48 Oil & Gas Journal | May 7, 2012

EXPLORATION & DEVELOPMENT

Life cycle analysis of water

use and intensity of oil and gas

recovery in Wattenberg field, Colo.

Efficiency, particularly in the western US, is an increasingly

important priority to meet an increasing water resource demand. Even though the oil and gas industry has long been a

part of the economy in Colorado and the West, recent technological advances have stimulated growth in oil and gas

development and operations and therefore have increased

the industry’s need for water resources.

This study provides an analysis of the volume of water

required for unconventional shale gas and shale oil development and how efficiently the water is used. A general material balance is used to assess the life 

cycle of water and energy resources of

445 Noble Energy Inc. wells in Wattenberg field in northeastern Colorado.

Water use data as well as oil and gas 

production data were collected from

Noble Energy wells and separated by

well type (horizontal or vertical) and

water use (drilling and hydraulic fracturing).

Vertical and horizontal wells operated by Noble Energy in Wattenberg

during 2010 and 2011 consumed an

average of 380,000 and 2,800,000 gal

of water, respectively. On average, vertical wells used 77,000 gal to drill and 

an additional 310,000 gal to hydraulically fracture the well; whereas, horizontal wells used 130,000 gal to drill

and 2,700,000 gal for hydraulic fracturing.

A decline curve analysis was used

to estimate the ultimate recovery from

each individual well. Exponential and 

harmonic decline curves were fit to

the production data to project low and

high production scenarios, respectively.

Stephen Goodwin

Ken Carlson

Colorado State University

Fort Collins, Colo.

Caleb Douglas

Ken Knox

Noble Energy Inc.

Denver

FILTERS AND CLASSIFICATIONS USED TO DEFINE THE SAMPLE DATA SET

Colorado wells 

Operator

Field 

Completion date

Water use Well type Production

Noble Energy Inc. 

Drilling

Completion

Horizontal Vertical 

Oil Water 

Gas

FIG. 1
EXPLORATION & DEVELOPMENT

50 Oil & Gas Journal | May 7, 2012

Vertical wells are expected to have an EUR between 24

billion and 60 billion btu for oil and between 32 billion and 

84 billion btu for gas. Horizontal wells are expected to have

an EUR between 390 billion and 1,100 billion btu for gas

and between 180 billion and 520 billion btu for oil.

A ratio of the water consumed and the EUR for each well 

was used to estimate the water intensity of each well. Vertical wells have an expected water intensity ranging between 

5.4 and 14 gal/MMbtu, and horizontal wells have an expected water intensity value between 2.9 and 9.7 gal/MMbtu.

When the water intensity of shale gas extraction was

compared to other energy sources it was found to be one of

the lowest. The average horizontal well in Wattenberg field

consumed 4.3 gal/MMbtu, which is comparable with 4 gal/

MMbtu for solar photovoltaic energy. In contrast, energy produced from underground coal requires 9 gal/MMbtu, and the

amount of water consumed for energy produced from biofuels

escalates to 11,000 to 68,000 gal/MMbtu.

Horizontal wells require more water for hydraulic fracturing than vertical wells, on average. However, the water

intensity is slightly lower for horizontal wells because the 

water is used in a more efficient manner.

Introduction

Water resources in Colorado and the western US are constantly strained given the historical agricultural needs, burgeoning development, and the semiarid environment.

With continued population increases and the importance

of agriculture to the overall economy, the pressure on water

and other natural resources is expected to intensify. Even 

though the oil and gas industry has long been a part of the 

economy in Colorado and the West, recent technological advances have stimulated considerable growth in oil and gas

development and operations and therefore have increased

the industry’s need for water resources.

Competition over water resources will continue to escalate to meet expanding municipal and industrial demands,

including those associated with the oil and gas industry. In 

October 2011 the State Review of Oil and Natural Gas Environmental Regulations (STRONGER) organization issued 

a report on the Colorado hydraulic fracturing program and

the rules developed by the Colorado Oil and Gas Conservation Commission (COGCC) related to this.

