Patent Application
20210363873
This invention generally pertains to technology for controlling electric and gas-powered rod pumping units that may be used on oil or gas wells. More specifically, the invention pertains to a controller that monitors pump power usage (e.g., current draw on electric powered drives and fuel or air consumption on gas-powered units) and possibly tubing pressure and/or polish rod temperature to indicate pump efficiency. The controller will start and stop the pump, possibly utilizing an algorithm that takes measurements from current usage/fuel usage/air usage and possibly tubing pressure and/or polish rod temperature. The pump-controller will also protect drive belts by turning the unit off if belt slippage is detected during the on cycle. The controller will also contain safety shut-down features for high/low tubing pressure, high/low amp-draw, and/or high/low fuel burn and high polish rod temperature.
Industry standard pump-controllers with the capability to detect a non-pumping situation, i.e. “pumped off,” use a variety of sensors such as load cells and encoders which tell a controller that the well is not pumping efficiently or is not pumping at all. These sensors can be expensive to purchase and expensive to install, requiring specialized technicians and equipment. This invention may perform the same function as the costly pump-controllers while utilizing inexpensive electric current, or fuel, air usage detection sensors that are built into or connected to the controller. Embodiments may include a pressure transducer (to send tubing pressure measurements to the controller) or a polish-rod temperature probe (to send polish-rod temperature to the controller). Within the controller, an algorithm uses the electric current/fuel burn/air flow and possibly tubing-pressure data or polish-rod-temperature data. The controller can make changes to pump operation timing parameters, which can, in turn, maintain peak pump efficiency. Operating the pump at peak efficiency will result in increased production and reduced energy use.
Pump-controllers (also called pump-off controllers) have been used in the oil and gas industry for many years. They use sensors to detect a “pumped-off condition.” This is a situation that occurs when the pump is not pumping liquid but is still running. This condition may be due to one or more of the following reasons: (1) the liquid entry into the wellbore is slower than the pump's ability to remove the liquid from the wellbore, (2) gas from the well interferes with the pump's ability to lift the liquid (e.g., the pump may be “gas locked,” a condition in which gas takes up room in the pump chamber leading to the gas compressing on not entering the tubing when the pump strokes, and gas expanding to prevent the pump chamber from filling when the pump strokes in the opposite direction), or (3) a mechanical failure (e.g., failure in surface equipment such as broken drive belts, broken or seized bearings on the pumping unit, bridle damage or and failure in down-hole equipment such as rod separations, pump failures, tubing leaks, and check valve (traveling valve) failures).
A pumping unit that is in operation but not actively pumping liquid may lead to any of a number of adverse consequences. For example, the energy used by the pump is wasted. This is a significant failing as energy consumption is one of the biggest costs in operating an oil and gas pumping unit. The pumping system may also be subject to premature wear and tear. Again, this is significant as the cost of the production tubing, rod string, downhole pump, and the pumping unit itself can be very expensive, even on shallow wells. When the pump is running while not pumping liquid, the entire system is wearing out at a great cost to the operator. The system may also be subject to additional damage to compromised well components. For example, a pumped-off condition could result in rod separation. If the rods separate and the well continues to pump, it could “slam” the top part of the rod string into the bottom section. This could potentially cause added rod string damage in addition to pump, pumping unit, and tubing damage.
Embodiments of the invention may provide a pump-control device. This device contains an inlet power monitor on electric-powered units and a fuel consumption sensor or air consumption sensor on gas-powered units.
In an electric-unit embodiment, the power inlet connection will feed power to a controller (i.e., a control circuit such as an application specific circuit, a PLC (programable logic controller), or a processor). Controller inputs may include a power-consumption sensor, a tubing-pressure sensor, a casing-pressure sensor, and a polish-rod-temperature sensor. The controller will have the ability to start and stop the pumping unit by turning electric motor power on and off. This can be achieved by running the motor supply power through a contact block.
In a gas-powered-unit embodiment, controller inputs may include a fuel-usage sensor, mass air-flow sensor, tubing-pressure sensor, casing-pressure sensor, and a polish-rod-temperature sensor. The controller will have the ability to start and stop the pumping unit by engaging/disengaging an electric clutch or sending a signal to an engine controller. The controller may be powered by the engine driving a voltage supply or using a solar panel and battery backup.
Both gas and electric embodiments of the rod-pump controller will use the same basic algorithm for controlling the pump. For example, the user will: (1) set a maximum off time not to be exceeded by the algorithm (with a factory-default setting of 3 hours), and (2) set a target off and on time (with a factory-default setting of 30 minutes off/10 minutes on for a period of 40 minutes and a duty cycle of 25%). When the pump turns on, it will run until a pump-off trigger or safety trigger is met. If a safety trigger is met, the unit will not try to restart until the user resets the system. (In an alternative embodiment, the unit may attempt to automatically restart after a period of time following a safety trigger shutdown.) When the pump-off trigger is met, the algorithm will compare the actual run time to the target run time. If the run time exceeded the target time, the off time will be reduced by 10% for the next cycle. If the actual run time does not reach the target run time, the off time will be increased by 10%, not exceeding the maximum off time set by the user. The percentage change this algorithm uses can be adjusted by the user to better control wells with differing pump-off characteristics.
Automatic Mode: Use an off-time algorithm to turn the pump on and off in an effort to maximize production and/or minimize energy consumption. All four overriding safety shutdowns may be used during this mode of operation.
Timer Mode: User will enter on and off times. The controller will turn the pump on and off in accordance with these times as long as the overriding shutdowns are allowing the pump to operate and the well has not pumped off (utilizing pump-off triggers). If the well pumps off during the “on” time, the controller will shut down and start the off cycle.
Manual Mode: Simple on/off; possibly a button or switch on the face plate that turns the unit on and off ignoring all overriding safety and pump off triggers.
Low-Pressure Trigger: A user definable trigger is met for “pump off” pressure or by using a Pressure Trigger Algorithm. One example can be when the pump is started, we allow a user definable delay for the pump to get liquid to surface before we start monitoring for a pumped-off condition. During the off cycle, gas will separate from the liquid in the tubing causing a gas bubble at the top of the liquid column. Other issues like leaking check/traveling valves in the pump mechanism will also cause a bubble that needs to be pumped out of the tubing before monitoring can begin. After the pump-up delay expires, we track the peak pressure of each pump stroke and log the highest stroke pressure to create a plateau. In some cases, it can take several minutes to achieve this plateau as the gas bubbles in the flowline system are partially compressing during the stroke. Once the pressure reaches its plateau, we monitor the difference in pressure from the plateau to the pressure from each stroke of the pump. If the stroke pressure falls below the user-definable trigger setpoint for a user-definable number of strokes, the program will advance to the post pump-off delay timer, then advance to the off cycle.
Current-Draw Trigger (electric-powered pumps): A user definable trigger is met when the current draw stops meeting the “high” set point or “low” set point (in the case the unit is weight heavy). A high amp (current) triggering example will be a unit that normally uses 24.4 amps when traveling in the up position that stops using 24.4 amps and only uses 23.5 amps for the time we allow (˜20 seconds), the trigger will shut the unit down on “pump off.” An example of low amp draw trigger for units that are “weight heavy” will be monitoring the low amp side of the pump curve. If a unit has a low amp reading of 9.48 amps during normal pumping operations and we start seeing 9.26 amps after a timer (˜20 seconds), the trigger for “pump off” will be made.
Fuel-Use Trigger (gas-powered pumps): Similar control parameters will be used for gas-powered units as electric-powered units; fuel usage will be used in place of current draw. Alternatively (or in addition), the system may use air intake for gas-powered units.
Current-Wave Trigger (electric units): On some wells we might not see a decrease in amp draw during the pump stroke (when pumped off) due to the relatively small change in power requirements. In this scenario, the amp draw “wave” (the current-vs-time profile) will be interrupted on the down stroke due to the pump piston impacting the liquid in a partially filled pump chamber. This interruption in the wave will trigger “pump off.” One way to see this interruption is by analyzing the current wave (or Amp wave) and triggering off of changes seen in that wave using amplitude and time. For example, one Current/Amp Trigger Algorithm can be when the pump is started, we allow for a pump-up delay to clear any gas pockets that could have formed above the liquid column in the tubing or in the flowline. We then start a learning cycle where we look at a user-definable amount of consecutive rising samples. At this point, we take a time stamp of the rising samples and an amplitude reading. We will then wait for the current/amp wave to drop below saved amplitude reading, this tells us the stroke is completed and we start looking for consecutive rising samples again to get a time/amplitude stamp on the next stroke. We take a user-definable number of samples to average together to generate our baseline. This baseline is compared to all future strokes of the pump. When we see a user definable % change in this time stamp, the program will advance to the post pump-off delay timer, then advance to the off cycle.
