GISERA’s water research projects in northern NSW 1. Impacts of CSG depressurisation on the Great Artesian Basin (GAB) flux [ Sreekanth et al, CSIRO Land and Water, Jun 18] 2. Data-worth and spatial design of groundwater monitoring network in the Narrabri Gas Project area [Sreekanth et al, CSIRO Land and Water Mar 18] 3. Improving the representation of the impact of CSG in groundwater models [ Connell et al, CSIRO Energy Nov 18] GISERA water research NSW| 30 Aug 2018 | 1
Impacts of CSG depressurization on Great Artesian Basin flux Sreekanth Janardhanan, Trevor Pickett, Dennis Gonzalez, Tao Cui, Mat Gilfedder, David Rassam, Matthias Raiber, Axel Suckow, Kate Holland, Damian Barrett, Dan O’Sullivan, Alec Deslandes, Helen Beringen, Nicola Proctor 30 August 2018
Stratigraphy Inter-burde den 1 Inter-burde den 2 GISERA water research NSW| 30 Aug 2018 | 3
Conceptualisation in the numerical model Basin Formation type Model layer Zone 1 Namoi alluvium alluvium 1 - 2 Zone 3 Surat Basin Inter-burden 3 - 5 Zone 6 Surat Basin Pilliga Sandstone 6 Gunnedah Basin Interburden 7 – 9; 11 - 13 Zone 8 Gunnedah Basin Coal 10, 14 GISERA water research NSW| 30 Aug 2018 | 4
Objectives ● Measurement and analysis of new environmental tracers and hydrochemistry data to improve conceptual understanding of recharge ● Integrating the knowledge derived from new data and ongoing work (OWS projects BA, FAM) into the conceptual understanding of the Surat and Gunnedah basins ● Predictive analysis of potential impacts of CSG development on drawdown and GAB fluxes ● Use the predictive uncertainty anlysis to inform data-worth and monitoring strategies 5 GISERA water research NSW| 30 Aug 2018 | |
Groundwater model built for the Namoi Bioregional Assessments Groundwater modelling for the Namoi subregion (Sreekanth et al, 2018) 6 GISERA water research NSW| 30 Aug 2018 | |
Probabilistic modelling approach for a generic CSG development scenario ● Water production rates are not hard-wired as a boundary condition in the model ● Instead, the model simulates the water production for a given depressurization target ● Accounts for the uncertainty in CSG water production 7 GISERA water research NSW| 30 Aug 2018 | |
Sensitivity analysis Vertical hydraulic conductivity of the inter-burden layers: most sensitive parameter that influences the propagation of depressurization upwards into the Pilliga Sandstone GISERA water research NSW| 30 Aug 2018 | 8
Conceptualisation of hydraulic properties Observed depth-dependency and spatial variability from core, DST, packer and pump test data ( Aryal et al, 2018; Turnadge et al, 2017, Sreekanth et al, 2018) 9 GISERA water research NSW| 30 Aug 2018 |
Inter-burden hydraulic properties Vertical hydraulic conductivity of the numerical model layer 7 immediately underneath the Pilliga Sandstone ( Purlawaugh formation) AQUIFER AQUTARD Santos GIA GISERA water research NSW| 30 Aug 2018 | 10
Spatial variability of vertical hydraulic conductivity in the inter- burden layer 8 GISERA water research NSW| 30 Aug 2018 | 11
Key findings – CSG induced GAB Flux changes (a) (b) GISERA water research NSW| 30 Aug 2018 | 12
Predicted CSG impacts to water volumes in the GAB aquifer 0.0001 5% predicted maximum CSG flux impact 0.06 Median of predicted maximum CSG flux impact 0.27 95% precited maximum CSG flux impact 3 Stock and Domestic right estimate 29.68 LTAAEL 42.4 Estimated recharge (SRS) 295 Recharge (GAB NSW total) 0 50 100 150 200 250 300 350 Water volume (Giga litre/year) Other estimates Highly parameterized model Parsimoniously parameterized model Volume (GL/y) Source Estimated Recharge (GAB NSW Total) 295 BRS report (Habermehl, 2009) Estimated recharge Southern Recharge Source 42.4 NSW Water Sharing Plan (SRS) Lont-term Annual Average Extraction Limit 29.68 NSW Water Sharing Plan (LTAAEL) Stock and domestic use 3.0 NSW Water Sharing Plan Unlikely that the maximum CSG flux impact in 2.3 This study any year will exceed Likely that the maximum CSG flux impact will 0.06 This study be around Likely that CSG flux impact will be more than 0.0001 This study 1 3 GISERA water research NSW| 30 Aug 2018 | |
Conclusion - 1 ● Depressurization of coal seams could potentially induce small changes in groundwater flux from the GAB aquifer to deeper formations ● The median value of the predicted maximum flux losses is 60 ML/year which is about 0.2 % of the Long-term Annual Average Extraction Limit set for the the Southern Recharge Source. GISERA water research NSW| 30 Aug 2018 | 14
