Slide 1

Report
Outline
• LNAPL multi-phase fluid mechanics review
• LNAPL metrics review
Introduction
• LNAPL transmissivity (Tn) principles
• Applicability
• Summary
LNAPL at the Pore Scale
Sediment Grains
Multi-Phase Fluid Mechanics
• LNAPL co-exists with
Wetting Fluid (Water)
water in aquifer pores
• LNAPL only partially fills
the aquifer pore space
• The degree of LNAPL
saturation depends
upon lithology and fluid
properties
Non-Wetting Fluid (Air or
LNAPL) Filling Large Pore Spaces
Ideal vs. Observed LNAPL Saturations
Multi-Phase Fluid Mechanics
Saturation curve height = thickness of mobile LNAPL interval
RTDF 2006
T vs. Tn / Tn vs. Sn
“How Much, How Fast”
• Transmissivity (T) for water
– Unit cross-section, gradient, time
Multi-Phase Fluid Mechanics
– Aquifer thickness
– Single fluid (krw drops out)
Tw  K wb
Kw 
 w gkkrw
w
• LNAPL Transmissivity (Tn)
– Unit cross-section, gradient, time
– Mobile LNAPL interval thickness
– Multi-fluid (krn matters)
Tn  K n bn
Kn 
 n gkkrn
n
Ideal LNAPL Metric
• Collective property incorporates:
– Aquifer properties (e.g., permeability)
– Aquifer type (sand vs. clay)
LNAPL Metrics
– LNAPL properties (e.g., viscosity)
– LNAPL type (condensate vs. crude oil)
• Fundamental or characteristic property
– Repeatable
• Saturation / mass driven
• Easy and cheap to measure
Non-Ideal Metrics - Thickness
• Same mass exhibits
different thicknesses
in different soil types
LNAPL Metrics
• Inconsistent under
varying hydrostatic
conditions
Modified after Kirkman (2009)
Modified after RTDF (2006)
Non-Ideal Metrics – Recovery Data
LNAPL Metrics
Benefits
Problems
•
Strongly affected by system
operational settings
•
Varies by technology – not
directly comparable
•
Can’t be used to predict
performance prior to startup
•
Direct measure of remediation
performance
•
Provides predictive data for
decline curve analysis
Tn – An Improved Metric
Tn Advantages
LNAPL Metrics
• Direct numeric measure of hydraulic
recoverability
• Varies directly with LNAPL saturation /
mass
• Normalizes all sites to a single
measurement standard
• Multiple Methods
• Measurable prior to, during and after
remediation
Transmissivity (Tn) Principles
LNAPL Transmissivity (Tn)
• Analog to aquifer transmissivity
• Provides basis for mobility /
recoverability analyses
• Four measurement methods
– Baildown / skimming tests
– Recovery data analysis
•
•
•
•
skimming
Vacuum enhanced skimming
Total fluids pumping
Multi-phase extraction
– Physical properties / modeling
– Tracer tests
• Hydraulic recovery only
• Dissolved and vapor phase risk
issues are separate
Applicability
Applicability – Uses for Tn
1.
2.
3.
4.
5.
6.
Alternative to laboratory Sn
Model calibration parameter
Technical impracticability threshold
Remediation design parameter
Operational progress metric
Recovery end point
Applicability - TI Demonstration
3. Technical Impracticability (TI) requires either:
– Recovery system data
• “Can I please turn it off now?”
• Direct recoverability threshold metric
Applicability
– Data from a pilot test and modeling study
• “Can I please not turn it on?”
• Robust calibration parameter for TI modeling
Applicability – Remediation Design
4. Remediation design parameter
– Compare different technologies (calibrated model)
• Technology-specific production curves
• Predicted rate and total volume decline curve analyses
• Sustainability
Applicability
– Design parameters
• Equipment sizing
• Waste management / recycling volumes
– Design cost-benefit analysis
• Projected operational lifetime
• Capital vs. mobile infrastructure
Applicability – Operational Progress
5. Operational Progress Metric
– Recovery data decline curve analysis (progress towards endpoint)
Applicability
– Non-recovery wells to monitor plume progress to endpoint
Tn Endpoint Analysis
Applicability
6. Hydraulic recovery end point (0.3 to 0.8 ft2/day)
Applicability
Tn Endpoint Analysis
Summary
• Tn is an improved metric for hydraulic recoverability
• Four calculation methods:
– Baildown / manual skimming testing
– Recovery data analysis
– Physical properties analysis
Summary
– Tracer testing
• Tn use as a metric
– Indirectly as a robust model calibration parameter
– Directly as a recoverability threshold (0.3-0.8 ft^2/day)
• Remediation and Tn
– TI threshold
– Design parameter
– End point for hydraulic recovery

similar documents