This paper describes the current development and acquired experiences obtained in a produced water re-injection (PWRI) project in high WOR mature oilfields located in the Amazon rainforest in Peru.
Pluspetrol operates Block 8 and Block 1-AB, both located in the Northern part of Marañon foreland basin in Peruvian jungle. Twenty-four oilfields had been discovered between 1971 and 1980 and they have been producing since 1978. Currently 174 wells are producing from 17 fields with average water cut as high as 95%.
Productive reservoirs are composed of fluvial, estuarine and shallow marine sandstones from Vivian and Chonta formations of Cretaceous age. Main reservoirs have lateral continuity with porosity between 12 and 24% and permeability between 50 md and 5000 md.
The production mechanisms are bottom and edge water drive. It is observed that water cut in these reservoirs shows a very sharp increase to values above 90% in early stages of exploitation due to mobility differences between viscous oil and formation water.
In a first stage a series of injectivity test were performed in both shallow and deep reservoirs. These tests showed a better injectivity in deep reservoirs like Vivian and Pozo.
At the beginning injection rates were under matrix conditions but later with the aid of thermal effect and high injection rates, injection under fracturing conditions was achieved allowing us to increase injectivity index and thus reducing the number of required water disposal wells.