water considerations and hydraulic fracturing, ron green

Hydraulic Fracturing PanelHydraulic Fracturing Panel

Water ConsiderationsWater Considerations

Presented at

Texas Groundwater Summit

August 28-30, 2012

byby

Ronald T. Green, Ph.D. , P.G. Geosciences and Engineering Division

Southwest Research Institute®

Amount of Water Needed to Hydraulically Amount of Water Needed to Hydraulically Fracture a WellFracture a Well

�� Water demand Water demand to to frackfrack a well is substantial:a well is substantial:

�� 55--15 acre15 acre--ft (ft (1,500,0001,500,000--5,000,000 gallons5,000,000 gallons) to ) to frackfrack a boreholea borehole

�� Compared with Compared with 100,000 gallons 100,000 gallons to to drilldrill a wella well

DisposalDisposal of of FrackingFracking Waste WaterWaste Water

�� DisposalDisposal of of FrackingFracking Waste WaterWaste Water

�� Considerable amount of degraded water Considerable amount of degraded water returns to surface as returns to surface as flowbackflowback: 20% in “dry” formations, 80% in “wet” formations: 20% in “dry” formations, 80% in “wet” formations

�� Quality of Quality of flowbackflowback can be poorcan be poor: : frackingfracking additives plus highadditives plus high--salinity in salinity in situ groundwatersitu groundwater

�� Disposal Disposal of of flowbackflowback in Texas is often in Texas is often by deepby deep--well injectionwell injection

Water Quality of Concern in Flowback

FlowbackFlowback contains contains frackingfracking additivesadditives

�� Precipitated & entrained solids (scaling tendencies) Precipitated & entrained solids (scaling tendencies)

�� Ca, Mg, Ca, Mg, BaBa, , SrSr

�� Mineral scales (calcium carbonate & BaSOMineral scales (calcium carbonate & BaSO44) )

�� Iron solids (iron oxide and iron sulfide) Iron solids (iron oxide and iron sulfide)

Dispersed clay fines, colloids & silts Dispersed clay fines, colloids & silts

�� Dispersed clay fines, colloids & silts Dispersed clay fines, colloids & silts

�� High dissolved solids levels (chlorides, sulfates, calcium, etc.) High dissolved solids levels (chlorides, sulfates, calcium, etc.)

�� Bacteria Bacteria

�� Suspended solids, Suspended solids, frackfrack sand (sand (proppantproppant))

�� Liquid & gas hydrocarbons Liquid & gas hydrocarbons

�� Acid gases (COAcid gases (CO2 & H& H2S)S)

�� Friction reducer residue Friction reducer residue

plus formation (i.e., highly saline) waterplus formation (i.e., highly saline) water

An injection well has greater influence

in the direction of maximum horizontal

stress and major faults and fractures

StressStress--Field Induced Preferential FlowField Induced Preferential Flow

Injected fluids tend to follow existing fractures consistent Injected fluids tend to follow existing fractures consistent

with prewith pre--existing stress field instead of as a isotropic sphereexisting stress field instead of as a isotropic sphere

stress and major faults and fractures

Isotropic sphere

Actual volume of injection

Regulations Predicated on Isotropic Media

Disposal Well Permit Guidance (Texas)Disposal Well Permit Guidance (Texas)

�� … the applicant shall review … wells that penetrate the … the applicant shall review … wells that penetrate the

proposed disposal zone proposed disposal zone within a 1/4 mile radius of the of the

proposed disposal well to determine if all abandoned proposed disposal well to determine if all abandoned

wells have been plugged in a manner that will prevent wells have been plugged in a manner that will prevent

the movement of fluids from the disposal zone into the movement of fluids from the disposal zone into

freshwater strata.freshwater strata.

This This regulation assumes pure radial flow and does not account for heterogeneity that could result from stressthat could result from stress--

field induced directional flowfield induced directional flow

Inadvertent Contaminant Migration Inadvertent Contaminant Migration

Possible Modes of MigrationPossible Modes of Migration

1.1. Migration along fault or through confining layer Migration along fault or through confining layer –– not likely unless vertical not likely unless vertical

separation is minimalseparation is minimal

2.2. Migration via an existing borehole Migration via an existing borehole (i.e., abandoned open well) (i.e., abandoned open well) –– possible, possible,

particularly if an abandoned well is not identified, reasonably close to the particularly if an abandoned well is not identified, reasonably close to the

disposal well, and contaminant is injected into the same horizon as the disposal well, and contaminant is injected into the same horizon as the

