Sergio N. Bordalo

Study of the dynamics, optimization and selection of intermittent gas-lift methods—a comprehensive model

The gas-lift is a widely used method of artificial lift, for which there are different design options. There are empirical rules of thumb to choose between the continuous gas-lift (CGL) and the intermittent gas-lift (IGL), but little exists in the literature for the selection among the different intermittent gas-lift designs. Furthermore, computer simulators for these processes usually are not in the public domain. This work presents a numerical model to study the behavior of the Conventional IGL, the IGL with chamber (IGLC), the IGL with plunger (IGLP) and the IGL with pig. Simulations are presented under various reservoir conditions, for different settings of the operations parameters. The models results can aid the engineer in the determination of the optimum values of the parameters for each design option and in the choice of the most adequate IGL design for a particular well.

Pressure drop coefficients for elliptic and circular sections in one, two and three-row arrangements of plate fin and tube heat exchangers

The objective of the present work is the experimental determination of pressure drop coefficients (loss coefficients) for elliptic and circular sections in one, two and three-row arrangements of plate fin and tube heat exchangers. The experiments permitted to correlate the dimensionless loss coefficient with the flow Reynolds number in the rectangular channel formed by the plate fins. The experimental technique consisted of the measurement of the longitudinal pressure distribution along the flow channel, for several values of air mass flow rate. The total number of data runs, each one characterized by the flow Reynolds number, was 216. The present geometry is used in compact heat exchangers for air conditioning systems, heaters, radiators, and others. Also, it is verified the influence of the utilization of elliptic tubes, instead of circular ones, in the pressure drop. The measurements were performed for Reynolds numbers ranging from 200 to 1900.

Whipping Phenomenon Caused by the Internal Flow Momentum on the Catenary Risers of Offshore Petroleum Fields

A laboratory-scale model was designed to investigate the influence of the internal flow of two-phase oil and gas mixtures on the motion of slender risers hanging in catenary configuration used for offshore petroleum production in deep waters. The behavior of the riser arises from the interplay of various dynamic phenomena: the long length and relatively small diameter of the pipeline confers a cable-like elasticity to the system, which, under static loading, assumes a catenary shape; dynamic excitation caused by environmental conditions generates oscillations. The internal flow momentum may impose a natural whipping displacement — compounding swinging and bending — adding to the concerns of stress and fatigue. The internal flow may display different two-phase patterns (bubbles, slugs, intermittent, annular or stratified mixtures) possessing completely different characteristics; also, the flow-induced dynamic loading depends on the flow rates of both oil and gas phases. Although computer codes have been developed to simulate the motion of risers, there is much need for experimental validation. This research attempts to discern the effects of the internal flow, discriminating it from the other dynamic phenomena. Accelerometers and video acquisition were employed to verify the phenomenon and to determine the frequency spectrum of the oscillations.Copyright

Control: PCP - An Intelligent System for Progressing Cavity Pumps

This paper describes an intelligent system for the management and control of petroleum wells operating with progressing cavity pumps (PCP), named CONTROL: PCP. The purpose of CONTROL: PCP is to maintain the operational conditions of PCPs within the established limits, reduce the operational costs, maximize the useful life of the equipment, and, consequently, increase the profitability of the petroleum wells. The architecture of the system involves expert knowledge for handling an existing database.

Experimental Assessment of the Behaviour of a Pipe Vibration Damper Underwater

Submarine petroleum pipelines, risers and jumpers suffer static and dynamic loads due to sea currents and waves, due to the displacements of the floating production units and due to the internal flow, among other causes. Mitigating the oscillations caused by such excitations is critical to the reliability and fatigue of those underwater bodies. The Pounding Tuned Mass Damper (PTMD) is one device that may be employed to absorb and dissipate vibrations. These devices have long been used for mechanical systems operating in the atmosphere, but are new for underwater applications. This paper presents a study of the behaviour of a PTMD working underwater.A small scale laboratory apparatus was built to assess the effect of the absorber on the oscillation of a pipe submerged in a water tank. The PTMD was attached to a test pipe section mounted on an elastic suspension harness. The PTMD model is a lumped mass-spring attachment similar to a tuned mass dumper (TMD) suppressor, but with the addition of a pounding layer, which limits the motion of the PTMD mass, dissipating the energy of the oscillating pipe through the impact of the PTMD mass against that layer. Free and forced oscillation experiments were executed in air and in water, with and without the oscillation absorber, to determine the effectiveness of the PTMD. The tests were run on a range of excitation frequencies and the amplification factors were obtained for each case.The data show a remarkable influence of the surrounding media on the dynamics of the pipe-absorber system, therefore the interaction with the water must be taken into consideration in the design of the system. Although the results are only a preliminary step on the development of a device applicable to an actual petroleum submarine pipeline, it was observed that the PTMD does indeed suppress the vibrations, but it must be properly configured to achieve an optimum performance. The data gathered from this work will also be useful in the improvement of a numerical model of the pipe-PTMD system for use in a computer simulator.Copyright