Pore-Pressure-Analysis Using Eaton's Equation

INTRODUCTION:

High pore pressures within sedimentary basins and subduction zones present a significant hazard during the well drilling for oil and gas exploration, geothermal energy exploration etc. The Eaton's method is used here analyse the evolution of pore pressure within a typical oil petroleum basin.

Pore Pressure Analysis workflow using Eaton's Equation:

--- Steps

1. Data Laoding, Cleaning and Processing
2. Estimate the Normal compaction trend line (NCT)

$$ P_{pg}=\sigma v_{g}-\left(\sigma v_{g}-P_{hg}\right)\left(\frac{\Delta t_n}{\Delta t}\right)^m $$

$$ \Delta t_n=\Delta t_m-\left(\Delta t_{ml}-\Delta t_m\right),e^{-cz} $$

3. Estimate Lithostatic Pressure

$$ \sigma v_{g}=\frac{\left(P_{sea}+\int_0^Z\rho_b(Z),g,dZ\right)-P_{sea}}{Z}=\frac{\int_0^Z\rho_b(Z),dZ}{Z},g $$

4. Estimate Hydrostatic Pressure

$$ P_{hg}=\frac{(P_{sea}+\rho_{w},g,Z)-P_{sea}}{Z}=\rho_w,g$$

5. Etimate of Pore Pressure using Eaton's Equation

$$ P_{pg}=\sigma v_{g}-\left(\sigma v_{g}-P_{hg}\right)\left(\frac{\Delta t_n}{\Delta t}\right)^m $$

$$ P_f=P_{sea}+P_{pg} Z $$

6. Estimate effective stress from classical Terzaghi's Equation

$$ σ_{v} = σ_{e} - P_{f} $$

7. Estimate of Lithostatic Load and Pore Pressure excess ratios

$$ \lambda^* = \frac{(P_{f} - P_{hydro})} {(P_{litho} - P_{hydro})} $$

$$ P^*=P_{f} - P_{hydro} $$

$$ \lambda = \frac{P_{f}}{P_{litho}} $$