1. A method of performing operations for an oilfield having at least one wellsite with a wellbore penetrating a subterranean formation for extracting fluid from an underground reservoir therein, comprising: obtaining a set of Nuclear Magnetic Resonance (NMR) data of a portion of the subterranean formation from inside the wellbore without acquiring formation fluid sample; isolating a quantitative reservoir fluid information associated with oil from oil based mud (OBM) using radial profiling of the set of NMR data, wherein the OBM is used for extracting fluid from the underground reservoir; determining gas-oil-ratio (GOR) related information associated with the portion of the subterranean formation from the quantitative reservoir fluid information associated with oil, wherein the GOR related information is determined based on a predetermined model; and performing operations for the oilfield based on the GOR related information.