No abstract

This paper describes the hydrate management strategies in Statoil’s gas and oil production systems. Hydrate management is a risk based approach allowing operations within the hydrate domain when the risk for hydrate plugging is concluded to be low. This is in sharp contrast to the hydrate avoidance approach practiced by Statoil in the past. Statoil has over 500 subsea wells and more than 100 subsea flowlines in operation. The hydrate management strategies take advantage of the intrinsic properties of the fluid systems, the hydrodynamics, and the plugging risk related to the amount of water present in the different parts of the production systems. This approach is based on a large body of research performed at Statoil and on extensive field experiences. Statoil’s current best practices in different production systems are described, and relevant examples from the field operations are provided.

The role of water in the deactivation of Al2O3-supported cobalt Fischer−Tropsch catalysts has been studied at different water partial pressures. In addition, model studies at nonreacting conditions using H2O/H2 feeds were carried out in order to study the possible reoxidation of cobalt by water. High-pressure gravimetry, temperature-programmed reduction (TPR), and X-ray photoelectron spectroscopy (XPS) were used as characterization methods in the model studies. The kinetic studies showed significant deactivation when water was added to the feed in fixed-bed reactor experiments. In the model studies, a large extent of bulk cobalt reoxidation was only observed in the absence of H2. Only a small amount of reoxidation could be observed when H2 was present, even at high H2O/H2 ratios. However, XPS studies indicated significant surface oxidation of cobalt at a lower H2O/H2 ratio. Surface oxidation or oxidation of highly dispersed cobalt phases is therefore concluded to be responsible for the observed deactivation. The possibility of changes in the phase distribution of the catalysts caused by the presence of high water partial pressures is discussed on the basis of TPR studies of H2O/H2- and H2O/He-treated catalysts.