How to choose the right downhole motor part 2

The Influence of the type of mud for downhole motor

If used in salt water mud, corrosion resistance of the conventional rotor less effective, lead to the mud motors failure in serious condition, also direct impact on the life of the mud motors.

Corrupted Rotor

Rotor coating:

Surface spray coating:

To adapt mud motor to a variety of drilling mud , but costs are high, the coating is 10 times than the normal, more saturated salt water mud conditions in use. 

Chrome coating rotor

Thick rotor coating process:

Common technology on chrome-coating depending on the surface shape of the rotor creates large tolerance between actual streamline and the academic streamline of the rotor, which will reduce the efficiency of the power section. Special chroming coating technics by landrill will control the rate between apex and vale of the coating control to 1:3, Best of up to 1:1

Rotor coating technology

High-temperature and oil resistant applications reports

User :XXX drilling  company 

Place :CHINA

Well type :horizontal 

Lithology:Yingcheng, gray mass conglomerate 

Oil content: Diesel fuel 86% 

Downhole Model:High-temperature 150℃、oil resistant 

Tricone bit selection :HUGHES Tricone bit 6"MXDS55DX） nozzzle：3Xф16

MUD MOTOR USING REPORT

Choose right mud motor according to the flow rate and the power of Mud pump

Hollow rotor mud motor

To increase hydraulic horsepower and upward speed of mud stream, rotor is manufactured into hollow rotor with nozzles. Thus, motor total flow rate is equal to the sum of the flow rate  through seal  cavity and rotor. Each type of motor has  its own recommended  maximum and    minimum flow rate value. If flow rate  is too high, rotor may be running at over speed, earlier   damage would occur onto stator and rotor. If it is too low, motor will stop operating. Therefore,  the flow rate through seal cavity shall be ensured or even higher than the recommended            maintenance value, while selecting nozzle size. Only in this way, can mud motor be kept in normal   operation. 

When mud density, nozzle size and total flow  rate is a constant value, the flow rate through nozzle and seal cavity always changes with the load. On bit leaving hole bottom ,the load is approximately zero . Whereas, the flow rate becomes minimum through nozzle on the rotor, but the flow rate becomes maximum through the seal cavity. While the bit dropping down, motor pressure loss will continuously increase, and the flow rate through rotor nozzle will become higher, but the flow rate through the seal cavity will become lower.

The principle of choosing ABH or fixed mud motor

1. Stepless adjustment of sub-grade and two structural adjustment.

2. Adjustable Bend Housing mud motors advantages:

The angle of housing can adjust at wellhead of Drilling platform Motors can be used either for straight use as a bend motors

Adjustable bend housing:

Our company is the production of adjustable bent housing mud motor with adjustable angle range of 0 ° -2 °, 0 ° -3 °, 0 ° -4 °.

How to choose the right downhole motor part 1

Landrill developed series of downhole motor specifications from 43-286mm , Total 24 models:43 、45、54 、60 、73 、89 、95 、102 、105、120 、127 、140、159 、165 、172 、178 、185、197 、203 、210 、216、228、244 、286mm.

How to choose the right OD of landrill mud motor ?

When drilling in downhole,the size of bit should be used according to the following list . if not, the probability of accidents will increase ,such as sticking of tool, shaft rupture and falling in well,etc..

The influenceof No. of stage and lobe for landrill mud motor

Spiral seal line on rotor is divided into single end and multi-end (stator with one more end than rotor) .The less ends the mud motor has the higher speed and the lower torque is . The more ends it has the lower torque is. The moroe ends it has the lower speed and the higher torque. We can produce the ratio is 1：2、3：4、5：6、7：8、9：10 downhole motors , shows the sectional profile of several typical motors

Division of critical temperature for working in downhole for landrill downhole motor

According to the temperature of the stator to provide the following specifications:

Note: High temperature motors for conventional wells is difficult to obtain good results

By Media offers the following specifications of the stator:

ZZJ-02 (Conventional Stator elastomer): For common mud system, the use of temperature below 120 ℃, the stator elastomer is high strength, wear resistance, long life under conventional temperature operation.

