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Evaluation of GEOR 1 as
     an Additive for Enhanced
                 Oil Recovery




Prepared by:
Professor Andrew Hurs...
Evaluation of GEOR 1 for EOR



                                                                Page

Summary             ...
Evaluation of GEOR 1 for EOR


Summary
Water flooding with GEOR 1 significantly enhances recovery of heavy oil. The
presen...
Evaluation of GEOR 1 for EOR




Images of the beadpack before and after flooding with GEOR 1 in Table 1.1 and
1.2 show th...
Evaluation of GEOR 1 for EOR




Table 1 Summary of results
               Oil                             Watercut during...
Evaluation of GEOR 1 for EOR



  Table 1 Continued
                    Oil                               Watercut
       ...
Evaluation of GEOR 1 for EOR


1.1 Introduction, aims and objectives
Experiments were designed and conducted to test under...
Evaluation of GEOR 1 for EOR


   •   Can GEOR 1 enhance oil recovery?


   •   Is GEOR 1 stable and effective in both fre...
Evaluation of GEOR 1 for EOR


1.2 Previous chemical EOR
Although there is a considerable literature on chemicals that enh...
Evaluation of GEOR 1 for EOR


microbially produced biosurfactants. Although GEOR 1 is used at low
concentrations, and for...
Evaluation of GEOR 1 for EOR


2.0 Experimental method
A microfluidic beadpack was adapted to allow the preliminary evalua...
Evaluation of GEOR 1 for EOR


solutions of 5 ppm concentration. GEOR 1 was not explicitly tailored or adapted
for the hea...
Evaluation of GEOR 1 for EOR


Further details
The device used in this study is not a micromodel but a micro-scale beadpac...
Evaluation of GEOR 1 for EOR


3.1 Heavy oil production using different EOR techniques
Fluid flow during experiments was d...
Evaluation of GEOR 1 for EOR


                    1



                   0.8       Primary Recovery                  5 p...
Evaluation of GEOR 1 for EOR


Making a comparison between the hotwater and GEOR 1 flood experiment is a
little more compl...
Evaluation of GEOR 1 for EOR


                        1


                                                      Hot water...
Evaluation of GEOR 1 for EOR


3.2 Further analysis
Analysis of fractional flow curves provides a means to predict how wat...
Evaluation of GEOR 1 for EOR


The fractional water-flow behaviour for the coldwater experiments are shown in
figure 3.5. ...
Evaluation of GEOR 1 for EOR




Figure 3.6 presents the results for the thermal EOR experiments. An initial a drop
in oil...
Evaluation of GEOR 1 for EOR


late stage extended flooding with GEOR 1 in saltwater is characterised by an
increasing wat...
Evaluation of GEOR 1 for EOR


3.3 Areal Sweep Efficiency


            Unswept regions after coldwater flood




        ...
Evaluation of GEOR 1 for EOR


phase. A thermal method would be expected to mobilise heavy oil in such
regions by the cond...
Evaluation of GEOR 1 for EOR


4.0 Conclusion
The presence of very low concentrations of GEOR 1 in injected water
signific...
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University Report on Effectiveness of GLENSOL as Oil Remediation Additive

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A research report by the University of Aberdeen on the GLENSOL Oil Remediation Additive - Evaluation of GEOR 1 as an Additive for Enhanced Oil Recovery

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University Report on Effectiveness of GLENSOL as Oil Remediation Additive

