For onshore oil & gas production well pads, effectively managing and recovering vapors means improving emissions control to meet regulatory requirements, increasing saleable natural gas, and providing a safer work environment for the personnel who manage the well pad site.In one of the Produced Fluids Management recorded webinars, Tank Vapor Control and Recovery in Upstream O&G, Emerson’s Frank Goulet discusses the challenges oil & gas operators face controlling emissions and complying with environmental regulations and some ways to address these challenges.
In the U.S., the Environmental Protection Agency (EPA) Quad-O regulation, short for Code of Federal Regulations (CFR) 40, Part 60, Subpart OOOO:
…establishes emission standards and compliance schedules for the control of volatile organic compounds (VOC) and sulfur dioxide (SO2) emissions from affected facilities that commence construction, modification or reconstruction after August 23, 2011, and on or before September 18, 2015.
Franks notes that this means around a 95% reduction in limits and steep fines for exceeding these limits. Vapor losses typically occur via flashing, working and standing. Flashing losses occur through higher pressure separator oil transfers to atmospheric pressure tanks. Working losses are caused by the rapid oil level changes during filling or pump out operations. Standing losses are caused by temperature and barometric pressure changes.
The airspace above the tank is dynamic constantly changing from entrained gas in the fluids coming into the tank, blanketing gas and pump out operations. Controlling the vapor space is critical to prevent air ingress to cause potentially combustible air/gas mixtures and moisture causing corrosion. Frank showed a typical 6 wells, 6 tanks per well site with a tank hatch seal leak having annual blanket gas losses of almost $300,000 per year.
He describes the layers of tank pressure control for both in-breathing and out-breathing conditions. In out-breathing conditions, capturing the vapors with a vapor recovery unit is the first step before more serious layers of safety occur. For in-breathing conditions, controlling the blanketing gas pressure to prevent combustible air/gas mixtures to develop before more serious steps must occur. The emergency in-breathing layer of protection is often missed. If all layers fail an implosion of the tank will occur.
Watch the webinar for more on the role of wired and wireless pressure vacuum relief vents and wireless emergency venting, and best practices in vapor control and recovery via smart vapor management (SVM) technology.