Characterisation of a dolomitised offshore carbonate reservoir using basin modelling, digital rock models and high-resolution heat flow simulations
Abstract
Carbonate reservoirs host more than half of the world’s remaining conventional
hydrocarbon reserves. However hydrocarbon production from carbonates is very
challenging because they often have complex distributions of porosity and permeability
that are the result of depositional and diagenetic processes. Indeed,
80% of North American and many Middle and Far Eastern carbonate reservoirs
are found in dolomitised rocks where dolomitisation is a main control on reservoir
quality.
In this thesis, three main contributions relating to carbonate diagenesis in general
and dolomitisation in particular were made by combining digital rock models,
basin modelling, geomechanical simulations and high-resolution heat-flow
simulations. Data from an Ypresian (early Eocene) dolomitised carbonate reservoir
located in the offshore Tunisia was used.
First, the diagenetic sequence and the corresponding porosity and permeability
evolution before and during dolomitisation were investigated using digital
rock models. Secondly, published fluid inclusion micro-thermometry data was
combined with insights of the burial and thermal history obtained from basin
modelling to identify the possible time of dolomitisation. A structural restoration
was carried out to reconstruct the basin geometry up to the time when dolomitisation
occurred. Finally the basin scale hydrogeology at the time of dolomitisation
was investigated using high-resolution heat-flow simulations. The fault
permeabilities in these simulations were based on geomechanical considerations
and simulations. The resulting flow patterns and temperature distributions in
the basin were qualitatively compared against oxygen isotope data that served
as proxy for temperature.