10th Asian Regional Conference of IAEG (2015)

Development of Directional Drilling System-Outline of the System and its Application for Omagari Fault in HokkaidoKenzo KIHO(1), Takayuki SUNAGA(2) and Kazunori HASE(2)(1) Central Research Institute of Electric Power Industry, Japan
E-mail:kiho@criepi.denken.or.jp(2) Sumiko Resources Exploration & Development Co., Ltd.
Abstract
For the site selection of HLW (High Level Waste) disposal, the measurement andlogging in the borehole in order to investigate the hydro-geological and geo-mechanicalconditions of the host rock is a very important way to examine the potential of the disposal
candidates. In Japan, the Neogene soft sedimentary rock is being focused as a host rock for
HLW disposal. Especially, the soft sedimentary rock at the coastal area is thought to be oneof the best candidates, since there is little driving force of the underground water. Because
the directional drilling is supposed to be efficient under the limited topographic andgeological conditions, CRIEPI (Central Research Institute of Electric Power Industry) has
been conducting the project on directional drilling and the logging/measurement
technologies in its boreholes since 2000. Basic directional drilling system was developed
and the system was applied to the normal sedimentary rock of Neogene at the Hokushinarea of Horonobe town in Hokkaido. The borehole was drilled to the 700m long and theapplicability of the system was confirmed in 2000-2004. Based on the results, CRIEPI has
been developing the drilling and logging/measurement technologies for fault zone. The
drilling technologies such as drilling for fault zone, horizontal drilling, long hole drilling,coring and locality detection were developed and improved, and drilling system was
integrated. After conducting seismic reflection survey for the Omagari fault distributing at
the Kami-horonobe area of the Horonobe town, the drilling site and borehole trace was
decided in 2005. Considering the planned trace, the borehole was drilled to the 1000m longand its core recovery was 99.8% as of FY. 2011. Using core sample and boreholelogging/measurement/survey, the geological, hydrological, geo-mechanical, geophysicaland geochemical data were collected and the Omagari fault was characterized.
Keywords: Measurement While Drilling (MWD), Logging While Drillign (LWD)
Soft sedimentary rock, HLW management
1.

Introduction

because there is little hydraulic driving force expected
due to the sea water level and there is little humaninvasion.
Due to access and working site limitations in thiscoastal area, controlled, directional drilling methods
with core sampling were considered to provide more
useful information over conventional vertical drilling
methods (Fig. 1). In order to develop thethree-dimensional geological model; logging andmeasurement in the hole without disturbance of thenatural geological, hydrological and geochemical
condition was essential (NUMO, 2004). From thisviewpoint, the development of a directional drillingsystem which permitted the loggings andmeasurements in the borehole was required, with anurgent need to systematize the reasonable drilling andmeasuring methods.

The Neogene soft sedimentary rocks arerecognized as potentially good host rock for the HLW
disposal. This rock has following characteristics;- The geological structure is relatively simple andgeological conceptual model can be easily
constructed.
- There are few water conductive fractures in therock mass and water flow is reported to be directionalby the geological strata, so it is easy to characterize
the water flow in the rock mass.
- The fine-grained clastic rocks such as mudstone
were expected to have low permeability
characteristics.
The coastal area is supposed to be a potential
candidate area for disposal of hazardous waste

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10th Asian Regional Conference of IAEG (2015)

Figure1 Directional drilling at coastal area
CRIEPI developed the drilling technology thatenabled the various measurements and loggings in theborehole, in order to characterize the geology andhydrology of the sedimentary rocks with reasonableconfidence (Kiho, et. al., 1998). This was achieved by
1999. In 2000, CRIEPI started to develop their own
core sampling, survey and logging technology indirectional drilling applications, following guidancefrom previous work (Kiho, et. al., 2002). In this paper
we report the conceptual design and manufacture of
the directional drilling system and in-hole logging,measuring and monitoring systems, and results of thisapplication to the Horonobe site.
2.

