Patent Application
20250215771
The main subject matter of the present invention for which a patent is requested is a HYDRAULIC UNIT FOR MECHANICAL PUMPING (HUMP) FOR OIL LIFTING, which responds to a novel design that maximizes its production capacity, decreasing the manufacturing cost thereof.
HYDRAULIC UNIT FOR MECHANICAL PUMPING (HUMP), have long tried to replace API 11E equipment having lower productivity, but the resistance to change was very strong.
In API-11E PUMPING UNITS or HYDRAULIC UNIT FOR MECHANICAL PUMPING (HUMP), the power transmission to the API 11AX depth pump is done through the rod string. For equal rod string the transmitted force will be equal, but the power transfer is produced by two variables, force and speed. The HYDRAULIC UNIT FOR MECHANICAL PUMPING could transmit during the whole cycle the same force by varying the speed of the polished rod at will, on the other hand in the API 11E equipment the speed is regulated by the equation of the connecting rod-crank. For this reason, their productivity is lower.
Initially these units consisted of a cylinder, supported on a structure or on the wellhead, inside of which there was a piston (surface piston). This piston generates a chamber, which when pressurized by the hydraulic pump, produced the upward movement of the surface piston, the polished rod, the rod string and the piston of the API 11AX depth pump. The electric motor consumed electricity only in the upward movement of the piston and the reciprocating motion was produced by pressure change.
To reduce energy consumption during operation, counterbalancing systems were introduced. The most commonly adopted is the pressure accumulator charged with nitrogen, responsible for counterbalancing the weight of the rod string and part of the tubing fluid column. This introduction allowed a significant decrease in the energy consumed during the operation thereof.
To achieve this, it was necessary to duplicate the hydraulic circuits: a counterbalance circuit that, as explained above, kept balanced the weight of the elements moving inside the tubing (rod string, pumped fluid and API 11AX pump) and an actuator circuit that provided the necessary force to produce the reciprocating motion, overcoming inertia, friction, etc.
The assembly of these two systems or circuits was simple. The counterbalance piston was joined, in tandem to a polished rod, to the actuating piston, and the latter to the rod string by another polished rod. Both pistons were aligned and slid on independent cylinders.
As we said before, the cylinder and the counterbalance piston formed a chamber fed by the pressure of the pressure accumulator that neutralized the weight of the rod string in fluid and part of the weight of the fluid, while the actuating piston with the actuator cylinder formed two chambers. The upper chamber forced the actuating piston and everything suspended to move downward and the lower chamber that produced the ascent of everything suspended.
The actuating piston received flow and pressure from a hydraulic pump after passing through by-pass valves, responsible for feeding both chambers to generate the reciprocating motion.
During the ascending stage, the counterbalance piston and the actuator generated force in the same direction, while during the descending stage they generated opposite forces, which caused the polished rod to descend and the fluid in the counterbalance cylinder to return to the pressure accumulator, restoring the initial conditions.
Although from an energy saving point of view the system was very good, it had two disadvantages: the first one was the duplication of the pistons and surface cylinders, the second one was the duplication of the length of the equipment, which generated mobility problems in the field.
To avoid this duplication, additional piston and cylinder combinations of different effective area were used. The idea of this set of additional pistons and cylinders (CPYC), which were fed by the Nitrogen charged pressure accumulator (Ac), and by the hydraulic pump (B), was to achieve that instead of increasing the force on the polished rod by increasing the area of the main piston or by the sum of the areas of the accumulator piston and the actuator piston, it was achieved by increasing the pressure on the main piston.
The CPYC assembly has two heads (CabS) and (Cabl), two cylinders joined to the central body of the CPYC and two pistons that moved inside each of the cylinders joined by a polished rod (V) that moved inside the central body, which has retainers to prevent leaks. Four chambers were formed:
The (CabS), the Upper Cylinder (Cs) and Upper Piston (Ps) formed a Chamber (C1).
The (Cs), the lower face of the (Ps) joined by the rod (V) and the upper wall of the CPYC Central Body, formed the Chamber (C2).
The Lower Cylinder (Ci), the Lower Piston (Pi) joined by the rod (V) and the lower wall of the CPYC Central Body form the Chamber (C3).
The (Cabl), the (Ci) and the lower face of the (Pi) form the Chamber (C4).
The (C1) is fed by the pressure accumulator (Ac) and its function is to counterbalance the weight of the string and about 50% of the fluid in the tubing.
The (C4) pressurizes the fluid that drives the Main Piston (Pp). The pressures produced on (Pp) change depending on what happens in Chambers (C2) and (C3). When (C3) receives pressure from pump (B) and (C2) has backpressure, the (Pp) will receive a higher pressure than the pressure accumulator (Ac) and the (Pp) will rise.
