directional drilling

Middle East & Asia Reservoir Review26 Middle East & Asia Reservoir Review The development of rotary drilling methods at the start of the twentieth century provided the technical basis fo

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New Frontiers in Directional Drilling

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 art as

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 traditional drilling.

In this article, Sudhendu Kashikar reviews the latest drilling methods and technologies, and examines how they will shape future operations.

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Middle East & Asia Reservoir Review

26 Middle East & Asia Reservoir Review

The development of rotary drilling

methods at the start of the twentieth

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 highly variable

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

safety improvements

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 in the

reservoir, with reduced nonproductive

time This level of performance is

achieved more quickly, at a lower cost,

and without compromising the safety

of the well

The number of directional wells is

growing every year, and many of these

are being drilled in more challenging

oilfield environments such as deep

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 operators are

performing infill-drilling campaigns to extend asset life and maximize value from existing infrastructure

Vision, understanding, and communication

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 each well

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, the new 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) where data are gathered and processed for experts

to review; and connectivity between office-based experts and their colleagues at the wellsite (Figure 1)

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 during drilling

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 for Onshore

Oil Operations, Petroleum Development Oman, Abu Dhabi Marine Operating Company, and Occidental Petroleum Corporation

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 review capabilities

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 to come

An established technology

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 injector wells

By the mid-1980s, drilling techniques had advanced significantly,

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, steerable motors, polycrystalline diamond compact bits,

or computers Without these key tools and technologies, there were many problems for the directional driller

to overcome

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 widely adopted

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 Oman drilled

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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 companies to 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 industry tool

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 increase reserves

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 (Figure 3)

Rotary steerable systems—a new direction

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 conventional systems

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-quality wellbores

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 had anticipated

Figure 1: The real-time cycle promotes continuous review and refinement of drilling operations

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 field reservoir

Figure 3: Horizontal wells offer a range of production benefits

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Accurate and powerful

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 unit contains

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 well trajectory

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 (Figure 5)

Once a pad has passed the push

point, the rotary valve cuts off its mud

supply and the mud escapes through

a specially designed leakage port

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 other out

Improved drilling methods produce better wells

Fully rotating steerable systems have been tested and shown to minimize problems such as wellbore spiraling and ballooning RSS systems optimize the efficiency of cuttings transport

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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

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 packing off

there are no stationary components

to create friction The efficient removal of cuttings means that cuttings are not reground during drilling

past the BHA because there are no annular bottlenecks in the wellbore

Enhanced production 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 (Figure 6)

Improved reservoir access and drainage

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 drainage patterns

Minimized lost-in-hole time 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 incidents for RSSs with those for conventional BHAs showed the RSS lost-in-hole rate was only 15 % of that experienced with conventional systems

Improved safety 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 to drill 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, increases safety

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 environmental impact 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 and lower drilling fluid losses For example, if the

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 (Figure 7)

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 (Figure 8)

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 annular velocity

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The tools for the job

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

each customer

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 drilling applications

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

of the drain section was drilled within

the optimum sand zone, and, during

this operation, the system achieved

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 conventional technology

Reliability and wear resistance are key features in demanding environments The PowerDrive Xceed tool has a totally enclosed internal steering mechanism and rugged, field-proven electronics that safeguard the tool’s performance in abrasive, hot, and high-shock applications

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 directional drilling

The next step

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 and cost-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 production potential

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 wasting time coring an uninteresting formation are significantly reduced

High-performance drilling with a motor

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 and unpredictable

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 optimization require excellent depth control and smoother holes that pass into the productive pays of any target zone and remain within it

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 be substantial

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 150 degC

High-quality drilling is achieved using

a simple, rugged steering section and directional measurements near the bit for precise, true-vertical-depth directional control

torque, minimize dogleg severity, drill

a smoother hole, and increase bit life (Figures 10 and 11)

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 requirements change

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 hole cleaning

Formation evaluation while drilling

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 Xceed system

Figure 8: The key features of the PowerDrive system Precise deviation control, continuous rotation,

and improved hole cleaning all lead to lower production costs

Figure 10: The principle of the mud motor

delay between drilling and logging meant that the results from wireline logs had to be corrected for invasion and other postdrilling effects

The Schlumberger LWD tool was introduced in 1988 The basic measurements were resistivity, neutron and density porosities, and photoelectric factor By the early 1990s, improvements had been made

in areas such as tool reliability and data-transfer rates

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

This development process has continued with the arrival of two new measurement systems, 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 are developed

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Reduce depth uncertainty with

real-time borehole seismic

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 seismic data

Continuously updating the bit’s

position on the seismic map helps

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 mud weight

Real-time producibility information

while drilling

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, and provides

reliable determinations of

mineralogy-independent porosity, bound- and

free-fluid volumes, productive zones,

and pore size, as well as the

identification of fluids (Figure 12)

techniques will help operators to reduce risk and overcome some of the geological uncertainties encountered while drilling complex wells

Ultrahigh telemetry rates (up to

12 bps) have been used to optimize 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 are high

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 drilling engineer can make rapid adjustments to the wellbore trajectory, relative to geological bedding planes or faults, and can modify steering while drilling

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 helps to monitor wellbore stability and enables adjustments to be made to mud weights or effective circulating density as required (Figure 14)

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 while drilling

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 acquired on

a subsequent wiper trip provides a clear picture of hole enlargement and stress failures after drilling

The big picture from the borehole

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 by bit

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 detailed images

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 and geosteering

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-fluid volumes

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

What could possibly go wrong?

