CO2 Injection in Light Oil Fractured Reservoirs. (Experimental Study)

Transcription

1 CO2 Injection in Light Oil Fractured Reservoirs (Experimental Study) Farshid Torabi, Ph.D., P. Eng., University of Regina Koorosh Asghari, Adj. Prof., University of Regina F. Torabi, K.Asghari, University of Regina, Canada, IEA-EOR

2 Introduction Outline Objectives Core Specifications and Fluids Properties Experiments Experimental Set-up and Procedure Results and Discussion Effect of Connate Water Effect of Oil Viscosity/Composition Effect of Core Permeability Conclusion F. Torabi, K.Asghari, University of Regina, Canada, IEA-EOR

3 Introduction Fractured Reservoirs are poor candidate for Immiscible gas injection Miscible gas injection and Huff and Puff Process in particular has not been tested in fractured reservoirs under miscible/immiscible CO 2 injection Reduction of capillary pressure, IFT and Oil viscosity combined with induced solution gas drive mechanisms at miscible condition could improve oil recovery F. Torabi, K.Asghari, University of Regina, Canada, IEA-EOR

4 Fractured Reservoirs Gravity drainage is the main mechanism of oil flow Low matrix permeability High fractured permeability High production rate at early stage Rapid decline of pressure and production rate F. Torabi, K.Asghari, University of Regina, Canada, IEA-EOR

5 Naturally Fractured Reservoirs F. Torabi, K.Asghari, University of Regina, Canada, IEA-EOR

6 Objectives Examine the effect of CO 2 on gravity drainage process in fractured reservoirs To investigate the effect of connate water saturation, matrix permeability, and oil viscosity on gravity drainage in presence of CO 2 Evaluate the potential of fractured reservoirs for CO 2 storage F. Torabi, K.Asghari, University of Regina, Canada, IEA-EOR

7 Types of Experiments Conducted A lab scale model is built and several sets of experiments simulating CO 2 gravity drainage are conducted. Both miscible and immiscible conditions between CO 2 and oil are investigated. Effect of the following parameters were investigated operating pressure connate water saturation matrix permeability oil viscosity F. Torabi, K.Asghari, University of Regina, Canada, IEA-EOR

8 Core Specifications D=5.08cm D=5.08cm H=30.48cm Core-1 L=1 ft H=30.48cm Core-2 Core/ Cylinder Permeability (md) Porosity (%) Height (cm/ft) Diameter (cm/in) /1 5.08/ /1 5.08/2 F. Torabi, K.Asghari, University of Regina, Canada, IEA-EOR

9 Fluid Properties Fluids Viscosity, cp Density, gr/cc at 20 o C, 1 atm nc Diluted Instow Oil F. Torabi, K.Asghari, University of Regina, Canada, IEA-EOR

10 Experimental Conditions Temperature, o C 35 Pressure, kpa Pressure, kpa Step~1729 kpa, nc 10 /CO 2 Step~3458, kpa, Instow Oil/CO 2 F. Torabi, K.Asghari, University of Regina, Canada, IEA-EOR

11 PVT Studies (Experiments, Winprop TM, Correlation) F. Torabi, K.Asghari, University of Regina, Canada, IEA-EOR

12 Minimum Miscibility Determination Minimum Miscibility Pressure METHOD (MMP), kpa nc 10 /CO 2 Crude/CO 2 Correlation WINPROP Experiment Rising Bubble F. Torabi, K.Asghari, University of Regina, Canada, IEA-EOR

13 Visualization of the Miscibility CO 2 2 CO 2 +nc 10 Crude oil oil ~7.5 MPa F. Torabi, K.Asghari, University of Regina, Canada, IEA-EOR

14 IFT (dyne/cm) University of Regina Minimum Miscibility Determination Through IFT Measurement MMP=~8050kPa Pre ssure (kpa) F. Torabi, K.Asghari, University of Regina, Canada, IEA-EOR