logging, measuring and monitoring technology.
CRIEPI reviewed the existing technologies andadapted their best principles for this project.
(1) Well bending while drilling
CRIEPI considered several techniques commonlyused in directional drilling. These were DHM(Downhole Motor), Wedge Technique andDirectional Core Barrel (DeviDrillTM: Kitahara et. al.,2005) as a vending tool for directional drilling. Thesesystems were compared from the viewpoint of not
only directional drilling, but of core sampling,
locality detecting, logging/measuring. The conclusion
was that the downhole motor is most practical for thisdirectional drilling. As the wall of the borehole in thissoft sedimentary rock is unstable and collapses
without support, casing was used while drilling. The
practicalities of developing a system were examinedfrom the viewpoint of directional drilling, casing,core sampling, in-hole survey capability andlogging/measuring. This resulted that the “Wellman”
system (Sumitomo Metal Mining Co., LTD., 1986)
was most practical for the casing and under-reamer.

Development of technology

2.1 Development goals
The following development goals were
established.
- To develop the technology for the directional
drilling of 1000 m long and 500 m deep drill holes in
the coastal Neogene soft sedimentary rocks.
- To collect a full core sample while drilling evenin the fault zone. The measurements from the coresample are considered very useful for this soft
sedimentary rock.
- To make the hole as slim as possible considering
the safety handling and productivity - cost
performance.
- To make several logging, measurement andmonitoring routines during and post-drilling.

(2) Core sampling technology
The core sampling technology was examinedfrom the viewpoint of undisturbed core sampling
recovery and quality. Considering the past results andeffective sampling, the wire-line system using triple
core barrel with acrylic tube was considered mostpractical.
(3) Locality-detecting technology
The systems MWD (Measurement While
Drilling) and SWD (Seismic While Drilling) werecompared and investigated as position detection

2.2 Selection of Element Technologies
This project comprised four basic technologies:(1) well bending technology, (2) rock core samplingtechnology, (3) locality detecting technology and (4)210th Asian Regional Conference of IAEG (2015)

Figure 2

Conceptual design of the drilling downhole toolsystems. Considering the past results and locality
detecting resolution, the MWD was estimated morepractical. The data transmission system for the MWD,
such as mud pulse and transmission cable werecompared and investigated from the viewpoint oftransmission speed and data volume. The
transmission system was adopted because it cantransmit a large volume of data at high speed and it
can also be used for another logging and measuring
tools.
The measuring items of MWD are azimuth,
inclination, WOB (Weight on Bit), Torque,
Temperature, inner and outer pressure. The azimuth
is measured by the compass. The value of azimuth
can be affected by magnetic material such as rods andanother downhole assemblies, so the value of azimuth
was corrected considering magnetic effect.
Additionally, in order to measure more accurate valueof azimuth, a gyroscopic tool was developed andinsert to the hole every several ten meters.

drilling fluid was selected.
This drilling system comprised downhole tools,
casing pipe following the downhole tools in order tocase the borehole wall protecting borehole wallcollapse, and the armored cable with inserting
apparatus which can push down and pull up thedownhole tools easily and can transmit the data of thedownhole tools by telemetric line installed inside thearmored cable (Fig. 1).
From the bottom, this system comprised drilling
bit and core barrel, reamer, DHM, MWD and LWD(Logging While Drilling).
And also, at theconnection part between the downhole tools andcasing pipe, there is a latch coupling to connect andseal this joint from leaking out of the mud water (Fig.
2).
The mud fluid flow down inside the casing pipe
and also inside LWD and MWD, and provides thehydraulic pressure to rotate the DHM. Most of thefluid then flows up to the surface through the annulus,
which is the aperture between the borehole wall andoutside diameter of the casing pipe.
The tools for drilling can be pulled up to thesurface by using a wire-line cable in each 3m coreruns; to collect core sample, and if a test is deemednecessary, the drilling tools will be exchanged for thetesting tools. As testing tools we developed in-situ
permeability testing tool, pressuremeter and in-situ
stress measurement tool.

