In producing fields, remapping reservoir fluid content and new contacts are some of the most important objectives in pursuit of optimized well productivity. Wireline logs and formation testing (FT) data are widely used for this purpose. Continuous fluid data from advanced mud gas (AMG) analysis with downhole logs can be used to generate a comprehensive data set for reservoir evaluation. Each method has its limitation and advantage. Combining and interpreting the output from the fundamentally different data sets require an experienced petrotechnical expert with specific skill sets.

To calculate hydrocarbon volume, and estimate and forecast reserves, formation fluid evaluation has primarily relied on a traditional method that depends heavily on formation pressure measurements. This was achieved through the analysis of gradients and local fluid contacts. This approach can be misleading for brownfields, where a sizable amount of producible hydrocarbon is left in the reservoir.

For characterizing formation fluid, a novel approach using complimentary technologies was adopted. For early hydrocarbon detection and FT program optimization, AMG data were first gathered while drilling. Post-drilling openhole (OH) logs, formation pressure, and fluid data were acquired not only to verify the AMG findings, but also to fill in the gaps regarding water-swept zones, reservoir pressure and depletion, exact fluid contacts, and fluid characteristics to reduce uncertainties.

During the job execution, AMG data were effectively used to provide early formation fluid identification and contacts. This information was used to optimize the wireline advanced fluid analysis stations. AMG analysis identified multiple fluids (wet gas, gas condensate, oil, and water) and revealed a much greater complexity of the reservoir, which could not be achieved with standard formation evaluation or other fluid contact identification techniques based on regional gradient analysis. The fluid types and contacts identified by AMG were then confirmed by the wireline downhole fluid analysis. Using this workflow, a high potential recoverable hydrocarbon oil was identified over a reservoir that was classified as a water zone based on initial evaluation and knowledge.

In this field, an innovative method was adopted for reservoir fluid characterization. This approach, based on digital integration and a unified workflow, was used successfully for fluid contact identification, targeted fluid sampling, and identifying and recovering more hydrocarbon from the swept zones.

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