Emulsifying systems

The industry has had to react in recent years to significant major challenges, improving both chemical stability of the emulsifier system and impact on the environment. This latter factor covers both occupational health and ecological hazards resulting from contact with the fluids themselves and the wastes generated, mainly drilled cuttings. Under pressure from state environmental agencies, the industry, particularly offshore, is being pushed to use fluid system components exhibiting maximum biodegradability which should, in
addition, be achieved with minimum oxygen demand. The system components should also be non-bioaccumulative, and the complete systems should exhibit low toxicity on representative species (an alga, a crustacean, and a sediment re-worker or a juvenile fish).

Aipu solids control equipment
Aipu solids control equipment

Clearly offshore drilling operations are where environmental pressure is at its greatest. Low temperatures, lack of oxygen and light at the seabed and an ideal milieu for the dissipation of chemical products are among the most extreme conditions that can be encountered. However, performance requirements of products are also increasing as new types of drilling operation are undertaken (both on- and offshore). Complex wells requiring high lubricity and high suspension capacity, deep-offshore drilling with its characteristics of extreme temperature cycling and excellent hole cleaning requirements
have led to needs for major product performance improvements.

In order to maximise technical performance of emulsifying surfactants for mud systems, it is necessary to implicate temperature stable functions such as imidazolines or amides to link the hydrophobic chain to the polar head. At the same time, in order to minimise ecotoxicological effects it is also necessary to design the manufacturing process such that it works without excess of reactants : indeed, unreacted reagents such as amines have a negative impact on toxicity. Also implicit in the process design is to obtain the maximum conversion of raw materials in order to minimise both the global consumption of chemicals and the production of useless by-products, thereby reducing adverse toxicity and occupational health risks. Biodegradability can be enhanced by the inclusion of unsaturated functions placed in the alkyl chain. Finally the stability of the emulsion can be fine-tuned by the reduction of surface tension and adequate mobility of the surfactant at the interface.

The system developed in the present paper meets all of these criteria and is referred to hereafter as the Superamide family of chemicals. Our objective was to develop new emulsifiers with increased thermal stability for use in low-impact syntheticbased muds. To attain this objective we decided to concentrate upon alkanolamides which are chemically resistant at high temperatures. Long chain alkanolamides with 18 or 22 carbon atoms were chosen in order to limit the mobility of the molecule at high temperature, which could destabilise the emulsion.

These molecules are prepared by transamidification of an ester of a fatty acid (oleic, linoleic, linolenic or erucic) by way of a controlled process that allows very low amounts of residual amine and fatty acid to be reached. A number of preparations (SA2, SA3, ‚Ķ) were developed, having varying chain lengths and using different transamidification agents. The amount of amine in each final product is less than 0,05%. The ester of the fatty acid used is derived from vegetable oil triglycerides. The use of this raw material of vegetable origin and the low amount of residual amine from the process give a non-ecotoxic emulsifier, useful for the stabilisation of low-polluting SBM’s at very high temperatures.

The ecotoxicological impact of the new emulsifier has been determined by NIVA, the Norwegian Institute for Water Research, specialised in the evaluation of ecotoxicity of oilfield fluids used in the North Sea region.

The tests involved are those defined by OSPAR :

  • Biodegradability under the protocol OECD 306 (closedbottle, sea water test)
  • Bioaccumulation under the protocol OECD 117 (high pressure liquid chromatography (HPLC) derivation of the n-octanol/water partition coefficient : log POW)

both conducted on the secondary emulsifier (Superamide) alone (i.e. as a single component)

    • Measures of toxicity on the three species defined by OSPAR :
      • Marine Algal Growth Inhibition (ISO 10253) on Skeletonema costatum
      • Acute Toxicity (ISO / FDIS 14669) on the crustacean Acartia tonsa
      • Acute Toxicity (KM Lab (98) Sediment Phase Toxicity Test. S.O.P. Lab IIA 1.5, 1st Aug 1999, version 3) on the sediment re-worker Corophium volutator

all conducted on a formulated fluid system comprising a baseoil (H1), brine (20% CaCl2), primary emulsifier (fatty acid), secondary emulsifier (Superamide), Ca(OH)2, glycerol

The results indicate that the product is of very low toxicity and is more than acceptably biodegradable. The bioaccumulation result is likely to be highly misleading as the method used is not adapted for use with surface-active materials.

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