1 research outputs found
On the equivalence of total stress and pressure gradient formulations for predicting land subsidence above compacting gas/oil fields
The solution of the poroelastic equations for predicting land subsidence above productive gas/oil fields may be addressed by the principle of virtual works using either the effective intergranular stress, with the pore pressure gradient regarded as
a distributed body force, or the total stress incorporating the pore pressure. In the finite element (FE) method both approaches prove equivalent at the global assembled level. However, at the element level apparently the equivalence does not hold, and the
strength source related to the pore pressure seems to generate different local forces on the element nodes. The two formulations are briey reviewed and discussed for triangular and tetrahedral finite elements. They are shown to yield different results
at the global level as well in a three-dimensional axisymmetric porous medium if the FE integration is performed using the average element-wise radius. A modification to both formulations is suggested which allows to correctly solve the problem of a finite
reservoir with an infinite pressure gradient, i.e. with a pore pressure discontinuity on its boundary