LINEAR FRAC PUMP ASSEMBLY

Abstract

A linear frac pump includes a fluid end having an inlet valve disposed proximate to an inlet port, and a discharge valve disposed proximate to a discharge port. The pump further includes a first plunger rod housed within a first plunger housing, the first plunger rod having first and second ends, the first end being in fluid communication with the fluid end, and the second end being coupled to a first actuator. The pump includes a second plunger rod housed within a plunger housing, the second plunger rod having first and second ends, the first end being in fluid communication with the fluid end, and the second end being coupled to a second actuator. The first and second plunger rods and housings are coupled to the fluid end and the first and second plunger rods operate in sync to drive fluids inward from the inlet port and outward via the discharge port being regulated by the inlet and discharge valves.

Description

FIELD

The present disclosure relates to positive displacement pumps, and in particular, to a linear frac pump assembly with a folded configuration.

BACKGROUND

Large powerful pumps are commonly used for mining and oilfield applications, such as, for example, hydraulic fracturing. During hydraulic fracturing, fracturing fluid (i.e., cement, mud, frac sand and other material) is pumped at high pressures into a wellbore to cause the producing formation to fracture. One commonly used pump in hydraulic fracturing is a high-pressure reciprocating pump, like the SPM® Destiny™ TWS 2500 frac pump or the SPM® QEM 3000 Continuous Duty Frac Pump, manufactured by S.P.M. Oil & Gas, a Caterpillar Company located in Fort Worth, Tex. In operation, the fracturing fluid is caused to flow into and out of a pump fluid chamber as a consequence of the reciprocation of a piston-like plunger respectively moving away from and toward the fluid chamber. As the plunger moves away from the fluid chamber, the pressure inside the chamber decreases, creating a differential pressure across an inlet valve, drawing the fracturing fluid through the inlet valve into the chamber. When the plunger changes direction and begins to move towards the fluid chamber, the pressure inside the chamber substantially increases closing the inlet valve increasing the differential pressure across an outlet valve and causes the outlet valve to open, enabling the highly pressurized fracturing fluid to discharge through the outlet valve into the wellbore.

A typical frac unit is powered with a diesel engine driving a frac pump through a multispeed transmission. The rotational energy transferred to the reciprocating frac pump is channeled to horizontal plunger bores for pumping via crankshafts and connector rods. The operating conditions are often extreme involving high fluid flow and high operating pressures (oftentimes up to 15,000 psi). Pressure fluctuations as seen in diesel powered units or other internal combustion-based units often cause undesirable cyclic stresses on components, shortening their lives.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view of an embodiment of a linear pump according to the teachings of the present disclosure;

FIG. 2 is a cross-sectional view of an embodiment of a linear pump according to the teachings of the present disclosure;

FIG. 3 is a schematic cross-sectional view of an embodiment of the linear pump according to the teachings of the present disclosure; and

FIG. 4 is a schematic cross-sectional view of an embodiment of a linear pump having a folded configuration according to the teachings of the present disclosure.

DETAILED DESCRIPTION

The introduction of natural gas as “free fuel” for frac operations has led to investigation of the best way to utilize natural gas to generate pumping power. One option is to use a large gas turbine generator that creates electrical power to run the frac job on electricity. Since electric drive is not limited to the maximum diesel engine power feasible for a mobile frac unit, a larger pump is possible. The ability to deploy larger pumps would lead to fewer units required on a frac site. Fewer units on location translates to a lower total cost of ownership and operating cost.

Reciprocating pumps have many moving parts and so do the power systems that drive them. Replacing reciprocating pumps and their associated drive systems with a linear pump that is actuated electrically through a planetary thread drive provides many advantages. The linear pumping action is created by the movement of the screw through the electrically-powered planetary drive.

In a first embodiment of a linear pump (described in a co-pending PCT Application No. WO2017/139583), a linearly actuated double-action pump includes a centrally-disposed drive system coupled to two fluid ends at either end along the linear axis, where the drive system drives the plunger rod to move the fluid in both fluid ends. In an example embodiment, an electric linear pump may use a planetary screw drive (e.g., planetary gears surrounding a threaded rod to convert rotational motion of the planetary gears to the linear translation movement of the threaded rod) to linearly move (i.e., translate) plunger rods instead of the traditional diesel engines. The threaded rod coupled to the drive system has plunger sections on both ends such that when the plunger rod moves in either direction, one of the two ends will be pumping out fluids while the other drawing in fluids. In other embodiments, the electric actuator may be in the form of a winding that uses electric current to create a magnetic field to move the rod along its axis (e.g., similar to solenoid actuation). A fluid end is coupled with each of the two plunger ends to control fluid charging on the suction stroke and pressure discharge on the power stroke. The electricity supplied to the planetary thread drive may be provided from the grid or produced by an onsite generator using local natural gas, thus minimizing fuel costs.

