The inflow performance relationship (IPR) developed through numerical simulation of vertical, horizontal, and slant wells in solution-gas drive reservoirs was analyzed. The IPR is essential to optimize production design; however, little information is available for interpreting the change of IPR with wellbore geometry and depletion stages. Gas saturation, PVT properties, and formation pressure close to a wellbore were investigated to interpret the shape of IPR curves at various flowing bottomhole pressures and stages of depletion. The effect of oil gravities on IPR curves was studied, and newly developed IPR curves for slant wells were compared to those for horizontal and vertical wells.
Horizontal well IPR curves fall on both sides of Vogel’s reference IPR curve for a vertical well. Horizontal wells show a better productivity improvement with additional pressure drawdown than vertical wells at the early stage of depletion. Horizontal well IPR curves increase their curvature with depletion up to 8% then slightly decrease in curvature at later stages of oil recovery. This trend, different than that found for vertical wells, is due to a high gas production rate from horizontal wells at low bottomhole pressures before oil recovery reaches 8%. The decrease in curvature of IPR curves for a vertical well with depletion is due to a slightly higher formation pressure around the wellbore at lower flowing bottomhole pressures at later stages of depletion.