Sourceless Porosity and Permeability Estimation with NMR Logs While Drilling in a Carbonate Reservoir: A Case Study

Abstract

AbstractSourceless porosity estimation has become more attractive because of evolving government regulatory and HSE requirements. The use of wireline nuclear sensors and their HSE procedures have a 50-year history, while nuclear sensors for logging while drilling share the last 20 of those years.Recently, the potential of using non-nuclear methods for porosity estimation has been explored in an offshore Abu Dhabi carbonate sequence. This paper presents a case study of nuclear magnetic resonance (NMR) logs while drilling, in comparison to conventional density and neutron logs using radioactive chemical sources. NMR T1 porosities were also compared to laboratory core results. Two approaches are investigated: Estimated hydrogen-index correction to NMR moveable-fluid volume using core-normalized porosities.An insight into an integrated NMR-acoustic approach, using the two sensor measurements to derive a corrected porosity.A workflow is proposed for optimized job planning, operational procedures, data-acquisition parameters, and interpretation techniques. Permeability estimation with NMR is discussed, and a selection of methods are considered and contrasted to laboratory core permeability and wireline formation-tester results.This paper explores the potential for sourceless porosity measurements through NMR and acoustic/NMR measurements in an offshore Abu Dhabi carbonate sequence in compliance with the HSE standards and government regulations, where the need for reconsidering reservoir characterization through sourceless porosity options will continue to grow.