An Introduction to Continuous Electric Logging while Drilling

ABSTRACT In order to provide electric logging information instantaneously and continuously while drilling, a new continuous logging-while-drilling system has been developed and successfully field tested. This tool, utilizing a unique mud pressure-pulse-telemetry system, provides a continuous resistivity log of the formations as they are penetrated by the drill bit. Along with the continuous resistivity log, a drilling rate curve and gas curve is also provided. The focused monoelectrode resistivity measuring method used in this system is described and its qualitative and quantitative advantages and disadvantages are discussed. Typical logs run while drilling are compared with conventional wireline logs, and the advantages of logging-while-drilling on exploratory wells are examined.