Prepared in cooperation with the 

Massachusetts Department of Environmental Protection and the 

Massachusetts Department of Environmental Management 

Borehole characterization of a methane-yielding 

bedrock well, Tyngsborough, Massachusetts 

By Herbert A. Pierce, Gregory J. Walsh, Robert C. Burruss, and James R. Degnan 

Open-File Report 2007-1399

U.S. Department of the Interior 

U.S. Geological Survey
ii

U.S. Department of the Interior 

DIRK KEMPTHORNE, Secretary 

U.S. Geological Survey 

Mark D. Myers, Director 

U.S. Geological Survey, Reston, Virginia 2007 

Revised and reprinted: 2007 

For product and ordering information: 

World Wide Web: http://www.usgs.gov/pubprod 

Telephone: 1-888-ASK-USGS 

For more information on the USGS—the Federal source for science about the Earth, 

its natural and living resources, natural hazards, and the environment: 

World Wide Web: http://www.usgs.gov 

Telephone: 1-888-ASK-USGS 

Cover Photograph: The Tyngsborough Fire Department responds to a burning drill rig operated by 

Skillings and Sons, Inc. after an explosive methane release in August 2004. Photograph provided by 

Joseph Cerutti, Massachusetts Department of Environmental Protection. 

Suggested citation: 

Pierce, H.A., Walsh, G.J., Burruss, R.C., and Degnan, J.R., 2007, Borehole characterization of a methaneyielding bedrock well, Tyngsborough, Massachusetts: U.S. Geological Survey Open-File Report 2007-

1399, http://pubs.usgs.gov/of/2007/of2007-1399. 

Any use of trade, product, or firm names is for descriptive purposes only and does not imply endorsement 

by the U.S. Government. Although this report is in the public domain, permission must be secured from the 

individual copyright owners to reproduce any copyrighted material contained within this report. 
iii

Contents 

Contents.........................................................................................................................................................iii 

Introduction ....................................................................................................................................................1 

Borehole Characterization..............................................................................................................................1 

 Outcrop Characterization ............................................................................................................................3 

Dissolved Gas Analysis..................................................................................................................................4 

Acknowledgments ..........................................................................................................................................5 

References Cited.............................................................................................................................................5 

Figures ............................................................................................................................................................7 

Tables ...........................................................................................................................................................12 

Figures 

Figure 1. Location map showing the bedrock well, nearby outcrops, and a cross section (A-A’) 

through the well from Scribner Road to Westford Road....................................................................7 

Figure 2. Plot of fracture locations and type by depth in the borehole....................................................8 

Figure 3. Plot of geophysical properties measured in the Skyline Drive well ........................................9 

Figure 4. Lower hemisphere equal area projection showing the orientation and type of fractures at the 

Alpine Way roadcut, and photograph of the roadcut. ......................................................................10 

Figure 5. Lower hemisphere equal area projections of measured structures observed in the borehole.10 

Figure 6. Photograph of Isotech Isobag showing in-situ sample from the bottom of the well with 

exsolved gas bubbles ........................................................................................................................11 

Figure 7. Hydrocarbon molecular composition versus the carbon isotopic composition of methane for 

gases in table 2 showing the fields for gases of microbial origin and petroleum gases from 

thermogenic cracking of sedimentary organic matter ......................................................................12 

Tables 

Table 1. Water level measurements made by water level probe in the Skyline Drive well, 

Tyngsborough, Massachusetts 

Table 2. Molecular and isotopic compositions of gases in groundwater from wells in crystalline 

basement rocks, Massachusetts 
iv

Conversion Factors 

Inch/Pound to SI 

Multiply By To obtain 

Length 

inch (in.) 2.54 centimeter (cm) 

inch (in.) 25.4 millimeter (mm) 

foot (ft) 0.3048 meter (m) 

mile (mi) 1.609 kilometer (km) 

mile, nautical (nmi) 1.852 kilometer (km) 

yard (yd) 0.9144 meter (m) 

Temperature in degrees Celsius (°C) may be converted to degrees Fahrenheit (°F) as follows: 

°F=(1.8×°C)+32 

Temperature in degrees Fahrenheit (°F) may be converted to degrees Celsius (°C) as follows: 

°C=(°F-32)/1.8 

Vertical coordinate information is referenced to the insert datum name (and abbreviation) here, for instance, “North American 

Vertical Datum of 1988 (NAVD 88)” 

Horizontal coordinate information is referenced to the insert datum name (and abbreviation) here, for instance, “North 

American Datum of 1983 (NAD 83)” 

Altitude, as used in this report, refers to distance above the vertical datum. 

