Rock Physics Analysis from Well Log Data of Carbonates

Choudhury, Suryyendu¹, Manika Prasad¹, R.D Chourasiya² (1) IIT-Bombay, India, Mumbai, India (2) Oil and Natural Gas Corporation Ltd, Mumbai, India

We have analyzed the well log response of carbonate sequences from passive margin basin in terms of repeatability of signals, trend development and examined possible rock physics transforms. The study incorporated interrelationship of the various logs like GR, Resistivity, NPHI, RHOB and sonic logs. The relationships between various rock properties vary from diffused, clustered to well defined trends. For example, bulk density–neutron porosity are inversely related but are scattered in few horizons. Neutron porosity-velocity data are scattered: we could not decipher a trend in some horizons. The repetitiveness of a signal in varying scale (few meters to 10s' of meters) may be explained by changes in the depositional pattern of the area. We attempt to explain these observations from geological point of view thereby tying up the petrophysical observations with the background geological knowledge. We look upon the Bombay offshore, India, to see whether such trends are recorded or not with the help of necessary rock physics transforms amalgamated with geological reasoning.