Figure 5- 1 Classification of Oil Production Methods
I. Mobile oil production
According to the energy of the reservoir itself, oil is driven from the reservoir to the bottom hole and lifted from the bottom hole to the ground. This production mode is called self-injection oil production. Oil wells produced by flowing method are called flowing wells. Flowing wells have the advantages of simple surface equipment, convenient operation, high output, fast oil recovery and good economic benefits.
(A) the principle of flowing well oil production
1. Principle The oil well can self-gush because the formation energy is sufficient. The formation energy level is reflected in the reservoir pressure level. After the formation is opened, crude oil flows from the deep part of the formation to the bottom of the well under the action of high formation pressure, which overcomes the seepage resistance of the formation, and the remaining pressure is the bottom hole pressure. Under the action of bottom hole pressure, crude oil flows from the bottom hole along the wellbore to the wellhead, and at the same time, the natural gas dissolved in crude oil begins to separate, and the gas will also become the energy for lifting crude oil.
2. Four flow processes of flowing wells
Spontaneous flow from oil reservoir to surface oil transportation station can be divided into four basic flow processes-formation seepage, wellbore multiphase pipe flow, nozzle flow and horizontal pipe flow, as shown in Figure 5-2.
(1) Formation seepage: from the oil layer to the bottom of the well, the fluid seeps in the porous medium, so it is called seepage. If the bottom hole pressure is greater than the saturation pressure, it is single-phase seepage; If the bottom hole pressure is less than the saturation pressure, it is multiphase seepage. During seepage, the pressure loss accounts for about 10% ~ 15% of the total pressure drop.
(2) Multiphase pipe flow in wellbore: vertical pipe flow. From the bottom hole to the wellhead, the fluid in the tubing rises. Generally, the pressure of a certain section of tubing is lower than the saturation pressure, so it belongs to multiphase flow of oil, gas or oil, gas and water. The pressure loss of vertical pipe flow is the largest, accounting for 30% ~ 80% of the total pressure drop.
(3) Mouth flow: The fluid passing through the throttle is called mouth flow. The nozzle velocity is high, and its pressure loss accounts for 5% ~ 30% of the total pressure drop.
(4) Horizontal pipe flow: After the fluid enters the oil pipeline, it flows along the ground pipeline and belongs to multiphase horizontal pipe flow. The pressure loss of horizontal pipe flow generally accounts for 5% ~ 10% of the total pressure drop.
Figure 5-2 Four Flowing Processes of Flowing Wells
1- formation seepage; 2- multiphase pipe flow in wellbore; 3-port flow; 4— Horizontal pipe flow
These four flow processes are interrelated and mutually restricted, and they are in the same dynamic system. The residual pressure flowing from the reservoir to the bottom hole is called bottom hole pressure (bottom hole flowing pressure). For a certain reservoir, at a certain production stage, the reservoir pressure is stable at a certain value, and then the bottom hole pressure becomes larger, and the oil well production will decrease; When the bottom hole pressure decreases, the oil well production will increase. It can be seen that the bottom hole pressure is the resistance in the oil layer seepage stage, while in the vertical pipe flow stage, the bottom hole pressure is the power to lift oil and gas out of the ground. The remaining pressure after oil and gas are pushed to the wellhead is called wellhead tubing pressure. Wellhead tubing pressure is the resistance of vertical pipe flow of oil and gas in the well and the driving force of wellhead flow.
3. Energy source and consumption in vertical pipe flow
Since the pressure loss is mainly consumed in the vertical pipe flow, the following focuses on the vertical pipe flow.
1) Single-phase vertical pipe flow
When the wellhead pressure of an oil well is greater than the saturation pressure of crude oil, the well is single-phase crude oil. Only when the pressure after flowing out of the wellhead is lower than the saturation pressure can natural gas be separated from crude oil. This oil well belongs to single-phase vertical pipe flow.
