Traditionally, measuring formation density requires a high-activity radioactive source. An alternative method known as sourceless neutron gamma density (SNGD) uses a pulsed-neutron generator that eliminates the need for chemical radioactive sources. However, in the past SNGD encountered limitations under certain conditions. Leveraging advancements in tool hardware and digital modeling capabilities, NovoSphere sourceless formation evaluation logging-while-drilling service was developed to address these challenges. This new service was used to measure formation density in a geologically complex clastic zone characterized by variable lithology. The well features a long horizontal section crossing a sequence of interbedded shales before reaching a sandstone reservoir. This sandstone section is relatively homogeneous, and is split by an intermediate shale body, into an oil-bearing and a water-bearing reservoir. These heterogeneous layers present considerable challenges for accurate formation evaluation and density measurement.
A strong correlation was observed between the SNGD in the NovoSphere service and the conventional gamma gamma density (GGD) measurements along the horizontal section, providing consistent results across different formation and fluid conditions.