  1. 1. Evaluation of GEOR 1 as an Additive for Enhanced Oil Recovery Prepared by: Professor Andrew Hurst Dr Stephen Bowden Dept Geology and Petroleum Geology, University of Aberdeen, Aberdeen Scotland 06 July 2009
  2. 2. Evaluation of GEOR 1 for EOR Page Summary 2 Introduction 6 Experimental Method 10 Results Recovery Efficiency 13 Fractional Flow analysis 17 Notes on Areal Sweep efficiency 21 Conclusion 23 Abbreviations cp; centipoises EOR; Enhanced oil Recovery GEOR 1; Glensol mixture used for experiments HO; heavy oil M; mobility ratio 1
  3. 3. Evaluation of GEOR 1 for EOR Summary Water flooding with GEOR 1 significantly enhances recovery of heavy oil. The presence of a low concentration (5 parts per million) increases the amount of oil recovered and reduces watercut. Relative to flooding with coldwater (20 deg C) or hotwater (>85 °C) flooding with GEOR 1 brings forward production of heavy oil. A single GEOR 1 additive is effective for both saltwater and freshwater. Many surfactants and emulsifying agents achieve very high levels of oil recovery but GEOR 1’s efficiency at low concentrations and in both salt- and freshwater set it apart. These two distinguishing features suggest the potential to succeed in the field where other chemical methods of enhanced oil recovery have failed. Previous chemical methods of enhanced oil recovery have depended on laboratory studies to adjust and optimise surfactant solutions prior to field application. GEOR 1’s efficiency at low concentrations combined with its improved economic efficiency would help to mitigate the marginal nature of chemical EOR methods: e.g. surfactant loss would be less significant economically and should increasing the concentration of GEOR 1 to improve recovery be necessary this need not significantly impact project-margins. Results for preliminary coreflood experiments are summarised in Table 1.1 and 1.2. During all experiments a flood with coldwater (20 deg C) was performed to drive a ~10000 cp heavy oil from a beadpack (the primary oil recovery phase). Subsequent to this an EOR method is applied (flooding with GEOR 1or hotwater or an extended flood with coldwater). The EOR phase was extended by flooding with an equal pore volume. For both cold- and saltwater, enhanced oil recovery by flooding with GEOR 1 greatly increased oil recovery and reduced watercut relative to continued flooding with coldwater. Increases in oil recovery and reductions in watercut achieved by GEOR 1 compare favourably or exceeded those of hot water. 2
  4. 4. Evaluation of GEOR 1 for EOR Images of the beadpack before and after flooding with GEOR 1 in Table 1.1 and 1.2 show the recovery of oil from bypassed regions. Relative to other methods GEOR 1 appeared efficient at accessing zones of bypassed oil. GEOR 1 was originally developed to remove heavy oil residues to remediate contaminated land and clean surfaces. In this application GEOR 1 acts rapidly, penetrating asphaltic deposits to clean oil from surfaces. This ability appears to transfer to a dynamic environment at the laboratory-scale, and would be crucial at the field scale if it improved the access of an EOR fluid to oil bypassed by the initial water flood. 3
  5. 5. Evaluation of GEOR 1 for EOR Table 1 Summary of results Oil Watercut during Recovered† EOR‡ % Image before Image after EOR Reduction EOR EOR phase Extended Average Primary Lowest †† phase EOR ‡‡ Freshwater 37 33 70 93 (55) 64 67 -10 GEOR 1 5 μL/L 27 67 90 40 60 67 -15 (60) 10 27 37 (30) 80 82 +5 Coldwater 55 27 43 16 85 85 +11 (37) 27 40 – 13 65 85 -28 Hotwater >70 ºC 80 – 85 ºC 46 – 64 78 -28 16 Hotwater 36 -38 63 – 55 71 85 ºC (57) -10 4
  6. 6. Evaluation of GEOR 1 for EOR Table 1 Continued Oil Watercut Recovered† during EOR‡ Image before Image after EOR Reduction Extended Average Primary Lowest % EOR phase‡‡ phase EOR EOR †† Saltwater GEOR 1 35 72 83 37 40 51 -31 5 μL/L (54) Coldwater 40 50 10 50 66 +27 (20) † Oil Recovered = the % of oil initially in place recovered. Primary recovery = % recovered after waterdrive; EOR = % recovered after equal volume of water to primary phase used to implement EOR technique; Extended = % recovered after extension of EOR phase. Approximately equal pore volumes used for each experiment. †† % EOR = % of oil initially in place recovered by first EOR technique, number in brackets is % enchantment in oil recovery. ‡ Water cut during EOR . Note that for extended flooding there is no reduction, hence this number is positive. ‡‡ Water is entering from the top of the page and oil exiting from wells at the bottom. Coloured lines identify regions of different shading, where shading is being used as a proxy for oil saturation. Blue is highest saturation and yellow lowest. 5
