Reprocessing of 2D Reflection Seismic Marine Data and Investigation into the AVO behavior of Cambrian Sandstones, Southern Baltic Sea, Sweden

Abstract: A seismic line from the 2007 Dalders survey, Baltic Sea, has been re-processed and used along with well data as a basis for an investigation into the AVO behavior of the Faludden Cambrian sandstone reservoir.  Line OP0701-260 is located in the southern part of the Baltic Sea with an approximate length of 52 km. The study profile lies within the Baltic Syneclise which is host to a significant thickness of the Paleozoic sediments. The area has been investigated for years for petroleum exploration and production. The Middle Cambrian sandstones are the most important reservoir rocks for hydrocarbon potential and CO2 storage potential in the Basin. 2D marine seismic data were acquired by Svenska Petroleum in 2007 and processed, but the existence of strong multiples, lack of good seismic image at depth and limited frequencies within the target zone were the significant reasons for reprocessing the data. In this study the seismic data are processed using processing software, Global Claritas, to create a new processing work flow by testing different processes and parameters to improve the processing workflow for a better stacked image. The final stacked image shows improvement in the signal to noise ratio and multiple removals. The improved stacked image shows strong reflections over the Cambrian interval which gives more confidence in the geological interpretation of the data. The B-9 well, which is located 82km south of Gotland in the Baltic Sea, sampled the Middle Cambrian interval, where P-wave velocity and density logs were recorded. Based on the good correlation between the seismic profile and the synthetic log especially for the Faludden sandstone, AVO modeling was performed based on the B-9 well.  The response to changes in gas saturation and porosity within the reservoir sands are investigated. Hampson Russell AVO program was used to study the amplitude variation with offset at the Faludden sandstone interface in the seismic data.  The results show a strong AVO anomaly is not anticipated associated with the Faludden interface. Different synthetic models were run for different petrophysical parameters to investigate how they can affect the AVO and stacked amplitude behavior of the data.