Laser-Induced Fluorescence & Tank Cleanups

Transcription

1 National Tank Conference September 2013 Laser-Induced Fluorescence & Tank Cleanups A Love Story Randy St. Germain, President Dakota Technologies, Inc.

2 What is LIF and how does it work? National Tank Conference September

3 fluorescence of fuels/oils (due to their PAH content) LIF responds ONLY to NAPL! NOT dissolved phase! NOT vapor phase! waveforms what LIF sees if probe window is in NAPL crude oil diesel waveforms what LIF sees if probe window is in NAPL fluorescence we see National Tank Conference September

4 LIF Optical Screening Tool Coupled with Direct Push generator umbilical breakout box remote display laser A/D scope e-deck LAN pc printer string pot rods cable split cap fiber optics Depth floating peg %RE National Tank Conference September

5 typical field setup LIF system temporarily coupled to direct push National Tank Conference September

6 what s behind those strange-looking LIF waveforms? National Tank Conference September

7 each fuel/oil type yields unique waveforms the size (height) scales approximately with concentration National Tank Conference September

8 long story short: waveform shapes change with fuels, oils, false positives National Tank Conference September

9 UVOST LIF waveforms of various NAPL types Jet/Kerosene Gasoline Diesels Oils National Tank Conference September

10 false positives/negatives most have short lifetimes and look odd vs. target fuel/oil National Tank Conference September

11 colorization of LIF (UVOST) logs are based on their 100s of waveforms in simplest form: blues indicate intact light fuels red/orange means highly weathered or heavy green/yellow means middle-weight fuels/oils or modestly National Tank Conference September

12 LIF system calibration OST LIF systems are calibrated with a known reference material similar to calibrating a photo-ionization detector (PID) with 100ppm isobutylene Dakota has used same reference emitter (RE) material since 1994 RE is placed on window just before each/every sounding all downhole LIF readings are normalized by the reference emitter (areas are calculated) - data is displayed as %RE RE method is used by all ROST and UVOST providers - globally National Tank Conference September

13 LIF waveforms grow larger with increasing NAPL content in the pore spaces (because the fluorescence gets brighter) diesel diesel clean 100 ppm 1000 ppm 10,000 ppm neat diesel how fluorescent ~= how much National Tank Conference September

14 what do actual field logs look like? National Tank Conference September

15 examples of typical field LIF logs both at the same gasoline LUST site each log contains 100s of waveforms only select few are called out at left the different colors in log fill alert us to different waveforms different waveforms means different chemistries/weathering National Tank Conference September

16 LIF systems log NAPL distribution which is tightly defined by geology in this sense LIF logs provide geologic insight, not just NAPL distribution National Tank Conference September

17 the shark s fin observed often with LIF in permeable homogeneous geologies LNAPL Saturation / Transmissivity The zone of highest LNAPL saturation has the highest LNAPL conductivity Low LNAPL saturation results in low LNAPL conductivity Vertical equilibrium (VEQ) conditions in a sand tank LNAPL Transmissivity = Sum T = K b o Hydraulic recovery rate is proportional to transmissivity for a given technology Well thickness does not dictate relative recoverability o o Saturation shark fin National Tank Conference September

18 unlike monitoring wells, which rely on assumptions to conceptualize NAPL in the adjacent formation LIF analyzes NAPL where it is no need to make decisions, where to place screens, etc. National Tank Conference September

19 site-wide NAPL heterogeneity duplicates are useful but when to apply? when most logs are differing from the others and validation sampling is planned i.e. where will the team gather representative samples at this site to confirm LIF findings? all these LIF logs were acquired at a small gasoline service station site on the same day reason for crazy differences - heterogeneity - glacial till National Tank Conference September

20 Dakota advocates doing duplicates with LIF at ~ 10% of locations to gain insight into NAPL heterogeneity National Tank Conference September

21 site-wide NAPL heterogeneity when are duplicates useful? NOT SO MUCH when every log is similar to the last no real driver exists because heterogeneity appears limited and behavior seems ideal National Tank Conference September

22 let s put it all together and examine a 4-day LIF investigation in 3D National Tank Conference September

23 coming soon: Dye-LIF for chlorinated DNAPLs based on TarGOST (the coal tar and creosote LIF) National Tank Conference September

24 Thank you! Randy St. Germain, President Dakota Technologies, Inc A 12 th St. North Fargo, ND Office: Mobile: