Chemical waste discharges 

Bench-scale separation rig at the Research Centre laboratory.

 

A great variety of chemicals are used in many aspects of hydrocarbon production, and not least for guaranteeing that crude oil meets market specifications.

Although such substances are essential, some of the spent chemical waste inevitably becomes incorporated in produced water. Much of this is discharged to the sea.

Knowing which chemicals are being discharged and the exact quantities involved is essential in complying with the requirement for zero harmful discharges set by StatoilHydro and the Norwegian government.

This naturally calls for an immensely complex audit, which has so far been fairly inaccurate.

StatoilHydro has therefore developed a superior user-friendly technique to overcome some of the basic problems.

This provides not only more reliable results, but also the opportunity to focus on which chemicals are potentially most harmful to the natural environment and should therefore be replaced by more environment-friendly substitutes.      

The division of polluting chemicals between water and oil – known as the distribution factor – was previously estimated from laboratory studies using standard water and a model oil called octanol. And this is where the problem lies.

To get closer to the true position, StatoilHydro has carried out experimental work on 35 of the most important chemicals using real crude oil and genuine produced water.

The results are revealing, since the distribution factors found using real systems differ significantly from those based on laboratory standards.

Group researchers have also systematised their results and simplified the calculation of distribution factors in a spreadsheet-based mass balance model.

This model is so easy to use that it allows StatoilHydro’s environmental coordinators – rather than its research specialists – to produce the annual voluminous field reports required by the authorities.