Screw downhole motor: characteristics, device, operating rules

The oil and gas industries need special equipment. ). For the organization of the working cycle, a screw downhole motor (PDM ) is often used. It participates in the process of extraction of liquid and gaseous, as well as solid minerals, and can also be used in the process of repairing existing wells.

Special equipment has a number of special technical characteristics. In order for the unit to fully perform the functions assigned to it, it must be properly selected in accordance with the existing operating conditions. To do this, it is necessary to understand the device design of the PDM, as well as the rules for its use at various sites.

general characteristics

применяется в добывающей промышленности для осуществления бурения глубоких, наклонно-направленных, горизонтальных и вертикальных скважин. The screw downhole motor is used in the mining industry to drill deep, directional, horizontal and vertical wells. It allows you to drill corks from sand, salt deposits, cement bridges.

To the engine could perform its functions, it has a certain torque. Depending on its technical characteristics, the equipment can destroy rocks at the required speed. This ensures high efficiency of the technological cycle.

The diameter of the PDM can be from 54 to 230 mm. The construction uses strong, but elastic teeth. This allows to provide high rigidity of the structure for bending, to reduce the leakage of liquids during their pumping.

началось в 1962 году. Production of screw downhole motors began in 1962. It was produced by the American manufacturer Dine-Drill. It was a single-screw pump. A similar design was invented in 1930 by the French engineer Muano.

The characteristics of the first HDR differed somewhat from modern units. He provided efficient inclined drilling. At the same time, its speed was 200 rpm. In 1966 domestic technologists created an assembly that was characterized by a quiet pace. He had the ability to adjust the speed from 100 to 200 rpm.

Over time, the device was improved. There were many varieties of such equipment. They are used in various branches of the extractive industry. To ensure proper drilling in different conditions, the design and operation of the PDM may differ slightly. However, the main principle of work remains the same for all varieties.

Design

The design of the presented equipment may be slightly different. Этот прибор является симметричным роторным оборудованием. For example, you can consider the device of a screw downhole motor DR 95. This device is a symmetrical rotor equipment. At its work, a gearing of an oblique type is used. The mechanism is driven by the pressure of the liquid being supplied.

The design consists of an engine assembly, as well as a working part. The first element of the system is the main power component. It is on its characteristics that the operational characteristics of the equipment depend. These include power, efficiency, torque, as well as the rotor speed.

The motor assembly consists of a stator (housing) and an elastomeric threaded insert. The rotor is engaged for it. The fluid starts to rotate. The elastic sheath divides the chamber into two cavities. It is made of durable rubber, resistant to wear. When abrasive particles hit the surface of the material, it does not collapse.

влияет множество факторов. Many factors influence the performance of a screw downhole motor . The rotor structure has the form of a drill. Its coating is very durable, made of alloy steel. The number of teeth at the rotor is one less than that of the stator. The motor assembly has a certain tension of the gearing. It depends on the characteristics of the working fluid, operating temperature, etc.

The operating elements are represented by a spindle knot and an angle adjuster. The first of these transmits the torque to the working tool. It undergoes significant axial loads. The spindle unit has a body and two supports. A shaft is attached to them. The node can be open or closed.

Operating principle

определяется особенностями конструкции. The principle of operation of a screw downhole motor is determined by the design features. These are three-dimensional rotary machines. The stator of their engine with cavities adjoins the chambers of low and high pressure. The screw-rotor is the leading one. Through it the torque is transmitted to the actuator.

The closing screws are called the driven elements of the structure. They compact the engine. With the help of the contactors, the liquid from the high-pressure chamber is prevented from entering into the low-pressure compartment.

The liquid circulates inside the structure through the working parts. This movement is possible due to pressure drop. At the same time, the torque is applied to the rotor. The screw elements of the working bodies are mutually closed. They separate the high and low pressure areas.

похож на работу поршневых разновидностей оборудования. Therefore, the principle of operation of a screw downhole motor is similar to the operation of piston types of equipment. In the working bodies of the PDM, separate gateways are created. For this, the number of stator teeth is determined by a large one by one than the rotor (internal element). The length of the working elements can not be less than the pitch of the helical surface of the outer element. This determines the normal functioning of the system. And the ratio of the steps of the outer and inner surfaces of the screw is proportional to the ratio of the number of teeth. Their profiles are characterized by a mutually bent shape. This allows them to be in continuous contact at any part of the clutch.

