RAG.ENERGY.DRILLING

Heimo Heinzle RAG.ENERGY.DRILLING, Schwarzmoos 28, A-4851 Gampern, www.rag-energy-drilling.at

Drilling, a high precision technology - current challenges and possible ways forward

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Introduction • Directional / Extended Reach Drilling

• Underbalanced Drilling

• Casing Drilling

• Coiled Tubing Drilling

• Dual Gradient, Managed Pressure Drilling

• Laser Drilling

• Plasma Drilling

• Automated Drilling / Rigs

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Summarizing the Challages

• Well should be: • Deeper • Longer • Drilled faster • Drilled cheaper • Drilled at remote Locations • …

Driven by the Oil Prize

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Safety !

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Directional Drilling – WHY ?

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Extended Reach Drilling – WHY ?

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Wytch Farm Field

• Discovered 1973

• Production before ERD

~10k-20k bbl/day

• Since 1993 ERD

• Production peak in 1997

with 110,000 bbl/day

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Sakhalin (RUS) Extended Reach 12.700m

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ERD Challanges

• Surveying

• Directional Drilling

• Geosteering

• Hole Cleaning

• Torque & Drag

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ERD - Margin of Error

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Directional Terminology

azimuth

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Approximation By Radius Of Curvature Method

P1

P2

ERD - Margin of Error

Accuracy of Compass

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Mud Pulse Telemetry

• Mud pulse telemetry utilizes an incompressible transmission path (mud column in drillpipe) to carry pressure waves created by a downhole pulser

• Sensor data can be encoded in many different ways but all methods require the pressure pulses to be detected at the surface in order for the data to be decoded

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Mud Pulse Telemetry – Positive Pulse

MEASURED TIME

MINIMUM PULSE TIME DATA TIME

• Data values (4 to 6 bits) are encoded as the time interval between two pulses

Choke Piston Turbine

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Electromagnetic Telemetry

• EM emitting antenna injects an electric current into the formation around the hole

• An electromagnetic wave is created, which propagates in the formation while being “channeled” along the drillstring

• Data is transmitted by current modulation and decoded at the surface

• Propagation of EM waves along the drillstring is strongly enhanced by the guiding effect of the electrically conductive drillstring

• If deeper than ~1,700m to 2,000m – repeaters installed within drillstring

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Directional Control

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PDM Motors

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• Push the Bit

• Point the Bit

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Rotary Steerable Systems

Push Point

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Rotary Steerable System

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• For straight hole sections, the RSS operates in a neutral position with the drive shaft concentric with stabilizer sleeve.

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Rotary Steerable System

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• For direction changes, hydraulic pistons deflect the drive shaft from the centerline, forcing the bit-to-point in the opposite direction.

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Rotary Steerable System

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Neutral Position

Maximum Deflection

Intermediate Deflection

• Eccentric rings

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Geosteering

21

Production Well

Offset Well

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Geosteering

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� Gamma Ray

� Formation Resistivity

� Formation Density

� Ect.

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Cuttings Bed Behavior

�Slip-velocity (suspension)

�Avalanching �Stationary cuttings bed �Cuttings transport depends on GPM/RPM

>

Legend: With flow No flow

> ±65° ±30° to ±65°

< ±30°

Hole Cleaning

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Gravity

Hole Cleaning

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Hole Cleaning

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Rotation Effects Why is it easier to clean 8-1/2” (& smaller holes)?

5” DP in 8-1/2” Hole 61% Eccentric

5” DP in 12-1/4” Hole 81% Eccentric

Pipe is better centralized by tool joint in small hole

Viscous coupling more effective

Higher annular velocity (usually), more evenly distributed

Fewer cuttings to remove for same ROP

Tool Joint

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Torque & Drag

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• Friction Factor is a coefficient that depends on wellbore roughness, tortuosity, drilling fluid lubricity, string stabilization, etc...

WOB has to be compensated for inclination and drag

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Torque & Drag - Buckling

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• Sinusoidal Buckling • Helical Buckling

INTERVALS OF AN E.R. WELL WHERE BUCKLING IS MOST LIKELY TO OCCUR

Near heel, on longhorizontal sections

In the lower tangent section, above the build/turn.

Buckling will probably not occur in the build or turn itself

as 'bent' pipe is more resistant to buckling.

Buckling is significantly more likely to occur with small

OD drillpipe above a liner top.

Intervals where bucklingis most likely to occur

In the vertical section, if in compression.

