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

10

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

11

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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