Toxic metal pollutants in groundwater should be identified to prevent future health risks. In this paper, the presence of heavy metals in groundwater in the western region of Iraq was investigated. The heavy metals concentrations, including Ni2+, Co2+, Zn2+, Pb2+, Cr3+, Cd2+, As3+ and Hg2+ were explored in twenty selected aquifers near Rutba City and the results were presented as spatial distribution maps. Findings indicate that contamination with the investigated heavy metal ions possesses a serious threat to the study area’s groundwater quality when compared to WHO and IEPA guideline values. Thus, a new approach to remove or adsorb heavy metal ions can be developed for large-scale production and the safe use of these aquifers water. Results revealed that the highest concentrations in mg/L1 of 2.312 in w19, 1.098 in w2, 5.78 in w17, 0.292 in w9, 3.349 in w5, 0.32 in w13, 0.074 in w11 and 5.622 in w1 for Zn2+, Cr3+, As3+, Pb2+, Ni2+, Co2+, Cd2+ and Hg2+ were recorded, respectively.

Efficient production of heavy oil from the reservoirs with strong bottom aquifer has proven to be a challenge. While providing enough energy to produce the field under the primary depletion, the strong bottom aquifer in combination with unfavorable oil/water mobility contrast leads to rapid development of water coning thereby limiting oil recovery. Drilling of long horizontal producing wells in the upper part of the oil column maximizes the distance from the aquifer and allows relatively high production rates. This slows down the water cone development and increases primary recovery. Even with further optimization of the primary production, the recovery factor remains relatively low and consequently application of Enhanced Oil Recovery (EOR) techniques is required to increase the recovery. Сrude oil from Nimr-E field is medium-heavy with the viscosity of 250-700cP under reservoir conditions. The field has been developed with mostly horizontal producing wells with relatively short inter-well distance. Due to strong bottom aquifer the reservoir pressure is maintained at the initial level despite the production under primary depletion. To increase the recovery factor polymer flooding was selected with expectation to increase the recovery by 5-10%. A field trial was conducted to understand the influence of polymer injection on oil recovery and address major uncertainties identified as key enablers for the full-field project. The pilot surveillance program, the surface facilities and the subsurface configurations were specifically designed to meet these objectives. The paper presents field data of polymer injection trial in Nimr field and focuses on the performance results and principal operational challenges. The injection of polymer resulted in the incremental oil production that was assessed using field data and simulations. A significant increase of initial oil production and clear watercut reversal due to polymer injection was observed and incremental recovery reached approximately 7% of the initial oil in place. Injectivity issues encountered in the pilot wells were mitigated by the techniques and chemicals developed to solve the issues. The results prove the subsurface and operational success of polymer field trial that leads the way to a commercial development.

Full field polymer flood has been identified as a potential EOR process for a heavy oil field with a strong bottom aquifer in the South of the Sultanate of Oman. A number of surface and subsurface risks have been identified prior to field implementation, including matrix injectivity, polymer sweep and impact of back produced polymer on surface facility & the field wet lands (reed beds). The development of the field will take a place in a phased manner in order to reduce the capex exposure, maximize the utilization of existing facility and managing project risks while contributing to the overall production. In order to support the standardization and steer the future phases the modular facility concept was selected as basis for polymer preparation and injection facilities, this design was made flexible enough to cater for a wide range of possible trial outcomes. A very comprehensive polymer pilot was performed in this dome-shaped heavy oil reservoir to assess polymer sweep performance as well as losses to the strong water aquifer. An inclusive real-time surveillance programme was executed to monitor key parameters including pressure, injection/production rates, viscosity and water quality, which concluded incremental oil gain from the process. Other tests were conducted to assess the impact of back produced polymer on growth of plants, heater fouling and surface facility separation tanks. In general, all results were positive which paved the way for field-wide development of polymer flooding with less Capex requirement. A sustained incremental oil gain was clearly observed from polymer injection, which was supported by saturation logs acquired from the observation wells. Injectivity could not be maintained as planned, due to a combination of polymer, biological and water quality issues. Later tests including biocide injection and QA/QC of polymer batches as well as some well stimulation did show improved injectivity profiles. Demulsifier tests mitigated the risk of creating stable emulsions. Lab tests indicated no heater fouling observed below 150°Cdeg. Short and long term investigation into the impact of water-contaminated polymer on plants in the wet lands was positive with the plants showing no necrosis with back produced polymer concentrations up to 500 ppm which is achievable given the excessive amount of water received at the facility level that dilute the back produced polymer. This helped in making the project more economically attractive as it results of a saving of around 30% from the overall project Capex. The different surface and subsurface tests paved the way for a full field implementation of polymer injection in structures with strong bottom water aquifer. The paper discusses the phasing that was purused to mitigate risks, learn on the go and improve the project economics

Polymer flooding has been identified as the next phase of developing two heavy oil fields located in the South of the Sultanate of Oman. The fields are supported with a strong bottom aquifer drive that results in large amount of water production due to the adverse mobility. In order to prove the concept of polymer sweep, a field trial was designed and conducted successfully in the field. Moreover, due to the challenges associated to handling back produced polymer number of tests were conducted to assess the impact of polymer on facilitates. Development of the field will take place in a phased manner in order to reduce the capex exposure, maximize the utilization of the existing facility and managing project risks while contributing to the overall production. Dynamic modeling of both fields showed that polymer development is feasible. The modeling work was supported by a field trial that was designed to prove: polymer sweep performance, injectivity, as well as polymer losses to the strong water aquifer. This trial was monitored with detailed surveillance program including pressure, injection/production rates, viscosity and water quality, which concluded incremental oil gain from the process. In parallel, a number of laboratory and field tests were performed to assess the impact of polymer on the surface facilities such as the heater, separation tanks and the growth of the reed beds - wet planets- in the field. Sustained incremental oil gain was clearly observed from polymer injection in the field trial. Injectivity could not be maintained as planned, due to a combination of polymer, biological and water quality issues. Later tests including biocide injection and QA/QC of polymer batches as well as some well stimulation did show improved injectivity profiles. Demulsifier tests mitigated the risk of creating stable emulsions. Laboratory tests indicated no heater fouling observed below 150°C. Short and long term investigation into the impact of water- contaminated polymer on plants in the wet lands was positive with the plants showing no necrosis. This was tested up to back produce polymer concentration levels of 500 ppm. Which is achievable given the excessive amount of water received at the facility allowing the dilution of back produced polymer to the required level. This helped in making the project more economically attractive as it results in a saving of around 30% from the overall project Capex. The modeling exercise proposed drilling of around 200 polymer injectors across both fields, but in order to manage costs and further reduce project risks an optimised phased development approach was evaluated. Both Analytical and modeling approach were used to identify the phasing strategy. The phasing strategy will start with the most attractive to least attractive areas allowing for appraisal these areas prior to committing to their development. The key enabler for phasing of this development is by standardizing and replicating the development. Hence, modular facility for polymer preparation and injection was selected, in which a detailed design will be conducted for the first phase then it will be replicated for the other upcoming phases. Phase-1 of the development will be in the central area as it is has a better response from the model compared to the other areas. This phase will include the drilling of 25 injectors and it will require two modular facilities. 25 to 30 injectors will subsequently be drilled every 2 years for the follow up phases. The different surface and subsurface tests paved the way for a full field implementation of polymer injection in structures with strong bottom water aquifer. The paper discusses the phasing and replication strategy to mitigate project risks, learn on the go and improve the project’s schedules and economics.

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