based on Conventional Well Logs Using Artificial Neural Network, International Journal of Coal Geology, Vol. 11, p. 1–15, 2017.
Passey, Q.R., Bohacs, K.M., Esch, W.L., Klimentidis, R., and Sinha, S., From Oil-prone Source Rock to Gas-producing Shale Reservoir: Geologic and Petrophysical Characterization of Unconventional Shale-gas Reservoirs, Society of Petroleum Engineers, SPE 131350, 29 p., 2010.
Passey, Q.R., Creaney, S., Kulla, J.B., Moretti, F.J., and Stroud, J.D., A Practical Model for Organic Richness from Porosity and Resistivity Logs, American Association of Petroleum Geologists, AAPG Bulletin, 14 (August), p. 1777–1794, 1990.
Peters, K.E., Guidelines for Evaluating Petroleum Source Rock Using Programmed Pyrolysis, American Association of Petroleum Geologists Bulletin, Vol. 70, p. 318–329, 1986.
Schmoker, J.W. and Hester, T.C., Organic Carbon in Bakken Formation, United States Portion of Williston Basin, American Association of Petroleum Geologists Bulletin, Vol. 67, p. 2165–2174, 1983.
Steiner, S., Ahsan, S. A., Raina, I., Dasgupta, S., and Lis, G. P., Interpreting Total Organic Carbon in Source Rock Oil Plays, Society of Petroleum Engineers, 2016. Doi:10.2118/183050-MS
Tabatabaei, S.M., Kadkhodaie-Ilkhchi, A., Hosseini, Z., and Moghaddam, A.A., A Hybrid Stochastic-gradient Optimization to Estimating Total Organic Carbon from Petrophysical Data: A Case Study from Ahwaz Oilfield, SW Iran, Journal of Petroleum Science and Engineering, Vol. 127, p. 35–43, 2015.
Tissot, B. P. and Welte, D. H., Petroleum Formation and Occurrence, a New Approach to Oil and Gas Exploration, Berlin Heidelberg New York Springer Verlag, Vol. 20, p. 428–428, 1978.
Xiong, H., Wu, X., and Fu, J., Determination of Total Organic Carbon for Organic Rich Shale Reservoirs by Means of Cores and Logs, Society of Petroleum Engineers, 2019, Doi:10.2118/196000-MS