Emissions Regulations Fuel Development of Separation Technology

For years, oil and gas refineries and wellsite service operations have used natural gas flaring as a gas disposal system in testing and well cleanups. Flaring oxidizes and converts waste gases - hydrocarbon gas volumes considered to be uneconomical to recover and process conventionally - into the safest form possible. Flare stacks transport waste gases above ground to an elevation that is sufficiently adequate for the gases to mix with atmospheric air and ignite.

Although a common practice throughout the industry, flaring gas systems have recently gained considerable attention among regulatory and environmental bodies. The debate centers on the potential environmental hazards of inefficient gas flaring.

Initiatives for Environmental Protection

Gas combustion efficiencies depend on the composition of the flare stream, the flow rate of flare gases, wind velocity and any turbulence near the flare, and the presence of hydrocarbon or water droplets in the flare stream. Any one of these variables can cause operational problems, which ultimately can lead to serious environmental issues.

For example, high winds can extinguish the flare before the gases can be destroyed. There also is no guarantee that all hydrocarbon gases will be burned off if, for example, the gas and air do not integrate completely due to unfavourable atmospheric conditions such as a crosswind.

With inefficient combustion, sulfur dioxide, nitrogen oxides, benzene, toluene, xylene and other by-products are released directly into the atmosphere. Depending on certain variables and conditions, gas flare efficiencies can be as low as 65 to 70%, which can result in an increase in hydrocarbon gas emissions and significant environmental damage.

To completely dispose of hydrocarbons and gas sulfur compounds, atmospheric conditions must be conducive for combustion to occur and there must be a burn duration of approximately one to one and one-half seconds. These circumstances are not always controllable, nor do they always exist with gas flaring systems. Although oil and gas companies have been aware of the hazards of gas flaring operations, it has been in the last few years that the potential environmental impact of inefficient gas flaring has been given closer consideration by the industry. Increased pressure from environmental and regulatory agencies to eliminate or reduce greenhouse emissions from flaring operations has also spurred the majority of oilfield service operators to either increase efficiency of the flaring process or develop alternative methods to reduce or eliminate flaring entirely.

Alternative Gas Disposal Systems

Naturally some alternatives will work better than others depending on the environment of a particular well project. For instance, modified gas flare stacks and new burner tip designs are being used by some operators to improve efficiency in gas combustion. These burner tip designs are ideal in permanent installations, but are less effective during variable flow conditions commonly found in most well tests.

Other operators are using inline testing to eliminate the need for gas flaring, except in emergencies. Inline testing requires companies to tie the well into permanent pipeline facilities prior to testing or use temporary pipelines to direct the produced gas to an existing gas pipeline or processing facility, thereby resolving inherent environmental problems and the inefficient nature of gas flaring.