Natural gas processing includes all the operations performed on the raw gas extracted from the deposit that will make it usable; natural gas must be dry, contain no water or hydrocarbons in a liquid state, be free from its acid gas components and toxic solids, and have a stable calorific value and density. On the production site it is preferable to perform only the operations that make the gas transportable, i.e. separation and de-acidification:
Most wells produce a combination of gas, oil, and water that has to be separated prior to any processing operation. A natural gas condensate is a liquid mixture of light hydrocarbons obtained by the condensation of certain raw natural gases. The gas with the condensates removed contains lighter hydrocarbons and undesirable constituents, CO2, sulphur compounds, and water, which are separated by means of the steps below.
The choice of technology is primarily based on the acid gas content of the raw gas. The acid removal processes fall under three main categories: adsorption, oxidation-reduction, absorption (as in amine scrubbing).
The gas fraction enriched with sulphur during the removal of acid gas cannot be sent directly to the incinerator because regulations require reducing emissions of SO2 and other sulphur compounds. Sulphur recovery units (SRU) are essential; they use Claus-type processes, which convert the H2S to elemental sulphur that is easily stored and recycled. A tail gas results that, before incineration, must be treated by special processes (Scot Clauspol, etc.)
After processing, the natural gas can also be converted into very pure – i.e. free of polluting sulphur and aromatics – liquid hydrocarbons (naphtha or diesel) by means of the GTL (Gas to Liquid) technology based on the Fischer-Tropsch process (catalysis of CO and H2 converted to hydrocarbons). This technology is increasingly important in terms of the environment ("clean" fuels). It also makes it possible to transport gas over long distances by tankers and pipelines, which is simpler and safer than the LNG chain, and then store and distribute it through conventional systems.
Sofren engineers specializing in these projects have particular expertise in process engineering and gas project management. They specialize in strategies relating to the design and completion of works broken down into packages.