Fuel Gas Conditioning issues that cause shutdown to instrumentation and compressor packages are a great concern for our clients. This can be caused from liquid loading, liquid fallout, or hydrate formation. This usually occurs during ambient temperature swings that cools the gas and then causes fallout and locks up the fuel lines. This case study will specifically focus on fuel gas for a gas lift. Gas lift is a method of artificial lift that uses an external source of high-pressure gas, usually a compressor, for supplementing formation gas to lift the well fluids. The principle of gas lift is that gas injected into the tubing reduces the density of the fluids in the tubing. The bottom line is if the compressors shuts down, production completely shuts down.
The Challenge:
A client’s compressors in South Texas were shutting down because of alarms signaling misfires. This was caused because of the gas quality of the fuel gas entering the compressor. Also, after further investigating the issues, there were so many liquids that were falling out that it was overwhelming the fuel pots and going into the engine, which caused shutdowns. As winter was approaching, there was a continuous decrease in ambient temperatures and in the temperature swings as well. These issues were manageable, but the shutdowns were now occurring on most days during the cool off periods which meant evenings and at night. This caused operational issues for our clients, requiring them to have technicians be at the location most nights to restart the compressors. This ultimately became a financial and operational liability.
The Solution:
When it comes to cleaning fuel gas for typical engines, CROFT sees it is not so often that a BTU reduction is needed but the amount of the heavier gas components that are in the gas. Removing the hexanes, pentanes, and a chunk of the butanes and propane really helps to increase the reliability in the engines. After talking to engine experts from Caterpillar and engine package engineers from some of the leading compressor and generator rental companies, we learned that these heavier components along with the instability in the gas quality decreases engine reliability and increases maitenance needed.
The client was recirculating around 8-10 MMcfd of gas and consuming an estimated 450 Mcfd of fuel gas per day in the compressors.
CROFT’s solution was the Fuel-Gas Conditioning System a unique, skid-mounted hybrid unit designed to remove water and high BTU’s for compressor fuel and instrumentation gas. The Fuel-Gas Conditioning System incorporates the Ambient Cooling System to initially cool the gas. The Joule Thomson System then removes hydrates and hydrocarbon liquids, lowering the BTU and reducing the water dew point. Lastly, the Passive Dehydration System® further reduces the dew point well below the pipeline specifications using CROFT’s enviroDRI desiccant.
Benefit:
Being that the system has no burners, or emissions the client required no regulation permitting and CROFT was able to deliver equipment within 48 hours of the signing of leasing contracts. CROFT personnel were able to provide startup assistance and get the system going within 8 hours of delivery. The system was modular designed, so drawings were sent to the client’s 3rd party welders or lease crews to start fabrication. The client’s glycol dehydration systems and amine plants were running longer between shutdowns. The shutdowns from preventable issues such as foaming, sludging, and hydrocarbon carryovers were reduced by 80%. Wear and tear on equipment and parts such as pumps were greatly reduced as well.
Result:
The unit worked for the entirety of the winter, during the 4th and 1st quarters, totaling 26 weeks, with only one interruption handling the volume swings, saturation swings from pressure and temperatures, and maintaining an outlet dewpoint. The interruption was caused by a throttle on the JT valve to go bad and after a swap from a CROFT technician, the unit has operated properly since. Once the summer months started and temperatures began to rise, the units were left on location but were bypassed and put on a standby rate for the customer until the next winter.
Learn more about our Fuel Gas Conditioning System.