  7. 7. Evaluation of GEOR 1 for EOR 1.1 Introduction, aims and objectives Experiments were designed and conducted to test under laboratory conditions whether there is evidence that GEOR 1, a chemical additive, has the potential to enhance the direct recovery of heavy oil from reservoir rocks. The background for the experimental work is a history of successful applications of GEOR 1 to dispersal of heavy-oil pollution, remediation of oil-contaminated sand and cleaning and unblocking of oil transport infrastructure (pipelines and storage tanks). The success of these downstream applications coupled with their cost effectiveness and environmental friendliness encouraged Glensol, the manufacturers of GEOR 1, to evaluate possible use of the additive to enhance oil recovery from natural reservoir rocks. GEOR 1 was successfully tested by Glensol as an extraction method for mined and quarried tar and oil sands. If significant improvement in heavy-oil recovery is possible by using a chemical additive it opens the way for step changes in the recovery of heavy oil both in terms of recovery efficiency and cost per barrel of oil recovered. The aim of this study is use simple laboratory experiments to verify that a low concentration of GEOR 1 added to water can enhance the recovery of heavy oil from reservoirs. Recovering heavy oil from the subsurface in a dynamic environment is very different to extracting bitumen from sand at the surface. Therefore specific objectives are required to benchmark any enhancement in recovery observed for GEOR 1 compared to extended flooding with coldwater and hotwater, with particular attention being paid to factors unique to flow through porous media. These factors are the rate of oil recovery relative to chosen benchmarks, and how much water is produced along with a given volume of oil. Additional objectives were to observe the behaviour of GEOR 1 in both salt and freshwater systems and differentiate GEOR 1 from previous methods of chemical-enhanced oil recovery. Specific questions to answer are: 6
  8. 8. Evaluation of GEOR 1 for EOR • Can GEOR 1 enhance oil recovery? • Is GEOR 1 stable and effective in both fresh and salt water? • How efficient is GEOR 1 in comparison to alternative methods of EOR? • How does GEOR 1 improve upon other chemical methods of EOR? Positive outcomes for the experiments above provide a basis for planning and designing field tests of GEOR 1 in conventional heavy-oil reservoirs. The experiments are designed to give oil-field operators a clear indication of the likely benefit of using GEOR 1 in a commercial context. 7
  9. 9. Evaluation of GEOR 1 for EOR 1.2 Previous chemical EOR Although there is a considerable literature on chemicals that enhance oil recovery there have been few successful commercial projects. General textbooks on reservoir engineering tend to characterise chemical methods of enhanced oil recovery as being economically marginal and technically complex, although rarely for a common reason. Foremost is that the cost of the surfactants can be expensive relative to the value of any increase in oil recovery. This is further compounded by the possible loss of surfactants to the reservoir formation during floods. Furthermore in many field situations it has been difficult to bring the injected water containing EOR- chemicals into contact with bypassed oil – the injected water containing EOR chemicals simply flows around regions that contain residual oil. Technical problems are caused the sensitivity of surfactant properties?? to differing reservoir formation water chemistry and mineralogy, which necessitate a design stage to specifically tailor a combination of surfactants and their co- surfactants for particular reservoir characteristics. A miscalculation or false assumption about reservoir rock and fluid properties at an early design stage has the potential to cause failure for a chemical EOR project at the field scale. Therefore in addition to the costs of implementing a field-scale EOR project a considerable investment is also necessary at the design stage, thus a chemical EOR project is inherently risky, may take along time to bring to fruition and even longer to pay back a financial investment. The chemical composition of GEOR 1 is confidential and thus it is hard to place within the schemes typically used to characterise chemical EOR techniques. Previous characterisations of EOR treatments similar to GEOR 1 include low and high concentration surfactant floods, techniques that form surfactants using chemicals already present in the oil (alkali flooding) and those that use 8
