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Carbon Sequestration in Sedimentary Basins Module VIII: Biosolids Injection – LA TIRE Project

Carbon Sequestration in Sedimentary Basins Module VIII: Biosolids Injection – LA TIRE Project. Maurice Dusseault Department of Earth Sciences University of Waterloo. Deep Injection of Biosolids…. Injection deep below GW level

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Carbon Sequestration in Sedimentary Basins Module VIII: Biosolids Injection – LA TIRE Project

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  1. Carbon Sequestrationin Sedimentary BasinsModule VIII: Biosolids Injection – LA TIRE Project Maurice Dusseault Department of Earth Sciences University of Waterloo

  2. Deep Injection of Biosolids… • Injection deep below GW level • Gets rid of sewage biosolids, animal biosolids without environmental risk • Permanent isolation of bioactive agents, heavy metals, etc. • CH4 is generated, and quite rapidly at higher temperatures • Extra C is sequestered permanently, mostly as an anthropogenic coal!

  3. Current Methods Straightforward Soil enhancement Highly local (short transport distance) Risks to water, soil Odors … DBI “New” technology True disposal Central facility No odors No water risks CH4 generated for beneficial use Carbon sequestered Waste co-disposal Comparison of Methods

  4. Based on Actual Experience Injection facility in Alberta, 1997

  5. Risks and Costs • The “true” cost of waste disposal… • Includes primary costs • Must also include risk costs • Must also include beneficial side effects • The “true” risks of waste disposal • Neutralizing bacteria, prions, viruses • Water contamination potential • Related risks (heavy metals in soils…) • The chances (risks) of abuse

  6. Conditions for Siting • Deep, well below potable water sources • In horizontal strata of great lateral extent • Stratum must be sufficiently thick & porous • Permeability must meet certain standards • Thick ductile overlying shales are desirable • At least one overlying permeable bed • Formation water briny, flowing horizontally • No exploitable resources to be impaired

  7. Ideal Lithostratigraphy possible SFI™ well locations flat or gently inclined strata surficial deposits mudstone limestone stringer silty shale blanket sand in a thick shale 3000-10,000’ channel sands in a silty shale continuous blanket sand limestone 5-30 km not to scale

  8. Steps in Implementation • Siting: geological and reservoir study • Interaction with regulatory agencies • Reservoir analysis: capacity, injection strategy, k, compressibility, etc… • New wells or old well recompletion? • Design & install monitoring systems • Approach based on waste type, studies, siting… • Reporting, QC, regulatory interaction

  9. Slurry and Injection Unit • Screening, mixing, controlling, injecting, monitoring are the functions of the system • Mixing assures a uniform slurry: mobile unit includes auger mixing, washing through a screen, and density control in an auger tank • All systems are operated by hydraulic motors • Pumping is by a triplex PDP, supercharged with a centrifugal pump (hydraulic)

  10. Flow-Through System ground wastes make-up water conveyor hopper mix tank spray jets, auger-mixer screen (5x8 mm) auger centrifugal charger triplex pump injection well high pressure line

  11. View of SFI System

  12. SFI in the Field Typical Processing and Injection Equipment Operations can be fully enclosed for severe weather or odor control

  13. Typical Surface Uplift ~symmetric max slope ~1:5,000 10 cm uplift no uplift at 1.5 km distance 700 m deep waste site, 100-150 m radius maximum V ~ 16,000 m3

  14. Well Capacity • Proper formation choice is required • To date, the maximum injected in a single well is ~30,000 m3 sand, 200,000 H2O • Water dissipates into the sediments rapidly • We believe 106 m3 of slurry is quite feasible for a biosolids injection well • Monitoring and analysis allow continuous re-evaluation of capacity and well performance

  15. Solids Injection Advantages • Wastes are permanently entombed • Proper stratum choice gives exceptionally high environmental security (minimal risk) • No chance of “repository” impairment • No chance of surface H2O contamination • Generated gases can be collected • Costs are reasonable, even for difficult wastes • Technology is “well-established”

  16. Injection Cycles pressure repose period sand inj. 5 5 6 6 2 4 2 4 7 7 8 8 3 3 9 10 sv = 11.4MPa 1 1 24-hr cycle initial pore pressure = 4.6 MPa time

  17. Environmental Husbandry

  18. Current Technology

  19. Gas to Energy Biosolids Injection Facility Methane Production Biosolids Injection Methane Deep Biosolids Injection • Inject biosolids into old O&G reservoirs • Metals, bacteria, viruses, are isolated • CO2 generation does not take place • Anaerobic decomposi-tion forms CH4 • CH4 can be used • Small footprint • Solid C is sequestered

  20. A Brief History • Massive sand injection developed 1992-97 • Biosolids disposal plus CH4 generation plus CO2 sequestration concept in 1997 • Vancouver assesses, declines (2000) • City of Los Angeles approached in 1999 • Land spreading court case lost in 2001 • DBI passes all permitting needs (late 2001) • EPA letter of acceptance (Sept 2003) • Etc., etc., etc., etc., hearings, etc., • Project initiation date (Jan 2007) • First biosolids injection (Sept 2008!!!)

