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Ikatan Ahli Teknik Perminyakan Indonesia

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Ikatan Ahli Teknik Perminyakan Indonesia Simposium Nasional IATMI 2009

Bandung, 2-5 Desember 2009

Makalah Profesional

IATMI 08 – 020

Laboratory Analysis of Combination of Vibration Stimulation and Surfactant Injectionat High Pressure and Temperature

By Revlin Rivelino Primadhani, ST Ir. Tutuka Ariadji, M.Sc, Ph.D

OGRINDO Abstract

Vibroseismic should be considered as one of IOR (Improved Oil Recovery) methods. For the last few years, many researches try to explain its mechanism using vibration stimulation laboratory work of core samples. To the author knowledge that we believe it could reduce surface tension physically, the related mechanism works on reducing capillary forces and surface tension between fluid and rock, increasing porosity, permeability, and oil mobility. In this study, we did laboratory experiment in combining vibroseismic and surfactant injection that has been known widely of reducing surface tension chemically, to pursue our hypothesis that is mechanism could work mutually to reduce the surface tension.

This experimental research is done at high pressure and temperature, which are 70oC and 100 psig. Based on the previous study, this study applied the optimum frequency of the vibration stimulation for the typical core samples that is 15 Hz. The results of this experiment show the best method to gain the best RF is the combination of vibration stimulation and surfactant injection simultaneously, i.e., 46.05%. Those results are also shown that there is characteristic change, where the lowest permeability and porosity decreasing generally happen in vibrated core samples.

Introduction

Limitations of the currently established Improved Oil Recovery methods to cope with oil field production decline cause in seeking on an alternative method. As an alternate method, Vibroseismic Technology applies the principles of vibration (seismic wave) to formations to improve oil field performance. The seismic wave that is transmitted from surface influences the electro potential of the oil in rocks, and then changes the contact angle as depicted in Figure 1. Positive 0.4 mV may change the contact angle to about 120 degree from 160 degree, and the oil may easily flow at 0.8 mV or -1.2 mV. Thus, the oil is released from the rock due to low contact angle or surface tension, formed coalescence and then it flows to the wells.

In Figure 2, the periodic displacements with the circular trajectories even with small amplitudes (less characteristic dimension of pores) can arouse vortex micro flows of liquid in pores. Such micro flows may develop rates increasing the displacement integrity of drops and films of the remaining oil adhesive to the walls of pores and being stable under steady-state watering regime. By the action of such hydrodynamic washing up of the pores’ walls under seismic action the remaining oil films and drops are detached from the walls and are involved into macro dynamical flow determined either by natural or by artificial hydrodynamic displacement of the reservoir. As a consequence the the oil production increases and water cut of the productive oil-wells decreases. Thus, those droplets


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forming a stream increase the oil mobility, as shown in Figure 3.

On the other hand, surfactant flooding is a well known of Enhanced Oil Recovery method by mechanism of lowering the surface tension chemically. Thus its target is the same parameter as the vibroseismic method that is surface tension reduction. Conceptually, combination this method with the vibroseismic method is a logically reasonable concept because the two methods reduce oil-rock surface tension both chemically and physically. An enclosed reference presents about this combination laboratory experiment results that give positive indications and encourage to doing more laboratory experiments for field core samples.

Surfactant has two surface active agents : the head and the tail. The head is the hydrophilic one, it bonds water to it. The tail is the hydrophobic one, it choose to bond with oil. The mechanism of surfactant can be seen in Figure 4. With this two surface agents, surfactant is capable to bond residual oil inside pores, and move together with the water to be produced to surface.

Moreover, prior to implementation, however, it needs conditions that suitable for this method to be conducted.

Screening criteria of the vibroseismic method have the following conditions4: 1. Reservoir rock type: consolidate 2. Permeability = Fair to Good 3. Oil gravity: 20-40 API 4. Viscosity less than 10 cp

Tutuka Ariadji5 (2005) has studied the effect

of vibration on fluid properties. The results study were the decreasing of residual oil saturation by up to 53.6%; the increasing of relative permeability as high as 73% on synthetic cores; the increasing of average porosity up to 36%. The residual oil saturation decreased as much as 66.1%; and decreased oil viscosity by 15% - 28% at various temperature from 70oC to 95oC. Beni6 shows that the optimum frequency using circular mode is 15 Hz that gives maximum incremental oil RF of 11.88% to the basecase on high permeability.

Antonius Himawan7 in his index ambient pressure and temperature research concludes that the most optimum surfactant can be used in this experiment is the 0.5% weight one among observed surfactant samples, both in surfactant injection experiment and also combination of it with vibration stimulation. The results can be seen in Figure 5 and Figure 6.

