Identification of hydrocarbon movability and type from resistivity logs

Resistivity data is normally used to evaluate water saturation using porosity values from porosity logs (neutron and density). Determination of initial oil (gas) in place is based on hydrocarbon saturation, porosity, and thickness obtained from openhole logging data for a given drainage area. It is important not only to determine the initial hydrocarbon in place, but also to define the existing hydrocarbon movability, indicating the recoverable hydrocarbon and its type. This article presents a new approach of the hydrocarbon movability factor (HCM). This factor is derived from shallow and deep resistivity data. The relation F = a/m is correct in water-saturated zones; in partially saturated zones this relation becomes invalid, and it will give the apparent formation resistivity factor (Fa). Based on this idea, the HCM has been derived, with scale going from 0.0 to 1.0. It is found that for HCM less than 0.75, hydrocarbon is movable, and for HCM greater than 0.75, the hydrocarbon is immovable. When HCM is less than 0.25, the movable hydrocarbon is gas, and for HCM greater than 0.25 and less than 0.75, the movable hydrocarbon is oil. Field examples have been analyzed with the HCM factor. These field examples demonstrated the contribution of HCM in the field of hydrocarbon type identification and determination of hydrocarbon movability from openhole resistivity logging.