Role of the Cluster Analysis in Logfacies and Depositional Environments Recognition from Well Log Response for Mishrif Formation in Southeast Iraq.

The recognition of depositional environments from well logs is based on the principle that well log responses are related to changes in thickness, texture, grain size and lithology along the well path. The variations in sedimentary rock response are due to reservoir heterogeneity. A similar set of log responses that characterizes a specific rock type and allows it to be distinguished from others, have defined an electrofacies.Cluster analysis includes a broad suite of techniques designed to find groups of similar items within a data set. Partitioning methods divide the data set into a number of groups predesignated by the user. Hierarchical cluster methods produce a hierarchy of clusters from small clusters of very similar items to large clusters that include more dissimilar items. Hierarchical methods usually produce a graphical output known as a dendrogram or tree that shows this hierarchical clustering structure.The method has tested on a 398.5 m thick interval of Carbonate deposits in a vertical well from Amara field, located in southeast Iraq. Modal data have collected from both core and cutting samples. Cluster analysis and electrofacies classification have performed using advance interpretation in Interactive Petrophysics software version 3.6.Carbonate microfacies and marine depositional environments studied for Mishrif Formation depended on the available thin sections though they were not enough to cover all the depositional environments of Mishrif Formation. Therefore, previous studies and well logs were also depended in this study.Correlation of determined logfacies with those defined from cores and cuttings is fundamental to check the reliability of used methods and to define a meaningful cut off level for wells from which no cores or cuttings are available