Uncertainties of Defining Slanted Wells in Black Oil Simulation

It is very common for wells having a certain deviation angle to the formation plane. Such wells are called “slanted wells”. The productivity of slanted wells would increase due to an increase in reservoir to wellbore exposure. However, though drilling slanted wells is usual, a few studies of their performances exist.

Despite the fact that simulating a slanted well seems to be an easy task, it would face some uncertainties considered as the main reason behind this paper. This study has tried to show the sensitivity of black oil simulation results to well production rate and the resolution of local grids selected for modeling. For this purpose, the slant skin was calculated for simulation cases having different “Local Grid Refinement” resolution. The calculated slant skin by analytical work of Cinco et al. was taken as the basis to find a reasonable LGR system. The applicability of this optimum LGR for all deviation angles with comparison with Cinco model is evaluated. This evaluation shows that for each well deviation angle Optimum LGR is particular. Furthermore for black oil simulation a minimum production rate was found, up to which the calculated slant skin were thought to be rate dependent.