Logging While Drilling (LWD) tools with natural radioactive sources present risks to drilling and field development teams, due to the safety hazards inherent to the use of natural radioactive sources in the tools. If any natural radioactive source is left in the hole due to drilling conditions, a complex procedure is required to abandon the hole and sidetrack it.
Recently, a new sourceless LWD logging technique (NeoScope), which incorporates Pulsed Neutron Generators (PNG), was introduced to Wafra Joint Operations (JO).
The new technique provides multiple measurements (Resistivity / Density / Neutron / Sigma / Spectroscopy) from a tool located in a single 26 feet long collar. The PNG* uses electrical power generated from the Measurement-While Drilling (MWD) turbine to generate a large cloud of fast neutrons. These fast neutrons interact with the formation atoms to generate formation hydrogen index, Sigma, and spectroscopy data. In addition, the fast neutron interactions generate a secondary gamma ray cloud that can be used to measure formation density (similar to standard density measurement).
The first successful use of this tool in Wafra Joint Operations was in the first time for in South Fuwaris Field. The tool was run in a pilot hole with an inclination of 60°, cutting Ratawi Limestone and Ratawi Oolite reservoirs. The acquired data were excellent compared to conventional LWD data.
The proven success of this new technology provides risk mitigation / elimination for future operations. Extra care should be taken when using natural radioactive sources while drilling. The use of Sourceless LWD technology is a good risk elimination. Proper planning is required to ensure tool availability (only available for 8 ½” hole)