"Processing and Interpretation of Pressure Transient Data from Permanent Downhole Gauges" by Masahiko Nomura

The author investigated methods to analyze the long term pressure data acquired from permanent downhole gauges. The study addressed both the data processing and the parameter estimation problem with the connection to the physical behavior of the reservoir.

Reservoir pressure has always been the most useful type of data to obtain reservoir parameters, monitor reservoir conditions, develop recovery schemes, and forecast future well and reservoir performances. Since 1990, many wells have been equipped with permanent downhole gauges (PDG) to monitor the well performance in real time. This continuous monitoring enables engineers to observe ongoing changes in the well and to make operating adjustments to optimize recovery. The long-term pressure record is also useful for parameter estimation, since the common pressure transient tests such as drawdown or build-up tests are conducted during relatively short periods.

However, the PDG data have several complexities, since the pressure data are not measured under well-designed conditions as in the conventional well testing schemes. The pressure data may have various types of noise and may exhibit aberrant behavior that is inconsistent with the corresponding
flow rate. The flow rate may change irregularly, since the flow rate is not controlled based on a designed scenario.

The methods enabled us to address specific issues:
(1) model identification,
(2) flow rate estimation,
(3) transient identification, and
(4) data smoothing.