Abstract

The Guando field in Colombia, South America, is a sandstone reservoir with an initial pressure about 150 psi at GOC. A waterflood has been implemented since early in the life of the field. A complete set of data has been maintained on each of the injectors since 2002. This data set includes: daily injection rates, pressures, water quality and solids analysis. Injection into four different hydraulically fractured reservoir units is controlled by down-hole valves. In some cases wells are operated at injection pressures above the fracture gradient.

To ensure good reservoir sweep efficiency, waterflood control and assurance of injectivity for each reservoir unit a detailed study of the injectivity of each injector was undertaken to understand the possible growth of fractures and its impact on frac-pack injectivity, injection profile and oil recovery. Field data indicates that the quality of river and produced water streams, mechanical configuration, stimulation of injector wells and injection facilities are important parameters that control the injectivity behavior.

Injection well simulations are presented to show that the injectivity behavior can be history matched quite well and this process provides valuable insight into the dependence of injection parameters such as injection rate and water quality on injection profiles and fracture growth. This paper presents data and history match simulations for seven injectors from the field. The results allow us to estimate the fracture lengths that are created in the injectors and to thereby evaluate the effectiveness of injection schemes being implemented. This history match study allowed us to make recommendations for future injection rates and water quality into each of the injectors.

To the best of our knowledge this is the first time that the injectivity of multi-layered, frac-packed injectors has been history matched with field data over an extended period of time. These history matched results validate our injection well model for frac-packed injectors and provide important guidance on future injection well design in addition to making concrete recommendations for the Guando field.

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