The Art and Science of Rock Physics Model in Derisking Observed Top Carbonate Seismic Responses

Carbonates are complex rocks with on first look often puzzling elastic rock properties. Unlike clastic sand-shale systems, carbonate porosity and acoustic impedance often don’t follow simple depth trends. When cross plotting porosity and acoustic impedance, the scatter can be significant – for the same impedance we often find rocks from below 10 to above 25% porosity. In light of this challenge: how can we use seismic top carbonate amplitudes (i.e., acoustic and shear impedances of the carbonate and its bounding mudrock) to derisk undrilled carbonate buildups – we need to establish whether the structure is likely gas or brine filled, and whether the porosity is high enough to support commercial production rates.

This presentation provides key learnings on the rock modeling workflow in analyzing the carbonate prospect L, E and Z in Block A. The key observations from the nearby field wells suggest that the soft top carbonate corresponds to gas bearing carbonate and vice versa with the hard top indicating water bearing carbonate. Contrary to that however, there is also hard top gas filled carbonate from few analogue wells in the adjacent play. Hence, we explore and investigate the different rock scenarios to understand the top carbonate seismic response.