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 drilling problems

(Figure 15) Avoiding drilling problems

cuts finding and development costs

and enables oil companies to focus on

their core business—building and

replacing reserves

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 on schedule

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 abandon the

stuck portion and drill a sidetrack around it This changes the drilling program completely and may significantly increase the well’s cost

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 stuck pipe

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 or blowouts

a Cement

c Differential sticking

d Drillstring vibration

e Fractured zone

formation

l Reactive formation

m Unconsolidated zone

n Undergauge hole

Figure 15: Offshore drilling costs are high, and problems that take days to solve will have major implications for field-development budgets

Drillstring vibrations can weaken and destroy pipe and equipment as well as seriously damage the wellbore

And some problems, even if they

do not completely suspend the drilling process, jeopardize subsequent logging, completion, and production

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 sound plan,

to update this continuously as new information becomes available, and

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 be encountered

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 for interpretation

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Right first time

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 the drilling

operation There are three phases in

an NDS project, see Figure 18

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, or safety

Technologies to meet key challenges

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 and services

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 reservoir data

This integration has led to benefits in areas such as stimulation, completions, and production optimization

Balancing costs and benefits

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 the technical

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 the reservoir

Azimuthal density/neutron viewer

software also enables structural dip

picking from images This can be

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

complex fields

LWD VISION tool eliminates the

need for a pilot hole

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 the reservoir

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 better wells

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 reviewing performance

The first challenge for a new drilling program is to link all the relevant

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 (Figure 17)

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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understanding of the reservoir and its production, it can optimize well placement and select the best perforation zones or drilling trajectories

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 those that 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 success will

be finding economically viable methods

to tap those reserves, despite the increased technical complexity that will be necessary

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 are starting

to affect field performance and production-enhancement services 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 the past

Reaching further, drilling smarter

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 other approach

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 meet demand

achievements of recent years, as

the industry drills deeper and more

complex wells

Well construction costs may be

rising, but the aim of reservoir

development technology is to

optimize reservoir exploitation using

a few advanced wells that significantly

outperform their conventional

counterparts Nowhere has this been illustrated more clearly than

in Russia, where a field development plan for 57 vertically drilled wells was recently scrapped in favor of two geosteered horizontal wells The total field production from the original plan

with a 19-year life Production from

the two designer wells totals

in 7.6 years

Brownfield drilling

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 (Figure 20)

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 the future

Once the company operating

a brownfield asset has a clear

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 way ahead

The demands of modern oil and gas exploration will continue to 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 specific needs

Collaborating with customers

There are many examples of collaborative projects for developing new technologies and processes with customers For example, Schlumberger Drilling and Measurements is currently working 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 mature fields

In the drilling sector, the key to business success is the ability to drill wells efficiently and safely while

providing maximum environmental protection Operating companies and regulatory authorities set 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-term partnership

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 cost savings

Leading operators have found that they can benefit from synergy when modern workflow processes are applied by highly trained and experienced members of the drilling team operating within a customized business model

People make the difference

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 technically demanding

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 efficiency improvement

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 service vendor

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’s challenges

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 service companies

to find opportunities for collaborating with their customers, particularly when they will be rewarded for the value they bring through improved drilling performance

Extended reach in the South China Sea

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 subsea wells

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 new platform

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

economics dictated that every new well should produce oil to cover or offset drilling costs

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 drilling campaign

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 more quickly

Dramatic rise in drilling efficiency for Middle East operator

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 PowerDrive system

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 be overcome

The PowerDrive Xceed system met the challenge and exceeded expectations on cost and time savings

Reduced wellbore tortuosity cut trip time by 68 %—a direct result of improved hole quality The operators

used the PowerDrive Xceed system

to drill the longest well in the field and, for the first time, managed to drill the sandstone section (4,172 m) in one run

Reliable tools and clearer pictures

Drilling places tough demands on tools For Schlumberger, tool reliability has been a priority for many years

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 few days

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 made downhole

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 to work

on the same model This enables the team to identify zones of interest, select targets, and work on the well path in an integrated process

Real-time visualization and the use

of secure Internet links, such as the InterACT system, also enable companies to identify potential 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 and money

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

within a multidisciplinary framework

Figure 23: Extended-reach drilling opens up

smaller satellite fields at a fraction of the cost

of traditional field development methods

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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 to improve

Meeting the targets

Operators want strong production from every well they drill, so justifying

a drilling campaign on prospects 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 within them

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 any project

Risks and 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 This kind

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 pricing based

on effective penetration rates

Over the past 20 years, the exploration and production industry has welcomed innovations in drilling practices ranging from the

introduction of MWD technologies 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 training programs

Today, the development rate for new drilling methods and technologies remains high This continued commitment to drilling optimization reflects the fact that well designs and drilling programs have become more complex, and present tough, new challenges and offer greater potential rewards

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 drilling technology

is driven by the needs of the industry (Figure 26)

Sharing risks and rewards would fit into the cooperative systems being advocated by operators Many oil 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 will follow

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 key to

long-term success

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 to ensure

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 well costs

Developing relationships

characterized by openness and trust

between operators and contractors is

fundamental to team building Even

without financial incentives, close

cooperation encourages people to

be proactive and find new ways to

boost performance

Assessing performance

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 can be

assessed and the impact of various drilling services can be evaluated

Typically, drilling-services companies have been assessed on and compared using tool reliability in terms of circulating hours While this provides

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 and meters drilled per circulating hour, which are

much more closely tied to an operator’s own performance metrics when a well is drilled

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 affects the

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

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