Multiplicity is one of the main parameters of the equipment operation. PDMs of domestic production have multi-input working bodies. Foreign companies produce the presented engines with one or several rotor approaches.

Classification

In accordance with various factors, the classification of screw downhole motors takes place . On the basis of application, there are three main categories of PDMs:

1. Units for drilling in the vertical direction. They have direct execution. The external diameter of such aggregates is from 172 to 240 mm.
2. Equipment for horizontal and directional drilling. Such engines have a twisted layout. The diameter can be from 76 to 240 mm.
3. Devices for repair and restoration works. They have direct execution. The outer diameter is from 43 to 127 mm.

127, 88, 76, 43 мм может иметь прямое исполнение. The power units can have an active part up to 550 cm in length. The screw downhole motor 105, 127, 88, 76, 43 mm can be directly executed. Also devices with a possibility of adjusting the angle of inclination are produced. This also allows for inclined or horizontal drilling. Power units are used to create a vertical well. Their outer diameter, power should be greater. Dimensions for such units can not be less than 178 mm.

The most simple and inexpensive variants of the presented equipment are the PDMs for well workover. These are reliable units, equipped with torsion transmission, rubber mounts.

Drilling equipment is additionally equipped with anti-emergency units. This allows you to exclude the leaving of parts on the face in the event of a breakdown. The spindle compartments of the engines for inclined and horizontal drilling have radial carbide supports in their composition. Their bearings have a high load capacity.

Filters-slurry catchers, calibrators, centralizers, reverse and overflow valves can be added to the PDM design. Also in the delivery set may include various spare parts.

Number of sections

может иметь одну, две или три секции. A screw downhole motor may have one, two or three sections. This determines the features of the design and operation of the device. Single-section varieties are indicated by the letter "D". They consist of a spindle and motor section. Also in the design there is an overflow valve.

Single-section structures have a direct design and are used most often for the repair of wells. Due to the features of the mechanism, the use of special seals drilling is possible with pressure drops on the bit to 8-10 MPa. Single-section constructions are made in our country and abroad. They are widely used in modern extractive industries.

могут иметь определенные особенности конструкции. Sectional screw downhole motors for drilling wells may have certain design features. Their use is considered more appropriate. Single-section varieties significantly lose their energy characteristics when screw pairs are worn.

Multisectional types of equipment today are more popular. Due to the peculiarities of their design, the load on working couples is reduced. The consumption of drilling mud is also reduced. Depending on their class, there are 2 letters in the designation. Engines of the "DS" type can be used for drilling inclined and vertical tunnels for various purposes. Their drilling mud can not have a temperature above 373 K.

The "DG" series is shorter. The required power and resource is provided by a two-step power section. In such designs, various mechanisms of body curvature are used. Can be equipped with centering devices.

The series "TO" is represented by the deviators. They have a hard curve sub. The angle of curvature of the spindle section is unregulated. Used to create inclined tunnels. Devices such as "DR" have a regulator of the angle of curvature.

Turboprop variants

. Relatively new type of equipment are turbine-screw downhole motors . They are characterized by high resistance and high energy efficiency. This kind of aggregates is sometimes referred to the class of gearbox turbodrills.

The screw pair is assigned the function of a reducer and a stabilizer. This allows the bit to be optimized under load. The design of turbine-screw varieties is highly complex. When you create it, you need a lot of material. Therefore, the cost of the presented equipment remains high. However, its working life exceeds the usual varieties of PDMs.

The screw pair of the presented units can be mounted above the section of turbines or between it and the spindle compartment. The first option is simpler. The aggregate consists of only one joint node in this case. The second version of the screw pair is less reliable because of its complexity. Here it is necessary to create two rotary joint nodes.

Characteristics of PDMs

определяют их характеристики. Features of drilling with screw downhole motors determine their characteristics. They must be taken into account for the correct choice of drilling parameters. The conditions for stable drilling must be maintained throughout the entire production process. Today, the BPMs are being improved in accordance with the existing requirements of the extractive companies.

The characteristics of the equipment are constantly improving. This allows us to correctly apply new technologies in the extractive industry. In today's world, adjustable pump drives have been used. Drilling can be carried out in inclined and horizontal directions. The method using continuous tubes is also used. To ensure the high productivity of new processes, the characteristics of the equipment are investigated in various ways.