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Underbalanced Drilling • Bottomhole circulating pressure is less than the static reservoir

UBD Conventional pressure

• Reservoir fluids enter the wellbore as drilling proceeds

• Preventing loss of drilling fluids to the formation

• Eliminating many causes of formation damage

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Underbalanced Drilling

• Five forms of flow regimes in UB

drilling exist. Actually all of these

grade into each other at some

point due to compression of gas.

• The flow patterns and lifting

capacity will change with gas

percent and fluid properties.

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Underbalanced Drilling

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Foam / Aerated Fluid Drilling

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Advantages of UBD • Reduced Formation Damage (Skin effect) - Especially for low-pressure reservoirs

• Reduced Completion and Stimulation Costs

• Expensive horizontal well stimulations can be eliminated

• Decrease of drilling costs (for material and time) by avoiding lost circulation, especially across fractured, low-pressured or highly permeable zones

• Elimination of Differential Sticking - Especially across low-pressured zones

• High Penetration Rates Reversed chip hold down effect increases ROP, especially in horizontal wells with low WOB

• Real Time Reservoir Investigation Proper data monitoring and interpretation allows identification of geological anomalies like fractures, hydrocarbons or water zones Production rates during drilling permits real-time decision regarding change in drilling depth, wellbore orientation and overall length.

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Disadvantages of UBD

• UBD has its own unique damage mechanisms, such as surface damage of the formation due the lack of heat conduction capacity of underbalanced drilling fluids.

• It is more complicated to model and predict the behavior of compressible drilling fluids.

• Reduced wellbore pressure gradients can cause hole stability problems.

• Stable foam condition is not easy to achieve.

• Water Influx – effect on cuttings transport

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• There is a higher risk of blowout, fire or explosion.

• Underbalanced drilling is still an expensive technology. Depending on the drilling fluid used, the cost can be significant, particularly for extended reach wells.

• It is not always possible to maintain a continuously underbalanced condition. Since there is not a filter cake around the wellbore, any instantaneous pulse of overbalance might cause severe damage to the unprotected formation.

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Casing Drilling

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Casing Drilling - 2 systems

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Casing Drilling

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Torque ring

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Casing Drilling – possible applications

• Shallow well sections

• Depleted zones / Mature fields / Differential Sticking

• Wellbore Stability Problems / Reaming Runs

• Lost Circulation during drilling

• Hole cleaning issues / large diameters

• High NPT (non productive time) (BHA / DP change)

• Cost effective (vs. rig rate)

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Casing Drilling - Disadvantages

• Drilling shoe to shoe (if BHA not retrievable)

• Time for R/U and R/D

• Back-up plan if problems (stuck casing, …)

• Torque Limitations – special connections (backreaming, …)

• Additional personnel at rig site

• Bit not re-useable

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Coiled Tubing Drilling

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Coil Tubing Drilling – possible applications: • Deepening Wells

• Conventional re-entry

• Through Tubing Re-Entry

• New wells from surface

• Rigless platforms

• Underbalanced Drilling

• Open Hole Sidetracks

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Coil Tubing Drilling - Advantages • Safety

• Less Personnel • Reduced Pipe and Tool Handling

• Operational • Underbalanced Drilling Capability (with higher ROP) • Thru-Tubing Drilling Capability • Reduced Trip Times (Very few Connections to Make up) • “Wired CT Telemetry” gives fast data rates for LWD & has protected cable

• Environmental • Smaller Footprint • Reduced Noise and Emissions

• Economic • Lower Mobilization Cost (Less Equipment and Personnel) • Slimhole Technology

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Coil Tubing Drilling – Disadvantages / Limitations • Operational

• Hole Size (Mostly Slimhole Drilling – max. up to 8 ½”)

• Rotation (Inability to Rotate CT String)

• Hole cleaning

• CT String Limitations (Lifetime of string / Mechanical & Hydraulic Limitations)

• Economic

• CT String = Consumable

• Downhole Motor Cost

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Dual Gradient, Managed Pressure Drilling

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DEPTH

Dual Gradient Drilling

¾ Single Gradient Wells

9 Wellbore contains a single density fluid

9 Single pressure gradient

¾ Dual Gradient Well

9 Wellbore feels seawater gradient to the seafloor, and mud gradient to bottom

DGD vs. Conventional Riser Drilling

SEAFLOOR

PORE PRESSURE

MUD HYDROSTATIC

PRESSURE DGD

SEA WATER HYDROSTATIC

PRESSURE

PRESSURE

MUD HYDROSTATIC

PRESSURE Conventional

FRACTURE PRESSURE

DGD vs. Conventional Riser Drilling

SEAFLOOR

PORE PRESSURE

MUD HYDROSTATIC

PRESSURE DGD

SEA WATER HYDROSTATIC

PRESSURE

PRESSURE

MUD HYDROSTATIC

PRESSURE Conventional

FRACTURE PRESSURE

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Dual Gradient Drilling

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Dual Gradient Drilling

Conventional Deepwater Casing Design:

Can result in 7+ casing strings !

