Integration of Borehole Image Analysis, Open Hole Logs and Core Data to Unlock Stratigraphic & Sedimentological Analysis of a South Eastern Algeria Field.

Abstract

Abstract The identification of the depositional environment is critical to the delineation and prediction of the best quality reservoir. It often starts with a detailed core description, which is based on number of features. Borehole image augments the core data by providing important information for orienting features, filling in gaps between cores, recognizing sedimentary structures and sorting for facies analysis and identifying depositional environments. Oil-Based Micro-resistivity Images and Ultra-sonic Borehole Images were successfully applied to reservoir modeling by introducing a statistically correct model that obeys facies association rules and facies contacts and improves the dynamic history match. The principal hydrocarbon reservoir of field-A in the South Eastern Algeria basin, TAGI, is part of a fluvial system. The microfacies were analyzed with a pseudo-grain size profile and textural analysis of the borehole resistivity and ultrasonic images. The TAGI sits unconformably on the Paleozoic rocks, it consists of variable sequences which have been sub-divided into four fluviatile cycles. The depositional environments are mainly amalgamated channels passing laterally to flood plain, crevasse splay and sheet flood deposits. The correlation of the cycles combined with empirical functions enabled estimating the geometry of the sandstone bodied for each deposition element. This is required input for object modeling. This study showed the value of borehole image logs in sedimentology analysis, which progressed from single-well borehole image interpretation to conceptual model construction and channel dimension estimation.