Using Modelling to Improve Wastewater Disposal … Modelling to Improve Wastewater Disposal...
Transcript of Using Modelling to Improve Wastewater Disposal … Modelling to Improve Wastewater Disposal...
Matrix Solutions Inc. 1
Using Modelling to Improve Wastewater Disposal Strategies
Gordon MacMillan, P.Geol. Matrix Solutions
Jens Schumacher, M.Sc., Matrix Solutions
Maxime Claprood, Ph.D., P.Eng., Matrix Solutions
Michael L. Brewster, M.Sc. P.Geol., Devon Canada
Matrix Solutions Inc. 2
Presentation Objectives
1) Complete the story of Grand Rapids disposal
2) Raise awareness of hydrogeology related disposal issues
3) Contribute to the rhetoric on the value of models
Matrix Solutions Inc. 3
Presentation Objectives
• Every model is wrong but some models are useful
• Garbage in…….… garbage out
• Models are too time consuming to be useful
Value of these statements can be tested by substituting “model” with “math”
More useful clichés might be
“Models provide a formal test of logic”
“Models can support decision making”
A x = b
math math
math math
math
Matrix Solutions Inc. 4
IntroductionIn-situ oil sands projects generate two wastewater streams that need to be handled. The most common approach to handling wastewater is downhole disposal. Poor selection of disposal zone can impair:
1) Bitumen recovery
2) Make-up water quality of wells in the same aquifer
3) Water quality of a non-saline aquifer
Matrix Solutions Inc. 5
Introduction
Wastewater disposal strategy can affect the project economics (SOR and CAPEX on disposal wells and pipeline) design
Desired Outcomes
o Minimize cost
o Minimize risk
o Maximize regulator and stakeholder acceptance
Key Decisions
1) Aquifer selection
2) Number of wells
3) Pipelines and other infrastructure
4) Well placement
5) Distribution of rates
Matrix Solutions Inc. 6
Introduction
If the modelling objective (question) is well defined, modelling can inform decisions and optimize the project design. dobs
Key Decisions (m)
1) Aquifer selection
2) Number of wells
3) Pipelines and other infrastructure
4) Well placement
5) Distribution of rates
Desired Outcomes (dobs)
Minimize cost
Minimize risk
Maximize regulator and stakeholder acceptance
𝛷 𝑚 = 𝑑𝑜𝑏𝑠 − 𝐹𝑚22
Numerical Model (F)
Matrix Solutions Inc. 7
Wastewater disposal near a steam chamber
Example 1
Matrix Solutions Inc. 8
Example 1
Wastewater disposal near a steam chamberProblem: Steam chambers interact with bottom water aquifers. Wastewater disposal could inadvertently cool chamber and increase water handling.
Matrix Solutions Inc. 9
Example 1
Wastewater disposal near a steam chamber
Modelling Objective: Create a tool that can account for the interaction between the steam chamber and the aquifer.
Identify areas of risk (i.e. areas sensitive to pressure change)
Plan disposal strategies to match desired reservoir conditions
Evaluate potential cumulative effects from other operators
Matrix Solutions Inc. 10
Example 1
Wastewater disposal near a steam chamber
Model Data:- 11 years of disposal or pumping at 50 wells- Transient pressures recorded at 50 observation locations- Large amount of geologic control: seismic; pre-
Cretaceous unconformity; 6,261 well control points
Model Approach: - Use high resolution McMurray Aquifer isopach- Include water imbalance at the SAGD pads as a source
term - Use a fast 2D model to calibrate (15 min solution time)- Use a high degree of parameterization (1,800 adjustable
parameters) to allow for potential heterogeneity
Matrix Solutions Inc. 11
Example 1
Wastewater disposal near a steam chamber
Matrix Solutions Inc. 12
Example 1
Wastewater disposal near a steam chamber
- 50 source and disposal wells
- Rates variable over time at all wells
Matrix Solutions Inc. 13
Example 1
Wastewater disposal near a steam chamber
Matrix Solutions Inc. 14
Example 1
Wastewater disposal near a steam chamber
Matrix Solutions Inc. 15
Example 1
Wastewater disposal near a steam chamber
Matrix Solutions Inc. 16
Example 1
Wastewater disposal near a steam chamber
• Calibrated transmissivitieswere relatively smooth and honored setting
• Some SAGD pads had a large influence on heads
• Model did good job of reproducing changes in head
Matrix Solutions Inc. 17
Example 1
Wastewater disposal near a steam chamber
Results- Water imbalance in SAGD chamber translates to water
gain/loss in the aquifer
- Transient head data is sensitive to this imbalance
- Numerical model was able to reproduce and can be used to evaluate future operation strategies
Identify areas of risk (i.e. areas sensitive to pressure change)
Plan disposal strategies to match desired reservoir conditions
Evaluate potential cumulative effects from other operators
Matrix Solutions Inc. 18
Wastewater migration toward make-up water supply wells
Example 2
Matrix Solutions Inc. 19
Example 2
Wastewater migration toward make-up water supply wellsProblem: Wastewater disposal is planned in close proximity to a make-up water supply well and could affect water quality over time.
