Horizon 2020

DEVELOPMENT OF DRILLING
TECHNOLOGIES FOR SHALE
GAS
Prof. Eng. Rafał Wiśniowski
Ph.D. Eng. Adam Jan Zwierzyński
Ph.D. Eng. Aneta Sapińska-Śliwa
MSc Eng. Albert Złotkowski
The Faculty of Drilling, Oil and Gas
The Departament of Drilling and Geoengineering
Gdansk, 8 October 2014
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1. Introduction
One of aplication of petroleum drilling are unconvetional shale gas deposits.
Barnett Field

1. Introduction
The principal aim of works realized for optimization of shale gas drilling should be
working out a drilling technology thanks to which:
- the cost of performing a borehole can be maximally reduced
- maximal safety of drilling
- environmental protection provided.

1. Introduction
In presentation we would like to show the newest
trends in development of directional drilling

2. Review of newest technical solutions
Increasing demand for drilling services, especially for the
prospecting of unconventional deposits favors modification of
the existing techniques and technologies as well as development
of new drilling methods.
At present they are connected with both :

Rigs

Rigs – Development trends depending on the
drilling site
Presently, drilling operations are more and more
frequently performed in hardly accessible onland
places, far away from inhabited areas, e.g.
deserts, forests, highly elevated areas.
Demanded higher automation and mobility of
equipment. New solutions are needed.

drilling site
Many oil and gas deposits can be found under
the sea and ocean beds. Marine drillings have
been performed for years. Their particiaption in
oil and gas prospecting keeps increasing.
Solutions applied offshore are technologically
very advanced.

drilling site
Depletion of conventional deposits of oil and gas
necessitates prospecting of virgin, unexplored
areas. Drillings start to be commonly performed
in subpolar and polar areas.

drilling site
Search for critical elements, water and oxygen,
traces of primitive forms of life on space objects,
analysis of their geology and history necessitate
an increasing interest in the subject of drilling in
space conditions.
New solutions are needed. Part of them will be
applied to drilling in the Earth conditions.

Rigs
Among the newest solutions are both small, fully automated rigs and
huge offshore rigs.

Step 1: Rig in position 1
Rigs
Step 2: Rig is moved up using
hydraulic cylinders
Step 3: Rig is moved horizontally
using hydraulic cylinders
Step 4: Rig is moved down. Rig in
position 2

Rigs
On the other hand, we have automated, large mobile rigs used for
opencast mining purposes.

Rigs
In the case of marine drilling the rigs are mounted on fixed, self-elevating,
semisubmersible platforms or vessals.

Diesel motors Pneumatic motors Hydraulic motors Electrical motors
 Low cost of fuel
 High power
 Universal
applicability
 Environmentally-friendly
 Possible
overloads
 Simple design
 High durability
 Safety
 Reliability
 Higher powers as
compared to
pneumatic
motors
 Safety
 Easily controllable
 High powers
 Reliability
 Applicable in
difficult conditions
Rigs - Drives

Rigs – Drives
Dominating role of electrical and hydraulic drives
Diesel motors Pneumatic motors Hydraulic motors Electrical motors
 Low cost of fuel
 High power
 Universal
applicability
 Environmentally-friendly
 Possible
overloads
 Simple design
 High durability
 Safety
 Reliability
 Higher powers as
compared to
pneumatic
motors
 Safety
 Easily controllable
 High powers
 Reliability
 Applicable in
difficult conditions

Rigs
Hydraulic rigs
Advantages of hydraulic rigs
•Quickly assembled/disassembled
•Lower than conventional rig
•Considerably automated drilling
operations
•Lower hourly cost of rig operation
•Lower environmental degrading

Rigs
Hydraulic rigs – comparison with traditional rigs

Hydraulic Rigs
Hydraulic rigs for snubbing drilling Electrical rigs for snubbing drilling
• Hoist: 300T
• Snubbing: 130T
• Thanks to the set of wellheads, the sealing
and injection jobs can be performed
efficiently
• Low mass and small size make the rig more
mobile
• Hoist: 250T
• Snubbing: 65T
• Working rate: 1.5 m/s
• Electrical drive
• Anti-buckling system

Rigs
New rig designs for space applications, worked out at FDOG

Rigs
New rig designs for space applications, worked out at FDOG
Funded by the Government of
Poland through an ESA Contract
under the PECS (Plan for European
Cooperating States)
The view expressed herein can in no
way be taken to reflect the official
opinion of the European Space
Agency

Development of new solutions: Atestation Laboratory of
Drilling and Exploitation Devices
Perfomed tests:

String

String
New designs of drill string and casing mainly rely
on material technologies.
Apart from classic carbon steels and alloys the
casing and collars are made of new-generation
steels withstanding corrosion, high pressure and
temperatures.

