In Al Khalij carbonate field, the impact of faulting and fracturing has long been considered insignificant on the dynamic reservoir behaviour. However with the continued field depletion, an interference between some wells has been noticed. This interference cannot be explained by matrix properties. Therefore, a better understanding of the detailed structure grain seems to be the key for understanding the field dynamic behaviour. This integrated study shows that faults can barely described from the seismic data. But it has been found that a detailed understanding of the field structure is possible if other data are also taken into account.
The model was therefore constraint with an integrated approach developed along the following four aspects:
1. Structural interpretation of the horizontal wells;
2. Seismic attribute analysis;
3. Image log data analysis;
4. Dynamic data analysis.
The structural interpretation of the seismic fault lineaments and the well fracture systems suggest that they are related to two successive compressive tectonic phases of different orientations which are controlled by a deep structural heritage and which result in a strike slip (transtensive), structural style.
A new structural model (Geo model) was created, but because of the insufficient reliability of the lower reservoir markers, a special attention was paid to the layer thickness construction. A meticulous structural study and the fault throw distribution analysis were performed before the final structural model construction to validate the structural consistency of the interpretation. All this work performed in 2D resulted in a very consistent structural network which was then used to define the 3D grid.
This geomodel reconciles all available data and analyses and gives a much more geological image of the field structure.
- Layer thicknesses are homogenous and not affected by drastic changes close to well calibration points.
- The resulting fault network appears to be rather predictive from recently drilled wells.
This new model will be the base of an updated reservoir model which should give a much better qualification of the field dynamic behaviour as investigated by other specialists.