Exploration and production geology challenges of the Zagros Mountain region
The Zagros Mountains offer the potential of an abundance of oil and gas exploration and production opportunities, despite misconceptions held by some petroleum geologists. The truth is not all plays have been tested, petroleum systems are not well understood, stratigraphic units are not uniform, etc. More robust methods, like sequence stratigraphy, as opposed to simplistic lithostratigraphy, would produce a more accurate visualization of facies variation in these complex Permian – Miocene depositional systems. Other parameters worth examining to better exploit remaining resources are porosity and permeability, as well as mechanical stratigraphy. Looking to the surrounding area, Abadan Plain, Southwest of Zagros, holds charge potential for light crude recovery from Early Cretaceous rocks. It turns out there is potential for new play concepts, after all.
AAPG 2017 International Conference & Exhibition, London
This year’s AAPG International Conference & Exhibition will take place from 15th October to 18th October in London, UK, during which M.D. Simmons (Halliburton Technology Fellow) will present on: Examining Some Exploration and Production Myths in the Zagros.
Abstract: The Zagros Mountains hold an abiding fascination for petroleum geologists, yet there are many misconceptions regarding the exploration and production geology challenges of the region. For example, very often the stratigraphy is regarded as being layer cake; stratigraphic units are uniform in character, especially at the field scale; most reservoirs are tight and fractured carbonates; petroleum systems are well understood; and all the play ideas have been tested. We would argue that simple adherence to these concepts is unwise and inevitably leads to incomplete evaluation of exploration and production opportunities.
The majority of petroleum system elements were deposited during Permian – Miocene times on the epeiric margin of Neo-Tethys. As such, the depositional systems evolved in response to relative sea-level change and typically show marked progradation and retrogradation and consequently marked facies variation, particularly at the scale of the huge fields present. Such variation is not captured in simplistic lithostratigraphy and requires a sequence stratigraphic approach to visualize correctly. As well as the implications for development strategies, such depositional systems hold the potential for untested stratigraphic trapping, especially in under-researched lowstand plays (both clastics and carbonates).
Whilst fracturing is often an important reservoir quality control, primary depositional fabrics are important and show porosity and permeability variations tied to sequence stratigraphic organization. Furthermore, mechanical stratigraphy and sequence stratigraphy appear to be linked.
In large parts of the Zagros, oils are typically heavy and biodegraded. Light oils low in sulphur would have a greater value if they could be located. An Early Cretaceous petroleum system may offer such promise, as there are a group of oils that have characteristics very different to those generated by Jurassic, Mid-Cretaceous and Tertiary source rocks. Basin modelling suggests that Early Cretaceous rocks may have charge potential in the Abadan Plain region and generate light crude.
New play concepts include stratigraphic traps (for example, onlap to emergent highs at key mega-sequence boundaries); subcrop at the base Triassic; and lowstand carbonate shelves and lowstand clastic deltas and fans. Erosion and channeling at key sequence boundaries support these lowstand play concepts.
This is one of a series of technical presentations, which will be delivered by Halliburton experts at the AAPG International Conference & Exhibition, London event on 15-18 October 2017. The full details of the event and agenda can be found here.
Join us to learn about key geological challenges facing exploration and the latest developments to optimize production.