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How are synthetic drilling fluids defined?
What factors lead to a drilling fluid being classified as a synthetic?
There are two on-going debates in the Exploration and Production community about synthetic drilling fluids:
- "What defines and classifies a drilling fluid as synthetic?"
- "Are there really environmental benefits to using synthetic drilling fluids?"
In this section we'll explore the definitions given by various regulatory agencies to help clarify the factors that lead to a drilling fluid being classified as a synthetic.
What is a synthetic?
In basic terms, "synthetic" applies to the process by which the end product was manufactured, where the ending molecules of the process are not normally found in nature. Fluids from chemical processes are defined as being "synthetic", while fluids extracted from refinery streams are generally defined as being "oil-based."
In order to define "synthetic", as it applies to drilling fluids, we reviewed the non-aqueous drilling fluid (NADF) offshore disposal regulations as legislated in several parts of the world. This included NADF regulations from Europe (OSPAR, 2000), the United States (USEPA, 2001), Canada (CNOSP, 2002), and Australia (DoIR, 1999). We also included a comprehensive review of NADF by the International Association of Oil and Gas Producers (OGP, 2003).
|Base Oil||Process||Europe (2000)||Canada (2002)||US (2001)||Australia (1999)||OGP (2003)|
|Mineral oils/ paraffins||Refinery extraction||OBF||OBF||OBF||OBF||OBF|
|Mineral oils/ paraffins||Refinery extraction and severe hydrotreatment||SBF2||EMOBF3||EMOBF||NA4||EMOBF|
|Synthesised paraffins||Fischer - Tropsch or LAO hydroformylation||SBF||SBF||SBF||NA||SBF|
|Linear alpha olefins||Ethylene oligomerisation||SBF||SBF||SBF||SBF||SBF|
|Internal olefins||LAO isomerisation||SBF||SBF||SBF||SBF||SBF|
|Esters||Condensation of fatty acids and alcohol||SBF||SBF||SBF||SBF||SBF|
1 OBF = oil base fluid
2 SBF = synthetic base fluid
3 EMOBF = enhanced mineral oil base fluid
4 NA = not addressed
As the chart shows, all the regulatory bodies and organisations agree that diesel, mineral oil and paraffins extracted from refineries are oil base fluids (OBF). They also agree that synthetic base fluids (SBF) include paraffins produced via Fischer Tropsch (gas to liquids) or linear alpha olefin hydroformylation processes, linear alpha olefins, internal olefins, and esters.
Controversy, however, continues over fluids extracted from refinery streams that are severely hydrotreated. Hydrotreatment is a processing step used to convert aromatics in fluids to paraffins. In the process, some minor chemical reactions occur as the aromatics are treated. Europe's OSPAR classifies such fluids as "synthetic". The US EPA, CNOSP and OGP classify these products as neither an SBF nor an OBF, but instead create an entirely new category known as enhanced mineral oil base fluid (EMOBF).
By reviewing product classifications, we learn that the "synthetic" label has little bearing on environmental impact. There are differences between products labelled SBF, OBF, and EMOBF. Even within a certain class of compounds (eg paraffins), some products may have less environmental impact than others.