## 5 A Hybrid Computational Platform
Figure 5: Pressure transient analysis toolbox. All the tools assembled honor the information exchange protocols of the hybrid platform discussed earlier. Making the decision on the suitability of an EOR process to a specific field is generally accepted as the very first step of paramount importance. There are typically a multitude of options in making this important decision. The expert tools highlighted in Figure 4 are designed to make the best decision on an EOR process, and when some representative reservoir parameters are assigned, they can generate not only a checkmark as required by a rule of thumb approach, but also some expected recovery performances in a quantified form. Thus, during the screening stage, it will be possible to visit several EOR processes and make an informed decision about the suitability of the most promising process. Once such a decision is in place for a specific EOR methodology, then in the next step a large number (tens of thousands) of proxy model runs can be conducted by varying reservoir properties and project design parameters to generate some certainty brackets on the project performance indicators. If needed, the information on optimized project design parameters, together with reservoir parameters used, is passed to the relevant high-fidelity model located on the right-hand-side of Figure 3 and the high-fidelity model is run to verify the results from the proxy model. As explained earlier, the coupled approach helps the EOR project design engineer by narrowing the search window extensively so that most of the unnecessary and peripheral work is eliminated. Furthermore, by studying tens of thousands of scenarios rapidly on the implementation of the project, it will be possible to quantify the overall certainty of the results more precisely. Figure 5 shows several well test analysis expert systems assembled in a second toolbox. These tools are designed for the pressure transient analysis (_PTA_) of hydrocarbon reservoirs with radically different macroscopic and microscopic characteristics. Some of these _PTA_ expert systems are designed for complex well structures such as multilateral wells, slanted wells, wells completed with multi-stage hydraulic fractures, etc. Well test analysis is a class  
Figure 6: General reservoir engineering applications toolbox. of systems analysis. In a systems analysis application, the system under observation is perturbed (e.g., the well is shut in or put on production). The reservoir system responds to this perturbation and the resulting signals (pressures) are measured in a time series. Then, using the existing analytical solutions in an inverse mode, some key reservoir characteristics are determined. Models that are used in pressure transient analysis are always built in the same manner. The basic models assume homogeneous and isotropic reservoir characteristics. There are also analytical models that are built for double-porosity, multilayer (with or without crossflow), and composite reservoirs. In well test analysis, perhaps the most critical step is the identification of the model that will be used in the interpretation of the well test data. The supervisory model that is placed at the top of Figure 5 reviews the time series of the pressure data and looks for specific signatures (markers) so that it can decide which expert system from the toolbox should be called in to conduct the pressure transient analysis. In generating the training data for the expert tools shown in Figure 5, either available analytical models or numerical models are used. Then, the specialized expert systems are exposed to the training data to learn and discover the existing signatures recorded in the data sets. The expert systems shown in Figure 5 have the capabilities to shed more light on the reservoir characteristics than the classical analysis models.