Time to Revisit Deep Dielectric Measurements? – Interesting Insights From Middle East Carbonate Reservoirs

Industry interest in deep dielectric measurements dates back to the 1960s and 1970s, when several oil operators and service providers developed wireline tools to measure the formation dielectric permittivity away from the borehole. Simultaneously, both academic and industry research explored interpretation methods to derive water saturation from the measured quantity. Water saturation derived from dielectric permittivity has been shown to be far less affected by salinity variations, which is an attractive feature/advantage in formations with mixed or unknown salinity. Several Middle East carbonate reservoirs have high salinity connate waters (180 – 220 kppm) and are subject to active water flooding with sea water (35 – 40 kppm). This mix of salinities makes the estimation of fluid saturations within the flood zone from resistivity or neutron capture logs very challenging due to uncertainty in the water salinity. Resistivity-based saturation estimates assuming either connate water or sea water can differ by more than 40%. At the same time, the water saturation estimate from dielectric permittivity is minimally affected by rock texture and wettability variations (Rasmus and Kenyon, 1985; Focke and Munn, 1987), both of which are known to greatly affect resistivity interpretation. However, deep dielectric measurements in saline boreholes or very conductive formations proved technically challenging when performed with conventional wireline logging devices. Hence, these measurements fell out of favor and virtually disappeared from the industry by the mid- 1980s. However, recent enhancements in the processing of Logging While Drilling (LWD) propagation- resistivity logs have provided a quantitative estimate of formation dielectric permittivity in the undisturbed 1 NoHiddenPay LLC 2 Abu Dhabi National Oil Company Offshore formation (Anderson et al., 2007; Luling, 2015). We adopt this innovative method to process the LWD logs, which respects the fundamental physics of electromagnetic propagation and determines both conductivity and dielectric permittivity from the measured data. Before the