Description

Positive Displacement Downhole Mud Motors for Directional Drilling

Goldenman Downhole Mud Motors are positive displacement drilling motors designed to convert drilling-fluid hydraulic energy into mechanical torque and rotary speed at the drill bit.

The available K7LZ series covers outside diameters from 95 to 244 mm, equivalent to approximately 3-3/4 to 9-5/8 inches. The product range supports vertical drilling, directional drilling, horizontal drilling, sidetracking, deviation correction, coring and reaming operations.

Standard and extended power-section configurations are available. An optional adjustable bent housing allows the bend angle to be set from 0° to 3° at the rig floor according to the directional drilling program.

Each motor is selected according to hole size, bit type, available drilling-fluid flow, pump pressure, required torque, desired bit speed, formation characteristics, bottom-hole temperature and drilling-fluid chemistry.

Product Short Description

Goldenman Positive Displacement Motors provide high downhole torque using drilling-fluid flow through a rotor-and-stator power section.

Available configurations include straight-housing motors, adjustable bent-housing motors, extended power sections and project-specific bearing assemblies. The motor can be matched to roller-cone or fixed-cutter bits according to the required torque, speed, flow rate and weight-on-bit range.

Product Highlights

• Positive displacement downhole drilling motor
• K7LZ series from 95 to 244 mm OD
• Tool sizes from 3-3/4 to 9-5/8 in
• High-torque, low-speed multi-lobe configurations
• Adjustable bent housing from 0° to 3°
• Straight-housing configuration available
• Standard or extended power section
• Replaceable rotor and stator assemblies
• Anti-friction transmission-section options
• Bypass or dump-valve assembly
• High-capacity radial and thrust bearing section
• Compatible with roller-cone and fixed-cutter bits
• Configurations for vertical, directional and horizontal drilling
• Project-specific drilling-fluid elastomer selection
• REG rotary shouldered connection options
• Performance, dimensional and inspection documentation available
• Replacement power sections and overhaul parts available

What Is a Downhole Mud Motor?

A Downhole Mud Motor is a drilling-fluid-powered positive displacement motor installed directly above the drill bit or lower BHA components.

Drilling fluid flows through the motor’s power section. The interaction between the helical rotor and elastomer-lined stator creates sealed cavities that move through the power section.

This hydraulic action rotates the rotor and produces:

• Rotary speed
• Output torque
• Hydraulic pressure drop
• Mechanical power at the bit

The transmission section converts the rotor’s eccentric movement into concentric rotation and transfers torque to the bearing assembly and bit box.

Because the bit can rotate without rotating the complete drillstring continuously, a Mud Motor can support directional control, slide drilling and reduced drillstring rotation in selected operations.

Main Applications

Goldenman Mud Motors can be configured for:

• Vertical drilling
• Directional drilling
• Horizontal drilling
• Slide drilling
• Rotary-assisted directional drilling
• Kick-off operations
• Azimuth correction
• Deviation correction
• Sidetracking
• Window milling support
• Coring
• Reaming
• Underreaming support
• Workover drilling
• Extended-reach drilling
• Hard-formation drilling
• Soft-formation high-ROP drilling

The exact motor configuration must be selected from the formation, bit, hydraulic and directional requirements.

Main Motor Assemblies

Bypass Valve Assembly

The bypass or dump valve controls drilling-fluid communication between the internal motor bore and the annulus during running and circulation.

Its functions can include:

• Allowing the drillstring to fill while running in hole
• Allowing fluid drainage while pulling out
• Directing drilling fluid through the power section when operating pressure is established
• Reducing trapped-fluid handling issues

The valve opening and closing pressure must be matched to the drilling program and circulation system.

Power Section

The power section contains the rotor and stator.

The rotor is a precision-machined helical metallic component. The stator consists of an outer steel housing with an internal elastomer profile.

Power-section performance is influenced by:

• Rotor and stator lobe configuration
• Number of stages
• Power-section length
• Rotor-to-stator interference
• Drilling-fluid flow rate
• Differential pressure
• Elastomer temperature
• Drilling-fluid chemistry
• Solids concentration
• Motor operating time

An extended power section provides additional active length and can increase available torque and power when properly matched to the hydraulic system.

Transmission Assembly

The transmission assembly converts the eccentric rotation of the rotor into concentric rotation at the drive shaft.

Depending on the motor design, the assembly may use:

• Universal joints
• Flexible shafts
• Connecting rods
• Anti-friction connecting mechanisms
• Sealed or drilling-fluid-lubricated components

The transmission system must accommodate cyclic bending and torque while transferring power to the bearing section.

Adjustable Bent Housing

The adjustable bent housing provides a controlled angular offset between the upper motor body and lower tool axis.

The listed Goldenman design can be adjusted from:

• 0°
• Intermediate project-specific settings
• Up to 3°

A lower bend angle generally produces a lower build tendency and smoother BHA behaviour.

A higher bend angle can increase directional response but may also increase:

• Bending stress
• Housing contact
• Rotational vibration
• Tool wear
• Torque fluctuation
• Difficulty rotating the complete drillstring

The selected angle should be based on the planned dogleg severity, BHA geometry and drilling procedure.

Bearing Assembly

The bearing section supports:

• Weight on bit
• Hydraulic thrust
• Radial bit loading
• Torque transmission
• Bending loads
• Dynamic drilling loads

The maximum allowable weight on bit must not be exceeded.

Bearing-section selection should account for bit type, hole size, formation, expected vibration and operating differential pressure.

Drive Shaft and Bit Box

The drive shaft transmits motor torque to the bit box.

The bit-box connection must match the selected drill bit and provide the required:

• Torque capacity
• Tensile capacity
• Bore
• Shoulder dimensions
• Connection condition
• Make-up torque

Connection orientation and exact pin or box configuration must be confirmed on the approved motor drawing.

Model Range

The existing Goldenman page covers the following K7LZ motor series.

Model	Motor OD	Nominal Tool Size	Typical Flow Range	Bit Speed
K7LZ95×7.0	95 mm	3-3/4 in	5–10 L/s	60–130 rpm
K7LZ120×7.0	120 mm	4-3/4 in	10–20 L/s	50–100 rpm
K7LZ165×7.0	165 mm	6-1/2 in	19–38 L/s	46–92 rpm
K7LZ172×7.0	172 mm	6-3/4 in	22–38.5 L/s	50–100 rpm
K7LZ197×7.0	197 mm	7-3/4 in	33.5–56.7 L/s	50–80 rpm
K7LZ244×7.0	244 mm	9-5/8 in	42–70 L/s	40–70 rpm

The original page labels the flow row as GPM, but the listed numerical ranges correspond more logically to liters per second. The unit must be confirmed against the original factory datasheet before publication.

Reconstructed Performance Specifications

The following table has been reconstructed from the existing page because the current HTML row labels are misaligned. All values must be checked against the approved Goldenman motor specification sheet before quotation.

Model	Pressure Drop per Stage	Rated Output Torque	Stall Torque	Recommended WOB	Maximum WOB	Maximum Power
K7LZ95×7.0	2.0 MPa	1,000 N·m	1,600 N·m	30 kN	60 kN	13.6 kW
K7LZ120×7.0	1.8 MPa	2,770 N·m	4,430 N·m	55 kN	100 kN	29 kW
K7LZ165×7.0	2.4 MPa	5,750 N·m	9,200 N·m	90 kN	180 kN	73 kW
K7LZ172×7.0	2.4 MPa	6,000 N·m	9,600 N·m	150 kN	300 kN	62.8 kW
K7LZ197×7.0	2.4 MPa	11,000 N·m	17,600 N·m	200 kN	380 kN	92.2 kW
K7LZ244×7.0	2.4 MPa	15,000 N·m	24,000 N·m	210 kN	400 kN	110 kW

The pressure-drop values appear to represent pressure drop per power-section stage rather than total motor operating pressure. Final total allowable differential pressure must be confirmed for the selected number of stages and stator configuration.

Reference Length and Connection Data

Model	Reference Length	Upper Connection Reference	Lower/Bit Connection Reference
K7LZ95×7.0	5.8 m	2-7/8 REG	2-7/8 REG
K7LZ120×7.0	6.2 m	3-1/2 REG	3-1/2 REG
K7LZ165×7.0	7.6 m	4-1/2 REG	4-1/2 REG
K7LZ172×7.0	6.7 m	4-1/2 REG	4-1/2 REG
K7LZ197×7.0	6.9 m	5-1/2 REG	6-5/8 REG
K7LZ244×7.0	7.8 m	6-5/8 REG	6-5/8 REG

The original webpage contains connection values but not clear pin/box orientation. The final upper and lower connection designation, orientation and make-up torque must be confirmed in the approved motor drawing.

Standards and Certification Positioning

The current API Spec 7-1 Monogram licensing scope does not list Downhole Motors as an eligible API 7-1 product category. The present API 7-1 list covers products such as Kelly Valves, Kellys, Drill Stem Subs, Drill Collars, HWDP, drill bits and Stabilizers.

For this reason, this product page should not describe the motor as an “API 7-1 Monogram Downhole Motor.”

Recommended wording is:

• Manufactured under Goldenman’s applicable API-certified quality system
• Supplied with certification documents according to the actual certificate scope
• Rotary shouldered connections manufactured and inspected according to applicable connection requirements
• Product performance manufactured according to the approved Goldenman motor datasheet and purchase specification

The exact Goldenman API certificate number and licensed product scope should be displayed separately.

How to Select the Correct Mud Motor

1. Match the Motor OD to Hole and Casing Clearance

The motor outside diameter must be compatible with:

• Open-hole diameter
• Casing and liner ID
• Restriction ID
• Stabilizer gauge
• Fishing clearance
• Planned BHA components
• Expected cuttings size
• Annular flow area

A larger motor can generally provide greater torque but reduces annular clearance.

Insufficient clearance can increase:

• Annular pressure loss
• Cuttings accumulation
• Sticking risk
• Housing wear
• Difficulty running through restrictions

2. Match Flow Rate to Mud Pump Capacity

The motor requires sufficient drilling-fluid flow to generate the desired speed and power.

Provide:

• Available mud pump flow
• Pump pressure
• Standpipe-pressure limitation
• Drillstring pressure loss
• Bit nozzle pressure loss
• Expected motor pressure drop
• Drilling-fluid density
• Rheology
• Solids concentration

The motor should not be selected using maximum flow alone. The complete circulating system must remain within the rig’s pump and standpipe limits.

3. Select Torque and Speed for the Bit

Different bits require different torque-speed characteristics.

A higher-speed configuration may be suitable for:

• Smaller bit sizes
• Softer formations
• Selected roller-cone applications
• Higher rotary-speed requirements

A lower-speed, higher-torque configuration may be preferred for:

• PDC bits
• Hard or interbedded formations
• Larger bit diameters
• Directional drilling
• Applications with high torque demand

The motor, bit and formation should be selected as one drilling system.

4. Confirm Total Motor Differential Pressure

Torque increases as motor differential pressure increases within the approved operating range.

However, operating above the permitted differential pressure can cause:

• Stator elastomer damage
• Rotor-stator slip
• Excessive heat generation
• Transmission overload
• Bearing damage
• Premature power-section failure

Surface standpipe pressure should be monitored against off-bottom pressure to estimate operating differential pressure.

5. Select the Bent-Housing Angle

Provide:

• Planned build rate
• Required dogleg severity
• Hole size
• Motor length
• Stabilizer placement
• Bit-to-bend distance
• Slide and rotate drilling ratio
• Formation tendency
• Maximum allowable toolface correction

The maximum 3° setting should not be selected automatically. A larger angle can increase directional response but may reduce smooth rotary performance.

6. Confirm Drilling-Fluid Compatibility

The stator elastomer is directly exposed to drilling fluid.

Provide:

• Water-based, oil-based or synthetic-based mud
• Oil/water ratio
• Aromatic content
• Chloride concentration
• Mud weight
• Solids content
• Chemical additives
• Bottom-hole circulating temperature
• Static temperature
• H₂S exposure

Incorrect elastomer selection can cause swelling, hardening, debonding, loss of interference or rapid wear.

Stator Elastomer Selection

The stator compound is one of the most important factors affecting Mud Motor performance.

Selection should consider:

Operating Factor	Potential Effect
High temperature	Accelerated ageing and loss of mechanical properties
Oil-based mud	Swelling or softening of incompatible elastomers
Aromatic hydrocarbons	Increased chemical attack
High solids	Abrasion and internal wear
Excessive pressure drop	Heat generation and elastomer stress
Long static exposure	Permanent deformation or swelling
H₂S	Material and safety compatibility requirements
Incorrect rotor interference	Reduced torque or excessive heat

The purchaser should provide actual mud-test data rather than only stating “OBM” or “WBM.”

Standard vs Extended Power Section

Standard Power Section

A standard power section may be suitable where:

• Conventional torque is adequate
• Tool length must be controlled
• Pump pressure is limited
• Formation severity is moderate
• Standard BHA performance is required

Extended Power Section

An extended power section can provide additional active rotor-and-stator length.

It may be selected for:

• Higher torque demand
• Larger PDC bits
• Hard formations
• Increased mechanical power
• Improved low-speed performance
• Higher required ROP

An extended section also increases:

• Tool length
• Total pressure drop
• Hydraulic demand
• Stator heat generation potential
• Handling and transportation requirements

The pump system must be checked before selecting an extended motor.

