Recent observations indicate a distinct hydrocarbon composition change in a mature condensate rich gas field in the Sultanate of Oman, which will drastically change the next development decisions.
The new insights were a result of: 1) data analysis and visualization and 2) collaboration between Development Planning (DP), Well & Reservoir Management (WRM) and Exploration. Field data such as well tests, fluid samples and production logging tests were integrated with geological concepts to deliver reservoir models that could assist late field life decision making.
The outcome of the data analysis was summarized in the so-called "Plumbing Diagram", which combines reservoir architecture, structural elements, fluid fill and a reservoir connectivity analysis. The diagram was also used as a collaboration tool between Development, WRM and Exploration, which enabled the non-core team members to quickly understand the key uncertainties, risks and opportunities.
Field data indicated vertical changes in hydrocarbon composition across the field. These new observations were combined with exploration burial diagrams and thin section analysis from core data. This led to the insight that the gas field is not just rich in condensate, but has gone through various hydrocarbon charge stages starting with an initial oil charge. A recently drilled well confirmed the existence of the oil charge with solid bitumen indicating a subsequent thermal cracking phase.
Integration with wire line log evaluations made it possible to define two field-wide fluid zones, referred to by the team as: 1) Free Gas (FG) and 2) Condensate Rich Gas (CRG). The split of the two fluid zones will have a major impact on the field Development and WRM strategy as the focus is shifting towards development of the CRG zone, which is more challenging mainly due to the fluid fill mixture of oil, bitumen, gas and condensate.
This paper describes how field data, observations and collaboration between teams improved the total hydrocarbon system understanding driving the future development decisions. The success of the changes in the development and WRM strategy will serve as blueprint for condensate rich gas fields with a similar burial and charge history in the north of Oman.