How Organic Carbon Content and Thermal Maturity Affect Acoustic Properties (and Ultimately Seismic Response) In A Shale Gas / Oil Formation: Woodford Shale, Permian Basin

摘要

Organic carbon content and thermal maturity are critical to the evaluation of shale gas and shale oil plays, determining the productivity of the formation and type of hydrocarbons that are produced. In this analysis, we demonstrate that these parameters also affect acoustic properties; thus, well logs and potentially seismic data can be inverted to estimate organic richness and maturity. Our study is based on data from two cored wells in the Woodford Formation, Permian Basin, west Texas, that had been previously studied to develop sedimentological and geochemical models for black shale deposition. The KCC 503 well is relatively shallow, and the Woodford Shale here has a maturity of 0.71% Ro, just entering the oil window. The RTC 1 well is relatively deep, and the Woodford in this well has a maturity of 1.48% Ro, in the wet gas window. In our analysis, we link rock composition, including total organic carbon (TOC) content and thermal maturity to data on p-wave (VP) and s-wave (VS) velocities and density and derivative properties including Vp/Vs ratios, impedance, geomechanical parameters including Poisson’s Ratio and Young’s Modulus and Lamé parameters mu and lambda. We then test whether stratigraphic intervals within the Woodford can be geophysically distinguished and potentially mapped with seismic data.