Generation of 3D geological model of pre-salt with karst structures

Abstract

Paleokarsts are complex regional unconformities that can be formed during brief periods of exposure and karstification, resulting in low-amplitude dissolution features, or during long term subaerial exposure, leading to the development of mature landscapes characterized by topographic variations of hundreds of meters and by large-scale cave systems (Immenhauser and Rameil, 2011). The identification and evaluation of subsurface paleokarsts are important challenges in carbonate reservoir characterization (Sayago et al., 2012), since karstified carbonates are globally relevant hydrocarbon reservoir rocks able to create important oil fields,for example in NE Alberta (Upper Devonian Grosmont Formation; Bown, 2011), the TarimBasin, NW China (Ordovician carbonates; Zhao et al., 2014), and the West Texas (LowerOrdovician Ellenburger Group - McDonnell et al., 2007). In Brazil, pre-salt carbonates have a great influence on karst features (Cazarin et al 2016).In addition to surface and near-surface karstification, other related processes such as the collapse of cave systems can occur during deep burial of carbonate successions and result incomplex reservoir architectures with high spatial heterogeneity (Sayago et al., 2012). Given the difficulty to access deep reservoirs, three-dimensional seismic imaging is an important tool to the study of paleo-environments and geomorphology (Rafaelsen, 2006). In order to assist the seismic interpretation of karst features, seismic attributes are often used in combination with other data and processing techniques. Thus Zhao et al. (2014) and Tian et al. (2016) integrated well logs, cores and high-quality seismic data including attribute analysis to investigate karst reservoirs in the Tarim Basin. Sayago et al. (2012) applied a multi-attribute seismic classification to characterize a paleokarst in the Loppa High, Barents Sea. Maoshan et al. (2011)developed a directional amplitude gradient technique to identify carbonate-karst reservoirs in the Tarim Basin.For this reason, the objective of this project is to realize a 3D geological model with influence of karst features. This work will be based on the results of the "Characterization and Geological Modeling of Albian Carbonates of the Campos Basin" project funded by Statoil for our research group. In the previous work was characterized karst structures of the Albian of the Campos Basin using seismic attributes. (AU)