The energy source of single-phase vertical pipe flow is bottom hole flowing pressure. Energy is mainly consumed when the liquid flows from the bottom hole to the wellhead, overcoming the liquid column pressure equivalent to the well depth and the friction resistance between the vertical pipe walls. Therefore, in single-phase vertical pipe flow, the relationship between energy supply and consumption can be expressed by the following pressure balance formula:
pf=pH+pfr+pwh
Where, pf—— is the flowing pressure at the bottom of the well;
Ph- liquid column pressure;
PFR-friction resistance;
Pwh- wellhead pressure.
2) multiphase vertical pipe flow
When the bottom hole flowing pressure is lower than the saturation pressure, oil and gas enter the bottom hole together, and the whole tubing is oil-gas two-phase. When the bottom hole flowing pressure is higher than the saturation pressure, and the wellhead pressure is lower than the saturation pressure, the natural gas dissolved in oil will start to separate at a certain height in the wellbore, that is, at the saturation pressure point. There are two facies belts in the oil well, the single-phase belt below and the two-phase belt above. In the two-phase region, gas separates from oil and expands, constantly releasing the elastic expansion energy of gas and participating in lifting. Therefore, the energy source of multiphase vertical pipe flow is the pressure energy (that is, flow pressure) of liquid and gas entering the bottom hole; The second is the gas expansion energy of the free gas entering the bottom hole with the oil flow and the natural gas separated from the oil during the lifting process. There are two ways to use the expansion energy of gas: one is that the gas acts on the liquid and pushes the liquid vertically upward; The other is to bring the liquid up through the friction between gas and liquid.
(2) Flowing well oil production equipment
Flowing oil production equipment includes wellhead equipment and surface process equipment.
1. Wellhead equipment
The wellhead device of a flowing well consists of casing head, tubing head and Christmas tree from bottom to top, as shown in Figure 5-3. The wellhead device of a flowing well is the basic equipment of other kinds of oil production wells, and the wellhead devices of other oil production methods are based on this.
Figure 5-3 Flowing Well Wellhead Structure Diagram
1-wax removal gate; 2- production door; 3— Cross joint of tubing head; 4- main door; 5— Casing cross joint; 6— Casing gate; 7— Back pressure gate; 8— Lubricator; 9— Nozzle sleeve; 10- oil pressure gauge; 1 1- back pressure table; 12- casing pressure gauge; 13- check valve; 14- casing head; 15- sampling valve; 16- tubing head
1) casing head
Casing head is located at the lower end of wellhead device, which is a component connecting casing and various wellhead devices. It consists of a body, a casing hanger and a sealing assembly. Its function is to support the gravity of technical casing and reservoir casing, seal the annular space between casing layers, provide transitional connection for installing upper wellhead devices such as blowout preventer, tubing head and Christmas tree, and perform operations such as squeezing cement, monitoring well fluid and balancing fluid through two side ports on the casing head body.
2) Tubing head
The tubing head is installed between the Christmas tree and the casing head, and the upper flange surface is the datum for calculating the oil replenishment distance and well depth data. Its function is to support the gravity of tubing in oil well; Cooperate with tubing hanger to seal the annular space of tubing and casing; Provide transition for connecting casing head and connecting Christmas tree; And through the two side ports (casing valves) on the tubing head four-way body, the operations such as balanced liquid injection and well cleaning are completed.
3) Christmas tree
Christmas tree refers to the part above the tubing head, and the connection methods are flange type and clamp type. The function of Christmas tree is to control and regulate the production of oil wells, guide the oil and gas sprayed from oil wells into oil pipelines, and realize tripping of downhole tools and instruments.
The main components and accessories of the Christmas tree have the following functions:
(1) master gate: installed on the tubing head to control the passage of oil and gas flowing into the Christmas tree. Therefore, it is fully opened during normal production, and only closed when it needs to be shut in for a long time or under other circumstances.
(2) Tubing four-way (or three-way): its upper part and lower part are respectively connected with wax removal gate and main gate, and its two sides (or one side) are connected with production gate. It is not only a connecting part, but also a channel for oil and gas to flow out and downhole instruments.
(3) Production gate: it is installed on both sides of the four-way or three-way tubing to control the flow of oil and gas to the tubing. During normal production, the production gate is always open and only closed when the inspection nozzle is replaced or the oil well is closed.
