Next generation of LWD measurement technology honored

Logging while drilling (LWD) technology has recently taken a step forward with the introduction of Schlumberger’s EcoScope multifunction LWD service.

EcoScope, which reportedly integrates a full suite of formation evaluation, well placement, and drilling optimization measurements into a single 26-foot collar, was a Spotlight on New Technology Award winner at this year’s Offshore Technology Conference (OTC) in Houston, Texas.

The innovation with this technology lies in its use of a pulsed neutron generator (PNG), rather than a chemical-based source of neutrons such as AmBe, to generate neutrons on demand and at energy levels that are three times greater than those from chemical sources. This transmits neutrons into the formation at higher energies, allowing them to travel deeper into the formation and provide more counts on the detector. The EcoScope’s PNG is reportedly safer as well, in that it eliminates the risk inherent with transporting and handling a chemical-based neutron source.

Optimized formation evaluation and well placement

In addition, the PNG provides for new measurements not available in previous generations of LWD technology, such as elemental capture spectroscopy, which provides a lithology of the formation, mineralogy and matrix properties. Formation sigma, a salinity indicator, is also available, which provides an alternative to resistivity for determining hydrocarbon saturation. Neutron gamma density, which measures the gamma rays generated from neutron-formation interactions, can also be measured.

The technology also has multi-imaging capability that is useful for well placement decisions. For example, EcoScope provides real-time azimuthal density and gamma ray images that can be used to identify optimal well trajectory.

The tool has been described as a faster and more convenient method of downhole data measurement and transmission as well. Multiple LWD sensors have been integrated into a single collar, which reduces both the flat time associated with bottomhole assembly and the size of rathole that must be drilled to obtain useful formation information. In addition, all measurements take place close to the drill bit, which reduces invasion effects.

Optimized drilling

EcoScope provides several drilling optimization measurements including annular pressure while drilling (APWD), which allows one to monitor hole cleaning as well as leakoff-test and connection pressures. Caliper data, including density and multisensor ultrasonic measurements, provide visual representations of hole shape, which is subsequently used to calculate the volume of mud and cement needed. The technology also possesses three-axis shock and vibration measurements, which indicate whether drilling energy is being efficiently transferred to the rock or is instead being dispersed in the bottomhole assembly.

Data may be stored into a large memory capacity that can record 2 data points/ft at penetration rates of up to 450 ft/hr. Data is transferred to the driller on the surface in real time through Schlumberger’s TeleScope technology, a high-speed telemetry service connected to EcoScope.

Finally, the transmitted data is fed into the EcoView answer product, which assists in the data analysis, computing a petrophysical interpretation of the reservoir and requiring only water salinity as the input from the user. EcoView also uses 2D and 3D visualization tools to combine the multiple borehole images obtained with the petrophysical interpretation.