David Macfarlane & Scott Dalzell Irrigation Australia Conference – Gold Coast 5 June 2014

1. The science and implementation of chemical amendment of coal seam water as an irrigation resource David Macfarlane & Scott Dalzell Irrigation Australia Conference – Gold Coast 5 June 2014

2. GLNG CS Water Irrigation Footprint

3. Irrigation Footprint-Fairview

4. Irrigation Footprint - Roma

5. 3 CS Water as an Irrigation Resource CS watersalts are predominantly NaCl and NaHCO3 In Santos GLNG footprint this generally varies from 2000 to 12,000 microsiemens (µS)/cm in EC or about 1300 to 8000 mg/L salinity Fairview Project Area has EC median / range of 3670 µS/cm / 1900-11,000 µS/cm and SAR median / range of 143/ 75 to 268 Roma Shallow Gas Project Areas has EC median / range of 3620 µS/cm / 2180-10,000 µS/cm and SAR median / range of 106 / 84-179.

6. 3 Current & Potential Commercial CS Water Treatment Options Reverse Osmosis with micro-filtration &/or ion exchange front ends Chemical amendment process 1: Associated Water Amendment Facilities (AWAF) adding prescribed quantities of sulphuric acid and micronised gypsum Chemical amendment process 2: AWAF treatment of raw CS water + RO permeate blends Chemical amendment process 3: Land Amendment Irrigation (LAI) involving suitable quality CS water and suitable soils and soil surface addition of prescribed quantities of sodium bentonite sulphur prills and agricultural gypsum Chemical amendment process 4: Potential to blend IX filtrate or RO permeate with up to 8000 µS/cm CS water and utilise via LAI

7. Major soils and variability in an irrigation area

8. 3 Treating CS water with an AWAF Influent water ranges from 2000-3400 µS/cm EC with SAR up to 130 Up to 400 L/ML 98% sulphuric acid is applied to reduce bicarbonate alkalinity from ~1000 mg/L to 200 mg/L & reduce pH from 8-9 to 5.3 Acidified water is stored for 1-2 days and then dosed with micronised gypsum (<35 microns) to reduce irrigation water SAR and maintain SAR/EC balance for structurally/hydraulically stable soils Current AWAFs have output ECs of 3000 to 4000 µS/cm have safe target SARs of 18-30 AWAF chemistry: Acid dosing: 2NaHCO3+ H2SO4 ==> Na2SO4 + 2H2O + 2CO2 Every mole of sulphuric acid used generates 2 moles CO2 SAR reduction using calcium only: SAR = [ Na ] / SQRT { ( [Ca]) / 2 } where concentrations are in milliequivalents per litre.

9. Commercial use of chemical amendment of CS water Santos GLNG has built 3 AWAF facilities at the Fairview field: AWAF1 – 10 ML/d capacity AWAF2 – 2 ML/d capacity AWAF3 – 4 ML/d capacity Designed plant CS water amendment capacities:

10. Plan of AWAF 1 – 10 ML/d Control room & irrigation pump station Micronised gypsum silos & batching plant 2 x 5 ML storage tanks Ozonation unit Filters & pumps Sludge tank degassing tanks Acid dosing intake

11. 3 AWAF Drip and Pivot Irrigation

12. AWAF drip &pivot irrigation 217 ha of AWAF pivot irrigation – pivots 10-50 ha Rhodes grass/leucaena pastures or fertilised Rhodes grass pastures Systems are designed to apply 6-10 ML/ha/yr over 5-6 years 72 ha drip irrigated Rhodes grass/leucaenadrip lines 1 m apart, up to 4 ML/ha/yr over 5 yrs Standard baseline application of 3 t/ha gypsum prior to irrigation Pastures fertilised with N, P, & S Expected levels of production are: >4 LSU/ha (1 LSU = 400 kg steer) producing >1000 kg beef/ha/yr 1075 ha Chinchilla White Gum on Springwater and 200 ha CWG on Fairview with surface and sub-surface, 4 m tree row spacing and expected marketable sawlog yield yr 25 of 250 m3/ha

