Abstract

The Tarapoa West area in the Oriente Basin of Ecuador was an unexplored area between Fanny-Dorine Field and Shushufindi Field, which was granted to Andes Petroleum Ecuador Ltd. in the 2011 Service Contract negotiation. Very sparse coverage of 2D seismic data and no wells were in the area. Andes decided to acquire 3D seismic over the entire area and merged the new data with existing 3D seismic on the Tarapoa Block to allow an integrated interpretation of new areas and comparison with nearby existing fields and known geological models.

A well planned and executed program consisting of environmental permitting, community negotiations, contractor selection, seismic program design, field testing and acquisition, field processing, final processing, and interpretation all were important, coordinated aspects of creating a successful exploration project in the Tarapoa West Area. Close communication and cooperation of all groups involved from the initial formulation of the concept to exploration drilling and discovery have contributed to a very successful project.

Strictly executed seismic program design and field testing, according to the parameters and imaging of the experiment, and making a comprehensive analysis of the explosives parameters and depths (1.5 kg charge size and single hole depth of 15 meters) obtained better continuity and higher resolution of the effective reflectors. The field records were of good quality and the signal to noise ratio was acceptable throughout the area. A focus on true amplitude recovery, accurate statics calculations and corrections, and accurate velocity analysis during data processing yielded optimal results. The high quality 3D volume allowed us to identify prospects with 4 way vertical closure of less than 5 milliseconds and seismic attribute maps have indicated the lithology distribution reliably. Combining the structure maps and seismic property information maps, and comparing with seismic sections crossing existing oil fields has been useful in calibrating the seismic acquired in the Tarapoa West area. By having a clear understanding of the geological model and target, and by having, from the beginning of the project, close communication and cooperation within the exploration team for the seismic acquisition, including the seismic program design, field testing analysis, processing parameter tests, and procedure design; and for the processing and interpretation phases, a portfolio of reliable, prospective drilling locations were identified. Three prospect trends were found and five exploration wells have been drilled, resulting in TNW, Johanna and Alice west three new fields.

Focusing on the geological target, on seismic acquisition processing and on an integrated interpretation solution has enabled us to not only identify low relief prospects, but also has provided abundant information on lithology distribution. Both aspects have been the key for well location selection.

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