Interior of D-Jax controller showing LED display and Keypad for entering timing changes. (Inset) Controller module at well site

iBeam Controller Provides High Tech at Low Cost

iBeam components

iBeam's beam-mounted, self-contained, solar-powered sensor and communication unit 

Affordable Optimization Options for Low Productivity Wells
by Karl Lang
Excerpts in PTTC Network News, 3rd Quarter 2003

Systems for optimizing production from artificially lifted wells span the spectrum of sophistication, from multiple-sensor, real-time, internet-accessible, remote monitoring and control systems to a simple timer on a rod pump motor. Some would argue that the latter does not really constitute true production optimization technology, and many smaller producers might reply: "Maybe not, but it is affordable." The fact is, many small producers cannot afford the capital investment required to take advantage of the benefits that well monitoring and control can provide, an investment that can total thousands of dollars per well once the costs of computer hardware and software, data transmission system installation, power supply enhancements and training are included. While the per well costs drop somewhat as larger numbers of wells are added to a system, the overall economics still can be problematic for stripper wells producing only a few barrels of oil per day.

On the other hand, the benefits of even the simplest applications of well monitoring and and control systems are well established. For example, pump off controllers (POCs), also called rod pump controllers (RPCs), are a proven technology that has been operating in fields worldwide for over three decades. Most POCs are remote terminal units (RTUs) that monitor conditions, usually by continuously measuring the load on the pumping unit, and initiate a pump shut down based on a pre-set condition set by the operator. By detecting the "pumped off" condition of the well and shutting down the pump, the controller allows time for fluid to enter the wellbore before starting the pump once more. 

Over-pumping a well or allowing it to be pumped after the fluid level has been lowered below the downhole pump, results in "fluid pound," a condition where the traveling portion of the pump strikes fluid in the pump barrel. This action exerts excess stress on the pump, the rods, the tubing and the pumping unit, contributing to an increased risk of failure. Of course, the cost of the electricity running the pump on an over-pumped well is a wasted investment.

So, by reducing the amount of time a pump is run ineffectively, POCs reduce power consumption. Also, by reducing the number of instances when a well continues to be pumped without a fluid level, POCs reduce the number of well remediations due to pump failures, parted rods or tubing leaks. This in turn reduces down time, maintenance costs and well workover costs. Reported cost savings range from 10% to 20% for electrical power and 25% to 40% for rod, pump and tubing repairs. Production increases from 1% to 7% have also been reported as downtime is reduced and pump efficiency improved.

Recognizing a market for low-cost alternatives that can translate some of these benefits for low-productivity wells, several companies are offering controllers that offer a degree of technology at an affordable price. Two of these are described here.

Penny Pinching Pump-Offs

Several options exist for producers caught between a need to improve rod-pumped well production efficiency and an inability to finance the large capital investment required for the more sophisticated monitoring and control systems. One of these is the "Penny Pincher" pump-off control from D-JAX Corporation of Midland, TX. This POC operates on a very simple principle: the speed of the pump plunger will increase slightly if the barrel is empty rather than full, and small differences in measured pump-strokes-per-minute can indicate when the well is pumped off downhole. According to Allen Lindsey, General Manager of D-JAX, "The sensor wand mounted on the gearbox pedestal reacts to a magnetic strip on the counterweight and sends a signal to a microprocessor that determines the speed of the rods and compares it to the speed measured at the beginning of a cycle, when the pump is full. When the difference indicates a pumped off condition, the controller shuts down the pump." This is the only sensor and the only measurement utilized by the POC. "Its simplicity makes it reliable, easy to install, easy to calibrate and easy for pumpers to operate," adds Lindsey. A very simple and easily understandable key pad allows each controller to be adjusted or re-calibrated.

Interior of D-Jax controller showing LED display and keypad
for entering timing changes. (Inset) Controller module at well site

The advantage this product offers over a simple timer is of course the fact that an actual measurement of the well’s condition is used to control the pump. When a well is run on a timer, adjusting the cycle time (usually in increments of 15 minutes) is a matter of trial and error. With low-productivity wells the operator typically adjusts the run time and then monitors well production. By iteratively decreasing or increasing the run time, the operator can eventually determine the maximum production corresponding to the minimum run time. If, however, the well is producing in a waterflood with varying injection rates, the well's pumped-off fluid level may not remain static over time and an optimal cycle run time may never be realized, even with this time-consuming trial and error method.
According to Lindsey, the D-JAX pump off controller reacts to the difference in pump speed rather than an absolute measurement of well condition, and this is an advantage if well conditions change. Says Lindsey, "Paraffin, gas content, and other variables do not affect the controller's ability to identify a pumped-off condition."

For example, a pumping unit running at ten strokes per minute with the pump barrel filled completely on each stroke, would have a single stroke speed of 6000 milliseconds per stroke (msps). As the downhole fluid level drops off and the pump barrel no longer fills completely, the stroke speed increases, dropping the msps value until it reaches a minimum when the well is pumped off, say for example 5982 msps, a "delta" of 18 ms. While this increase in speed is imperceptible to the eye, the sensor installed between the gearbox and crank arm can detect and quantify the difference, and thereby determine when the well has pumped off.

The second parameter used by the Penny Pincher is the period between pumping cycles that is required for the fluid level to return to its maximum: the downtime. This parameter is generally set through trial and error, with the help of a dynamometer to determine exactly when the pump is once again filling completely. Of course it is important to accurately determine both the downtime and the delta parameters to optimize the well's pumping performance.