Specific conductance is given in microsiemens per centimeter at 25 degrees Celsius (μS/cm at 25°C). 

Concentrations of chemical constituents in water are given either in milligrams per liter (mg/L) or micrograms per liter (μg/L).
Borehole Characterization of a Methane-Yielding 

Bedrock Well, Tyngsborough, Massachusetts 

By Herbert A. Pierce, 1 Gregory J. Walsh, 2 Robert C. Burruss, 1 and James R. Degnan3

Introduction 

In August 2004, a domestic water well was drilled into granitoid metamorphic rocks 5.38 

kilometers southwest of Tyngsborough, Massachusetts on Scribner Hill (fig. 1). According to 

well driller Roger Skillings of Skillings and Sons, Inc. (oral commun., 2005), no water was 

encountered during drilling and when the borehole reached a depth of approximately 305.1 m, a 

blue flame exploded out of the well casing and ignited the drill rig, resulting in a total loss of the 

equipment (cover). Follow up water quality studies by the Massachusetts Department of 

Environmental Protection (Stephen Hallem, oral commun., 2006) detected low levels of methane 

in the groundwater extracted from the well. Discussions with the Stephen Hallem, Massachusetts 

Departments of Environmental Protection and David Wunsch, the New Hampshire State 

Geologist, prompted the USGS to further investigate this methane occurrence in granitoid rock. 

Borehole characterization and water quality sampling reported here were completed in May and 

June 2006, in an effort to identify the potential source of the methane. Follow up samples yielded 

no detectable methane, and for that reason this report presents a brief summary of our 

preliminary findings. 

Our findings show that the well has many fractures but none clearly discernible at the 

bottom of the well (305.1 m). The deepest observable fracture occurs near the bottom of the well 

at a depth of 294 m. The original methane was probably stored in this deep fracture or an 

unobservable fracture at the very bottom of the well (305.1 m), and released during drilling. We 

can only speculate about the initiation of the explosion. Perhaps a spark was generated by static 

electricity as the gas escaped or by the dry drill bit—rock interaction producing a piezoelectric 

effect caused by the applied mechanical stress of drilling. Microbial action may be responsible 

for depleting the methane in the well to limits below detection. 

Borehole Characterization 

In May and June 2005, borehole characterization of the well was completed with the 

following instruments: 

• Three arm caliper (with natural gamma) 

• Induction (rock resistivity and conductivity with natural gamma) 

• Electrical log (Fluid conductance, resistivity, and temperature) 

 

1

 USGS, Reston, Virginia 

2

 USGS, Montpelier, Vermont 

3

 USGS, Pembroke, New Hampshire 

1
• Optical Televiewer (oriented) 

• 1 liter down hole water sampler 

Results of the borehole characterization logs are included in this report in WellCAD log (WCL) 

format. The logs are located on the DVD in the file, Tyngsborough.WCL, that accompanies this 

text. The WellCAD Reader software is provided on the DVD and must be installed in order to 

view, scale, and print the logs. Use file wcad.reader.4.2.exe to install the WellCAD Reader. For 

additional information on WellCAD, please visit: 

http://www.rockware.com/catalog/pages/wellcad.html or http://www.alt.lu 

A summary of the borehole findings includes 

• The borehole is drilled through granodiorite, pegmatite, foliated granite, and 

metasedimentary rocks of the Silurian and Ordovician Devens-Long Pond facies of the 

Ayer Granite and the Silurian and Ordovician Berwick Formation (fig. 1) (Zen, 1983). 

