The wide range in geological complexity encountered in fractured carbonate reservoirs requires the combination of several elements to optimize their development: a favorable structural position for drilling needs to be paired with the understanding of the fluid connectivity pathways affecting its location. In addition, the well placement criteria will vary depending on the stage of maturity of the field. This work aims to summarize key observations acquired by the authors during over a decade of field development experience in faulted and fractured carbonate oil reservoirs in the Zagros Fold and Thrust Belt in the Kurdistan Region of Iraq.

The methodology of this work includes the analysis of different fracture types and their context of occurrence with respect to well behaviors during drilling, production and surveillance stages. These correlations are based on the authors’ observations from a number of producing oil fields where vertical and horizontal wells in deformed sections provided insights to the wide spectrum of geological features and their hierarchical range in flow potential. Commonalities observed from these fields are presented in this paper in a generic fashion covering multi-scale data sets.

The work summarizes the understanding of the diverse fracture networks and their dynamic behavior along with key remarks on optimizing well placement criteria and completion strategies according to the maturity of the field and, ultimately, to improve the field development strategy. Outcrop examples are used to introduce the array of fracture categories encountered in subsurface and to guide the discussion on the dimension of scale and their spatial relationship relative to each other as contributors to reservoir plumbing systems and observed reservoir dynamics. As a result of this analysis, the challenges related to fractured and faulted carbonate fields such as water breakthrough scenarios, cumulative rise in water production and underperforming reservoir sections are addressed.

This paper therefore intends to contribute to the discussion on development strategies, definition, and selection of drilling targets and well design applied in fractured and faulted carbonate reservoirs by utilizing observations from different reservoir types in the Kurdistan Region of Iraq.

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