Research Article Rational Rock Physics for Improved Velocity Prediction and Reservoir Properties Estimation for Granite Wash (Tight Sands) in Anadarko Basin, Texas Muhammad Z. A. Durrani, 1 Keith Willson, 2 Jingyi Chen, 1 Bryan Tapp, 1 and Jubran Akram 3 1 Department of Geosciences, University of Tulsa, 800 South Tucker Drive, Tulsa, OK 74104, USA 2 Newield Exploration Company, 101 E 2nd Street, Tulsa, OK 74103, USA 3 Department of Geoscience, University of Calgary, 2500 University Dr. NW, Calgary, AB, Canada T2N 1N4 Correspondence should be addressed to Jingyi Chen; jingyi-chen@utulsa.edu Received 22 January 2014; Revised 27 June 2014; Accepted 9 July 2014; Published 26 August 2014 Academic Editor: Rudolf A. Treumann Copyright © 2014 Muhammad Z. A. Durrani et al. his is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. Due to the complex nature, deriving elastic properties from seismic data for the proliic Granite Wash reservoir (Pennsylvanian age) in the western Anadarko Basin Wheeler County (Texas) is quite a challenge. In this paper, we used rock physics tool to describe the diagenesis and accurate estimation of seismic velocities of P and S waves in Granite Wash reservoir. Hertz-Mindlin and Cementation (Dvorkin’s) theories are applied to analyze the nature of the reservoir rocks (uncemented and cemented). In the implementation of rock physics diagnostics, three classical rock physics (empirical relations, Kuster-Toks¨ oz, and Berryman) models are comparatively analyzed for velocity prediction taking into account the pore shape geometry. An empirical ( P - S ) relationship is also generated calibrated with core data for shear wave velocity prediction. Finally, we discussed the advantages of each rock physics model in detail. In addition, cross-plots of unconventional attributes help us in the clear separation of anomalous zone and lithologic properties of sand and shale facies over conventional attributes. 1. Introduction For the last sixty years, the Anadarko Basin has been a proliic setting for oil and natural gas explorations in North America largely focused on two natural gas plays: the Woodford shale and the Granite Wash. he exploration activity in the Granite Wash play has increased over the last decade. he Granite Wash play straddles the Oklahoma-Texas border and covers more than six counties (Hemphill, Roberts, Wheeler, Beckham, Roger Mills, and Washita) (Figure 1). he play is a series of stacked potential play zones, each of which should be treated diferently and requires a more geophysically focused approach to achieve success. Due to the low porosity and permeability, cementation and the presence of microfractures make each interval a slightly diferent nut to crack [1]. Desmoinesian age (Granite Wash) deltaic sediments relect a long diagenetic history, with extensive cementation by quartz and calcite. Postcementation secondary dissolu- tion and leaching of calcite cement and framework grains (e.g., feldspar, rock fragments) produced/recovered current porosity in the facies [2]. he geological and depositional factors such as lithology, luid, and porosity (LFP) directly afect the elastic properties of the rock and subsequently the seismic responses. Because of the complex nature of Granite wash, it has mystiied geologists and petrophysicists as well as geophysicists alike, thus making geophysical experimental and numerical studies extremely challenging. he solution to the problems requires rational rock physics to tackle complex mineralogy and poor under- standing of diagenetic conditions to reexamine the current understanding of the reservoir properties of Granite Wash. Rock physics bridges the reservoir quantitative (e.g., P- and S-wave velocities, impedances, and elastic moduli) and reservoir qualitative (e.g., porosity, clay content, lithology, Hindawi Publishing Corporation International Journal of Geophysics Volume 2014, Article ID 209351, 15 pages http://dx.doi.org/10.1155/2014/209351