Research Method Methodology of this research is as the

following: 1. Literature Study Theories and laboratory results from previous researches are used to be compared and to support our laboratory results. 2. Laboratory Equipment Design Laboratory design is intended to design a new equipment that can be operated at high pressure and temperature, and it has better accuracy. 3. Laboratory Experiment Data Analysis Lab experiment and analysis conducted to prove the hypothesis of high pressure and temperature influences to the results. Research Limitation

There are some limitations in doing this research, those are: 1. Synthetic core, clean sand, homogeneous 2. Overburden Pressure 100 psig 3. Temperature 70oC 4. Q injection 0.3 cc/ min 5. One type of local surfactant 0.5% weight 6. Wave Type : Sircular (S-Wave) 7. Frequency : 15Hz Materials and Devices

There are the materials that are used in this experiment: 1. Quartz sand 2. Cement 3. Formation crude oil 4. Formation brine 5. N2 tube 6. He gas 7. Filter paper 8. Toluene 9. Surfactant

Devices that are used in this experiment: 1. UltraporeTM 300 Helium Pycnometer 2. Ultra PermeameterTM 400 3. Vacuum pump 4. Injection pump 5. Hassler Core Holder 6. Flask / measuring glass 7. Solvent extraction 8. The Vibroseismic apparatus 9. Oscilloscope 10. Vibration control unit 11. Digital scale 12. Pycnometer 13. Oven 14. Electric sieve apparatus


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Objective Technically, the objective of this laboratory

experiment work is to obtain quantitative influence of surfactant injection in combination with vibration stimulation at high pressure and temperature on recovery factor. Results and Analysis

In previous experiment, the vibroseismic apparatus could only work at atmospheric condition. Now, after being upgraded, the vibroseismic apparatus can work at high pressure and temperature. The new upgraded vibroseismic apparatus can be seen in Figure 20, while the details scheme for sircular wave in Figure 21. As seen in those figures, there are heater to heat the injected fluid, isolator jacket to isolate injection pipe with the environment, and temperature control, to maintain the experiment temperature applied for the experiment.

In these experiments, a vibration stimulation is applied simultaneously with injection of various surfactant concentrations. The oil used in this experiment is an oil with 0.8172 gr/cc of density 2.02 cp of viscosity, and 40 API. Brine used in this experiment has a 0.9964 gr/cc of density, and the surfactant goes in this experiment is 0.5% weight surfactant having 99% of active contents with 0.88 cp of viscosity, 0.971 gr/cc of density, and 14 API. Data for viscosity measurement is shown in Table 1.

There are 13 sample cores used with 33% of cement content. Characteristics of those sample cores and treatments applied to them are shown in Table 2. For the basecase, the experiments were conducted only with water (brine) injection. This injection works as a waterflooding simulation happened in real reservoir. Later, the results gained from these basecases were compared with other treatments. Those treatments are vibration stimulation; surfactant injection; and vibration and surfactant injection simultaneously. Results from these treatments can be seen in Table 4 and Table 5 consisting of incremental oil recoveries, rock characteristic changes, and the comparison graphs among them are shown in Figure 14 until Figure 19.

In Figure 14, the surfactant injection method gives higher RF over the basecase. So does what is shown in Figure 15. Here, there are two sample cores with equilibrium characteristic (k1=153.7 mD, k2=129.758mD) compared with the basecase (k=168 mD), and the result is the first core gives higher RF than the second core. This result appears none other because of its higher permeability.

As seen on Figure 16, where vibration stimulation and surfactant injection were ran simultaneously, it takes a while for this method to give higher RF over the basecase. There is a delay time that might due to the mechanisms occurred with the combination. Vibration stimulation itself takes some time to affect the oil productivity. The extra energy it gives takes some time to appear, and so does the movement of oil droplets and its stream forming. The injected surfactant also needs time to bond the oil with the water. The chemical reaction cannot happen in a short time because everything inside the cores, i.e., fluids and core wall, move caused by the vibration stimulation. But, once the reaction happen and the surfactant is able to bond the oil with the water, the oil productivity increases, and it increases faster because of vibration stimulation.

Meanwhile with the same method for different core samples, shown in Figure 17, it takes a while for oil to be produced. This might be happening because the core was not 100% fully saturated with oil, so the surfactant can be produced first. After all, this method is giving the best oil RF incremental among all, which is about 46.05%.

