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Published byJacqueline Hewatt Modified about 1 year ago

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Outline LNAPL multi-phase fluid mechanics review LNAPL metrics review LNAPL transmissivity (T n ) principles Applicability Summary Introduction

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LNAPL at the Pore Scale LNAPL co-exists with water in aquifer pores LNAPL only partially fills the aquifer pore space The degree of LNAPL saturation depends upon lithology and fluid properties Sediment Grains Wetting Fluid (Water) Non-Wetting Fluid (Air or LNAPL) Filling Large Pore Spaces Multi-Phase Fluid Mechanics RTDF 2006

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Ideal vs. Observed LNAPL Saturations RTDF 2006 Multi-Phase Fluid Mechanics Saturation curve height = thickness of mobile LNAPL interval

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T vs. T n / T n vs. S n Transmissivity (T) for water – Unit cross-section, gradient, time – Aquifer thickness – Single fluid (k rw drops out ) LNAPL Transmissivity (T n ) – Unit cross-section, gradient, time – Mobile LNAPL interval thickness – Multi-fluid (k rn matters ) Multi-Phase Fluid Mechanics “How Much, How Fast”

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Ideal LNAPL Metric Collective property incorporates: – Aquifer properties (e.g., permeability) – Aquifer type (sand vs. clay) – LNAPL properties (e.g., viscosity) – LNAPL type (condensate vs. crude oil) Fundamental or characteristic property – Repeatable Saturation / mass driven Easy and cheap to measure LNAPL Metrics

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Non-Ideal Metrics - Thickness LNAPL Metrics Same mass exhibits different thicknesses in different soil types Inconsistent under varying hydrostatic conditions Modified after RTDF (2006) Modified after Kirkman (2009)

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Non-Ideal Metrics – Recovery Data LNAPL Metrics Benefits Direct measure of remediation performance Provides predictive data for decline curve analysis Problems Strongly affected by system operational settings Varies by technology – not directly comparable Can’t be used to predict performance prior to startup

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T n – An Improved Metric LNAPL Metrics

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LNAPL Transmissivity (T n ) 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 Transmissivity (T n ) Principles

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Applicability – Uses for T n 1.Alternative to laboratory S n 2.Model calibration parameter 3.Technical impracticability threshold 4.Remediation design parameter 5.Operational progress metric 6.Recovery end point Applicability

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Applicability - TI Demonstration Applicability 3.Technical Impracticability (TI) requires either: – Recovery system data “Can I please turn it off now?” Direct recoverability threshold metric – Data from a pilot test and modeling study “Can I please not turn it on?” Robust calibration parameter for TI modeling

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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 – Design parameters Equipment sizing Waste management / recycling volumes – Design cost-benefit analysis Projected operational lifetime Capital vs. mobile infrastructure Applicability

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Applicability – Operational Progress 5.Operational Progress Metric – Recovery data decline curve analysis (progress towards endpoint) – Non-recovery wells to monitor plume progress to endpoint Applicability

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T n Endpoint Analysis 6.Hydraulic recovery end point (0.3 to 0.8 ft 2 /day) Applicability

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T n Endpoint Analysis Applicability

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Summary T n is an improved metric for hydraulic recoverability Four calculation methods: – Baildown / manual skimming testing – Recovery data analysis – Physical properties analysis – Tracer testing T n use as a metric – Indirectly as a robust model calibration parameter – Directly as a recoverability threshold ( ft^2/day) Remediation and T n – TI threshold – Design parameter – End point for hydraulic recovery Summary

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