Directional-Drilling-to-Multilateral-Drilling.pdf

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1. New Frontiers in
DirectionalDrilling
Drilling is a crucial part of field development.Operating
companies can only optimize hydrocarbon production
and recovery by drilling their wells in the best field
locations. In the past, drilling was as much an artas
a science. In many cases, drilling operations relied
on personal skill and judgment, with key decisions
being made with only a limited understanding of the
subsurface environment. Today, drilling engineers
can call upon a wealth of information and advanced
techniques that eliminate much of the guesswork that
characterized traditionaldrilling.
In this article, Sudhendu Kashikar reviews the latest
drilling methods and technologies, and examines how
they will shape futureoperations.

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he development of rotarydrilling
Tmethodsatthestartofthetwentieth
century provided the technical basis for
effective oil and gas exploitation and
therefore helped to establish the
modern oil and gas industry. For
decades, drilling operations were
controlled by a small number of experts.
These experts tried to interpret well
conditions during drilling and relied on
improvisation to overcome problems as
they arose. Those who had a detailed
knowledge of local geology and
understood the types of problems that
might be encountered in a specific
location usually achieved the best
results. However, success rates for wells
drilled under this traditional system
were highlyvariable.
The introduction of improved seismic
methods and tools for more detailed
reservoir characterization has given the
driller vital information about drilling
targets and the sequences above them.
These powerful techniques, when
combined with advances in drilling
technology, have led to rapid and
sustained improvements in drilling
operations. This gradual development
of tools and techniques has delivered
cost reductions, time savings, and
safetyimprovements.
Today, operating companies can
benefit from a new approach to
drilling operations, an approach that
reduces drilling risks, optimizes well
positioning, and provides consistently
high-quality results. The key to this
step change has been the emergence
of integrated drilling systems that link
procedures, people, and technology
to deliver better wellbores that are
placed more accurately inthe
reservoir, with reduced nonproductive
time. This level of performance is
achieved more quickly, at a lower cost,
and without compromising the safety
of thewell.
The number of directional wells is
growing every year, and many of these
are being drilled in more challenging
oilfield environments such asdeep
gas fields; carbonate reservoirs; high-
pressure, high-temperature zones;
and deepwater settings. There is also
an increasing demand for precision
directional drilling in mature oil
provinces, where operatorsare
performing infill-drilling campaigns to
extend asset life and maximize value
from existinginfrastructure.
Vision,understanding,
andcommunication
Drilling engineers wishing to improve
drilling efficiency, avoid potential
hazards, and optimize well placement
need a detailed understanding of
reservoir characteristics and how these
affect drilling operations in eachwell.
Data collection during drilling
enables rapid and effective
modifications to the drilling plan. As
fresh information is gathered, it can be
incorporated into the reservoir model.
This helps to ensure that the response
to unexpected developments is
appropriate. For example, thenew
technology enables engineers to adjust
well positions in real time. There are
three elements to real-time positioning:
vision technology that provides clear
images of the wellbore in real time;
interpretation facilities (for example,
iCenter* environments) wheredata
are gathered and processed for experts
to review; and connectivity between
office-based experts and their
colleagues at the wellsite (Figure1).
The value of real-time
measurements lies in being able to
review the changes as they happen
and then respond quickly to avoid
potential problems and minimize
their effect on the well. Continuous
monitoring enables field operators
to identify problems, make informed
decisions, and deal with any
unexpected situations that arise
duringdrilling.
Schlumberger Drilling and
Measurements has real-time support
centers in operations bases to
maximize the value of the information
recorded in the well. These centers
offer a range of data delivery and
interpretation options that operators
can access at any time. For example,
the operations support center in
Mussafa, Abu Dhabi, covers operations
in Oman, Qatar, United Arab Emirates,
and Yemen, and provides fast and
efficient support for customers such
as Abu Dhabi Company forOnshore
Oil Operations, Petroleum
Development Oman, Abu Dhabi
Marine Operating Company, and
Occidental PetroleumCorporation.
Some companies have taken the
monitoring and review process a step
further by introducing drilling iCenter
technology into their offices. By using
onsite centers, a company can provide
a collaborative environment for the
various disciplines to interact, and a
process for maintaining continuous
interpretation and reviewcapabilities.
An establishedtechnology
Drilling engineers have long
understood the potential benefits of
steering their wellbores. The world’s
first horizontal well was drilled near
Texon, Texas, USA, in 1929. In the late
1930s and early 1940s, wells were
drilled with horizontal displacements
of 30 to 150 m, and the world’s first
multilateral well was drilled in the
Soviet Union in 1953 (Figure 2). By
1980, the Soviet Union had drilled
more than 100 multibranch horizontal
wells, including exploration,
production, and injectorwells.
By the mid-1980s, drilling
techniques had advancedsignificantly,
but were still very different to those
that can be applied today. In the
1980s, wells were drilled without the
benefit of synthetic-base mud, top
drives, steerablemotors,
polycrystalline diamond compact bits,
or computers. Without these key tools
and technologies, there were many
problems for the directionaldriller
toovercome.
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350 horizontal wells in 33 different
oil and gas fields. At the same time,
European offshore successes with
directional drilling in the North Sea
encouraged oil and gas companiesto
apply directional technologies to land-
based drilling. Today, horizontal wells
have been drilled in every oil and gas
basin, and the technology is so
efficient at extracting oil and gas that it
has become a standard industrytool.
Modern directional drilling methods
are cost-effective and extremely
versatile, and they offer significant
advantages over vertical drilling for
the recovery of oil and gas. Horizontal
wells, for example, can improve
production and increasereserves
by intersecting natural fractures that
cannot be accessed with vertical wells.
This delays the onset of water or gas
coning so that more oil is produced,
and production from thin or tight
reservoirs and waterflood sweep
efficiency are improved (Figure3).
Rotary steerablesystems—a
newdirection
The introduction of rotary steerable
systems (RSS) in 1997 marked a
major milestone for drilling
technology. The fully rotating
drillstring soon proved more stable,
less prone to sticking, and better able
to facilitate hole cleaning and wall
smoothing than conventionalsystems.
