IDENTIFICATION OF GAS BEARING ZONES AND DETERMINATION OF MECHANICAL PROPERTIES UNDER TIGHT FORMATION USING VP! V RATIO AND POISSON'S RATIO

Abstract

Limestones and sandstones possessing very low porosities (-5% or less) exist in the Vindhyan region. These are expected to contain gaseous accumulations but due to their varying resistivities conventional methods of log interpretation a cannot be applied successfully. However, use of V Y/VS and Poisson's ratio is able to identifying gas bearing zones in such low porosity rocks. Logs available in such areas have been used to identify such zones. Both these ratios show low values in the presence of gas. Determination of gas saturation has been attempted based on the use of Biot-Gassmann theory which depends on the calculation of bulk moduli from sonic log data. This has been tried in the present case.