Wastewater Disposal
Matrix Solutions Inc. 20
Example 2
Wastewater migration toward make-up water supply wells
10 km
Modelling Objectives: 1) Predict likelihood of
wastewater breakthrough at make-up water well.
2) Predict concentration profile over time at make-up water well.
800 m
Matrix Solutions Inc. 21
Example 2
Wastewater migration toward make-up water supply wellsModel Data:
- High resolution transmissivity field from 2D model- Facies characterization of areas to north and south- Vshale interpretations at 100 wells available as digital files- Salinity data from 107 logs- Pre-Cretaceous unconformity and other geologic knowledge
Model Approach:
- Use high resolution McMurray Aquifer transmissivities- Create a geomodel of hydrofacies in a one township area- Generate 50 stochastic geomodel realizations- MODFLOW predictions of wastewater migration in 22 geomodels- Use stochastic predictions of TDS to optimize disposal strategy
Matrix Solutions Inc. 22
Example 2
Wastewater migration toward make-up water supply wells
Above: 3D visualization of facies in 100 boreholes
Left: vertical distribution of facies as volume fraction
Right: One of two training images
Matrix Solutions Inc. 23
Example 2
Wastewater migration toward make-up water supply wells
• 50 geomodel realizations
– honor hard data
– reflect geologic knowledge of channel orientation, meander, and width
– Reflect proportions of facies (e.g. 48% sand)
• Facies upscaled to 2.5 m tall by 75 m wide
Matrix Solutions Inc. 24
Example 2
Wastewater migration toward make-up water supply wells
• 2D transmissivity field is exactly the same in each MPS model
• Regen disposal fluid predictions at source well ranged from 1 to 19% wastewater
• Non-MPS simulations predicted less than 2% wastewater
Matrix Solutions Inc. 25
Example 2
Wastewater migration toward make-up water supply wells
Results- Wastewater migration is highly dependent on geologic
structure (i.e. connectivity of sand facies)
- Single hydrofacies approach underestimates wastewater migration in this geologic setting
- Numerical model was able to test alternative disposal strategies (e.g. rates and completion intervals) so that risk can be minimized
Matrix Solutions Inc. 26
Understanding physical setting in the context of Grand Rapids disposal
Example 3
Matrix Solutions Inc. 27
Example 3
Understanding physical setting in the context of Grand Rapids disposal
Problem: High salinity area of the Grand Rapids is an attractive zone for wastewater disposal but is near non-saline area.
Lower Grand Rapids
Calculated TDS 4,000 – 60,000
(mg/L)
Matrix Solutions Inc. 28
Example 3
Understanding physical setting in the context of Grand Rapids disposal
Modelling Objective: Support decision making on the use of the Lower Grand Rapids Aquifer as a disposal zone by:
1) Evaluating regional structures and groundwater flow for a mechanism responsible for the high salinity
2) Evaluating the likelihood of wastewater impacting water quality in the non-saline areas of the aquifer.