• During the time of logging, the water table ranged from approximately 39 to 46 m below 

ground surface (table 1). 

• The borehole diameter is stepped but generally uniform, smooth, and 305.1 m deep (fig. 

3). 

• Gently to moderately dipping fractures occur throughout the borehole in the igneous 

rocks, but are not apparent in the Berwick Formation. 

• Fractures that cross the foliation “crossing fractures” are more common than fractures 

along the foliation “parting fractures”; (fig. 2 and the borehole log). 

• The deepest measurable fracture occurs at a depth of 294.4 m. The fracture is 

approximately parallel to the foliation (parting), and occurs at the top of a thin (20 cm 

thick) zone with a relatively higher concentration of leucocratic material (granite or 

pegmatite). Highly reflective minerals interpreted as pyrite are present in this zone. 

• No distinct fractures were detected at the bottom of the well. At the bottom, the caliper 

log indicates that the borehole is cylindrical and measures 14.47 cm in diameter. 

• Rock types in the borehole appear to be the same as rock types at nearby outcrops. The 

main rock type is granodiorite of the Ayer Granite. 

The nature of borehole logs is such that normally a suite of logs are collected. At this well 

we employed various borehole probes; each probe collects several physical property 

measurements. Though some measurements are redundant this approach is applied because two 

logs may provide answers that may not be possible with either log separately, and each 

additional log may add much more to an understanding of the system (Keys, 1989). 

2
Combined physical property data can be used to provide other useful information about a 

borehole such as volume, structure, strike and dip, fracture apertures and sizes, fracture density, 

borehole deviation, and lithologic contacts. 

Outcrop Characterization 

Geologic characterization of nearby outcrops was conducted for comparison with the 

borehole. Nearby outcrops consist largely of Ayer Granite with screens and xenoliths of Berwick 

Formation metasedimentary rocks. Both the Ayer and the Berwick contain crosscutting dikes and 

sills of foliated biotite granite and granite pegmatite. The biotite granite resembles the nearby 

Devonian Chelmsford Granite. Fracture characterization was conducted at a large roadcut on 

Alpine Way (fig. 4) and included measurement of all fractures over a distance of 25 m with trace 

length ≥1 m on the western end of the roadcut. The rock type is dominantly biotite granodiorite 

with 1-2 cm microcline megacrysts. There are two large foliation-parallel xenoliths or screens 

(~1-2 m thick) of Berwick Formation biotite-quartz-plagioclase granofels and calc-silicate 

granofels within the roadcut (fig. 4). Smaller xenoliths of Berwick Formation are visible on the 

top of the outcrop on the south side of the road. The Berwick Formation and the Ayer Granite 

share the same dominant foliation; in other words, both rocks pre-date the major foliationproducing deformation event in the crystalline rocks. The Berwick Formation is rusty weathering 

and locally sulfidic. The Ayer Granite is rusty weathering near the contacts with Berwick. Some 

fresh, non-rusty sulfides were seen in the Ayer. A summary of the findings includes 

1. Sheeting fractures (low angle joints (<20o) often associated with parallel foliation, rock 

cleavage, or quartz veins) some with water seeps, generally strike NNW and dip gently 

ENE. Most are blind (not continuous) and planarity is moderate to low. Spacing is ~0.2 – 

1.0 m, and increases with depth. 

2. Steeply to moderately dipping foliation strikes NE and dips SE and shows occasional 

parting in the Ayer and well-developed parting in the Berwick. Foliation-parallel 

fractures are throughgoing. 

3. NW striking, sub-vertical faults all show NE side-up relative motion with slickensides 

plunging moderately to the SE. General motion is left-lateral, north side up and to the 

NW. All faults are blind and show low to moderate planarity (in other words, some are 

slightly curved). 

4. Steeply dipping very planar joints trending ~170o are throughgoing and cross all 

structures. They are not uniformly distributed across the outcrop, but occur in zones with 

~0.2 – 0.6 m spacing. 

