New Important Insight into CO 2 EOR in Different Types of Chalk

Transcription

1 New Important Insight into CO 2 EOR in Different Types of Chalk Erling H. Stenby Center for Energy Resources Engineering - CERE Technical Universiy of Denmark, DTU

2 Co-authors: M. Monzurul Alam, Ben Niu, Ida L. Fabricius, Wei Yan, Center for Energy Resources Engineering, DTU Helle F. Christensen, Frederik P. Ditlevsen, Morten L. Hjuler, Danish Geotechnical Institute, GEO Dan Olsen, Geological Survey of Denmark and Greenland

3 EOR through CO 2 Utilization Question to be answered: Is there a potential for CO 2 EOR in Denmark using CO 2 from Danish sources? DONG Energy Power Generation, DONG Energy E&P, CERE DTU, GEO, GEUS Funding: DONG Energy, HTF, DTU, GEO and GEUS Duration: 1 January June 2010

4 What did we investigate? How does CO 2 influence the properties of chalk? How does CO 2 influence the properties of a specific Danish reservoir oil? How well does CO 2 displace residual oil after waterflooding in different types of chalk? Core material, flluids and conditions come from the South Arne field

5 CO 2 EOR in Chalk o WP 1: Fluid-Rock Interactions 1.1: Sample Characterization (DTU) 1.2: Rock Mechanics (GEO) o WP 2: Phase Equilibria of Fluids (DTU) 2.1: Brine/CO 2 Equilibria 2.2: Effect of CO 2 in Water Flooded Reservoirs o WP 3: Multi-Phase Flow 3.1: Flooding Experiments (GEUS) 3.2: CT-scanning (DTU)

6 Objective of WP 1: Rock Fluid Interactions To quantify the effect of CO 2 -flooding of chalk on: Borehole stability (Shear strength properties) Compaction and subsidence (Pore collapse strength) Stiffness parameters Deliverables are data for: Reservoir modeling (compaction drive) Numerical modeling of borehole stability Petrophysical interpretation

7 Wormholes Problem Wormholes have compromised test results in previous studies Problem solution Estimate highest allowable flooding rate from Da and Pe and staying below Result Efforts successful no wormholes detected in this test series 37 mm Wormholes on chalk end surface!

8 Petrography: Tor Formation Porosity: 26% Permeability: 0.8 md BET: 1.7 m 2 /g Ca-carbonate: 98.6% calcite quartz smectite dolomite

9 Petrography: Ekofisk Formation Porosity: 32% Permeability: 0.6 md BET: 3.5 m 2 /g Ca-carbonate: 88.3% calcite quartz kaolinite

10 The Hoek cell for triaxial testing s 1 s 3 s

11 The p -q plot Shear strength Borehole stability Stress path Pore collapse Reservoir compaction

12 Tor Formation: Shear Strength and Pore collapse Flooding with supercritical CO 2 has no significant effect on shear strength and compaction properties of 30% porosity chalk from South Arne reference CO 2 flooded

13 Ekofisk Formation: Shear strength and Pore collapse Flooding with supercritical CO 2 has no significant effect on shear strength and compaction properties of 30% porosity chalk from South Arne CO 2 flooded reference

14 Normalised Amplitude Normalised Amplitude Results: Nuclear Magnetic Resonance (NMR) Flooding with supercritical CO 2 has no significant effect on wettability as indicated by NMR T2 relaxation time of chalk from South Arne 5 4 Tor Formation 5 4 Ekofisk Formation Time(ms) Time(ms) S w Brine saturated SCO2 w injected at brine saturated condition CO2 injected CO 2 at injected irriducible water saturated condition CO2 injected at residual oil saturated condition S wir S or

15 Biot's coefficient Results: Biot s coefficient Flooding with supercritical CO 2 probably decreases stiffness of Tor Formation chalk from South Arne After CO 2 injection 0.75 Before CO 2 injection Porosity

16 Conclusions Shear strength parameters: No significant effect. Pore collapse strength: No significant effect. Stiffness parameters: Probably decreasing in Tor Formation. Porosity: Probably increasing. Permeability: No significant effect.

