Journal of Water Resource and Protection, 2013, 5, 1262-1267
Published Online December 2013 (http://www.scirp.org/journal/jwarp)
http://dx.doi.org/10.4236/jwarp.2013.512135
Open Access JWARP
Improved Water Use Estimates for Drilling and Hydrualic
Fracturing in Northeastern Colorado
Stephen Goodwin1*, Ken Carlson1, Bing Bai1, Luke Rein1, Ken Knox2, Caleb Douglas2
1Department of Civil and Environmental Engineering, Colorado State University, Fort Collins, USA
2Noble Energy, Inc., Environmental Engineering: Denver Office, Denver, USA
Received September 21, 2013; revised October 25, 2013; accepted November 23, 2013
Copyright © 2013 Stephen Goodwin et al. This is an open access article distributed under the Creative Commons Attribution License,
which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.
ABSTRACT
The development of unconventional resources in tight shales has stimulated considerable growth of oil and gas produc-
tion in Northeastern Colorado, but has led to concerns about added demands on the region’s strained water resources.
Northeastern Colorado’s semi-arid environment, population growth, competing water demands and uncertainty about
drilling and hydraulic fracturing water requirements have resulted in scrutiny and conflict surrounding water use for
tight shales. This study collects water use data from wells in Northeastern Colorado to improve water estimates and to
better understand important contributing factors. Most water resource studies use estimates for the number of future
wells to predict water demands. This study shows that the number of hydraulic fracturing stages is a better measure of
the future water demands for horizontal wells. Vertical wells use significantly less water than horizontal wells and will
be less prevalent in the future.
Keywords: Hydraulic Fracturing; Shale; Wattenberg; Niobrara; Water; Energy
1. Introduction
Water resources in Northeastern Colorado and the west-
ern United States are constantly strained given the his-
torical agricultural needs, burgeoning development, and
the semi-arid environment. With continued population
growth and the importance of agriculture, the pressure on
water resources in the region is expected to intensify. The
oil and gas industry has long been a part of Northeastern
Colorado’s economy, but recent advances in technology
have stimulated considerable growth in the region that
has increased the industry’s demand for water resources.
Several studies have assessed water resource demands
in Northeastern Colorado [1-6]. All of these studies base
the total water demands on the number of wells. Typi-
cally the water required to drill and hydraulically fracture
a well is estimated to be between one and five million
gallons per well [7,8]. These general estimates of water
use have led to increased uncertainty and conflict sur-
rounding water development for the oil and gas industry
in Northeastern Colorado.
As competition over water resources between agricul-
tural, recreational, municipal, and industrial demands,
including oil and gas operations continues to escalate, it
is important to understand more precisely the demands for
the oil and gas industry will place on water resources. Se-
veral organizations have voiced concerns about a lack of
water use data to assess impacts on water resources. In
October, 2011 the State Review of Oil and Natural Gas
Environmental Regulations (STRONGER) organization
issued a report on rules developed by the Colorado Oil
and Gas Conservation Commission (COGCC) related to
hydraulic fracturing. One of the five recommendations of
the report included the following:
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 sup-
ply 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 water supply is an issue, how best to maximize wa-
ter reuse and recycling for oil and gas hydraulic fractur-
ing.
The Natural Gas Subcommittee of the Secretary of
Energy’s Advisory Board (SEAB) made other recom-
mendations regarding the management of water resourc-
es associated with hydraulic fracturing in November
*Corresponding author.

S. GOODWIN ET AL. 1263
2011 [9]. The subcommittee was charged in April 2011 to
study ways to improve the safety and environmental per-
formance hydraulic fracturing from natural gas shale for-
mations. In its final report, the subcommittee stated “At
present neither EPA nor the states are engaged in devel-
oping a system/lifecycle approach to water management.”
They recommended that new partnerships or mechanisms
be developed to study the lifecycle of water resources as
one approach to protect the quality of water resources in
the future.
This study addresses these concerns by examining the
water use of individual wells to provide governing agen-
cies, industries, and the greater public empirical data to
make informed decisions regarding future water and en-
ergy development. The objective of this study is to pro-
vide a detailed assessment of current water use and to
determine the factors that have the strongest influence on
the total water use per well. These factors include the
well type (vertical, horizontal, or extended horizontal),
number of hydraulic fracturing stages, water use (drilling
or hydraulic fracturing), temporal, and spatial distribu-
tion.
