Experimental Pulsed Neutron Porosity for Gas-Filled Boreholes in the Gulf Coast

Abstract

ABSTRACT Determination of formation porosities in cased holes becomes necessary when no other porosity information is available, such as openhole logs or core data. Within the pulsed neutron generations of logging tools, there have been various hybrids of "neutron" porosity computations made. The porosity has primarily been derived from a ratio of the count rate data obtained from selected gating and or detector combinations. Success has varied, depending on tool type and the composition of the formation encountered. A technique has been developed for the Gulf Coast which has much less sensitivity to the environmental effects of gas in the borehole. Over the period of a year, numerous tests were made with data from wells with various borehole conditions. The results to date indicate that this new technique will have application in eliminating or minimizing wellbore environmental effects due to gas in the wellbore. Gulf Coast and other examples are included which illustrate comparisons of this new technique with other porosity measurements.