Seismic reservoir characterization of Utica-Point Pleasant Shale with efforts at quantitative interpretation — A case study: Part 1 Satinder Chopra 1 , Ritesh Kumar Sharma 1 , Hossein Nemati 2 , and James Keay 2 Abstract The Utica Shale is one of the major source rocks in Ohio, and it extends across much of the eastern United States. Its organic richness, high content of calcite, and development of extensive organic porosity make it a perfect unconventional play, and it has gained the attention of the oil and gas industry. The primary target zone in the Utica Play includes the Utica Formation, Point Pleasant Formation, and Trenton Formation intervals. We attempt to identify the sweet spots within the Point Pleasant interval using 3D seismic data, available well data, and other relevant data. This has been done by way of organic richness and brittleness estimation in the rock intervals. The organic richness is determined by weight % of total organic carbon content, which is derived by transforming the inverted density volume. Core-log petrophysical modeling provides the necessary relationship for doing so. The brittleness is derived using rock-physics parameters such as the Young’s modulus and Poisson’s ratio. Deter- ministic simultaneous inversion along with a neural network approach are followed to compute the rock-physics parameters and density using seismic data. The correlation of sweet spots identified based on the seismic data with the available production data emphasizes the significance of integration of seismic data with all other relevant data. Introduction The Marcellus Shale, which has become widely known as a source of natural gas in the eastern United States, is a thick formation that covers 95;000 mi 2 across the Appalachian Basin. The first well that used horizontal fracturing technology for completion in the Marcellus shale was drilled in 2006 by Range Resources (Pickett, 2015). The formation contains 500 Tcf of esti- mated recoverable gas reserves. Approximately 2000– 7000 ft below the Marcellus sits the geographically even more massive formation, the Utica Shale (Figure 1). Its areal extent is larger in that it spans over 170;000 mi 2 over portions of seven U.S. states (Pennsylvania, Ohio, West Virginia, New York, Virginia, Kentucky, and Ten- nessee) and across the border into Canada (Ontario) (EIA Report, 2017). The Utica Shale is considered a source rock for oil and natural gas, and it has been produced by conventional means in the overlying rock formations. According to a 2012 USGS report, the for- mation holds 940 million barrels of oil and approxi- mately 38 Tcf of natural gas (Kirschbaum et al., 2012), but with more drilling and production, these estimates have been revised and stand at 2 billion barrels of oil and 782 Tcf of natural gas (Cocklin, 2015). Eastern Ohio has now become a new drilling target and the focus of development activity in the Utica Shale play, followed by western Pennsylvania. The main rea- son for this is that the thermal maturity studies of the Utica Play Shales have indicated a northeast–southwest trend over eastern Ohio and western Pennsylvania, with a western oil phase window, a central wet gas phase window, and an eastern dry gas phase window (Ma- riani, 2013). The oil and wet gas phase windows span a large part of eastern Ohio and a small corner of northwestern Pennsylvania (Figure 2). In this respect, Utica is considered analogous to the Eagle Ford Shale in Texas. The other significant reason is that the Utica Play thins to the west in Ohio and becomes deeper and thicker as its dips to the east and southeast of the Appalachian Basin (Antoine and Frederic, 2016). In eastern Ohio, therefore, the Utica Play is the preferred target (over the Marcellus) due to its increased thick- ness within the oil and wet gas windows and the higher reservoir pressures present because of the extra 2000– 6000 ft of burial. One of the key elements for a successful shale re- source play is its thickness. The thickness of the Utica Shale in eastern Ohio is greater than 200 ft. As men- tioned earlier, it thins to the west and northwest, and the thickness increases to greater than 500 ft as it dips to the southeast. Historically, the early vertical wells that pierced through the Utica, and encountered natural fractures, either showed or produced hydrocarbons. It was not 1 TGS, Calgary, Canada. E-mail: satinder.chopra@tgs.com; rsharma@arcis.com. 2 TGS, Houston, Texas, USA. E-mail: mnemati@arcis.com; james.keay@tgs.com. Manuscript received by the Editor 31 July 2017; revised manuscript received 11 October 2017; published ahead of production 15 December 2017; published online 16 March 2018. This paper appears in Interpretation, Vol. 6, No. 2 (May 2018); p. T313–T324, 17 FIGS. http://dx.doi.org/10.1190/INT-2017-0134.1. © 2018 Society of Exploration Geophysicists and American Association of Petroleum Geologists. All rights reserved. t Technical papers Interpretation / May 2018 T313 Interpretation / May 2018 T313