Development of Engine Drivers for Unconventional Gas

Abstract

Abstract Objectives/Scope: Gas compression engine drivers used in unconventional resource development require the flexibility to operate with a wide range of fuels, in a wide range of conditions and with a high degree of reliability. This paper demonstrates the processes used to develop a modern medium speed engine driver and the technology leveraged to create an engine with the performance needed to be effective in unconventional gas applications. The resulting engine performance and operating envelop will be reviewed. Methods, Procedures, Process: Engine manufactures have adopted varying strategies for dealing with the challenges new applications present. One manufacturer uses a disciplined, gate driven development process to move from identifying user performance requirements to delivering a fully capable and reliable family of engines that meets the needs of gas compression operators throughout the world. The process for technology selection, laboratory confirmation and field validation is described. A system by system review of the selected engine technologies is presented, along with their specific contribution toward enabling the use of lower quality fuel gases found in unconventional developments while also enhancing other performance attributes. Results, Observations, Conclusions: Laboratory data that demonstrates the validity of individual system designs and the entire functioning engine is provided. Areas of focus will include the benefits of smart fuel valves, real time NOx emissions measurement, the impact of lowering combustion air temperature through two stage intercooling and the effect of reducing the engine compression ratio through piston design and other techniques. In addition to demonstrated engine performance in a laboratory setting, gas compression operators require an exceptionally high degree of reliability to minimize costs, maximize production and reduce operational uncertainty. The process used to validate the reliability of the compression driver in application is discussed, along with the findings of the field validation work and how the process drove changes to the final, production ready engine. Lean burn and stoichiometric combustion technologies are reviewed, along with their impact on combustion design decisions and engine emissions. The complete engine combustion recipe for the new driver is reviewed in detail. Engine performance under varying extremes of fuel quality and other environmental factors is explained. Another challenge in unconventional gas development can be the presence of hydrogen sulfide (H2S) in engine fuel at levels that cause damage to engine components. Engine configurations and operating regimes that help minimize the impact of H2S are discussed. Novel/Additive Information: A new approach for increased compressor throughput by as much as seven percent during periods of lower ambient temperature is presented. The enabling engine technologies and operator strategies for leveraging this capability is described to allow new developments to take advantage of the engine/compressor potential.