Confirmation of Water Saturation and Rock Fluid Properties Across the Transition Zone for a Major Carbonate Reservoir

Abstract

Proper petrophysical evaluation of carbonate formations, offshore Abu Dhabi is a difficult process considering the number of challenges to resolve. Lithology mainly consists of a combination of dolomite and calcite but also contains anhydrite which must be accounted for to get an accurate porosity. Resistivity measurements are affected by invasion and by the very high shoulder bed resistivity so computing formation resistivity can only be done through resistivity modeling and inversion, and once formation porosity and resistivity are properly computed, it is possible to compute an accurate formation saturation only if the Archie parameters cementation and saturation exponents m and n are properly defined. We will show how to resolve these challenges by acquiring and integrating in an advanced workflow a modern suite of logs including density-neutron-resistivity-gamma ray along with a multi-frequency dielectric measurement. We will also show how to confirm the formation saturation in selected zone in an Archie independent manner by combining the dielectric log and pump-out formation tester. The integration of the log data with core analysis results in a very comprehensive petrophysical evaluation of the formations encountered.