The Impact of Rheology on Viscous Oil Displacement by Polymers Analyzed by Pore-Scale Network Modelling (original) (raw)
Related papers
2011
The injection of water and/or polymer in extra-heavy oil reservoirs is currently gaining great attention in both the academic and industrial worlds. Water and enhanced water injection schemes represent an interesting alternative in all those cases where thermal methods are either impractical or uneconomic; furthermore several laboratory investigations have already shown that such recovery protocols can provide much higher than expected oil recoveries. On the other hand, because such mechanisms are still poorly understood in virtue of the high fluid complexity, the non Newtonian flow behaviour and the characteristically unstable displacements, it is clear that process optimisation for possible field application remains problematic. Ideally, a combination of efforts would need to be put in place which considers the ensemble of 2-phase flow experiments, simulation at both pore and core scales and rheological measurements. In this work we present such effort: both 2D (30cmx30cm slab) and 1D (30cm long core) experiments of tertiary polymer injection in extra heavy oil (7000cp at 23°C) were carried out on Bentheimer sandstone to quantify the underlying flow mechanisms, the oil recoveries and evaluate the impact of unstable flow on model geometry. Water (enhanced water) saturation maps were accurately measured by means of X-ray scans enabling the visualisation of flow instability development (viscous fingering) with high resolution. High microscopic recovery to secondary waterflooding (up to 30% after 5 PV injected) was achieved in line with previous published investigations; most importantly a rather impressive further gain after polymer flooding (reaching final recoveries of more than 60%) was obtained. In parallel, both bulk and in-situ rheological measurements were performed at different polymer concentrations and flow rates and a precise rheological model for simulation was constructed and entered in a conventional reservoir simulator. Generic simulations were able to match the regional crossflow observed in 2D experiments. A simulation exercise, conducted with the aid of pore scale modelling (PSM) technology to help gathering two-phase flow data, proved very educational in that it allowed transferring results from one rock geometry to other rock structures.
Brazilian Journal of Petroleum and Gas, 2019
The successful use of polymer-enhanced oil recovery observed in the last two decades is leading to effective field implementations. One of the reasons for such positive results in polymer flooding is the integration between laboratory-measured properties and reservoir simulation. Recent reports show that inaccessible pore volume (IAPV) plays a significant role in the apparent viscosity of random coil polymers, such as hydrolyzed polyacrylamide (HPAM). This paper assesses both direct and indirect impacts of IAPV on polymer flooding. This investigation relies on laboratory and field-scale simulations of polymer flooding using CMG-STARS. Simulation cases review the effects of IAPV on production indicators in direct and indirect forms. This study compares laboratory-scale simulations with experimental results and uses quality indicators to evaluate the history matching of both approaches. It relies on a modified benchmark field case to study both approaches in comparison to waterflooding and idealized polymer flooding. Results indicate that IAPV has a small direct impact on production curves. However, data show significant indirect implications of the IAPV on recovery. This effect occurs because the apparent viscosity of HPAM has a direct relationship with IAPV. Although the simulation results were consistent with current literature, the results obtained through the experiments indicate that the most realistic simulation case is achieved when considering the impact of IAPV on polymer viscosity.
Spe Journal, 2018
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Does Polymer's Viscoelasticity Influence Heavy-Oil Sweep Efficiency and Injectivity at 1 ft/D?
SPE reservoir evaluation & engineering, 2019
For heavy-oil-recovery applications, mobility control is more important than interfacial-tension reduction, and therefore importance should be given to the recovery of remaining mobile oil by enhanced sweep efficiency. Although the relative roles of polymer viscosity and elasticity in capillary-trapped residual light-oil recovery have been studied extensively, their roles in sweeping mobile viscous oil have not been explored. Injectivity is vital for heavy-oil-recovery applications, and polymer selection is performed solely using criteria that is based on shear rheology. In this paper, the influence of viscous (shear) resistance and elastic (extensional) resistance of viscoelastic polymer on mobile-heavy-oil recovery and injectivity is investigated through the combination of bulk shear/extensional rheology and single-phase and multiphase coreflood experiments at a typical reservoir-flooding rate of 1 ft/D. Two polymer solutions with different concentrations and salinities are selected such that a polymer with low molecular weight (MW) [hydrolyzed polyacrylamide (HPAM) 3130] provides higher shear resistance than a high-MW polymer (HPAM 3630). Extensional characterization of these two polymer solutions performed using a capillary breakup extensional rheometer revealed that HPAM 3630 provided higher extensional viscosity than HPAM 3130. The results show that the behaviors of polymers in extension and shear are completely different. Two multiphase and two single-phase experiments are conducted at low flux rate to investigate the roles of extensional viscosity on mobile-heavy-oil recovery and high flux rates on injectivity. After 1 pore volume (PV) of polymer injections, higherconcentration and lower-MW HPAM 3130 contributes to approximately 17% higher incremental recovery factor vs. lower-concentration and higher-MW HPAM 3630. The core-scale pressure drop generated by HPAM 3130 is more than twice the pressure drop generated by HPAM 3630. Under low-flux-rate conditions at the core scale, shear forces dominate, and displacing fluid with higher shear viscosity contributes to better sweep. HPAM 3630 exhibits a shear-thickening phenomenon and possesses the apparent viscosity of approximately 90 cp at the flux rate of approximately 90 ft/D. In contrast, HPAM 3130 continued showing shear thinning and has the apparent viscosity of approximately 70 cp at approximately 90 ft/D. This signifies the role of extension rheology on the injectivity at higher flux rates. Results revealed that while the extensional rheological role toward sweeping the mobile heavy-oil recovery at low flux is lesser compared with the shear role, its negative role on the polymer injectivity is very significant. Polymer-selection criteria for heavy-oilrecovery applications should incorporate extensional rheological parameters.
