Erik Svenson Leonid Germanovich Todd Schweisinger Larry Murdoch Supported by NSF EAR TRANSIENT CHANGES in FRACTURE APERTURE DURING HYDRAULIC WELL TESTS in FRACTURED GNEISS LAR m (GT)

FRACTURED BEDROCK Hydraulically active sheet fractures Wells Sweet City Quarry Elberton, GA Fracture signifance geometry response

OBJECTIVE/MOTIVATION Single Well Pressure & Displacement Approach: Develop Field Scale Test Interpret Data with (HM) Model Motivation: Predict movement of fluids in low transmissivity rock Transmissivity Fracture Storativity Heterogeneities (Leakage and Blockage)

HYDROMECHANICAL REGIMES Pressure and Displacement Pumping: Fracture Aperture: (-) Withdrawal Injection (+) ClosingDilatingOpening Propagating Asperities in contact

CONCEPTUAL MODEL

THEORETICAL MODEL P  P  P  p  P P,P : Continuity in finite difference  : Estress-displacement   Sneddon integral, semi-analytical   

Transient Responses During Slug Test t 0.37 MODEL RESULTS (SLUG TESTS) T = d well 2 /t 0.37 Similar to Hvorslev Method Transmissivity, T T = 0.1 cm 2 /sec Slug Injection

FRACTURE COMPLIANCE ~2.5x10 -6 m/m H 2 0 Late-time derivative (slope) of displacement vs. head curve ff Fracture Compliance,  f Inversely proportional to fracture normal stiffness Fracture Compliance During Slug ff time Hysteresis S f =  w  f Storage: Depth: 25 meters Fracture Storativity: Specific Storage of interval: S s =  f /length

INFLUENCE OF HETER0GENEITIES Leakage away from well Blockage away from well Hysteresis becomes less pronounced as leakage is placed closer to well Hysteresis becomes more pronounced for blockage

EXTENSOMETER Displacement Transducer Packer Exploded View of Retractable Anchor Anchor Packer

BASIC FIELD RESULTS (25m deep ) Slug-In Test (13 Liter Slug) Fracture Compliance Plot Δ Head:6.4 m H 2 0 Fracture Compliance,  f : 1.75 x10 -6 m/m H 2 0 Δ Displacement: 3.3 µm Specific Storage, S s :~ m H Transmissivity: 0.5 cm 2 /s

DEPTH VARIATIONS WELL-(LAR-4) FRX. LOCATION 25.5m 27.0m NORMALIZED COMPLIANCE PLOTS Repeatable Results Variable: Compliance Shape δ max : 2μm δ max : 3μm

K & S DISTRIBUTIONS Leakage Blockage Three conductive zones (Blue Highlight) Most of water released from storage in upper 2 zones Leakage within 8m of borehole (Yellow Highlight) Well located ~ 6m away

CONCLUSIONS displacements Feasible to measure in-situ displacements DisplacementsDisplacements during slug tests: up to 20  m Use and displacementsUse head and displacements to subsurface to characterize subsurface Fracture Compliance (  f ): 0.1  m/(m of drawdown) -- 5  m/m Specific Storage (Single Well): ~ to m -1 S s Proportional  f, estimates ~ to m -1 Estimate leakage blockage away from boreholeEstimate leakage and blockage away from borehole

Erik Svenson Leonid Germanovich Todd Schweisinger Larry Murdoch Supported by NSF EAR TRANSIENT CHANGES in FRACTURE APERTURE DURING HYDRAULIC WELL TESTS in FRACTURED GNEISS LAR m (GT)

Comparison to Hvorslev T = [C ] r c 2 /t 0.37 T = [0.5 ln(R e /r w )] r c 2 /t 0.37 Hvorslev’s Eqn. This work 3.7 < C < 6, from graph So, for Hvorslev in frx’d rock R e > 1600r w Most applications of Hvorslev would underestimate K in this system tT/r c 2