The use of dynamic method to determine hydrocarbon in-place volumes in R5000 reservoir in Urad field became necessary when it was discovered that the in-place volumes estimated in previous studies for this reservoir cannot be validated by current production data. A combination of Buckley Leverett and Decline Curve Analysis has been used to significantly reduce the wide range of uncertainty reflected in previous in place volumes estimation.
R5000 reservoir in Urad field has two producing wells, one closed-in well and two planned wells; from production data review, it was discovered that estimated in-place volumes was less than optimum. The challenge of re-evaluation to obtain result that both structural interpretation and production performance data will support arose. This paper therefore has deployed Buckley Leverett method with assumption of moderate water drive and gravity drainage to approximate a water flood and as such predict recovery efficiency using the interaction between fluid mobilities, fractional flow and water saturation. Decline curve analysis performed on the producing wells in R5000 reservoir was used to derive technical Ultimate Recovery and a reverse calculation has been done to estimate hydrocarbon initially in-place that supports structure and production data.
The recovery factors of three reservoirs in Urad field, namely P1000, H2000 and K3000 have been previously estimated in an earlier study on this field using Buckley Leverett method and result obtained in this work was validated by repeating the BL evaluation for these three reservoirs to reproduce the recovery factor results obtained in earlier study.
This work provides a solution to the challenge of estimating hydrocarbon initially in-place volumes in reservoirs where available rock and fluid data as well as fluid contacts information are not reliable.