(4) Wax removal gate: the gate installed at the top of the Christmas tree. Keep it open during normal production to observe the tubing pressure. It can be connected with the BOP and used for wax removal or well testing, which can be opened during wax removal or well testing, and closed after wax removal or well testing.
(5) Casing cross: its upper surface is communicated with the main valve, its lower part is connected with the casing head, and its left and right sides are connected with the casing gate. It is the main component of tubing and casing collection and shunt. Through it, the shunt between the empty oil casing and the oil casing is sealed. The external pressure is casing pressure and the internal pressure is tubing pressure.
(6) Back pressure gate: It is installed on the oil pipeline behind the choke, and closed during inspection and replacement of the choke, maintenance of the production gate and workover operations to prevent the fluid in the oil pipeline from flowing backwards. Some oil wells have installed one-way valves in this position instead of back pressure gates.
(7) lubricator: the lubricator is made of φ63mm(2.5in) tubing and sheathed with φ89mm(3.5in) tubing, which circulates steam or hot water (oil) in the annular space for thermal insulation (without thermal insulation circulation, there is no need for jacket), which has two functions in the flowing well: one is to lift the wax remover and melt the wax brought by the wax scraper before and after wax removal; Second, raise and lower various testing and well testing tools.
(8) One-way valve: to prevent the crude oil flowing from the wellhead from flowing back to the wellbore.
2. Main equipment of ground technology
Generally speaking, a set of Christmas tree which can control and adjust oil and gas production is installed in the wellhead surface flow of a flowing well; There is also a set of devices for heating and insulating oil well products and wellhead equipment, as well as devices for measuring oil and gas production, which mainly include heating furnace, oil-gas separator, high-pressure centrifugal pump and ground pipeline. This series of process equipment is also universal to other oil recovery methods.
Second, mechanical oil recovery
In the process of oilfield development, because the reservoir pressure itself is very low, or the reservoir pressure drops after a period of development, the oil well can't or can't keep flowing. Sometimes it is possible, but the output is very low, so artificial energy should be used to extract oil, that is, certain mechanical equipment (surface and underground) should be used to extract oil and gas from wells to the surface. Mechanical oil recovery can be divided into two categories: sucker rod pump oil recovery and rodless pump oil recovery.
(A) rod pump oil production
Rod pump oil production device includes beam pumping unit-deep well pump device and ground-driven screw pump oil production device.
1. beam pumping unit-deep well pump device
1) beam pumping unit
See Figure 5-4 for the structure of beam pumping unit. It is the main ground mechanical transmission device for rod pump oil production. It can be used with sucker rod and deep well pump to pump crude oil to the ground. Oil wells using pumping units are often called "pumping wells". The working feature of pumping unit is continuous operation, long-term in the field, unattended. Therefore, the requirements for pumping units should be high strength, long service life, certain overload capacity, simple installation and maintenance and strong adaptability.
Figure 5-4 Structure Diagram of Beam Pumping Unit
1 flying suspension device; 2- braids; 3- Shantou; 4- Walking beam; 5— Support shaft; 6 beam axes; 7 beams; 8- connecting rod; 9— Balance block; 10- crank; 1 1- big pulley; 12- belt; 13- motor; 14-input shaft; 15-output shaft; 16-crank pin; 17- brackets; 18 group; 19- polished rod
(1) Main component functions.
① donkey head: installed at the front end of the walking beam, its function is to ensure that the sucker rod is always aimed at the wellhead center when pumping oil. The arc of the donkey's head is centered on the support bearing and draws an arc with the forearm length of the walking beam as the radius.
(2) Walking beam: The walking beam is fixed on the bracket, with a donkey's head at the front end, which bears the underground load, and the back end is connected with the connecting rod, crank and reducer to transmit the power of the motor.
(3) Crank-link mechanism: Its function is to convert the rotating motion of the motor into the up-and-down reciprocating motion of the donkey's head. There are 4 ~ 8 holes in the crank to adjust the stroke.