When this is reversed, i.e. Pump (B) pressurizes (C2) and (C3) has backpressure, the (Pp) will receive lower pressure than the (Ac). This will cause the (Pp) to drop and the hydraulic fluid that was in Chamber (C1) will return to the Accumulator restoring the initial pressure in it.
This system increases or decreases the pressure on the Main Piston (Pp), generating the reciprocating motion, which will be transmitted to the polished rod, the rod string and the piston of the API 11AX depth pump.
Although we have avoided duplicating the length of the equipment to be installed in the field, this causes a significant increase in cost due to the addition of the assemblies included in the CPYC (two cylinders, two pistons, rod, two heads and the complexity of achieving the concentricity of these elements.
To avoid these higher costs, the new HYDRAULIC UNIT FOR MECHANICAL PUMPING (HUMP) of the present invention has been developed, which we consider simplifying and reliable, which in turn decreases the cost of manufacturing, maintenance, and production of this equipment:
To facilitate understanding of the equipment referred to in this invention, the description which follows uses the numerical references appearing in the representative figures of the invention.
The proposed equipment consists of a Cylinder (34) and Piston (32), a Pressure Accumulator (13), and auxiliary Nitrogen tubes (14), which will be responsible for the upward movement of the Piston (32).
The Hydraulic Unit including Hydraulic Fluid Reservoir (1), Heat Exchanger (5), Electric or Thermal Motor (7) to drive a Hydraulic Pump (6), responsible for the downward movement of the Piston (32), Bypass and Position Valves, Temperature and Pressure Detectors. All this coordinated by a Program incorporated to a PLC.
The force that will generate the upward movement of the Piston (32), the polished rod (33), the rod string, the API 11AX Piston and the oil in the tubing, will be produced by the pressure of the hydraulic fluid from the pressure accumulator (13), on the lower face of the main Piston (32i).
This pressure will have a maximum value, limited by the resistance of the rod string and a working pressure related to the speed in GPM (strokes per minute) that we want to give to the equipment. The speed of the upward movement can become high and must be tempered in the final stretch of the upward stroke by a restriction of the outlet flow of the Chamber (31) that will originate an increase of pressure in it.
The downward movement of the Piston (32), of the rod string and moving parts including the API 11AX Piston, will be produced by the effect of the pressure and flow of the hydraulic pump fluid (6) on the upper face of the Piston (32s). Its descent speed will be regulated by controlling the minimum force to which the polished rod (33) must be subjected to avoid “curling” (bending or “backling”) in the rod string.
The cost of energy spent per cycle arises from the energy consumed to lower the piston (32) for half a cycle, since during this stroke the fluid from the chamber (35) will enter the pressure accumulator (13) again, thus restoring the initial pressure thereof.
The maximum speed that the equipment of this invention will be able to develop will be limited in the ascending stage by the diameters of the hydraulic fluid supply and return pipes (by friction in the pipe) and by the resistance offered by the rod string and the oil to its ascending movement (by friction and inertia).
The maximum speed in the descending stage will be limited by the “curls” that can be produced in the string, directly related to the minimum force to which the polished rod (33) must be subjected and that can be controlled by pressure difference and areas on both faces of the piston (32) during the descending stage.
We believe we have succeeded in simplifying the equipment to the maximum and maximizing the expected performance for this equipment with standard elements.
This invention defines a new combination of means conceived to achieve a superior result, being unpredictable and surprising even for one skilled in the art. Consequently, in addition to being new, its constructive and functional conception shows a clear inventive activity, so that it meets the conditions required by the Law to be considered a patent of invention.
Generally, the pressure accumulator (13) has been used in this equipment as the one responsible for balancing the weight of the pumping rods and 50% of the weight of the fluid being lifted.
According to the present invention, to affect the upward movement of the piston (32), the pressure and flow of the pressure accumulator (13) will be used, with the advantage of being able to limit the generated force, limiting the maximum pressure to which the pressure accumulator (13) will be regulated, so that the resistance of the rod string, according to Goodman's diagram, is never exceeded.
On the other hand, the flow produced by the pressure accumulator is variable, much higher than that of any pump and of controllable pressure, which means that in the elongation stage, which in long strokes of deep wells can be very significant, we can reduce the cycle time, improving the performance of the equipment.
The energy cost spent during the cycle will be the energy spent by the hydraulic pump (6) to lower the main piston (32) during the descent stage, since during this stroke the fluid from the chamber (35) will enter the accumulator (13) again, restoring its initial pressure.
As can be seen, the decrease in cost per equipment is remarkable, also the hydraulic losses due to seals will be low since there are only two places where they can occur: (Cylinder and piston), (polished rod and seal bushings).