ZYN-02 (Oil Resistqancethe stator elastomer): For oil-based mud system and common mud system, temperature below 120 ℃in oil-based mud that has excellent oil capacity expansion characteristics.

ZGYN-180 (high-temperature oil-base mud the stator elastomer): use in high temperature, high oil mud system, the elastomer used under the conditions of 180 ℃and high oil content, the show results: high-oil-resistant adhesive strength under high temperature , tear strength and other properties remain high, plus a reasonable amount of interference co-ordination, oil-resistant rubber in high-temperature, high-oil-based mud conditions can have a better use of results, now in the Liaohe, Daqing, Xinjiang oilfield successful running.

powerful downhole motor for directional drilling

Downhole motor is a kind of downhole dynamic drilling tools, which is supplied the power from drilling mud. mud motor is placed in the drill string to provide additional power to the bit while drilling. The PCPD pump uses drilling fluid to create eccentric motion in the power section of the motor which is transferred as concentric power to the drill bit (well). The mud motor uses different rotor and stator configurations to provide optimum performance for the desired drilling operation, typically increasing the number of lobes and length of power assembly for greater horsepower. In certain applications, compressed air, or other gas, can be used for mud motor input power.

Landrill downhole motor

Mud motor is made by drive shaft assembly、universal coupling assembly、motor assembly、anti-drop assembly and outlet valve assembly .

mud motor

Basic principle

Based on the principle developed by Rene Moineau, the theory states that a helical rotor with one or more lobes will rotate eccentrically when the stator contains more lobes than the rotor. The flow of the fluid transmits power allowing the assembly to rotate and turn the bit.

Normal construction

Normal mud motor construction consists of a top sub, which connects the mud motor to the drill string; the power section, which consists of the rotor and stator; the transmission section, where the eccentric power from the rotor is transmitted as concentric power to the bit using a constant-velocity joint; the bearing assembly which protects the tool from off bottom and on bottom pressures; and the bottom sub which connects the mud motor to the bit.

When the bit is bottomed and the mud motor is effectively working, there is a notable increase in the pressure in the fluid system. This is caused by a restriction within the mud motor and is termed the "differential pressure". If this differential pressure is too high then the mud motor can stall which means the bit has stopped turning and this can cause severe damage to the internal surface of the stator.

A mud motor is described in terms of its number of stages (usually three), lobe ratio and external diameter. Stages are the number of full twists that the stator makes from one end to the other and the lobe ratio is the number of lobes on the stator, to the number of lobes on the rotor (the stator always has one more lobe than the rotor). A higher number of stages or the number of lobes indicates a more powerful motor, capable of producing more torque. A lower number of lobes indicates a reduction in the torque produced but a faster bit rotation speed.

The operating parameters include flow rate, bit rpm and torque. The relationship between the rotor and the stator geometry determines the rotational speed and torque. The rotational speed is proportional to the flow rate and torque is proportional to the pressure drop in the fluid as it flows through the motor. The more lobes the higher the torque and the slower the rpm.

The use of mud motors is greatly dependent on financial efficiency. In straight vertical holes, the mud motor may be used solely for increased rate of penetration (ROP), or to minimize erosion and wear on the drill string, since the drill string does not need to be turned as fast.

The majority of mud motor use is in the drilling of directional holes. Although other methods may be used to steer the bit to the desired target zone, they are more time consuming which adds to the cost of the well. Mud motors can be configured to have a bend in them using different settings on the motor itself. Typical mud motors can be modified from 0 degrees to 4 degrees with approximately six increments in deviation per degree of bend. The amount of bend is determined by rate of climb needed to reach the target zone. By using a measurement while drilling (MWD) tool, a directional driller can steer the bit to the desired target zone.

Steerable motors are used to drill the kick off point. When drilling the kick off point be sure to avoid drilling a soft formation immediately below a hard one. In hard abrasive formations the high side forces at kick off can cause severe bit shank wear. Ideally the kick off point should be selected in a non-abrasive homogenous formation.

Advantages

• Extremely hard rock formations can be drilled with mud motors using diamond or PDC bits.

• High penetration rates can be achieved since rotation speeds are high.

• Will allow circulation of the borehole regardless of the horsepower or torque produced by the mud motor.