The controller also features an option whereby the operator can program the unit to run for only a portion of the pumping time during a certain number of pumping cycles. For example, setting the controller for five cycles at 95% will force the pump to run for 95% of the established pumping time for five cycles, after which, on the sixth cycle, the unit would run until the delta indicated the well was pumped off. This feature is designed to ensure that fluid pound strokes are eliminated, for example, when fiberglass rods are at risk.

The Penny Pincher has been around for 12 years, but D-Jax recently introduced new internal electrical surge protection for the controller. The standard system of thermistors, resistors and varistors proved effective in mitigating damage from nearby lightening strikes but could not prevent catastrophic failures in cases of direct strikes. While rare, these events were costly for the operator.

A solution was found in isolating the POC logic board from the power supply board using fiber optic couplings. The simple fiber optic circuit D-Jax uses between the power supply and the logic board consists of an emitter (transmitter), which converts normal electrical signals to light and sends them through the optical fiber, and a receiver that converts the light signal back to an electrical signal. The isolation begins with the 110 volt power supply which feeds the logic board 12 VAC, reducing the potential for flashover and collateral damage. Another potential source of surges is the sensor circuit coming from the gearbox pedestal. The sensor circuit is conventional copper wire to the power supply and fiber optic from the power supply to the logic board. Any surges brought in by the sensor circuit will stop at the power supply. While this configuration cannot completely eliminate all damage from lightning strikes or other powerful electrical surges, it does minimize the economic impact of damage when such events occur. By isolating the logic board from the power supply board, catastrophic damage will occur only to the power supply, which is about one-fourth as costly to replace as the logic board. The system has proven effective thus far. D-Jax has installed approximately 550 fiber optic-based controls, many in areas where lightning has been a problem, and has yet to see a failure attributable to lightning or other electrical events.

The Penny Pincher gets its name from its price: $1,495 plus a $250 installation fee. Lindsey reports that over 9,000 of these POCs have been installed domestically and worldwide. Overseas applications include Columbia, Argentina, Kazakhstan, Africa, and recently, Poland. While most of the wells employing these POCs are stripper wells, Lindsey adds that some wells producing as much as 200-300 BOPD have them installed. Operators using the bigger bore pumps find the Penny Pincher helpful in preventing fiberglass rod parts.

Following up this low-cost POC option, D-JAX has also recently introduced a wireless dynamometer system priced at $5,995, about half the cost of conventional systems. This product includes a load sensing and data transmission unit that clamps to the polished rod and a data receiver that sits on a truck dashboard and connects to a laptop computer. The system operates up to a distance of 300 feet. D-JAX is currently working with a software developer to provide analytical software.

iBeam Controller Provides High Tech at Low Cost

Another option for operators looking to achieve a level of optimization in their rod-pumped wells is a new wireless rod pump controller recently rolled-out by e-Production Solutions Inc. (eP): the iBEAM RPC. According to Karl Sakocius with eP, Houston, the iBEAM adds a low-cost option to eP's established product line of rod pump controllers. 

iBEAM components

The iBEAM responds to operators' reluctance to install controllers on low-productivity wells with a unique, self-contained design that uses proven technology without requiring the traditional cabling and trenching associated with most RPCs. "The wireless design eliminates the installation costs of laying cables from the load cell and position sensor on the pumping unit to the controller, resulting in a unit that costs less than $2,000," says Sakocius. "That is about half the cost of prior industry technology."

iBEAM's beam-mounted, self-contained,
solar-powered sensor and communication unit

The controller uses a strain gauge to measure load and an accelerometer to measure the position of the polished rod, accepted approaches that are used in a variety of RPCs offered by eP and others. Historically, this has proved to be the most accepted method to control rod-pumped wells. A radio signal sends commands to the well's motor starter relay, and communicates operational data for remote monitoring. The radio can also be used to provide data to an operator's handheld device. The controller optimizes the restart timing by readjusting idle time, based on the most recent pump cycle history. Proper timing of the pump cycles keeps the fluid level low, allowing maximum inflow in a low-pressure reservoir, but avoiding the fluid pound mentioned above. 

The controller uses the load and speed information to generate a dynamometer card that can be used to identify pumped-off status. This data, as well as run time, can also be stored for later analysis. The self-contained unit, clamped to the walking beam of the rod pump, is powered via solar power.

According to Sakocious, a recent beta test of the iBEAM RPC on a low-productivity well in Texas illustrates its benefits for marginal wells. "The well was pumping 6 BOPD at 50% cut from 2,300 ft., on a timer set to pump 12 hours each day. After installing the iBEAM controller, pumping time was reduced to 3 hours per day, with no reduction in oil. With the monthly reduction in pumping hours totaling nearly 270 hours, the monthly savings in power cost alone was $125."

But the savings expected from a reduction in the number of repairs could be much more significant. Depending on the specific conditions, RPCs have reportedly cut the incidence of pump and rod failures more than 20%. The cost savings of a single avoided workover to repair parted rods more than likely would be sufficient to cover an iBEAM installation's entire cost.

The iBEAM RPC provides a relatively low-cost yet technically robust solution to the problem of monitoring and controlling low-productivity rod-pumped wells. It can also serve as a first step for operators who, after becoming convinced of the economic benefits such systems can provide, take further steps toward building an even more sophisticated system for instantly responding to RPC-reported changes in well performance. Ultimately, this can lead to more efficient application of a limited workforce, further cost savings, and improved profitability.

For further information, contact Lance Cole at lcole@pttc.org.