Loggingwhiledrilling

Over the last 15-20 years, new technology has been developed to measure in situ properties in oil and gas industry holes that are drilled horizontally where conventional logging with a flexible wireline is not feasible. This innovative technology is called "logging-while-drilling" (LWD) and uses sensors placed just above the drill bit [e.g. Allen, et al., 1989]. The differences between LWD and conventional logging technology, however, must be taken into consideration when using these data in a particular drilling environment [e.g. Evans, 1991], For example, wireline tools record information as they move upward at (approximately) constant speed and sample data at a fixed depth interval; LWD tools record information as they move downward at variable speed (the drilling rate) and sample data at a fixed time interval (Fig. 1). Currently available LWD

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