AN OVERVIEW OF HEAVY OIL RECOVERY STUDIES

Transcription

1 1 AN OVERVIEW OF HEAVY OIL RECOVERY STUDIES AT THE CENTRE FOR ENHANCED OIL RECOVERY AND CO2 SOLUTIONS OF HERIOT-WATT UNIVERSITY Prof. Mehran Sohrabi 28 August 2012 IEAEOR 33 rd Annual Symposium, Regina, Saskatchewan, Canada Contact: +44(0) Institute of Petroleum Engineering, Heriot-Watt University Edinburgh, UK

2 Outline 2 Introduction & Objectives Experimental Facilities Visualization Experiments Coreflood Experiments Conclusions

3 Heavy Oil Recovery 3 Very low primary production (5% to 10%) and poor waterflood performance. Thermal methods are applied in the field but there are limitations: - thin and deeper reservoirs - energy intensive - environmental issues e.g. carbon footprint Non-thermal recovery methods provide a solution for reservoirs in which thermal methods are impractical or uneconomical also offer advantages on capital cost, energy consumption, environmental pollution etc.

4 Objective 4 The objective of the Non-Thermal Enhanced Oil Recovery JIP at Heriot-Watt is to investigate potential of improving heavy oil recovery by: Water/CO2 combinations (focus of this presentation) Chemical Injection, and Mobility control techniques.

5 Mechanisms of Oil Recovery by CO2 Injection 5 Interactions of CO2 and crude oil are different in heavy oil compared to conventional oil Light Oil Systems Heavy Oil Systems Klins, 1984

6 Viscosity Ratio (% viscosity of oil/co2 mixture to original oil viscosity) CO2 Dissolution and Viscosity Reduction 6 While miscibility would be absent, large drops in heavy oil viscosity takes place upon mixing with CO2. 100% 90% Crude "J" 80% Crude "C" 70% 60% 50% 40% 30% 20% 10% 0% 0% 20% 40% 60% 80% 100% CO2 content, saturation frac.

7 7 Our research approach: Investigate pore-scale physics by performing visualization experiments Quantify level of additional oil recovery by each method by core flood experiments under reservoir conditions. Performed simulation and modelling at core and field scales.

8 Outline 8 Introduction & Objectives Experimental Facilities Visualization Experiments Coreflood Experiments Conclusions

9 Work Reported in Thesis 9 Eight heavy crude oil samples were provided by sponsor companies from reservoirs around the world. The viscosity range was from 5 to cp at their test conditions. The focus of this presentation is on the following two heavy oils. Crude APIº Viscosity (cp) Pressure (psig) Temperature (ºC) C J Experimental Work Fluid Characterization: Viscosity, composition, Wettability, IFT, Acid number, etc Flow Visualization Experiments: Using the transparent micromodels to investigate the displacement mechanisms at the pore scale, Displacement Experiments: Using Sandpack and consolidated cores to up-scale and quantify the observations in the micromodel.

10 Flow Visualization Rig 10 High-pressure micromodels allow detailed investigation of pore-scale mechanisms under reservoir conditions.

11 11 Coreflood Rig

12 Outline 12 Introduction Experimental Facilities Visualization Experiments Coreflood Experiments Conclusions

13 Low Pressure (gaseous) Application of CO2 (Crude C) Initial Waterflood Flood poor oil recovery CO2 Flood at CO2 Breakthrough CO2 Flood after 2 days note change of colour of oil due to dilution with CO2 Water injection after CO2 flood resulted in significant additional oil recovery

14 High Pressure (Super Critical) Application of CO2 (crude J) Initial Oil saturation Initial Water Flood CO2 Flood at Breakthrough CO2 Flood after 1 day 2 nd Waterflood (post CO2 Flood)

15 Mobility Control by CO2-Foam (Crude C) Initial Oil Saturation Water Flood Surfactant Flood CO2-Foam, BT 1 hr CO2-Foam, 2 hrs CO2-Foam, 5 hrs CO2-Foam, 101 day hrs

16 Oil Recovery Comparison (Crude C) CO2 Flood after 2 days CO2 and Water injection (slugs) CO2-Foam injection 1 day

17 Outline 17 Introduction Experimental Facilities Visualization Experiments Coreflood Experiments Conclusions

18 Oil Recovery (%OOIP) Oil Recovery by Waterflood (Heavy Oil vs. Light Oil) Heavy Crude oil J cp Light Oil - 1 cp Water BT Inj Brine (PV)

19 Oil Recovery (%OOIP) Heavy Oil Recovery by CO2 Injection (Tertiary Vs Secondary) Secondary CO2 Flood Tertiary CO2 Flood Secondary CO2 Flood CO2 BT 10 Secondary Waterflood Tertiary CO2 Flood Inj Fluids (PV) Crude J 617 cp (medium heavy oil)

20 Oil Recovery (%OOIP) Mobility Control by CO2-Foam (CO2 inj Vs CO2Foam) Tertiary CO2 Flood CO2-Foam Flood Waterflood CO2/CO2-Foam Flood Inj Fluids (PV) Crude C 8670 cp (extra heavy oil)

21 CO2 Storage (PV) Average Gas Saturation CO2 storage in light vs. heavy oil Reservoirs 21 While in conventional oil reservoirs the amount of CO2 that can be stored in water flooded reservoirs (tertiary) is much lower than secondary. In heavy oil systems, CO2 storage capacity is almost the same for secondary and tertiary CO2 injection. Heavy Oil (Crude J ) 617 cp Light Oil µ <1 cp Secondary Gas Injection Tertiary Gas Injection Secondary CO2 Flood Tertiary CO2 Flood Phase, Gas Injection 3 Phase, 1st Gas Injection Inj Fluids (PV) Gas Injected (Core PV) Mobeen Fatemi and Mehran Sohrabi, Water Alternating Gas Injection JIP, Steering meeting Oct. 2011

22 Outline 22 Introduction Experimental Facilities Visualization Experiments Coreflood Experiments Conclusions

23 Conclusions 23 The results of this study show significant potential for enhanced oil recovery and CO2 storage in heavy oil reservoirs. The coreflood results show that the performance of CO2 is, to a large extent, dependent on reservoir conditions, the state of CO2 under reservoir conditions, and physical properties of the heavy crude oil.

24 Conclusions 24 Comparison of recovery data during secondary and tertiary injection of CO2 reveals that secondary CO2 injection provides much better recovery efficiency at early injection times. While CO2 storage capacity in light oil systems is a strong function of injection mode (pre- or postwaterflood), heavy oil systems show much less sensitivity to CO2 injection strategy.

25 Conclusions 25 The results of micromodel and coreflood experiments revealed that when the CO2 flood process is boosted by a appopriate mobility control technique (e.g. insitu formation of foam), heavy oil displacement process takes place in a much shorter time period and more efficiently.

26 Acknowledgment 26 This work was carried out as part of the ongoing Enhanced Heavy Oil Recovery joint industry project (JIP) at the Institute of Petroleum Engineering of Heriot-Watt University and was equally supported by: Total Exploration and Production UK, ConocoPhillips, Petrobras, PEMEX, and PTT Ltd. which is gratefully acknowledged.