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


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


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


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


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


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)


Wastewater disposal near a steam chamber

Example 1


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.


Example 1


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


Example 1


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


Example 1



Example 1


- 50 source and disposal wells

- Rates variable over time at all wells


Example 1



Example 1


• 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


Example 1


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


Wastewater migration toward make-up water supply wells

Example 2


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


Example 2


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


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


Example 2


Above: 3D visualization of facies in 100 boreholes

Left: vertical distribution of facies as volume fraction

Right: One of two training images


Example 2


• 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


Example 2


• 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


Example 2


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


Understanding physical setting in the context of Grand Rapids disposal

Example 3


Example 3


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)


Example 3


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.


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


Example 3


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


Example 3


Empress Channel Gross Isopach Lower Grand Rapids Hydraulic Head


Example 3


Lower Grand Rapids Calculated TDS 4,000 – 60,000 (mg/L)


Example 3


• 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


Example 3


• 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


Christina Channel

Wiau Channel

Sunday Creek Channel

Example 3


No interference predictedChristina Channel

Wiau Channel

Sunday Creek Channel

Saline Water Interface

No interference predicted


Example 3


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


Conclusions


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


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 Contacts

Gordon MacMillan, P.Geol. Matrix SolutionsPh. 403.513.2280

[email protected]

Jens Schumacher, M.Sc., Matrix SolutionsPh. 403.206.0515

[email protected]

Maxime Claprood, Ph.D., P.Eng. Matrix SolutionsPh. 418.529.4480

[email protected]

mailto:[email protected]




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.

Using Modelling to Improve Wastewater Disposal … Modelling to Improve Wastewater Disposal...

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