Reservoir Imaging Using Seismic Attributes, Pattani Basin, Thailand

Abstract

In the Pattani Basin, Gulf of Thailand, the sand reservoirs of Sand A and Sand B are studied by using seismic attributes to image the reservoir. The reservoirs are Late Miocene age and comprise of moderate to high porosity and permeability sandstones with enclosing mudstone. Seismic attributes are useful for interpreting and presenting as much reservoir detail as possible. The attributes were created by using full stack and partial stack of 3D seismic processing data, well log data and geo-steering data. The first part of the study was aimed to improve seismic quality for understanding sand body distribution. The geological data from well drilling, especially from the results of geosteering, was compared to seismic attributes to define the distribution of thin sand reservoir in Sand A and Sand B. The Middle-Tertiary  Unconform-ity (MTU) that occurs below the reservoir was also mapped using seismic attributes. The seismic attributes include structural orientation filtering, similarity series, geometry attributes, and instantaneous attributes. The attributes were used to improve and identify reservoir distribution images. The result of using seismic attributes for reflector continuity enhancement, structural smoothing or structural orientation filtered is the best for recognizing the discontinuity reflector for unconformity identification. Similarity attribute is used for checking the quality of processing and acquisition before combining with other seismic attributes. The smooth dip of maximum similarity is an interesting attribute for identifying the unconformity of the MTU on the boundary of the basement high. The best sand reservoir identification attribute is the relative acoustic impedance attribute volume that was used with well log data for proving the sand distribution and imaging sand-predictive maps. Multiattribute and composite attributes that are generated from two different seismic attributes can image reservoir distribution within sedimentary basin and depositional features in one image.