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Scientific Drilling, No. 14, September 2012 39
CORK-Lite: Bringing Legacy Boreholes Back to Life
by C. Geoffrey Wheat, Katrina J. Edwards, Tom Pettigrew, Hans W. Jannasch,
Keir Becker, Earl E. Davis, Heiner Villinger, and Wolfgang Bach
doi:10.2204/iodp.sd.14.05.2012
3URJUHVV5HSRUWV
Introduction
An essential aspect of the forty years of deep-sea scien-
tific drilling has been to maximize the scientific return
during each expedition while preserving samples for future
investigations. This philosophy also extends to borehole
design, providing the community with tens of cased legacy
boreholes that penetrate into the basaltic crust, each ripe for
future investigations of crustal properties and experiments
to determine crustal processes (Edwards et al., 2012a).
During Integrated Ocean Drilling Program (IODP)
Expedition 336 to North Pond on the western flank of the
Mid-Atlantic Ridge at 22qN, Hole U1383B (Fig. 1) was plan-
ned to be a deep hole, but was abandoned when a 14.75 -inch
tri-cone bit catastrophically failed at 89.9 meters below the
seafloor (mbsf ) (Expedition 336 Scientists, 2012). This
resulted in about 36 meters of open hole below casing, sim-
ilar to conditions within tens of legacy boreholes. Because
the overall experiment required a return to the “natural”
hydrologic state in basaltic basement, it was critical to seal
the hole to prevent a hydrologic “short circuit ”. Thus, a plan
emerged at sea to seal Hole U1383B with a simplified
Circulation Obviation Retrofit K it (CORK) termed
“CORK-Lite” that could be deployed by a remotely operated
vehicle (ROV) on a planned dive series five months later.
To prepare for this deployment, a standard ROV platform
that is used with CORKs was modified to be self-guiding in
the re-entry cone and deployed. The next step was to design
a CORK system that could seal the borehole, yet be physi-
cally manageable with an ROV, and be ready for shipping and
deployment within three months. Several key functional
aspects dictated the design of the new COR K-Lite (Table 1).
Design of CORK-Lite
The COR K-Lite has four major compo-
nents: the body with a seal, a removable
cap, a downhole instrument string, and a
borehole pressure monitoring instrument.
The body is a 4.9 -m-long 12 -inch pipe with a
landing seal ring that has a diameter of
19.5 inches that fits within the 32-inch
guide hole in the ROV plat form ( Figs. 2, 3).
The landing seal ring lands on and seals
in the 20-inch casing hanger. The body
has hooks to hang instruments, two valve
bodies that accept hydraulic connectors
closed in the horizontal position (Wheat
et al., 2011), two flanges (lifting wings) for
deployment that also serve to aid in moving
the body during ROV operations, and a
grooved top ring made of stainless steel to
insure a proper seal is achieved with the
cap. A re-movable “boot ” was designed to fit
the bottom of the body to protect it during
deployment and to prevent it from penetra-
ting into the sediment during free fall. In
addition, a lif ting bar assembly was fabrica-
ted that connects the body to a float pack-
age and eases handling by the ROV.
Figure 1. Location of IODP Sites drilled during Exp. 336 (North Pond) and ODP Hole 1074A
(duplicated from Expedition 336 Scientists, 2012). The CORK-Lite was deployed at Site
U1383. Bathymetry was provided by Schmidt-Schierhorn et al. (2012).
395A
U1382
U1384
(NP-1)
U1383
(NP-2)
1074A
-46°12' -46°10' -46°08' -46°06' -46°04' -46°02' -46°00'
-46°12' -46°10' -46°08' -46°06' -46°04' -46°02' -46°00'
22°54'
22°52'
22°50'
22°48'
22°46'
22°44'
22°42'
22°54'
22°52'
22°50'
22°48'
22°46'
22°44'
22°42'
-6000 -5500 -5000 -4500 -4000 -3500 -3000 -2500 -2000
m
km
0510
N
W
40 Scientific Drilling, No. 14, September 2012
3URJUHVV5HSRUWV
The downhole instrument string utilized components
from Exp. 336 (osmotic pumps, coils of small bore sample
tubing, support rods and various connectors) that were de-
signed for deployment within the 3-inch confines of the
Exp. 336 CORKs. With the larger diameter available to the
CORK-Lite, seven osmotic packages were coupled into one
unit (Fig. 5). These packages include standard, dissolved
gas, acid addition, enrichment, BOSS (fluid sampler that is
preser ved with R NA later for microbial-based analysis),
and microbial colonization experiments ( Jannasch et al.,
2004; Wheat et al., 2011; Orcutt et al., 2010). A frame was
designed to hold these packages, protect them during
The cap was designed to fit on the top of the body and seal
it using a rubber gasket ( Fig. 4). In case the borehole forma-
tion is over-pressured, four latching dogs are included.
