Sediment Provenance Study of the Lower Hamilton Group: An Analysis of the Organic-Rich Facies and its Depositional History

Abstract

Currently, insufficient geological models exist to explain the variability and distribution of TOC in the Marcellus Shale, within the Hamilton Group. TOC is one of the several limiting factors for natural gas production within the Marcellus Shale basin. One possible explanation for the low TOC regions is that detrital dilution was variable across the basin, with different sediment sources contributing detritus to low TOC areas, compared to surrounding regions with higher TOC. This hypothesis is tested by analyzing the source composition of inorganic detritus, using elemental and mineralogical proxies, with two cores in the Hamilton Group. The Armstrong #1 core is located in Taylor County, West Virginia and the Coldstream Affiliates 1MH (CSA) core is located in Clearfield County, Pennsylvania. Both these wells are located outside of the higher productivity regions with a nearby horizontal Armstrong well totaling 0.45 BCF/1000ft lateral and a nearby horizontal CSA well totaling 0.41 BCF/1000ft lateral. Variation in production may also result from over maturation of the kerogen-hosted pores. To evaluate the influence of thermal history, the thermal maturity of the Marcellus Shale in the lower productivity Armstrong #1 and CSA wells and the higher productivity MSEEL well was assessed using Raman spectroscopy. Major element, trace element, and REE geochemistry indicate the sediment source area was composed of intermediate and felsic granitic and recycled sedimentary lithologies. Samarium-neodymium isotopic analysis reveals a range of DM ages and εNd values. The Armstrong #1 well DM / εNd ranged from 1.64 to 1.91 Ga /-11.93 to-9.56 and the CSA from 1.62 to 1.88 Ga /-12.07 to-11.12. The εNd values became more negative upsection, however the DM did not display a consistent trend relative to depth. Provenance analysis indicates the most likely source of clastic sediment was the Acadian Fold-Thrust Belt to the east with minor inputs from Superior Craton and southern Canadian Grenville Province. Ultimately, results conclude that elevated TOC was associated with only older DM ages and recycled sedimentary signatures. iii TABLE OF CONTENTS