Benefits and Challenges of Polymer Flooding in a Heavy Oil Field
Authors: Callegaro Chiara , Galeazzi Paolo , Masserano Franco , Tritto Chiara , Moghadasi Leili , Viareggio Alberto , Zuber Joshua , Waggoner John 
Published: February 2024

This work presents the status of inter-well polymer project in a heavy oil field, started with EOR evaluations, followed by laboratory tests for polymer selection, simulation activities and well injectivity tests to predict the effects at a larger scale and drive strategy of the implementation. The pilot results are presented with discussion of polymer benefits and experienced challenges.

The entire EOR workflow was applied. The polymer injection was selected as the most promising technology among different techniques for a heavy oil field, with lab work and preliminary simulations. Injectivity tests were conducted in four wells to assess the injection capacity and select the best injector for the inter-well pilot. A dedicated surveillance program to evaluate the polymer effects was performed: collection of polymer plant (skid) and polymer parameters, real time and downhole data, tracers' analyses. The 3D model was used to assess the polymer potential in the pilot area and extend the beneficial effects.

The field is a shallow-water sandstone heavy oil (50-200 cP) reservoir with good petrophysics, flooded by water since production startup and developed by world class horizontal wells following a line drive pattern. Screening activities, including 3D simulations, highlighted polymer as the best EOR solution. Polymer key characteristics were evaluated through bulk tests and corefloods to identify the best product. Chemical properties were upscaled into the 3D simulation model to optimize forecast scenarios. Results of injectivity tests were modelled to understand and propagate the EOR process to full field scale; this required advanced polymer features (polymer degradation and rheology) to explain the moderate loss of injectivity seen in the field. The inter-well pilot was started in the field in April 2021 with a close data collection and monitoring program. After 2-year of injection, the proof of remobilized oil bank with water cut reduction and oil increase in nearby producers was visible thanks to a continuous injection at target viscosity. 3D reservoir simulations improved the understanding of field results. The pilot gave lessons learned and recommendations for the process extension, especially in a low temperature environment which represents a challenge for the polymer project for plant footprint and logistics. A Life Cycle Assessment was finally performed, estimating a reduction of CO2 emissions with polymer flooding scenarios with respect to waterflood.

The polymer project is the first company experience in a heavy oil reservoir using reinjected produced water for polymer dilution. An integrated laboratory and simulation workflow was applied to select the best polymer and the most favorable EOR strategy. The field experience gave positive key performance indicators in terms of oil production increase and CO2 emissions reduction allowing to gain valuable insights for process extension and to recommend best practices to other operators.