Application of Pulsed Neutron Mineralogy Tools to the Evaluation of Evaporite Deposits

In recent years, the oilfield services industry has developed logging tools specifically designed for downhole measurement of formation elemental weights. These tools have been developed in response to the requirement for accurate quantification of challenging lithologies now often found in hydrocarbon-bearing formations, especially “shale” prospects. Many other subsurface industries are also interested in precise subsurface elemental and mineralogical compositions—in particular, industries concerned with mineral extraction. Traditionally, these industries have relied on conventional techniques such as regional geological knowledge, seismic surveys, correlations inferred from existing wells, and cuttings and core analysis. Many of these have associated disadvantages in terms of high uncertainty, poor resolution, limited data, cost, and time to obtain results. We propose that modern downhole elemental spectroscopy tools can fulfil many requirements of these industries. In this paper we present the application of the Baker Hughes Formation Lithology Explorer (FLeXsm) pulsed neutron elemental spectroscopy service for evaluating a complex Northern European evaporite formation to identify and quantify magnesium-bearing horizons for solution mining. We then compare the results to conventional techniques, and describe the advantages over these techniques. Furthermore, we present a workflow optimised for quantification of in-situ mineralogy and propose applications for this technology in non-hydrocarbon subsurface industries.