l Research & Projects l
| Abstract | Introduction | Field
Operations | Tools, Calibrations, and Data Processing |
| Results and Discussion | Concluding
Remarks | Acknowledgments | References |
Logging Results from the Newark Rift Basin Coring Project
D.S. Goldberg(1), D.J. Reynolds(1,3), C.F. Williams(2),
W.K. Witte(1,4), P.E. Olsen(1) and D.V. Kent(1)
1. Lamont-Doherty Earth Observatory of Columbia University, Palisades,
2. U.S. Geological Survey, Menlo Park, CA 94305
3. now at Exxon Production Research Co., Houston, TX 77252-2189
4. now at
University of Alaska, Fairbanks, AK 99775-0800
Wireline logs were acquired at seven sites in the Newark
Rift basin using dipmeter, gamma ray, resistivity, velocity,
porosity, density, magnetic susceptibility, temperature,
and acoustic televiewer tools. The logs indicate that the
formations are clay rich and dip on average 9 N-NW. Densities
are relatively constant (2.60-2.80 g/cc) and compressional
velocities vary from 4.2-5.5 km/s. Thin uranium-rich layers
and basalt flows are clearly delineated. The boreholes are
mostly in-gauge, but deviated, and borehole temperature gradients
vary between 15 to 260C/km. These data are potentially useful
as indicators of fluid flow and regional stress, lithologic
cycles, and for core orientation in the Newark Rift basin.
During an eight month period in 1990-1991 and two months
in early 1993, a series of seven deep core holes were drilled
through the Triassic lacustrine strata and lava flows of
the eastern North American Newark rift basin. The prime objectives
of the NSF-funded Newark Rift Basin Coring Project (NBCP)
were to unlock the history of the region's ancient climate
and tectonic history and to extend the geomagnetic polarity
stratigraphy to the interval from about 200-230 Ma [Olsen
and Kent, 1990]. An offset coring technique was used to take
advantage of the eroded half-graben geometry of the basin
(Fig. 1). In this method, the core holes
were spudded in a mappable, easily recognized lithologic
member and continuously cored through to another distinctive
unit at a depth of 3000-4000 ft (~1-l.3 km). A suitable location
of outcrop of the latter unit was identified updip as the
next drill site, and so forth, until practically the entire
Newark basin section was cored. This was done seven times
in two transects. The offset drilling approach also avoided
drilling through the Palisades diabase sill (Fig.
1). A narrow gauge, diamond coring system was used and
achieved nearly 100% core recovery. composite stratigraphy
of the core holes drilled through the Newark Rift Basin is
shown in Figure 2.
The LDEO Borehole Research Group provided for the wireline
logging in the NBCP through a commercial logging service,
in-house televiewer and susceptibility logging equipment,
and temperature logging equipment loaned by the U.S. Geological
Survey. Based on the availability of logging instruments
that fit into a narrow-gauge (4 in.) drill bore, BPB Inc.
was contracted for the commercial service. The logging services
they provided were: 3-arm dipmeter, hole deviation, natural
gamma radiation, focused resistivity, 3-channel sonic velocity,
neutron porosity, single-arm caliper and density. Magnetic
susceptibility, temperature, and acoustic borehole televiewer
logging services were recorded by LDEO, with collaboration
by the U.S. Geological Survey for temperature logging. These
logs and the core data from the NBCP are archived at LDEO.
Resistivity and gamma ray logs were also recorded by the
New Jersey Department of Environmental Protection, but are
not presented here.
The purpose of this paper is to present the wireline logging
results of the NBCP; work on the cores has been presented
at meetings [e.g. Kent and Olsen, 1994] and papers are in
preparation for journal publication. In view of the availability
of a completely cored section, the logs provide a complementary
data set which when integrated with the core enables the
calibration of in situ and laboratory measurements.
The NBCP logging program was designed to continuously measure
fine-scale in-situ properties of the borehole and the formations.
Core-log comparisons are extremely valuable, but should be
made cautiously, because logging data are far-field observations
and sample a larger volume of rock than core measurements.
This difference, however, enables an intermediate-scale link
to be made from core measurements to seismic boundaries,
which can be used to investigate the origin, age, and cyclostratigraphy
of paleoclimatic changes and seismic reflectors [e.g. Reynolds,
1993]. Vertically continuous logs also allow for depth registration
and corrections of core deformation and loss as well as certain
measurements, such as temperature and stress direction, which
can only be made in situ. In particular cases, logs
can be used for core orientation.
Geological map of the Newark rift basin
showing the locations of the seven coring sites. Most
strata dip towards the northwest and black shading indicates
the primarily gray and black Lockatong Formation and
mapped gray and black units in the overlying Passaic
Formation. Several of the latter were units used to correlate
between cores (see Figure 2). Coring sites are: M, Martinsville;
W, Weston Canal: S, Somerset; R, Rutgers; T, Titusville,
N, Nursery; and P, Princeton. Map adapted from Olsen
and Kent (1990).
Correlation between core holes from the Newark Rift
Basin Coring Project. Shading indicates portions of the
cores that stratigraphically overlap. Adapted from Olsen
and Kent (1 990).
At each of the NBCP Sites, it was necessary to drill two
or three holes to comply with New Jersey Department of Environmental
Protection guidelines. The first was a water well, drilled
with a conventional water well rig, needed to supply sufficient
water for the coring rig. The procedure with the main core
hole (called hole #1) was to conventionally drill an 8 in
diameter hole with the water well rig to a depth of 300 ft
and then case it with 4.5 ID steel pipe and grout it with
cement. Coring with the high-speed coring rig was then begun
at the base of the casing through to 3,000 to 4,000 ft (1.0
to 1.3 km), depending on the depth of the objective reference
unit. At five Sites (Weston Canal, Somerset, Rutgers, Titusville
and Princeton), an adjacent 300 ft hole (called hole #2)
was cored from the surface to sample the cased interval of
the main core hole. A polymer-based drilling mud was used
for the high-speed drilling, then fresh water was circulated
for a full volume cycle to remove the polymer mud before
logging. In total, 12 holes were drilled and logged to their
total depth with the complete suite of tools summarized in Table
1. Total core recovered was about 22,100 ft (6730 m).
Six of seven sites were drilled by Amoco Production Company's
SHADS (Scientific High-speed Advanced Drilling System) group
in a cooperative agreement with LDEO. The SHADS system combined
a wireline coring rig, a well-head control device, and a
series of "geological modules" in which the core
was initially processed, subjected to several pass-through
natural gamma and magnetic susceptibility measurements, recorded
on video, and described. The seventh Site (Weston Canal)
was cored by Longyear Drilling Co. The core was processed
on site by contracted Exlog personnel using a converted and
equipped 40-ft trailer. Continuous natural gamma, magnetic
susceptibility, and video will be obtained al LDEO from the
core from this last site.
Table 1. Summary of logging information
acqured in the Newark Rift Basin Coring Project
Table 2. Example sequence
of logging operaions
The usual sequence of logs run without
the drill rig over the hole is presented
in Table 2. This sequence of 20 to
25 logs in both holes #1 and #2 required on average 3.5
to 4.0 days to complete, including set-up, calibration,
and trouble shooting. Over the course of the 10-month
field program, log data recording was unsuccessful due
to tool failure only once, at the Rutgers site, where
the susceptibility tool calibration would not stabilize
in subzero air temperature. Several other equipment failures
were experienced due to cold weather and mechanical problems,
however no data loss occurred. Due to one such failure,
the USGS temperature log was recorded at single depth
stations at the Nursery Road site, however a BPB temperature
log was run continuously with depth and calibrated to
the USGS temperature data.
calibrations, and data processing
The logging tools used in this project were 3-arm dipmeter,
natural gamma radiation, resistivity, sonic velocity, neutron
porosity, single-arm caliper and density, magnetic susceptibility,
temperature, and borehole televiewer. The design and functionality
of each device type is summarized in Log Interpretation
Principles (Schlumberger, 1987) and in the ODP Logging
Manual (Borehole Research Group, 1990).