5. Subordinate fractures include steeply dipping, abutting and blind joints striking ~EW to 

ENE. Trace lengths are generally < 2 m. 

6. Minor parting occurs along late, thin (< 10 cm thick) NE striking tabular pegmatite dikes. 

3
7. The orientation of the dominant foliation is approximately the same in the borehole as it 

is in the roadcut. In the borehole, the approximate dip, dip direction and strike are 56o, 

123o, 33o. This orientation is approximately the same as the small fracture seen at 294.4 

m (51o, 123o, 33o). 

Planar features measured in the borehole are shown in figures 3 and 5. A comparison 

with features observed in the borehole indicates the following: 

• Gently to moderately dipping fractures (see item 1 above) are common to the borehole 

and the outcrop, as are steeply dipping E-W trending fractures (item 5 above). Northsouth trending fractures seen at the outcrop were not observed in the borehole (item 4 

above). 

• Foliation in the borehole is fairly uniform and has a similar orientation at the outcrop 

(item 2 above). 

• Granite and pegmatite dikes in the borehole have many orientations, but show two 

preferred directions with a NE strike and a SE and NW dip; the former is parallel to the 

foliation. 

Dissolved Gas Analysis 

Water samples were collected from the well by the USGS in May and June 2006. In May 

2006, water samples were collected from the bottom of the well with a stainless steel in-situ 

sampler and from approximately 73 m below ground surface with a turbine pump. Pumped 

samples were collected in 100 ml glass vials closed with silicone septa using standard USGS 

sampling procedures for dissolved gases in groundwater. Aliquots from the bottom in-situ 

samples were collected in 100 ml glass vials closed with silicone septa, but were exposed to air 

during shipping. Samples collected from the bottom of the well in June 2006 with an in-situ 

sampler were transferred from the sampler into gas sampling bags without exposure to air. All 

samples exsolved gas at the surface (fig. 6). 

Analytical results are listed in table 2. In addition to USGS analyses, Table 2 includes an 

analysis of the Skyline Drive well performed by the Massachusetts Department of Environmental 

Protection (Mass DEP) in May 2005, and analyses of two samples from other bedrock wells in 

Massachusetts, also provided by the Mass DEP. 

There are two obvious features in the molecular analyses in table 2 for the Skyline Drive 

well. The gases are dominated by nitrogen and oxygen, essentially air, and methane was not 

detected in the USGS samples taken in 2006 and the methane concentration in May 2005 in the 

sample taken by the Mass DEP was very low, only 0.288 molecular precent. Ethane was detected 

only in the Mass DEP sample, and all other hydrocarbon gases up to C6 (hexane) were below 

detection limits. 

The only stable isotopic data for methane in the Skyline Drive well is the analysis of the 

Mass DEP sample that has a carbon isotopic composition of -41.28 permil relative to Pee Dee 

Belemnite Standard (PDB). One goal of the USGS sampling in 2006 was to confirm this value 

and provide an analysis of the hydrogen isotopic composition. This was not possible. The carbon 

4
isotopic composition of methane in other bedrock wells in Massachusetts ranges from -70 to -78 

permil relative to PDB. The carbon isotopic composition of dissolved inorganic carbon ranged 

from -14.4 to -20.5 permil relative to PDB. The isotopic composition of nitrogen was measured 

in one sample with δ15N = 0.29 permil relative to air. 

The origin of hydrocarbons in the Skyline Drive well is problematic because methane is 

no longer present. Unpublished isotope data and composition data from the Mass DEP (Stephen 

Hallem, written commun. 2006) are intriguing, but frustrating because duplicate measurements 

were not possible. The carbon isotopic composition of methane (no hydrogen isotope data 

unfortunately) is in the range of thermogenic petroleum gas (fig. 7), but the amount of ethane is 

low enough that this isotopic composition could be due to microbial oxidation of an original 

microbial gas that looks like the others. The concentration of methane that Hallem measured is 

so low that the gas would not be flammable. We could not measure methane in either of our 

samples, but present a hypothetical time line. The well produces "no water" but blows out 

enough flammable gas (has to be greater than about 30 percent methane) to start a fire when 

drilled in 2004. By May 2005, the water level in the well had recharged to its current level and 

the dissolved gas contained only 0.288 percent methane, a trace of ethane and measurable 

amounts of He and H2, but generally looked like atmospheric air. We sampled it a year later, find 

no detectable methane, H2, or He, the gas looks like air, and the water recharge rate is clearly 

very, very low. 