Figure 18 and Figure 19 show the performance of vibration stimulation experiment. The vibration stimulation gives not only higher oil RF in the end, but also faster recovery time. This phenomenon show us that vibroseismic can make the oil produced faster caused by its mechanism in changing the surface tension and later changing capillary forces. Results of this method always give ladder-shapped graphs. This can happen because vibroseismic also works by giving extra energy to push oil droplets to move and by making stream from oil droplets. No wonder there are some steps in this experiment where oil moves in droplets, and also in stream, and then followed by water production in its each steps.

The characteristic change of core samples are shown in Table 4. Because of limited facility, the solvent extraction cannot be ran perfectly. By having a solvent extraction the clean pores from any fluids (oil) are expected, but this step in this research were ran only for 24 hours where it should be 48 hours at least. Table 4 shows that there are few increasing core permeability and porosity, although most of them even decrease. But, the decreasing characteristics are higher in basecase core than the treaments ones. This phenomenon is not expected, however, considering the last fact that the basecase core has the higher decreasing characteristic, this can be understood. Water can make a swelling happen inside pores, that’s why all the basecases get higher decreasing characteristics. Surfacant


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injection takes the second phase, because it still contains water, but the vibroseismic method gives a good result among all. One of vibroseismic mechanism works by changing core characteristic. Meanwhile, Figure 13 and Figure 14 show the characteristic change in k/ki and φ/φi. The increasing permeability changes happen in cores injected with surfactant, but the others’ changes are not too bad either, their k/ki are still around 0.9. In this phenomenon, the vibrated cores don’t increase caused by their high cement content, which is 33%. Joko Mulyono8, the average clay content for vibroseismic application is around 20 to 25%, if it’s more than that, the clay inside pores will fall down after the stimulation and plug the pores.

In the Table 3, the results of each methods in different experiment condition are being compared. The first condition is when the experiment is in atmospheric temperature. The results for surfactant and combination of it with vibration stimulation were gained from Antonius Himawan7 experiment results, while the vibration one from Victor Sitompul’s9. The second condition is when the experiment ran in high temperature, which is 70oC. In the table below, the second condition gives higher oil RF, and the combination of vibration stimulation and surfactant injection are the highest. High temperature can make oil flow easier because of its decreasing viscosity. Meanwhile, the surfactant used in this experiment, Surfactant 13A*, can still work until 125oC. Conclusion 1. The best method to obtain optimum oil RF is

vibration stimulation and surfactant injection imultaneously with 46.05% of oil RF Incremental.

2. There are rock characteristic change happening, where the lowest permeability and porosity reduction generally happen in vibrated core samples.

3. Vibration stimulation and surfactant injection works better simultaneously where their mechanism work in physical and chemical way, although here’s delay time in reaching maximum oil RF.

4. Experiment with high temperature gives higher oil RF than the atmospheric one.

Acknowledgement

We wish to acknowledge OGRINDO for the financial support in doing the research.

References 1. Barabanov, V. L., Slides. 2. GEOSVIP, JSC: Feasibility Study Report-

Vibroseismic Stimulation of Oil Reservoirs to Enhance Oil Recovery at Selected Oil Fields in Indonesia, Moskow (2005), 7-9.

3. Ellingson, Olav, 2002. EOR by Electro-Acoustic Reservoir Stimulation: World Oil Magazine.

4. VSIT Technical Paper : Feasibility Study of Vibroseismic Technology in Malacca Strait Fields, 4-5.

5. Ariadji, Tutuka. (2005) : Effect Of Vibration On Rock And Fluid Properties: On Seeking The Vibroseismic Technology Mechanisms, SPE 93112.

6. Beni, Setiawan, (2007): Mathematical Modelling of Oil Production Performance under Vibration Stimulation, Thesis.

7. Anthonius Himawan (2007) : A Laboratory Study of Combination of Vibration and Surfactant Injection, Thesis.

8. Mulyono, Joko (2007) : Laboratory Test on The Permeability Change and Oil Recovery Factor of Clay Content under Stimulated Vibration, Final Assignment.

9. Sitompul, Victor (2008) : Effect of Vibration Wave Type in Low Permeability Sample Cores, Thesis.


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Table 1. Data for Viscosity Calculation

Measurement Result (sec) Trial Num Viscometer Constant Surfactant Oil

1 16.57 17.47 46.93

2 16.37 17.03 46.32

3 16.27 16.78 46.00

Average 16.40 17.09 46.42

Table 2. Samples Cores Used in Experiment

INITIAL

CORE Permeability (mD)

Porosity (%)

TREATMENT

X1 79.234 24.252 Basecase 1

SR 2.2 14.578 18.588 Basecase 2

RRP 1.4 24.420 24.927 Basecase 3

RV 2.13 82.525 14.282 Surf Injc.

