APPLICATION OF 4D SEISMIC ATTRIBUTES TO MONITOR RESERVOIR FLUID MOVEMENT AND PRODUCTION DISCREPANCIES: MAUI FIELD, TARANAKI BASIN, NEW ZEALAND

Abstract

4D timelapse seismic data is commonly implemented to monitor reservoir evolution associated with fluid changes over time. This research utilizes seismic attributes and machine learning to improve upon traditional 4D seismic workflows to better understand fluid movement in 4D time lapse seismic data within the C Upper Sand reservoir of the Maui Field off the western coast of New Zealand. This technique is unique as it implements attributes calculated on two separate 3D seismic volumes acquired in different years in the attempt to image changes in fluid types associated with concurrent hydrocarbon production. Additionally, a computed difference volume, looking at the variation between these two original seismic volumes, is analyzed with each attribute for further insights.In particular, instantaneous, spectral, and geometric attributes are utilized to provide a better understanding of reservoir fluid movement in this 4D analysis. Instantaneous attributes, sensitive to frequency and amplitude variations are implemented to track movement of both reservoir gas and water associated with production. Spectral attributes are used to indicate facies heterogeneity throughout the reservoir that may affect fluid flow behavior. Geometric attributes are used to elucidate any previously overlooked reservoir baffles that could prohibit fluid movement through the reservoir as it is produced. Following these attribute calculations, attribute volumes were cross referenced with fluid saturation models and production maps to validate the accuracy of what each attribute is portraying in regards of fluid movement. Additionally, attributes that contribute to the overall understanding of reservoir fluid movement are combined in a principal component analysis (PCA) to accentuate reservoir heterogeneity and changes, spanning from lithologic facies to fluid alterations. After PCA computation, well logs were used to validate the interpretation of geologic reservoir heterogeneity for differential reservoir depletion among zones, finding that baffles and facies that are prone to diagenetic cementation hinder fluid movement. The research concludes that employing a 4D attribute-based workflow aids in a more thorough comprehension of the geologic control of reservoir fluid movement during production in the Maui C Upper Sand over time.