  10. 10. Evaluation of GEOR 1 for EOR microbially produced biosurfactants. Although GEOR 1 is used at low concentrations, and forms water in oil micro emulsions, the producers of GEOR 1 believe that GEOR 1 does not fit easily within any currently used classification. 9
  11. 11. Evaluation of GEOR 1 for EOR 2.0 Experimental method A microfluidic beadpack was adapted to allow the preliminary evaluation of water flooding with GEOR 1 as a method of enhanced oil recovery for heavy oil. During experiments the bead-pack was flooded with heavy oil and to promote the aging of the system to an oil-wet state it was warmed at 30 ºC. The device was cooled to room temperature before use. Two or more phases of recovery were used. The first phase comprised primary recovery by water drive. During this stage coldwater (20 ºC) was used. Second and subsequent phases comprised flooding by one of three techniques; 1) coldwater (20 ºC), 2) hotwater between 70 to 85 ºC or 3) water with a 5 μL/L (5 ppm) concentration of GEOR 1. The beadpack was videoed during the experiments and still-images were point-counted to measure water saturation and the volume of fluids exiting the bead pack. The methodology is summarised in figure 2.1. Table 1 lists the experiments performed for the evaluation of GEOR 1 as a heavy oil recovery additive and the details of additional experiments whose results are presented here for evaluation purposes. Table 2.1 Experiments used for report Water type EOR method Other details Freshwater GEOR 1 5 μL/L concentration GEOR 1 duplicate Coldwater comparison Hotwater comparison experiments at 70, 80 and 85 ºC Saltwater GEOR 1 5 μL/L concentration Coldwater comparison Heavy Oil and Water The oil used is from Siljian (Sweden) and has an asphaltene + resin content of 36 %, an API value of 18 o/ ~10 000 cp. Tap water (TDS < 500 mg/L) was used for freshwater floods and seawater for saltwater floods (TDS ~ 35 000 mg/L). The same stock solution of GEOR 1 was used to make up saltwater and freshwater 10
  12. 12. Evaluation of GEOR 1 for EOR solutions of 5 ppm concentration. GEOR 1 was not explicitly tailored or adapted for the heavy oil and bead pack used in this study. 1) Channel with 2) Channel packed with bead trap beads 3) Oil flown into 4) Water flown into channel channel ~ 48 μm 5) Volume of oil and water in draining Bead diameter/ Grain size: 22 μm wells counted Porosity: ~ 46 % 800 μm 6) Before and after images of gravel pack analysed Figure 2.1 Photo graphs of device, and device before and after heavy oil is emplaced. Schematic diagram of method, showing different stages of an experiment. 11
  13. 13. Evaluation of GEOR 1 for EOR Further details The device used in this study is not a micromodel but a micro-scale beadpack. The key difference between the two techniques is that the beadpack creates true 3D tortuousity. The sodalime glass-beads used for experiments are a high sphericity 22 micrometer diameter particle-size standard. Beads were introduced through a channel 500 micrometers in breadth and ~46 micrometers in depth until a pack of suitable length accumulated behind a gap filter. A picture of the device and an image of the channel packed with beads is shown in figure 2.2. Prior to use the pack was flushed with the water appropriate to the experiment and the oil flown in to the pack at high flow rates/pressures. Prior to each experiment the device was warmed to 30 oC to promote the adhering of oil onto the beads to create an oil wet system. During experiments the beadpack and the draining wells were videoed. Image stills were point-counted to obtain water saturation and fractional watercut. When measuring fractional water-cut, blocked-wells were excluded from calculation of the parameter. The device was fabricated at the James Watt-Nano Centre at the University of Glasgow in cooperation with Professor Jonathan Cooper, experiments were performed at the Dept of Geology and Petroleum, University of Aberdeen. 12
  14. 14. Evaluation of GEOR 1 for EOR 3.1 Heavy oil production using different EOR techniques Fluid flow during experiments was driven by the circulation of water with the data collected including the volume of water injected into the device, the percentage of water in the beadpack and the percentage of water exiting through the draining wells 1 . These three measurements represent the time taken to recover a given quantity of oil, the amount of oil recovered out of the total available and the proportion of oil recovered relative to water. The amount of oil produced per volume of injected water is plotted in figures 3.1. and 3.2. Extended phases of recovery are denoted by dashed lines, but the following discussion refers to the first phase of enhanced oil