When production testing an oil reservoir in the oil-water transition zone it is usual to expect water production. This paper shows field examples where dry oil production is encountered in the middle of oil-water transition zones in a non-fractured, mono-modal and essentially homogeneous carbonate reservoir. Whilst it is simple to replicate this behavior in numerical simulators, the reason behind this phenomenon is not so obvious. This paper pulls together current understanding with regard to wettability, capillary pressure, percolation and adsorption through films in order to explain the mechanism behind the phenomenon. Through a greater understanding of the cause of the anomaly it is anticipated that knowledge of pore scale processes will lead to improved recovery methodologies.

The Field, which is the subject of the case study, is in the appraisal stage (6 well penetrations, no production) and is composed of a series of stacked Carbonate reservoirs located in shallow water offshore of the UAE. The entire oil column has been cored, extensive Mercury Injection data was available for analysis and the oil-water transition zone extends across 70% of the oil column.

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