For the specific tools deployed in the NBCP, calibrations
were made on site by BPB for neutron, density, and gamma
ray devices by comparing the tool responses to count rates
in known test standards, such as aluminum. Sonic, resistivity,
and temperature tool responses were compared for consistency
with known values in air or steel. Caliper calibrations were
made by setting the tool responses to different casing diameters.
The borehole televiewer was calibrated on site by LDEO using
an oriented test tank. The magnetic susceptibility tool was
calibrated in air, and at one site (Titusville), it was also
calibrated with core measurements [Witte and Kent, in press].
The susceptibility logs presented here are not corrected
for non?linear drift with temperature and time from the null
calibration in air.
The logging data were all originally recorded on digital
media, except for the borehole televiewer (photographic paper
and videotape) and the magnetic susceptibility (paper) logs.
All of the digital log data are stored at LDEO on 9-track,
LIS-format magnetic tapes and in an ASCII-format, tabular
database on diskette. The susceptibility logs were digitized
from the original paper logs at the 0.4-ft database sample
interval. The borehole televiewer data are not presented
here and will be digitized from videotape into image format
and archived at LDEO.
The log database was created by translating and decimating
the LIS -format data, which was acquired at a 0.04-ft (0.5-in)
depth sampling interval. Depth shifts between logging runs
were corrected by matching the gamma ray logs recorded during
each run. Depth corrections were generally less than 2 ft.
Sonic and temperature logs were processed from raw data
for the database at the LDEO and USGS, respectively. The
three raw sonic travel-time logs, one for each source- receiver
pair, were smoothed over 60 cm to coincide with the longest
source-receiver spacing and then averaged to create a single
log. Temperature gradient logs were computed by the temperature
difference over 40-point offsets and excursions in these
data were not excluded. The dipmeter logs were processed
by BPB. Formation dip and formation azimuth estimates were
computed by automatic correlation between the three-arm microresistivity
pads at 5-ft intervals. The dipmeter pad correlation is high
when the coefficient is close to 1.0. Values less than 0.5
should be evaluated carefully because they represent a low
statistical significance of the measurement.
In Figures 3 through
9, the log database is presented graphically. The logs,
except for dipmeter data, were smoothed using a 5-pt (2.0
ft) moving depth window for display. Each site is represented
by a separate figure divided into two parts: (a) those
logs measuring hole and geometrical properties, and (b)
those measuring rock physical properties. Data from core
hole #1 and from core hole #2 are superimposed on each
figure, when applicable, occasionally generating short
gaps in the intervals near 300 ft. Because the caliper
log shows that the holes are mostly in gauge, corrections
to the data for hole size effects were not made. In general,
these logs have valid and continuous data over their depth
intervals. Intervals where no data are available are annotated.
The physical properties of the holes and the formations
encountered in the NBCP are generally similar at all 7 sites.
The caliper logs clearly show that all of the deep holes
are almost perfectly in gauge (4 in. diameter) to their total
depth. Variations in borehole diameter more than 0.5 inch
over gauge can usually be attributed to the poor registration
of the caliper arm in the vicinity of fractures, such as
observed in Martinsville and Weston Canal. Fractures in these
holes are also observed over the same depths in the core
and televiewer images.
The borehole deviation and azimuth logs systematically exhibit
an increasing trend with depth. Hole deviation increases
from 0° at the surface to as much as 10° S-SE with
depth in all the holes. This observation can be explained
by a tendency of the drill pipe to align perpendicularly
to the bedding planes of the strata while drilling, which
dip 6 to 14 degrees N-NW to W through the basin sequence.
