The Yasuni National Park is located in the Ecuadorian Amazon. It is the most important reservoir of biodiversity on the planet and home to two peoples in voluntary isolation: the Tagaeri and Taromenane. Below the ground of this park are three oil fields that contain approximately 20% of the country's oil reserves. For these reasons, NOC Petroamazonas EP performed detailed environmental impact studies, with the mandate to use proven technologies to develop the reserves of these fields. Based on this, a drill cutting reinjection feasibility study was conducted in the Apaika field within Yasuni Park.

This paper presents the results of the feasibility study in which all aspects of geoscience and operations parameters that influence the selection of the optimal formation and well injection were integrated: geology, petrophysical, geomechanical, fracture simulations, slurry design, interference analysis, injection rates, well completion, erosion velocities, etc.

The geology and petrophysical analysis included seal analyses to help ensure the containment of slurry (outcrops, natural fractures, and faults), storage (lateral continuity, thickness, effective porosity, clay volume, water saturation, and pore throat radius), and flow properties. Filtrate invasion simulations were conducted considering the volume of drilling waste planned in the field and the maximum volume that could be injected into the formation without affecting neighboring wells (areal interference) and without resulting in fluid loss to formations of interest (vertical interference). Fracture simulations were supported by geomechanical models and calibrated with real-time results in the field. Also, laboratory tests were performed to obtain the optimal slurry. Finally, tubing erosion velocity, casing burst failures, and surface equipment analyses were performed to assess the integrity and condition of the injector well, Apaika 001X.

Implementing drill cutting reinjection feasibility studies in Apaika 001X provided Petroamazonas EP with a definitive solution to the waste accumulation at the surface, helping to minimize the environmental impact in the Apaika field and also to prepare for operations in Yasuni, which is a bigger challenge. Following the recommendations of the feasibility study, a diagnostic formation integrity test (DFIT) was performed in April 2014 to calibrate the geomechanical model. Cuttings were first injected into Apaika 001X in June 2014, making it the first drilling waste reinjector well in Ecuador supported by best practices.

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