Evaluation of continuous surfactant flooding in north east Africa: Case study of bentiu reservoir

Recently, continuous surfactant flooding (CSF) has been devised as an improvement to overcome the limitation of conventional surfactant flooding (SF). The utilization of CSF depends on several factors such as surfactant type and reservoir characteristics. This study performs the feasibility study of utilizing CSF for a marginal field of Bentiu reservoir in Sudan with a production history of 20 years. The reservoir is moderately heterogeneous reservoir. Thirty-six (36) cores from the natural reservoir extension of its most effective basin were evaluated. The evaluation focused on the role of core properties such as porosity and permeability on CSF. The comparison of the results was benchmarked by water flooding and the conventional surfactant flooding. Numerical simulation CMG STARS was used to perform the sensitivity analysis on the core scale. The results of the study showed 5 main ranges of the cores available after grouping. The highest recovery factor of water flooding was in the range of 48 (+/- 1.3%). There were no significant changes in the cumulative oil produced; however, the core physical properties affected the duration needed to reach the production plateau. For CSF, the highest recovery was in the fourth group of cores. In term of water cut, the percentages declined slightly with a range of 0.01 to 0.09 % with lowest percentage value water cut recorded at 99.90% and the highest result of 99.99%. Moreover, the recovery factor reached up to 45.80% using water flooding method and increased up to 90.41 % in CSF method. The remaining oil saturation reached to 0.35 during water flooding and dropped to 0.061 during the CSF. Moreover, the result obtained in CSF which indicates that the optimum porosity and permeability range of 0.26 to 0.29 in porosity and 390 to 2220 mD in permeability is the suitable range to be implemented in continuous surfactant application. Hence, based on the obtained results, CSF shows promising effects for use in marginal oil fields.