1. Monitoring the Movement of CO 2 at the Upper Spraberry Reservoir Using Well Logs Gokul Lakshman Texas A&M University Pioneer Natural Resources

2. Outline  Pilot Information  Location  Pilot Design  Pilot Highlights  Upper Spraberry Makeup  CO 2 Flood Mechanism  Log Monitoring  Objectives and Tools Used  Looking Inside CNL tool  What the logs have to say?  Decision Analysis  Production Outlook  Conclusions and Future Scope

3. Glasscock Co Reagan CoUpton Co Midland Co Martin Co Canyon Reef Carriers CO 2 Supply Canyon Reef Carriers CO 2 Supply O’Daniel Shackelford Driver Merchant North Pembrook Benedum Pembrook Aldwell Sherrod Preston Midkiff Tippett Location

4. Pilot Design Producers CO2 Injectors Observation wells Water Injectors N

5. Pilot Goal To evaluate the technical and economical feasibility of using CO 2 as a tertiary recovery agent in the low permeability, fractured sandstone of the Spraberry Trend Pilot Objectives  Collection and Analysis of pilot performance data To understand vertical and horizontal heterogeneities To determine optimal usage of CO 2 Comparison of waterflood and CO 2 flood performance Work within the limitations of allocated budget

6. Spraberry Reservoir : Looks Complicated??

7. CO 2 Flood Mechanism CO 2 +OILOIL HEAVIER FRACTIONS 1550 PSI CO 2 1U 3U 4U 2U 5U 7045 7230 PAY ZONES CO 2 Key Operating Targets CO 2 Injection Rate= 91MSCF/D Average Reservoir Pressure= 2300PSI Target Water Injection Rate= 250BPD

8. Log Monitoring of CO 2 flood – A Forensic science Objectives  Monitoring the movement of CO 2 in the formation  Calculation of the saturation of fluids Logging Tools Used  Compensated Neutron Log  Array Induction Log

9. Enter Tool Physics CNL TOOL H+H+ Formation Gamma Rays Thermalized neutrons SSD SOURCE SS LS  LSD

10. Logging Runs Conducted Total HCPV to be injected : 22HCPV(128MMCF) How much has been injected until now:76MMSCF RUNSMONTHS 1Jan 2Feb 3Mar 4Apr 5Jun 6Aug 7Dec Feb 22nd Start of CO2 Injection

11. Successive Neutron porosity decrease observed-Jan to Dec Well 49 1u 2u 3u 4u 5u Gas entry What the logs have to say ?

12. 1u Frequency Distributions in Well #49 0.038-0.0500.050-0.0630.063-0.0750.075-0.0880.088-0.1000.100-0.1130.113-0.1250.125-0.1380.138-0.1500.150-0.1630.163-0.1750.175-0.1880.188-0.2000.200-0.2130.213-0.225 Neutron Porosity Distribution Relative frequency 0 10 20 30 40 50 60 70 80 90 100 Cumulative frequency Jan rel freqMar rel freqjan cum freqmar cum freq 1 2

13. 5u Frequency Distributions in Well #49

14. Decision Analysis--Lets be practical? Oil in tank-Is it significant?? Whether a nominal PV of CO2 has been injected ? Have Log So Responses Been Stabilized Cease CO 2 Injection

15. Production Outlook -Cumulative CO 2 Injection

16. Are we still getting enough oil in the tank??

17. Conclusions From neutron porosity logs there is indication of gas movement in all layers More Logging runs required to get a clear picture of CO 2 movement My present status of research Trying to calculate Sg using count rates Awaiting more data from field What I plan to achieve? Calculate Sg for all layers Compute extent of vertical displacement of CO 2 using log analysis Predict the horizontal movement of CO 2 using tracers and gas compositions at different wells