Abstract

This paper presents a study on the impact of reservoir characteristics such as matrix porosity, matrix permeability, initial reservoir pressure and pay thickness as well as the length and the orientation of horizontal wells on gas production in New Albany Shale.

The study was conducted using a publicly available numerical model, specifically developed to simulate gas production from naturally fractured reservoirs. Reasons for selecting a non-commercial simulator for this study were two folds. First, we wanted to make sure that our results, discussions, and conclusions are accessible and repeatable by all interested operators and individuals that are currently producing or plan to produce from New Albany Shale since the simulator we used is readily available. Secondly, we wanted to demonstrate the utility and ease of use of this publicly available simulation software.

The study focuses on several New Albany Shale wells in Western Kentucky. Production from these wells is analyzed and history matched. During the history matching process, natural fracture length, density and orientations as well as fracture bedding of the New Albany Shale are modeled using information found in the literature and outcrops and by performing sensitivity analysis on key reservoir and fracture parameters.

Sensitivity analyses are performed to identify the impact of reservoir characteristics and natural fracture aperture, density and length on gas production. Economic analyses are performed to identify and rank the impact of the above parameters on the Net Present Value of investing on gas wells producing from New Albany Shale.

Introduction

New Albany Shale Gas -The New Albany Shale is predominantly an organic-rich brownish-black and grayish-black shale that is present in the subsurface throughout the Illinois Basin. The total gas content of the New Albany Shale (Devonian and Mississippian) in the Illinois Basin has been estimated to be 86 trillion cubic feet (TCF) (1). Although the New Albany Shale has produced commercial quantities of gas for more than 100 years from many fields in southern Indiana and western Kentucky, only a small fraction of its potential has been realized (2)

The Shale is shallow, biogenic and thermogenic that lie at depth of 600–5,000 feet and are 100–200+ feet thick. Natural fractures are believed to provide the effective reservoirs permeability in these zones and gas is stored both as free gas in fractures and as absorbed gas on kerogen and clay surfaces. (3)

The lack of dense natural fractures does not eliminate the potential for an economic fracture play in the New Albany.

The New Albany Shale has great potential for natural gas reserves. Gas-in-place (GIP) measures from 8 bcfg/square mile to 20 or more bcfg/square mile, depending on locations and depths.

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