Conventional Log Evaluation in Organic Shales

Cody Knepper
NuTech

There are various methods available to the geoscientist to evaluate the properties of organic shale reservoirs. In a new well, one might elect to add a modern geochemical tool to their logging suite, or go with the absolute best way to evaluate organic shale reservoirs, retrieval and analysis of whole core. After all, ―The rock is the rock‖, but how to gauge risk and potential before drilling or leasing?

There are thousands of available conventional wireline logs over or-ganic shale zones. Access to this data is cheap & easy compared to drilling and coring a well, but can one believe the log response in unconventional reservoir rock? How can the geoscientist maximize the existing pool of log data to make more informed decisions about organic shale potential?

Accurate evaluation of organic shale reservoirs is possible with proper use of existing conventional Gamma Ray/Resistivity/Porosity log data. Several examples of organic shale analyses will be shown, with particular focus on the Woodford shale. Organic shales present unique petrophysical challenges that are not seen in conventional reservoir rock. The effects of kerogen and maturity on log response and the different ways to correct data will be discussed. With proper calibration & execution, a strong petrophysical model can make geo-chemical logs unnecessary, and eventually replace the need for cor-ing. Large scale petrophysical analysis combined with mapping has proven to be an effective tool for getting ahead of the competition in these highly competitive plays.

AAPG Search and Discovery Article #90184 © AAPG Woodford Shale Forum, Oklahoma City, Oklahoma, April 11, 2013