Parallel Natural Gas Generators to Save Costs, Cut Flaring
The North American oil and gas industry has experienced unparalleled growth of oil production over the last five years. Since 2009, the U.S. and Canada have steadily increased oil production year to year. By 2014, the U.S. surpassed Saudi Arabia and Russia as the world’s largest oil producer with a production rate of 12.5 million barrels per day (b/d). At the same time, Canada became poised to top China as the fourth largest oil producing country. In 2014, Canada reported a production rate of 4.3 million b/d compared to China’s rate of 4.4 million b/d.
Along with increased oil production come increased requirements and restrictions. Oil and gas producers must find ways to comply with emissions regulations, such as North Dakota Industrial Commission (NDIC) flaring restrictions, without hindering overall production.
New products have emerged to meet the needs of the oil and gas industry. A natural gas generator consumes wellhead gas as a fuel source and, in turn, provides power to the well site. So not only does a natural gas generator reduce fuel costs, it also reduces flaring emissions and helps avoid the penalties used to enforce the restrictions. The ability to parallel natural gas generators is gaining popularity as a solution for avoiding downtime and achieving acceptable emissions levels for oil and gas applications, specifically those in remote oil fields where even planned downtime can mean a significant loss of revenue.
Paralleling capability provides oilfield engineers the flexibility to design redundancy into their application. If a particular project requires 300 kW of power, selection of a single 300 kW generator would certainly do the job, but would not provide any redundancy. That means any generator downtime would result in lost production. When an oil well is producing thousands of dollars of revenue an hour, any loss of production — whether due to scheduled maintenance or unexpected downtime caused by machine failure — can result in a significant loss of profits for the oil well operator.
One solution is the same project powered by two 300 kW generators with paralleling capability. The two generators share the load, meaning each generator supplies 150 kW to the application. However, if one machine has a problem and shuts down, or needs to be taken offline for maintenance, the other unit seamlessly takes on the full load and the job avoids any downtime.
While paralleling diesel generators is common for mission-critical applications, such as live events, paralleling natural gas generators make it possible for oil producers to continue operations around the clock — an appealing scenario when thousands of dollars of profit are at stake.
The setup of paralleling generators, especially those using wellhead gas as a primary fuel source, can be a complex process. But, as demand for such applications continues to grow, manufacturers are finding ways to improve the technology.
For generators to operate in parallel, three conditions must be met. The first is that all paralleling generators must be able to measure and adjust accordingly to match voltage. Second, paralleling generators must provide as close to 60 Hz output as possible. Even a minor variance in frequency between generators will cause the machine operating at a lower frequency to perform like a motor, ultimately consuming power instead of producing power. The third condition requires power output to be precisely in-phase. If paralleling generators are not in-phase, the slower machine will be forcibly thrust into phase, likely causing extensive damage to, or failure of, the generator. When all three conditions are met, the generators are considered to be synchronized. At the precise point where the generators reach synchronization, the control system sends a command to close the circuit breaker. Once this process is complete, the generators are now operating in parallel and will begin sharing load.
The sophisticated control system and electronically controlled circuit breaker needed to successfully meet the paralleling conditions are the major differentiators between standard generators and those with paralleling capabilities. The control system will make adjustments to generator voltage and engine speed in order to bring the units into synchronization and will command the electronically controlled circuit breaker to close only when the units are precisely synchronized.
Once connected and operating in parallel, the control system continuously monitors the power demand and ensures all units are sharing load equally. It also provides assurance that, should one unit experience a problem, the load will automatically transfer to other generators in the system and isolate the unit with the fault.
A factory-installed paralleling solution assembles the necessary equipment, ensuring the machines are effectively communicating and reacting to the whole system. The integrated control panel communicates digitally between the generators, providing each machine the information necessary to synchronize and equally share the load. A standard generator is only able to monitor its own operating conditions and remain within the limits of those conditions. It is unable to effectively communicate and synchronize with other machines and, therefore, unable to share the load successfully.
Much like their diesel counterparts, paralleled natural gas generators require a specially trained mobile generator dealer to provide setup of the machines. The sophisticated controller and electronically controlled breaker have made the basic day-to-day operation of paralleling generators — start and stop — a fairly simple process once the generators are set up in the oil field.