Pore Scale Modelling of Polymer Flow
IOR 2013 - 17th European Symposium on Improved Oil Recovery, 2013
Polymer flooding as an EOR method that has boomed in the last decade as oil prices have been rising, and new and larger polymer flood projects are being realized. Some milestones and examples are the largescale viscoelastic polymer flood implementation at the Daqing field in China, polymer injection in Marmul field, Oman, and the Dalia offshore polymer project. Polymer flood is a mature EOR technology, but as the reservoir targets get more diverse and the field conditions harsher, the current understanding of polymer flood is stretched to its limits. In order to explain viscous fingering in inter-mediate to heavy oil reservoirs and viscoelastic mobilization of residual oil there is a need for a better understanding of polymer flow mechanisms on the pore scale. Pore scale polymer flow characterization is very complex and involves several flow phenomena like; adsorption, viscous fingering, depleted layers, hydrodynamic retention, bridging/flow-induced adsorption, viscoelastic effects, in-accessible pore volume and more. In this study we have developed a Navier-Stokes model to analyse polymer flow and to compare against Newtonian fluids. The aim has been to identify the key parameters for polymer displacement. Examples of obtained results are that the depletion layer plays a major role in study of rheological properties. Increased depleted layer thickness lead to lower velocity at the centre of the pore and more slip effect near the pore wall. When a higher degree of shear thickening is included a larger drag on fluids in side channels will occur, this is consistent with oil mobilisation and lowering of residual oil saturation.
Journal of Applied Polymer Science, 2018
High molecular weight polymers used for heavy oil recovery exhibit viscoelasticity that can influence the oil recovery during chemical enhanced oil recovery. Different polymers having similar molecular weight and shear rheology may have different elongation flow behavior depending on their extensional properties. Displacing slugs are more likely to stretch than shear in tortuous porous media. Therefore, it is critical to seek an analytical tool that can characterize extensional parameters to improve polymer selection criteria. This article focuses on the extensional characterization of two polymers (hydrolyzed polyacrylamide and associative polymer) having identical shear behavior using capillary breakup extensional rheometer to explain their different porous media behavior. Maximum extensional viscosity at the critical Deborah number and Deborah number in porous media classified the associative polymer as the one having high elastic-limit. Extensional characterization results were complemented by significantly higher pressure drop, marginally increased oil recovery of associative polymer in porous media.
2014
One of the most important criteria for evaluating chemical enhanced oil recovery (EOR) processes that use polymers is its rheological behaviour which in turn account for other physical effects of adsorption and resistance factors during polymer-formation rock interactions. However, complete knowledge of behaviour of polymer solution in porous media has not yet been fully gained. A computational fluid dynamics (CFD) simulations implemented in COMSOL Multiphysics is used to simulate a 1-D single- phase, non-elastic xanthan gum flow in geometries approximating formation pore throats. Simulation results show the degree of solution viscosity degradation at different inlet pressures and shear rates at varying pore constriction diameters. Results also show that numerical techniques can predict the performances of polymer solution applications in actual field operational conditions and aid in design and interpretation of laboratory tests.
Transport of Polymer Particles in Oil–Water Flow in Porous Media: Enhancing Oil Recovery
Transport in Porous Media, 2018
We study a heuristic, core-scale model for the transport of polymer particles in a two phase (oil and water) porous medium. We are motivated by recent experimental observations which report increased oil recovery when polymers are injected after the initial waterflood. The recovery mechanism is believed to be microscopic diversion of the flow, where injected particles can accumulate in narrow pore throats and clog it, in a process known as a log-jamming effect. The blockage of the narrow pore channels lead to a microscopic diversion of the water flow, causing a redistribution of the local pressure, which again can lead to the mobilization of trapped oil, enhancing its recovery. Our objective herein is to develop a core-scale model that is consistent with the observed production profiles. We show that previously obtained experimental results can be qualitatively explained by a simple two-phase flow model with an additional transport equation
The goal of enhanced oil recovery is to improve sweep efficiency in the reservoir by the injection of artificial materials in order to reduce the trapped oil saturation. In this study, the application of an anionic polyacrylamide polymer was investigated for heavy oil recovery based on the results of rheological measurements and oil recovery experiments. The properties of the polymer solution were interpreted by the use of well-known rheological models and oil recovery experiments were performed using a heterogeneous two-dimensional glass micromodel saturated with heavy oil of 270 cP. To provide a better understanding of the microscopic efficiency of the process, analysis of continuously provided pictures during the experiments by the use of image processing technique was performed. Rheological results combined with microscopic observations revealed that the non-Newtonian behavior of the solution enhances the sweep efficiency of the both pore throats and pore bodies. Macroscopic observations showed the ultimate oil recovery of 56% and dramatic improvement in breakthrough time during polymer flood in comparison to water flood. In addition, the microscopic pictures disclosed that the pulling effect and stripping mechanisms are responsible mechanisms for the high microscopic sweep efficiency during polymer flooding.