These logs also exhibit a characteristic 50- 100 ft sawtooth
pattern over long intervals in several holes. This effect
is attributed to tool rotation and a varying magnetometer
response function, not the result of hole properties.
The typical temperature profile shows a significant hydrologic
disturbance over the upper 200 to 300 m intervals with a
conductive temperature gradient below the disturbance of
15 to 26 °C/km. Average thermal conductivity measured
on core samples range from 1.6 to 2.7 W/m 186, controlled
by the relative proportions of quartz and alteration minerals
[Williams et al., 1991J. Williams et al.  also extrapolated
the temperature measurement to the equilibrium profile, estimating
preliminary heat flow values of 38 to 44mW/m2 at all
of the sites, consistent with nearby continental provinces,
and ground water flows with a downward velocity of 1 cm/yr
at the Martinsville site. At Titusville, large variations
in temperature gradient were recorded below 500 ft depth,
possibly due to deep groundwater flow. The mean gradient,
however, is consistent with the other holes. Observing the
variations in temperature gradient, groundwater was likely
flowing through open fractures during logging, but its persistence
over time cannot be determined without long-term instrumentation
of the boreholes.
The gamma ray logs in the clay-rich lithologies drilled in the NBCP
were repeatable and are used to register depths between logging runs.
Gamma ray values were measured up to 1000-API units in thin layers,
but have a mean and standard deviation in most intervals of about 150
and 50 API units, respectively. The highest values (>300 API) occur
mostly in the lower part of the stratigraphic sequence in the black
shales of the Lockatong Fm, encountered through the bottom of Titusville,
Nursery Road, and the upper part of Princeton. In the upper 300-ft
interval of Somerset, and from about 600-ft to 1200-ft in Martinsville,
the gamma ray mean and standard deviation are half that of other intervals,
about 75 and 25 API units respectively. This is a result of the tool
response through the casing at Somerset and in the Orange Mt. Basalt
at Martinsville. The latter interval is obviously anomalous in all
of the log responses.
With the exception of anomalous intervals in the Orange
Mt. Basalt and in the lower part of Princeton, densities
vary in each hole mostly between 2.60 and 2.80 g/cc. Values
as high as 2.90 g/cc are reached in the lower Passaic formation
(Titusville), possibly due to a greater concentration of
secondary calcite and barite in the formation. Greater variability
in bulk density is observed in the Stockton arkose through
lower part of Princeton, associated with thin bedding in
this interval. Large excursions in the density log below
2.60 g/cc occur at depths coincident with excursions in other
logs and probably indicate fracturing. Bulk densities observed
in the Orange Mt. Basalt increase with depth to greater than
3.05 g/cc near 800 ft depth in Martinsville and again towards
its lower contact near 1200 ft, suggesting a decrease in
porosity at the base of basalt flow units.
The neutron porosity logs exhibit systematically higher
porosity than measured on core samples [C. Williams pers.
comm., 1991J, likely due to neutron absorption by clay in
the formation. Average uncorrected porosity values, as high
as 45% porosity in Somerset and as low as 10% in the Orange
Mt. Basalt, reflect only relative variations. Porosities
generally decrease with depth in the upper 500 to 1000 ft
of each bole. Cyclical variations in porosity with depth
are observed in Nursery as well as in other intervals. In
the basalt, porosity increases significantly towards the
top of the flow units in Martinsville, but is typically less
variable than in the overlying and underlying sediments.
Sonic travel time logs correlate directly with porosity
in the sediments and in the basalt and show similar decreases
with depth. The sonic travel times range between 55 and 65 µs/ft,
corresponding with formation compressional velocities of
4.7 kim/s and 5.5 km/s. Travel times in the basalt average
about 49 µs/ft, a velocity of 6.2 km/s.
