Monitoring of CO2 storage in a depleted natural gas reservoir: Gas geochemistry from the CO2CRC Otway Project, Australia

The CO2CRC Otway Project in southwestern Victoria, Australia has injected over 17 months 65,445 tonnes of a mixed CO2-CH4 fluid into the water leg of a depleted natural gas reservoir at a depth of ∼2km. Pressurized sub-surface fluids were collected from the Naylor-1 observation well using a tri-level U-tube sampling system located near the crest of the fault-bounded anticlinal trap, 300m up-dip of the CRC-1 gas injection well. Relative to the pre-injection gas-water contact (GWC), only the shallowest U-tube initially accessed the residual methane gas cap. The pre-injection gas cap at Naylor-1 contains CO2 at 1.5mol% compared to 75.4mol% for the injected gas from the Buttress-1 supply well and its CO2 is depleted in 13C by 4.5‰ VPDB compared to the injected supercritical CO2. Additional assurance of the arrival of injected gas at the observation well is provided by the use of the added tracer compounds, CD4, Kr and SF6 in the injected gas stream. The initial breakthrough of the migrating dissolved CO2 front occurs between 100 and 121 days after CO2 injection began, as evidenced by positive responses of both the natural and artificial tracers at the middle U-tube, located an average 2.3m below the pre-injection GWC. The major CO2 increase to ∼60mol% and transition from sampling formation water with dissolved gas to sampling free gas occurred several weeks after the initial breakthrough. After another ∼3 months the CO2 content in the lowest U-tube, a further average 4.5m deeper, increased to ∼60mol%, similarly accompanied by a transition to sampling predominantly gases. Around this time, the CO2 content of the upper U-tube, located in the gas cap and an average 10.4m above the pre-injection GWC, increased to ∼20mol%. Subsequently, the CO2 content in the upper U-tube approaches 30mol% while the lower two U-tubes show a gradual decrease in CO2 to ∼48mol%, resulting from mixing of injected and indigenous fluids and partitioning between dissolved and free gas phases. Lessons learnt from the CO2CRC Otway Project have enabled us to better anticipate the challenges for rapid deployment of carbon storage in a commercial environment at much larger scales.

[2]  D. Peng,et al.  Two- and Three-Phase Equilibrium Calculations for Coal Gasification and Related Processes , 1980 .

[3]  Stefan Bachu,et al.  Acid-gas injection in the Alberta basin, Canada: a CO2-storage experience , 2004, Geological Society, London, Special Publications.

[4]  R. Reid,et al.  The Properties of Gases and Liquids , 1977 .

[5]  A. Lothe,et al.  Reservoir geology of the Utsira Formation at the first industrial-scale underground CO2 storage site (Sleipner area, North Sea) , 2004, Geological Society, London, Special Publications.

[6]  David R. Cole,et al.  Gas-water-rock interactions in Frio Formation following CO2 injection: Implications for the storage of greenhouse gases in sedimentary basins , 2006 .

[7]  C. Anderson,et al.  Australia's first geosequestration demonstration project-the CO2CRC otway basin pilot project , 2007 .

[8]  H. Helgeson,et al.  Thermodynamics of hydrothermal systems at elevated temperatures and pressures , 1969 .

[9]  B. Mayer,et al.  Geochemical monitoring of gas-water-rock interaction at the iea Weyburn CO2 Monitoring and Storage Project, Saskatchewan, Canada , 2005 .

[10]  C. Hofstee,et al.  CO2 Storage and Enhanced Gas Recovery at K12-B , 2009 .

[11]  Jim Underschultz,et al.  Geochemical monitoring at the CO2CRC Otway Project: tracer injection and reservoir fluid acquisition , 2009 .

[12]  B. B. Benson,et al.  The solubility and isotopic fractionation of gases in dilute aqueous solution. IIa. solubilities of the noble gases , 1989 .

[13]  C. H. Whitson,et al.  Peng-Robinson predictions for hydrocarbons, CO2, N2, and H2 S with pure water and NaCI brine , 1992 .

