proposed analysis from the well file review
TRANSCRIPT
Proposed Analysis from the Well File Review Technical Workshop Series: Well Construction/Operation and Subsurface Modeling
EPA-Research Triangle Park • April 16, 2013 Jeanne Briskin and Nathan Wiser
EPA Study of the Potential Impacts of Hydraulic Fracturing on Drinking Water
Resources
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• Assess whether hydraulic fracturing may impact drinking water resources
• Identify driving factors that may affect the severity and frequency of impacts
EPA Study Goals:
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For more information: http://www.epa.gov/hfstudy
Hydraulic Fracturing Water Cycle
WATER CYCLE STAGES
Water Acquisition → Chemical Mixing → Well Injection → Flowback and Produced Water → Wastewater Treatment and Waste Disposal
Water Acquisition
Chemical Mixing
Well Injection
Flowback and Produced Water
Wastewater Treatment and Waste Disposal
Surface Water
Ground Water
Wellhead
Recycling Facility
Disposal Well Wastewater
Treatment Plant
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Primary Research Questions
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Large volume water withdrawals from ground and surface waters? Water Acquisition
Surface spills on or near well pads of hydraulic fracturing fluids? Chemical Mixing
Surface spills on or near well pads of flowback and produced water?
Flowback and Produced Water
Inadequate treatment of hydraulic fracturing wastewaters?
Wastewater Treatment and Waste Disposal
The injection and fracturing process? Well Injection
What are the potential impacts on drinking water resources of:
Well Injection
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• How effective are current well construction practices at containing gases and fluids before, during, and after fracturing?
• Can subsurface migration of fluids or gases to drinking water resources occur, and what local geologic or man-made features might allow this?
Secondary Research Questions
Subsurface Migration Modeling Retrospective Case Studies
Ongoing Research Projects Literature Review Service Company Analysis Well File Review
Well File Review
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GOAL Identify practices or factors that may impact drinking water resources
Identify Hydraulically Fractured Wells • Provided by nine hydraulic fracturing service companies • Fractured between Sept. 2009 and Sept. 2010
Select Wells for Well File Review • Select statistically representative sample of wells from nine oil
and gas operators of various sizes • Wells include different geographic areas and completion types
Extract and Analyze Well File Data • Well construction practices • Hydraulic fracturing practices, including water acquisition and
wastewater disposal
Well Locations
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Shale gas basins (EIA, 2011)
Oil and gas production wells
Example Well Completions
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Ground Surface
True vertical depth is highly variable
Note: Not to scale; conductor casing, wellbore holes and cement not shown
Liner
Surface casing
Production casing or Open hole
Intermediate casing
“toe” “heel”
Hydraulically fractured perforations or open hole
Vertical Wells Deviated Well Horizontal Well
Information Requested
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• Geologic maps and cross sections • Daily drilling and completion records • Mud logs • Open hole logs, such as porosity and resistivity logs • Description of well casings installed • Cased hole logs, such as cement evaluation logs • Pressure testing results of installed casing • Up-to-date wellbore diagram • Pre- and post-hydraulic fracturing reports, including
volumes/additives used • Source(s) of water used • Chemical analyses of fluids (used in treatment, water zones,
offset locations, flowback) • Microseismic monitoring results • Spill/incident reports
Proposed Graph for Analysis
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Generic Well Diagram
Cem
ent C
ement
Cem
ent Cem
ent
Vertical Separation
HF Zone
Vertical Separation between HF Zone and Ground Surface (Bar Graph)
Num
ber o
f Wel
ls
Distance (feet)
Inherent Protectiveness LESS MORE
If multiple zones are fractured, distance between ground surface and
uppermost zone is graphed
Diagram not to scale
Proposed Graph for Analysis
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Generic Well Diagram
Cem
ent C
ement
Cem
ent Cem
ent
Vertical Separation
HF Zone
Vertical Separation between HF Zone and Top of Cement (Bar Graph)
Num
ber o
f Wel
ls
Distance (feet)
Inherent Protectiveness LESS MORE
If multiple zones are fractured, distance between top of cement and
uppermost zone is graphed
Diagram not to scale
Top of Cement
Proposed Graph for Analysis
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Generic Well Diagram
Cem
ent C
ement
Cem
ent Cem
ent
HF Zone
Distribution of Cement Bond Indices (Box and Whiskers Plot)
Cem
ent B
ond
Inde
x
Distance Interval Above Uppermost Perforation (feet)
Diagram not to scale
Cement Bond Index Measure of bond quality (0-100%) obtained from cement bond logs
0%
100%
Zonal isolation indicated
LESS
MORE
Proposed Graph for Analysis
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Generic Well Diagram
Cem
ent C
ement
Cem
ent Cem
ent
HF Zone
Zones and Degree of Cement (Bar Graph)
Perc
ent o
f All
Cas
ing
Strin
gs
Inherent Protectiveness MORE LESS
Diagram not to scale
Partially- or Un-Cemented Interval
• Are water zones present? • Are hydrocarbon (HC)
zones present?
Fully Cemented
No HC or water
HC Only Water Only
HC and Water
Zones in Partially- or Un-Cemented Intervals
Proposed Graph for Analysis
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Top View Distance to Nearby Faults (Bar Graph)
Num
ber o
f Wel
ls
Distance (feet)
Separation between Wellbore and Fault
LESS MORE
Vertical Wellbore
Horizontal Wellbore
Distance
Distance
Other Potential Factors of Interest
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• Surface casing setting depth vs. drinking water resource depth • Trend in water usage – fresh vs. recycled • Flowback volumes and disposition • Patterns of additives used as a function of geologic lithology treated • Pre-stimulation casing test pressure vs. maximum treatment pressure • Spills and the remedial actions taken during and after hydraulic
fracturing • Degree of monitoring and other data available in file to assure the
operator that conducting hydraulic fracturing is protective of drinking water resources
– Examples: Formation water sampling to confirm presence/absence of underground
source(s) of drinking water Frequency of cement evaluation (i.e. cement bond logs) Annular monitoring during hydraulic fracturing Offset well monitoring during/after hydraulic fracturing
Session Outline
• Finding the drinking water resource (Williams) • Well construction and integrity (Syed) • Cement to isolate and hydraulic fracture (Tipton) • Cement challenges (Badalamenti) • Leaky wells (Ingraffea) • Systems to verify barriers (op de Weegh) • Field level isolation (Carey) • Different well experiences (Hemenway)
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