Effective Stress Laws For Petrophysical Rock Properties

Abstract

Effective stress laws and their application are not new, but are often overlooked or mis-applied. As we observe in deepwater GoM Lower Tertiary (LT) sands, the effective stress coefficient deviates significantly from one and can be quite different for different rock properties of interest. As petrophysicists, log and core analysts, we need to be aware that pore pressure can have a significant impact on reservoir properties in ways not easily described using a simple effective stress law. These effects must be taken into account when applying measurements made in the laboratory for calibration of reservoir engineering models and calculation of rock mechanical properties from acoustic logs.