Modified analytical equations of recovery factor for radial flow systems

• This paper presents analytical algorithms to calculate ultimate recovery factors for radial flow systems.
• The proposed analytical model improves the prediction of reservoir performance, which has been applied/verified by a field case study.
• This method demonstrates higher water saturation in the near-wellbore region and consequently leads to a short period of water breakthrough process in peripheral waterflooding system.
• As a result, the radial algorithms tend to give a slightly higher recovery factor than the linear system approach.
• This new method is critical for field development plan in early stage and reserve evaluation practice.

Buckley–Leverett displacement equations have been derived strictly from linear flow systems, and have been verified by linear flow experiments only. This paper presents analytical algorithms to calculate recovery factors for radial flow systems, which is expected to be more accurate for peripheral water-flooding reservoirs.The proposed equations have been verified with field data. The original Buckley–Leverett equation generally results in much lower recovery factors that barely match the well cumulative production at interest. Consequently, the estimated ultimate recovery (EUR) by volumetric methods tends to be low. As a result, the production projection according to volumetric EUR is not reasonable in comparing to the historical performance. The proposed analytical model improves the prediction of reservoir performance.