Fugitive Hydrocarbon Emissions from Pacific Offshore Oil Platforms: Models, Emission Factors, and Platform Emissions

Abstract

In 1989, the U.S. Department of the Interior sponsored a field study that included the measurement of fugitive hydrocarbon emissions from seven offshore oil and gas production platforms located in outer continental shelf waters off the coast of Southern California. This study generated a set of emission factors for five different models for ten different combinations of component style and product stream as a function of a component's screening value measured one centimeter from the source with an organic vapor analyzer (OVA). These emission factors (ranging from 1 × 10^-6 to 8.05 pounds of total hydrocarbon per day per component) are utilized together with an inventory of the components and the OVA screening value for each component to estimate total platform fugitive hydrocarbon emission rates. For the seven platforms included in this study, the total platform emission rates ranged from 42 to 140 pounds of hydrocarbon per day with more than 70 percent of the emissions due to a very small number of large emitters. The average platform non-methane emission rate was 20 pounds per day. A comparison with measurements made a decade ago indicates that technological advances and adoption of inspection and maintenance practices have reduced fugitive hydrocarbon emissions from these offshore facilities by more than 75 percent. Components in gas service were observed to have emission factors about an order of magnitude greater than the same components in liquid service due to the greater leak frequency of components in gas service.