  21. Why Los Angeles? LA Basin oilfields are excellent geologic targets with known trapping mechanisms close to major LA sanitation plants LA lost a court case (2001), and will have to almost eliminate sludge spreading on fields (e.g. Kern County) by 2004-2005* With CH4 at $12 MBTU, DBI and gas recovery is substantially cheaper than secondary and tertiary treatment, & spreading *California keeps on giving temporary extensions…

  22. Los Angeles O&G Fields Hyperion Carson JWPC Terminal Island Site completed in summer 2008 OCSD Plant

  23. View of SFI System

  24. A DBI System

  25. DBI Advantages 5. Clean energy Gas to Energy Facility 2. Reduce greenhouse gas emissions CH4, CO2 landfarms Fresh water sand 4. Reduce transport costs Mud/shale Fresh water sand Sealing shale Brine filled sand Sealing shale Brine filled sand 1. Improve groundwater protection 3. Long-term carbon sequestration

  26. Uncertainties 1. How much gas will be produced, and how fast? 2. How much CO2 will be absorbed by formation water, and for how long? 3. How best to control or eliminate H2S ? 4. What are optimum injection parameters? Estimated gas production for 5 yrs of biosolids injection at 200 wt tons/day Injection Period

  27. Formation Response • Liquid bleed-off is rapid, allowing pressure decay and strain relaxation between injection episodes • Large target stratum provides necessary storage • Overlying shales provide hydrologic isolation from fresh water and stress barriers to minimize vertical migration • Solid wastes remain close to injection point due to high permeability induced fracture leak-off • Natural temperature, pressure, fluids, provide a good environment for anaerobic biodegradation waste pod water flow

  28. Typical Injection Parameters • Slurry density 1.15-1.35 • Injection rates 1-2 m3/min • Injection period 6-12 hours • Interval period 12-40 hours • Daily volumes 600-1200 m3/d These rates are sufficient to handle a city of 300,000 – 450,000 at a single site!

  29. Some DBI Details • CO2, H2S stripped from gas by dissolving in the water (CH4 has low solubility in H2O) • Carbohydrates have a 40% surplus of C; this is left behind: sequestered elemental carbon • No sludge ponds, no digesters … • Sealed DBI unit, no odor, no spray • May have to inoculate the biosolids with optimum bacteria for the T, pH conditions • Based on oilfield skills and technology

  30. Initial Compaction, DT • Biosolids slurry ( ~ 1.2) is injected for 8-10 hours each day, for several years… • Tslurry ~ 15°C, Tfmn ~ 40-50°C • Pore pressures dissipate, massive compaction occurs (non-linear behavior) • Formations are cooled by injectate • Gradual re-heating takes place as the geothermal regime is re-established • T effects, organics are compressible…

  31. 50 40 30 20 10 0 Compaction of Biosolids rapid slurry dewatering phase “classical” consolidation porosity “creep” of organic material +DT effects 2 yrs(?) biodegradation phase log(t)

  32. DT DT T Gradients - Injection Cold fluid injection A A conductive heat flux shale low k convective heat flux To high k B sandstone shale T To B d

  33. Methanogenesis Phase • Biowastes are essentially complex carbohydrates and fats… • CxHyOz, plus small amounts of S, N • Anaerobic, methanogenic bacteria break these molecules down • Available O becomes CO2 • Available H becomes CH4 • Perhaps traces of H2S if pH is right • Excess C remains as solid carbon (coal!) • This is accelerated coal & gas generation

  34. Forming of Carbon Evolved gases CH4 CO2 Complex carbohydrate CxHyOz (N,S) C-rich remnants NOx H2S (N can form nitrates, S other sulfur compounds) ~16% of mass of CHO converted to CH4

  35. T, Biological Activity, • Higher T accelerates biodegradation • Biodegradation = more compaction • The cold region must warm with time • Water viscosity is also affected (small) • Thus, a complex coupling exists among the compaction behavior with time and Fourier and Darcy diffusion with changing diffusivity parameters • It is rendered more complex yet…

  36. Gas Generation • Initially, there is no free gas, Sg = 0 • With time, Sg increases in the biosolid, decreasing water relative perm, kw • CH4 generation builds pressure until fracturing takes place (po > s3) • Gas is lighter than water, so Dr-driven gravitational segregation occurs • Gas flows upward through the biosolid and the porous medium (sandstone)

  37. Gas Migration, Segregation Injection well, later converted to a gas production well Gas cap Shale caprock Gas bubbles Sandstone Biosolids Base rock

  38. Chromatographic Gas Cleaning… • CH4 (75%), CO2 (25%), a bit of H2S, NOx • These gases start to bubble upward • But, the aqueous phase absorbs gas until it is saturated with each specie • CH4 is very insoluble (< 0.01 v/v/atm) • CO2 & H2S are highly soluble • As gases migrate upward, these are stripped by dissolution, but not CH4 • Slow moving H2O carries CO2, H2S away

  39. More Coupling… • CO2, H2S gases dissolve in the water • Gravity segregation occurs, displacing water from the system; this requires a gravity drainage flow model • Liquid flux carries dissolved gases away • Cleaned CH4 gas is produced through the well (p-V-T reservoir effects) • Excess carbon remains sequestered, • As well as the CO2 dissolved in water

  40. Los Angeles Project • Began in 1999 • All parties on board 2001 except EPA • EPA gave the go-ahead in Sept 2003 • Project plan filed in Dec 2003 • Final approval Jan-Feb 2007 • Biosolids injection started in 2009? • LA sludge after primary biodegradation • Sludge will be non-hazardous • Inoculate sludge with methanogenic thermophilic bacteria species? No…

  41. Los Angeles O&G Fields Hyperion Carson JWPC Terminal Island OCSD Plant

  42. Approach to Analysis • The process is highly complex… • Moving boundaries (injection, compaction) • Thermal effects (heating and cooling) • Pore pressure effects (fracturing…) • Biological decomposition • Gas generation and chromatographic effects • … • Currently, processes are treated in an uncoupled manner, approximate only

  43. Comments on Biosolids Inj. • Complicated coupled processes are typical in geomechanics • DBI concepts evolved from petroleum geomechanics • Formal simulation remains excessively challenging at present… • Massive non-linearities • Phase changes, biological activity • Many simultaneous diffusion, stress effects • Moving boundaries…

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