This suggests the methane content has decreased with time to essentially zero. This could 

be due to microbial oxidation. The original, flammable gas was most likely of microbial origin, 

probably by CO2-reduction, using H2 from redox reactions with water in the granite (Sherwood 

Lollar, and others, 1993). Once the system was opened, microbial oxidizers took over and 

consumed the remaining methane, at least in the well bore. 

Acknowledgments 

We would like to thank Paul Blain and Stephen Hallem of the Massachusetts Department 

of Environmental Protection for their cooperation in this study, and permission to publish water 

quality results. We thank Dr. David Wunsch, New Hampshire State Geologist, for assistance 

with Mass DEP sample collection. We also thank Michael Schena of Connell Construction for 

permission to study the well. 

References Cited 

Barton, G.J., Burruss, R.C., and Ryder, R.T., 1998, Water quality in the vicinity of Mosquito 

Creek Lake, Trumbull County, Ohio, in relation to the chemistry of locally occurring oil, 

natural gas, and brine: U.S. Geological Survey. 

Bernard, B.B., Brooks, J.M., and Sackett, W.M., 1976, Natural gas seepage in the Gulf of 

Mexico: Earth and Planetary Science Letters, v. 31, p. 48-54. 

Burruss, R.C., and Ryder, R.T., 2003, Composition of crude oil and natural gas produced from 

14 wells in the Lower Silurian "Clinton" sandstone and Medina Group, northeastern Ohio 

and northwestern Pennsylvania: U.S. Geological Survey, p. 64. 

5
Keys, S.K., 1989, Borehole geophysics applied to ground-water investigations: National Water 

Well Association, Dublin, Ohio, 313 p. 

Salvini, F., 2004, Structural Data Integrated System Analyzer software: (DAISY 4.01): 

Dipartimento di Scienze Geologiche, Universita degli Studi di “Roma Tre”, Rome, Italy. 

Sherwood Lollar, B., Frape, S.K., Fritz, P., Macko, S.A., Welhan, J.A., Blomqvist, R., and 

Lahermo, P.W., 1993, Evidence for bacterially generated hydrocarbon gas in Canadian 

Shield and Fennoscandian Shield rocks: Geochimica et Cosmochimica Acta, v. 57, p. 

5073-5085. 

Whiticar, M.J., 1999, Carbon and hydrogen systematics of bacterial formation and oxidation of 

methane: Chemical Geology, v. 161, p. 291-314. 

Zen, E-an, editor, and Goldsmith, Richard, Ratcliffe, N.M., Robinson, Peter, and Stanley, R.S., 

compilers, 1983, Bedrock geologic map of Massachusetts: U.S. Geological Survey, scale 

1:250,000.

6
Figures 

Figure 1. Location map showing the bedrock well, nearby outcrops, and a cross section (A-A’) 

through the well from Scribner Road to Westford Road. 

7
Figure 2. Plot of fracture locations and type by depth in the borehole. 

8
Figure 3. Plot of geophysical properties measured in the Skyline Drive well. Includes Wulff 

plots of measured foliation (green dots on Wulff plot correspond to green lines on borehole 

view), dikes (purple), and fractures (red) by depth (see also fig. 4). A scalable plot is included on 

the DVD but must be viewed with the WellCAD reader for the details in full resolution.

9
Figure 4. Lower hemisphere equal area projection showing the orientation and type of fractures 

at the Alpine Way roadcut, and photograph of the roadcut. Structural data plotted with Daisy 

software (Salvini, 2004). Numbers 1-6 (stereonet) and 1-4 (photograph) correspond to 

features described in the text. Arrows on the photograph show two large screens of Berwick 

Formation within the Devens – Long Pond facies of the Ayer Granite. View is looking to the 

north-northeast. 

