This paper discusses the early evaluation of vertical connectivity with vertical interference tests (VITs) using an advanced multi-probe wireline formation tester in a giant carbonate field in Saudi Arabia. The objective was to determine the vertical permeability of low permeability layers within the reservoir. Early understanding of the vertical connectivity is required to ensure the optimum development for new fields with limited dynamic data.

To conduct the evaluation, a multi-probe advanced formation tester was utilized in five key wells around the field to obtain vertical and horizontal permeabilities with several VITs creating pressure pulses at the dual packer, which produce pressure responses monitored at the two observation probes in real time. The vertical connectivity was assessed from the pressure response to the transient generated across stratigraphic layers. Comprehensive interference tests were conducted across all the layers. Advanced nonlinear regression analysis techniques were utilized for pressure transient analysis at test intervals. The results were further confirmed with a fine gridded 3D reservoir simulator. The integration of all vertical permeability results obtained so far indicated a good degree of reservoir vertical connectivity.

The VIT results were used as input in the field simulation model improving the accuracy of the vertical permeability in different areas of the reservoir, which in turn supported changes in the well placement strategy to maximize recovery.

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