Accurate fluid characterization is critical for reservoir development planning and typically relies on pressure-volume-temperature (PVT) experiments. However, in structurally complex reservoirs, fluid classification based solely on laboratory measurements can lead to misinterpretations. In the Gongshanmiao block of the Sichuan Basin, initial PVT analysis suggested that the reservoir was a condensate gas system. Subsequent field development revealed inconsistencies with this interpretation, including abnormal gas–oil ratios and atypical pressure build-up behavior that deviated from expected condensate gas reservoir performance. To resolve this discrepancy, this study proposes a diagnostic framework that integrates geoscience and engineering data, including fluid sampling, 3D structural modeling, production performance analysis, pressure build-up testing, and hydraulic fracturing data. The integrated analysis revised the initial PVT-based interpretation, and the results indicated that the reservoir is more accurately characterized as a saturated oil system with an overlying gas cap, rather than a condensate gas reservoir. Furthermore, the integrated interpretation clarifies the structural trapping mechanism and delineates the spatial extent of the gas cap. Overall, the proposed approach provides an integrated geoscience-engineering workflow for fluid reclassification in structurally complex reservoirs, which reconciles laboratory fluid analysis with field production behavior, offering a systematic framework for fluid interpretation in similar geological settings.
Yu et al. (Fri,) studied this question.