Data-worth and spatial design of groundwater monitoring network in the Narrabri Gas Project area Sreekanth Janardhanan, Dan Gladish, Trevor Pickett, Dennis Gonzalez, Dan Pagendam, Tao Cui, Mat Gilfedder, David Rassam, Damian Barrett, Dan O’Sullivan, Helen Beringen, Nicola Proctor 30 August 2018
Method overview START Flow model Particle tracking Geostatistical spatial MODELS (MODFLOW USG) Mod-PATH3DU models Travel times, distances, MONTE-CARLO Drawdown in model Baseline WQ variance velocities SIMULATIONS layers LINEAR GLOBAL Optimal monitoring Data worth analysis ANALYSIS OPTIMIZATION design(s) STOP GISERA water research NSW| 30 Aug 2018 | 16
Maximum drawdown impacts GISERA water research NSW| 30 Aug 2018 | 17
Travel distances within a modelling period of 100 years GISERA water research NSW| 30 Aug 2018 | 18
Ensemble predictions to inform potential future monitoring locations to observe CSG-induced drawdown Dmax – Maximum CSG-induced drawdown Layer 6 Layer 7 Layer 12 Tmax – Time at which maximum CG-induced drawdown occurs GISERA water research NSW| 30 Aug 2018 | 19
Monitoring network used in data-worth analysis Monitoring Potential monitoring bore sites network design ● Monitoring within predicted drawdown area to verify and refine the predictions GISERA water research NSW| 30 Aug 2018 | 20
Current GAB monitoring bores within the predicted drawdown area ● Current density of montoring bores ~4.2 bores/100 km 2 GISERA water research NSW| 30 Aug 2018 | 21
Receptor locations for data-worth analysis GISERA water research NSW| 30 Aug 2018 | 22 GISERA water research NSW| 30 Aug 2018 |
Data worth of observations a GISERA water research NSW| 30 Aug 2018 | 23
Conclusion – 2 ● Probabilistic predictive analysis resulted in a median predicted drawdown to be less than 0.2m for most of the areas within and beyond the gas project area ● Probabilistic particle tracking analysis indicated that velocity of groundwater flow in the Pilliga Sandstone aquifer is slow and particles may travel on the order of 100s of metres within a simulation period of 100 years. ● The current density of GAB monitoring bores is approximately 4.2 bores/100 km 2 ● Data-worth analysis indicated that nested monitoring bores within the 95 th percentile drawdown area and especially monitoring formations underneath the Pilliga Sandstone returns maximum data-worth ● A design for a network of 10 bores and the data-worth emerging from that is demonstrated in this study GISERA water research NSW| 30 Aug 2018 | 24
IESC advice to decision maker on Narrabri Gas Project –gaps addressed by GISERA study IESC comment number GISERA research Q1.2, Q1.13, Q2.15 Improve confidence in Used target heads in coal seams/formations modelled heads in target seams instead of (projects 1). Project 3 will help to refine this specified flux boundary condition for coal further seasm gas Q1.3, Q1.6f Groundwater model Investigated two different parameterisation parameterisation, calibration, uncertainty schemes, undertook calibration, sensitivity and sensitivity analysis. and uncertainty analysis (projects 1 and 2) Monitoring points for data collection could be identified based on uncertainty analysis Q1.6b, 2.17 “measuring heads directly Our monitoring design study (project 2) above and below tightest aquitards would establishes this using quantitative analysis allow constrain aquitard properties” that multi-level piezometers would be most useful in refining predictions GISERA water research NSW| 30 Aug 2018 | 25
IESC advice to decision maker on Narrabri Gas Project –gaps addressed by GISERA study IESC comment GISERA study Q1.6d Consideration should be given to use We have used the data/knowledge from methods like Turnadge et al (2017) in Turnadge et al and have assessed the assessing effects of changing permeability drawdown effects from varying and storativity particularly in areas with permeability and storativity in the overlying sensitive receptors uncertainty analysis Q1.6e “range of different hydrogeological In this study we used environmental tracers conceptualisations and methods to address to understand recharge. We also evaluated uncertainties in recharge ” wide range of variabilities in recharge in the model while predicting the impacts Q1.6h “robust estimates of We have spatially varying evapotranspiration in the model” evapotranspiration considering vegetation height GISERA water research NSW| 30 Aug 2018 | 26
Thank you Sreekanth Janardhanan Senior Research Scientist t +61 7 3833 5565 e Sreekanth.janardhanan@csiro.au w gisera.org.au
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