recovery. Relative to flooding with hotwater and coldwater, flooding with GEOR 1 brought forward production significantly. This is illustrated in figures 3.1.and 3.2 by GEOR 1 attaining its maximum displacement of oil for the circulation of lower pore volumes in comparison to the hot- and coldwater experiments. Although the overall volume of oil displaced is similar for both hotwater and GEOR 1, the key difference is that GEOR 1 attains this far more rapidly (a Welge displacement efficiency calculation suggests that to recover 70 % of the oil initially in place more than 50 pore volumes of cold-freshwater would have to be circulated). Fractional water-cut is a measure of the proportion of water produced relative to oil. Because of the viscous and asphaltic nature of the heavy oil used during the experiments water is significantly more mobile than oil during the primary water- flooding. This is particularly notable for the cold-freshwater experiment where the watercut was very high from an early stage in the experiment (figure 3.3). This continued during extended flooding with cold-freshwater. In contrast coldwater flooding with GEOR 1 added significantly reduced or suppressed the fractional water-cut. 1 The higher the amount of water in the bead pack the greater the amount of oil displaced and recovered. Similarly; either water or oil is exiting the device so the greater the percentage of water exiting the device the lesser the percentage of oil recovered. 13
  15. 15. Evaluation of GEOR 1 for EOR 1 0.8 Primary Recovery 5 ppm Glensol Water saturation 0.6 Cold water 0.4 Hot water 85+ ºC 0.2 Hot water 75 to 80 ºC 0 1 0.8 5 ppm Glensol 0.6 Cold water 0.4 0.2 0 0 5 10 15 20 25 30 35 40 45 50 Pore volume injected subsequent to water break through Figures 3.1 and 3.2. Graphs illustrating the recovery of oil by displacement with water. All unfilled symbols e.g. □, ○ etc refer to data for primary recovery phases. Shades symbols: ■▲ = data obtained for Glensol; ● = data obtained for cold water; + = data for hot water experiments. Dashed lines show extended flooding with Glensol. 14
  16. 16. Evaluation of GEOR 1 for EOR Making a comparison between the hotwater and GEOR 1 flood experiment is a little more complicated due to differential changes in volume in the oil phase brought about by the two EOR techniques. It is likely that the overall reduction in water-cut brought about by GEOR 1 is at least equitable to that of the hotwater method if not greater. The minimal water-cut values attained by both techniques are about 60 % for the freshwater/heavy oil system (figure 3.3.). The saltwater/heavy oil system exhibited higher recoveries of the oil in place. The presence of saltwater changes how heavy oil interacts with solid surfaces (lowering the contact angle between the oil and water phases on wetting surfaces). For an oil-wet system the decrease in contact angle or wetting preference in saltwater can increase the mobility of the oil phase causing it to be more easily mobilised than in a freshwater/heavy oil system. The effect of this change in wetting preference can be seen by comparing figure 3.1 and 3.2, where considerably more oil is mobilised during flooding with saltwater than with freshwater. The behaviour of GEOR 1 in a saltwater system is important in two respects: 1) does GEOR 1 have an effect above that of using cold-saltwater alone and 2) is GEOR 1 stable in both a fresh and saltwater environment? Firstly; flooding with GEOR 1 in a saltwater system brought forward production significantly and recovered more oil than cold-saltwater alone, but most notably it reduced water- cut by about 40 % (figure 3.4). Secondly, the same GEOR 1 batch enhanced oil recovery in both freshwater and saltwater/ heavy oil systems. This is highly significant because it broadens the scope of applicability for GEOR 1-flooding as an EOR-technique. Previous surfactant flood and EOR techniques that utilised micellar solutions have been highly sensitive to formation water chemistry requiring a pre-flush to condition formations or the tailoring of surfactants for specific formation water chemistries. For both salt- and freshwater a GEOR 1 flood recovered 70 % of the oil in place. 15
  17. 17. Evaluation of GEOR 1 for EOR 1 Hot water 75 to 80 ºC 0.8 Fractional water cut 0.6 Hot water 85+ ºC 5 ppm Glensol 0.4 0.2 0 1 0.8 0.6 0.4 0.2 0 0 5 10 15 20 25 30 35 40 45 50 Pore volume injected subsequent to water break through Figure 3.3 and 3.4. Graph of the fraction of water exiting the device. All unfilled symbols e.g. □, ○ etc refer to data for primary recovery phases. Shades symbols: ■▲ = data obtained for Glensol; ● = data obtained for cold water; + = data for hot water experiments. Dashed lines show extended flooding with Glensol. 16