Before the arrival of RSSs, wells
were drilled using a rotating mode
for straight sections and a sliding
mode for curved sections. Drilling in
the sliding mode was effective for
steering, but inefficient, as it slowed
the rate of penetration (ROP) and
produced poor-qualitywellbores.
This mode of drilling was a key
obstacle that needed to be overcome
when optimizing directional drilling
performance. The emergence of RSS
technology delivered the benefits that
drilling engineers hadanticipated.
Figure 1: The real-timecyclepromotes
continuous review and refinement of
drilling operations.
These advances in technology and
interpretation capabilities have given
the driller the tools and the
mechanisms necessary to reduce
drilling risk and optimize well
placement beyond what was possible
just a few years ago. Greater
connectivity, and the secure data
access that this allows, has been a key
factor in these advances and will lead
to profound changes in the drilling
sector for years tocome.
Figure 2: Well 66/45, drilled at Bashkiria, now
Bashkortostan, Russia, was the first multilateral
well. It had nine lateral branches that tapped the
Ishimbay fieldreservoir.
During the 1980s, directional drilling
was difficult and comparatively costly.
As a result, it failed to achieve broad
acceptance within the industry. Slant-
hole drilling was the first directional
technique to be widelyadopted.
Between 1982 and 1992, more than
1,000 slanted or angled wells were
drilled, primarily in Canada, Venezuela,
and China. The 1990s upsurge in
exploration activity saw a sustained
interest in horizontal drilling, and the
technique emerged as the preferred
option for production wells in
countries such as Oman, Canada, and
the USA, and in areas like the North
Sea. Between 1990 and 1998,
Petroleum Development OmandrilledFigure 3: Horizontal wells offer a range of productionbenefits.
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3. Accurate andpowerful
The PowerDrive* RSS is a compact
system, comprising a bias unit and a
control unit, that adds only 3.8 m to
the length of the bottomhole assembly
(BHA) (Figure 4). The bias unit sits
immediately behind the bit and
applies force to the bit in a controlled
direction while the entire drillstring
rotates. The control unitcontains
self-powered electronics, sensors, and
a control mechanism to provide the
average magnitude and direction of
the bit-side loads that are used to
adjust welltrajectory.
The bias unit has three external,
hinged pads that are activated by
controlled mud flow through a valve.
The valve exploits the difference in
mud pressure between the inside and
the outside of the bias unit. The
three-way rotary disk valve actuates
the pads by sequentially diverting
mud into the piston chamber of each
pad as it rotates into alignment with
the desired push point—the point
opposite the desired trajectory—in
the well (Figure5).
Once a pad has passed the push
point, the rotary valve cuts off its mud
supply and the mud escapes through a
specially designed leakageport.
Each pad extends no more than
approximately 0.95 cm during each
revolution of the bias unit. An input
shaft connects the rotary valve to the
control unit, and this regulates the
position of the push point. If the angle
of the input shaft is geostationary
with respect to the rock, the bit is
constantly pushed in one direction,
the direction opposite the push point.
If no change in direction is needed,
the system is operated in a neutral
mode, with each pad extended in
turn, so that the pads push in all
directions and effectively cancel each
otherout.
Improved drilling methodsproduce
betterwells
Fully rotating steerable systems have
been tested and shown to minimize
problems such as wellbore spiraling
and ballooning. RSS systems optimize
the efficiency of cuttingstransport
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and reduce the risk of sticking. Other
studies indicate that using an RSS
reduces stress on logging-while-
drilling (LWD) systems and cuts bit
wear. Good design and an effective
RSS will minimize or eliminate
undesirable effects such as bounce,
stick-slip, whirl, and lateral vibration.
Fully rotating the entire steering
system
◼reduces mechanical and differential
sticking of the drillstring because
there are no stationary components
in contact with the casing, whipstock,
or borehole. It also reduces the risk
of the BHA packingoff.
◼improves penetration rates because
there are no stationary components
to create friction. The efficient
removal of cuttings means that
cuttings are not reground during
drilling.
◼enhances the flow of drilled cuttings
past the BHA because there are no
annular bottlenecks in thewellbore.
Enhancedproduction
The ability to land and position
wellbores more precisely within the
reservoir leads directly to better
production. The more sophisticated
RSSs, which have automated, closed-
loop control of the steering response,
can position wells more precisely than
even the very best directional driller
could using conventional technology.
This ability to land and navigate wells
precisely within the best production
zones provides an immediate benefit
for improving the production
performance of the well.Straighter,
cleaner wellbores improve the flow
rates for hydrocarbons by eliminating
water sumps and gas crests (Figure6).
Improved reservoir access anddrainage
In areas where three-dimensional
directional drilling control is
troublesome, RSSs can provide a much
wider range of well-trajectory design
options at low operational risk. This has
proved particularly beneficial in fields
where a lack of directional drilling
control had limited well designs to
simple, two-dimensional wells and thus
restricted reservoir access and field-
drainage patterns. With the
introduction of rotary steerable drilling
techniques to these fields, producible
reserves are increased through
improved reservoir access and more
efficient drainagepatterns.
Minimized lost-in-holetime
Continuous pipe rotation, smoother
and less tortuous trajectories, and
overall improvements in hole-gauge
quality help to reduce stuck-pipe
and lost-in-hole incidents. A study
comparing lost-in-hole incidentsfor
RSSs with those for conventional BHAs
showed the RSS lost-in-hole rate was
only 15 % of that experienced with
conventionalsystems.
Improvedsafety
When drilling programs are conducted
with RSSs, fewer trips in and out of
hole should be required. RSS methods
extend the life of drill bits, which
results in more footage per bit and,
therefore, fewer trips for bit changing.
In addition, continuous rotation at high
rotary speeds results in very efficient
hole cleaning and removes the need
for many short cleaning trips. RSSs
are also much more versatile and
should be able todrill
all of the required section trajectories
(such as build, drop, tangent, and
turn) using a single BHA design; this
means fewer trips for BHA change.
