Transcript Slide 1
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