Straight Motor vs Adjustable Bent Motor

Comparison	Straight-Housing Motor	Adjustable Bent-Housing Motor
Primary use	Vertical or rotary drilling	Directional and slide drilling
Housing angle	0°	Adjustable from 0° to 3°
Directional response	Limited	Project-specific build capability
Rotary smoothness	Generally higher	Depends on selected bend angle
Housing contact	Lower	Can increase with bend angle
Toolface control	Not primary function	Important during slide drilling
BHA modelling	Recommended	Essential for directional planning

The final motor geometry should be included in the BHA directional model.

Replacement Power Sections and Spare Parts

Goldenman can supply:

• Rotor
• Stator
• Complete power section
• Bypass valve parts
• Transmission components
• Adjustable housing parts
• Drive shaft
• Radial bearings
• Thrust bearings
• Bearing sleeves
• Seals and O-rings
• Bit box
• Top sub
• Repair and overhaul kits

Replacement rotor and stator assemblies must be matched by:

• Motor model
• OD
• Lobe configuration
• Number of stages
• Rotor lead
• Stator profile
• Interference
• Elastomer compound
• Operating temperature
• Drilling-fluid type

A rotor or stator should not be ordered using only the motor outside diameter.

Replacement Motor Compatibility

For replacement of an existing motor, provide:

• Existing manufacturer
• Motor model
• Serial number
• Motor OD
• Overall length
• Upper connection
• Bit-box connection
• Stabilizer OD and location
• Bend angle
• Bit-to-bend distance
• Flow range
• Speed range
• Rated torque
• Stall torque
• Maximum differential pressure
• Maximum WOB
• Rotor and stator information
• Mud type and temperature
• Existing dimensional drawing

Two 6-3/4 in Mud Motors may fit the same hole but have substantially different torque, speed, bend geometry and hydraulic requirements.

Common Operating Risks

Motor Stall

A stall occurs when bit resistance prevents the rotor from turning while drilling-fluid pressure continues to increase.

Repeated or prolonged stalls can damage:

• Rotor and stator
• Transmission components
• Bearings
• Drive shaft
• Bit cutters

The operator should monitor differential pressure and follow the approved stall-recovery procedure.

Excessive Flow Rate

Operating above the approved flow range can produce:

• Excessive bit speed
• Increased erosion
• Bearing overload
• High hydraulic pressure loss
• Rapid stator wear

Insufficient Flow Rate

Insufficient flow can reduce:

• Rotor speed
• Bit cleaning
• Available power
• Motor cooling
• Hole cleaning

Excessive Weight on Bit

Applying more than the approved WOB can overload the thrust bearing and increase the risk of bearing or drive-shaft damage.

High Bottom-Hole Temperature

High temperature can reduce elastomer strength and change rotor-to-stator interference.

The operating temperature must include both formation temperature and heat generated by hydraulic differential pressure.

Inspection and Quality Control

Goldenman inspection activities can include:

• Material certificate review
• Heat-number traceability
• Body and sub dimensional inspection
• Ultrasonic testing of critical metallic components
• Magnetic-particle inspection
• Hardness testing
• Rotor profile inspection
• Rotor surface and coating inspection
• Stator profile inspection
• Elastomer batch identification
• Rotor-to-stator fit verification
• Adjustable-housing angle verification
• Connection dimensional inspection
• Rotary shouldered connection gauging
• Bearing assembly inspection
• Bypass-valve functional test
• Pressure and leakage test
• No-load rotation test
• Performance test where specified
• Product marking inspection
• Final documentation review

The exact test scope should be confirmed in the approved inspection and test plan.

Factory Acceptance Test

The agreed FAT may include:

• Approved datasheet review
• General arrangement drawing verification
• Material traceability review
• Motor OD and overall length inspection
• Connection inspection
• Bent-housing angle verification
• Bypass-valve functional test
• Rotor and stator assembly inspection
• Bearing-section rotation check
• Internal pressure test
• Leakage inspection
• No-load functional test
• Flow, speed, torque or differential-pressure performance test where ordered
• Product marking verification
• Documentation review

Performance-testing requirements and acceptance limits must be agreed before manufacturing.

Available Documentation

The project documentation package can include:

• Goldenman API certificate according to actual licensed scope
• Quality-system certificate
• Certificate of Conformity
• Approved product datasheet
• General arrangement drawing
• BHA interface drawing
• Material certificates
• Heat-treatment records
• NDE reports
• Hardness report
• Dimensional inspection report
• Connection inspection report
• Rotor inspection record
• Stator elastomer identification
• Bent-angle inspection record
• Pressure and leakage test report
• Functional test report
• Performance test report when ordered
• Operation and maintenance manual
• Recommended spare-parts list
• Packing list
• Third-party inspection report

Frequently Asked Questions

Is a Downhole Mud Motor an API 7-1 Monogram product?

