Role of Probabilistic Petrophysical Analysis in Rock Physics Modeling for Better Reservoir Characterization It’s Importance and Pitfalls

Beer S. Bisht, P. K. Chaudhri, Birbal Singh, and N. K. Verma
INTEG,GEOPIC, ONGC, Dehradun, India

Probabilistic Petrophysics, a radical new approach in Petrophysical analysis, has been adopted in the industry for estimation of volumes of minerals and fluids of the reservoir being logged by the wire line logging tools. Mayer & Sibbit in 1980 formalized a new approach for Petrophysical analysis where they focused on the response of wire line tools to the environment being logged. They setup response equation for predicting each measurement in the logging suite in terms of all the volumes of minerals and fluids that actually influence each sensor. These volumes were adjusted to give optimum or most probable match of the measured and predicted logs.

The data acquired by the logging tools in insitu condition and hostile environment of the borehole need to be corrected. Most of the logs are effected by washout or rugoes hole, mud filtrate invasion, type of mud, borehole temperature, pressure and salinity of the formation water which misleads the estimation of the reservoir parameters. The optimum results thus obtained are most suitable for rock physics modeling for better reservoir definitions.

Rock Physics modeling relates elastic parameters to porosity, mineralogy and fluid content of the reservoir. The seismic velocities are sensitive to reservoir parameters like porosity, lithofacies, pore fluid types, saturation and pore pressure. The estimation of reservoir parameters and to build relationship between these is the key objective of rock Physics modeling. Effect of porosity & fluid can be estimated through several modeling methods e.g. Xu - White, which has been used in present study.

Presentation GEO India Expo XXI, Noida, New Delhi, India 2008©AAPG Search and Discovery