1. Dr. Mohammed M. Amro Petroleum Engineering Dept. King Saud University Effect of Scale and Corrosion Inhibitors on Well Productivity in Reservoirs Containing Asphaltenes 16.05.2005

2. Outline Statement of Problem Statement of Problem General Aspects General Aspects Effect and Preventation of Asphaltenes Precipitation Effect and Preventation of Asphaltenes Precipitation Experimental Work Experimental Work  Material Used  Results and Discussion Summery Summery

3. Statement of Problem During oil production from several wells in Arabian Gulf area, significant productivity decline was noticed. During oil production from several wells in Arabian Gulf area, significant productivity decline was noticed. One of the reasons behind this might be asphaltene precipitation. Production data of the particular wells were collected and analyzed. One of the reasons behind this might be asphaltene precipitation. Production data of the particular wells were collected and analyzed. Many of these wells were injected with scale and corrosion inhibitors in downhole and surface equipment. Many of these wells were injected with scale and corrosion inhibitors in downhole and surface equipment. It was decided to investigate the potential of formation damage due to asphaltene in presence of scale and corrosion inhibitors as field chemicals. It was decided to investigate the potential of formation damage due to asphaltene in presence of scale and corrosion inhibitors as field chemicals.

4. General Aspects Controlling asphaltenes problems requires one to understand the conditions lead to deposition. Controlling asphaltenes problems requires one to understand the conditions lead to deposition. Reviewing production decline and well history can identify damaged wells. Focus on treatment history (acid, other solvents, …) and subsequent response. Reviewing production decline and well history can identify damaged wells. Focus on treatment history (acid, other solvents, …) and subsequent response. Laboratory testing helps design effective chemical treatment Laboratory testing helps design effective chemical treatment

5. Effect and Preventation of Asphaltenes Precipitation  Asphaltenes Problems in the reservoirs can occur during primary depletion in highly undersaturated Reservoirs, IOR-CO2 or chemical treatment and cause Permeability reduction Wettability alteration (Oil wetting) Reduce oil production

6. Prevention Predictive method Predictive method  PVT, Compatibility tests between different fluids Reservoir pressure above Pb Reservoir pressure above Pb Mechanical (scrapping) Mechanical (scrapping) Chemical treatment Chemical treatment  Solvents (Aromatics)  Dispersant and/or surfactant  Light oil Asphaltene deposition is the consequence of instability of oil

7. Experimental Part Material Used Crude oil (11 cp, API 31.2°, 15% resin) Crude oil (11 cp, API 31.2°, 15% resin) Asphaltene sample as solid paritcles Asphaltene sample as solid paritcles Scale and Corrosion Inhibitors Scale and Corrosion Inhibitors (5 scale & 2 Corrosion inhibitors) Core Samples (Berea Sandstone) and Core Samples (Berea Sandstone) and Flooding Apparatus Flooding Apparatus

8. Experimental Part Methodology The asphaltenic oil was prepared by mixing a certain weight of solid asphaltene at different concentrations. The asphaltenic oil was prepared by mixing a certain weight of solid asphaltene at different concentrations. The max. concentration was determined by observing flocculation and precipitation of asphaltenes for a period of 5 days. It was found that the used crude oil could stabilize an asphaltene concentration up to 3%. The max. concentration was determined by observing flocculation and precipitation of asphaltenes for a period of 5 days. It was found that the used crude oil could stabilize an asphaltene concentration up to 3%. Surface and interfacial tensions and contact angle of the oil samples were measured in presence of brine as well as brine containing scale and corrosion inhibitors. Surface and interfacial tensions and contact angle of the oil samples were measured in presence of brine as well as brine containing scale and corrosion inhibitors.