Figure 5. Lower hemisphere equal area projections of measured structures observed in the 

borehole. Structural data plotted with Daisy software (Salvini, 2004). 

10
Figure 6. Photograph of Isotech Isobag showing in-situ sample from the bottom of the well with 

exsolved gas bubbles. Sample collected on June 20, 2006. 

11
Figure 7. Hydrocarbon molecular composition versus the carbon isotopic composition of 

methane for gases in Table 2 showing the fields for gases of microbial origin (green box) and 

petroleum gases from thermogenic cracking of sedimentary organic matter (red box). The 

composition of gases that are oxidized by microbes can be shifted from the range for microbially 

generated gas toward thermogenic gas by partial removal of methane as indicated by the arrow 

(Bernard and others, 1976; Whiticar, 1999). In addition to the gases from crystalline bedrock in 

Massachusetts, the compositions of natural gases from Silurian age reservoirs in Ohio and 

Pennsylvania and shallow water supply wells in Ohio, are shown for comparison (Barton and 

others, 1998; Burruss and Ryder, 2003). The mixing line is calculated for gases with the endmember compositions with points for 20 percent increments of mixing. There is no evidence of 

mixing between microbial and thermogenic gases in the samples from Massachusetts.

12
13

Table 1. Water level measurements made by water level probe in the Skyline Drive well, Tyngsborough, 

Massachusetts.

Date Time 

Depth to water below 

ground surface (m) Method 

2 May 2006 10:15 AM 38.71 water level probe 

pumped unknown volume of water 

3 May 2006 09:00 AM 45.64 water level probe 

4 May 2006 09:00 AM 45.57 water level probe 

Table 2. Molecular and isotopic compositions of gases in groundwater from wells in crystalline basement rocks, 

Massachusetts. 

Molecular Composition 

Isotech1

 Sample Location He H2 Ar O2 CO2 N2 C1 C2

Lab No. Name Name % % % % % % % % C1/C2+ 

81605 Deep well water 13 Skyline Dr., Tyngsborough 0.123 0.152 1.07 16.09 0.29 81.99 0.288 0.0017 169.4 

97779 

06RCB13 Bottom 

hole 13 Skyline Dr., Tyngsborough 1.37 21.94 0.79 75.90 

97780 06RCB14 A 13 Skyline Dr., Tyngsborough 1.56 12.18 3.93 82.33 

62006-

1 2919-C6620 13 Skyline Dr., Tyngsborough 1.33 24.93 0.96 72.78 

88334 31 Constantine Dr. 

31 Constantine Dr., 

Tyngsborough 1.24 11.35 0.26 81.42 5.72 0.0147 389.1 

97781 Wales Brookside Wales Brookside 0.977 3.97 0.061 82.57 12.42 0.0031 4006.5 

Isotopic Composition 

Isotech Sample Location δ

13C1 δDC1

δ

13C 

DIC 14C1

Std. 

Dev. 

δD 

H2O

δ

18O 

H2O δ15N

Lab No. Name Name ‰ per mil ‰ pMC ‰ ‰ ‰ 

81605 Deep well water 13 Skyline Dr., Tyngsborough 

-

41.28 -14.44 2.6 0.2 

97779 

06RCB13 Bottom 

hole 13 Skyline Dr., Tyngsborough -18.74 

97780 06RCB14 A 13 Skyline Dr., Tyngsborough -20.49 

62006-

1 2919-C6620 13 Skyline Dr., Tyngsborough -17.58 -61.7 -9.23 0.29 

88334 31 Constantine Dr. 31 Constantine Dr., Tynsboro 

-

78.08 -244.2 0.4 0.1 

97781 Wales Brookside Wales Brookside 

-

70.07 -247.0 -13.36 

1

Analyses by Isotech Laboratories, Inc., Champaign, Illinois.