These dogs are activated by a mechanical lever system that
forces the dogs in place through vertical motion of a floating
nut driven by a power screw with attached handle. A two -way
valve (closed in the horizontal position) is included in the
cap. This valve is necessary to equalize the pressure before
removing the cap if the borehole is under-pressured. A pad
eye is welded under the cap to at tach the downhole instru-
ment string.
Figure 2. The CORK- Lite body is lowered over the side of the R/V Maria S. Merian.
The boot is held in place with a tee handle and secured with a bungie. The lifting bar
assemblely is attached to the body with triple-strand polyproplyene rope and floats
above. Extra Alvin dive weights were attached to the hooks for faster descent.
Table 1. A list of design consideration of CORK-Lite.
t The CORK-Lite has to be installed using an ROV, with weight being balanced by flotation.
t The CORK-Lite body must be self-centering, fit within the 16-inch casing, robust enough to withstand ROV operations, and
extend ~2 m above the ROV platform for ease of ROV manipulations.
t The seal must apply for either an over-pressured or under-pressured system.
t Any negative differential pressure across the top seal cap must be vented prior to eventual removal of downhole instruments.
t Two valves and ports (for redundancy) must attach to and penetrate the body for pressure monitoring within the borehole.
t Any instrument string has to fit within the steel pipe used as the CORK-Lite body.
t For safety, the instrument package must reside within the casing; intakes for fluid sampling must extend into the open borehole
in an attempt to get “clean” borehole fluids free of possible artifacts from the steel casing and cement above.
Figure 3. Schematic of the CORK-Lite body during
free fall to the seafloor.
FLOATS
LIFTING BAR
ASSEMBLY
SAMPLING
VALVE BODY
INSTRUMENT
HANGER HOOK
PLUG BODY
323.8 mm
ø
(12.75 in)
495.3 mm
ø
(19.49 in)
LANDING/SEAL
RING
BOOT RELEASE
T-PULL PIN
BOOT
4.9 m
(192.1 in)
5.8 m
(228.3 in)
Scientific Drilling, No. 14, September 2012 41
deployment and recover y, and guide them into the
CORK-Lite body. These frame components have a
diameter of 10.75 inches, which easily fit through
the 12-inch CORK-Lite body (12-inch I.D.).
Because of borehole inst ability issues within other
CORKs, we placed the instrument package near
the bottom of the casing yet have the sample
intakes extend meters into the open portion of the
borehole. Intakes were protected with Tygon
tubing and attached to a strength member (rope)
and sinker bar. A weak link was positioned just
below the instrument package in case the bore-
hole is unstable and traps the sinker bar. Thus, the
instrument package can be recovered even if the
sinker bar becomes entombed.
The pressure monitoring device was developed
at the Pacific Geoscience Centre (Sidney, BC,
Canada), identical to most systems deployed on
CORK s today, including those deployed on IODP
Exp. 336 and previously on Exp. 327 and 328 (see
technical descriptions in Davis et al., 2010; Fisher
et al., 2011; Edwards et al., 2012b). The instrument
includes batteries, electronics, two absolute pres-
sure gauges (Paroscientific Model 8B-7000; one
to monitor the formation and the other to monitor
the sea floor), a data logger (set to sample pres-
sure and temperature every t wo minutes like
the Exp. 336 CORKs in IODP Holes U1382A and
U1383C), an underwater mateable connector
(Teledyne ODI), and a stainless steel line that con-
nects to an ROV-deployable hydraulic coupler that
fits in the valve package on the CORK-Lite body.
