Improved Waterflooding - Analytical Screening of Cyclic Parameters

The cyclic injection improves water-flooding sweep efficiency in heterogeneous reservoirs. The IOR-method was applied in many fields in Russia, USA, China. Cyclic injection potential to improve water-flooding efficiency was clearly demonstrated in a number of projects. The uncertainty which exists with the cyclic water-flooding is related to understanding the IOR mechanism, ability to accurately model and predict efficiency of the process, design a field application. In this work we discuss and evaluate parameters that affect cyclic water-flooding. The algorithms and analytical tool were developed to model cyclic injection and fluid cross-flow between stratified reservoir layers. The model accounts for compressibility effects, gravity and capillarity forces. The screening results of cyclic injection in the North Sea heterogeneous sandstone reservoir are presented. A wide-range sensitivity analysis was performed to estimate the process efficiency. The analysis with respect to rock-fluid parameters, heterogeneity, cycle length and pressure conditions allowed to rank the critical factors by their influence and importance for achieving efficient cyclic process. Cyclic injection has significant IOR potential in stratified sandstone reservoirs with high permeability contrast. The method can improve water-flooding sweep, accelerate oil production and increase oil recovery by up to 11%.