Understanding Your Elemental Data Sources — What are the Limitations and Advantages of Different Elemental Data Acquisition Methods?

Abstract

Over the last 10 years the use of inorganic elemental data to characterize and correlate sedimentary sequences both in academia and within the oil and gas industry has increased dramatically. The increase in demand for elemental data has come hand-in-hand with an increase in the number of different analytical options available to generate this type of dataset; from lab-based ICP (inductively-coupled plasma) OES and MS (Optical Emission spectroscopy and Mass Spectroscopy) to portable and hand-held XRF (X-ray fluorescence) instruments. In this study we investigate the type and quality of data derived from different analytical methodologies (ICP, XRF) and instrument types (hand-held, bench-top or laboratory). Additionally, we demonstrate the efficacy of different instrumentation in the acquisition of elemental data from core, cuttings and powdered/pelleted samples. Through a series of case studies from several North American shale plays, we discuss the best strategies for interpreting and assessing data quality from full lab-based XRF and ICP-OES/MS datasets through to those generated from hand-held XRF instruments, where lighter major elements like sodium are not acquired. Furthermore, the level of confidence that can be placed on key elements when providing an interpretation from these datasets will also be addressed, specifically where elemental data is used to generate mineral models or where trace elements such as Mo, V, Ni and U are used to assess anoxic conditions at the time of deposition. In many cases, these parameters are used to refine target zones within a shale play and are best put to use when integrated with other mineralogical or petrophysical datasets. As users of these data, it is important to understand the confidence that can be placed on different bulk elemental datasets especially when using different sample selection, preparation and analytical methodologies.

AAPG Datapages/Search and Discovery Article #90216 ©2015 AAPG Annual Convention and Exhibition, Denver, CO., May 31 - June 3, 2015