The resistivity logs show considerable variation even as
presented on a four-decade logarithmic scale. A general correlation
with depth between resistivity and porosity is observed,
however resistivity does not correlate with density, sonic,
or gamma ray logs. In general, average resistivity values
are about 20 ohm.m in the upper part of the sequence (Martinsville,
Weston Canal, Somerset, and Rutgers holes) and between 200
ohm.m to 2000 ohm.m in the older rocks (Titusville, Nursery
Road, and Princeton holes). In this deeper sequence, gamma
ray is high and variable and sharp decreases in resistivity
are frequent, even though the highest average log values
occur. Resistivities in the Orange Mt. Basalt are high, but
variable, ranging from 500 ohm.m to 5000 ohm.m. Although
the magnetic susceptibility logs presented here have not
been corrected for temperature drift with time, they exhibit
some fine-scale correlation with resistivity and generally
show low values (20 to 40 µcgs) in sediments and extremely
high values (>6000 µcgs) in basalt. The overall
range of resistivities and magnetic susceptibilities recorded
through this sequence in the Newark Rift Basin span three
orders of magnitude.
The wireline logging data presented here from the Newark
Rift Basin Coring Project were acquired during late 1990
and early 1991 and in early 1993. High-quality logs were
acquired at seven sites and include: 3-arm dipmeter, borehole
deviation, natural gamma radiation, focused resistivity,
3-channel sonic velocity, neutron porosity, bulk density,
magnetic susceptibility, temperature, caliper and borehole
televiewer. The extremely high percentage of core recovered
presents a unique opportunity for studying these log data
in conjunction with core collected over the same intervals.
The log data and cores from the Newark Rift Basin Coring
Project are archived at LDEO.
Based on these results, in situ physical properties
can be studied through the entire Newark rift basin sedimentary
sequence and in the Orange Mt. Basalt. The clay-rich sediments
appear to be fractured and permeable, particularly at shallow
depths, and exhibit relatively consistent physical property
readings through significant portions of the Newark basin
sequence. The Orange Mt. Basalt, and flow units within it,
are delineated by anomalous physical properties observed
in the logs. Anomalies in temperature gradient suggest active
hydrologic flow in the upper intervals of all seven holes.
The log data are potentially useful as indicators of fluid
flow, the regional stress regime, and lithologic cycles in
the Newark rift basin.
We gratefully acknowledge the financial support from the
Continental Dynamics Program of the National Science Foundation
for acquisition and preparation of these data. The cooperation
of Amoco Exploration, U.S. Geological Survey, N.J. Department
of Environmental Protection, and the landowners enabled the
successful coring and logging of these holes. Technical assistance
from D. Moos, T. Moses, E. Scholz, R. Wilson, and B. Cornet
for data acquisition was essential to the success of this
project. D. Barnes prepared the logs for publication. Lamont-Doherty
Earth Observatory contribution number 5248.
Borehole Research Group, 1990. ODP Logging Manual, Vol.
3. Lamont-Doherty Earth Observatory, Palisades, NY.
C. F. Williams, J. H. Sass, T. H. Moses, and D. Goldberg, 1991.
Preliminary heat flow results from the Newark Rift Basin
Coring Project: EOS, Trans. of the American Geophysical
Union v.72, p. 504.
Kent, D. V. and P. E. Olsen, 1994. Newark Basin Coring Project:
A complete late Triassic/earliest Jurassic stratigraphic
section from a continental rift basin, Trans.
VIIth International Symposium on the Observation of the Continental
Crust through Drilling, Santa Fe, NM, April 25-30, 1994.
Olsen, P.E., and D. V. Kent, 1990. Continental Coring of the Newark
EOS, Trans. of the American Geophysical Union v.71. p.
385 and p. 394.
Reynolds, D. J., 1993. Sedimentary basin evolution: tectonics and climate
interaction, Columbia University, NY [PhD thesis], 2lS pp.
Schlumberger. 1987. Log Interpretation Principles, 2nd Ed..
Schlumberger Educational Services, Houston, TX.
Witte, W. K., and D. V. Kent, 1994. Rock magnetic and paleomagnetic
properties of red and grey siltstones from the Titusville well, Newark
Basin, in preparation.