This dramatic reduction in tripping
saves time, reduces drill-floor activity,
cuts handling of tubulars, and,
ultimately, increasessafety.
Reduced tripping activity can be
measured by plotting the footage
drilled against the total amount of pipe
tripped over the course of a project. In
some cases, the introduction of RSSs
has reduced tripping by almost 50%.
Reduced environmentalimpact
Drilling with rotary steerable
assemblies results in a more in-gauge
hole than drilling with steerable motor
systems. This gives smaller volumes of
drilled cuttings waste andlower
drilling fluid losses. For example, if the
hole in a 121⁄4-in section were drilled
overgauge to an average diameter of
14 in, this would represent an increase
of about 30 % in cuttings waste and,
correspondingly, a 30 % lower annular
velocity compared with drilling the
section in gauge (Figure7).
All of the RSS-related improvements
listed combine to deliver time savings,
improved safety performance, and
greater cost efficiencies that translate
into lower production costs for field
operators (Figure8).
Figure 4: The PowerDrive RSS produces high-quality boreholes at high ROPs.
Figure 6: Conventional drilling technology produces tortuous wells. In horizontal producers, this can restrict the flow of hydrocarbons (a). Flow rates are
maximized when the borehole is smooth and straight(b).
Figure 5: Actuators push against the side
of the borehole to steer the RSS.
Figure 7: Wells drilled overgauge generate
more cuttings waste and are drilled at a lower
annularvelocity.
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The tools for thejob
Drilling technology must be flexible
and enable the engineer to design and
execute the most appropriate drilling
program for any well. There are often
considerable variations across oil-and
gas-bearing formations. Even adjacent
wells may be significantly different, and
each can exhibit unique temperature,
pore-pressure, permeability, and
lithological conditions. The industry
needs an integrated drilling system that
can be adapted to these local variations
and that will meet the specific needs of
eachcustomer.
For example, the PowerDrive
Xceed* RSS has been designed to
excel in harsh environments. It is a
fully rotating tool that provides high
levels of accuracy and reliability in
extreme drillingapplications.
Maersk Oil Qatar AS used the
PowerDrive Xceed system to drill thin
sands in the Nahr Umr reservoir in
Qatar (Figure 9). The system
provided excellent geosteering
control, with the bit staying in the
sand section through 99 % of the
2,006-m, 81⁄2-in hole. More than 90 %
of the drain section was drilled within
the optimum sand zone, and, during
this operation, the systemachieved
a significant 90-degree change in well
trajectory azimuth at an extended
step-out. This level of performance
has proved very difficult to achieve
with conventionaltechnology.
Reliability and wear resistance
are key features indemanding
environments. The PowerDrive Xceed
tool has a totally enclosed internal
steering mechanism and rugged, field-
proven electronics thatsafeguard
the tool’s performance in abrasive,
hot, and high-shockapplications.
The reduced dependence of the
steering principle on wellbore contact
makes the tool ideal for openhole
sidetracking steering in overgauge-
hole and soft-formation applications.
Minimal wellbore dependence also
enables the PowerDrive Xceed system
to be used with bicenter bits for
directionaldrilling.
The nextstep
As the exploration and production
industry extends its operations into
new areas, there is increasing pressure
on service companies to provide tools
with higher levels of reliability that can
complete demanding drilling programs
quickly andcost-effectively.
The availability of near-bit
measurements in real time ensures
accurate, efficient drilling and
wellbore placement. The efficient
downlink systems and the automatic
inclination hold provide a smooth
tangent section and improve the
accuracy of the true vertical depth
in the horizontal section—critical
for maximizing recoverable reserves
and the well’s productionpotential.
A measurement-while-drilling
(MWD) type triaxial sensor package
close to the bit provides accurate
azimuth and inclination directional
information, which enables fast,
responsive directional control in
either the automatic or the manual
operation mode. Once a target
formation has been penetrated, the
trajectory can be locked in using the
inclination-hold functionality. No
further input is required from the
directional driller. Steering decisions
are further aided by an optional
real-time azimuthal gamma ray
measurement and imaging of the
wellbore to provide information on
formation dip or fault boundaries. An
azimuthal gamma ray sensor 2 m
from the bit enables drillers and
geologists to identify bed boundaries
quickly and thus respond faster to
formation changes in order to
optimize well placement. Casing and
coring point detection are optimal,
penetration of the formations to be
cored is minimized, and the chances
of drilling through a potentially
valuable core section or wastingtime
coring an uninteresting formation are
significantlyreduced.
High-performancedrilling
with amotor
When a PowerPak* steerable mud
motor is run in conjunction with a
PowerDrive system, all of the drilling
energy is concentrated at the bit. This
configuration can improve the ROP,
eliminate slip/stick andunpredictable
Today, drilling systems are being
deployed in tough conditions, such
as deep, hot wells, where they are
expected to deliver better images
and more accurate data. Precision
drilling and field optimizationrequire
excellent depth control and smoother
holes that pass into the productive
pays of any target zone and remain
withinit.
When providing directional drilling
services, it is usually preferable to
drill from shoe to total depth in one
run, every time, at maximum ROP.
The PowerDrive X5* RSS was
developed to meet these challenges.
This system represents a step change
in reliability and efficiency that makes
it possible to drill longer runs,
optimize wellbore placement, and
reduce drilling time. The associated
cost savings can besubstantial.
The PowerDrive X5 system has a
robust steering section and utilizes
advanced coating materials that
reduce wear and so ensure reliable,
consistent performance in a wide
range of drilling environments. The
system’s electronics, which are
chassis mounted for reliability and
durability, can operate in downhole
temperatures of up to 150degC.
High-quality drilling is achieved using
a simple, rugged steering section and
directional measurements near the
bit for precise, true-vertical-depth
directionalcontrol.
torque,minimizedoglegseverity,drill
asmootherhole,andincreasebitlife
(Figures10and11).
PowerPak* steerable motors are
positive displacement mud motors
that incorporate a stabilizer and a
bent-housing section that permits
rotary drilling in vertical, tangential,
or horizontal sections of the hole as
well as oriented drilling during
kickoffs or course corrections. The
surface-adjustable bent housing
provides flexibility as orientation
requirementschange.