Where to place/land them within wellhead ?

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Dual Gradient Drilling

12.4 ppg mud

13.5 ppg mud

12.4 ppg mud

13.5 ppg mud

12.4 ppg mud

13.5 ppg mud

Pressure, psi

Depth

ft

Seafloor @ 10,000’Seawater HSPSeawater HSP

23,880 psi

@ 37,500’

2 different fluid gradients

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Dual Gradient Drilling

Casing Requirement Conventional

SEAFLOOR

PORE PRESSURE

SEA WATER HYDROSTATIC

PRESSURE

PRESSURE

MUD HYDROSTATIC

PRESSURE Conventional

FRACTURE PRESSURE

Casing Requirement Conventional

SEAFLOOR

PORE PRESSURE

SEA WATER HYDROSTATIC

PRESSURE

PRESSURE

MUD HYDROSTATIC

PRESSURE Conventional

FRACTURE PRESSURE

Casing Requirement DGD

DEPTH

SEAFLOOR

FRACTURE PRESSURE

PORE PRESSURE

SEA WATER HYDROSTATIC

PRESSURE

PRESSURE

DEPTH

MUD HYDROSTATIC

PRESSURE DGD

Casing Requirement DGD

DEPTH

SEAFLOOR

FRACTURE PRESSURE

PORE PRESSURE

SEA WATER HYDROSTATIC

PRESSURE

PRESSURE

DEPTH

MUD HYDROSTATIC

PRESSURE DGD

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Dual Gradient Drilling

Wellhead and BOP

Return Line

Drillpipe

Rotating Diverter

BHADrill String Valve

Mud Return and Pump

Seawater-Driven MudLift Pump

Seawater Filled Marine RiserSeawater Power Line,

Control Umbilicals

Seawater Pumps(Existing Mud Pumps)

Wellhead and BOP

Return Line

Drillpipe

Rotating Diverter

BHADrill String Valve

Mud Return and Pump

Seawater-Driven MudLift Pump

Seawater Filled Marine RiserSeawater Power Line,

Control Umbilicals

Seawater Pumps(Existing Mud Pumps)

Seawater Power Line,Control Umbilicals

Seawater Pumps(Existing Mud Pumps)

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Dual Gradient Drilling Alternative Dual Gradient Systems: • Nitrogen Injection at Wellhead or below

• Injection of Hollow Glass Spheres at seabed

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Managed Pressure Drilling

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Managed Pressure Drilling The idea is to keep the static and dynamic pressure the same. How to go from static balance to dynamic (circulating) balance without either losing returns or taking a kick. This can be done by gradually reducing pump speed while simultaneously closing a surface choke to increase surface annular pressure until the rig pumps are completely stopped and surface pressure on the annulus is such that the formation “sees” the exact same pressure it saw from ECD while circulating.

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Way Forward

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Laser Drilling • A laser is a device that emits light through a process of optical amplification based

on the stimulated emission of electromagnetic radiation. The term "laser" originated as an acronym for "light amplification by stimulated emission of radiation".

• It is generated by a device which converts energy to electromagnetic beams or photons.

• This light radiation is then focused to form intense high powered beams which can fragment, melt or vaporize rock.

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Laser Drilling + Small Rig Site

+ No conventional Drilling Equipment needed (bit, DC, …)

+ Rate of Penetration (10x faster compared to conventional drilling)

+ Sealing wellbore due to melting prozess

- Energy consumption (wellbore diameter 8 1/2“ or bigger) ?

- Energy supply to rig site ?

- Bigger hole diameters – means overlapping laser beams

- Well Control Mechanism ?

- Formation Damage in Reservior Section due to melting process ?

- Wellbore Cleaning ?

- Wellbore stability ?

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High-energetic electrical plasma is a technology currently being developed in deep drilling applications

• An electric arc is an electrical breakdown of a gas that produces an ongoing plasma discharge, resulting from a current flowing through normally nonconductive media such as air or gas. An arc discharge is characterized by a lower voltage than a glow discharge, and relies on thermionic emission of electrons from the electrodes supporting the arc.

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Plasma Drilling

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Automated Rigs

• Automation • Conventional or • Robotics

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Automated Rigs

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+ Less personnel

+ Hands OFF - Safety

+ Eliminates human errors

+ Reliable ?

+ Reduced NPT

� What if equipment breaks down ?

� Maintenance Intervalls/Cost

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Dual Gradient Drilling Hollow Glass Spheres