Microseismic monitoring of the B-sand hydraulic fracture experiment at the DOE/GRI multi-site project Page: 3 of 10
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N.R. Warpinski, T.B. Wright, J.E. Uhl, B.P. Engler, P.M. Drozda, R.E. Peterson
In addition to improving fracture diagnostics, a secondary
goal of the M-Site experiments has been to improve and
validate fracture models and to better understand model
mechanisms. This goal is accomplished by providing a site
with well known properties, fully monitored fracture
treatments, time-imaged fracture geometries, comparison of
diagnostic results with various models, and even specialized
fracture monitoring technology (as in an intersecting well) that
can provide previously unavailable information.
Details of the M-Site layout and fracture treatments have been
given in a companion paper (Peterson et al.") and are only
briefly repeated here. The M-Site field experiments, located
at the previous Multiwell Experiment site in the Piceance
basin of Colorado, are co-funded by the Gas Research
Institute (GRI) and the US Department of Energy, and several
additional contractors are funded directly by GRI. The
reservoirs undergoing testing are fluvial Mesaverde sand-shale
sequences, so the technologies developed in this difficult
environment are easily translatable to many other reservoirs
throughout the world. Details of previous work can be found
in several papers and reports. 12
A schematic of the well, instrument, and sandstone layout
are shown in Figure 1. The site consists of one treatment well
(MWX-2), one monitor well with cemented-in triaxial seismic
receivers and bi-axial inclinometers and one cased observation
well for wireline run tools (MWX-3). Not shown in the figure
is an intersection well with deviated laterals for penetrating
through the created hydraulic fractures in each sandstone.
The monitor well provides the instrumentation for
validating the seismic results. Thirty triaxial receiver stations,
with low-noise, wide-bandwidth accelerometers provide high
quality microseismic data which can be accurately located. In
the same well six bi-axial tiltmeters with nanoradian
resolution provide information on the mechanical deformation
of the formation which is used to validate the seismic results.
The 7-in cased observation well is used for multi-level,
wireline-run, triaxial receiver arrays, of the type that will be
used in a commercial fracture diagnostic service. This array
uses the same accelerometers as are grouted in the monitor
well, and the multi-level feature also provides for highly
accurate microseismic event location. The monitor well
results, with many more levels to apply in location algorithms,
are used to verify the data obtained from the wireline receiver
Additional information obtained in the treatment well,
such as bottom-hole pressure, spectral gamma logs of
radioactive tracer distributions, and seismic surveys, are used
for detailed fracture modeling and additional diagnostic
information. Detailed stress, rock property and reservoir
property data are also available for these reservoirs and are
used for fracture models, finite element deformation models,
and analyses of the mechanical response of the formation to
the fracture treatment.
Additionally, crosswell seismic surveys were conducted to
determine the p-wave and s-wave structure at the site.
Seismic data were obtained with 5-ft source and receiver
spacings in the treatment and monitor well, respectively, and
the permanent 30-ft spacing of the cemented receivers in the
monitor well. The seismic source was an airgun which
provided excellent p-waves and generally good s waves. Both
p and s tomograms have been produced, as well as Poisson's
ratio and calculated uniaxial stress tomograms.
The lithology of the B sandstone is somewhat complicated
by a second sand lobe that lies below the main 30 ft interval of
the B sandstone. Figure 2 shows a gamma log of this
configuration taken from the treatment well. The stress
contrasts around the B sand, as determined from microfracture
stress measurements, are shown in Figure 3. For modeling
purposes, more detailed calibrated stress logs were also
During B-sand testing, six different fracture injections
using three different fluids were monitored. Important
information on the injections are given in Table 1.
Table 1 Treatment Data
FRACTURE VOLUME FLUID RATE SAND
(bbl) (bpm) (LB)
2B Step-Rate 27 KCI 0.5-3
363 Pump-In #1 100 KCI 10
46 Pump-In #2 210 KC0! 10
56 Minifrac #1 400 40# Linear 22
66 Minifrac #2 400 40# Linear 22
76 Propped Frac 670 X-Link Gel 20 77,600
Cemented-in receivers in the monitor well were oriented using
three different techniques. During installation of the
receivers, a radioactive pip was inserted in a known location
on the receiver, and, subsequent to cementing, was located
using a rotating gamma-ray logging tool. This orientation was
confirmed using polarization data from perforations in the
treatment well and from polarization of the crosswell survey
data. With the exception of a couple of levels in which one or
more receiver axes were clearly non-functioning, there was
good agreement between the different orientation techniques.
Orientation of the five-level receiver system was
accomplished by conducting an airgun orientation scan in the
treatment well at 10-ft spacing over the interval in which
microseisms were expected. Polarizations of p-wave arrivals
for each level were analyzed to provide accurate orientation.
Microseisms were processed in the standard manner, with p-
wave arrivals, s-wave arrivals, and p-wave particle motion
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Warpinski, N. R.; Wright, T. B.; Peterson, R. E. & Branagan, P. T. Microseismic monitoring of the B-sand hydraulic fracture experiment at the DOE/GRI multi-site project, article, November 1996; Albuquerque, New Mexico. (digital.library.unt.edu/ark:/67531/metadc678891/m1/3/: accessed December 12, 2018), University of North Texas Libraries, Digital Library, digital.library.unt.edu; crediting UNT Libraries Government Documents Department.