Parameter Estimation for Linear Velocity Functions

The porosity-preserving and permeability-reducing Fe-chlorite coatings present in three sandstone reservoirs coming from the Lower Cretaceous of Pakistan and the Silurian of Tunisia, were characterised in order to understand their evolution in the 90-160 °C temperature range. The two chlorite resulted to be respectively a thuringite and a chamosite and showed a difference in total thickness. This difference is tentatively attributed to thermal evolution, as the Cretaceous samples underwent a more severe heating (present temperature around 160 °C) than the Silurian ones (present temperature around 90 °C). The original clay minerals (precursors) were completely transformed to chlorite in this temperature range. This might imply that prediction of reservoir quality in Fe-chlorite bearing sandstones has to take into account temperature as a key-factor.