Matrix Solutions Inc. 29
Example 3
Understanding physical setting in the context of Grand Rapids disposalModel Data:
- Regional scale characterization and model (Hayley et al. 2014)
- 7 base flow estimates- Hydraulic head estimates at 1,359 DSTs and 444 wells- Transient heads at 147 locations responding to 10 years of
water use (or disposal)
Model Approach:
- Use regional scale model to reproduce natural gradients and test for stagnation area
- Use particle tracking to evaluate extent of wastewater migration and if the edge of the saline zone will move as a result of disposal
Matrix Solutions Inc. 30
Example 3
Understanding physical setting in the context of Grand Rapids disposal
Regional model:- Extends from ground surface to 50 m
below pre-Cretaceous unconformity- Includes 28 hydrostratigraphic units- Total volume of 15,000 km3
discretized with 331,000 nodes
Matrix Solutions Inc. 31
Example 3
Understanding physical setting in the context of Grand Rapids disposal
Empress Channel Gross Isopach Lower Grand Rapids Hydraulic Head
Matrix Solutions Inc. 32
Example 3
Understanding physical setting in the context of Grand Rapids disposal
Lower Grand Rapids Calculated TDS 4,000 – 60,000 (mg/L)
Matrix Solutions Inc. 33
Example 3
Understanding physical setting in the context of Grand Rapids disposal
• Hydraulic heads in the Grand Rapids are strongly influenced by the Empress Channels and result in stagnant, high TDS, area
~ 20 km
Zone of Relative Stagnation
Matrix Solutions Inc. 34
Example 3
Understanding physical setting in the context of Grand Rapids disposal
• Relative to the McMurray Aquifer, the disposal zone sands are laterally continuous and homogeneous
• Particle tracking deemed sufficient to evaluate extent of wastewater migration
• Particle tacking completed during simultaneous pumping and injection and evaluated after 90 years
102/08-21-074-05W4
Matrix Solutions Inc. 35
Christina Channel
Wiau Channel
Sunday Creek Channel
Example 3
Understanding physical setting in the context of Grand Rapids disposal
No interference predictedChristina Channel
Wiau Channel
Sunday Creek Channel
Saline Water Interface
No interference predicted
Matrix Solutions Inc. 36
Example 3
Understanding physical setting in the context of Grand Rapids disposal
Results- Area of hydraulic stagnation between Wiau and
Sunday Creek channels correlates with area of high TDS
- Single hydrofacies approach was used for wastewater migration in this geologic setting
- Modelling results indicate zone can be safely used for wastewater disposal
Matrix Solutions Inc. 37
Conclusions
Matrix Solutions Inc. 38
Conclusions
• Wastewater disposal can pose a risk to project operations and the environment
• By effectively framing the problem and leveraging all valuable data modelling supported the following findings:
– Disposal near SAGD chambers has a causal link to SAGD water balance
– Extent of wastewater migration is highly dependent on geologic heterogeneity
– An aquifer not traditionally considered for wastewater disposal is an environmentally responsible option
Matrix Solutions Inc. 39
Acknowledgements
Christina Lake Regional Water Management Agreement (CLRWMA) partners:
Devon Canada CorporationCenovus FCCL Ltd.MEG Energy Corp.
Rebecca Jacksteit, M.Sc., Cenovus FCCL Ltd.
Scott Rayner, M.Sc., MEG Energy Corp.
Beiyan Zhang, Ph.D., Matrix Solutions Inc.
Louis-Charles Boutin, P.Eng., Matrix Solutions Inc.
Kevin Hayley, Ph.D., P.Geoph, Matrix Solutions Inc.
Matrix Solutions Inc. 40
Matrix Contacts
Gordon MacMillan, P.Geol. Matrix SolutionsPh. 403.513.2280
Jens Schumacher, M.Sc., Matrix SolutionsPh. 403.206.0515
Maxime Claprood, Ph.D., P.Eng. Matrix SolutionsPh. 418.529.4480
Matrix Solutions Inc. 41
References
Hayley K., J. Schumacher, G. MacMillan and L. Boutin. 2014. Highly parameterized model calibration with cloud computing: an example of regional flow model calibration in north east Alberta, Canada. Hydrogeology Journal (2014) 22: 729-737.