Oil and Gas Development - Onshore Industry - Pollution Prevention Guidelines
Pollution Prevention Guidelines to provide technical advice and guidance to staff and consultants involved in pollution-related projects. The guidelines represent state-of-the-art thinking on how to reduce pollution emissions from the production process. In many cases, the guidelines provide numerical targets for reducing pollution, as well as maximum emissions levels that are normally achievable through a combination of cleaner production and end-of-pipe treatment. The guidelines are designed to protect human health; reduce mass loadings to the environment; draw on commercially proven technologies; be cost-effective; follow current regulatory trends; and promote good industrial practices, which offer greater productivity and increased energy efficiency.
Table of Contents
- Industry Description and Practices
- Waste Characteristics
- Pollution Prevention and Control
- Target Pollution Loads
- Treatment Technologies
- Emissions Guidelines
- Monitoring and Reporting
- Key Issues
Industry Description and Practices
This document deals with onshore oil and gas
exploration, drilling, and production operations.
Refining operations are covered in a separate
document. Testing, delineation, and production drilling
are integral to hydrocarbon reservoir development,
which involves the use of drilling rigs, associated
equipment such as casing and tubing,
large quantities of water, and drilling muds. In
the process, oil and gas are moved to the surface
through the well bore either through natural
means (if the reservoir has enough pressure to
push the oil and gas to the surface) or through
induced pressure by means of a pump or other
mechanism. At the surface, oil, gas, and water
are separated. Crude oils with associated gas containing
more than 30 milligrams per cubic meter
(mg/m3) of hydrogen sulfide are normally classified
as “sour crude.” The crude oil may require further processing, including the removal of associated gas. Oil produced at the wells is piped or shipped for use as feedstock in petroleum refineries.
Natural gas is predominantly methane with smaller amounts of ethane, propane, butanes, pentanes, and heavier hydrocarbons. Gas wells produce small quantities of condensate, which may require processing. Separation processes generally use pressure reduction, gravity separation, and emulsion “breaking” techniques. The gas that is produced may be used directly as fuel or as feedstock for the manufacture of petrochemicals. It may also contain small amounts of sulfur compounds such as mercaptans and hydrogen sulfide. Sour gas is sweetened by processes such as amine scrubbing.
The main wastes of environmental concerns associated
with onshore oil and gas production are
drilling-waste fluids or muds, drilling-waste solids,
produced water, and volatile organic compounds.
The drilling-waste muds may be
freshwater gel, salt water (potassium chloride or
sodium chloride), or oil invert–based systems.
The oil invert mud systems may contain up to
50%, by volume, of diesel oil.
Drilling wastes may contain drilling muds (bentonite), borehole cuttings, additives (polymers, oxygen scavengers, biocides, and surfactants), lubricants, diesel oil, emulsifying agents, and various other wastes that are specifically related to the drilling activities. Drilling-waste solids, which are made up of the bottom layer of drilling-mud sump materials, may contain drill cuttings, flocculated bentonite, and weighting
materials and other additives. Additional wastes from the drilling process include used oils, cementing chemicals, and toxic organic compounds.
Field processing of crude oil generates several waste streams, including contaminated wastewater, tank bottoms that may contain lead, emulsions, and heavy hydrocarbon residues, which may contain polynuclear aromatic hydrocarbons (PAHs). Cooling tower blowdown, boiler water, scrubber liquids, and steam production wastes are also generated, as well as contaminated soil, used oil, and spent solvents.