The Use of Tracers to Validate CO 2 Migration Paths and Rates Detection and Monitoring of Migration and Leakage

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1 The Use of Tracers to Validate CO 2 Migration Paths and Rates Detection and Monitoring of Migration and Leakage Linda Stalker Science Director for the National Geosequestration Laboratory (NGL) Matt Myers Research Scientist August 2014 ENERGY FLAGSHIP/NATIONAL GEOSEQUESTRATION LABORATORY

2 Outline Tracers in CCS Where have they been used before? Choice where to start! Injection how much? Sample acquisition options Analysis of tracer samples (not as straight forward as you might imagine.) Interpretation partitioning behaviour Modelling mind your language! Conclusions Residually trapped CO 2 Residually trapped CO 2 Residually trapped CO 2 Rock grains Water Flow of CO 2 Rock grains Water Flow of CO 2 Rock grains Water Flow of CO 2

3 Tracers Workflow Laboratory Experiments Suitability of tracer for a particular application / environment and tracer behaviour in the relevant system being studied Field Trials Tracer interaction with system being studied A variety of methods (e.g. water sampling) are used to determine what has happened to the tracer. Simulations and Modelling - Interpretation of tracer data This requires accurate information from both laboratory experiments and field trials All of these are required to develop an accurate understanding of chemical tracer transport within a system.

4 Tracers where have they been used before? Oil and gas industry EOR S or determination Water floods Compartmentalisation Groundwater research Flow rates Water sources Contamination Rainfall recharge rates Atmospheric Medical Livestock emissions Imaging CCS cases CO2CRC Otway Project Stage 1 CO2CRC Otway Project Stage 2B Frio Brine Projects BP In Salah K12-B West Pearl Queen ZERT/Ginninderra Shallow Release

5 Choice of Tracers Considerations Physical/chemical behaviour Background concentration OHSE Reactivity Geology Cost/Amount required Availability Impact on different monitoring scenarios Analysis cost, turnaround, local availability Artificial tracers Otway Stage 1 CD 4 / SF 6 / Kr / R-134a Otway Stage 2 PDGA / Triacetin / Tripropionin Xe/Kr Frio Brine Perfluorocarbons (PFCs) Noble gases Other projects Perfluorocarbons (PFCs) Natural tracers Existing organic/inorganic species Often persistent in the environment

6 Injection Interwell or single well tests In the case of Otway.. 300kg (or approximately 50,000L) SF 6, 20,000 L Kr and 2,000L CD 4 were added to the injection stream in April, These volume requirements were based on the addition of 100,000 tonnes of gas injected over a 24 month period, assuming a 30% residual methane gas saturation, transit distance of 300m from injector to monitoring well, a need to saturate a 15m radius around the injection borehole, reservoir porosity of 15% and downhole pressures of around 20.7 MPa (3000 psi). (Stalker et al EP) And then add a few zeros. U-tube 1

7 Injection Reservoir to surface Example: West Pearl Queen 20 tonnes of CO 2 mixed with 500 ml of PDCB Average leakage rate of CO 2 (CATS tubes buried in soil) = x 10-6 L over 54 days over entire area covered by network Estimated leak rate of % of injected CO 2 per year Wells et al, 2007 App. Geochem. Typically a detectable rate of % per year is necessary. 1 million tonnes of CO 2 25,000 L of PFC tracer if you tag all of the CO 2

8 Sample Acquisition CO2CRC CRC-2 Stage 2B equipment Deep formation samples Positive displacement samplers Vacuum samplers Flow-through samplers Pumps U-tubes Summarised in Wolff-Boenisch & Evans (2014) Wellhead suitable for nonvolatile liquids Soil gas and atmospheric sampling CATS tube for PFCs Freifeld et al. (2005)

9 Analysis of tracer samples In the field or in the lab, the method depends on The injected tracer some need specific methods e.g., GC-MS vs GC-ECD ; special columns; pre-treatments; derivatisation etc. Some of these can linger or have memory effects The background fluid ScCO 2 vs in formation water What you have available (not always the most efficient way to go) Timing trace amounts in a background medium may not linger!

10 Lab measurements of tracer behaviour Batch Reactor setup designed to pressures up to 300 bar, temperatures up to 120 C and salinities of up to 300,000 ppm. Hastelloy and Superduplex typically used for all wetted parts exposed to CO 2 and/or brine. Slim Tube experimental set up includes 12 m stainless steel ¼ tubing filled with a variety of sediments Oven for packed tubing Low flow and high flow syringe pump system to push through brines and CO 2 saturated brines Sample collection and analysis facilities to quantify breakthrough and/or tracer lost onto sediment surfaces or trapped residually.

11 Batch Results Tracer CO 2 CO 2 : CH 4 (80:20 mol/ mol. %) 59 C experiments K c/w conc. basis K c/w std. dev. K x c/w mol. frac. K c/w conc. basis K c/w std. dev. K x c/w mol. frac. Kr Xe SF CD R134a C experiments Kr Xe SF CD R134a

12 Partition coefficients interwell tests Tracer production profiles at the top of the monitoring well for CO 2 and tracer injection into an infinite-acting aquifer. Tracer production curves for air/water partition CO 2 /water partition coefficients Dashed line indicates breakthrough of injected gas at the observation point.

13 Laboratory Study of Reactive Ester Tracers High pressure/temperature laboratory studies to determine tracer CO 2 /water partition coefficients. Compound Partition coefficient based on mole fraction of solute in solvent, k i x Partition coefficient based on concentration at 15 MPa, k i Propylene glycol diacetate 54.5 ± ± 0.86 Propylene glycol 1.04 ± ± monoacetate 1 Propylene glycol 9.79 ± ± 0.36 monoacetate 2 Triacetin 27.7 ± ± 0.90 Diacetin ± ± Diacetin ± ± Monoacetin ± ±.044 Monoacetin ± ± Acetic acid ± ± Propionic acid 1.50 ± ± Glycerol a a Propylene glycol a a Selection of chemical tracers and simulation of tracer breakthrough curves

14 Concentration (arbitrary units) Partition coefficients single well test S or = 0.05 S or = S or = S or = time (hours)

15 Conclusions The use of chemical tracers in CCS is complementary to geophysical measurements (e.g. seismic, INSAR). Test sensitivity can be scaled by the amount of tracer added. A variety of chemical tracers are used for interwell and/or single well chemical tracer tests. Perfluorocarbons dominate CCS space particularly for applications related to measuring leak rates. There is potential for development of new chemical tracers. Tracers in combination with other measurements (e.g., CO 2 content) can give long term information on the behaviour of the storage interval. Use of chemical tracers in large scale tests could actually contribute to higher background levels downward spiral.. (Watson and Sullivan, Environ. Sci. Technol., 2012, 46 (3), pp )

16 Thank you NGL/Energy Flagship Linda Stalker Science Director for the National Geosequestration Laboratory (NGL) t E linda.stalker@csiro.au w Energy Flagship Matt Myers Research Scientist t E matt.myers@csiro.au w ENERGY FLAGSHIP