Following the work from Ilk [2023], pressure normalized decline could be extended to include multiphase flow rates.
Step 1: Calculating the Multiphase Productivity Index (JTF)
In this work, based on URTEC 2019-178-MS, fluid rates are summed together, and divided by the pressure drop (as discussed in Pressure Normalized Decline Analysis ). The forecast is then generated using the pseudo fluid. This method is very close to FMB and Rate Transient Analysis (RTA)using both flowing pressures and initial pressure (and is just short of basic PVT and Net Pay).
This is very close to traditional PTA methods where one used combined fluid for multiphase flow
Of course, one can also perform some of the pre-mentioned flow regime identification as shown below to help identify boundary dominated flow extra.
Step 2: Predicting Total Fluid Rate
Ilk [2023] then showed the back-calculation of the total fluid rate the predicted DCA model. In this particular example, he also showed DCA to predict future flowing pressures; However, one does not need to use a modelled Pwf, and can choose to use any specific value they see fit.
Step 3: Extracting Water Cut
Once a total fluid rate prediction is available, the water decline can be calculated based on a prediction of WOR (or similar). Basically
Step 3-1: Calculate water fraction, based on total fluid, and make future prediction.
Step 3-2: Use predicted water fraction to extract water rate from total fluid (this leaves BOE as we still need to account for gas flow).
Step 4: Extract Oil Rate & GOR (or similar)
With BOE and water rate calculated, one can now perform an extrapolation of gas-oil-ratio (GOR).
Step 4-1: Forecast GOR using user desired methodology
Step 4-2: Extract Gas Rate from BOE and qg relationship
Step 4-3: Calculate Oil Rate using the gas rate and GOR.
