Rock Physics and Quantitative Interpretation (QI)
Rock physics models provide the link between the reservoir rock properties and the Vp, Vs, Rho, acoustic and elastic properties picked up by the seismic sound waves. The reservoir rock properties include the description and makeup of the rock, i.e. the lithology (type, mineral mix), porosity (%, type), pore fluid (type, mix), fracturing and the rock’s present environmental conditions such as the pore pressure, confining pressure and temperature. Reservoir rock properties vary tremendously, from cold, shallow marine sands to hot, high pressured, deeply buried, fractured sandstones; from quartz grain suspensions to solid, cemented rocks; and from clastic sandstones to carbonate reefs to fractured volcanics. RokDoc provides a selection of rock physics models with matched fluid and lithology substitution methods. This enables seismic interpreters to forward-model the seismic data that would have been recorded in different geological scenarios. A quantitative interpretation is made by making comparisons with the real seismic data.
A RokDoc user in Perth commented: “Using rock physics we can forward model any scenario we want. If you want to know what would happen if your reservoir was filled with chocolate instead of oil you can! (Provided you can work out the Vp, Vs and Rho of chocolate.) Using rock physics we directly link the seismic and the rocks. Forward modelling allows us to find out what the effect of changing any characteristic of geology or petrophysics has on the seismic. If we have a water-wet well we can find out what the seismic would have looked like if it was gas bearing, or oil bearing (or even full of chocolate). It allows us to de-risk potential reservoirs that have been identified on seismic. We can forward model to see what the reservoir 'should' look like if filled with hydrocarbons. If our model of seismic and the actual seismic match, there is a very good chance that our model is correct”.