Abstract
Recent publications1,2,3,4,5 have described the development and utility of cased-hole neutron and density porosity measurements from a pulsed-neutron system. Porosity information from cased-hole logging can provide required data for wells with limited logging programs such as old wells or new wells where open-hole logging is not viable. In reservoir sequences typical of the Rocky Mountain region, the addition of the cased-hole density measurement has proven useful in discriminating tight porosity from gas-filled porosity and coals from shales.
Whereas a tool such as the Computalog PND-S™ pulsed-neutron system uses two detectors, analysis of pulsed-neutron density measurement physics immediately suggests that a third long-spaced detector would be helpful in measuring deeper into the formation. Thus, a prototypical system based on the standard PND-S™ was constructed with a third detector at a 95-cm spacing. This prototype provided a collection of third detector data on normal logging runs.
Log examples from the North America Rocky Mountain region demonstrate the utility of this measurement in cased-reservoir analysis.