In a second embodiment of the linear actuated pump 10 shown in FIGS. 1-3, a centrally-disposed fluid end 12 is coupled to two actuators 14 and 15 on its two sides along a linear axis. The actuators 14 and 15 may be hydraulic or electro-mechanic actuators that are in fluid communication with a hydraulic/electrical-controlled drive system (not shown) that may incorporate a planetary screw drive or a solenoid drive system. The actuators 14 and 15 each drives or causes linear displacement of respective plungers 16 and 17 that reciprocate within their respective fluid bores defined within respective plunger housings 18 and 19. In this configuration, the stroke length of each plunger rod 16 and 17 can be halved and a smaller screw drive system may be employed and still achieve the same horsepower and fluid rate output when compared to the above-referenced double-action pump configuration. In this more compact second configuration, the overall length of the pump assembly 10 is reduced by the size of one fluid end. Further, because of the shorter stroke length, it is easier to achieve and maintain accurate alignment of the fluid end and hydraulic drive components. Within the fluid end 12 are an inlet and discharge valves 22 and 23 that regulate the intake and discharge of fluids from the pump through inlet and discharge ports (not explicitly shown). The inlet port is connected to a manifold (not shown) that supplies the frac fluid and the discharge port is connected to a discharge line (not shown) that leads to a wellbore. According to an embodiment, multiple linear pumps can be fluidly coupled at the discharge lines to deliver a constant high-pressure flow to the wellhead.

In a third embodiment as shown in FIG. 4, the “legs” of a linear pump assembly 40, including the respective actuators 44 and 45, plunger pistons 46 and 47, and piston housings 48 and 49, are “folded” at the centrally-disposed fluid end 42 so that the “legs” become disposed proximate to and alongside each other. Same as before, the actuators 44 and 45 may be hydraulic or electro-mechanic actuators that are in fluid communication with a hydraulic/electrical-controlled drive system that incorporates a planetary screw drive or a solenoid drive system. In this “folded” configuration, the overall length of the linear pump assembly 40 is greatly reduced to about half of the embodiment shown in FIG. 3. The great reduction in overall length enables more flexibility with respect to the arrangement of multiple pump assemblies within a limited footprint, such as on a trailer bed that is typically 48 feet in length and up to 8 feet in width.

The linear pump assemblies described herein may operate under or with a control module (not explicitly shown) that include a computer with associated software installed therein, to cooperatively operate the drive system and hydraulic/electrical-mechanical actuators so that the fluid output from the fluid end is smooth with minimized fluid pulsation. A number of sensors may be used to measure and monitor a variety of pump operating characteristics that are provided as input to the control module. The monitored pump characteristics may include, for example, fluid pressures, fluid flow rate, motor speed, etc.

In some embodiments, multiple pump assemblies, such as from two to six units, may be used for redundancy and configured to maintain a constant or steady output flow (i.e., smooth output). In different implementations, different plunger sizes and fluid end sizes (e.g., different product families) may be provided for a range of pressures needed for different applications.

In some examples, the motor used in the linear electric pump may be a permanent magnet synchronous motor. The bearing may be a spherical axial thrust bearing. The planetary gears may be directly driving a threaded plunger rod without additional transmission assemblies. In some cases, the electric linear pump may have one or more sensors to measure the rotary position of the plunger rod or the planetary gears to determine position, speed, or other information of the plunger rod. The motor, gears or planetary gears, bearings, and the threaded rods may be enclosed within a housing for lubrication and cooling purposes. Cooling system is provided for both the electric motor and the driven gears thereof. A logic control unit (LCU) may be used to accurately control the rotation of the motors and provide control according to control signals per control algorithm or programs. Detailed examples are provided below. One benefit of the electric motor-driven linear pumps described herein is much reduced noise generation than traditional operations using diesel engines and power ends.