RRP 1.8 12.630 24.682 Surf + Vibration

RRP 1.5 34.494 24.485 WF + Vibration

RV 2.10 168 15.493 Basecase 4

RV 2.15 218.962 16.336 Basecase 5

RV 2.11 315.018 16.854 Basecase 6

RV 2.3 153.700 16.326

RV 2.5 129.728 16.620 Surf Injc.

RV 2.14 216.220 17.354 Surf + Vibration

RV 2.1 310.751 16.656 WF + Vibration

Table 3. Oil RF Comparison for Each Method and Experiment Condition

Oil RF (%)

TREATMENT Atmospheric Temperature

High Temperature

Surfactant 6.25 33.64 40.13 18.75

Vibro 7.01 9.429 11.31 -

Vibro + Surf 12.5 14.23 46.05 -


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Table 4. Core Characteristic Change

INITIAL FINAL CHANGE

CORE Permeability (mD)

Porosity (%)

TREATMENT Permeability (mD)

Porosity (%) k/ki φ/φi

X1 79.234 24.252 Basecase 1 52.461 21.053

SR 2.2 14.578 18.588 Basecase 2 10.454 12.668

RRP 1.4 24.420 24.927 Basecase 3 12.297 14.469

- -

RV 2.13 82.525 14.282 Surf Injc. 68.820 12.110 1.312 0.575

RRP 1.8 12.630 24.682 Surf + Vibration 9.550 23.000 0.914 1.816

RRP 1.5 34.494 24.485 WF + Vibration 11.372 11.574 0.925 0.800

RV 2.10 168.000 15.493 Basecase 4 103.570 14.950

RV 2.15 218.962 16.336 Basecase 5 200.019 14.780

RV 2.11 315.018 16.854 Basecase 6 298.664 14.334

- -

RV 2.3 153.700 16.326 122.687 15.525 1.185 1.038

RV 2.5 129.728 16.620 Surf Injc.

98.234 13.979 0.948 0.935

RV 2.14 216.220 17.354 Surf + Vibration 188.253 16.100 0.941 1.089

RV 2.1 310.751 16.656 WF + Vibration 299.834 13.380 1.004 0.933

Table 5. Incremental of Oil Recovery after Treatment

CORE TREATMENT RF (%)

Δ RF (%)

X1 Basecase 1 27.93 SR 2.2 Basecase 2 22.52

RRP 1.4 Basecase 3 27.57 -

RV 2.13 Surf Injc. 61.57 33.64 RRP 1.8 Surf + Vibration 36.75 14.23 RRP 1.5 WF + Vibration 36.99 9.43 RV 2.10 Basecase 4 16.02 RV 2.15 Basecase 5 28.77 RV 2.11 Basecase 6 32.79

-

RV 2.3 56.16 40.14 RV 2.5

Surf Injc. 34.77 18.75

RV 2.14 Surf + Vibration 74.81 46.05 RV 2.1 WF + Vibration 44.10 11.31


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Figure 1. The Relation of Contact Angle and Amplitude1

Figure 2. The Movement of Oil while Vibrated2

Figure 3. The effect of Vibration on Oil Mobility3

Figure 4. The Mechanism of Surfactant

Figure 5. Oil Recovery Factor by injecting Various Concentration of Surfactant6

Figure 6. Oil Recovery Factors of 10 Hz Vibration Stimulation and Injection of Various Surfactant6


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Figure 11. Incremental of Oil Recovery (RF) after treatments

Figure 12. Permeability Change of Core Samples


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Figure 13. Porosity Change of Core Samples

Figure 14. Comparison Graph between Basecase 1 (k= 79.234 mD) and Surfactant Injection (k=82.525 mD)


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Figure 15. Comparison Graph between Basecase 4 (k=168 mD) and Surfactant Injection (k1=153.7 mD, k2=129.758 mD)

Figure 16. Comparison Graph between Basecase 2 (k= 79.234 mD) and Vibroseismic Stimulation and Surfactant Injection (k=82.525 mD)


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Figure 17. Comparison Graph between Basecase 5 (k= 218.962 mD) and Vibroseismic Stimulation and Surfactant Injection (k=216.22mD)

Figure 18. Comparison Graph between Basecase 3 (k= 24.42mD) and Vibroseismic Stimulation (k=34.494mD)


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Figure 19. Comparison Graph between Basecase 6 (k=315.018mD) and Vibroseismic Stimulation (k=310.751mD)

Figure 20. Vibroseismic Apparatus Working at High Pressure and Temperature


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Figure 21. Scheme of Sircular Wave in Vibroseismic Aparatus

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