„String”
Drill string can be also made of titanium or various aluminium alloys. Casing, used for
protecting borehole against crushing or contracting rocks used to be made only of
steel; now it is produced also of other materials.
Comparison of properties of mud pipes made of titanium (Ti- 6A1- 4V) and
standard casing (27/8-in. x 0.362 )
Average unit
mass
[lb/ft]
Young modulus
[psi]
Maximum
torsional
moment ,
[ft . lb]
Tensile
strength, [lb]
Minimum yield
Material point Re [psi]
S-135 Steel 135 000 385,820 20 798 30 000 000 10.50
G-105 Steel 105 000 300,082 16 176 30 000 000 10.50
Ti-6A1-4V 120 000 342,951 18 487 17 000 000 6.19

Bits

Roller bits
Recently an advancement in bit technology has been
observed. The patented solutions:
•Sealing and lubrication of bearings inside,
•Covering the bearing with plastic materials,
•Hard fastening of teeth on the edge girdle of the bit,
•Hard facing of sides,
•Optimization of shapes and distribution of teeth and cones on
girdles,
•Adjusting movement of particular cones with respect to one
another and their angle, depending on the hardness of drilled
rock,
•Use of directed hydraulic nozzles
created conditions in which cogged bits can transmit large
axial loads at high rotational speeds.

Bits with natural
diamond blades
Impregnated bits
PDC (Polycrystalline Diamond Compact)
bits
Hybrid bits
Considerable advancement in diamond
bit design has been recently observed.
The following drills and bits are
presentely applied:
Diamond bits

Drills - Development of new solutions:
Laboratory of Rock Drilling Mechanics
Perfomed tests:

Drilling fluids

Drilling fluids
Various types of fluids are used in drilling
technology, e.g.
•Drilling muds,
•Sealing slurries,
•Buffering fluids,
•Wash out fluids,
•Advancing fluids,
•Cushion fluids,
•Acidifying fluids,
•Fracturing and supporting fluids,
•Overpacker fluids.

Drilling fluids
New recipes of drilling muds and cement slurries used for drilling in
unconventional gas fields have been worked out at the Faculty of Drilling, Oil
and Gas.
Laboratory of Drilling Fluids
Physicochemistry Laboratory of Drilling Fluids
Laboratory of Geoengineering
and Cementing

Drilling fluids – Development of new solutions:
Laboratory of Drilling Fluids Physicochemistry
Perfomed investigations:

Laboratory of Drilling Fluids

Laboratory of Geoengineering and Cementing
1) Physical parameters of cement slurry:
2) Rheological parameters of cement slurry:

Laboratory of Geoengineering and Cementing
3) Cement – sheath measurements:

Casing

Casing
Casing is an important element of the borehole. Tripping
operation is both time-consuming and complex. Frequently
a few columns of different diameter are driven to the
borehole. New designs of a string which could play the role
of the casing are searched for. Among new technical
solutions are expanding casing pipes.

3. New drilling technologies
New technical possibilities favor the development of
drilling technologies.
The drilling of a borehole lies in making a cylindrical
opening in the Earth crust of specific diameter, depth and
planned trajectory.
For geologic–drilling reasons the borehole cannot be
performed in one technological process; it has to be
drilled section-by-section and the diameter gradually
reduced.
New technological solutions are aimed at shortening the
time of drilling of a borehole having a strictly defined
trajectory.

Considerable progress has been recently observed in the
directional (also multilateral) drilling technologies.
Drilling with the use of the top drive and downhole
motors: there were worked out new technologies which
can be employed for the prospecting of unconventional
deposits of hydrocarbons.
Coiled Tubing Drilling
Snubbing Drilling
Underbalance Drilling
Managed Pressure Drilling
Slimhole Hydraulic Drilling
Casing Drilling
Expanded Casing Drilling

Coiled Tubing

Snubbing drilling
Anti Bucking System

UBD - Underbalance Drilling

UBD - Underbalance Drilling
ADVANTAGES OF UNDERBALANCE DRILLING
• Increases drilling rate
• Provides longer life of the drill
• Eliminates damage to the near-wellbore zone
• Provides higher yield
• Lowers lost circulations of mud
• Provides longer life of the borehole
• Lower cost of the borehole (the borehole starts to bring
profit since the moment the reservoir rock has been drilled)

MPD – Managed Pressure Drilling
MPD Technology
International Association of Drilling Contractors (IADC) defined MPD technology as
an adaptative drilling process used to precisely control the pressure in annular
space in the entire wellbore profile. Its main task is to provide constant pressure on
the bottom of the wellbore within appropriate range and good control of dynamic
pressure.
General MPD problem

MPD Technology is mainly employed for
drilling zones where the reservoir pressure is
similar to the fracturing pressure in the
layers of the drilled profile.
It is also used for drilling zones where the
risk of lost circulations and simultaneous
kicks is probable.

Traditional drilling Underbalance drilling in MPD
technology

Specialist equipment used in MPD technology

Slimhole hydraulic drilling

Slimhole hydraulic drilling
Working out engineering and technologies of
performing small-diameter multilateral wells
to opening out shale oil and gas deposits in
Poland.
General demonstrator concept of the designed
engineering and technology

Casing drilling
Depending on the type of drilled rocks and designation of the borehole,
there were produced numerous drilling systems with casing drilling.
Drilling technologies with casing drilling which have been elaborated
and used all over the World differ in the following elements:
•Mode of drilling,
•Type of drive transmitted on the drill and casing,
•Type of drills, their build and use technology,
•Trajectory of wellbore axis.

Casing drilling

Drilling with expanding columns
• Drilling of deep boreholes in complex geologic conditions
necessitates using many casing columns.
• To minimize their number, a new technology of expanding
liner pipes was worked out.
• This new type of the casing can be used for performing and
casing long sections of the wellbore of constant or slightly
reduced diameter.
• This technology also allows for reducing the cost of making
the borehole as the drilling for the surface casing can be
done with a drill of slightly smaller diameter.

Drilling with expanding columns
Classic casing plan vs. expanding casing plan
Conventional Well Plan
36"
26"
20"
16"
13-3/8"
11-3/4"
9-5/8"
7"
5-1/2”
TD =25,000’
The Vision

Drilling with expanding liner
Schematic of expanding liner

4. Designing trajectories of boreholes
The planning of an appropriate trajectory of a wellbore can frequently bring about
a higher efficiency of hydrocarbon production from the deposit. This is especially
important while developing unconventional deposits of hydrocarbons.
The process of drilling vertical boreholes (conductor and technical columns) is
frequently associated with unintended displacement of the wellbore axis from
vertical. The supervision of the trajectory of the performed wellbore is very
important.

The rotational system for vertical drilling, initially designed for oil
wells, now also finds an application to:
•Freeze boreholes (while making freeze plates),
•Engineering boreholes near the shaft (to avoid underground mining
infrastructure),
•Geothermal boreholes.

The basic element of keeping a borehole vertical is a
stabilizer equipped with expandable conductor-ribs.
The actual displacement from the vertical is recorded by
sensors.
The correction is made by expanding conductor-ribs and
exerting side force on appropriate part of the wellbore wall,
pushing the stabilizer to the vertical position.

Vertical Rotary Steerable System (VRSS)
V-Pilot PowerV VertiTrak RVDS

Rotary Steerable System (RSS)
Geo-Pilot PowerDrive X5 Autotrak
Push the bit
Point the bit

Multilateral boreholes
Maxon motor
• 200°C
• 100 g
• 5'000 m
• 1 700bar

5. Optimization of horizontal drilling
While drilling wellbores in unconventional gas deposits located in
mudstone-clayey strata, the following elements should be accounted
for to reduce the cost of drilling and enhance the flow of formation
fluids:
1. Optimize the design of the wellbore in view of lower cost of drilling,
2. Optimize the number of drilled wellbores by performing multilateral
wells,
3. Optimize the trajectory of wellbores, i.e. drill perpendicular to the
strongest rocks,
4. Optimize the risk of drilling works by performing additional wellbores
and well logging.
5. Optimize the proppant used for supporting the fractures.