  18. 18. Evaluation of GEOR 1 for EOR 3.2 Further analysis Analysis of fractional flow curves provides a means to predict how water flooding could operate at a bigger scale and also helps to characterise processes and mechanisms that are enhancing oil recovery during a GEOR 1 flood. The simplest estimate of water flood efficiency is the mobility ratio, a parameter that balances the viscous forces of one fluid phase against another; a mobility ratio less than 1 characterises an efficient water flood regime and a ratio much greater than 1 is an inefficient water flood. The mobility ratio estimated for the cold-freshwater experiment is approximately 500 following water breakthrough. Primary Recovery Extended water flood 100 Fresh water Sea water 80 fractional water cut % 60 100 99 80 M>4 2.5 0.25 40 5 M=2 Wct % 60 M= M= 40 20 20 0 0 0.2 0.4 0.6 0.8 1 Water saturation 0 0 0.2 0.4 0.6 0.8 1 Water saturation Figure 3.5. Fractional flow behaviour of beadpack. ○● = data for primary and advanced stages of cold- freshwater flood (solid blue line); ∆▲ = data for primary and advanced stages of cold-saltwater flood (dashed blue line). Inset shows behaviour for idealised mobility ratios. Wct % = fractional water cut and M = mobility ratio. 17
  19. 19. Evaluation of GEOR 1 for EOR The fractional water-flow behaviour for the coldwater experiments are shown in figure 3.5. After a small amount of heavy oil has been produced (water has displaced oil from the beadpack thus increasing water saturation), water-cut values are high. For comparative purposes fractional water-cut curves are also shown for idealised systems with lower mobility ratios. Comparison of these systems to the one used for experiments highlights the difficulty of producing heavy oil: if a watercut of 80 % represented the operating limit for a given field, then production of a heavy oil deposit with the characteristics of the micro- beadpack would have to cease after production of less than 10 % of the movable oil in place. For the lowest mobility ratio illustrated, with a low viscosity oil this would be about 50 % of the oil in place. 100 80 oC 70 oC 85 oC 80 fractional water cut % 60 100 80 t Oil we 40 et 60 Wct % ter w Wa 40 20 20 0 0 0.2 0.4 0.6 0.8 1 Water saturation 0 0 0.2 0.4 0.6 0.8 1 Water saturation Figure 3.6. Fractional flow behaviour during thermal EOR, note wetability inversion at highest temperature. Blue line from figure 3.5. Redlines = thermal EOR data.. × = data for hot water at 70 oC, + = 80 oC and ○ = data for 85o C. 18
  20. 20. Evaluation of GEOR 1 for EOR Figure 3.6 presents the results for the thermal EOR experiments. An initial a drop in oil viscosity for temperatures in the 70 to 80 oC range increases recovery o marginally, but at temperatures greater than 85 C a completely different fractional flow behaviour results. The concave upwards graph is characteristic of the fractional flow behaviour observed for low viscosity water-wet systems and describes a situation where increased oil recovery is accompanied by relatively minor increases in fractional water-cut. 100 80 Fresh water Glensol fractional water cut % 60 Sea water Glensol 40 20 0 0 0.2 0.4 0.6 0.8 1 Water saturation Figure 3.7. Fractional flow behavior under Glensol flood.▲∆ & ●○ = data for 1st and 2nd stages of EOR with Glensol in freshwater. = 1st and 2nd stages of EOR with Glensol in saltwater. From figure 3.7 it is clear that flooding with GEOR 1 improves the fractional flow regime; arrival of the GEOR 1 flood-front at the end of the beadpack is marked by a reduction in water-cut as an oil bank is mobilised and moved through the beadpack. This effect is most pronounced for the saltwater experiment. However 19
  21. 21. Evaluation of GEOR 1 for EOR late stage extended flooding with GEOR 1 in saltwater is characterised by an increasing water-cut, but the shape and gradient of the line on figure 3.7 does not suggest a change in wettability as was observed for the thermal method. Although the extended floods using GEOR 1 in freshwater do not water-out during the duration of the experiment, eventually this would occur. Flooding with a low concentration of GEOR 1 may increase recovery via a range of mechanisms: 1) An increase in heavy oil mobility caused by strong and rapid surfacting action; GEOR 1 has been shown (by Glensol) to act rapidly on asphalt associated with tar-sands and pipe-line precipitated asphaltenes where it rapidly penetrates through oil residues to reach the oil-surface interface. Results presented here suggest that the same effect occurs in a dynamic environment. This gives GEOR 1 not only access to residual oil, but access to heavy asphaltic oil in marginally tighter regions of the beadpack that would be difficult to mobilise using water alone. 2) The formation of water in oil microemulsions with reduced oil viscosity. Microemulsions have a much reduced viscosity and swell to form a continuous mobile oil phase. This process is most evident for the saltwater experiments and is expressed as a notable decrease in water-cut and an increase in recovery. 3) If GEOR 1 viscosifies water it may also increase overall recovery by stabilising the flood-front and being better able to mobilise oil. This would aid sweep efficiency and increase overall recovery. 20
