The Naturally Fractured Reservoirs (NFR) constitute a challenge for the oil industry due to its importance in hydrocarbon production and the technical complexity they represent, because well’s productivity in carbonated formations is influenced by fracture systems that govern the fluids motion within reservoirs. This approach is oriented to the analysis of a very complex NFR, where we show the results obtained through a dynamic characterization methodology focused on new opportunities in a High Pressure-High Temperature (HP-HT) coastal mature oilfield with high water cut production. The proposed methodology is based on a full analysis starting from the pressure-production historical data, fluids properties, dual-porosity material balance, a detailed static model update (petrophysics, core analysis, petrography, fracture analysis, sedimentology-diagenesis and structural geology), flow units discretization, Water-Oil Contact (WOC) advance monitoring in each block, Pressure Transient Analysis (PTA) (determination of preferential flow direction and interference), and Rate Transient Analysis (RTA). This methodology allowed to determine the real Original Oil in Place (OOIP) and the proper recovery factor according to the type of NFR and its characteristics, to detect different WOC’s for each block that were hydraulically connected to each other but with a different dynamic behavior among them, the detection of heterogeneities, facies changes and faults that originally were not mapped, sweet spots location, better distribution of the petrophysical properties, fracture analysis, static model reinterpretation based on the dynamic behavior, reservoir connectivity analysis (among blocks) and the generation of improved production forecasts based on an exploitation strategy especially designed for the current conditions and needs of the field; all of this contributed to have a better understanding of the reservoir and a good numerical simulation model.

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The objective of this work is to generate a selection matrix that contributes to the decision making, contemplating all the necessary technical criteria to ensure that the information gathering is adequate and the Pressure Transient Analysis (PTA) could be advantageous for the reservoir characterization and the determination of well productivity parameters. For this scrutiny we analyzed more than 500 well tests from 100 fields in Mexico and other parts of the world, onshore and offshore, carbonates and terrigenous, and different types of fluids (black oil – extra heavy, heavy, intermediate and light, volatile oil, retrograde gas and condensates, wet gas and dry gas), from which all the pressure responses obtained were compared in order to identify every associated problem and the causes that originated them from the design, execution and finally, during the interpretation of the PTA. The importance of this work lies in improving the PTA through the allocation of different numerical values for each of the controlling factors involved at reservoir, well and at surface level, depending on its own impact on the results, so we classify them in Well Evaluation Conditions (WEC) and Reservoir Evaluation Conditions (REC).