| Popis: |
In oil industry economic context, the clean-up of wells through surface production facilities is an option in order to minimize environmental impact, economize rig days and commercialize produced clean-up oil. Clean-up operations through offshore topside production facilities started to be performed some years ago. However, many risks must be considered, especially production chemistry risks linked to compatibility between drilling/completion and production fluids. The goal is to ensure process stability and final quality of oil and produced water which, in many cases, must comply with rigorous specifications for coastal discharge or reinjection into the reservoir. This study shows the methodology developed to evaluate separation and deposits risks. As a general observation, experiments performed show a degradation of the separation process when drilling/completion fluids (completion brines and CaCO3 particles from drilling muds) are added to the emulsion. The most probable hypothesis is that some solid particles will adsorb at the oil-water interface and affect the stability of emulsions. Nevertheless, additives that change the wettability of solids seem to enhance separation, ensuring a separation efficiency equivalent to the system without particles. In the case of oils that contain very high molecular weight naphthenic acids (TPA), the use of brines with calcium chloride increases the risk of naphthenic salt deposits at topside facilities. The degradation of the water quality was also observed and the optimization of a reverse demulsifier is then required. The final clean-up strategy should also be adapted to topside design and possibilities to handle drilling fluids. How to separate and recover debris could be a problem for brown fields. For new projects, some additional provisions may be included in the design for well clean-up. In any case, a multidisciplinary risk evaluation is always required to ensure the good progress of this type of operations. |
