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Innovative Workflow for Fracture Characterization and its Utilization in Development of Naturally Fractured Carbonate Reservoirs: A Kuwait Case Study

Abstract

Kuwait Oil Company is currently appraising and developing subsalt deep fractured carbonate reservoirs of Oxfordian-Callovian-Toarcian age in the northern part of Kuwait. One of the critical success factors for optimal development of these challenging reservoirs is the ability to intersect open, connected fractures. However, these fracture corridors also pose risks during drilling (severe losses / stuck pipe) and production (early water break through). Over the past few years, variety of static and dynamic data sets such as Bore Hole Image logs (BHI), Conventional Cores, Core reorientation and customized Pressure Transient Analysis (PTA) is acquired. As part of the BHI interpretation, a concept of quality flag is introduced which takes care of the uncertainties due to data acquisition artifacts. The core data is also carefully analyzed through surface core reorientation. The quality flag and the core reorientation results are integrated, leading to a reliable interpretation of fractures. This integrated result is further validated through PLT/PTA data, leading to understanding of different types of fracture types i.e., open, partly open and closed. Next level of integration through seismic data is helping in understanding the inter-well space fracture population. 3D seismic data has also assisted in building the structural evolution models linked to regional structural tectonics / deformation phases. Through these customized workflows, fracture characterization in terms of different types of fractures like drilling induced and natural fractures; connected fracture network / fracture corridors are understood. This work flow also provides additional information on key fracture attributes like fracture porosity, permeability, mechanical stratigraphy and fracture genesis. A realistic production forecast, through nodal analysis, is obtained through application of this workflow for these challenging reservoirs. This robust fracture characterization is enabling development of these naturally fractured reservoirs through effective well planning of deviated / horizontal wells and enhancing the well delivery.