[14]  Iain Wright,et al.  Plume development around well KB-502 at the In Salah CO2 storage site , 2009 .

[15]  Sandeep Sharma,et al.  The CO2CRC Otway Project: Overcoming challenges from planning to execution of Australia’s first CCS project , 2009 .

[16]  K. Brown,et al.  Weyburn CO 2 monitoring and storage project , 2005 .

[17]  D. Peng,et al.  A New Two-Constant Equation of State , 1976 .

[18]  W. G. Mook,et al.  Isotopic fractionation between gaseous and dissolved carbon dioxide , 1970 .

[19]  Sally M. Benson,et al.  The role of hydrogeological and geochemical trapping in sedimentary basins for secure geological storage of carbon dioxide , 2004, Geological Society, London, Special Publications.

[20]  Susan D. Hovorka,et al.  The U-Tube: A Novel System for Acquiring Borehole Fluid Samples from a Deep Geologic CO2 Sequestration Experiment , 2005 .

[21]  John H. Weare,et al.  An equation of state for the CH4-CO2-H2O system: II. Mixtures from 50 to 1000°C and 0 to 1000 bar , 1992 .

[22]  Sally M. Benson,et al.  Implications of Surface Seepage on the Effectiveness of Geologic Storage of Carbon Dioxide as a Climate Change Mitigation Strategy , 2002 .

[23]  Takashi Ohsumi,et al.  Case study of geochemical reactions at the Nagaoka CO2 injection site, Japan , 2008 .

[24]  Ray Leuning,et al.  Atmospheric monitoring and verification technologies for CO2 geosequestration , 2008 .

[25]  W. G. Mook,et al.  CARBON ISOTOPE FRACTIONATION BETWEEN DISSOLVED BICARBONATE AND GASEOUS CARBON-DIOXIDE , 1974 .

[26]  V. Majer,et al.  Henry's law constant and related coefficients for aqueous hydrocarbons, CO2 and H2S over a wide range of temperature and pressure , 2008 .

[27]  F. Mutelet,et al.  Predicting the phase equilibria of CO2+hydrocarbon systems with the PPR78 model (PR EOS and kij calculated through a group contribution method) , 2008 .

[28]  Ernie Perkins,et al.  A Review of Tracers in Monitoring CO2 Breakthrough: Properties, Uses, Case Studies, and Novel Tracers , 2009 .

[29]  Jim Underschultz,et al.  CO2 storage in a depleted gas field: An overview of the CO2CRC Otway Project and initial results , 2011 .

[30]  Richard H. Worden,et al.  Geological storage of carbon dioxide , 2007, Geological Society, London, Special Publications.

[31]  Sally M. Benson,et al.  Measuring permanence of CO2 storage in saline formations: the Frio experiment , 2005 .

[32]  Ray Leuning,et al.  Assurance monitoring in the CO2CRC Otway Project to demonstrate geological storage of CO2: Review of the environmental monitoring systems and results prior to the injection of CO2 , 2008 .

[33]  Allan H. Harvey,et al.  Henry’s Constants and Vapor–Liquid Distribution Constants for Gaseous Solutes in H2O and D2O at High Temperatures , 2003 .

[34]  Jean-Noël Jaubert,et al.  VLE predictions with the Peng–Robinson equation of state and temperature dependent kij calculated through a group contribution method , 2004 .

[35]  M. O'Sullivan,et al.  Modeling the phase partitioning behavior of gas tracers under geothermal reservoir conditions , 2001 .

[36]  C. Boreham,et al.  The U-tube sampling methodology and real-time analysis of geofluids , 2009 .

[37]  C. Boreham,et al.  Abundance and carbon isotopic composition of neo-pentane in Australian natural gases , 2008 .

[38]  Barry Freifeld,et al.  Real‐time quadrupole mass spectrometer analysis of gas in borehole fluid samples acquired using the U‐tube sampling methodology , 2006 .

[39]  Gunter Borm,et al.  Status Report on the First European on-shore CO2 Storage Site at Ketzin (Germany) , 2008 .