environment where MWD technology had an economic advantage over conventional mechanical TOTCO devices, and lead to rapid developments, including LWD, to add Gamma and Resistivity, by the early 1980s. Available LWD measurements LWD technology was originally developed to guarantee at least a basic data set in case high cost exploration wells could not be logged with wireline. Although the aspiration was to partially or completely replace wireline logging, that was not the driver for early deployments, such as in the limited drilling season offshore in the Arctic summer in the early 1980s. Over the years, more of the measurements have been made available in LWD. Certain new measurements are also development in LWD only. The following is an incomplete list of available measurement in LWD technology. Natural gamma ray (GR) Total gamma ray Spectral gamma ray Azimuthal gamma ray Gamma ray close to drill bit. Density and photoelectric index Neutron porosity Borehole caliper Ultra sonic azimuthal caliper. Density caliper Resistivity (ohm-m) Attenuation and phase-shift resistivities at different transmitter spacings and frequencies. Resistivity at the drill bit. Deep directional resistivities. Sonic Compressional slowness (Δtc) Shear slowness (Δts) Borehole images Density borehole image Resistivity borehole image Formation tester and sampler Formation pressure Formation fluid sample Nuclear magnetic resonance (NMR) Seismic while drilling (SWD) Drillbit-SWD See also Geosteering Measurement while drilling References Petroleum production