(4) Reducer: Its function is to convert the high-speed rotation of the motor into the low-speed rotation of the crankshaft, and at the same time support the balance weight.
⑤ Balance block: The balance block is installed at the tail of the beam of the pumping unit or on the crankshaft. Its function is: when the pumping unit upstrokes, the balance block moves downward to help overcome the load on the donkey's head; In the downward stroke, the motor moves the balance weight upward to store energy. Under the action of counterweight, the load difference between up and down stroke of pumping unit can be reduced.
⑥ Rope hanger: It is a flexible connector connecting the polished rod and the donkey's head, and can also be used for dynamometer indicator diagram.
(2) Working principle.
The motor transmits its high-speed rotation motion to the crankshaft through the belt and gearbox, and drives the crankshaft to do low-speed rotation motion; The crank drives the walking beam to swing up and down through the connecting rod and the cross beam. The front end of the walking beam is equipped with a donkey's head, and the rope hanger hanging on the donkey's head drives the sucker rod to reciprocate vertically up and down, and the sucker rod drives the piston to move, thus pumping crude oil out of the well bore.
2) Deep well pump
Deep well pump is the core pumping equipment of oil well. It goes down into the well through sucker rod and tubing, sinks to a certain depth below the liquid surface, and sends crude oil to the ground through suction.
Deep well pump is mainly composed of working cylinder (including outer cylinder and bushing), piston, traveling valve (discharge valve) and fixed valve (suction valve). Its working principle is shown in Figure 5-5.
Figure 5-5 Working Principle Diagram of Pump
1- drain valve; 2- piston; 3— Bushing; 4- Suction valve
Upstroke: the donkey head rises, the sucker rod string rises with the piston, and the traveling valve on the piston is closed by the pressure of the internal liquid column. If the pipeline is full of liquid, a section of liquid equivalent to the piston stroke length will be discharged at the wellhead. At the same time, the pressure in the pump barrel below the piston decreases. When the pressure in the pump is lower than the sinking pressure (liquid column pressure in circular space), the fixed valve opens under the sinking pressure, and crude oil enters the pump, occupying the volume released by the piston, as shown in Figure 5-5(a).
Downstroke: When the donkey head descends, the sucker rod string moves down with the piston, the liquid sucked into the pump is compressed, and the pressure in the pump increases. When the pressure is equal to the liquid column pressure in the annular space, the fixed valve is closed due to its own weight. When the piston continues to descend, the pressure in the pump continues to rise. When the pressure in the pump exceeds the pressure of the liquid column above the piston, the float valve is pushed open, and the liquid at the lower part of the piston enters the upper oil pipe through the float valve, that is, the liquid is discharged from the pump, as shown in Figure 5-5(b).
3) sucker rod and wellhead device
(1) sucker rod.
Sucker rod is an important part of pumping unit, which is connected with pumping unit and deep well pump, and plays the role of transmitting power in the middle. The sucker rod bears a variety of loads in the working process, and the force is extremely uneven when it moves up and down, with a large force when it rises and a small force when it falls. As a result of this repeated action, it is easy to fatigue the metal and break the sucker rod. Therefore, the sucker rod is required to have high strength, wear resistance and fatigue resistance.
Sucker rods are generally rods made of solid round steel. There are rough forging heads at both ends, and there are square sections connecting threads and wrenches below. The top sucker rod of sucker rod string is called polished rod. The polished rod is used in conjunction with the wellhead sealing packing box to seal the wellhead.
(2) Wellhead device.
The wellhead device of pumping well is similar to a flowing well, and the pressure is low. It is mainly composed of casing tee (or casing tee), tubing tee (or tubing tee), rubber ram and polished rod sealing section (or sealing packing box). The number and connection mode of other accessories depend on the specific conditions of each oilfield. However, no matter what form it takes, the wellhead device of pumping well must have the functions of measuring indicator diagram, dynamic liquid level, sampling and observing pressure, and it should be easy to operate and manage. Figure 5-6 shows the water mixing wellhead device of pumping well.
