The purpose of this study was to improve the knowledge, increase the quality of the input data for the static and dynamic modeling, and to contribute to define new areas for exploration and production of hydrocarbons in the Cretaceous reservoirs of the Tapi-TTT oilfield, Block 57, northernmost Oriente basin, Ecuador. Specifically, the pursued objectives were: understand the structural context of this oilfield, run sedimentological core descriptions and identify regional sequence stratigraphic surfaces, define major paleoenvironments, describe the paleogeography of the sedimentary area, construct field maps of sediment distribution, run a quality control and interpret the petrophysical data, and characterize the reservoirs. For getting the objectives there were employed two 4-in core samples 102.5-ft in length, well logs, and a conventional study on 122 core plugs of the Tapi-9 well. The study concludes that the Lower T Sandstone reservoir, upper Albian in age, is a good quality clastic reservoir, composed by medium-grained Orthoquarzites, with its petrophysical parameters depending on its sedimentological facies, with the best quality reservoir facies placed in the sandy fluvial- to tide-dominated estuarine realms and the less quality reservoir facies in the medium to upper shoreface clastic realms, and showing a near equal reservoir capacity for fluid flowing in the H & V directions and a great potential of depletion. For the Lower U Sandstone, lower Cenomanian in age, the study concludes that it is a good to excellent reservoir, with its petrophysical parameters depending on its sedimentological facies too, with the best quality reservoir facies occurring in the sandy tide-dominated estuarine realm and the less quality reservoir facies in the silty-sandy (tight) tide-dominated estuarine realm, and showing a different reservoir capacity for fluid flowing in V & H directions and a low potential of depletion but with a high potential of creating stratigraphic traps.

During the drilling campaign in the Tapi field, Ecuador, events of total losses and directional unexpected behaviors were observed. These issues represent a high risk in the operations and required a better understanding of the geological structures. The use of a new Logging While Drilling (LWD) Micro-Resistivity technology was used for the first time in Tapi field, Ecuador to study the geological and geomechanical characteristics of this field in detail.The tool string was run as a penta-combo with a rotary steerable system with the purpose of getting a hole in gauge and consequently a better image quality. The LWD micro-resistivity images tool provided images of the borehole. The interpretation of the Micro-Resistivity Image started showing an average structural dip trend towards NE, identifying a main structural trend of the field.Two post-drill geomechanical models based on wellbore stability were made in the Tapi I and Tapi II wells. Using the LWD micro-resistivity images technology the current geomechanical model was confirmed. Based on the geological information acquired through the image interpretation (natural fractures orientation, breakouts, faults, structural and stratigraphic dips), the geomechanical model uncertainties were minimized.