The PowerPak motor’s modular
design meets a full range of directional
drilling requirements. The superior
design of the tool features short bit-to-
bend and bit-to-stabilizer spacings to
enable high surface rotary speeds for
improved holecleaning.
Formationevaluation
whiledrilling
Two decades ago, formation
evaluation was usually conducted
using wireline tools that were
introduced to the borehole once
drilling had been completed.The
Figure 9: The thin sands of the Nahr Umr
reservoir in Al-Shaheen field were drilled using
a PowerDrive Xceedsystem.
Figure 8: The key features of the PowerDrive system. Precise deviation control, continuous rotation,
and improved hole cleaning all lead to lower productioncosts.
Figure 11: Short bit-to-bend and bit-to-stabilizer spacings enable high surface rotary speeds and improve hole cleaning.
Figure 10: The principle of the mud motor.
delay between drilling andlogging
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meantthattheresultsfromwireline
logshadtobecorrectedforinvasion
andotherpostdrillingeffects.
The Schlumberger LWD tool
was introduced in 1988. The basic
measurements wereresistivity,
neutron and density porosities, and
photoelectric factor. By the early
1990s, improvements had been made
in areas such as tool reliability and
data-transferrates.
Further advances included the
introduction of the IDEAL* Integrated
Drilling Evaluation and Logging system,
which enabled drillers to monitor
trends and spot abnormal situations
using quick-look interpretations on a
drill-floor screen, and the arc5* Array
Resistivity Compensated tool, which
proved extremely useful in thin-bed
environments.
Thisdevelopmentprocesshas
continuedwiththearrivaloftwo
newmeasurementsystems,the
seismicVISION*seismic-while-drilling
service and the proVISION* real-time
reservoir steering service tool, which
provide detailed formation evaluation
information during drilling. This
information has changed the ways
that wells are drilled and reservoirs
aredeveloped.

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Reduce depth uncertainty with
real-time boreholeseismic
The seismicVISION LWD tool delivers
time-depth/velocity information in
real time without affecting drilling
operations. The tool helps operating
companies to make the best drilling
decisions, while reducing costs and
improving safety. The seismicVISION
tool delivers traditional borehole-
seismic measurements, including real-
time checkshot and interval velocity
data, that reduce the uncertainty of
events ahead of the bit. Real-time
access to these calibration data is
critical where there are significant
uncertainties in the time–depth
relationship or in wells where casing
must be set in an interval identified by
surface seismicdata.
Continuously updating the bit’s
position on the seismic maphelps
in navigation, selection of casing and
coring points, prediction of target
depth, and reduction of sidetracks and
pilot holes. Acquired interval
velocities provide the necessary data
to manage pore pressure while drilling
and to optimize mudweight.
Real-time producibility information
whiledrilling
The proVISION nuclear magnetic
resonance tool helps oil and gas
companies to optimize productivity.
This tool represents a step change
in how nuclear magnetic resonance
technology is applied to formation
characterization. The proVISION
tool delivers real-time evaluation of
formation productivity, andprovides
reliable determinations of mineralogy-
independent porosity, bound-and
free-fluid volumes, productive zones,
and pore size, as well as the
identification of fluids (Figure12).
techniques will help operators to
reduce risk and overcome some of the
geological uncertainties encountered
while drilling complexwells.
Ultrahigh telemetry rates (up to
12 bps) have been used tooptimize
horizontal well placement and to warn
of wellbore stability issues before they
jeopardize operations or impact on
drilling costs (Figure 13). Transmission
of high-quality, real-time azimuthal and
image log data is possible, even in cases
where penetration rates arehigh.
Resistivity images are transmitted
uphole to present the wellbore in four
quadrants. This information can be
wrapped into a 3D image of the
wellbore, which helps the drilling
team to optimize well placement using
geological markers. Armed with this
information, the drillingengineer
can make rapid adjustments to the
wellbore trajectory, relative to
geological bedding planes or faults,
and can modify steering whiledrilling.
Wellbore stability problems are
detected using ultrasonic caliper
logs from density LWD tools. Hole
enlargement or washouts can be
identified while drilling or during
subsequent trips. This helpsto
monitor wellbore stability and enables
adjustments to be made to mud
weights or effective circulating
density as required (Figure14).
Wellbore stability problems can be
confirmed using VISION* Formation
Evaluation and Imaging While Drilling
technology that incorporates
azimuthal density/neutron viewer
software, which provides density-
image and caliper data whiledrilling.
The azimuthal density/neutron
viewer also generates 3D images and
caliper logs that, when combined,
make it easier to understand wellbore
conditions during drilling. In addition,
the 3D density images and ultrasonic
caliper information enable engineers
to characterize wellbore instability
mechanisms and then resolve them.
This is vital in completions where
gravel packs or expandable screens
are required. The ultrasonic and
density caliper information gathered
during drilling can indicate whether
the hole quality is good enough for
engineers to deploy specialized
completions. Log data acquiredon
a subsequent wiper trip provides a
clear picture of hole enlargement and
stress failures afterdrilling.
Thebigpicturefromtheborehole
Although LWD and MWD tools have
been available for many years, it is
only recently that advances in data
transmission and interpretation have
progressed to generating accurate
images of the wellbore. These images
are based on real-time data and offer
insight into what is really happening
downhole.
Typically, a high-quality image is
drawn from detailed, 3D resistivity
data. A resistivity tool similar to the
wireline-deployed FMI* Fullbore
Formation MicroImager tool supplies
these data. The resistivity tool is
capable of identifying wellbore
features and characterizing faults,
cementation changes, and threaded
or spiraling boreholes caused bybit
whirl. Software converts the
resistivity data into 3D wellbore
images that can be viewed from any
angle using simple mouse movements.
The resistivity measurements are
transformed into 56 azimuthal sectors
around the circumference of the
wellbore to provide extremely
detailedimages.
