Pressure depletion during oil production results in increase of overburden effective stress in a porous matrix. This stress in turn causes rock compaction with deformation and consequential permeability and porosity reduction. Production rate decline during oil production due to rock compressibility has been observed in several reservoirs.

The rate decline during pressure depletion is particularly significant for totally unconsolidated or slightly consolidated sandstones, which are typical for Campos Basin reservoirs (Brazil).

Compaction with porosity reduction can improve production by squeezing oil from rock into wellbore. However, compaction can also impair permeability and reduce production. Understanding the interplay of these effects is essential for optimising well placement, for predicting of production rates and for reservoir management.

The collective effects of compaction phenomena on oil production and reservoir behaviour can be understood by means of mathematical experiments using synthetic, laboratory and field data. Mathematical modelling can do reliable prediction of oil production.

A mathematical model for radial oil flow towards wells in a deformable porous media is derived, and the boundary problem for the quasi steady state depletion processes is formulated. The solution is expressed by explicit analytical formulae. The model was applied to the reservoir R (Basin C, Brazil) and results were compared with laboratory data.

You can access this article if you purchase or spend a download.