screened section of the abandoned wellscreened section of the abandoned well

screened section of the abandoned wellscreened section of the abandoned well

Disposal well Abandoned

open wells

Usable aquifer

Confining layer

Zone of injection

Injection of disposal fluids

±

Example: Proposed Injection Well

±

0 1 2 3 40.5

Kilometers

A

±

Abandoned Oil/Gas WellsRRC Database is not Comprehensive

Proposed Disposal

Well

Well

Symbol

!A Permitted Location

D Canceled Location

R Dry Hole

!( Oil Well

#* Gas Well

") Oil/Gas Well

!. Plugged Oil Well

#0 Plugged Gas Well

"/ Plugged Oil/Gas Well

±

0 1 2 3 40.5

Kilometers

Existing Water Wells

Area of Interest

±

Stress-Field Ellipse Indicating Potential Direction of Preferential Flow

Proposed Disposal

Well

¼-mileradius

Well

Symbol

!A Permitted Location

D Canceled Location

R Dry Hole

!( Oil Well

#* Gas Well

") Oil/Gas Well

!. Plugged Oil Well

#0 Plugged Gas Well

"/ Plugged Oil/Gas Well

±

0 1 2 3 40.5

Kilometers

Existing Water Wells

Abandoned Wells

Failure of wells used for deep-well disposal of waste fluids and migration of

waste fluids through 1,000s of feet of rock are not the greatest threat

Actual Threat from Disposal Wells

are not the greatest threat

Abandoned wells pose the greatest threat in deep-well disposal of waste fluids, and

possibly hydraulic fracking

How Great is the Threat from Abandoned Wells?How Great is the Threat from Abandoned Wells?

Oil drilling began in earnest in the Oil drilling began in earnest in the early 1900searly 1900s, some , some

wells have been in existence for almost a century.wells have been in existence for almost a century.

RecordsRecords of wells, especially older wells, are often of wells, especially older wells, are often

incomplete or absentincomplete or absent..

Well casing Well casing is estimated is estimated effective for 20 yrseffective for 20 yrs, structural , structural

integrity of older abandoned wells may be compromised.integrity of older abandoned wells may be compromised.

How many? How many? Estimates vary from Estimates vary from less than 10,000 less than 10,000 to to

over over 110,000 (orphan and inactive) wells110,000 (orphan and inactive) wells. .

Is Waste Disposal by DeepIs Waste Disposal by Deep--Well Injection Well Injection a Problem?a Problem?

Disposal of degraded fluids after Disposal of degraded fluids after frackingfracking ((flowbackflowback) by ) by

12,610 disposal wells in Texas 12,610 disposal wells in Texas

RRC requires notification RRC requires notification of all occurrences of of all occurrences of breakoutbreakout, but , but

doesn’t maintain a single databasedoesn’t maintain a single database

RRC on RRC on retains records retains records on breakout for on breakout for onlyonly two yearstwo years

There are documented cases There are documented cases of breakoutof breakout

In absence of a centralized database, risk is unknown, but In absence of a centralized database, risk is unknown, but

possible possible

RecommendationsRecommendations

There are several actions the State can take to There are several actions the State can take to mitigate mitigate

the threat the threat of contamination due to “breakout” from a of contamination due to “breakout” from a

disposal well. disposal well.

�� Limit or prohibit injection of liquid wastes into oil/gas Limit or prohibit injection of liquid wastes into oil/gas (i.e., (i.e., productive) productive) formationsformations, particularly formations with a history of , particularly formations with a history of

productive) productive) formationsformations, particularly formations with a history of , particularly formations with a history of oil/gas development. oil/gas development. That’s where the abandoned wells are.That’s where the abandoned wells are.

�� Increase the ¼Increase the ¼--mile radial distance mile radial distance from proposed disposal well from proposed disposal well over which abandoned wells are searched.over which abandoned wells are searched.

�� Develop a single database Develop a single database for all occurrences of “breakout”. Risk for all occurrences of “breakout”. Risk from breakout can only be assessed if number of occurrences and from breakout can only be assessed if number of occurrences and their severity are known.their severity are known.

Contact InformationContact Information

Ronald T. Green, Ph.D., P.G.Ronald T. Green, Ph.D., P.G.

Institute ScientistInstitute Scientist

Geosciences and Engineering DivisionGeosciences and Engineering Division

Southwest Research InstituteSouthwest Research Institute

Southwest Research InstituteSouthwest Research Institute

6220 Culebra6220 Culebra

San Antonio, Texas 78238San Antonio, Texas 78238

1.210.522.5305 (office)1.210.522.5305 (office)

1.210.522.5184 (fax)1.210.522.5184 (fax)

1.210.316.9242 (cell)1.210.316.9242 (cell)

[email protected]@swri.edu

SW Segment of the Carrizo-Wilcox AquiferPrePre--Development Development PotentiometricPotentiometric SurfaceSurface

Groundwater elevation reconstructed with limited

reconstructed with limited data and historical evidence of spring flow and flowing artesian wells.

(modified from Deeds et al., 2003)

19291929--30 Carrizo30 Carrizo--Wilcox AquiferWilcox AquiferPotentiometricPotentiometric SurfaceSurface

Pumpage was estimatedat 27,000 acre-ft/yr in

at 27,000 acre-ft/yr in1929-30

Zone of depression isabout 150 ft lower thanpre-development groundwater elevation


1999 Carrizo1999 Carrizo--Wilcox AquiferWilcox AquiferPotentiometricPotentiometric SurfaceSurface

Pumpage was estimatedat 65,000-80,000

at 65,000-80,000 acre-ft/yr in 1999

Zones of depression areabout 350 ft lower thanpre-development groundwater elevation


water considerations and hydraulic fracturing, ron green

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