Daniel F. Dorffer

Method and Application of Cyclic Well Testing With Production Logging

One of the predicaments of traditional well testing is the requirement of shutting-in a well to conduct a pressure buildup test for the purpose of obtaining well and reservoir properties. This deterrent factor is more prominent in prolific wells due to loss of revenue and problems associated with crossflow or when bringing a well back on production. Moreover, in case of commingled reservoirs, conventional buildup provides only average values of permeability, skin, and pressure. An innovative periodic well testing technique named WTPL (Well Testing by Production Logging) has been developed in which a cyclic wave function is imposed in the wellbore by modulating the flowrate. The analysis of the acquired rate function and the resulting pressure wave then provides formation characteristics such as permeability and skin in the vicinity of the well. This technique eliminates the disadvantage of shutting-in a well and maintains the production with a modulating periodic pattern. In addition, the WTPL can be easily applied to commingled reservoirs to estimate the individual permeability and skin for each layer. This effort has also resulted in the development of a downhole flow modulation tool capable of creating the cyclic flow patterns needed for the new testing method.

Cased-hole interpretation workflow for determining residual oil saturation for mature fields

AbstractFormation evaluation for mature oil fields remains a challenge for operators. Rock-petrophysical properties present large uncertainties following years of production. Formation evaluation becomes even more challenging when there is a lack of open-hole logging data as is typically the case. Logging programs for cased-hole formation evaluation are limited by the size of the well completion. In addition, a metallic casing often prevents the effective use of electric measurements. However, pulsed-neutron tools (PNTs) are a viable option for mature fields. We developed a brief review of PNT theory. The high-energy neutrons output at a high count rate fit the need of cased-hole applications. Application of pulsed-neutron technology for mature fields and a case history from west Texas, in which pulsed neutron technology was used to determine remaining oil saturation are discussed. We documented the best practice for data acquisition and the processing workflow. Having a good collaboration between operato...