Current imaging-while-drilling
technology is sufficiently fast and
accurate to facilitate geosteering
while drilling. Modern software and
MWD telemetry systems provide a
clear insight into 3D wellbore
features, well placement within the
reservoir, wellbore stability issues,
formation dip, and structural
configurations. Combining resistivity
and density services with real-time
logging images andgeosteering
Figure 13: High data-transmission rates enable drillers to control wells with high ROPs.
Figure 12: The proVISION tool clearly identifies hydrocarbon layers, rock porosity, production zones,
and bound-and free-fluidvolumes.
Figure 14: LWD tools can help drilling engineers to modify mud weights and so avoid
problems such as kicks and fluid loss.
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Figure 16: Every well can present problems for the drilling engineer. Understanding the potential risks and where problems might occur helps to keep the
drilling program on schedule.
Whatcouldpossiblygowrong?
Oil and gas companies spend around
USD 20 billion on drilling each year.
Unfortunately, about 15 % of this is
attributed to losses. These losses
include materials such as drilling
equipment and fluids, and deficiencies
in drilling process continuity (called
nonproductive time) that are incurred
while searching for and implementing
remedies to drillingproblems
(Figure 15). Avoiding drilling problems
cuts finding and development costs
and enables oil companies to focus on
their core business—building and
replacingreserves.
Every well presents problems: the
main challenge for drilling engineers
is to manage the drilling risk in a way
that prevents small problems from
escalating. Most of the time spent
drilling wells, and most of the cost, is
associated with cutting down
through the rock sequence above the
reservoir. Knowing what the
potential risks are and where they
are likely to occur helps to keep the
drilling program onschedule.
There are various problems that can
trouble drilling engineers (Figure 16,
a–n). For example, drillpipe can
become stuck against the borehole
wall through differential pressures or
by lodging in borehole irregularities;
skill and force are required to free it.
When sticking cannot be resolved, the
only solution may be to abandonthe
stuck portion and drill a sidetrack
around it. This changes the drilling
program completely and may
significantly increase the well’scost.
Drilling at high ROPs can save time
and money, but when this high rate is
accompanied by a low drillstring
rotation rate or a mud flow rate that
fails to lift rock cuttings to surface,
the result is stuckpipe.
The faults and fractures that the
wellbore encounters open conduits
for loss of drilling fluid to the
formation. Excessively high mud
pressure can fracture the formation
and cause lost circulation. However,
if the mud pressure is too low, it will
fail to keep high-pressure formations
under control and can lead to gas
kicks orblowouts.
g. Poor holecleaning h. Wellboregeometry
a.Cement b.Collapsed c.Differential d.Drillstring e.Fractured f.Geopressure i.Debris j. Keyseating k.Mobile l.Reactive m.Unconsolidatedn.Undergauge
related casing sticking vibration zone formation formation zone hole
Figure 15: Offshore drilling costs are high, and problems that take days to solve will have major
implications for field-developmentbudgets.
Drillstring vibrations can weaken
and destroy pipe and equipment as
well as seriously damage thewellbore.
And some problems, even ifthey
do not completely suspend the drilling
process, jeopardize subsequent
logging, completion, andproduction.
Drillers who have to decide how best
to correct these problems face tough
challenges: there are many factors for
them to consider. For example,
increasing the mud weight to control
wellbore stability in one interval in a
well may cause fracturing elsewhere.
Often, the most effective solutions
cannot be widely applied, as many
drilling-related problems are well-or
field-specific. The key to successful
drilling is to develop a soundplan,
to update this continuously as new
information becomes available,and
34 35Middle East & Asia Reservoir Review Middle East & Asia Reservoir Review
to inform all the relevant personnel.
The plan must include procedures to
follow under normal circumstances
and methods for dealing with the most
likely and the most severe problems
that could beencountered.
Despite these challenges, successful
drilling should be a routine process for
properly trained personnel who are
following a well-defined drilling
procedure and who have sufficient
data and tools forinterpretation.

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Right firsttime
As with all oilfield operations, drilling is
an activity that field operators want to
complete quickly and cost-effectively.
The keys to avoiding problems while
drilling are assessing and managing
risk, and optimizing wellbore
construction through detailed
planning and real-time monitoring
during the execution phase. Predrilling
analysis and prediction, with real-time
updating as drilling progresses, enable
the drilling engineer to anticipate
potential problems ahead of time and
to solve them proactively. No Drilling
Surprises (NDS) is a focused process
that covers all aspects of well planning
and execution, and delivers relevant
information to the appropriate
personnel at every stage in thedrilling
operation. There are three phases in
an NDS project, see Figure18.
Continuous updating of the living
well plan helps the asset team to
ensure that drilling decisions are
based on accurate and up-to-date
information and that they will not
compromise hydrocarbon production
recovery, orsafety.
Technologies tomeet
keychallenges
Growing market demand has created
a broad spectrum of drilling services.
Today, leading service companies are
investing heavily in their own research
and development to keep pace with
industry needs and are participating in
collaborative efforts with their
customers. New products andservices
are being introduced to fill the gaps
in drilling-services packages, and
companies are starting to integrate
drilling data with seismic, logging,
production, and other reservoirdata.
This integration has led to benefits in
areas such as stimulation, completions,
and productionoptimization.
Balancingcostsandbenefits
Many operators, while acknowledging
the technical advances that have been
made in drilling, would like to see more
technology aimed directly at reducing
costs. Although costs appear to be
falling in many areas, for example,
software, well costs are not coming
down. In real terms, some wells cost
more today than they would have done
5 or 10 years ago. However, these
higher costs do reflect thetechnical
Figure 18: The three phases in an NDS project. Careful planning, live monitoring and updating during drilling, and detailed postjob analysis can help to
eliminate drilling problems before they arise.
Real-time dip information, provided
by the LWD resistivity imaging tools,
can be used to view geological
structures and reduce the uncertainties
in earlier geological models. Production
teams can also analyze surface seismic
data to establish the presence or
location of erosion surfaces that might
jeopardize the well trajectory. Data
transmission from the rig site enables
experts to observe the wellbore
remotely and to anticipate changes in
the bedding plane and the structural
behavior of thereservoir.