Figure 5-6 Water Mixing Wellhead Device of Pumping Unit
1- rubber gate; 2- pipeline exhaust valve; 3- main door; 4— Casing test gate; 5— Casing gate; 6— Back pressure gate; 7— Straight-through valve (small circulation); 8— Hot cleaning valve; 9-water mixing valve (large circulation); 10- check valve; 1 1- mixed water control valve; 12- production of gate valves; 13- oil pressure gauge; 14- polished rod sealing section; 15- casing pressure gauge; 16- shell outlet valve
2. Ground-driven screw pump pumping device
At the end of 1970s, screw pump began to be used for crude oil exploitation. Screw pump is a positive displacement pump, which can be divided into ground-driven screw pump and underground-driven screw pump according to the driving form.
Ground-driven screw pump equipment is shown in Figure 5-7. It consists of ground drive system, sucker rod string, sucker rod string centralizer and screw pump. Its working principle is that the screw pump discharges oil through a cavity (that is, a closed cavity formed between the rotor and the stator). When the rotor rotates, the closed cavity moves axially from the suction end to the discharge end. When the closed cavity disappears at the discharge end, the crude oil in the cavity will be evenly squeezed from the suction end to the discharge end, and a new low-pressure cavity will be formed at the suction end to suck the crude oil away. In this way, closed cavities are constantly formed, moved and disappeared, and crude oil is continuously filled, squeezed and discharged, so that crude oil in the well is continuously sucked and lifted to the wellhead through tubing.
Figure 5-7 Schematic Diagram of Screw Pump Oil Production
1- electric cabinet; 2- motor; 3 belts; 4- gearbox; 5 square clips; 6— Special wellhead; 7— Casing pressure gauge; 8— sucker rod; 9— Pipeline; 10- sucker rod centralizer; 1 1 and 16- tubing centralizer; 12- stator; 13-rotor; 14- locating pin; 15- tubing anti-dropping device; 17- sieve tube; 18-casing; 19 plug
Screw pump oil production device has simple structure and small floor space, which is beneficial to oil production of offshore platforms and cluster wells. There is only one moving part (rotor), which is suitable for heavy oil wells and sand wells; Uniform displacement, no pulsation oil discharge characteristics; There are no valve parts and complicated flow channels in the valve, so the hydraulic loss is small; The actual lift of the pump is greatly influenced by the viscosity of the liquid. With the increase of viscosity, the lift of the pump is greatly reduced.
(2) Rodless pump oil production
Rodless pump oil production includes gas lift oil production, electric submersible centrifugal pump oil production, downhole driven screw pump oil production, hydraulic piston pump oil production and jet pump oil production.
1. Gas lift oil recovery
When the energy of oil and gas is not enough to maintain the flow of oil well, in order to make the oil well continue to produce oil, gas (natural gas or air) is artificially pressed into the bottom of the well, and crude oil is lifted to the ground by using the expansion energy of gas. This oil recovery method is called gas lift oil recovery. There are two kinds of gas lift modes: annular air intake mode and central air intake mode.
The wellhead and downhole equipment of gas lift oil recovery method are relatively simple, and the management and adjustment are as convenient as flowing wells.
1)
Take the air intake mode of annular space as an example. When the oil well stops production, the liquid level in the tubing and casing is in the same position. Start the compressor and inject compressed gas (air or natural gas) into the annulus of the oil sleeve, and the liquid level in the annulus will be squeezed downward (if the liquid is squeezed into the oil layer, all the liquid in the annulus will enter the oil pipe), and the liquid level in the oil pipe will rise. When the annular liquid level drops to the pipe shoe, the compressor will reach the maximum pressure, which is called the gas lift starting pressure. When compressed gas enters the tubing, the crude oil in the tubing is mixed with the gas, and the liquid level keeps rising until it is sprayed out of the ground.
