Sinai well logging compares TDT, CHFR applications

The use of thermal decay time (TDT) and case-hole formation resistivity (CHFR) techniques for monitoring reservoir water saturation has been compared by a Sinai, Egypt oil field. Based on a time-lapse technique, interpreting TDTs is he most useful and practical approach. TDT is advantageous for wells not having a reference log. Its reliability increases with greater formation porosity and water salinity. However, it is limited by not for formations with near wellbore effects, not for formations with low porosity and others. On the one hand, CHFR evaluation is possible in low porosity and low formation-salinity zones. However, CHFR is prone to a scraper run, not make good contact at casing collars which can cause distortions and not designed to operate in dual strings because of too many variables in the installation. Therefore, a CHFR may replace a TDT log in cases where reservoir conditions or well completions are unsuitable for running a TDT log. While CHFR clarifies any confusion in the TDT interpretation, TDT shows more water saturation difference with reference openhole water saturation, indicating more flooding than CHFR.