RISK ANALYSIS ON WELL PERFORMANCES TO VALIDATE PRODUCTION TRENDS BY-PASSING BACK-ALLOCATION ISSUES

摘要

Production data back-allocation of fluids produced into the various wells can be affected by some uncertainties, especially when multiphase flow conditions limit the reliability of flowmeters measurements. This uncertainty can have a considerable impact on the outcomes of Production Data Analysis (PDA) aimed at understanding the main fluid paths in reservoir. In this context, a probabilistic Monte Carlo based approach is proposed to validate the production trends, especially in terms of WC and GOR, compensating the back-allocation issues. An Eni in-house tool (IPRMC) is implemented in order to manage the risk on production rates. A probabilistic approach is run on the VLP of each well, generating thousands of gradient curves among which it is possible to select those that honour the wellhead and bottom hole pressures, the most reliable measurements. This subset of curves is characterized by a new probabilistic distribution for each uncertain produced fluid which is used to identify its most likely value/range. The work describes the application of this methodology to an offshore deep-water field, where it proved to be a powerful tool to support detailed PDA. The risk analysis approach allows for more confidence in the fluids produced by each well, and better identification of the inter-well interactions and fluid dynamics in reservoir.