Traditional quantification of water use based upon the
number of energy wells developed is misleading and no
longer practical. An accurate and applicable measure of
accurate water development is the number of stages used
in completion of an energy well, commonly referred to as
hydraulic fracturing. This investigation illustrates the va-
lue and importance of applying this new metric in water
resources management for energy development.
2. Method
The wells included in the water use analysis are limited
to wells located in the Wattenberg field located in North-
eastern Colorado, drilled between January 1, 2010 and
July 1, 2013, and operated by Noble Energy, Inc. (Noble)
with complete water use records available. For this study,
the Wattenberg field is defined by the Colorado Oil Gas
Conservation Commission’s (COGCC) GIS shape file
accessed on July 1, 2013 (Figure 1). To best assess cur-
rent water requirements and predict future demands only
wells drilled after 2010 are included in the study. Noble
is the largest operator in the Wattenberg field.
A total of 1220 wells are included (Tabl e 1) and cate-
gorized using: 1) drilling water consumed; 2) hydraulic
water consumed; 3) total water consumed; 4) well type
(vertical, horizontal, or extended horizontal); 5) hydrau-
lic fracturing stages or distance; 6) hydraulic fracturing
fluid; 7) well coordinates; 8) year; and 9) target forma-
tion, if available.
Water use is categorized as either drilling or hydraulic
fracturing water. Water used to drill the well, prepare the
borehole, and set the casings is defined as drilling water.
Water used to fracture the shale, carry the proppant used
Table 1. The count of sampled wells separated by year and
well type.
Vertical Horizontal Extended Horizontal
2010 181 6 0
2011 408 65 2
2012 227 182 6
2013 5 117 21
Total 821 370 29
Figure 1. The spatial distribution of sampled wells used in
this study. Sampled vertical wells are shown in green, sam-
pled horizontal wells are shown in blue, and extended hori-
zontal wells are shown in red. The Wattenberg field as de-
fined by the COGCC on July 1, 2013 is shown in tan.
to maintain fracture geometry, and flush the well is de-
fined as hydraulic fracturing water.
Drilling and hydraulic fracturing water consumption
records for each well are collected using Noble Energy’s
WellView software [10] and separated by year. WellView
is part of the Peloton suite of software used for collecting
and organizing oil field data. A Noble employee adds
drilling and hydraulic fracturing reports to WellView that
is on-location at each drilling and hydraulic fracturing
site. Noble Energy’s accounting department verifies the
water consumption totals and any conflicts are reconciled
in WellView. The water use data was downloaded from
Noble Energy’s WellView software on July 1, 2013. The
drilling and hydraulic fracturing water use are summed,
if both are available, to estimate the total water con-
sumed.
Open Access JWARP

S. GOODWIN ET AL.
1264
Wells are separated by type (vertical, horizontal, or
extended horizontal) using Noble’s well naming system
or the number of hydraulic fracturing stages, if available.
Directional and deviated wells are categorized as vertical
wells for this study because of similar water require-
ments. Horizontal wells are separated from extended ho-
rizontal wells by Noble’s well naming system or the
number of hydraulic fracturing stages used when avail-
able. A horizontal well will typically be hydraulically
fractured in 20 stages. Recently, Noble has drilled and
hydraulically fractured longer horizontal wells that can
include over 40 stages to hydraulically fracture. Hori-
zontal wells that require over 25 hydraulic fracturing
stages are defined as extended horizontal wells in this
study.
The type of hydraulic fracturing fluid used and the
number of hydraulic fracturing stages per well are col-
lected from Noble Energy’s WellView software. The well
coordinates, year, and target formation are all collected
COGCC’s online facilities database.
An Anderson-Darling test [11] is used to test the nor-
mality of each subset of data. The difference between
water use for each subset of data is tested using a non-
parametric Kruskal-Wallis test. A Dunn-Šidák post-hoc
comparison [12] is used to compare any differences be-
tween samples that are found using the Kruskal-Wallis
test. A 95% confidence interval is used throughout the
analysis. The number of hydraulic fracturing stages is
correlated using a simple linear regression. A coefficient
of determination is used to measure how well the regres-
sion correlates the hydraulic fracturing water use and the
number of stages. Spatial autocorrelations are measured
with ArcGIS Spatial Analyst tool [13] using Moran’s I
with inverse distance weighting and a 95% confidence
interval.