Azimuthaldensity/neutronviewer
softwarealsoenablesstructuraldip
pickingfromimages.Thiscanbe
used in combination with the real-time
data for structural interpretation. Bed
dips and layer thickness are also
characterized for the evaluation of
structural cross sections. The reduction
in risk and geological uncertainty will
make wellbore imaging an essential tool
for companies operating in geologically
complexfields.
LWD VISION tool eliminates the
need for a pilothole
The VISION drilling tool has helped to
save time and reduce costs by enabling
several operators worldwide to drill
deepwater production wells without
first drilling a pilot hole. The geological
drilling campaigns used real-time LWD
images and bit resistivity data to land
the well in thereservoir.
Accurate well steering and
placement require significant prejob
planning in order to minimize drilling
risks while steering using geological
criteria. The use of LWD images in
real time was a key element in
predicting undesirable events that
might otherwise have jeopardized the
success of the project. In this well,
subseismic faults and premature
entry into the shale zone occurred.
The interpretation of the available
log and image data was critical to the
decision-making process during
drilling and ensured reentry into the
reservoir.
The path to betterwells
Drilling optimization and the benefits
it brings cannot be achieved through
tools and technology alone. Drilling
and production engineers require risk-
management systems to help them to
optimize wellbore construction and
performance, and to learn the lessons
from previous drilling programs. This
approach requires detailed planning,
real-time control during execution of
the drilling plan, and a method for
reviewingperformance.
The first challenge for a new drilling
program is to link all therelevant
expertise. This means that all parties
can observe the well’s progress in real
time and that the drilling engineer has
the full support of an expert team,
should the well encounter any
difficulties. Modern connectivity
systems such as the InterACT* real-
time monitoring and data delivery
system make this possible by linking
remote locations to field offices and
corporate headquarters through
secure Internet and intranet
connections (Figure17).
Figure 17: The InterACT real-time monitoring and data delivery system provides secure monitoring
and control.
Downhole
monitoring
Wireline
logging
Production
monitoring
Stimulation
operations
Drilling
operations
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understandingofthereservoirand
itsproduction,itcanoptimizewell
placementandselectthebest
perforation zones or drillingtrajectories.
Over the next decade, worldwide
oil demand is projected to increase
significantly, especially within the
developing economies (Figure 21).
Published estimates indicate that the
reserves to meet this demand are
available, but that they are thosethat
are usually more difficult and costly to
produce. Reserves located in remote or
challenging environments such as deep
water or environmentally sensitive
regions, or those that are considered
nonconventional such as coalbed
methane or heavy oil will require
substantial research and development
to devise suitable extraction solutions
(Figure 21). The key to successwill
be finding economically viable methods
to tap those reserves, despite the
increased technical complexity that
will benecessary.
Recent advances in wellbore-
construction and production-
enhancement techniques have been
key contributors in this drive to meet
technical challenges while reducing
costs. Until now, the demand for
stimulation services has been largest
in North America, but demand is
rising quickly in other parts of the
world. Even in the Middle East, which
contains many of the world’s most
prolific reservoirs, depletion and
production problems arestarting
to affect field performance and
production-enhancementservices
are being investigated.Interest
in unconventional resources is
increasing globally, a sure sign that
easy oil and gas production may soon
be a thing of thepast.
Reaching further, drillingsmarter
As operators locate satellite fields
and bypassed zones around a main
reservoir, they may seek to develop
these with extended-reach wells.
However, for extended-reach wells
to succeed there must be a careful
assessment of risk. Extended wells
can reach under urban centers or
protected wilderness sites to tap oil
and gas that would be inaccessible
using any otherapproach.
Figure 21: The steep rise in global oil demand will be driven by countries in the developing world.
Figure 22: As conventional oil production peaks, other sources of hydrocarbons, such as heavy oils or
coalbed methane, will have to be tapped to meetdemand.
achievements of recent years, as
the industry drills deeper and more
complexwells.
Well construction costs may be
rising, but the aim of reservoir
development technology is to
optimize reservoir exploitationusing
a few advanced wells that significantly
outperform theirconventional
counterparts. Nowhere has this
been illustrated more clearlythan
in Russia, where a field development
plan for 57 vertically drilled wells was
recently scrapped in favor of two
geosteered horizontal wells. Thetotal
field production from the original plan
was estimated at about 2,000 m3/d
with a 19-year life. Productionfrom
the two designer wellstotals
5,000 m3/d and depletion is expected
in 7.6years.
Brownfielddrilling
Today, most of the world’s oil
production comes from mature fields
(Figure 19), and some of these
brownfield assets are over 30 years
old. The industry is working hard to
prolong the lives of these fields, to
optimize production from them, and
to improve recovery factors through
remediation and production-
enhancement technologies.However,
there are many technical and economic
challenges to be overcome in mature
and brownfields. In these fields, drilling
expenditure must be justified by the
value of the incremental production
from the asset (Figure20).
In recent years, significant progress
has been made in this area by
developing technologies designed to
combat the decline of older fields and
to add capacity for thefuture.
Once the company operating
a brownfield asset has aclear
Figure 20: The key challenges in brownfield development are to reach
bypassed oil cost-effectively and to avoid collision with existing wells.
Figure 19: Brownfield production dominates global oil and gas supply.
Sources: Energy Information (EIA). Office of Energy Markets and End Use, International Statistics Database
and International Energy Annual 1999, DOE/EIA-0319(99) (Washington, DC, February 2001) EIA. World Energy
Projection System(2002).
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The wayahead
The demands of modern oil and
gas exploration will continueto
shape the drilling-services sector. In
mature and marginal fields, operating
companies expect complex wells,
excellent reliability, and low drilling
risks at reasonable costs. As a result,
manufacturers and service suppliers
will have to continue to improve their
technology and provide more efficient
equipment throughout every area of
the drilling process. To achieve this
goal, manufacturers and service
companies will have to work in close
cooperation with customers to answer
their specificneeds.
Collaborating withcustomers
There are many examples of
collaborative projects for developing
new technologies and processes
with customers. For example,
Schlumberger Drilling and
Measurements is currentlyworking
with BP and Shell on a through-tubing
RSS that is designed to reduce the
costs of sidetracking from existing
wells and to reach small pockets of
hydrocarbons in maturefields.
