oa De-Risking H2S in Carbonate Khuff Field in Central Oman: Implications for Facility Design and $14.2 Million Cost Avoidance

Middle Khuff in Field A was initially considered a sweet opportunity based on Well A-1 and A-2, which showed no H2S in the produced oils. However, after drilling Well A-3 in the field’s crest, H2S increased rapidly, showing elevated concentrations which exceed 1400ppm. The study examined oil, gas, and water phases to understand the origin of the H2S, reservoir connectivity and inform decisions about the Field A production facility, which was not designed to handle high H2S levels. The results indicated noticeable differences in the oil and water chemistry between Well A-1 (sweet) and Well A-3 (sour), suggesting inhomogeneous hydrocarbon columns. Oil and gas analysis suggested that the H2S was likely derived from the Upper Nafun/‘Q’ source rocks rather than biogenic processes. Further analysis pointed to the possibility that Well A-3’s horizontal hole was connected with the Lower Khuff through natural fractures, which explained the increase in water cut post-production and the discrepancies in water and oil chemistry. The findings were supported by the Well A-4 drilled in the flank, which tested 0ppm H2S. This study reduced H2S uncertainty, preventing a costly $14 million upgrade to the production facility and minimizing risks for future Middle Khuff wells.