17 WP 2: Phase Equilibria of Fluids Fundamental to CO 2 EOR processes Complex phase equilibrium when CO 2 is present Uniqueness of reservoir fluid should be addressed Modeling and simulation WP 2.1 Phase Equilibrium Measurements in Mixtures of Brine, Oil and CO 2 WP 2.2 Modelling and Simulating the Compositional Effects during CO 2 Injection into a Waterflooded Oil Reservoir

18 Saturation pressure (bar) Swelling factor CCE and CO 2 swelling P bubble increases with T: bar at 45, 80 and o C. Swelling test results LLE C 80 C C 80 C Single phase % 20.00% 40.00% 60.00% 80.00% % CO 2 mole percent (%) % 20.00% 40.00% 60.00% 80.00% % CO 2 mole percent (%) Liquid-liquid like equilibrium even P> P sat at high CO 2 mol% (>50 %) Adding 0.5 g CO 2 to 1 g oil (47 mol%) swells the oil by 35 vol%.

19 Viscosity (cp) Viscosity results Viscosity changes from to cp for CO 2 from 0 to 50 mol% (115.6 o C and 450 bar) C 80 C Two phases detected for CO 2 >60%, light phase viscosity plotted % 10.00% 20.00% 30.00% 40.00% 50.00% 60.00% 70.00% 80.00% 90.00% % CO2 mole percent (%) Both P sat and viscosity measurements indicate LLE like equilibrium at high CO 2 concentrations even at very high P.

20 WP 3: Multi-Phase Flow Reservoir conditions core flooding with miscible CO 2 using reservoir oil and reservoir cores Two different laboratories: CERE DTU and GEUS Core material selected and prepared at GEUS Same reservoir fluid prepared at CERE DTU CERE DTU: Single cores, CT scanning, horizontal GEUS: Stacked cores, vertical Conceptual modelling and simulation

21 Overview of the Experimental Setup

22 Flooding Conditions : Tor & Ekofisk 115 o C and 385 bar Tor Flooding rate, water-flooding Flooding rate, CO 2 -flooding Ekofisk Flooding rate, water-flooding Flooding rate, CO 2 -flooding 2 cc/h 4 cc/h 3 cc/h 3.6 cc/h

23 Tor: Water flooding Breakthrough

24 Tor: Gas flooding

25 Tor: Gas flooding

26 Ekofisk: Water flooding

27 Ekofisk: Gas flooding

28 Ekofisk: Gas flooding

29 Major Flooding Results Formation Tor Ekofisk Porosity 26 % 33 % Gas perm 1.1 md 0.73 md So, start of waterflood So, end waterflood So, end CO 2 -flood Sg, end CO 2 -flood Produced oil, waterflood 84 %OOIP 34 %OOIP Produced oil, CO 2 -flood 13 %OOIP 44 %OOIP Residual oil, end CO 2 flood 2.8 %OOIP 22 %OOIP

30 CO 2 EOR experiments on chalk at reservoir conditions GEUS Purpose of the work: To test the performance of CO 2 injection to produce additional oil from Syd Arne chalk after water-flooding. Perform two experiments with water-flooding followed by CO 2 -flooding on Syd Arne chalk.

31 Implications for CO 2 EOR on chalk extrapolated from work on two samples CO 2 -injection may produce significant amounts of additional oil from low-permeable chalk, even after a water-flooding operation. CO 2 -injection may result in effective oil displacement without early breakthrough of CO 2. Adverse effects from dissolution and compaction were not observed. CO 2 -injection may have a considerable potential for producing additional oil from Ekofisk chalk where waterflooding is inefficient.

32 EOR through CO 2 Utilization Question to be answered: Is there a potential for CO 2 EOR in Denmark using CO 2 from Danish sources? Answer: YES! and perhaps A comprehensive, coordinated and careful research project leading to new and solid conclusions

33 EOR through CO 2 Utilization o No negative effect on borehole stability and compaction o Some effect on stiffness of the Tor formation o No negative interaction with the South Arne oil o New generic data and modelling on CO 2 +brine o Increased recovery from the Tor formation o Dramatically increased recovery from the Ekofisk formation

34 Thank you!

35 Inlet end of samples after CO 2 -flooding All samples: Diameter = 37 mm Inlet end FS-1 before CO 2 -flooding Inlet end FS-1 after CO 2 -flooding Inlet end of sample FS-1 No dissolution features Inlet end FS-2 after CO 2 -flooding Inlet end sample OCD1 after flooding with CO 2 -enriched water