Hydrocarbon Potential Monitoring of By-passed Pay Zones Using TDT and CHFR Logs

Detection of pay zones and monitoring the rate of advance of water zones represent main task of the petroleum engineer, this is improve the efficiency of producing wells. The ability to detect pay zones and definition of new water levels are necessary to propose remedial actions to reduce water cut values. Good cased hole well logging program is required to answer this question. The main technique, which has been used for monitoring reservoir saturations, is TDT tool. But, it was hard to interpret the TDT data in the low formation water salinity reservoirs. This problem can not be solved because it is related to the theory itself of TDT measurement, which depends on salt content in formation brine. Cased Hole Formation Resistivity tool (CHFR technique was proposed to overcome many of the pulsed neutrons tool limitations. A comparison study was done between the two available techniques, TDT and CHFR as methods for reservoir saturation monitoring, in addition to the results of open-hole resistivity logs as reference runs. It was found that water saturations calculated from CHFR logs were more accurate than TDT log in most of the cases.