(4) Logging, measuring, and monitoring
technology
From the viewpoint that the geological,hydrological,
geochemical
andmechanicalmeasurements should be done in the hole while
drilling, the element technology of the logging andmeasurement for development were examined. There
are few past records about these technologies and few
element technologies could be recognized. The
logging, measurement and monitoring systems which
fit for the drilling system were developed.
3.

4.

Verification of applicability
In 2003 the directional drilling system wasconstructed by integrating these sub-tools, such as
angle-capable drill rig, core barrel, winged bit, DHM,
MWD and so on. Before applying this system to thesite, we verified its performance by drilling an
artificial rock mass that was made of mortar to adepth of 60 meters. The directional drilling andmeasurement system was applied to the sites ofHoronobe town in Hokkaido, in the northern part ofJapan, in order to verify the applicability of theOutline of drilling system

This system is based on the wire line drilling
principle, but conventional wire line tools can’t insert
the drilling and measurement assembly in a gently
sloping or horizontal drill hole. The water pressure
inserting apparatus (so called pump-in system) which
can insert the downhole tools by using pressure of3

10th Asian Regional Conference of IAEG (2015)

Figure 3 Geological map and drilling site
systems as a collaboration work between CRIEPI and
JNC (Japan Nuclear Cycle Development Institute).
By 2005, CRIEPI had conducted a directional drillingof 700m long and 500m deep drill hole in the
mudstone of the Koetoi formation and shale of the
Wakkanai formation of Neogene at Hokushin sitewhich is located at northern part of Horonobe town
(Kiho et al., 2005). Following this drilling, anotherdrilling was performed, targeting the Omagari fault inorder to check the applicability to characterizing thefractured zone and in-situ measurements. This work
was conducted at Kami-horonobe site, the southernpart of Horonobe town until 2013.

4.2 Results(1) Hokushin site
CRIEPI started the drilling project in order toverify the applicability of the technology ofdirectional drilling and survey/measurement at
Hokushin site in 2003. The target geology is the
Koetoi and Wakkanai formations. For 3 years from2003 to 2005, we planned to drill the borehole with
700m long. The direction of the borehole was kept
N30E and the inclination was changed from high dip
to low dip. At the mouth of the borehole, theinclination was set to 30o, and at the bottom of theborehole, the inclination was expected to be about 70o(Fig. 4).
In 2003, we started drilling and drilled a pilot hole
to 150m long with a stable inclination of 30o, thenperformed the controlled drilling to 290.3m long. In
2004, we continued to drill to 547m long with theinclination change from 30o to 55o. In 2005, we
drilled to the length of 706m with the bottom
inclination of 68o.
From 0 to 150m in length, the conventional
drilling without coring was done and the casing pipewith inner diameter of 157.8mm was finally inserted.
From 150m to 706m in length, we tried to collect thecore sample except the section of 352m - 390m where
the core drilling couldn’t be done due to big water
loss. At the core drilling section, the core recovery isalmost 100%.
The borehole was drilled with a stable inclinationof 30o from 0m to 150m long. From 150m to 290m
the directional drilling was carried out to change theinclination with change rate of 1o per 10m. The

4.1 Geological Conditions
The geology around the drilling site is mainlycomposed of the Koetoi and Wakkanai formations of
Neogene. The rock facies of these formations aremainly diatomaceous mudstone (Koetoi Formation)and hard shale (Wakkanai Formation). The thicknessof each formation is more than several hundred
meters (Fukusawa, 1985). The Horonobe area ischaracterized by the prevalence of folded structure
and the reverse Omagari fault. The axis of a fold hasa trend of north-northwest and dips to the north at thenorthern part of Horonobe. The Omagari fault has thesame trend as the fold and a trace length of 25km. It
intersects through the town centre and the outcrop of
the fault is clearer in a southern part of town (Ishii, et.
al., 2006). The porosities of the diatomaceous
mudstone of the Koetoi and Wakkanai formations areabout 60% and 30% and their uni-axial compressive
strengths are about 6 MPa and 15 MPa, respectively(Fig. 3).

