The diffusivity equation for geopressure prediction using well logs

• This novel method follows accepted theoretical criteria of diffusion transfer phenomena.
• An analytic approach of solution is being applied rather than empirical.
• The model is applicable for complex lithological scenarios others than Tertiary formations.
• Because no Normal Trend of Compaction identification is needed, no graphical method is required.
• The method is useful for identifying additional sources of abnormal pressures other than disequilibrium compaction.

Common practice in industry is to obtain geopressures from indirect methods applied to data obtained from seismic or electrical logs. Because the diffusivity equation describes the pore pressure behavior of a saturated porous media, in this work, it is being used as the basis to attempt a solution to estimate pore pressure in producing formations and above them, in the overburden. Formation properties captured through well logging in offset wells are introduced to our solution of the diffusivity equation as “normalized values” to estimate pore pressures. For a traditional pore pressure assessment, as it is proposed in this work, the problem is set to a time frame. The resulting boundary value problem is solved by applying a “non-strict inverse approach” until a satisfying solution is found. Pressure data from offset wells are used as calibration parameters to obtain the pore pressure distribution along depth of investigation. To prove effectiveness and accuracy of our novel technique, results from real data in conventional and complex geological basins are discussed.