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Unconventional Carbonate Reservoir Characterization Using Sonic Velocity and Characterization of Pore Architecture: an Example from the Mid-Continent Mississippian Limestone

Beth Vanden Berg
Boone Pickens School of Geology, Oklahoma State University, Stillwater, OK, USA
[email protected]

Abstract

The Mid-Continent Mississippian Limestone is an unconventional carbonate reservoir with a complex depositional and diagenetic history. Oil and gas have been produced from vertical wells for over 50 years, but recent horizontal activity in low porosity, low permeability zones makes it crucial to understand the petrophysical characteristics to target producing intervals.

The objective of my project is to test whether the relationship between sonic velocity, pore architecture and permeability in carbonates dominated by macro-pore systems is consistent with rocks containing pores at the micro- to nano-scale. Confirming this relationship would enhance the predictability of porosity and permeability trends in fine-grained, low porosity, low permeability carbonates.

Additional sonic velocity response in fine grain carbonates will be measured using core plugs taken from 4 cores in north-central Oklahoma and 2 outcrops in Missouri and Arkansas. Samples are selected based on the greatest difference in porosity for a given permeability, and permeability for a given porosity, so primary controlling features can be identified. Thin sections and samples from the same intervals are analyzed using a petrographic microscope and scanning electron microscope (SEM) to identify the primary and secondary pore types (moldic, intercrystalline), and quantify the pore architecture (pore shape and size). A sub-set of samples will have argon milling performed in 5-10μm increments and viewed sequentially using the SEM to examine the micro- to picoscale pore architecture in 3-D. High resolution 3-D CT scans will also be performed on a sub-set of samples to view the macro- to picoscale 3-D pore architecture and connectivity of pores.

AAPG Search and Discovery Article #90199 © 2014 AAPG Foundation 2014 Grants-in-Aid Projects