Dolomitisation is a diagenetic process that can affect carbonate rocks changing their original petrophysical characteristics. In the carbonate platform of Karachaganak Field this diagenetic event is significant, affecting about 40% of the rock volume, where both original porosity and permeability result to be increased. The 3D modelling of dolomite is therefore necessary to better describe the reservoir rock matrix storage capacity and flow capacity.

Despite the large data-base available, represented by lithological logs of about 150 wells calibrated on more than 25000 core plugs, the dolomite pattern distribution does not show clear trends. To go further of meaningless "bull-eyes maps", the 3D Modelling of dolomite has been performed integrating well data with conceptual models for dolomitisation, within the framework of depositional sequences presented in SPE139887.

Different conceptual dolomitisation models, described by different Probability Trends, have been applied for different Stratigraphic Units and the 3D Modelling has been performed using Sequential Gaussian Simulations. The simulations have been run, initially, without any well control using well data as verification data set. By trial and error approach, the different simulations have been checked at the wells, comparing CPIs percentage vs. simulated percentage. A tuning process has been performed, optimizing the practical application of Conceptual Models, revising the Probability Trends according to different geological inputs and adjusting the lithology percentage.

The workflow, applied to each Stratigraphic Unit, has led to a geologically meaningful stabilized realization, in good agreement with well data. Finally the Simulation has been performed well data constrained.

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