13. 3 AWAF 1 Applied Research 2009-2011 Investigation of United States experience of chemical amendment Required acid dosing for specific bicarbonate levels in treated water Target soil solution Na, Ca, bicarbonate requirements following irrigation for sustainable soil condition Pre- and post-treatment bicarbonate dynamics in CS water Periodic land amendment gypsum requirements to protect against high rainfall Engineering integrity limits of sulphuric acid dosing Gypsum solubility and CS water pH relationships and optimum dosing rates Gypsum vs gypsum + Mg SO4 for SAR control in hypermagnesic soils Managing the hydroscopicity of micronised gypsum Periodic acid flushing to avoid calcium salts in drip lines and emitters Variability in emitter output TDS conversions for CS water for salinity loading calculations

14. LAI – US Experience LAI implemented in >95 irrigation projects since 1999 Typical Powder River Basic CS water quality: Salinity 2500-3600 µS/cm; SAR 40-80; GPS precision spreading of gypsum and sulphur required overlapping S drops soil pH to 3 → strips poor lucerne growth Apply 2-5 ML/ha in summer over 7-9 yr period For average 3 m deep clay loam soil under LAI SAR ranged from 6-18 and averaged 10-12; EC ranged from 4-5 dS/m Lower costs/ML treated than for RO or Ion Exchange (e.g. Higgins Loop) water treatment systems

15. Land Amendment Irrigation - US

16. Requirements for commercial LAI Soil hydraulic conductivity >40 mm/day Soil depth >1.5 m and starting profile salinity <1 dS/m CSG water applied EC <4000 µS/cm Target crops have high yield/water use salinity thresholds If reach trigger values (≤ 75% threshold) reached provide salinity flushing irrigations – do not restrict water use of the crop pump Peripheral non-irrigated buffers of deep rooted perennial species up to 100 m width required No major aquifer within 35 m below root zone and separated by stratigraphies of 15-20% porosity Minimum area of 50 ha / block, up to 4 x 50 ha blocks within 2 km of each other sufficient to attract a reliable land amendment contractor

17. Good potential LAI soils Vertosol Dermosol Shallow A horizon Chromosol

18. Managing CS water with Pivot LAI Regularly apply small amounts of S-bentonite on poorly buffered soils to prevent fluctuations in soil pH Induce leaching (~10-15% leaching fraction) to maintain soil root-zone salinity within acceptable limits Leaching irrigation applied during winter when crop ET demand is low likely to most effective Field observations of soil hydraulic conductivity backup routine soil chemistry monitoring Continuous/periodic environmental monitoring  adaptive management  preventsadverse impacts on soil/water resources LAI can be implemented on long-term, large-scale centralised, or medium term decentralised or short-term local appraisal irrigation projects where water quality is suitable.

19. Root zone impacts AWAF vs LAI

20. Large intact soil cores at UQ

21. Soil impacts of LAI - after 9ML/ha LAI & 400 mm rainfall

22. Comparing AWAF, AWAF + extra gypsum, LAI and local bore water irrigation systems

23. IR6(3) comparative trial key data Current comparative field trial

24. Using broad scale soil association/land resource maps to focus LAI soils reconnaissance

25. Environmental impacts-AWAF vs LAI vs ROP systems

26. Management of environmental risks of chemical amendment Environmental risks/ mitigation: Fail to maintain sustainable soil chemical conditions / real time soil monitoring and periodic soil & analysis, use proven salinity / sodicity /water balance modelling, treat water or amend soils for stoichiometrically correct levels of calcium and sulphuric acid entering system for bicarbonate and SAR management Increase soil salinity / regular monitoring, developsoils with low-moderate starting salinity, adequate hydraulic conductivity, manage irrigation practice & crop selection for target water / salt leaching fractions beyond root-zone Movement of CS water salinity beyond the irrigation environment impacting surface water or groundwater / regular monitoring, irrigation application & buffer management controls, sub-root zone unsaturated zone being >35 m deep of 15-20% porosity, conservative 2-D seepage modelling, adaptive irrigation management

27. Total costs - centralised CS water management

28. Comparative process risks of LAI vs AWAF as chemical amendment water treatment systems

29. Santos GLNG business benefits Chemical amendment of CS water delivers the following benefits: Flexibility in CS water management planning Reduced water treatment costs Shorter lead time to beneficial CS water use accelerates field development Least cost centralised and decentralised water treatment options for commercial and appraisal irrigation projects for suitable water quality LAI offers enhanced process safety and reliability over AWAF and ROP + brine injection systems based on 5.7 years Fairview experience Superior environmental outcomes - best practice LAI vs best practice AWAF and ROP irrigation system management will consistently reduce the risk of soil structural degradation by maintaining superior soil EC/SAR balance in surface soil