Rinaldo A. de M. Vieira (Doctor of
Philosophy in Petroleum Engineering)
Flow Dynamics in Oil Wells
Directed by Dr. Mauricio Prado
305 pp., Chapter 6: Contributions, Conclusions and Recommendations
(270 words) Oil and gas wells
frequently face production stability issues that lead to operational
problems for surface and sub-surface equipements and/or productions
losses. To determine whether or not an equilibrium solution is stable,
two methodologies are used: local linearization analysis and transient
simulation.
The first approach is based on local
linearization around the equilibrium solution
in order to develop simple analytical criteria. Although represented by
easy inequalities that depend on steady-state parameters, these criteria
provide only limited information about the problem. In addition, due to
simplifying assumptions, the criteria usually misrepresent reality and
are also incapable of determining the existence of different attractors
such as limit cycles and strange attractors.
The second approach, transient
simulation, seems to be the method that leads to
results that are closer to reality. This work presents a review
regarding instability of dynamic systems and its application to some
liquid single phase flow system. The validity of such criteria is
discussed and comparisons with incompressible and compressible transient
simulations are made. The vast majority of existing transient simulation
work for oil wells focused on semi-closed gas-lift systems. This type of
instability is quite well understood by the petroleum industry. No
transient simulation work has been conducted with bottom-hole gas
segregation and storage effects, especially considering the use of
Electrical Submersible Pumps and down hole separators.
A two-phase flow code based on the drift
flux approach was developed in this
work, in order to simulate well configurations without packer. For wells
equipped with ESPs, the two-phase flow pump performance as well as
separation models where used. Several examples of casing heading and ESP
oscillatory behavior are shown.
Download
dissertation (TUALP members only)
|