Before injection, the bottom hole pressure is always greater than the reservoir pressure. After the injection, the gas is continuously pressed into the annular space, and the mixed gas liquid in the oil pipe is continuously injected, so that the density of the mixed gas liquid becomes smaller and smaller, and the pressure of the pipe shoe drops sharply. When the bottom hole pressure is lower than the reservoir pressure, crude oil will flow into the bottom hole from the reservoir. Due to the oil production in the reservoir, the proportion of mixed gas and liquid in the tubing increased slightly, so the compressor pressure rose again and stabilized after a period of time. The stable compressor pressure is called gas lift working pressure. At this time, the reservoir continues to produce oil steadily and the wellhead continues to produce oil.
2) gas lift mode
There are two ways of gas lift:
(1) annular air intake mode. This gas lift method is also called reverse lift. This means injecting compressed gas from the annular space of the oil casing and extracting crude oil from the oil pipe.
(2) Central air intake mode. It is just the opposite of the annular air intake method, that is, the gas is injected from the tubing and the crude oil is returned from the annulus of the oil casing. This gas lift method is also called positive lift.
When the oil contains wax and sand, if central air intake is used, annular air intake is often used in practical work, because the oil flow rate in the annular space is low, the sand is easy to settle, and the wax on the outer wall of the pipeline is difficult to remove.
3) Characteristics of gas lift oil recovery
Advantages of gas lift oil recovery: low one-time investment in downhole equipment and small maintenance workload; There are no friction parts underground, which are suitable for wells containing sand, wax and water; Not affected by corrosive substances and high temperature in mineral liquid; Easy to use in inclined wells, turning wells and offshore platforms; Easy centralized management and control. Disadvantages: gas lift oil production must have sufficient gas source; If continuous gas lift works under high pressure, the safety is poor; Gas lift is not suitable for high-yield wells, wax-deposited wells and heavy oil wells with damaged casing; Small oil fields and single wells have poor gas lift oil recovery effect.
Figure 5-8 Schematic Diagram of Electric Submersible Pump Well Device
2. Electric submersible centrifugal pump for oil production
Electric submersible centrifugal pump (esp or electric pump for short) belongs to rodless pumping equipment. It uses tubing to lower the centrifugal pump and submersible motor into the well, and the submersible motor drives the centrifugal pump to lift the oil to the ground. The electric pump has wide adjustment range of displacement and lift, strong adaptability, simple ground process flow, convenient management, easy automation and high economic benefit.
Electric pump equipment consists of three parts: ground, middle and underground, as shown in Figure 5-8.
The ground part is composed of transformer, junction box, control cabinet (switchboard), cable and wellhead device, which mainly plays the role of control, protection and recording.
The middle part is mainly cables, including power cables and lead cables. The power cable transmits the ground current to the underground lead cable; The lead cable is used to connect the power cable with the motor.
Generally, the downhole part consists of oil drain valve, one-way valve and downhole unit from top to bottom. Downhole devices include multistage centrifugal pump, oil-gas separator, protector and submersible motor. Some electric pump wells are also equipped with monitoring devices under the submersible motor, which can measure the bottom hole pressure, temperature, motor insulation and liquid level rise and fall, and transmit the signals to the ground console.
The submersible motor is installed at the lowest part of the underground unit and is the power of the electric pump. The high-voltage electricity on the ground is transmitted to the submersible motor through cables. The submersible motor converts electric energy into mechanical energy output, and drives the electric pump to work through the shaft. The protector is installed on the upper part of the submersible motor to balance the pressure in the motor, lubricate and seal the motor. Oil-gas separator is usually installed at the upper end of protector and the lower end of multistage centrifugal pump to separate free gas in crude oil and improve pump efficiency. The multistage centrifugal pump consists of a fixed part and a rotating part. The rotating part has a pump shaft on which a large number of impellers are installed. When the motor drives the impeller on the pump shaft to rotate at high speed, the liquid filled in the impeller is thrown around the impeller under the action of centrifugal force, which accelerates the well fluid and makes it have kinetic energy. The well fluid is introduced into the secondary impeller from the guide shell, so that a certain lift can be obtained after being superimposed step by step, and the well fluid is lifted to the ground.