In the development of the drilling program, bench tests are performed on the PDM. This allows you to identify their actual performance parameters. This entails additional costs to the manufacturer. However, the equipment is used more efficiently. Production cycles are organized harmoniously. By pressure, which is present in the riser, you can control the load of the bit. This entails an increase in drilling efficiency.

могут иметь статические или динамические характеристики. Screw downhole motors for drilling wells can have static or dynamic characteristics. In the first case, the dependence between the observed variables in the steady-state regimes is reflected. Dynamic characteristics reflect the ratio of indicators in unstable regimes. They are caused by the inertia of the observed processes.

Bench and load characteristics

требует соблюдения установленных производителем оборудования правил и норм. Drilling with screw downhole motors requires compliance with the rules and regulations established by the equipment manufacturer. They are determined by bench or load characteristics. In the first case, torque functions are tested in the production. Load characteristics are determined after bench tests for specific conditions for creating wells.

As the torque increases, a certain pressure drop is created. This indicator increases linearly. The speed of rotation at the beginning of the test decreases slightly. When approaching a complete stop, the drop occurs abruptly. The curves of the total efficiency and power have an extreme form.

Testing is performed in four main modes (optimal, idle, extreme and braking). The working conditions of the PDM during the investigation under production conditions are extreme conditions. In accordance with this regime, the passport data of the equipment are indicated.

It is considered optimal if the unit is used in modes that are shifted to the left from extreme operating conditions. The torque in this case will be less important. In the extreme operating mode, the most effective fracture of rocks is determined. The boundary of this mode passes next to the zone of stability of the device. останавливается. With further increase in the load, drilling with screw downhole motors stops. There comes the braking mode.

Features of operation

According to the results of testing the characteristics of the equipment, rules for the operation of screw downhole motors are established. In the cold period, the mechanism is heated by steam or hot water. The washing liquid must have a certain level of viscosity and density. It should not contain sand.

When the device is lowered to a depth of 10-15 m, it is necessary to turn on the pump, wash the well zone. The engine does not turn off at this moment. If the chisel is new, it is necessary to make it run-in at a small axial load.

The tool is fed into the well smoothly. There should be no jerks. Periodically, the rotation of the PDM is performed. In this case, it is necessary to correctly set the flow rate of the washing liquid. For this, it is necessary to take into account the features of cleaning the face.

In the process of working, the working pair gradually wears out. , необходимо увеличить расход промывки. To ensure high efficiency when operating a screw downhole motor , it is necessary to increase the washing rate. It should be 20-25% higher at the end of the job compared with the initial level.

To ensure that the engine does not accumulate sludge, it is necessary to flush the well before increasing the capacity or raising it when changing the bit. Only after this, the tool is lifted over the bottom zone at 10-12 m. After that, you can stop the pump, open the valve.

Also, during the operation of the equipment, it is necessary to check its operation. The engine is sent for maintenance at the set frequency. With a decrease in its power, performance, equipment is sent for repair. This procedure is also necessary when the spindle clearance is increased. Also, the engine maintenance procedure is performed when it is smeared or unable to start over the well.

Finally

должен обладать определенной скоростью потока моющей жидкости. The screw downhole motor must have a certain flow rate of the cleaning liquid. The more blades the rotor has, the greater the amount of flushing required during the operation of the equipment. However, this leads to an increase in the wear of the unit.

When there is no load on the equipment (when lifting from the well), the pressure inside falls. If the rotor is suspended, bring equipment heavier. This requires a huge amount of energy.

When the load on the PDM increases, at the beginning of the procedure, a pressure drop occurs. However, it is restored when the rotor is untwisted.

When operating the unit, it is necessary to take into account the maximum permissible pressure in the working unit. If the specified line is exceeded, the elastomer deforms. The torque will be lost. At the same time, the work can not move forward, and the working fluid will run dry through the engine.

The lowest losses of working pressure are observed with an increase in the cross-sectional area of the bit. If its size decreases, there is a rapid wear of the bearings. The flow of liquid does not have time to cool them.

его основные характеристики и условия применения, можно правильно подобрать оптимальную модель оборудования. Having considered what a screw downhole motor is, its main characteristics and application conditions, it is possible to choose the right model of the equipment correctly.