Individual well flowing rate recovery from PDG transient pressure with either assigned daily rate or total cumulative production of the well or group of wells through wavelet approach

Abstract

The advent of permanent down-hole gauge (PDG) makes the real-time reservoir monitoring and management possible, where the long term transient data can be processed to distill information about the reservoir through using recently developed wavelet transform algorithm. However, the key in analyzing the PDG data, particularly transient pressure, is to get the flowing rate history right during the pressure draw downs and build ups. In practice, the most available flowing rate data include assigned daily rate, total cumulative production of the well or group of wells with a measurement error tolerance at about ±10%. While multiphase down home rate data is rather expensive to have, the industry is desperately looking for ways to get the flowing rate history right. The second big problem in analyzing long term PDG data is that there is a time shift between the flowing rate and the corresponding transient pressure. In other words, when the rate goes up, the pressure also goes up instead of going down as expected. This caused a big problem in reservoir simulation, history matching and numerical well testing. This paper presents a technique based on the recently developed wavelet approach to recover flowing rate history directly from the measured PDG transient pressure, under the most common practical conditions described above. In this method, the exact timing of the rate change is identified through wavelet high frequency analysis. Then the rate and pressure are synchronized in every identified time intervals. Since the rate and the frequency amplitude of the transformed transient pressure are proportional, the real rate value in each time interval can be derived under the given common practical conditions. Both synthetic and field examples were used to demonstrate and further validate the developed technique, which showed very promising results.