Another example of using the amp wave to trigger a pump-off condition is to measure the valley and peak of the wave with a time stamp to get a wave period (sometimes colloquially referred to as “wavelength” in a temporal domain). An algorithm will learn this wave period after an adequate pump-up delay, then use this baseline to compare all future periods during the cycle. When a user definable change is met between the baseline and the running period, the trigger is met, a post pump-off timer is met, and the unit starts the off cycle.
Fuel-Wave Trigger (gas units): Similar to the current-wave trigger, except based on a the fuel-usage or air-usage wave.
High-Line Pressure: User definable with no timer, shut down immediately when this set point is reached to keep from damaging the sales/flow line from high pressure.
Low-Line Pressure: On a timer, only active when the unit is pumping; this is set below the “pump off trigger” pressure. For example, if a normal flow line pressure is 45 psi while pumping and we trigger a pump off event at 35 psi, we will set the low line pressure to ˜15 psi. This should trigger if the flowline fails and we are pumping liquid on the ground. This feature will be on a delay timer to allow a brief change in pressure due to the directional change of the pump.
Belt Alarm (low amp draw/fuel/air usage): Active when “normal” high/low amp or fuel-usage or air-usage trigger is not met within a user definable time. For example, on an electric unit, if the normal up/down cycle shows a max current (amp) draw of 25 amps and minimum of 9 amps, the unit will trigger a belt slippage alarm if 80% (˜20 amps) of high amp draw is not met within the allowable time. Gas units will use fuel usage or air usage instead of amp draw to trigger the belt slippage alarm.
High-Polish-Rod Temperature: If the temperature exceeds the user definable set point, the unit will stop.
These and other features, aspects, and advantages of the present invention will become better understood with reference to the following description, appended claims, and accompanying drawings where:
In the summary above, and in the description below, reference is made to particular features of the invention in the context of exemplary embodiments of the invention. The features are described in the context of the exemplary embodiments to facilitate understanding. But the invention is not limited to the exemplary embodiments. And the features are not limited to the embodiments by which they are described. The invention provides a number of inventive features which can be combined in many ways, and the invention can be embodied in a wide variety of contexts. Unless expressly set forth as an essential feature of the invention, a feature of a particular embodiment should not be read into the claims unless expressly recited in a claim.
Except as explicitly defined otherwise, the words and phrases used herein, including terms used in the claims, carry the same meaning they carry to one of ordinary skill in the art as ordinarily used in the art.
Because one of ordinary skill in the art may best understand the structure of the invention by the function of various structural features of the invention, certain structural features may be explained or claimed with reference to the function of a feature. Unless used in the context of describing or claiming a particular inventive function (e.g., a process), reference to the function of a structural feature refers to the capability of the structural feature, not to an instance of use of the invention.
Except for claims that include language introducing a function with “means for” or “step for,” the claims are not recited in so-called means-plus-function or step-plus-function format governed by 35 U.S.C. § 112(f). Claims that include the “means for [function]” language but also recite the structure for performing the function are not means-plus-function claims governed by § 112(f). Claims that include the “step for [function]” language but also recite an act for performing the function are not step-plus-function claims governed by § 112(f).
Except as otherwise stated herein or as is otherwise clear from context, the inventive methods comprising or consisting of more than one step may be carried out without concern for the order of the steps.
The terms “comprising,” “comprises,” “including,” “includes,” “having,” “haves,” and their grammatical equivalents are used herein to mean that other components or steps are optionally present. For example, an article comprising A, B, and C includes an article having only A, B, and C as well as articles having A, B, C, and other components. And a method comprising the steps A, B, and C includes methods having only the steps A, B, and C as well as methods having the steps A, B, C, and other steps.
Terms of degree, such as “substantially,” “about,” and “roughly” are used herein to denote features that satisfy their technological purpose equivalently to a feature that is “exact.” For example, a component A is “substantially” perpendicular to a second component B if A and B are at an angle such as to equivalently satisfy the technological purpose of A being perpendicular to B.
Except as otherwise stated herein, or as is otherwise clear from context, the term “or” is used herein in its inclusive sense. For example, “A or B” means “A or B, or both A and B.”
While the foregoing description is directed to the preferred embodiments of the invention, other and further embodiments of the invention will be apparent to those skilled in the art and may be made without departing from the basic scope of the invention. Features described with reference to one embodiment may be combined with other embodiments, even if not explicitly stated above, without departing from the scope of the invention. The scope of the invention is defined by the claims which follow.
This application claims the benefit of U.S. Provisional Patent Application No. 63/029,687 filed on May 25, 2020.
| Number | Date | Country | |
|---|---|---|---|
| 63029687 | May 2020 | US |
