In recent years there have been increasing marketpressures and hints of regulatory changes that wouldrequire the total elimination of traditional nuclear welllogging sources for downhole applications. There are anumber of reasons why replacement of isotopic sourceswould be desirable, and a considerable effort has beenexpended discussing and researching the possibilities.The dialog has taken place at every level from internalresearch and development activity at individualcompanies and laboratories, through discussions amonglarger groups at technology forums and special interestgroup meetings, all the way to congressional hearingsand formal Nuclear Regulatory Commission reports tothe President of the United States.The issue is not just the replacement of the Americium-Beryllium neutron logging source, but of the Cesium-137 source as well. Various service-company andoperating-company groups have been wrestling withthis problem for at least 30 years, and yet no acceptablereplacement for the traditional Cesium gamma-gammadensity measurement has been fielded. There are someservices that produce a density curve using pulsedneutron generators, but none of these provides theaccuracy and precision of the traditional sourcedmeasurement. The gamma-gamma densitymeasurement is the most trusted porosity indicator forreserves estimation around the world, and the lack of aviable sourceless alternative creates a problem for theindustry. The fact that formation density and neutronporosity measurements are used for much more thanjust formation porosity complicates the issueconsiderably.This paper examines some of the potential benefits ofusing neutron generators and high energy photonsources in well logging. Pulsed neutron generators canbe used for a number of measurements in addition toneutron porosity, and these additional data can besignificant going forward. The potential for highenergyelectronically controlled photon generators istruly great if we can produce measurements of qualitycomparable to the traditional Cs-sourced tools, and ifwe can get them to work in the downhole environment.We will also examine some of the difficulties involvedin making all of this happen. There are significanthurdles that must be overcome to produce the necessaryenabling technologies required to provide the level ofreliability, accuracy, and precision that we have becomeaccustomed to with the traditional sourced tools. Wewill discuss some of these issues and attempt to suggesta course forward.
展开▼