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10th Asian Regional Conference of IAEG (2015)

Figure 4

Borehole trace at Hokushin site (HCD-1&2)

inclination was not changed to 250m, because we
tried to find the best combination of the bent angle ofthe kick-off sub and barrel length to change theinclination. By using new combination of the bent
angle of 0.78o and barrel length of 1.5m, we couldchange the inclination successfully from 250m to
547m.
In 2004 we met a big water loss at several
sections while drilling. At the sections, we performed
cementing to reduce the water loss, but theseprocedures took a lot of time and the schedule wasdelayed. The cause of the water loss was assumed asfollows;(i) There are many water conductive fractures

Figure 5leading to the water loss.
(ii) Highly pressurized water to move thedownhole motor causes water loss.
To prevent water loss the system was improved toreduce water pressure in the borehole.
In 2005, we identified the section of big water
loss from 482.5m to 488.5m and tried to perform
cementing at the section to reduce water loss.
From 547m to 598.7m, using combination of thebent angle of 0.78o and barrel length of 2.5m and
3.5m, the borehole could be drilled with 1.46o per
10m of inclination change, and from 598.7m to
706.0m, using combination of the bent angle of 0.39oand barrel length of 2.5m and 3.5m, the borehole

Result of directional drilling HCD-3 at Kami-horonobe site

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10th Asian Regional Conference of IAEG (2015)

Figure 6

Rock core sample at Omagari fault

could be drilled with 0.51o per 10m of inclination
change.

uni-axial compressive strength test, physical property
test.
From the results of logging and measurement in
the borehole and core logging and measurement, theOmagari fault was characterized. The fault zone
which consists of fault gauge and/or cataclasite andfractures was identified at the 24 sections of different
depth, and the fault profile deduced from seismicreflection methods coincided with the zone from f3 to
f14. The geological structure differs at f8 which isassumed to coincide with the main fault of theOmagari fault. The permeability within the fault is alittle lower than that around the fault, and waterchemistry is not changed between the inside andoutside of the fault. The hydraulic head pressure at
the foot wall side of the fault is about 80 meters and it
recognized to be relatively higher compared withhanging wall side of the fault. From these results, thefault itself has lower permeability comparing with
intact rock around fault, and it has an ability tomaintain the hydraulic pressure (Fig. 7). But there islittle water chemistry change among hanging wallside, foot wall side and fault itself.

(2) Kami-horonobe site
In 2005, the Seismic reflection method was
conducted at the Kami-horonobe area where theoutcrop of the Omagari fault is located and the fault
lineament is well defined. Taking into consideration
the fault profile deduced from the results of seismicreflection, the borehole trace proposed to intersect thefault was planned. In 2006, this directional drilling
was started to verify the applicability of the drillingand measuring system. The borehole was drilled on abearing of S40W with a stable inclination of 35o from0m to 200m long. From 200m onwards, thedirectional drilling was relaxed to a shallower
inclination at 3o per 30m and the borehole reachedhorizontal attitude at the length of 720m. Drilling was
terminated at the length of 1000m after horizontal
drilling for 280 metres, as of 2011 (Fig.5). From 0m
to 200m drilling was conducted without coring andfrom 200m the cored drilling was performed and thecore recovery was almost 98% as of 2011, even in thefractured zone (Fig. 6).
From 2006 to 2013, measurement and logging in
the borehole such as WL-LWD, Water sampling andpermeability tests were conducted. Core logging,measurement and analyses were also carried out.
The WL-LWD was conducted at selected intervals
and permeability tests were attempted at the same
sections of 11 different depths. The color, hardness
and magnetic susceptibility of the core samples were
measured in-situ every 50cm and the rock core was
sampled every 10 metres for mineral analysis,
analysis for water chemistry, permeability test,

5.

