
The Downhole Logging area on Core Deck	Kerry Swain (Logging Engineer, Schlumberger Offshore Services) oversees the storing of the downhole instruments after logging operations. (Credit: Bill Crawford, IODP JRSO) [Photo ID: exp356_045]	Schlumberger Logging Engineer, Kerry Swain, (in blue) supervises the assembly of a tool string used in downhole logging operations. The tool string consists of different types of sensors that are assembled one after another and then lowered into the drill pipe. The entire assembly will measure 40 meters in length. (Credit: Christian Haller & IODP) [Photo ID: exp356_138]

Overview

Sediment and rock cores recovered during IODP expeditions provide key data to interpret the geology and biology of the subseafloor environment. However, core recovery is not always complete. In addition, core samples brought to the surface are not at their original conditions of temperature and pressure. Downhole measurements complement core sample analyses and are vital for obtaining continuous and/or in situ records of subseafloor ephemeral formation properties.

The Downhole Measurements laboratory is used as a staging and data acquisition area for several types of downhole measurements, including those taken by tools deployed on the drill string/coring cable and on a standard 7-conductor logging cable (or "wireline").

The IODP JRSO utilizes three main kinds of downhole measurements: well logs, formation testers and samplers, and long-term borehole observatories. The laboratory has the equipment necessary to measure a variety of physical, chemical, and structural properties, including the natural radioactivity, density, electrical resistivity, porosity, permeability, and temperature of the formation. In addition, there is equipment for measuring formation properties and collecting downhole fluid samples from the borehole and from the formation. For detailed tool descriptions, please see Downhole Logging Tools.