In the drilling sector, the key to
business success is the ability to drill
wells efficiently and safelywhile
providing maximum environmental
protection. Operating companies
and regulatory authoritiesset
these standards as part of the field-
development plan, and any service
company that cannot reach the
required standards is unlikely to
form a long-termpartnership.
Future advances in tools and
techniques will be driven by the
needs of customers. Oil and service
companies that can establish and
maintain business relationships over
several years are more likely to
optimize drilling performance and so
generate time and costsavings.
Leading operators have found that
they can benefit from synergy when
modern workflowprocesses
are applied by highly trained and
experienced members of the drilling
team operating within a customized
businessmodel.
Peoplemakethedifference
The introduction of instrumented
drilling systems, including surface
and downhole components, has had
a beneficial effect on the drilling
community. This step change in
technology made it necessary to
implement radical training programs
to teach personnel how to get the
best from the new equipment.As
drilling engineers gained experience
and confidence in applying the new
drilling practices, they were prepared
to conduct drilling programs that
were more technicallydemanding.
Drilling, like any other technology,
will continue to develop. Engineering
capabilities will become increasingly
important as the reservoir targets
become harder to drill and technology
offers further opportunities for
efficiencyimprovement.
People also play an increasingly
critical role in developing new
business models. The last few years
have seen evolution in the way that
service companies—particularly
drilling-services providers—work with
their customers. In some areas, the
traditional short-term client–supplier
relationship persists. In areas where
work is seasonal and activity is
variable, this may be the only sensible
way of working. However, many
operators have been trying to enter
into more comprehensive and long-
term relationships, particularly where
the work scope is larger and more
consistent. This approach benefits the
oil company and the supplier, who can
become a drilling partner rather than
an equipment and servicevendor.
As the industry moves forward, an
important consideration is more risk
sharing and collaboration in order to
ensure that solutions are provided for
today’s and tomorrow’schallenges.
Leading service suppliers are
investing heavily in new technology
and processes, and in personnel
development for addressing these
challenges. To continue this process,
and potentially raise investment
levels, requires servicecompanies
to find opportunities for collaborating
with their customers, particularly
when they will be rewarded for the
value they bring through improved
drillingperformance.
Extended reach in the South ChinaSea
Phillips China Inc. and its partners,
China National Offshore Oil Company
and Shell China, discovered the
Xijiang 24-3 field in the South China
Sea in 1994 (Figure 23). The
operators drilled several wells to
different producing horizons and put
them on production. Smaller, satellite
reservoirs, such as Xijiang 24-1, were
not drilled because the estimated
production would not support the
costs associated with a separate
platform or drilling subseawells.
economicsdictatedthateverynew
wellshouldproduceoiltocoveror
offsetdrillingcosts.
The first proposed bottomhole
location was over 8 km from the
platform, and meeting the objectives
of this well would require going
beyond the range of normal
development drilling. Ultimately, an
extended-reach well was directionally
drilled, to a then world-record
measured depth of more than 9,200 m,
while using real-time LWD services to
provide formation evaluation in a
timely and cost-effective manner. The
success of this well led to an extension
of the drillingcampaign.
Subsequent wells, while not reaching
as far from the platform, used LWD
sonic and resistivity logging tools to
provide real-time seismic correlation,
porosity data, and hydrocarbon
evaluation. These data enabled the
operator to optimize costs and make
decisions much morequickly.
Dramatic rise in drilling efficiency
for Middle Eastoperator
In the Middle East, Schlumberger has
helped one operator achieve a 52 %
(USD 1.5 million) reduction in total
well costs. This resulted primarily from
a 91 % increase in drilling efficiency
per bit run, which persuaded the field
operator to replace conventional motor
technology throughout the company’s
ongoing field program with the
PowerDrivesystem.
During the second phase of the
multiwell program, the operator
needed increased ability to overcome
obstacles in the highly faulted and
laterally variable sandstone reservoir.
Nearly 90 % of these wells required
openhole sidetracks for geological
realignment. The available seismic data
defined the heavily faulted area, and
sidetracks were imperative. Steerability
and directional control in loose sands;
geosteering between different sand
layers; abrasion; excessive wear; and
hole cleaning were among the obstacles
to beovercome.
The PowerDrive Xceed system
met the challenge andexceeded
expectations on cost and time savings.
Reduced wellbore tortuosity cut trip
time by 68 %—a direct result of
improved hole quality. Theoperators
used the PowerDrive Xceedsystem
to drill the longest well in the field and,
for the first time, managed to drill the
sandstone section (4,172 m) in onerun.
Reliable toolsand
clearerpictures
Drilling places tough demands on
tools. For Schlumberger, tool reliability
has been a priority for manyyears.
Every downhole tool that the company
develops is subjected to an intense
testing program that simulates the
severe shock, bending,vibration,
and temperature cycles it will
encounter in the well. By using
sophisticated test methods, new
tools can be subjected to a lifetime of
downhole stress in just a fewdays.
Only tools that pass these tests are
released to the field. Tool reliability is
vital and helps to boost performance,
but not all of the improvements in
drilling operations are madedownhole.
Schlumberger is working in close
cooperation with operating companies
to develop and introduce 3D
visualization rooms for integrated well
planning and remote support through
real-time data transfer and virtual-
reality technology (Figure 24). Some
operating companies are using
software packages that help them to
produce integrated well designs that
bring geophysicists, geologists, and
drilling engineers together towork
on the same model. This enables the
team to identify zones of interest,
select targets, and work on the well
path in an integratedprocess.
Real-time visualization and the use
of secure Internet links, such as the
InterACT system, also enable
companies to identifypotential
problems before they affect production.
Operating companies that use virtual-
reality systems for well planning report
these have led to optimized designs
that help to save time andmoney.
Visualization technology has a proven
track record and is constantly under
development. For many companies, the
major challenge is not introducing the
systems, but modifying the way that
departments and individuals interact—
changing the ways in which they work
and learntogether.