In order to give concrete expression to the advantages of the hydraulic pumping equipment of the invention, to which users and ones skilled in the art may add many others, and to facilitate the understanding of the constructive, constitutive and functional features of the same, a preferred embodiment example is described below, which is illustrated schematically and without a specific scale; it is expressly clarified that precisely because it is an example, it is not to be considered as limiting, exclusive or conditioning the scope of protection of the present invention, but merely has a merely explanatory or illustrative purpose of the basic conception on which the invention is based.
The Pressure Accumulator Subassembly (PAS) is represented. It is composed of a pressure accumulator, responsible for the upward movement of the piston, whose maximum pressure will be controlled to avoid exceeding the resistance of the rod string and its working pressure, in order to achieve the strokes per minute for which the equipment was designed.
The Pressure Generator Subassembly (PGS) is represented. It consists of a hydraulic oil tank, a hydraulic pump, and valves that, acting according to the PLC program, achieve the reciprocating motion.
The Cylinder, Piston, and Polished Piston Rod Subassembly (CPPS) is represented. It is composed of the parts mentioned in the subassembly, responsible for generating the reciprocating motion to produce oil.
The PLC Subassembly is represented, whose program receives signals from thermometers, pressure gauges and position sensors and issues orders to valves and contactors, according to its programming.
Looking at
The Pressure Generator Subassembly, Pressure Accumulator Subassembly, the Cylinder, Piston and Polished Rod Subassembly and PLC Subassembly.
The referred Pressure Generator Subassembly (PGS), is composed of elements described above, but which will be described again to better understand the function thereof: An Oil Tank with filling mouth and air filter (1), Heat Exchanger (5), a Hydraulic Pump (6) driven by an Electric or Internal Combustion Engine (7) that will send hydraulic liquid through the Directional Valve (25) to the Chamber (31) passing through the Shut-off Valve (26) and the Pressure Gauge with dial and digital output for PLC command (28).
This hydraulic fluid besides producing the descent of the Piston (32) sends the fluid from the Chamber (35) back to the Pressure accumulator (13), passing through the Manometer with dial and digital output for PLC command (29) and through the Shut-off Valve (27).
The references thereof are:
As for the Pressure Accumulator Subassembly (PAS), is composed of the Hydraulic Accumulator filled with Nitrogen (13) and Nitrogen Bottles, 75-liter, for working with high pressures, used to back up Cylinders, (14) pressure gauges, thermometers and valves. With the references thereof:
As for the Cylinder, Piston and Polished Rod Subassembly (CPPS), it is composed of the parts mentioned in the subassembly, which form the Upper Chamber (31) and the Lower Chamber (35) responsible for generating the reciprocating motion of the Piston (32), which through the Polished Rod (33), transmits to the Rod String and Piston of the API 11AX pump. The references are:
The above-mentioned PLC subassembly has a program to receive the input signals and issue commands to valves or contactors. Before starting the equipment, we must load reference pressures and force in the program. The maximum pressure that in case of exceeding could produce the breakage of the rod string, the working pressure whose value defines the number of strokes per minute (SPM) the opening pressure in ascent and the opening pressure in descent to improve the performance of the cycle and the minimum force in the polished rod (33) during the descent, to avoid the “curls” in the rod string. The references are:
Signals entering the PLC for: level, temperature, and pressure.
Input signals to PLC position
Input signals to the PLC for pressure change
Piston rising stage (32) (
The PAS subassembly is ready for operation. Its pressure accumulator (13) has been pressurized with Nitrogen. The maximum pressure tolerated by the rod string has been entered into the PLC program (12), as well as the working pressure that will provide the number of strokes per minute (SPM) demanded by the wellbore production. The upward opening pressure and the downward opening pressure have also been entered to improve the cycle performance and the minimum downward force on the rod (33) to avoid “curls”. At the set time, the programmed sequence that will make the production cycles possible will start.
The PLC Subassembly Program will verify the pressure of the hydraulic fluid in the Pressure Gauge (10), if that pressure is not within the tolerance foreseen for the working pressure, it will issue the orders of: Direction of the Valve (8) so that the fluid goes towards the Valve (9), closing of the Valve (27) and starting of the Motor (7) and hydraulic pump (6), to fill the Pressure Accumulator (13), with the specified amount of fluid. The process stops when the Pressure Gauge (10) reaches the Working Pressure and sends the signal to the PLC Program. At that moment the upward cycle starts, the PLC cuts the energy of (7), or directs the Valve (8) so that the flow of the Hydraulic Pump (6) goes to the Reservoir (1), directs the Valve (25) towards the Reservoir (1), opens the Valve (26) and finally opens the Valve (27).
The pressurized fluid from the pressure accumulator (13) will enter through the inlet/outlet port (02) into the chamber (35), with sufficient and approximately constant pressure to raise the piston (32) at the required speed, displacing from the chamber (31) the fluid that will pass through the inlet/outlet port (O1), the pressure gauge (28), the valve (26) and the directional valve (25) to enter the reservoir (1).