While introducing hardware to the wellbore attention should be paid
to the complete recovery of the resource in a long time perspective.
The additional enhancement works should:
• Maximize the completion of the field resources at minimum cost,
• Provide solid fractures, eliminating the risk of closures after the
pumping pressure of sealing slurry has been lowered,
• Provide many year’s operation of the wellbores.

Optimization of the wellbore structure means a casing plan which
minimizes the cost of the used steel.
The difficulties connected with drilling in unstable zones should
be minimized by using properly selected drilling mud which
provides high mechanical rates of drilling, protects the wellbore
wall and gives stability.
Lighter rigs can be used for lighter casing columns
Smaller wellbore diameters reduce the cost of the fluids used for
drilling operations.

Optimum design of a wellbore – most
advantageously on four casing columns

Unconventional deposits of gas are located at condsiderable
depths in Poland, therefore it is more advantageous (considering
the total number of drilled wellbores) to use vertical borehole
sections for multilateral offsprings.
In this type of completion one outlet can open a considerable
part of the rock hosting hydrocarbons.
In this way the cost of the performed wellbores can be reduced
as compared to single-lateral boreholes which are used for
opening out an analogous area.

Single vs. multilateral wellbores

Field completion with multi- and single-lateral wellbore

Unconventional mudstone-clayey reservoir rocks and classic
reservoir rocks have different directional anisotropy of strength
parameters of rock skeleton. Such rocks are layered, which
necessitates a specific way of drilling.
Structure of mudstone-clayey rock

Completion works in this type of rocks should concentrate on
drilling in a perpendicular direction when strongest rocks are
involved. Maintaining appropriate trajectory is decisive at the
successive stages of work in the borehole as far as fracturing of
hydraulic rocks is concerned.
Proper direction of wellbore axis with
respect to rock mass lamination

By taking into account the directional anisotropy of mechanical
strength of rocks, the rock layers can be 'disrupted' and the
fractures propagate at considerable distances from the wellbore.
In this way a very large area of the reservoir can be opened up
with one offshot of the multi-lateral wellbore.
Influence of directional anisotropy of clayey
mudstone on the range of fractures

Example of a large range of fractures obtained while drilling
perpendicular (left), and a small range when drilling horizontally

The trajectory of a wellbore can be properly realized only after
well logging, thanks to which the direction of layers can be
identified. For this reason, additional wellbores have to be drilled
for geophones.
Borehole trajectories can be well designed and then gas
production enhanced with the hydraulic frac method only when
the unconventional rock has been correctly recognized.
The auxiliary wellbore should be later used for other completion
works.

Properly recognized build of the rock mass in the completion zone

The fracturing job is a complex and multistage operation. The
main role in the foractures formation plays the frac fluid, which is
responsible for opening the rock
Opening takes place after a certain value of pressure is exerted
by frac fluid on the rock; as a consequence the continuity of the
medium is disturbed. The mudstone-clayey rock delaminates
necessitating large volumes of fluids to be injected.
This is a rather violent process, requiring large amounts of water
at hand (from a few to tens of thousands m3 of water.)

Fracturing job: pressurize frac fluid parallel to lamination and
obtain fractures between them

Then appropriate proppant is sequentially injected to support the
opened fractures.
Besides, proppant also 'polishes' the main channels in the rock
increasing their diameter.
Complete frac job is connected with a flowback of 20 to 40% of
injected fluid and gas flow from the reservoir.
Inappropriately selected proppant will not protect the fracture; it
will hinder gas flow to the borehole.

Introduction of proppant and flowback of
fracturing fluid; unsupported fractures contract

•Proper granulation,
•Good geometrical proportions of grains,
•Applied sharpness of edges,
•Sufficient strength of grains,
•Material used.
Selection of size, shape
and sharpness of proppant
edges
Selection of optimum proppant should be based on:

Meeting all requirements set before good wellbores producing
unconventional gas is troublesome.
Experience in designing parameters of boreholes, drilling fluids
and interpretation of well log data helps find the best solution
without unnecessarily risking too much.
Nonetheless, the complexity of this issue makes the specialists
further develop techniques of drilling and completing deposits of
hydrocarbons in mudstone-clayey strata in Poland.

6. Concluding remarks
According to our experiences, optimisation of shale gas drilling can be realized by:

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