15 Liquid Viscosity (cp) University of Regina Viscosity of CO 2 /Crude System Temperature = 35 o C kpa kpa kpa CO 2 Mole Fraction F. Torabi, K.Asghari, University of Regina, Canada, IEA-EOR

16 Experiments F. Torabi, K.Asghari, University of Regina, Canada, IEA-EOR

17 Experimental Set-up Pressure regulator P CO 2 Fan Fracture Computer Heating Wrap Oil/gas Separator Core-holder CORE ISCO Pumps T Air Bath CO 2 High-Pressure Visual Cell F. Torabi, K.Asghari, University of Regina, Canada, IEA-EOR

18 Procedure of Experiments A core was saturated with oil (nc 10 and later Instow oil) Starting with 1 st pressure step (1729 kpa), CO 2 was introduced in the system including high-pressure collector sell Pumps were allowed to keep the pressure constant After 24 hrs, a valve provided between the core holder and HP cell was closed HP cell was depressurized and produced fluids were collected HP cell was then re-pressurized using CO 2 to the same pressure as the main system F. Torabi, K.Asghari, University of Regina, Canada, IEA-EOR

19 Procedure of Experiments The valve between HP cell and core holder was opened and connection was resumed Experiments were conducted until no more oil was produced This concluded gravity drainage experiment at One pressure step The same series of experiments were repeated in presence of connate water saturation Effect of core permeability was studied using a high permeability core Later, experiments were conducted using Instow oil in presence of connate water saturation (viscosity effect) F. Torabi, K.Asghari, University of Regina, Canada, IEA-EOR

20 Results and Discussions F. Torabi, K.Asghari, University of Regina, Canada, IEA-EOR

21 Recovery Factor, % University of Regina Summary of Results P=1729kPa P=3457 kpa P=5186 kpa P=6914 kpa P=8643 kpa P=10372 kpa Time(Days) F. Torabi, K.Asghari, University of Regina, Canada, IEA-EOR

22 Recovery Factor, % University of Regina Effect of Permeability on Ultimate Oil Recovery Low Perm (100md) High Perm (1000md) Pressure, kpa (Psi) F. Torabi, K.Asghari, University of Regina, Canada, IEA-EOR

23 Recovery Factor, % University of Regina Effect of Connate Water On Ultimate Oil Recovery Core saturated 100% with nc 10 Core saturated with crude in presence of Water Pressure (kpa) F. Torabi, K.Asghari, University of Regina, Canada, IEA-EOR

24 Recovery Factor, % University of Regina Effect of Type of Oil on Ultimate Oil Recovery nc10+water Crude+Water Pressure, kpa (Psi) F. Torabi, K.Asghari, University of Regina, Canada, IEA-EOR

25 Asphaltene Precipitation Asphaltene (b) F. Torabi, K.Asghari, University of Regina, Canada, IEA-EOR

26 CONCLUSION Miscible CO 2 injection in fractured reservoirs can improve gravity drainage, significantly. Results o this study showed a recovery factor of up to 18% below MMP, and 70% when MMP achieved. Connate water saturation seems to have no or minor effect on the RF performance by CO2 injection (at the capacity of this experiment) Suggested operating pressure is MMP but not far above or below it. CO 2 may become denser than oil at pressures far above MMP, reducing RF. F. Torabi, K.Asghari, University of Regina, Canada, IEA-EOR

27 Future Works Multi-fracture matrix model Multi-slab-fracture model is recommended Large-scale model study F. Torabi, K.Asghari, University of Regina, Canada, IEA-EOR

28 Acknowledgement The financial support provided for this research was provided by the Petroleum Technology Research Center (PTRC), Regina, and the Faculty of Graduate Studies and Research at the University of Regina. F. Torabi, K.Asghari, University of Regina, Canada, IEA-EOR

29 Thank You For Your Attention F. Torabi, K.Asghari, University of Regina, Canada, IEA-EOR