1 The report,

which was generally positive, made five recommendations 

for improvement. One of the key recommendations in this 

report was regarding the availability of water:

“The review team recommends that the COGCC and the 

DWR jointly evaluate available sources of water for use in

hydraulic fracturing. Given the significant water supply issues in this arid region, this project should also include an 

evaluation of whether or not availability of water for hydraulic fracturing is an issue and, in the event that water supply

is an issue, how best to maximize water reuse and recycling

for oil and gas hydraulic fracturing.”

Other recommendations regarding the management of

water resources associated with hydraulic fracturing were

made by the Natural Gas Subcommittee of the Secretary of

Energy’s Advisory Board (SEAB) in November 2011.

2

 The

subcommittee was charged in April 2011 to study ways to

*Applied to Noble Energy oil and gas wells in Wattenberg eld, Colorado.

MATERIAL BALANCE USED TO DEFINE WATER INTENSITY ASSESSMENT*

Well Treatment

Efrac

Water treatment

Assumed that all owback

and produced water is

disposed and none is reused Assumed to be negligible Drilling Water intensity

Vdrill

Vin

Vfrac

Hydraulic

fracturing water

Values from

Noble Energy water

consumption records

Vowback

Flowback water 

Vproduced

Produced water

Etreatment

Vdisposal

Disposed water

Vout

Water reuse

Erecovered

Vinject

Injected water

Vevap

Evaporated water

Eoil Egas

Oil

recovered

Natural

gas recovered

EUR estimated using

Noble Energy production records

Edrilling

FIG. 2
EXPLORATION & DEVELOPMENT

52 Oil & Gas Journal | May 7, 2012

titled “Water Consumption of Energy

Resource Extraction, Processing, and 

Conversion.”15

Several regional studies12-14 16-18 have 

assessed water resource challenges 

with increasing demands for water.

The majority of these studies provide a 

broad estimate of water requirements,

without a detailed analysis of water

use on an individual well basis. An 

analysis of the water intensity of each

individual well provides a more detailed and accurate assessment of the 

water intensity. Other studies focus

solely on electricity generation7 10 19-25

or transportation,

26-28 the two largest

energy sectors in the US.

The project described in this report

is the first step in addressing the concerns raised and gaps in other studies.

A framework is proposed to assess the 

life cycle of water and energy resources 

of Noble Energy wells in Wattenberg 

field in northeastern Colorado. Data

from Noble Wattenberg wells are used to assess the overall

water use and average water intensity in the region as a first

application of the general framework.

The specific objectives of this project are to: (1) determine 

water use associated with Noble Energy wells in Wattenberg

field and delineate them with respect to well type (horizontal or vertical) and water use (drilling or hydraulic fracturing); and (2) determine the water intensity of each well and 

compare with other energy sources.

Methodology

Data collection

To best assess current water use and predict future water 

needs, sampled wells were limited to those completed in 

2010 and 2011 by Noble Energy in Wattenberg field.

Older wells that have been refractured to stimulate recovery were not included in the assessment of wells since this 

circumstance is not equivalent to fracturing a newly drilled

well. The issue of refracturing wells and the associated water consumption and water intensity should be included in 

future studies.

Water consumption and energy production data were collected and separated by well type and water use (Fig. 1). The

final sample includes 386 vertical wells and 59 horizontal

wells. This 445-well data set represents all of the wells in

2010 and 2011 with complete water consumption and energy production records. A total of 883 wells was drilled in 

2010 and 2011 and the remaining 438 wells were omitted for

a variety of reasons; most did not have water consumption or 

improve the safety and environmental performance of natural gas hydraulic fracturing from shale formations.

In its final report, the subcommittee stated, “At present, 

neither the Environmental Protection Agency (EPA) nor the

states are engaged in developing a systems/life cycle approach to water management.” They recommend that new

partnerships or mechanisms be developed to study the life 

cycle of water resources as one approach to protecting the 

quality of water resources in the future.