ROV Operations
Operations were conducted with the
U.S.-operated ROV Jason from the German
research vessel R/V Maria S. Merian during expe-
dition MSM 20/5. The ROV platform was inspected
on Jason dive J2-623 (20 April 2012). Before the
next dive the CORK-Lite body was deployed with
~770 lbs of flotation. During the second dive the
CORK-Lite was located, transported to the bore -
hole, and lowered into place. A black stripe was
painted on the body prior to deployment and used
as an indicator that the body was in the proper position. After
the subsequent dive the downhole instrument string was
deployed. The instrument string included (from bottom to
top) descent weights, a sinker bar, a 12-m-long three-strand
polyproplyene rope with a weak link and intakes that
extended 8 m from the instrument package, the instrument
package (seven OsmoSampler packages, and three
self-contained temperature recorders), a 50-m length of
3/8-inch spectra, the top plug, and flotation. T he instrument
string was located and installed, and the valves were closed.
Later in the dive program the pressure logger was attached,
and the data set that was retrieved indicated that the
CORK-Lite was sealed (Fig. 6).
Future Applications
The design, fabrication, and operational effort at Hole
U1383B illustrate the engineering potential to seal and
instrument any of the tens of legacy boreholes that have been
drilled into basement and cased through the sediment,
leaving tens to hundreds of meters (in some cases up to
1500 meters) of open borehole (Edwards et al., 2012a).
Figure 4. A CORK-Lite was successfully deployed and instrumented in IODP Hole
U1383B. The cap (silver material above the gray pipe) is secured to the body utilizing
the handle with a shor t piece of rope that originally was connected to flotation. T he
pressure logger rests on the ROV plat form and is connected to the CORK-Lite body.
Figure 5. The downhole instrument package is fabricated before connecting it to the
intake and ropes that space the package at the proper depth in the borehole. Seven
osmotic packages are arranged in a bundle.
42 Scientific Drilling, No. 14, September 2012
3URJUHVV5HSRUWV
Acknowledgements
We want to thank the engineering and operational staff
involved in IODP Exp. 336, the crew of the R /V Maria S.
Merian, and the team that operates the ROV Jason. Funding
was awarded from the Gordon and Betty Moore Foundation,
the German Science Foundation (DFG), and the National
Science Foundation ( NSF) through the STC Center for Dark
Energy Biosphere Investigations (C-DEBI) (0939564) and
individual research grants to CGW (OCE-0939564 and
1030061), KJE (OCE-1060634) and KB (OCE-0946795 and
1060855 for pressure-logging system). This is C-DEBI con-
tribution number 132.
References
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the basaltic ocean crust: Implications for chemolithoauto -
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Acta, 67(20):3871– 3887, doi:10.1016/S0 016-7037(03)
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Davis , E.E ., Becker, K., Pet tig rew, T., Carson, B., a nd MacDonald, R.,
1992 . CORK: A hydrologic seal and downhole obser vatory
for deep-ocean boreholes. In Davis, E.E., Mottl, M.J.,
Fisher, A.T., et al., Proc. ODP, Init. Repts., 139: College
Station, TX (Ocean Drilling Program), 43–53. doi:10.2973/
odp.proc.ir.139.103.1992
Davis , E.E ., Malone, M.J., and the Expedition 328 Scientists and
Engineers, 2010. Cascadia subduction zone ACORK obser-
vatory. IODP Prelim. Rept., 328. doi:10.2204/iodp.
pr.328.2010
Edwards, K .J., Becker, K., and Colwell, R ., 201 2a. T he deep, dark
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Edwards, K .J., W heat , C.G., Orcutt, B.N., Hulme, S., Becker, K.,
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ment of borehole observator ies and exper iments during
IODP Exp. 3 36. Mid-Atla ntic R idge flank at North Pond.