1220 wells have both drilling and hydraulic fracturing
water and are included in the study. Wells that are drilled
but not hydraulically fractured (260 sampled wells) are
typically conventional wells recovering from an oil and
gas trap. Wells that are hydraulically fractured but not
drilled (25 sampled wells) are typically existing wells
that are reworked or restimulated using hydraulic frac-
turing.
3. Results
A Kruskal-Wallis test reveals there is a significant dif-
ference between the median total water use for vertical,
horizontal, and extended horizontal wells (χ2(2) = 622, p
< 0.05). Dunn-Šidák post-hoc comparisons of the total
water for the three well groups indicates that vertical
wells (Mdn = 360,000) use significantly less total water
than either horizontal (Mdn = 2,871,000) or extended
horizontal wells (Mdn = 5,620,000), as shown in Figure
2 and Table 2. Vertical wells also use significantly
Table 2. Descriptive statistics for total water use separated
by well type.
Total (Million Gallons)Vertical Horizontal Extended Horizontal
Q1 332,900 2,600,000 3,721,000
Q2 360,000 2,871,000 5,620,000
Q3 461,900 3,108,000 6,830,000
IQR 129,000 510,100 3,109,000
Skewness 9.1 4.6 −0.44
Kurtosis 99 54 −1.3
Figure 2. A histogram of the distribution of drilling and hy-
draulic fracturing water use for vertical, horizontal, and
extended horizontal wells. Vertical we lls are shown in green,
horizontal wells are shown in blue, and extende d horizontal
wells are show n in red.
less water than horizontal wells.
The total water use for each well type does not show
significant temporal (Figure 3) or spatial variation (Fig-
ure 4) within the Wattenberg field. Only vertical wells
show any significant spatial autocorrelation (I = 0.66, p <
0.05). The significant clusters for vertical wells appear to
be randomly distributed throughout the Wattenberg field
and do not present an obvious trend in water use spatially.
Horizontal (I = 0.53, p = 0.60) and extended horizontal (I
= −0.082, p = 0.70) wells do not show any significant
spatial autocorrelation.
The type of hydraulic fracturing fluid used signifi-
cantly influences vertical wells. The normalized hydrau-
lic fracturing water use is significantly less for gelled
fractures (Mdn = 544 gallons per foot) than slickwater
fractures (Mdn = 1340 gallons per foot) for vertical wells
(χ2(1) = 42.4, p < 0.05). Horizontal wells do not have
enough slickwater data to compare gelled and slickwater
hydraulic fracturing water use.
The majority of the water used for each well is used
for hydraulic fracturing. Vertical wells use a median of
81% (Q1 = 77%, Q3 = 85%) of the total water for hy-
draulic fracturing. Horizontal and extended horizontal
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S. GOODWIN ET AL. 1265
Figure 3. The water use for vertical wells and horizontal
wells separated by year. The 25th and 75th percentiles are
represented with a blue box, the 50th percentile is repre-
sented with a red line, the 10th and 90th percentiles are
represented with black lines, and the outliers are repre-
sented with red plus signs.
Figure 4. The total water use is separated into quartiles
with the lightest shade representing the first quartile (least
water use) of the total water use and the darkest shade rep-
resenting the fourth quartile (most water use). Vertical
wells are shown in blue, horizontal wells are shown in green,
and extended horizontal wells are show n in red.
wells use a median value of 96% (Q1 = 95%, Q3 = 97%)
and 97% (Q1 = 97%, Q3 = 98%) for hydraulic fracturing,
respectively, as shown in Table 3.
There is a significant difference between the median
drilling water use across the three well types (χ2(2) =
387.24, p < 0.05). Vertical wells use significantly less
total water than either horizontal or extended horizontal
wells and horizontal wells use significantly less water
than extended horizontal wells (Figure 5). Vertical wells
use the least water (Mdn = 74,760) followed by horizon-
tal wells (Mdn = 116,300), and extended horizontal wells
(Mdn = 180,800).
There is also a significant difference between the me-
dian hydraulic fracturing water use across the three well
types (χ2(2) = 619.71, p < 0.05). Vertical wells use sig-
nificantly less hydraulic fracturing water than either hori-
zontal or extended horizontal wells and there is not a sig-
nificant difference between the total water use between
horizontal and extended horizontal wells. Vertical wells
use the least water (Mdn = 278,900) followed by hori-
zontal wells (Mdn = 2,792,000), and extended horizontal
wells (Mdn = 6,517,000).
The total water use for horizontal and extended hori-
zontal wells correlates (r2 = 0.64) with the number of
stages used to hydraulically fracture each well (Figure 6).