2

Gleick3 provided one of the first broad reviews of water

intensity, presenting direct, consumptive water intensity

values for each life cycle phase (i.e., mining, fuel preparation, generation, etc.) of several different fuel sources in 

1994. Sovacool and Sovacool

4

 expanded the scope of a water

intensity analysis to separate water use into both water withdrawals and consumption.

Fthenakis and Kim5 were the first to include upstream

water use in the analysis, which includes water requirements

associated with energy and material inputs to each life cycle

phase of electricity generation technologies.

In recent years, increasing concern about water and energy resources in the US has led to significantly more research

and associated reports, particularly from government agencies,6-14 most notably, a 2006 report to Congress from the

Department of Energy.6 The report was a response to a Congressional directive asking for “a report on energy and water

interdependencies, focusing on threats to national energy

production that might result from limited water supplies.”

Perhaps the most comprehensive and recent review of

water intensity comes from the Harvard Kennedy School,

5

4

3

2

1

0

0 100 200 300 400

WATER CONSUMED PER WELL, SEPARATED BY WATER USE

Vertical hydraulic fracturing water

Vertical drilling water

Horizontal hydraulic fracturing water

Horizontal drilling water

Water consumption, million gal

Noble well water consumption ranking

FIG. 3
EXPLORATION & DEVELOPMENT

54 Oil & Gas Journal | May 7, 2012

berg field. The final water consumption data set includes water consumed

and energy recovered from 386 vertical wells and 59 horizontal wells and 

categorized as either drilling water or

completion water.

Material balance

Water intensity is defined as the ratio

of water consumed and energy recovered and is used to measure how efficiently a water resource is used.

For this study, a materials and energy balance approach was used to determine the net water consumed and

net energy recovered for each well. A

schematic shows the water and energy

flows and the boundary used to define 

the water intensity (Fig. 2).

The water intensity discussed in

this article incorporates only the water consumed and energy produced.

The amount of water and energy consumed in drilling and hydraulic fracturing that is offset by flowback and

produced waters that are treated and

recycled into the production stream

warrant additional research as these

technologies are developed and applied.

It is assumed that the energy used

in drilling and hydraulic fracturing is

negligible compared with the amount

of energy recovered, and none of the

flowback or produced water is reused. 

General equations for the water intensity can be developed for the water intensity (see box with Equations 1 and

2).

Results

Water consumption

On average, each vertical and horizontal well used an average of 380,000 and 2,800,000 gal of water, respectively.

Vertical wells used an average of 77,000 gal to drill and 

an additional 310,000 gal to hydraulically fracture each well.

Horizontal wells used an average of 130,000 gal to drill and 

an additional 2,700,000 gal to hydraulically fracture each 

well.

Fig. 3 arranges each sampled well from least to greatest,

in terms of total water consumption. The bars are color coded by well type and water use. Table 1 shows the average 

water consumption of each well type and water use.

production data readily available.

Noble Energy collected water consumption values using

the patented WellView program (Peloton Computer Enterprises Ltd., Houston). WellView is part of the Peloton suite 

of software used for collecting and organizing oil field data. 

Drilling and hydraulic fracturing reports are added to WellView by a Noble Energy employee that is on site at each drilling and hydraulic fracturing site.

The water consumption totals are verified by Noble Energy’s accounting department, and any conflict of values between the field operations and the accounting department

is reconciled using the WellView program. All of the water

consumption data were accessed in November 2011.

Wells were classified as either horizontally or vertically

drilled. Directional and deviated wells are classified as vertical wells. Less horizontal well data were acquired because

the technology has only recently been adapted to WattenMEASURED WELLBORE DEPTH AS A FUNCTION OF WATER CONSUMED

Horizontal hydraulic fracturing water

Horizontal drilling water

Vertical hydraulic fracturing water

Vertical drilling water

5

4

3

2

1

0

Water consumed, million gal

6,000 7,000 8,000 9,000 10,000 11,000 12,000 13,000

Measured wellbore depth, ft 

FIG. 4

Water

intensity

Volume of

drilling water

Volume of

hydraulic

fracturing

water

Volume of

owback water

Volume of

diposed water

Volume of

produced water

Energy

from oil Energy from

natural gas

Energy used

for drilling

Energy used for

hydraulic fracturing

Energy used for

water treatment

Equation 1 is reduced to:

Water

intensity

Water

intensity

Vdrill + Vfrac

Erecovered Erecovered

V = = in

=

!

