SLIDE 1
Evolution of a Remedial Injection Program in Saprolite
Stephen W. Kirschner, P.E. and Craig E. Petko, P.G. (Advanced GeoServices Corp., West Chester, PA) John Liskowitz (ARS Technologies, Inc., New Brunswick, NJ)
Evolution of a Remedial Injection Program in Saprolite Stephen W. - - PowerPoint PPT Presentation
Evolution of a Remedial Injection Program in Saprolite Stephen W. - - PowerPoint PPT Presentation
Evolution of a Remedial Injection Program in Saprolite Stephen W. Kirschner, P.E . and Craig E. Petko, P.G. (Advanced GeoServices Corp., West Chester, PA) John Liskowitz (ARS Technologies, Inc., New Brunswick, NJ) Background North Carolina
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Site Conceptual Model
Topographical High Residual clayey silts Decomposed bedrock (Saprolite) 6 m Steeply fractured Paleozoic Quartz / Feldspar Granite & Hornblende Diorite (TCE migration to 250+ ft)
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∗ Residual clayey silts
∗ Direct Push Geoprobe, Solid Flight Augers
∗ Decomposed bedrock (Saprolite)
∗ Solid Flight Augers, Sonic Drilling
Encountered Geology (Drilling methodology)
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∗ Restricted access in side building ∗ Minimize business disruption to current tenants ∗ Saprolite highly variable ∗ Metamorphic bedrock matrix ∗ Effective reagent distribution in heterogeneous geology ∗ Off-site migration ∗ No risk-based protocols in REC Program
Insitu Remediation Challenges
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Low Clearance
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Indoor Air Quality Protection
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∗ Fracturing
∗ Phase I
∗ Hydraulic Fracture Emplacement
∗ Phase II
∗ Pneumatic Fracture Emplacement
∗ Treatment Injectant Material
∗ Vegetable Oil Emulsion (VOE) ∗ Chase water (NaOH added during Phase II)
Injection Materials
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Phase I Fracture Emplacement
Extension of Initial Bedrock Injection Program
d Return Water acker strength limitations Prolonged cutting
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Summary of First Method
∗ Top Down Approach ∗ Direct-Push 2-inch steel pipe
∗ Retract 6 inches ∗ Hydraulically cut notch in formation ∗ Propagate fracture with guar gel and sand ∗ Inject SRS, Sodium Carbonate & Chase Water
∗ Drive to next depth and repeat
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Phase I Fracture Emplacement Summary
∗ 4 wells & 22 injection intervals ∗ Refusal 18 ft to 57 ft (avg = 34 ft) ∗ Est. ROI = 20 to 30 ft ∗ Vol. treated = 6,000 cy ∗ 595 gals of 60% VOE concentrate
100 200 300 400 500 600 700 800 900 1000 50 100 150 200 250 300 350 400 450 500 Time
Injection Event
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Phase II – Full-Scale
Hydraulic Fracture Emplacement Pneumatic Fracture Emplacement
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Pneumatic Fracturing Emplacment Injection Process
(By Changing Viscosity of Treatment Media more effective distribution in Subsurface results)
Conventional Hydraulic Injection of Liquid Pneumatic Fracture Emplacement
The same liquid blended with gas as it becomes atomized Shows hydraulic injection of liquid
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Additional Improvements Implemented During Phase II
Use of Small Rotosonic Rig enabled injections to
- ccur at any target depth without encountering
Refusal
Formation improvement
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∗ Roto-sonic and Hollow Stem Augering used to advance holes ∗ Fracture entire overburden column first using nitrogen to establish fracture network and increase formation permeability (before injecting treatment material). ∗ Once hole fractured, advance tooling to depth and begin injections bottom up manner ∗ Straddle Packers used to isolate 3 foot injection interval ∗ Liquid atomized injection using nitrogen on site improved treatment material distribution
Phase II Methods
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Injection Variability (Injection ROI was increased as depth increased and more competent Material Encountered) 30 Foot Depth 50 Foot Depth
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Baseline Conditions - Est. 123,500 ft2 plume size & Post Phase I Injection Conditions - Est. 54,000 ft2 plume size
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Post Phase I Injection Conditions - Est. 54,000 ft2 plume size & Post Phase II Injection Conditions- Est. 32,000 ft2 plume size
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∗ Phase I (Hydraulic Fracturing Emplacement) ∗ Radius of Injection = 20 to 25 ft ∗ Volume treated = 6,000 cy ∗ Treatment Depth = 18 ft to 57 ft bgs (average = 34 ft) ∗ Phase II (Pneumatic Fracture Emplacement) ∗ Radius of Injection = 15 to 45 ft (decreasing w/ depth) ∗ Volume treated = 22,000 cy ∗ Treatment Depth = 45 ft to 77 ft bgs (average = 60 ft)
Phase I & II Comparison
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∗ Includes: Mob/Demob, Drilling, Injection, All Materials, Oversight, & Restoration
∗ Phase I Hydraulic Fracture Emplacement (22 injections – Avg. 34 ft Depth)
∗ $3,000 per injection or $11 per cubic yard ∗ Time to Complete 9 days
∗ Phase II Pneumatic Fracture Emplacement (81 injections – Avg. 60 ft Depth)
∗ $3,800 per injection or $13 per cubic yard ∗ Time to Complete 30 days
Total Capital Costs Summary
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∗ Difficult & Varied Saprolite geology required a more advanced drilling method during Phase II to adapt to penetrate less weathered zones ∗ Significant formation changes occurred over short distances that impacted distribution and caused injection hole by hole customization ∗ Goal of creating in-situ bioreactor by distributing treatment material throughout majority of target area achieved ∗ Significant (99%) VOC reductions achieved ∗ Appreciable cost savings resulted due to better reagent distribution
Conclusions
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