9. Experimental Part- Flooding 1 st Using crude oil displaced by 5% brine (reference experiment). 2 nd Using crude oil displaced by 5% brine containing scale or corrosion inhibitors (Effect of inhibitors on the floodin in presence of crude oil without asphaltenes). 3 rd Using asphaltenic oil at 1% asphaltenes displaced by 5% brine. (represent the flooding with asphaltenic oil as a reference). 4 th Using asphaltenic oil at 1% asphaltenes displaced by 5% brine containing 200 ppm scale or corrosion inhibitors.

10. Experimental Part - Flooding Relative permeability curves were determined using unsteady state method, to evaluate the influence of the inhibitors on the multiphase flow through the porous media. Relative permeability curves were determined using unsteady state method, to evaluate the influence of the inhibitors on the multiphase flow through the porous media. Driving fluid at constant flow rate displaces the in-situ fluid. Driving fluid at constant flow rate displaces the in-situ fluid. Johnson-Bossler-Naumann (JBN) was used to calculate the Kr. Johnson-Bossler-Naumann (JBN) was used to calculate the Kr.

11. Results of Flooding Experiments The presence of scale inhibitors does not affect the fluid flow behavior in porous media (confirmed by contact angle and IFT). The presence of scale inhibitors does not affect the fluid flow behavior in porous media (confirmed by contact angle and IFT). The presence of corrosion inhibitors showed significant change in Kr The presence of corrosion inhibitors showed significant change in Kr The experiments conducted in series 1 and 2 were analyzed and compared The experiments conducted in series 1 and 2 were analyzed and compared Series 1: Crude oil displaced by brine Series 2: crude oil displaced by brine containing corrosion inhibitor

12. Results of Flooding Experiments The experiments conducted in series 1 and 3 were compared. The experiments conducted in series 1 and 3 were compared. It shows a reduction in oil relative permeability in presence of asphaltenes. This is probably due to higher viscosity (14 cp) It shows a reduction in oil relative permeability in presence of asphaltenes. This is probably due to higher viscosity (14 cp)

13. Results of Flooding Experiments

14. Photograph of core#3 & 4

15. Core #3Core #4 Core #3Core #4

16. Summary There is no significant change in wettability in presence of scale inhibitors There is no significant change in wettability in presence of scale inhibitors The presence of corrosion inhibitor solution resulted in alteration of wettability to strongly oil wet. The presence of corrosion inhibitor solution resulted in alteration of wettability to strongly oil wet. A mixture of corrosion and scale inhibitors will not affect the water wettability of quartz plate A mixture of corrosion and scale inhibitors will not affect the water wettability of quartz plate It was found that the combination of asphaltenic oil and corrosion inhibitor leads to asphaltenes deposition (formation damage) It was found that the combination of asphaltenic oil and corrosion inhibitor leads to asphaltenes deposition (formation damage)

17. Summary A successful chemical treatment in the field is based on laboratory investigations to verify the compatibility of any field chemicals with the well productivity prior application A successful chemical treatment in the field is based on laboratory investigations to verify the compatibility of any field chemicals with the well productivity prior application The overall results are important for oil reservoir containing asphaltenes The overall results are important for oil reservoir containing asphaltenes

18. Thank you

19. Diagnosis Information Analysis Plugged Wells Deposit Inorganic Deposit Scale Sand Organic Deposit ParaffinsAsphaltenes Non Plugged Wells Prediction: PVT Asphaltenes Solubility Characterization % Asphaltene (Each 2 Months) % Asphaltene Reduction

20. Fine Particles

21. Contact Angle Pre-Screening

22. Contact angle measurements in presence of crude oil (Water wet)

23. Contact angle measurements in presence of asphaltenic crude oil

24. Surface tension of asphaltenic oil

25. Interfacial tensions between asphaltenic oil and brine containing scale inhibitor

26. Surface and Interfacial Tension Corrosion Inhibitors Contact Angle of asphaltenic oil in presence of corrosion inhibitor 180° (Strongly oil wet) C-68C-62E Surface Tension 3737 Interfacial tension with Arabian light 6.81.2 1.80.2

27. Relative Permeability