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1.1 Development of downhole drilling motors

Since the first turbodrill patent was awarded in 1873,

designs and ideas for downhole motors have prolif-

erated. Today, positive displacement motors dominate

oilfield operations and offer distinct operational and

economic advantages over conventional rotary drilling

in many conditions.Downhole motors offer the option of drilling in either

a traditional rotary mode or a sliding mode in which the

hole follows the direction of the bent housing on the

motor. In directional drilling applications, downhole

motors permit control of the wellbore direction and,

thus, more effective deviation control than conventional

rotary methods.The Anadrill PowerPak* steerable motors (Fig. 1-1)

have been designed specifically to meet the demanding

criteria of directional drilling. This handbook is intended

to give general advice and guidelines and sufficient tech-

nical information to enable you to use PowerPak motors

to their fullest advantage.

Introduction 1.1

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Figure 1-1. PowerPak motor assembly.

Introduction1.1

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Bearing section andrig floorreplaceablesleeve-type stabilizer

SABSurface-AdjustableBent housing

Power section

Dump valve

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1.2 PowerPak design and testing

PowerPak motors were designed according to directional

drillers requirements, with particular emphasis on

ruggedness, simplicity and proven technology that trans-

lates to superior, dependable performance at the wellsite.

Customer and operational requirements were established

through liaison with drilling operators. Anadrill engi-neers then applied knowledge and expertise gained from

more than three decades of involvement in directional

drilling to set design criteria with a focus on reliability.

Anadrill followed a downhole systems approach to

minimize noise interference with measurements-while-

drilling (MWD) telemetry and to ensure that PowerPak

motors would not unnecessarily limit flow rates andother drilling procedures. An 18-month program of sys-

tems analysis and component testing began in 1990.

This comprehensive program included full-scale dyna-

mometer and drilling rig performance testing at the

Anadrill advanced testing facility in Sugar Land, Texas.

An engineered maintenance program was designed toinclude scheduling and component tracking.

Since their introduction in early 1992, PowerPak

motors have continually achieved or exceeded design

goals for reliability, performance and maintenance costs

and have established new standards for improved effi-

ciency and reduced drilling costs.

PowerPak features

PowerPak steerable motors are modular in design

(Fig. 1-2), which enables them to operate in a wide

range of directional drilling conditions with minimal

interference to MWD systems. Motor components can

be selected to optimize performance for each set of

drilling conditions.

PowerPak motors feature mud-lubricated bearings for

rough drilling environments.

Introduction 1.2

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Figure 1-2. Motor assembly cross section.

Introduction1.2

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Drive shaft

Transmission

assembly

SABSurface-AdjustableBent housing

Power section

Dump valve

Bearing section

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The variety of rotor/stator configurations allowsPowerPak motors to be used for both low-speed/high-

torque and high-speed/low-torque applications.

Extended power sections are available in most sizes

and configurations.

The SAB* Surface-Adjustable Bent housing improves

efficiency and increases drilling control at the wellsite.

A forged-steel drive shaft enhances the motors

strength.

Sealed transmission couplings extend motor life

by preventing mud contamination.

The bearing section is compact, which places the bend

closer to the bit and further enhances directional

performance.

The bearing section incorporates tungsten-carbide-

coated radial bearings and multiple ball races as axial

bearings.

To optimize rotary drilling performance and minimize

bit wear, PowerPak bearing sections can be fitted with

rig floorreplaceable, sleeve-type stabilizers or withintegral blade stabilizers.

Introduction 1.2

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1.3 Applications

The versatility of the PowerPak motors makes them the

ideal motors for both performance (straight hole) and

directional drilling. They are also useful in coring,

under-reaming, milling, template drilling and other

operations that are not covered in this handbook. For

information on these applications, call your Anadrillservice representative.

Performance drilling

In straight-hole applications, PowerPak motors function

as a performance drilling tool to increase the rate of pen-

etration (ROP) and reduce casing wear by minimizing

string rotation.

Directional drilling

Compact design and high-torque capabilities make

PowerPak motors ideal for both conventional directional

drillingthat is, situations in which a well path is

steered to follow a planned geometric courseand

geosteering, in which the well or drainhole is steered tooptimize its local position within a reservoir with regard

to geological, fluid and structural boundaries.

For conventional directional drilling, an adjustable

bent housing in the transmission section and a stabilizer

on the bearing section allow the PowerPak motor to drill

in either an oriented (sliding) or a rotary mode. In rotary

mode, both the bit and the drillstring rotate. The rotation

of the drillstring negates the effect of the bent housing,

and the bit drills a straight path parallel to the axis of the

drillstring above the bent housing.

In sliding mode, only the bit rotates. The motor

changes the well course in the direction of the bent

housing, and the drillstring slides down the hole after thebit. In this mode, the motor is oriented in the same way

as for conventional directional drilling, making it appli-

cable for kickoff or course corrections.

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The PowerPak steerable motor makes it possibleto drill complete hole sections with one bottomhole

assembly (BHA) and to attain various combinations

of hole size and buildup rate.

In each of the applications described above, the

PowerPak adjustable bent housing can be quickly set

on the rig floor. Housings are available for 0 to 2 and

0 to 3 bend angle ranges. The PowerPak extra curve(XC) motor has a surface-adjustable 0 to 4 bend

mechanism.

The PowerPak steerable motor consists of three major

subassemblies:

power section, composed of a rotor and a stator, which

converts hydraulic energy into mechanical rotarypower

transmission section, which transmits rotary drive

from the power section to the bearing section and also

incorporates the adjustable bent housing

bearing section, which supports axial and radial loads

during drilling and transmits the rotary drive to the bitthrough a drive shaft.

Introduction 1.3

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