st Sep 8 Matteo Loizzo Schlumberger Carbon Services

st Sep 8 Matteo Loizzo Schlumberger Carbon Services engineering manager Schlumberger Private Oxyfuel Flue Gas, Steel and Rock Implications for CO 2 Geological Storage 1 International Oxyfuel Combustion Conference, Cottbus (Germany), 2009

Geological storage performance factors 2 Schlumberger Carbon Services Schlumberger Private “I’ll pay you 50 €/t to take 6 Mt/year for the 40 years of life of my power plant, with a reliability of 4 , and with no measurable leaks. ”

Some definitions – European Directive 2009/31/EC n – Deep saline formations and (depleted) oil and gas reservoirs n "A CO 2 stream shall consist overwhelmingly of carbon dioxide. Concentrations of all [contaminants] shall be below levels that would […] adversely affect the integrity of the storage site or the relevant transport infrastructure” Schlumberger Carbon Services Schlumberger Private ““Geological storage of CO 2” means injection accompanied by storage of CO 2 streams in underground […] rock layers” 3

What is in the rock before we inject CO 2? 4 n EOR/EGR: Enhanced hydrocarbon Recovery – Oil recovery rate ~40% of OOIP ü Gas: >90% ü Issues: unconnected/heterogeneous reservoirs, pressure decline, water… – CO 2 is lighter (but not so much) so it can sweep the “ceiling” and reasonably miscible so it reduces fingering ü Minimum Miscibility Pressure ~10 MPa ü Water Alternate Gas to sweep the floor as well – Oil, water, gas Depleted (gas) reservoirs very low pressure gas, and water Schlumberger Carbon Services n Deep saline formations salty water (brine) n Schlumberger Private – Initial production, then pressure maintenance (water or gas), then tertiary recovery

Where does the water go? 5 Water needed for most contaminants’ reactions n CO 2 -water displacement n ü Like “salting out” does it really affect injectivity? – Diffusion of CO 2 and contaminants at the edges of the plume ü Depends on exchange surface, upside solubility trapping n Shut-downs water flows back – Near reservoir and wells affected Schlumberger Carbon Services Source: Azaroual et al. , ENGINE Workshop, 2007 Schlumberger Private – Sharp front, residual saturation Srw – Evaporation of residual water in the plume

Contaminants in deep rock – experience and insights 6 Injection of flue gas for pressure maintenance n In-situ combustion n ü Including “rich air” after N 2 removal – Low and high temperature total O 2 injection rate, heavier hydrocarbon chains n Raw Seawater Injection – Oxygenated water n Acid gas disposal – CO 2+H 2 S Schlumberger Carbon Services Schlumberger Private – Air injection

Potential issues – Sulfate-Reducing Bacteria 7 n Reduce sulfur (SO 4/SO 3) to H 2 S – Form injectivity-reducing biofilms in near wellbore ü Biofilms enhance steel corrosion in tubulars n Requirements – Nutrients: volatile fatty acids, available from (long chain) hydrocarbon LTO – depleted reservoirs; phosphates (? ); nitrogen ü Can use thermodynamic inhibitors like methanol or diethylene-glycol, or other C sources – Temperature: surface to ~90ºC n Risk mitigation – Low p. H, high salinity (deep saline formations), O 2 inhibit growth – NOx (nitrates) control SRB by bio-exclusion Schlumberger Carbon Services n Aerobic bacteria? Schlumberger Private – H 2 S can lead to the precipitation of Fe. S and S (with NO 2), reducing injectivity

Potential issues – H 2 S geochemistry 8 Weak acid n Can precipitate iron sulfide or elemental sulfur (with nitrites) n n Risk mitigation – Iron in reservoir (hematite or siderite) can scavenge H 2 S n Additional issues – “Sour” steel corrosion, Stress Corrosion Cracking Schlumberger Carbon Services Schlumberger Private – Reservoir plugging and injectivity reduction

Potential issues – SO 2 geochemistry 9 n Very soluble in water, oxidizes to sulfuric acid ü Smaller acid area with carbonates, reduced mineralization potential – Might reduce Fe. S scaling? n Readily precipitates anhydrite (Ca. SO 4) and barite (Ba. SO 4), with limited solubility – “swap” with CO 2 – Reservoir plugging, injectivity reduction HCl/HF used for reservoir stimulation ü Bigger risk for carbonates, interaction with wormholing? Schlumberger Carbon Services Schlumberger Private – O 2 scrubber, requires metal catalysts? – Simulations (Xiao et al. ) suggest a p. H 0 zone ~10 -100 m from the injection well

Potential issues – O 2 geochemistry 10 n Hydrocarbon oxidation – Low temperature (no sustained combustion) or high temperature – Requires “light” oil (C 7 or heavier) n Rock oxidation – Iron in rock or water, Fe 2+ Fe 3+, which then precipitates as ferric hydroxide competing with H 2 S reduction? n Risk mitigation – Not enough O 2 Schlumberger Carbon Services Schlumberger Private ü LTO may slightly damage recovery oil emulsions

Potential issues – corrosion 11 n CO 2 “sweet” corrosion, reasonably mild – Uniform (vs. pitting), possible protection from Fe. CO 3 layer Contaminants will increase corrosion, synergistic effects – O 2 concentration seems to be detrimental ü Removes Fe. CO 3 ü Will produce pitting in 13 Cr Corrosion Resistant Alloy <10 ppb ü May passivate steel, contrasted by SO 2 – H 2 S from SRB may add Sulfide Stress Corrosion and pitting – Chlorides in formation water lead to Stress Corrosion Cracking Schlumberger Carbon Services Schlumberger Private n

Corrosion control 12 n Corrosion Resistant Alloy n Risk mitigation – Coating hard to protect casing connections, wireline damage – Inhibitors expensive, may play a role in SRB growth n Main point: corrosion requires water! – Dehydrating CO 2 streams proved most effective corrosion control ü Reduction or elimination of Water Alternate Gas EOR strategy by Kinder Morgan – Injection breaks and formation water flow back ü May be reduced by formation plugging at the edge of the plume Schlumberger Carbon Services Schlumberger Private – Very expensive metallurgy, poorly tested for all contaminants in flue gas

Conclusions 13 n Flue gas-rock interactions – Precipitation of insoluble scale and plugging of rock pores in the near wellbore seems to be the main risk SO 2, H 2 S, O 2 Iron and carbonates risk factors, but some competing effects may help Some standard control mechanisms in use in the O&G industry Characterize reservoir chemistry (rock and water), core floods – “Preventive” hydraulic fracturing to mitigate scaling? – Biofilms might be an issue, especially with intermittent injection n Corrosion – No water ü Water flow back during injection breaks – Transport “weakest link” ü Biggest impact of CRA adoption Schlumberger Carbon Services Schlumberger Private ü ü