_ _

_ _ _

+

+

0 0 0

0 0 0

(2)

(1)

EQUATIONS
EXPLORATION & DEVELOPMENT

56 Oil & Gas Journal | May 7, 2012

A wide range of EURs is presented because the long-term

performance of unconventional oil and gas wells is not well

understood and less than 2 years of data are used for the decline curve analysis. As recovery rates are better understood

and additional production data is available, the EUR values 

can be estimated with more precision.

Water intensity

Horizontal wells are estimated to have a water intensity value between 2.9 and 9.7 gal/MMbtu, and vertical wells are

estimated to have a water intensity value between 5.4 and 14

gal/MMbtu (Table 4).

Despite much lower water requirements for vertical wells, 

horizontal wells have lower water intensity requirements for

all energy production scenarios. These results indicate that

horizontal drilling and hydraulic fracturing is a more efficient approach for oil and gas extraction than older methods

have been.

When the water intensity associated with recovery is

compared with other energy sources, unconventional oil

and gas recovery in Wattenberg field is found to be comparable with solar energy (Table 5).

Although only a simplified version of the material balance

framework presented in this study was applied in this study,

it can be used to assess recycling and reuse of flowback and 

produced water and the energy requirements of these processes.

The degree of treatment of flowback and produced water

will determine the amount of water available for reuse, additional energy requirements for treatment, and best practices for life cycle water management and disposal. Also, the 

material balance of an entire region can be assessed for the

complete life cycle of the wells to quantitatively determine 

the long-term impact on water resources.

Summary

Vertical and horizontal wells operated 

by Noble Energy in Wattenberg during

2010 and 2011 consumed an average

380,000 and 2,800,000 gal of water.

Despite the much higher quantities of water used for horizontal wells, 

the efficiency of this energy extraction

practice was found to be greater than

with vertical drilling and hydraulic

fracturing.

Vertical and horizontal wells operated by Noble Energy in Wattenberg

during 2010 and 2011 were determined to have an expected average water intensity of 6.9 and 4.3 gal/MMbtu,

respectively. Vertical wells have an expected water intensity ranging between

5.4 and 14 gal/MMbtu, and horizontal

Water consumption values of horizontal wells are significantly more than water consumption values of vertical wells.

The increased drilling distance of horizontal wells and an

increased number of hydraulic fracturing stages contribute 

to the increased water requirements.

A subset of wells was chosen to determine if a correlation between the 

measured wellbore depth and water

uses (e.g., drilling water consumption

or hydraulic fracturing water consumption) exists. No clear correlation

was found (Fig. 4).

Ultimate energy recovery

Vertical wells are estimated to have an

ultimate recovery between 56 billion

and 150 billion btu with approximately 60% of the energy from gas, and

horizontal wells are estimated to have 

an ultimate recovery between 570 billion and 1,600 billion btu with 70% of

the energy from gas.

Tables 2 and 3 show the energy

recovery for each well type, energy

source, and recovery scenario.

AVERAGE WATER CONSUMPTION Table 1

Drilling Hydraulic frac. Total

––––––––––––– Water, 1,000 gal –––––––––––––

Horizontal well 130 2,700 2,800

Vertical well 77 310 380

ESTIMATED ULTIMATE RECOVERY

FOR VERTICAL WELLS

Table 2

Low Average High

–––––––– Production scenario, billion btu –––––––––

Oil 24 42 60

Gas 32 62 84 ––– –––– –––– Total 56 100 150

WATER INTENSITY ESTIMATES Table 4

Low Average High

–––––––– Production scenario, gal/MMbtu ––––––––

Horizontal 9.7 4.3 2.9

Vertical 14 6.9 5.4

ESTIMATED ULTIMATE RECOVERY

FOR HORIZONTAL WELLS

Table 3

Low Average High

–––––––– Production scenario, billion btu –––––––––

Oil 180 350 520

Gas 390 740 1,100 –––– ––––– ––––– Total 570 1,100 1,600

WATER INTENSITY OF

DIFFERENT ENERGY SOURCES

Table 5

–––– Gal/MMbtu –––

Coal

Surface mining 2 (3, 5)

