An application of the composite index method to the heterogeneity of fluvial reservoirs: An example from the 3⁴ reservoirs of the 2nd member of the Shahejie Formation in the 2nd district of the Shengtuo Oil Field

The present paper gives a detailed description of interstratal, intrastratal and planar heterogeneity and its main influencing factors in the fluvial reservoirs of the 3⁴ reservoirs in the 2nd member of the Shahejie Formation in the 2nd district of the Shengtuo Oil Field in the light of reservoir architectures and logging interpretation by using the entropy's method. The 3⁴ reservoirs are turned out to be moderate to highly nonhomogeneous, and become progressively higher with the increase of water injection. The planar heterogeneity tends to be higher than the interstratal and intrastratal ones. The reservoir heterogeneity is believed to be controlled by reservoir architectures, and more complicated by diagenesis. The different heterogeneity tends to caused by deficient injection and production patterns. The heterogeneity index based on the entropy's method may be important to characterizing the heterogeneity of the fluvial reservoirs and predicting the distribution of residual oil.