The current API Spec 7-1 Monogram licensing list does not include Downhole Motors as an eligible product category.

The page should therefore not claim that the motor itself carries an API 7-1 Monogram unless Goldenman can provide a separate, explicitly applicable API product scope. API certification and connection compliance must be described according to the actual certificate and documentation.

How should the correct Mud Motor size be selected?

Motor OD should be selected from the hole size, casing restrictions, annular clearance, required torque, bit size and available flow rate.

The largest motor that physically fits the hole is not automatically the best choice because annular pressure loss, cuttings clearance and fishing requirements must also be considered.

How do flow rate and differential pressure affect motor output?

Flow rate primarily affects rotor and bit speed.

Differential pressure across the power section is closely related to torque. Increasing pressure within the approved operating range increases torque, but exceeding the allowable differential can damage the stator, transmission and bearings.

Is the listed pressure drop the total allowable motor pressure drop?

The existing table appears to list pressure drop per stage rather than total motor differential pressure.

The allowable total pressure drop depends on the selected number of stages, rotor-stator design and elastomer. It must be confirmed in the final model datasheet.

When should an extended power section be selected?

An extended power section may be selected when the operation requires greater torque or mechanical power.

The rig must also have sufficient pump pressure and flow capacity, and the longer tool must remain compatible with the planned BHA and directional response.

Can one stator elastomer be used with every drilling mud?

No.

Water-based, oil-based and synthetic-based mud systems can affect elastomers differently. Temperature, aromatic content, salinity, oil ratio and chemical additives must be reviewed before selecting the stator compound.

What causes a Mud Motor to lose torque?

Possible causes include:

• Worn rotor or stator
• Loss of rotor-to-stator interference
• Elastomer swelling or damage
• Excessive temperature
• Incorrect flow rate
• Internal bypass leakage
• Abrasive solids
• Operating beyond the pressure limit
• Transmission wear

Surface pressure records and teardown inspection should be reviewed together.

Can a 6-3/4 in motor directly replace another 6-3/4 in model?

Not automatically.

The flow range, torque, speed, overall length, bend setting, bit-to-bend distance, stabilizer position, connections and elastomer may differ.

A dimensional and hydraulic comparison is required.

How should the adjustable bent angle be selected?

The angle should be selected from the desired build rate, hole size, motor geometry, stabilizer placement, formation tendency and slide-drilling plan.

Using the maximum angle can increase directional response but may also increase housing contact, vibration and rotary stress.

What data are required to order a replacement rotor and stator?

Provide the motor manufacturer, model, serial number, OD, lobe configuration, number of stages, rotor and stator dimensions, elastomer type, operating temperature and drilling-fluid composition.

A used stator may be swollen or worn and should not be the only dimensional reference.

Information Required for Quotation

Please provide:

• Hole size
• Bit type and bit size
• Required motor OD
• Vertical, directional or horizontal application
• Straight or adjustable bent housing
• Required bend angle
• Required build rate
• Available drilling-fluid flow
• Available standpipe pressure
• Drilling-fluid density
• Drilling-fluid type
• Oil/water ratio where applicable
• Solids concentration
• Maximum circulating temperature
• Maximum static temperature
• Required bit speed
• Required output torque
• Maximum weight on bit
• Standard or extended power section
• Upper connection
• Bit-box connection
• Stabilizer requirement
• Bit-to-bend distance requirement
• H₂S conditions
• Required spare power section
• Required bearing and seal kits
• Inspection and performance-test requirements
• API certificate documentation requirement
• Third-party inspection requirement
• Quantity
• Destination country
• Required delivery schedule

For replacement motors, also provide the existing nameplate, run data, dimensional drawing and teardown report when available.

Request a Technical Quotation

Goldenman supplies Positive Displacement Downhole Mud Motors for vertical, directional, horizontal, sidetrack, coring and reaming applications.

Available K7LZ models cover outside diameters from 95 to 244 mm, with straight or adjustable bent housings, standard or extended power sections and project-specific elastomer options.

Send your hole size, bit, flow rate, pump pressure, torque, speed, bend-angle and drilling-fluid requirements to:

Email: info@goldenman.com

Goldenman will review the BHA and hydraulic requirements and prepare the recommended motor model, performance datasheet, dimensional drawing and commercial quotation.