A possible solution for this problem would be to move the suction point higher up in the well, which would reduce the height of the fluid column above.This fluid column was found to be the main contributor to the negative friction effect.This might cause problems in studying this particular simulation case as it mostly relies on pressure control based on manipulations of the hydrostatic pressure component.
Nevertheless, it is important to test the experimental set-up with the proposed method first to be able to assess its efficiency.
The simulation results found that the model is extremely friction dominated, a very important conclusion in this case.
In the end, setting the outlet pressure flux equal to 1 atm was concluded to be the best alternative.
The scheme was available in two versions, 1st order and 2nd order.
Two methods for achieving stable numerical solutions were found.
Since the pressures delivered by the approximated small-scale model were very low, the first method involved pressurizing the system with 10 bars.Special focus was placed on the numerical boundary treatment on top of the well.Several ways of defining the outlet pressure boundary were investigated.One of the breaking innovations with CML is early kick detection, which allows determining the reservoir influx in less than a minute.Well Control procedures used for the CML are close to Driller’s method.However, an alternative method was found by editing a specific pressure condition in the code, which was there initially to assure stability but in this set-up was causing a problem.Both methods were compared and the alternative method was concluded to be the best out of the two.The updated 2nd order scheme differs from the original 1st order scheme by using slope limiters.This reduces numerical diffusion, which is a common problem with numerical schemes.Due to an increased demand from operator companies for deep-water drilling solutions, an interest in Dual Gradient technologies has risen.An example of such a technology is Controlled Mud Level (CML) drilling, where a subsea pump integrated in one of the riser joints actively controls the riser level.