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

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

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

Pilot Design Producers CO2 Injectors Observation wells Water Injectors N

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

Spraberry Reservoir : Looks Complicated??

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

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

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

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

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

1u Frequency Distributions in Well # Neutron Porosity Distribution Relative frequency Cumulative frequency Jan rel freqMar rel freqjan cum freqmar cum freq 1 2

5u Frequency Distributions in Well #49

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

Production Outlook -Cumulative CO 2 Injection

Are we still getting enough oil in the tank??

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