Abstract
A water flooding project was initiated in a mature field in the Oriente basin. The shortage of water production for the implementation required the identification of the water source, an infinite aquifer located at the base of existing wells. Next, well integrity, well schematics, well status, water quality and water demand were used to define the best candidates to be converted from oil producers to water source wells. As part of the operational process several issues were solved by the evaluation and implementation of different solutions. To isolate shallower producing intervals, three technologies were applied: traditional cement squeeze, scabliner and casing patch. The latter resulted to be the best technical solution followed by scab liner and cement squeeze. To avoid residual oil zones at the top of the water source reservoir, it was necessary to create a new operative bottom by drilling out cement, landing collars and float collars at the base of the production liner or casing.
As the well productivity index of the water source wells ranges from 8 to 80 BPD/psi and the reservoir pressure is steady at 4,500 psi, electrical submersible pumps are installed in the 9 5/8 production casing at shallow depths. This configuration reduces operational risks and provides the required discharge pressures to reach the injection points. Over the course of the project the perforated interval for water production was continuously optimized, as pressure and water viscosity are mostly constant, and the absolute permeability is quite homogeneous.
These water source solutions proved to be successful for the first phase of the waterflooding project and were extrapolated to other areas of the asset resulting in 16 wells being converted to water source wells, and 3 wells being recompleted as dump flooding wells.
This document can be used as a guide and set of best practices for recompleting wells to produce high quality water from existing wells by integrating reservoir conditions, mechanical configurations and water demand requirements. The analysis of NPT and UPT will also provide additional clues for converting oil producers to water source wells.
