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Logging service companies are attempting to provide a fairly good selection of devices which have proven to be popular with the oil industry. However, the introduction of new devices or new services is being limited because oil companies are standardizing the logging‐suites run in their various geographic operating areas. Some of these new techniques appear to have significant applications. Recently, standard logging‐suites and evaluation‐techniques have evolved; these can be evaluated in terms of open‐hole and cased‐hole applications and the physical parameters of interest. Generally, these standard procedures depend on the differences in responses of multiple electrical and porosity devices. The multiple measurements are input to response equations which yield the parameters of interest. Although mining companies have been slow to adopt logging techniques, the use of logging devices and interpretation methods in nonpetroleum mineral (groundwater, nonmetals, metallic sulfides, etc.) exploration and evaluation, and in providing geophysical survey parameters is increasing. Nuclear, electrical, acoustic, and other methods are utilized, and newer applications of these to exploration, particularly in lithology determination, suggest themselves. Log digitizing and computer processing of log data have become routine in most major oil companies, but techniques, programs, and equipment vary significantly. Currently, commercial digitizing services are too expensive to be used extensively; the per‐log costs, however, are declining as more digitizing companies offer competitive services. Two basic commercial systems for transmission and computation of log data are functioning. To date, these systems yield “quicklook” reconnaissance parameter computations. Current research and development emphasis is on pulsed neutron‐spectroscopy and acoustic‐parameter measurements and on digital processing techniques.

The current status and apparent trends in formation evaluation are reviewed. There are at present well over two dozen borehole measurements available for formation evaluation encompassing cuttings samples, cores, borehole fluid logs, wire line logs and productivity and fluid flow tests. Some twenty major applications in petroleum engineering are realized by use of this array of measurements. The predominant application continues to be estimation of recoverable hydrocarbon volumes, but other important applications in connection with exploration, exploitation, and well completion are also realized.

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