Summary Polymer flooding of oil fields has not reached the same maturity as waterflooding. Hence, implementing polymer projects at field scale requires a workflow comprising several steps. The workflow starts with screening of the portfolio of an organization for oil fields potentially amenable for this enhanced-oil-recovery (EOR) method. Next, laboratory and field testing is required, followed by sector and field implementation and finally rollout in the portfolio. Going through the workflow, not only is the subsurface uncertainty reduced, but also the knowledge regarding the cost structure and operating capabilities of the organization is improved. Analyzing the economics of polymer-injection projects shows that costs can be split into costs dependent on the polymer injector/producer (polymer pattern) and costs that are independent. Knowing these costs, a minimum economic number of patterns (MENP) is defined to achieve net present value (NPV) of zero. This number is used to determine a minimum economic field size (MEFS) for polymer injection, which is taken into account in the screening of the portfolio. A robustness criterion for economic-evaluation purposes is defined as the minimum number of patterns required for economic polymer injection. By use of this criterion, a diagram is derived allowing for screening of fields for polymer economics by use of pattern-dependent and pattern-independent costs and the utility factor (UF). The cost structure reveals how the NPV of polymer projects changes with the number of patterns, incremental oil, and injectivity. Injectivity is particularly important because it determines the chemical-affected reservoir volume (CARV) or speed of production. A sensitivity analysis of the NPV showed that for the cost structure used here, in addition to the polymer costs, the well costs are important for the economics of a full-field polymer-injection project.

As polymer injection has not reached the same maturity as waterflooding, implementing polymer injection projects at field scale requires a workflow comprising screening of the portfolio of an organization for oil fields potentially amenable for polymer injection, laboratory and field testing followed by sector- and field implementation and roll-out in the portfolio. Going through the workflow, not only the subsurface uncertainty is reduced but also the knowledge about the cost structure and operating capabilities of the organization improved. Analyzing the economics of polymer injection projects shows that costs can be split into polymer injector-producer (polymer pattern) dependent and independent costs. Knowing these costs, a Minimum Economic Number of Patterns (MENP) is defined to achieve Net Present Value zero. This number is used to determine a Minimum Economic Field Size (MEFS) for polymer injection which is taken into account in the screening of the portfolio. Defining a robustness criterion for economics, the minimum number of patterns for polymer injection meeting this criterion is calculated. This criterion is applied to generate a diagram allowing for screening of fields for polymer economics using pattern dependent and pattern independent costs and Utility Factor. The cost structure reveals how the NPV of polymer projects changes with number of patterns, incremental oil and injectivity. Injectivity is of particular importance as it determines the Chemical Affected Reservoir Volume (CARV) or speed of production. A sensitivity analysis of the NPV showed that for the cost structure used here, in addition to the polymer costs, the well costs are important for the economics of a full-field polymer injection project.

Nowadays, the injection of dilute hydrolyzed polyacrylamide (HPAM) solutions after water flooding operations is a promising tertiary recovery method. However, the treatment of produced water containing breakthrough polymer plays a challenging aspect in the oil and gas industry. Ensuring good filterability of the produced water for further usage, either pressure maintenance or EOR application, is still a critical issue. Polymer loads in the produced water need to be expected, which can massively influence the separation efficiency of the water treatment system. Especially, the handling of polymer-containing water streams and finding the appropriate technology for the treatment, chemically or mechanically, has a decisive influence on performing a full-field roll out of polymer flooding activities. Aim of this work was to study the impact of back-produced polymer on the water treatment process and to reach the desired injection water quality. Therefore a water treatment plant in pilot scale was used. The unit simulates the main process steps of the water treatment plant Schönkirchen in the Vienna Basin (corrugated plate interceptor, dissolved gas flotation unit, and nutshell filter). The maximum back-produced polymer concentration, which can be handled within the system, was determined. Two different chemical sets (coagulant and flocculant) were tested, regarding their oil and solids removal ability, in presence of different polymer concentrations. At the end of the field study, one of these chemical sets was found, having a hydrocarbon removal efficiency of around 99% in presence of 30 ppm HPAM inlet concentration. Using this set, good removal efficiency and no plugging of the nutshell filter was observed even at high polymer concentrations. The other set led to plugging of the filtration system at relative low polymer concentrations of 8 ppm HPAM and the removal efficiency of hydrocarbons as well as polymer was poor. Based on these results, it can be assumed that the processes of the water treatment plant Schönkirchen are not negatively affected in the presence of up to 30 ppm polymer load in the inlet water stream.

Cost-effective treatment of produced water is crucial for the implementation of EOR technologies. A multi-chamber flotation unit was tested under real-field conditions for a polymer flood of the Matzen field, Austria. The operating conditions, performance, and potential for cost-effective separation were successfully assessed with HPAM polymers for a concentration up to 800 ppm. In order to evaluate the performance of the flotation technology, a comprehensive test matrix for a widespread operating envelope was defined. Characteristics of the feed water were varied by selecting specific production wells from the Torton reservoir. Consequently, a wide range of retention times, oil-in-water contents, oil droplet size distributions, and EOR polymer concentrations were tested. The unit was operated with and without the application of a water clarifier. Performance was evaluated by measuring inlet and outlet water quality parameters via laboratory analyses and an in-line monitoring device. The impact of EOR polymer on the treatment efficiency clearly indicated a turning-point of treatment efficiency dependent on polymer concentration. Produced water conditions of polymer flooding operations are considered harsh due to the impact on oil droplet coalescing behavior and impacted viscosity. The influence of oil droplet size and shearing of polymer versus the impact of retention time on effectiveness was assessed. On-site core-flood tests were performed to evaluate the injection behavior of treated water with different HPAM polymer concentrations and in combination with and without a water clarifier.