Underground mining 9 (3, 5)

Natural gas

 Conventional 0 (6)

Noble Energy data

 Vertical 6.9

 Horizontal 4.3

Oil

 Primary 1.5 (3)

Oil shale 5.5 (15)

Conventional  ooding 14 (6)

Oil sand 35 (3)

Enhanced recovery 62 (15)

Solar

 Photovoltaic 4 (5)

Wind

 Turbine 0 (5)

Biofuels

Ethanol from

 irrigated corn 11,000 (8)

Biodiesel from soy 60,000 (15)

Biodiesel from

 rapeseed 68,000 (15)
EXPLORATION & DEVELOPMENT

58 Oil & Gas Journal | May 7, 2012

freshwater needs to meet future thermoelectric generation requirements: 2009 update,” technical report 400/2009/1339,

NETL, US DOE, September 2009.

11. National Energy Technology Laboratory, “Emerging

issues for fossil energy and water,” technical report, NETL,

US DOE, 2006.

12. Government Accountability Office, “Energy-water

nexus: Improvements to federal water use data would increase understanding of trends in power plant water use,” 

technical report, US GAO, 2009.

13. Colorado Water Conservation Board, “State of Colorado 2050 municipal and industrial water use projections,”

technical report, CWCB, Camp Dresser and McKee Inc.,

Harvey Economics, July 2010.

14. Colorado River Basin Roundtable and Yampa/White

River Basin Roundtable, “Energy development water needs

assessment phase ii,” technical report, Colorado Water Conservation Board, February 2011.

15. Mielke, Erick, Anadon, Laura Diaz, and Narayanamurti, Venkatesh, “Water consumption of energy resource

extraction, processing, and conversion,” Discussion Paper

2010-15, Harvard Kennedy School Belfer Center for Science

and International Affairs, Cambridge, Mass., October 2010.

16. Fisher, Jeremy, and Ackerman, Frank, “The water-energy nexus in the western US: Projections to 2100,” technical

report, Stockholm Environment Institute, February 2011.

17. CDM Inc., “Colorado’s water supply future: State water supply initiative 2010,” technical report, Colorado Water

Conservation Board, January 2011.

18. Stacy Tellinghuisen, “Water conservation = energy

conservation,” a report for the CWCB, Western Resource 

Advocates, June 2009.

19. Domenichini, Rosa, Arienti, Silvio, Cotone, Paolo,

and Santos, Stanley, “Evaluation and analysis of water usage

and loss of power in plants with CO2 capture,” Energy Procedia, Vol. 4, 2011, pp. 1,925-32.

20. Gerdes, Kristin, and Nichols, Christopher, “Water requirements for existing and emerging thermoelectric plant

technologies,” technical report DOE/NETL-402/080108, 

National Energy Technology Laboratory, April 2009.

21. Hightower, Mike, “Energy and water: Issues, trends,

and challenges,” EPRI workshop, Sandia National Laboratories, July 2008.

22. Inhaber, Herbert, “Water use in renewable and conventional electricity production,” Energy Sources, Vol. 26,

2004, pp. 309-22.

23. Larson, Dana, Lee, Cheryl, Tellinghuisen, Stacy, and 

Keller, Arturo, “California’s energy-water nexus: Water use

in electricity generation,” Southwest Hydrology, September/

October 2007, pp. 20-30.