The features of the present invention which are believed to be novel are set forth below with particularity in the appended claims. However, modifications, variations, and changes to the linear pump configurations described above will be apparent to those skilled in the art, and the linear actuated pump configuration described herein thus encompasses such modifications, variations, and changes and are not limited to the specific embodiments described herein.

Claims

1. A linear frac pump assembly comprising: a fluid end;a first plunger rod having first and second ends, the first end being in fluid communication with the fluid end, and the second end being coupled to a first actuator, the first plunger rod being housed within a first plunger housing defining a first plunger bore, the first plunger rod being configured for linear reciprocation within the first plunger bore driven by the first actuator;a second plunger rod having first and second ends, the first end thereof being in fluid communication with the fluid end, and the second end being coupled to a second actuator, the second plunger rod being housed within a second plunger housing defining a second plunger bore, the second plunger rod being configured for linear reciprocation within the second plunger bore driven by the second actuator; andthe first and second plunger bores being in in fluid communication with the fluid end and further being linear alignment with one another.

2. The linear frac pump assembly of claim 1, wherein at least one of the first and second actuator comprises an electric motor.

3. The linear frac pump assembly of claim 1, wherein at least one of the first and second actuator comprises an electric motor configured to engage the respect at least one of the first and second plunger rod.

4. The linear frac pump assembly of claim 3, wherein one or more gears of the electric motor are driven by a planetary gear transmission receiving rotation input from an electrically powered rotor.

5. The linear frac pump assembly of claim 1, wherein the fluid end comprises an inlet valve disposed proximate to an inlet port, and a discharge valve disposed proximate to a discharge port.

6. The linear frac pump assembly of claim 1, wherein the first and second actuators are selected from the group consisting of hydraulic and electro-mechanical actuators.

7. A linear pump assembly comprising: a fluid end;a first plunger rod housed within a first plunger housing coupled to the fluid end, the first plunger rod having first and second ends, the first end being in fluid communication with the fluid end, and the second end being coupled to a first actuator; anda second plunger rod housed within a plunger housing coupled to the fluid end, the second plunger rod having first and second ends, the first end being in fluid communication with the fluid end, and the second end being coupled to a second actuator, the first and second plunger rods and housing in parallel alignment and alongside one another and are traveling in the same direction and in sync.

8. The linear frac pump assembly of claim 7, wherein the first and second actuators are selected from the group consisting of hydraulic and electro-mechanical actuators.

9. The linear pump assembly of claim 7, wherein at least one of the first and second actuator comprises an electric motor.

10. The linear pump assembly of claim 7, wherein at least one of the first and second actuator comprises an electric motor configured to engage the respect at least one of the first and second plunger rod.

11. The linear pump assembly of claim 9, wherein one or more gears of the electric motor are driven by a planetary gear transmission receiving rotation input from an electrically powered rotor.

12. The linear frac pump assembly of claim 7, wherein the fluid end comprises an inlet valve disposed proximate to an inlet port, and a discharge valve disposed proximate to a discharge port.

13. A linear pump assembly comprising: a fluid end having an inlet valve disposed proximate to an inlet port, and a discharge valve disposed proximate to a discharge port;a first plunger rod housed within a first plunger housing, the first plunger rod having first and second ends, the first end being in fluid communication with the fluid end, and the second end being coupled to a first actuator; anda second plunger rod housed within a plunger housing, the second plunger rod having first and second ends, the first end being in fluid communication with the fluid end, and the second end being coupled to a second actuator, the first and second plunger rods and housings being coupled to the fluid end and the first and second plunger rods operate in sync to drive fluids inward from the inlet port and outward via the discharge port being regulated by the inlet and discharge valves.

14. The linear pump assembly of claim 13, wherein the first and second plunger housings are in linear alignment.

15. The linear pump assembly of claim 13, wherein the first and second plunger housings are parallel and disposed alongside one another.

16. The linear pump assembly of claim 13, wherein at least one of the first and second actuator comprises an electric motor.

17. The linear pump assembly of claim 13, wherein at least one of the first and second actuator comprises an electric motor configured to engage the respect at least one of the first and second plunger rod.

18. The linear pump assembly of claim 17, wherein one or more gears of the electric motor are driven by a planetary gear transmission receiving rotation input from an electrically powered rotor.

19. The linear pump assembly of claim 13, wherein at least one of the first and second actuator comprises an electric motor.