Coupling and Damping Effects on the Dynamics of Submerged Expanded Tubes in Borehole Wells

Hydraulic expansion of submerged tubes is accomplished by propelling a mandrel through it using differential pressure. This process deforms the tube beyond its elastic limit. Toward the end of the expansion process, the mandrel pops out of the tube resulting in displacement, stress, and pressure waves propagating through the system. A mathematical model has been developed to describe the dynamics of the tube-fluid system due to the pop-out phenomenon. The model takes into consideration the coupling effect between fluids and the structure, as well as the inherent system damping of its response. An analytical solution describing the wave propagation in the tube-fluid system was obtained. The model identified the potential failure locations and showed that the inherent system damping reduced the chances of failure but could not eliminate it completely. In addition, it showed that the coupling effect was more prominent in the tube as compared to the outer and inner fluids. Furthermore, a sensitivity analysis was conducted in order to investigate the effect of the geometrical and material properties on the response. The sensitivity analysis showed that the coupling effect vanished with the increase in tube stiffness and reached an asymptotic value with an increase in formation stiffness

Dynamic Analysis and Vibration of Beam Inside Annulus for Ultra Short-Radius Water Jet Drilling

Conventional water-jet nozzle systems have been developed and partially used in the oil and gas industry to drill horizontal sidetracks. However, this technique still presents a few shortcomings associated with tube buckling and water jet sagging. Due to these problems, the drilled hole deviates from the desired path and does not reach the target reservoir. The issue becomes more complex due to the continuously moving boundaries representing the borehole profile, which is, in turn, governed by the nozzle dynamics. A mathematical model representing the dynamics of water jet drilling confined in a borehole along with drilling mud is developed to predict the sagging phenomenon during the drilling process. The closed form solution of the governing equation is obtained for horizontal drilling in shallow formation layers. The solution shows the strong influence of nozzle vibration and the magnitude of thrust force at the nozzle tip on the profile and the diameter of drilled hole. For sidetrack drilling of greater than 400 m length, the magnitude of sagging is large enough to miss the target reservoir. Furthermore, the dril string buckles at certain magnitudes of thrust forces and penetration lengths

Modelling of multicomponent reactive transport in finite columns — Application to gold recovery using iodide ligands

Existing semi-analytical solutions to the problem of reactive transport in porous media are either restricted to single aqueous species, to decoupled processes or to infinite/semi-infinite domains. Our approach addresses the problem of multicomponent reactive transport in finite columns, where coupling feedbacks emanating from the non-equilibrium thermodynamics of chemical species are taken into account. The main purpose of this research work is to investigate the in-situ leaching of precious metals—a technique that is expected to be relevant to the Earth's regolith consisting of fragmented and/or weathered rocks where permeability is sufficiently high for reactive transport. Producing precious metals from such areas may be beneficial especially when the grade is too low for conventional mining techniques to be applicable. The proposed solution method is validated experimentally using existing tests of column leaching using iodine-based lixiviants. The obtained results show good agreement with the experimental data. In addition, the results indicate that the rate of effluent gold concentration increases until its maximum when the flow velocity, concentration of iodine lixiviants, or specific surfac e increase. After the peak, the behaviour is more complex and the obtained results allow to optimise the amount of recovered gold

Improved impact-echo approach for non-destructive testing and evaluation

This study examines rationale of correction factor β in the formula of thickness resonant frequency, fundamental to the impact-echo (IE) approach in non-destructive testing and evaluation for integrity appraisal and damage diagnosis of infrastructure systems. It shows the role of the factor in the resonant frequency which is typically obtained with average characteristic from traditional fast Fourier transform or FFT data analysis of IE recordings. A time-frequency data analysis termed Hilbert-Huang Transform or HHT is then introduced to overcome the shortage of FFT analysis in identifying the resonant frequency from IE recordings. With the FFT and HHT analyses of five data sets of sample IE recordings from sound and damaged concrete structures and comparison with referenced ones, this study reveals that the proposed IE approach with HHT data analysis not only eliminates the use of correction factor in the formula, it also improves greatly the accuracy in the IE approach