P - Wave Velocity Characteristics in Coal Measure Rocks of Eastern India Coalfields

The P-wave velocities and their relation to depth of burial, density, porosity and electrical resistivity are studied for the coal measure rocks of Ranigunj and Jharia coalfields. From studies on the P-wave velocities in the dry and fluid saturated states, it is observed that the effect of fluid saturation is significantly more in a direction perpendicular to the bedding plane, than in the direction parallel to the bedding plane. The effect of fluid saturation is maximum in coarse-grained sandstones with low P-wave velocities. The anisotropy factor (Vp/⊥ Vp), decreased after fluid saturation. The absorption-anisotropy relation for sandstones is found to depend on grain-size distribution as well as fluid saturation conditions. The results show that saturating conditions, direction of measurement and anisotropy assume importance in the interpretation of velocity data.