Practical Applications of NMR Technology Enhance Formation Evaluation, Testing and Completion Decisions

Abstract

Abstract In the last several years the use of borehole nuclear magnetic resonance (NMR) measurements has become more commonplace because the measurements are better understood by the service and operating companies and new applications have been developed. In most wells drilled in Indonesia, basic formation evaluation tools deliver sufficient data for evaluation. However, some wells can be more difficult to evaluate for any number of reasons. NMR measurements provide new petrophysical parameters that can help deal with difficulties such as low-contrast pay resulting from high irreducible water saturation or iron-rich minerals, varying or unknown formation water resistivity, and unknown mineralogy and grain density. Any of these issues can lead to inaccurate evaluations. Producibility is another issue that standard logs are not designed to address. Determining this property often requires drillstem tests or tests made with wireline formation testers. NMR measurements can give a cost-effective, continuous quantitative indication of rock quality and permeability in lieu of these tests. This paper will present several case studies from wells in Sumatra and Java where the basic NMR measurements have been used by asset teams to solve difficult evaluation problems. The NMR measurements have been integrated into a full volumetric evaluation of the reservoirs. These examples will cover clastic, carbonate and basement (weathered granite) formations. Production, test results and core analyses have been used to validate the evaluations.