Talara Basin, Peru: Structural and Stratigraphic Characterization Based on 3D-Seismic Data

Abstract

Abstract Along the past decades the prolific Talara Basin, located at the northwest part of the Peruvian coast, has been intensively studied based mainly on the huge amount of onshore wells on the area. Beside this, contributions come up from 3D seismic. These contributions are stratigraphic and/or structural analysis, which provide suggestions about reservoir communication, fault movement and optimize well positioning. The reservoir characterization methodology applied on this work used 3D PSDM seismic data. The first step aimed to better understand deep reservoir levels (Lower Eocene and Paleozoic), that are less sampled by wells than upper levels (e.g., Middle Eocene). The second step focused on Middle Eocene reservoirs, sampled by tens of wells with a good geological correlation. From well data and geological interpretation, it is well known that Lower Eocene reservoirs are high energy fluvial systems – this depositional pattern appeared with a distinct seismofacies in the entire seismic cube. Seismic data and well logs showed that Lower Eocene presents more fractures and faults than Middle Eocene. However, the relation between directions and fracture classification as open, semi-open or closed fractures was not conclusive. The seismic facies found at Middle Eocene show sin-depositional differential tectonics movements that could have caused compartmentalization. At this level, seismic facies are very clear, with strong and parallel reflectors, indicating the presence of amalgamated lobes (probably derived from erosion of an eastern ridge located). Identified seismic anomalies were mainly related to structural highs, associated to hydrocarbon saturated reservoirs. An understanding of stress field behavior along geological time is very important to achieve a better trapping model and hydrocarbon migration routes. In this work, the high number of structures observed provided the tools to set up an event chronology. According to the stress history, N70W normal faults acted as migration routes probably during Miocene. Considering the last compressive reactivations (occurred between Upper Eocene and Oligocene) these previously migration routes could be changed to sealing faults.