Jacobs Journal of Petroleum and Natural Gas

Variations in Gas Content in Organic Matter-Rich Low Maturity Shale; Example from the New Albany Shale in the Illinois Basin

*Maria Mastalerz
Department Of Geological Engineering, Indiana University, Bloomington, United States

*Corresponding Author:
Maria Mastalerz
Department Of Geological Engineering, Indiana University, Bloomington, United States
Email:mmastale@indiana.edu

Published on: 2018-08-18

Abstract

This paper investigates controls on gas content in the Upper Devonian to Lower Mississippian New Albany Shale, specifically addressing the influence of organic matter content and porosity on the desorbed and residual gas contents. The shale samples studied come from Daviess County, Indiana, where the entire New Albany Shale thickness of 40 m (~120 ft) was cored. Gas content was measured by canister desorption and volumetric displacement apparatus, and porosimetric techniques included He adsorption (total porosity) and low-pressure N2 (mesopore characteristics) and CO2 (micropore characteristics) adsorption techniques. Other techniques included organic petrographic analysis, TOC and S analysis, and SEM. Total porosity of the shales ranges from 2.9 to 10.3%, BET surface area from 4.1 to 9.1 m2/g, BJH mesopore volume 0.0125 to 0.0243cm3/g, and micropore volume 0.0080 to 0.0197cm3/g. Our data demonstrate that organic matter content is a good predictor of gas content, and micropores present in organic matter are the main storage sites not only for residual but also desorbed gas. The role of larger pores in gas storage in these shales is limited.

Keywords

Shale; Desorbed Gas; Residual Gas; New Albany Shale

Introduction

The New Albany Shale (NAS) in the Illinois Basin is a Middle and Upper Devonian to Lower Mississippian unit, correlative with the Antrim Shale of the Michigan Basin and the Ohio Shale of the Appalachian Basin. These shale units are thought to be part of an epicontinental succession deposited in response to a sea-level rise over large areas of the North American craton. In Indiana, the NAS is underlain unconformably by Middle Devonian North Vernon Limestone and is lithostratigraphically subdivided into the following six member units in succession from the oldest to the youngest: the Blocher Member, the Selmier Member, the Morgan Trail Member, the Camp Run Member, the Clegg Creek Member, and the Ellsworth Member. In most of Indiana, the NAS is overlain by the Rockford Limestone.