Abstract
A new application of the Godunov scheme to describe dynamic oil-well behavior is presented. The numerical model is able to capture discontinuities associated with surface flow-rate variations. The finite volume method and Riemann problems are utilized for building the unsteady discrete solution. Initial and boundary conditions are related to cases of static, steady and transient well condition. Well data used in simulation are taken from true operational conditions and well mechanical configuration. The results of Godunov’s modeling describe the behavior of transient pressure and transient flow rate inside drill pipe and annulus. These profiles are commonly caused by turning on, adjusting mud flow rate and turning off the rig pumps. The evaluated rig indicators are: back pressure, pumping pressure, bottomhole pressure and injected flow rate. Calculated transient profiles are physically consistent and in good agreement with published well data. Therefore, engineering contribution is the application of first-order Godunov method to evaluate the transient hydraulics whereas variations of mud flow rate; also, the analysis and interpretation of the dynamic pressure behavior travelling inside the well. The Godunov scheme has robust engineering applications for modeling the transient drilling hydraulics, e.g., managed pressure drilling, hydraulics of pipe connections, and foam cementing, as well.
Highlights
Drilling hydraulics includes the cases of static, steady and transient wellbore conditions
At 0.1 s, 280 gpm are pumped by standpipe, the time spent by the pressure wave to travel along inside of the drill pipe and annulus is 7.3 s considering the wave velocity of 3281 ft/s; it means that the 280 gpm will be returning out to surface after 7.4 s
The numerical modeling of the wellbore drilling hydraulics was carried out applying the transient Godunov scheme considering variations of the injected flow rates
Summary
Drilling hydraulics includes the cases of static, steady and transient wellbore conditions. The resulting pressure and flow-rate profiles are plotted versus true vertical depth and length of simulation to depict how the discontinuities are travelling along the well They are widely validated together with hydraulics data of oil well drilling. This deals with the dynamic behavior of wellbore considering controlled flow-rate variations In drilling, this well condition is very common; i.e. when the driller is adjusting mud flow rate for better hole cleaning, during pipe connections or utilizing an automatic control of rig pumps; the driller mainly acts based on his field experience and well off-set data of previous interventions. The article section explains the math model and a Godunov discrete solution, the numerical results of transient hydraulics; the main conclusions are stated
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