High-Resolution Resistivity Image Interpretation to Improve Stratigraphic Model of the ITT Field – Oriente Basin, Ecuador

Abstract

Abstract The Oriente Basin is an oil-rich province located in Ecuador, where the main reservoirs were deposited during the Late Cretaceous. The distribution and thickness of the sandy reservoirs vary from East to West of the basin. For that, most of the reservoirs are amalgamated to the East and the definition of the contacts between them are difficult. The ITT oil field is located in this area and the main reservoir correspond to M1 Sandstone Member of the Napo Formation. However, in certain areas, the contact between M1 Sandstone Member of Napo Formation and the Basal Tena Member of the Tena Formation is hard to discern. The primary objective of this study was determined if the sandstones beds present in the well TMB-081 of the ITT oil field in the Oriente Basin- Ecuador belong to the same formation or not, based on analysis of high-resolution, resistivity-based borehole images. The structural analysis of the image show that the sandy interval to the top of the well is in the same structural zone, which suggest that they were deposited in the same sedimentological conditions. Additionally, the sedimentological analysis shows that textures of the image can be linked with lithofacies defined for deltaic environment in previous works. Finally, the paleocurrents direction suggest that the sediments source rock was located to the South and East of the ITT Field. The contact between Napo and Tena formations is a regional discordance. Therefore, if all sandy interval is in a single structural zone meaning that they belong to the same formation. Additionally, the direction of the paleocurrent suggest that the origin of the sediments is the Amazonian Craton and not the Andes for these sandstones. In conclusion, the sandstones located to the top of the well TMB-081 correspond to the M1 Sandstone and not to the Basal Tena Sandstone. This definition only can be defined using high-resolution resistivity-based images because the conventional logs can provide this type of information.