4. The reservoir is a carbonate reservoir. The data set of deep resistivity and interval transit time is given in Table Q4. Estimate the formation and true resistivity value, R, when water saturation is held at 50%. Note: The hole is filled with fresh water mud. Table Q4 Data set Data Set Deep resistivity Transit time Rd, (ohm.m) At (us/ft) 1 8 59.5 2 25 52.0 3 30 64.0 4 60 49.0 5 70 56.5 6 100 52.0 7 200 64.0 [20 marks]