Comparison of History-Matched Water Flood, Tertiary Polymer Flood Relative Permeabilities and Evidence of Hysteresis During Tertiary Polymer Flood in Very Viscous Oils

Abstract

Polymer flooding in very viscous oil has been gaining interest since its efficiency has been field proven. Multiple laboratory investigations have evidenced that the incremental oil recovered by the tertiary process increases considerably the recovery reached thanks to water flooding. However, such tertiary injection is made all the more complex that it is preceded by unstable displacement of oil by water. Therefore a better understanding of the physics is needed, in order to better predict and optimize the viscous oil reserves associated with tertiary polymer flooding. This work presents the interpretation of three similar tertiary polymer flood experiments carried out at the Centre for Integrated Petroleum Research (CIPR, Norway). Each experiment consisted in a water flood followed by a polymer flood. They involved the same Bentheimer outcrop sandstone, 2000 cP oil, 70 cP polymer solution, 2D slab geometry, but different slab lengths (2 slabs are 30cmx30cm, 1 slab is 30cmx90cm). Saturation evolution was monitored by X-ray. On the one hand, provided simple simulation assumptions, the three water floods under study could be history matched (production, pressure). Similar ratios between water and oil relative permeabilities were found, although the water flood relative permeabilities, matched with non Corey-type curves, reflected an important variability. On the other hand, the tertiary polymer floods were found challenging to match consistently. In particular, using classic history matching approaches, the history matching of the long slab experiment could not be reconciled with that of short slab experiments. Simulations were initialized with saturation maps obtained at the end of the water floods. None of the tested approaches enabled us to match consistently the short and long slab experiments together, unless a hysteresis model was implemented. Indeed, a memory effect was observed experimentally from the quantitative analysis of X-ray saturation maps and interpreted as a hysteresis phenomenon. This simple model, with two additional matching parameters, is then further validated by the comparison of 2D simulations with measured in situ saturations.

Historical and recent observations in polymer floods: An update review

“…Canadian polymer floods are a good example of this reporting the injection of polymer solutions between 20 and 50 cP in viscous oil (up to 7,500 cP) reservoirs and recovery factors up to 14% of the OOIP (Delamaide, 2014;Renouf, 2014). These observations have been also reported in recent coreflood studies using viscous crude oils (Fabbri et al, 2015;Romero et al, 2013;Skauge et al, 2014).…”

“…History matching approaches of primary and water injection can also impact the prediction of polymer injection. Input variables required to predict polymer flood performance are also part of the uncertainties that needs to be considered in simulation studies (Aldhuwaihi, King & Muggeridge, 2015;Alkhatib, 2015;AlSofi and Blunt, 2011;Chiotoroiu et al, 2016;Fabbri et al, 2015;Romero et al, 2013;Skauge and Salmo, 2015;Skauge et al, 2016;Zhou, Y., Muggeridge, A. H., Berg, C. F., & King, P. R., 2015). Additionally, commercial simulation tools still have some limitations to properly represent the potential formation of in-situ emulsions and its impact on well injectivity/productivity.…”

Ranking Viscous Finger Simulations to an Acquired Ground Truth with Topology-Aware Matchings

“…The performance and quality of our approach are then evaluated. Acquisition: The detailed experimental setup is that of [29,34], further described in [88][89][90]. We consider slabs of Bentheimer sandstone (30×90×2.45 cm), with porosity of approximately 23% and absolute permeability of 2.5 Darcy (when S w = 1).…”

The Impact of Rheology on Viscous Oil Displacement by Polymers Analyzed by Pore-Scale Network Modelling

“…For example, polymer flooding applied in Pelican Lake showed accelerated oil production at a very adverse mobility ratio. Many other studies have investigated the application of polymer flooding for such heavy viscous oils [ 3 , 4 , 5 , 6 , 7 , 8 , 9 , 10 , 11 , 12 ]. These studies definitively established that, contrary to the conventional displacement theory, significant incremental oil could be produced by injecting the polymer in very viscous oils and this oil was produced in an accelerated manner.…”