Hart Energy Publishing
 

Pump pays off

Article by Dick Ghiselin
March 1, 2005
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Electrical submersible pumps (ESPs) have been around for decades. For the most part, they quietly do their jobs until they are pulled for routine maintenance, or fail, whichever happens first. Failure can be costly, with repair and replacement costs coupled with workover costs and the cost of lost production during the shutdown period. Even more costly is the ESP that produces sub-optimally for years, decreasing the well's potential one barrel at a time.

ESPs are elegant in their simplicity. Conveyed to the producing zone on tubing or electrical coiled tubing (e-Coil), most require only a power cable and a surface variable speed drive and they will pump away 24/7 with little trouble. But it was not ever thus. Back in the mid '90s, Petroleum Engineer International published a multi-part series consisting of page after page of ESP failure data, and these data gave rise to an idea. What if the pumps could monitor their own conditions and telemeter the operating data to surface for analysis?

The personal approach

One company that took up the challenge was eProduction Solutions, now a division of Weatherford International. Although not alone in this endeavor, eProduction Solutions has created a comprehensive list of applications for EPSs that could report their condition. At the same time, they developed solution sets for any number of tasks, including pump setup and testing, integration with client production management networks, continuous monitoring and reporting, memory (black box) monitoring, field optimization, failure prediction and analysis, pumping efficiency optimization, power conservation, and production system simulation.

Most intelligent ESPs have the capability to piggyback telemetry and control signals on the power cable itself, thus greatly simplifying the installation. With a single cable serving double-duty as power and telemetry/control line, environmental feed-throughs at wellhead and pump are not affected, and standard existing ones will suffice. In the pump, sensors can be installed that measure motor and bearing temperature, intake and output pressure, pump rpm, multidimensional vibration, voltage, current, frequency, load factor, water cut, flowrate and other factors. The pumps can be made as sophisticated as the operator wants based upon his field requirements, risks and workover costs. Entire production systems and individual or multistage pumps can be designed for each situation - the one-size-fits-all approach is not necessary.

The result is a pump that can be designed, built and tuned for top performance, and one that will give early warning when it starts to wear out - plenty of time to put it in the workover schedule so production downtime and pump refurbishment costs can be minimized.

Any pump can get 'smart'

Another feature of this software is that it works for any pump. In fact, the first program the company recommends is a field analysis and design program that integrates reservoir information with production system constraints to help the operator figure out the best specifications for the pumps. Even fields with a mixture of pump brands can be optimized. New pumping wells can be added, and the program will calculate the effect of the new well plus already existing wells. "What if?" games can be played until the operator is satisfied that the most economical long- and short-term solution has been developed.

Once the pumps start feeding operating data into the surface computer, ESP software collects and analyzes the information needed to discover inappropriate or inefficient operation of the ESP wells. Wells with commonalities can be grouped for analysis when it makes sense, and reports can be generated to compare results against design criteria for a single well, or any size group of wells. Automatic software alarms can be invoked to alert field personnel (or office workers via satellite channel) of any dangerous or undesirable trend. Alternatively, wells can feed a local area network so that field operators can poll the system from the field controller when they arrive on their routine maintenance visits to quickly identify any wells needing attention, as well as their priority.

Easy-to-use and read graphical interfaces are provided so field personnel can observe specific data points or view trends. Historical data can be quickly accessed so deviations can be analyzed and incident frequencies determined. Changing reservoir conditions that might affect pump efficiency or operation are catalogued and can be tracked along with pump data. Even details like perforating plugging or skin buildups can be detected and identified by the system. The general protocol of the system is to operate "by exception." This means that operators are not deluged with "Status Green" reports - only wells needing attention are flagged automatically. Of course, an operator can access any well in the system on command.

Smart pumps live longer, produce more oil

The use of intelligent pumping systems was pioneered by Amerada Hess, which has used the technology to achieve average run lives of more than 6 years. The dynamic operating software lets the operator set and maintain optimum operating parameters for each well and also lets him/her set performance tolerances, and the minimums and maximums, the pumps must stay within before alarms are sounded. These can be applied to pressure, temperature, voltage or pump speed - anything the operator needs to aid the decisionmaking process and keep it proactive rather than reactive. In fields that occasionally pump off, sensors can stop the pump before damage or overspeed occurs, automatically restarting the pump when normal fluid levels are reestablished. As a result, no production time is wasted. Similarly, conditions such as buildup of paraffin, water or gas coning, or sanding can be detected before productivity is compromised.

Pump diagnostic software can be used by engineers to analyze individual pump performance against test-bench norms to predict the onset of wear long before it becomes critical. When these data are observed over time, trends that indicate the incipient failure mode can be identified. Economic analyses can be applied to determine the effect on lifting costs so decision priorities can be set within the business model.

For fields under complex production schemes such as CO2 flooding, pump analysis can be performed on a stage-by-stage basis. The miscible fluid model can accurately describe fluid behavior in each stage of a pump, with either fixed-frequency or variable-frequency drive equipment, in a field undergoing CO2 injection.

Smart operators use smart pumps

In addition to helping operators design and choose the right pump or pumping system, and in addition to enabling continuous monitoring of well and pump performance for production optimization and maintenance management, the software provides valuable information to feed the business models that drive the enterprise. While cost control is important, it pales in the face of production optimization benefits. The increases in field productivity can pay for intelligent pumping systems in weeks or months. After that, everything goes to the bottom line.