24. Stillwell, Ashlynn S., King, Carey, W., Webber, Michael E., Duncan, Ian J., and Hardberger, Amy, “The energywater nexus in Texas,” Ecology and Society, Vol. 16, No. 1,

2011.

wells have an expected water intensity value between 2.9

and 9.7 gal/MMbtu. 

The water intensity of these oil and gas extraction techniques when compared with other energy sources was found 

to be one of the lowest.

The average Noble Energy horizontal well in Wattenberg

field retains a water intensity of 4.3 gal/MMbtu, which is 

comparative with photovoltaic solar energy at 4 gal/MMbtu.

Only wind (0 gal/MMbtu) and primary oil recovery (1.5 gal/

MMbtu) are significantly lower. In contrast, the water intensity for energy produced from underground coal is 9 gal/

MMbtu and escalates to 16,000 to 45,000 gal/MMbtu for

energy produced by biofuels.

Acknowledgments

The project was funded by the Colorado Energy Water Consortium (http//cewc.colostate.edu). 

References

1. STRONGER, “Colorado hydraulic fracturing state review, technical report,” STRONGER: State Review of Oil and 

Natural Gas Environmental Regulations, October 2011.

2. SAEB, “Shale gas production subcommittee second 

90-day report,” technical report, US Department of Energy, 

November 2011.

3. Gleick, Peter H., “Water and energy,” Annual Review

of Energy and the Environment, Vol. 19, No. 1, 1994, pp. 

267-99.

4. Sovacool, Benjamin K., and Sovacool, Kelly E., “Preventing national electricity-water crisis areas in the US,”

technical report, Energy Governance Program at the Centre 

on Asia and Globalization, Lee Kuan Yew School of Public

Policy at the National University of Singapore, 2009. 

5. Fthenakis, Vasilis, and Kim, Hyung Chul, “Life-cycle

uses of water in US electricity generation,” Renewable and

Sustainable Energy Reviews, Vol. 14, No. 7, 2010, pp. 2,039-

48.

6. US Department of Energy, “Energy demands on water resources,” technical report, US Department of Energy, 

2006.

7. US Department of Energy, “Estimating freshwater

needs to meet future thermoelectric generation requirements,” Technical Report 400/2008/1339, DOE and National Energy Technology Laboratory, September 2008.

8. US Department of Energy, “State oil and natural gas

regulations designed to protect water resources,” technical

report, US DOE, Office of Fossil Energy, National Energy

Technology Laboratory, May 2009.

9. Clark, C.E., and Veil, J.A., “Produced water volumes

and management practices in the US,” technical report, Argonne National Laboratory prepared for US DOE, Office of

Fossil Energy, National Energy Technology Laboratory, September 2009.

10. National Energy Technology Laboratory, “Estimating
Oil & Gas Journal | May 7, 2012 59

EXPLORATION & DEVELOPMENT

the Colorado Energy Water Consortium (http://cewc.colostate.

edu). He has a BS in chemical engineering from the University

of Wisconsin-Madison, MS in environmental engineering from

CSU, and a PhD in environmental engineering from the University of Colorado-Boulder.

Caleb Douglas is an environmental engineer at Noble Energy

Inc. specializing in water management. He has BS and MS

degrees in environmental engineering from CSU.

Ken Knox is a senior advisor for Noble Energy and is responsible for strategic planning and management of the company’s

comprehensive full life cycle water program. He has a BS in

chemical engineering and MS and PhD degrees in civil engineering, all from CSU.

25. Yang, Xiaoying, and Dziegielewski, Benedykt, “Water

use by thermoelectric power plants in the US,” Journal of

American Water Resources Association, Vol. 43, No. 1, February 2007, pp. 160-69.

The authors

Stephen Goodwin is a PhD candidate in the 

Civil and Environmental Engineering department 

at Colorado State University. He has a BS in 

mechanical engineering from the University of 

Colorado at Boulder and an MS in environmental

engineering from CSU.

Ken Carlson (kcarlson@engr.colostate.edu) is an associate

professor in Civil and Environmental Engineering at Colorado 

State University and cofounder with Noble Energy authors of

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