25th January 2018

Carbonate Reservoirs of the Middle East and Their Future Challenges

Badley Ashton's Dr. Matthieu Deville de Periere will be in attendance at the AAPG Middle East's three day workshop on the Carbonate Reservoirs of the Middle East and their Future Challenges. This event runs at the Crowne Plaza Hotel in Abu Dhabi from Tuesday the 30th of January until Thursday the 1st of February.

This three-day workshop builds on the success of the first AAPG Carbonate Reservoirs of the Middle East GTW, held in Abu Dhabi, UAE in 2015. It is dedicated to addressing the hydrocarbon bearing carbonate reservoirs of the Middle East, in the context of a changing oil market within a more challenging exploration and development environment. These challenges include the shift from traditional anticlinal traps to stratigraphic traps, and development strategies for dealing with maturing, long-producing, giant fields.

The key objective is to gather oil industry experts from different disciplines, (geology, geophysics, petrophysics and reservoir engineering), to share their knowledge and experience. Case studies, which range from field-scale reservoir heterogeneities to regional-scale depositional system evolutions and shifting sequence stratigraphic elements will be used to stimulate discussion around best practices for the Middle East's numerous carbonate reservoirs.

The workshop will consist of 2 days comprised of presentations, poster sessions and core displays, followed by a third day offering optional field trips to either the Abu Dhabi Sabkha, or the tertiary outcrops of Jebel Hafit.

Matthieu will be presenting on Wednesday afternoon on The Link between microporous limestones and elastic properties in tight carbonates. A case study from the Lower Arab Formation (Upper Jurassic), onshore UAE; work that has been undertaken with our clients from ADNOC Sour Gas. The abstract from his presentation is given below. Don't forget to come along and say hello to Matthieu who will be very happy to discuss his presentation as well as discuss Badley Ashton's services and how we may be able to help you.

Link between microporous limestones and elastic properties in tight carbonates. A case study from the Lower Arab Formation (Upper Jurassic), onshore United Arab Emirates.

Matthieu Deville de Periere, Alexander Foote, Meriem Bertouche, Badley Ashton and Associates Ltd.

Razza Shah, Fatima al-Darmaki, Wala bin Ishaq, ADNOC Sour Gas.

The Lower Arab D Member (Kimmeridgian) in onshore UAE is typically characterised by a thick succession of homogeneous mudstones with local cm-scale interbedded bivalve-rich floatstones, which are thought to have been deposited in a low-energy mid-ramp setting. This sedimentological unit is located at the base of a sour gas reservoir that includes the oolitic grainstones of the Upper Arab D Member.

The pore system in these micritic deposits is dominated by matrix-hosted microporosity, along with open to partially cemented fractures, primary intraparticle macropores and rare biomoulds in the shell beds, hence a poor to very good porosity and extremely poor to rarely excellent permeability. Variations in porosity and permeability values appear to be strongly related to variations in the micritic fabric: both porosity and permeability increase when the micritic fabric evolves from anhedral compact with coalescent intercrystalline contacts (associated with very little and poorly connected micropores) to subrounded with facial to subpunctic intercrystalline contacts (with locally well-developed micropores). Micritic fabrics also clearly impact the elastic properties of the rock. Through analysis of elastic moduli calculated from standard density, and shear/compressional sonic wireline logs, the relationship between micritic fabric, porosity, permeability and geomechanical properties has been explored. With the evolution of micritic fabric from anhedral compact to subrounded, Young's Modulus decreases with increasing porosity and permeability, indicating a decrease in the overall stiffness of the mudstones. The implication of this observation is fundamental for the development of natural fractures within the Arab D, which are used as conduits for the vertical fluid flow. Indeed, stylolites with associated partially cemented tension gashes are commonly observed at the rheological boundaries, providing further secondary macroporosity and permeability anisotropy within the reservoir.

In this study, the observed link between micritic fabrics, log-derived porosity and elastic moduli within cored intervals has been used to predict micron-scale micritic fabric distribution in uncored wells from wireline logs only.

Key words: limestones, microporosity, elastic moduli, Young's Modulus

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