The process continues until the Piston (32) makes contact with the Proximity Detector (23) and the Program will generate the following orders: Close Valves (26) and (27). The PLC program will be attentive to the pressure detected by the pressure gauge (29). The effort that the polished rod (33) was making during the upward stroke at almost constant speed included the weight of the oil, the weight of the SRs in fluid and the friction force of the oil and the rod string which was proportional to the speed. At this point, the Piston Speed (32) is equal to zero. As the API 11AX pump piston speed approaches zero, the stress on the polished rod (33) decreases, therefore the rod string stretch will decrease, and the pressure in the chamber (35) will be detected by the pressure gauge (29). When it reaches the Rising Opening Pressure value, it will send signals to the PLC Program which will command the opening of Valves (27) and (26). The Piston (32) will continue to rise and when the Proximity Detector (24) sends the signal to the PLC program, the descent will begin.
We can say that the speed of ascent that this equipment can develop will be comparatively high because the pressure accumulators (13) can deliver high flow rates with little pressure variation.
When the Proximity Detector (24) sends the signal to the PLC, the PLC will send the commands, which will be carried out simultaneously to start the descent stage: given Direction for the Valve (8) for the flow to go to Valve (25) and Valve Direction (25) for the flow to go to Valve (26), which is open. Valve (27) should also be open. The hydraulic Pump (6) will operate, and the fluid produced by the Pump (6) will pass through Valve (25), Valve (26) and enter the Chamber (31) through the Inlet/Outlet Port (01), lowering the Piston (32), dislodging the hydraulic fluid from the Chamber (35) and sending it through the Valve (27) to the Pressure Accumulator (13). As the Piston (32) passes through the Proximity Detector (22) it will send a signal to the PLC Program which will command the Valves (26) and (27) to close. This will cause the force on the polished rod (33) to increase, because the weight of the rod string during the descent was decreased by the friction effort (proportional to the descent speed). As the lowering speed in the piston (32) becomes zero and the speed in the API-11AX piston decreases, the weight of the rod string will increase; this will generate a greater stretching and as a consequence of the increase of force on the polished rod (33) and the piston (32) an increase of pressure in the chamber (35) that will be detected by the pressure gauge (29) that, when reaching the opening pressure in descent, will send a signal to the PLC program that will order to open the valves (26) and (27). The Piston (32) will continue to descend until it is detected by the Proximity Detector (21). At that point, obeying the PLC program, the flow of the Pump (6) is diverted by means of the directional Valve (8) to the return pipe having as final destination the Tank (1), while simultaneously the Valves (26) and (27) are opened. The upward stroke has started again.
As for the descending speed, we can say that although it is limited as it is in other mechanical pumping equipment, its design allows us to control the descending speed by the minimum force to which the polished rod (33) must be subjected, to avoid the “curls” of the rod string. This minimum force control is carried out throughout the whole descending stage, by means of the PLC program with the information sent by the pressure gauges (28) and (29). The program will receive the pressure on both sides of the piston (32), will multiply it by the respective areas and will send the orders of partial openings or closings to the damped closing valves (26) and (27) during the descent.
Both in the first (ascending stage) and in the second (descending stage), by means of the proximity detectors (22) and (23) in collaboration with the pressure gauge (29), we manage to take maximum advantage of the available stroke in the surface cylinder (34) and piston (32), decreasing the stretching of the rod string in the ascending stroke and the contraction of the rod string in the descending stroke, making the stroke of the API-11AX Piston closer to that of the surface Piston.
During the ascending stroke, initial pressure is restored in the pressure accumulator (13), then the energy expense in the cycle will be the operation cost of the pump (6) during half-cycle.
Generally, the pressure accumulator (13) has been used in this equipment as the one responsible for balancing the weight of the pumping rods and 50% of the weight of the fluid being lifted. With the Hydraulic Unit of the invention, we are using it to effect the upward movement of the main Piston (32), with the advantage that we can limit the force generated in it, limiting the maximum pressure to which the Pressure Accumulator (13) will be regulated, so that the resistance of the rod string is never exceeded, according to Goodman's diagram. On the other hand, the flow produced by the pressure accumulator (13) is variable, much higher than that of any pump and of controllable pressure, which means that, in the elongation stage, which in long strokes, in deep wells, can be very significant, we reduce the cycle time, improving the performance of the equipment.
Finally, the descent speed control by minimum force to which the polished rod (33) must be subjected, to avoid the “curls” of the rod string, gives us greater sensitivity to improve the descent speed and avoid damage to the rod string.
| Number | Date | Country | Kind |
|---|---|---|---|
| P20230103553 | Dec 2023 | AR | national |
