Deep resistivity \u201cturnover\u201d effect at oil generation \u201cpeak\u201d in the Woodford Shale, Anadarko Basin, USA

Ting Wang,Jacobi David

doi:10.1007/s12182-019-00370-8

Abstract

The Devonian Woodford Shale in the Anadarko Basin is a highly organic, hydrocarbon source rock. Accurate values of vitrinite reflectance (Ro) present in the Woodford Shale penetrated by 52 control wells were measured directly. These vitrinite reflectance values, when plotted against borehole resistivity for the middle member of the Woodford Shale in the wells, display a rarely reported finding that deep resistivity readings decrease as Ro increases when Ro is greater than 0.90%. This phenomenon may be attributed to that aromatic and resin compounds containing conjugated pi bonds generated within source rocks are more electrically conductive than aliphatic compounds. And aromatic and resin fractions were generated more than aliphatic fraction when source rock maturity further increases beyond oil peak. The finding of the relationship between deep resistivity and Ro may re-investigate the previously found linear relationship between source rock formation and aid to unconventional play exploration.

Highlights

In a lot of early-stage unconventional shale play explorations, several key geochemical parameters, including organic richness (TOC) and thermal maturity, are need to be known to evaluate potential unconventional shale play (Comer 2005; Jarvie 2011)
This study focuses on hydrocarbon source rock thermal maturity, which is scaled by vitrinite reflectance (Ro) in practice
Accurate values of vitrinite reflectance (Ro) present in the Woodford Shale penetrated by 52 control wells were measured directly

Summary

Introduction

In a lot of early-stage unconventional shale play explorations, several key geochemical parameters, including organic richness (TOC) and thermal maturity, are need to be known to evaluate potential unconventional shale play (Comer 2005; Jarvie 2011).

Methods

Results

Conclusion