Figure 24: Advanced visualization facilities enable field operators to assessreservoirconditions
within a multidisciplinaryframework.
Figure 23: Extended-reach drilling opens up
smaller satellite fields at a fraction of the cost
of traditional field development methods.
Production from the Xijiang 24-3
field indicated that the booked
reserves understated the actual
amount of oil in place. Revised maps
and seismic interpretations provided
the operator with several promising
undrilled locations, including the
Xijiang 24-1 structure. This location
became regarded as a development
project, but was still considered too
small to justify a newplatform.
Proving the validity of the new
maps required drilling additional
wells. In a newly discovered prospect,
these would normally be vertical
delineation wells, which are discarded
after logging. However,project
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number of sections drilled before a
failure occurs, so, while no increase
in reliability would be seen in terms
of traditional reliability KPIs such
as mean time between failures,the
reliability measured as meters between
failures will continue toimprove.
Meeting thetargets
Operators want strong production
from every well they drill, so justifying
a drilling campaign onprospects
other than certainties has become
increasingly difficult in recent years.
As a result, operators and service
providers must work together to
ensure that the targets are selected,
planned, and drilled correctly. To help
the operating companies reach their
business goals, service companies
must understand the financial
limitations and find a way to work
profitably withinthem.
The development of new
technology should be driven by the
operators’ needs and only introduced
where a business benefit can be
clearly demonstrated. This is where
the use of performance-driven KPIs
becomes invaluable. Although new
technology often has a reliability risk,
its use may be justified if it offers a
step change in performance. To help
operators weigh these issues, it is
essential that service companies be
involved early in the planning process.
This enables better technical solutions
to be proposed and planned to
address the needs of anyproject.
Risksand rewards
Drilling-services providers are
generally compensated on an hourly
basis for equipment and personnel.
However, many service providers
maintain that the key to sustained
improvement is for them to share
some of the potential project risks
and the value that they can deliver
through performance gains. Thiskind
of business model already exists in the
exploration and production industry
and could include incentives for shoe-
to-shoe drilling, reduced number of
failures, and variable pricingbased
on effective penetrationrates.
Over the past 20 years, the
exploration and production industry
has welcomed innovations in drilling
practices ranging from the
introduction of MWDtechnologies
and steerable motors, to computerized
rig-site displays and high-resolution
while-drilling logs. In the early 1990s,
various operators and service
companies applied while-drilling
measurements to new methods of
stuck-pipe avoidance and developing
drilling trainingprograms.
Today, the development rate
for new drilling methods and
technologies remains high. This
continued commitment to drilling
optimization reflects the factthat
well designs and drilling programs
have become more complex, and
present tough, new challenges and
offer greater potentialrewards.
The key challenges for the next
decade are already well defined. Drilling
multilateral wells requires extraordinary
accuracy and control. Deepwater and
high-pressure, high-temperature wells
offer additional challenges. Wells are
being drilled in tectonically active and
remote areas where the infrastructure
may be less well developed and the
communications problematic. The
emergence of new drillingtechnology
is driven by the needs of the industry
(Figure26).
Sharing risks and rewards would fit
into the cooperative systems being
advocated by operators. Manyoil
companies are now seeking a complete
package from drilling-services
providers. By this, they mean that their
drilling-services provider is an
important member of the team and
plays a full role in assessing projects
and tackling problems. If service
companies and their customers can
achieve this level of trust, then other
benefits willfollow.
Figure 26: Drilling technology has advanced rapidly over the past 30 years. The development and introduction of new tools has enabled engineers to reach
deeper and more complex targets in frontier areas and established oil provinces.
Cooperation—the keyto
long-termsuccess
In many fields, the drilling-services
providers are only called in once the
targets have been selected and the
drilling program has been sketched
out. This leaves very little scope for
the service provider to help reduce
costs or increase the efficiency of
the program. When drilling-services
providers are present from the early
stages of field development and
intimately involved in the planning
process from the conceptual target
selection, then their potential impact
is much greater and the cost savings
can be immense (Figure 25). Targets
can be selected to tie in with the
optimal drilling surface location or
slot, and targets may be linked to
increase the reservoir penetration
with a single wellbore. Well profiles
can be optimized by reservoir
engineers and petrophysicists to
ensure the optimal trajectory, and
the field can be planned toensure
that anticollision issues are addressed.
In addition, involving the drilling-
services’ drilling engineers at this
early stage enables early optimization
of the BHA. All these factors, when
added together, can significantly
reduce wellcosts.
Developing relationships
characterized by openness and trust
between operators and contractors is
fundamental to team building. Even
without financial incentives, close
cooperation encourages peopleto
be proactive and find new ways to
boostperformance.
Assessingperformance
For drilling performance to improve
as a field development or contract
progresses, performance must be
benchmarked effectively. The key
performance indicators (KPI) must
be genuine measures of drilling
performance, and must be agreed
upon by the operator and the
provider in advance. As drilling
advances and the number of wells
increases, the learning curve canbe
assessed and the impact of various
drilling services can beevaluated.
Typically, drilling-services companies
have been assessed on and compared
using tool reliability in terms of
circulating hours. While thisprovides
a simple way to compare suppliers,
it does not drive performance, and
leading companies are trying to use
KPIs that better reflect the impact
that a service provider can have on
drilling performance. For example,
Schlumberger is trying to move to
more representative KPIs such as
meters between failure andmeters
drilled per circulating hour, whichare
much more closely tied to an
operator’s own performance metrics
when a well isdrilled.
By crossplotting these suggested
metrics against each other, it becomes
apparent that after a certain base level
of reliability is achieved (meters
between failures), savings from
increased reliability become very small
compared with those achieved through
increased effective performance
(meters per circulating hour). As the
effective performance improves the
drilling efficiency, the well cost
continues to be significantly reduced.
Performance also directly affectsthe
Figure 25: Choosing an integrated service company to cover all aspects of drilling lowers costs, saves
time and reduces the administrative burden on operating companies.
42 43Middle East & Asia Reservoir Review Middle East & Asia Reservoir Review