Placing sensors, samplers,
and experiments in legacy
boreholes could address
a range of f undamental
questions about condi-
tions and processes within
igneous oceanic crust. For
example, the basaltic crus-
tal aquifer plays a sub-
stantial role in cooling the
Earth, regulating biogeo-
chemical cycles within the
oceans, and providing dif-
ferences in redox poten-
tials (i.e., bet ween oxidiz-
ing seawater and reducing
basaltic minerals) that
offer great potential for
abiotic and biologically-mediated electron transfer reactions
(Bach and Edwards, 2003; Fisher and Wheat, 2010). With
appropriate instrumentation in selected legacy boreholes,
we will be able to prov ide a better measure of the range of
biogeochemical processes w ithin the basaltic crust and the
global significance of these processes. Legacy boreholes can
serve other communities as well, for example, by providing
access for a range of sensor suites for geological and geo-
physical studies.
Because legacy boreholes are typically cased with
10.75-inch pipe or larger, they can accept a range of sensors
and instruments that typical CORKs cannot accept
(many limit internal instrument diameters to 3.5 inches).
Furthermore, there are a number of instrument suites de-
veloped by Schlumberger Limited that cannot be used in
typical IODP boreholes but could be used in legacy bore-
holes. Although the initial COR K-Lite did not include electri-
cal cables or an umbilical, futu re COR K-Lites could be mod i-
fied to include such connections that penetrate the cap for
seafloor interrogation of downhole sensors. Also, it is con-
ceivable to deploy swellable packers, baffles, and other
means to eliminate or minimize vertical fluid exchange
within the borehole, allowing one to examine specific geo-
logic or hydrologic horizons.
For some applications CORK-Lite provides an inexpen-
sive alternative. It is especially useful for boreholes with sin-
gle horizons, as it allows for the use of less armored and less
expensive umbilicals, and it eliminates the need for an inner
casing string or extensive wellhead structure. Furthermore,
deploying such systems into legacy boreholes is indepen-
dent from the drilling schedule. In some ways the COR K-Lite
is a rejuvenation of the original CORK concept (Davis et al.,
1992), but it is much more versatile. IODP Hole U1383B is
just the start! We envision future CORK-Lites that address a
range of scienti fic questions, utilizing a variet y of instru-
ments, sensors, and experiments.
00:00 03:00 06:00 09:00 12:00 15:00 18:00 21:00 00:00 03:00
44970
44980
44990
29–30/Apr/2012
Pressure [kPa]
CORK 1383B
seaoor
formation
45000
On ROV platform at U1383C
Attached to U1383B
Figure 6. Pressure data from the CORK-Lite at IODP Hole 138 3B. Before the instrument was attached, both
sensors monitored bottom seawater on the ROV platform at Hole U1383C. After attachment, the two readings
are different, signifying that the borehole is sealed and under-pressured relative to bottom seawater.
Scientific Drilling, No. 14, September 2012 43
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Authors
C. Geoffrey Wheat, Global Undersea Research Unit,
University of Ala ska Fairba nks, P.O. Box 475, Mos s Land ing,
CA 95039, U.S.A ., e-mail: wheat@mbari.org
Katrina J. Edwards, Department of Biological Sciences,
Marine Environmental Biology Section, University of
Southern California, L os Angeles, CA 90089, U.S.A., e-mail:
kje@usc.edu
Tom Pettigrew, Pettigrew Engineering, 479 Nine Mile
Road, Milam, TX 75959, U.S.A., e-mail: pettigrew.engineer-
ing@windstream.net
Hans W. Jannasch, Monterey Bay Aquarium Research
Institute, 7700 Sandholdt Road, Moss Landing, CA 95039,
U.S.A., e-mail: jaha@mbari.org
Keir Becker, University of Miami, 4600 Rickenbacker
Causeway, Miami, FL 33149, U.S.A., e -mail: kbecker@
rsmas.miami.edu
Earl E. Davis, Pacif ic Geoscience Centre, Geological
Survey of Canada, 9860 West Saanich Road, Sidney, BC V8L
4B2, Canada, e-mail: edavis@nrcan.gc.ca.
Heiner Villinger and Wolfgang Bach, Department of
Geosciences, University of Bremen, Klagenfurter Strasse,
28359 Bremen, Germany, e-mail: vill@uni-bremen.de,
wbach@uni-bremen.de