Interpretation of the Performance Results of a Polymer Flood Pilot in the Tambaredjo Oil Field, Suriname
Authors: Delamaide E. , Let K. Moe , Bhoendie K. , Paidin W. R. , Jong-A-Pin S. 
Published: September 2016

A polymer flood pilot has been ongoing since 2008 in Suriname in the heavy oil Tambaredjo field operated by Staatsolie. The pilot started with one injection well and four producers and was subsequently expanded to three injection wells and nine producers.

Initially, a polymer solution with a viscosity of 45 cP was injected and this was later increased, first to 85 cP then to 125 cP in order to improve the sweep efficiency. The response to polymer injection has been positive even though some wells have not responded as expected to the injection. The incremental recovery (over primary) to date is estimated at 11.3% STOOIP. Additionally, some wells outside the pilot have also shown response to injection.

The performance results of the pilot have already been presented in previous paper SPE-180739-MS (Delamaide, Moe Soe Let, Bhoendie, Jong-A-Pin, & Paidin, 2016). The current paper focuses on the interpretation of the performance of the pilot. Several factors have contributed to make this interpretation challenging: the reservoir heterogeneity with permeability of up to 30 darcy (to air) measured in cores and in pressure transient tests; the characteristics and contribution of a water-bearing formation of Cretaceous age below the main reservoir which remains not very well understood. But also the fact that the pilot patterns are not confined; the increases in injected polymer viscosity over the course of the pilot and the role of induced fractures or pseudo-fractures created during the injection of the polymer solution.

Salinity data recorded over the whole production history of the wells was invaluable for the analysis thanks to differences in salinity between the reservoir, the water-bearing Cretaceous and the injection water.

The results of the interpretation of the pilot performance have given a higher confidence for possible future expansion of polymer flood in the Tambaredjo field. Contrary to the common practice of using reservoir simulations to interpret pilots, this work has been conducted with classical reservoir engineering techniques and calculations, and thus presents an interesting case study. Some main conclusions for this project are: Polymer injection has generated an incremental recovery of 11.3% OOIP; Polymer Utilization Factor ranges between 0.41 bbl/kg and 0.57 bbl/kg of polymer.Fluid movement outside the patterns has been observed; it was due to the unconfined nature of the pilot patterns and was probably exacerbated by the limited drawdown imposed on the pattern wells. It is likely that incremental recovery would have been higher had the wells been produced more aggressively.A first response to polymer injection was obtained when a viscosity of 45 cp was injected. Increasing the viscosity further did not result in any obvious increase in oil recovery.

For the future polymer expansion, it is recommended to maximize well drawdown and to reduce injected polymer viscosity to improve the economics (Polymer Utilization Factor).