Analyzing Transient Pressure From Permanent Downhole Gauges (PDG) Using Wavelet Method

AbstractReservoir pressure monitoring during its production life is to evaluate its performance to ensure the effective extraction of hydrocarbon from the reservoir. Continuous reservoir monitoring offers a window of prospects to increase well productivity, while reducing operating costs through an improved and more accurate well performance. These are achieved through analyzing the long term, real time, dynamic transient pressure obtained from Permanent Down-hole Gauges (PDG), which will provide input and vital information for improving the existing reservoir model for flow simulation.Reservoir monitoring during field development can amplify the understanding of the reservoir depletion, compartmentalization, and efficiency of water injection, also the presence of any flow barriers (such as activated fault). On this basis, reservoir management can be more accurate and realistic.In contrast to the data obtained from the traditional well test such as DST, pressure data from PDG is large in quantity (long term up to six years), noisy, multiple phase flow and multiple rate. The key for the analysis of such data set to extract reservoir information is to develop a technique in handling the data, i.e. to make the data analyzable but not losing the true information contained in the data.This paper presents techniques using wavelet transform method for such purpose. These have been developed recently through an industry sponsored research Project. The procedures include PDG data visualization, de-noising, smoothing and "break point" (due to drop of rate and well shut-in) identification through analyzing field examples provided by the sponsors. After this process, transient pressure data (extracted drawn-down and build up) can then be analyzed using current traditional methods and software. The analysis results such as skin factor and reservoir effective permeability can be evaluated in a time lapse fashion to reveal information about the dynamic changes of the reservoir.