Analytical Methods for Estimating Hydraulic Diffusivity in Heterogeneous Reservoirs Influenced by Ocean Tides

Abstract

In offshore wells, the pressure fluctuations caused by the ocean tide can be used to inform on the mechanical properties of the reservoir, in particular its compressibility. Such phenomena is not associated with water movement, except at the microscopic level. In heterogeneous reservoirs, these pressure oscillations can cause macroscopic movement of water, which can serve as the basis for the estimation of reservoir flow properties. The purpose of this study is to develop a set of analytical solutions that describe the pressure variations in a heterogeneous reservoir, in terms of amplitude ratio and phase shift. The solutions were developed using the coupled fluid flow-geomechanics equation for a reservoir under uniaxial tidal loading. This study looks in particular at three geometries of inhomogeous diffusion—radial composite, linear composite and composite slab.