Diagnostic of changes in reservoir properties from long-term transient pressure data with wavelet transform

For conventional well testing which is carried out over several days or several weeks, reservoir properties are usually assumed to be constant, but this assumption is often not valid for analyzing long-term transient pressure data acquired from a permanent down-hole gauge, which can record down-hole transient pressure data for several years. For example, skin factor may increase due to formation damage, or decrease due to stimulation operations during the time of long-term production. Monitoring changes in reservoir properties is important for reservoir management. This paper proposes a novel method of diagnosing the change in reservoir properties with the wavelet transform. A new diagnostic function has been defined that can detect and quantify changes in reservoir properties. Theoretical analysis and a field example have been conducted and identified to demonstrate this new method and its potential for application in oilfield.