"Phase Behavior of Petroleum Reservoir Fluids" by Karen Schou Pedersen, Peter L. Christensen

Oil and gas properties have had our professional interest for the past 25 years. With this book we want to share our experience with others interested in this fascinating subject.

We first became interested in oil and gas properties in the late 1970s when the oil and gas production from the North Sea had just started. The oil companies operating in that region were facing practical problems not seen anywhere before. New technical solutions had to be invented to make the oil production competitive with that from other regions. After a few years it became common practice in the North Sea to transport untreated multiphase well streams over long distances in subsea pipelines connecting smaller fields with existing process facilities. At the temperature of the sea bottom, an untreated well stream may undergo all kinds of phase transitions. The standard PVT experiments that had developed in the oil industry did not cover phase behavior at seabed temperature and did not take into consideration that a well stream often carries formation water from a water zone beneath the oil zone.

Thermodynamic models and phase equilibrium algorithms were needed that were capable of predicting the phase behavior of petroleum reservoir well streams, considering several fluid and solid phases. Such models could not be developed without experimental data. In the 1970s and early 1980s, it was unusual for an oil company to publish its in-house phase equilibrium data. The Norwegian oil company Statoil was among the first to realize that this practice had to be altered for the oil industry to be able to cope with the enormous challenges in the North Sea. We are grateful to Statoil and especially to Per Thomassen, Hans Petter Ronningsen, Otto Rogne, Knut Kristian Meisingset, and Jess Milter for being prepared to share its in-house fluid property and phase equilibrium data with the public. The data material published by Statoil has been the basis of extensive modeling efforts at universities and in the oil industry all over the world, and has helped to convince other oil companies about the usefulness of making in-house data available for public.

The book takes a compositional approach but acknowledges that “black oil” simulations are still in frequent use in the oil industry. It may therefore also be the right textbook in PVT courses having the aim to prepare the students for compositional fluid simulations but still accepting the need for them to understand “black oil” terminology.