This document discusses the use of LNAPL transmissivity (Tn) in remediation design, progress evaluation, and determining endpoints. Tn is presented as an improved metric for quantifying mobile LNAPL impacts that can be determined through various field methods and recovery data analysis. The document outlines how Tn can be applied within the TRRP-32 framework, including using Tn values to select remediation technologies, calibrate models, evaluate operational performance, and determine when technical impracticability of hydraulic recovery has been reached. Threshold values of 0.3-0.8 ft2/day for Tn are presented as potential decision points for changing remediation approaches.
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Lnapl Tn For Tceq Tf 2010 100504 Sec 1to3
1. LNAPL Transmissivity (Tn)Remediation Design, Progress and Endpoints H2A Environmental, Ltd. J. Michael Hawthorne, P.G. mhawthorne@h2altd.com May 2010
Broad Brush – information dense slides, but we’ll cover much material quickly – handouts provide detail for reference
A number of people were very generous in helping me to prepare for this presentation in various ways, including (Read list). Dr. Charbeneau, Huntley and Sale did not work with me directly, but their previous work provided much of the background for my work.
Start by providing CONTEXTFour types of questions Tn can help you answer:Understanding Your Site DataComparing your LNAPL Occurrences from well to well and site to sitePredicting the hydraulic recovery rates and durations of LNAPL wellsManaging LNAPL programs across large numbers of sites to prioritize and manage potential LNAPL migration risk and recovery potential
One last thing before we start: This work is based primarily on three forerunner analogs:HydrogeologyAquifer Testing and Slug Testing to get K/T to understand water movement and production (hydraulics)NORMALIZES all sites to one (1) measurement standard so you can NUMERICALLY:AnalyzeComparePredictThen use Aquifer K and T values to PREDICT and DESIGN:Pumping Rates andROCMultiphase Fluid Mechanics – Hydrogeology with another layer of COMPLEXITYLNAPL and water SHARING SPACE in an aquifer – NO PANCAKE – Density / Viscosity / Wettability and other PHYSICAL PROPERTY differences so DO NOT FLOW the sameSaturation Distribution – LNAPL Saturation highest in/near capillary fringe, always <100%Relative Permeabilities – highest LNAPL mobility in/near the capillary fringeModeling Tools to Easily Deal with Complexities – LDRM by Dr. Charbeneau / APIPetroleum Engineering TOOLS for multiphase fluid production – Decline Curve AnalysisRTA and EUR
Outline
Go Through SlideWhy do we talk about LNAPL T instead of K – frequently deal with K in waterLNAPL is a saturation distribution with K that varies substantially from bottom to top of mobile LNAPL profileAverage K can be used, but it is an average of a large range of values so doesn’t accurately represent either extremeHighest K and mobility at/near the capillary fringe, average K will underpredict hereTn incorporates range of K values across an entire LNAPL thickness, and so better represents the total picture of LNAPL SATURATION and MOBILITY
Word of Caution: devil is in the details – must understand LCSM and all variables and adjust through time for changing variables or you will have garbage
Think of these as two opposite overlapping funnels that net out as additive (drawdown plus vacuum)
Critical point – inexpensive Tn values across your site give a high degree of modeling confidence without the high cost of site wide frozen core analyses