Energy Storage for Natural Gas Fueled Electric Drilling Rigs

Abstract

Abstract The drilling industry is in search of an environmental and economical solution to rising fuel costs and tightening emissions regulations. Alternative engine technologies have been deployed and are challenging the conventional compression ignition diesel engine for drilling operations power generation. This includes the spark ignition natural gas engine generator which operates on processed natural gas (LNG or CNG), field gas, pipeline gas, or combinations of these. Compared to a diesel powered drilling operation, annual fuel cost savings of today's natural gas powered drilling operation can be expected to range from $300K when using processed LNG or CNG to $1.5 million when using field gas. Natural gas engine generators offer significant fuel cost savings and sizeable reductions in emissions. However, diesel engines have much better load characteristics compared to natural gas engines and respond more reliably to dynamic loads dictated by abruptly changing drilling functions. Combining energy storage with a natural gas engine generator results in a hybridized drill rig that offers both improved performance and fuel economy. An adequately sized energy storage system provides the operator of a natural gas fueled, land drilling rig with reliability and responsiveness superior to a diesel rig. Use of resistive load banks, excess generator capacity, and backup generators are minimized or even eliminated. UPS powered ride-through ensures electrical power quality with less vulnerability of generator output to variations in field gas flow rate and methane content. In addition to boosting rig performance, this hybrid rig technology offers economic benefits: • reduced natural gas fuel consumption by operating the engine at a higher more fuel efficient load and through less use or even elimination of the resistive load bank • less frequent maintenance and longer engine life as a result of operating more consistently at higher loads • reduced engine generator costs through rig operation primarily with one engine generator Compared to a diesel powered drilling operation, annual fuel cost savings of the hybrid natural gas powered drilling operation with energy storage are projected to range from $920K when using processed LNG or CNG to $1.7 million when using field gas. With performance driven beyond diesel rig levels combined with the significant fuel savings and emissions reductions, natural gas powered drilling rigs are expected to see greater acceptance with the hybrid electric approach.