Recent Advances in Com-putational Terminology

A well logging instrument having a gamma ray source, a short-spaced gamma ray detector, and a long-spaced gamma ray detector is coupled through a logging cable to surface electronics. A cadmium filter is used to alter the response of the short-spaced detector. This filter causes the relationship between the counting rates measured by the long-spaced detector and the short-spaced detector as the mud cake thickness is varied to be a straight line rather than a curved line when plotted on log-log graph paper. Filters composed of tin, silver, copper, nickel or iron, individually or in combinations, may be used in place of cadmium. Such straight line relationships are useful in determining true formation densities from the two counting rates.