Characteristics of the system

The CRIEPI’s directional drilling system has
following characteristics;(1) Applicable to soft rock: This directional drillingsystem can drill even in soft rock, because DHM is
attached at the wire-line downhole assembly andcasing rod can follow the down hole tools in order tocase the borehole.
(2) High core recovery: Rotational driving force islocated just above core barrel, so the wobbling of6

10th Asian Regional Conference of IAEG (2015)

Figure 7

Result of hydraulic test of HCD-3

core bit must be less than conventional drillingsystem. The MWD which is attached in the drillingassembly can monitor real-time drilling informationsuch as WOB, Torque and pressure, and theinformation is very useful for drilling.
(3) Exhaustive survey: Survey and logging
technologies such as LWD, hydraulic testing andwater sampling tool, in-situ rock stress measuring
tool, pressure meter and long term monitoring systemin the borehole which is drilled by directional drillingsystem have been developed, and these surveys cancover most geological characters necessary for site
selection of HLW disposal.
6.

(iii) Locality detecting technology: Wire-line MWD(iv) Logging and measurement technology: Wire-line
LWD, In-situ permeability test with geochemical
water sampling and Imaging, pressure meter, In-situ
stress measurement and hydraulic pressure
monitoring.
Based on the conceptual design, the sub tools
were manufactured and the drilling system wasconstructed by integrating these sub tools. Before
implementing the drilling system in the field, thetesting of the drilling system was carried out by
drilling artificial rock made from mortar at the
beginning of 2003.
Since late in 2003, the CRIEPI has been
conducting the in-situ directional drilling to verify theapplicability of the drilling, logging and measurement
system at Horonobe town. Since 2006 we have been
drilling the Omagari fault to estimate the fault
characteristics with an inclination change of 3o per
30m to the horizontal. During and after drilling, themeasurement and logging were carried out and thegeological,hydrological,
geochemical
andgeo-mechanical characteristics of the fault wereconcluded accurately.

Conclusions

CRIEPI have been conducting directional drilling
projects
withassociatedin-boreholelogging/measurement/monitoring technologies toverify the hydro-geological and geo-mechanicalconditions of the host rock at the potential waste
disposal candidate sites. In 2000, as the beginning
year of this project, we designed the concept of thedrilling and measurement systems, and manufactured
key tools concerning each technology. The element
technologies were selected based on following four
key technologies.
(i) Technology of well bending while drilling:
Downhole motor and Casing following system(ii) Core sampling technology: Wire-line triple tube
core barrel

Acknowledgements
This study was done under contracts awarded
from ANRE (Agency of Natural Resources andEnergy) of METI (Ministry of Economy, Trade andIndustry) and the in-situ drilling and survey was

710th Asian Regional Conference of IAEG (2015)

conducted as a collaboration work with the Horonobe
Underground Research Center of JAEA (Japan
Atomic Energy Agency, former JNC).

Kiho, K., Miyakawa, K., Suzuki, K., Ishiyama, T.,
Kubota, R. & Kawanishi, S., 2002, Development of
Directional
Drilling
Technology
inSoft
Sedimentary Rock, Proceedings of 9th congress ofInternational Association for Engineering Geology
and the Environment, 2061-2067.
Kiho, K., Miyakawa, K., Suzuki, K., Hayakawa, M.
& Masuhara, M., 2005, Development ofTechnology
forDirectional
Drilling
andMeasurement in the Borehole, Proceeding of 11th
Formation Evaluation Symposium of Japan.
Kitahara, S., Tani, T., Tsushima, N. and Ueno, H.,
2005, Application of directional drilling system togeological evaluation of the tunnel, Proceedings ofJapanese Association of Engineering Geology 2005,
183-186 (written in Japanese).
Nuclear Waste Management Organization of Japan,
2004, Evaluating Site Suitability for a HLW
Repository - Scientific Background and Practical
Application
of
NUMO’sSitingFactors,
NUMO-TR-04-04, 74.
Sumitomo Metal Mining Co., LTD., 1986, Wellman
Technique, Technical News of Kanto geotechnicalConsultants Association, 27, 14-17 (written in
Japanese).

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