--> Reservoir Characterization and Fracture Network Modeling of the Highly Fractured Dolomitized A-2 Carbonate (Silurian) Gas Storage Reservoirs in the Michigan Basin

AAPG ACE 2018

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Reservoir Characterization and Fracture Network Modeling of the Highly Fractured Dolomitized A-2 Carbonate (Silurian) Gas Storage Reservoirs in the Michigan Basin

Abstract

The Overisel and Salem fields of Southwest Michigan annually store upwards of 30 Bcf of natural gas in the upper dolomitized portion of the Silurian-aged, A-2 Carbonate formation (A-2C). Porosity and permeability in these fields has been enhanced by fracturing and dolomitization associated with the dissolution and collapse of underlying salt units. However, little is known about the depositional and diagenetic model for the A-2C on a field scale. This study aims to 1) present a high resolution depositional and diagenetic model for the A-2C, and 2) create a fracture network model for the Overisel and Salem fields. Cored intervals from 8 wells, gamma ray and neutron logs from 263 wells in the gas storage fields will be the primary dataset for characterization of the depositional and diagenetic model for the A-2C. Primary production and current gas storage operations data from these fields, along with petrophysical data and 12 newly acquired acoustic circumferential borehole image logs (CBIL) will serve as the basis of the fracture network model. CBIL logs will be used to observe rock properties as well as fracture density, orientation, aperture, length, and type. Statistical analysis of fracture data allows for the construction of representative discrete fracture networks to better understand connectivity and fluid flow characteristics of these fields. Conceptualization of a high-resolution depositional and diagenetic model paired with fracture analysis and petrophysical data will allow for the creation of a three-dimensional static reservoir model that will test uncertainties and better predict fluid pathways in the Overisel and Salem storage fields.