Wells defined as horizontal wells (less than 25 stages) are
shown in blue region and the wells defined as extended
horizontal wells are shown in the red region. A linear
regression using a least-square linear fit is also shown.
When the total water use is normalized by the number
of hydraulic fracturing stages, the water use for horizon-
tal and extended horizontal is not statistically different
(χ2(1) = 2.85, p < 0.05). The distribution is also similar
for horizontal and extended horizontal wells (Figure 7).
Vertical wells do not show any correlation between the
total water use (r2 = 0.081) or hydraulic fracturing water
use (r2 = 0.073).
4. Discussion
The most important factors with estimating the total wa-
ter use for a well are the well type and the number of
hydraulic fracturing stages. Vertical wells use signifi-
cantly less water than horizontal wells. The water total
water use for vertical wells remains relatively constant.
However, the total water use for horizontal wells can
vary from a few hundred thousand gallons up to nearly
eight million gallons per well. Accounting for the number
of hydraulic fracturing stages used can reduce the vari-
ability in the total water use for horizontal wells. The ma-
jority of the total water use per well is used for hydraulic
fracturing. When the number of hydraulic fracturing stag-
es normalizes the total water use, the water use is similar
for all of the horizontal wells.
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Table 3. Descriptive statistics for drilling and hydraulic
fracturing water use separated by well type.
Drilling
(Million Gallons) Vertical Horizontal
Extended
Horizontal
Q1 62,160 94,660 121,400
Q2 74,760 116,200 149,900
Q3 89,040 140,700 184,000
IQR 26,880 46,080 62,580
Skewness 12 3.1 −0.085
Kurtosis 240 25 0.8
Hydrualic
Fracturing Vertical Horizontal
Extended
Horizontal
Q1 269,400 2,483,000 3,593,000
Q2 278,900 2,753,000 5,458,000
Q3 395,000 2,995,000 6,803,000
IQR 125,700 512,300 3,210,000
Skewness 9.2 2.9 −0.39
Kurtosis 100 20 −1.5
Figure 5. The distribution of drilling and hydraulic frac-
turing water use for vertic al, horizontal, and extended hori -
zontal wells. The 25th and 75th percentiles are represented
with a blue box, the 50th percentile is represented with a
red line, the 10th and 90th percentiles are represented with
black lines, and the outliers are represented with red plus
signs.
The median total water use per well has remained con-
stant or decreased slightly since 2010 for both vertical
and horizontal wells. As drilling and hydraulic fracturing
technology improves, the water use per well may con-
tinue to decrease slightly or remain constant. However,
the number of wells in the Wattenberg field has been
increasing from 2010 to 2013 and is very likely continue
Figure 6. A simple linear regression between the number of
hydraulic fracturing stages and the volume of hydraulic
fracturing water used. Horizontal wells (less than 25 stages)
are shown in the blue region and extended horizontal wells
are shown in the red region.
Figure 7. The distribution of the total water use for horizon-
tal and extended horizontal water use normalized to the num-
ber of hydraulic fracturing stages.
to increase. The water use does not show any strong spa-
tial correlation within the field. The same water demand
predictions can be made throughout the Wattenberg.
Flowback or produced water estimates for each well
were not included in this study. As water treatment and
reuse becomes more prevalent in the Wattenberg field,
the net water use should also be considered when esti-
mating demands on water resources. Produced water vo-
lumes may show significant temporal and spatial varia-
tion and further complicate water demand predictions.
The volume of oil and gas recovered for each gallon of
water used should also be considered. This measure of
water intensity is important to determine how efficiently
water is being used and to compare different well types
and sizes. The efficiency of additional factors beyond
water quantity, such as community impacts, air and water
quality, land disturbances, should be considered.
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5. Conclusion
Estimates of the total water use and demands on water
resources can be dramatically improved by taking the
well type and number of hydraulic fracturing stages into
consideration. Spatial and temporal variations do not
have a strong influence on the water use for the different
well types. As horizontal wells become more prevalent in
the future, water demand predictions should be based on
the number of hydraulic fracturing stages rather than the
number of wells. The number of hydraulic fracturing
stages can range from three to 45 and the total water use
can vary from a few hundred thousand gallons up to
nearly eight million gallons per well. It is a mistake to
simply assume that all of the wells use a specific volume
of water, particularly as the lateral lengths of horizontal
wells are becoming longer to minimize surface impacts
and maximize hydrocarbon recovery.
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