  22. 22. Evaluation of GEOR 1 for EOR 3.3 Areal Sweep Efficiency Unswept regions after coldwater flood Unswept regions after coldwater flood 1 mm Comparison after Glensol flood Comparison after extended coldwater Figure 3.8. Images showing increased areal sweep efficiency of Glensol flood at small scale. Top images show beadpacks after primary waterflood. Bottom images show photographs of pack after 1st EOR stage. Coloured overlays show outlines of unswept regions after primary flooding. After the coldwater flood areas outlined in blue still contain black oil. After Glensol flood the areas outlined in blue are better swept. Field-scale areal sweep efficiency is a function of geological heterogeneity and cannot be assessed at the scale of the experiments reported here. However regions of bypassed oil did develop during most experiments. This is evident in most experiments after the initial waterflood stage (see Table 1.1 and 1.2). GEOR 1-floods are notably effective at accessing oil within these regions. This can be further illustrated by overlaying the outlines of regions of bypassed oil (shown as blue lines) onto to the bead pack after the application of the EOR method (figure 3.8). After an extended waterflood many dark patches of oil remain within blue lines as cold water can not easily shift the heavy oil in these regions. This is not the case after flooding with GEOR 1 where the areas enclosed by blue lines, although large, contain few patches of dark oil. GEOR 1 has somehow managed to access regions initially inaccessible to the water 21
  23. 23. Evaluation of GEOR 1 for EOR phase. A thermal method would be expected to mobilise heavy oil in such regions by the conduction of heat, which does not depend on mass transfer to lower viscosity. A chemical EOR method requires physical contact with the by- passed or residual oil to mobilise it. The mobilisation of heavy oil in these regions by GEOR 1 is therefore notable and attests to the rapid and deep surfacting action of GEOR 1. 22
  24. 24. Evaluation of GEOR 1 for EOR 4.0 Conclusion The presence of very low concentrations of GEOR 1 in injected water significantly enhances the recovery of heavy oil during waterflood. Heavy oil production is brought forward relative to coldwater flooding with fresh and saline water with high recoveries obtained more rapidly when flooding with GEOR 1 than with hotwater or coldwater benchmarks. The positive affect of GEOR 1 in both fresh and saltwater highlights its robustness as an additive. To the best of our knowledge GEOR 1 has unique properties as a chemical additive as it is efficient and effective in salt- and freshwater when used at low concentrations sets it apart from previous chemical methods of enhanced oil recovery. GEOR 1 is cost effective and not designed to be recovered for reinjection thus mitigating an important element of economic risk in EOR projects. For example, where loss of surfactant by adsorption onto reservoir surfaces is encountered during surfactant flooding this could feasibly be mitigated by increasing the concentration of GEOR 1 in the injected water as the GEOR 1 itself is not an unreasonable cost increment or environmentally sensitive in an EOR project. Because the GEOR 1 additive can be used in a variety of reservoir formation water chemistries it should be possible to simplify programes of additive treatment in field applications. This potentially reduces the costs and risks typical of previous chemical methods of enhanced oil recovery which required extensive design and compatibility studies. The experimental results far exceeded our expectations for GEOR 1 and more importantly demonstrated that the additive out-performs cold- and hot-water floods in fresh- and salt-water. Our bead-pack experiments are a simplification of natural reservoir conditions however, they provide an important insight into the utility of GEOR 1, which encourages us to recommend designing an immediate field trial. 23

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