The working process of the electric pump unit can be simply described as follows: the ground power supply is input to the underground submersible motor through the special cable of the electric submersible pump, and the submersible motor drives the multistage centrifugal pump to rotate, and the bottom crude oil is lifted and pumped to the ground through the centrifugal action of the multistage impellers of the centrifugal pump.
Practice shows that electric pumps have good effects on wells with strong water flooding, high production, wells with different depths, directional wells, sand wells and wax wells. Its displacement range is16 ~14365438+100 m3/d; The maximum pumping depth can reach 4600 meters, and the maximum underground working temperature can reach 230℃.
3. Downhole drive screw pump oil production
Different from the surface-driven screw pump, the downhole-driven screw pump provides power at the bottom of the well without sucker rod. Its working principle is that the pump, motor and protector are lowered into the well below the liquid level through the oil pipe, the motor drives the screw to rotate through the eccentric coupling, the screw is installed in the casing, and the cavity formed by the screw and the casing is isolated. When the screw rotates, these chambers gradually move from bottom to top, which makes the liquid pressure increase continuously, thus sending the well fluid to the surface.
As far as the current situation is concerned, the ground-driven screw pump technology is mature; Downhole drive screw pump has many advantages, but it is still in the experimental stage.
4. Hydraulic piston pump oil production
Hydraulic piston pump is a rodless pumping device with hydraulic transmission, which is the application of hydraulic transmission in pumping equipment. Compared with sucker rod pump, its fundamental feature is to change the energy transfer mode. The hydraulic piston pump consists of three parts: the ground, the middle and the underground, as shown in Figure 5-9.
Figure 5-9 Open Hydraulic Piston Pump Oil Production System
1- high pressure control manifold; 2- Ground power pump; 3 engine; 4— Power liquid treatment tank; 5— Wellhead device; 6— Downhole pump working barrel; 7- submersible pump
The ground part includes power liquid treatment tank, engine, ground power pump, high pressure control manifold, valve group and wellhead device, which is responsible for providing power.
The middle part is the central oil pipe of power fluid from the ground to the underground unit, which is a special channel for discharging waste power fluid and produced fluid to the ground.
The downhole part is composed of working cylinder and submerged pump, which mainly plays the role of pumping oil.
The working principle of hydraulic piston pump is: the motor drives the ground power pump, and the liquid in the liquid storage tank enters the central oil pipe after being pressurized by the power pump. After the high-pressure power liquid enters the underground hydraulic piston pump, it drives the pump to work, and the scrubbing liquid and the power liquid after doing work return to the ground through the outer tubing.
The displacement range of hydraulic piston pump is large (16 ~ 1600 m3/d), and it has strong adaptability to reservoir depth, wax content, heavy oil, deviated wells and horizontal wells. It can be used for oil well exploitation under various conditions and can work in wells with high temperature. However, the structure of the unit is complex, the machining accuracy is high, and the measurement of power fluid is difficult.
Fig. 5- 10 working principle diagram of jet pump
5. Jet pump oil production device
Jet pump is divided into ground part, middle part and underground part. The ground part and the middle part are the same as the hydraulic piston pump, except that the hydraulic jet pump can only be installed as an open power liquid circulation system. The downhole part is a jet pump, which consists of nozzle, throat and diffuser, as shown in Figure 5- 10.
The working principle of the jet pump: the power fluid is injected from the tubing, flows to the nozzle through the upper part of the jet pump, and enters the mixing chamber communicated with the formation fluid. At the nozzle, the total pressure head of almost all power liquids becomes the velocity pressure head. The crude oil entering the mixing chamber is scrubbed by the power liquid, mixed with the power liquid and flows into the throat, where momentum and kinetic energy are converted, and then the velocity head is converted into the pressure head through the diffusion tube with gradually expanding cross section, thus lifting the mixed liquid to the ground.
Characteristics of jet pump: downhole equipment has no power parts; The jet pump can be located in the same working cylinder as the hydraulic piston pump; Not limited by the lifting height; Suitable for high-yield liquid wells; High initial investment; Corrosion and wear will damage the nozzle; The maintenance cost of ground equipment is quite high.