Well Log Clustering Analysis and Upscaling Procedure of the Tuscaloosa Marine Shale, Mississippi and Louisiana

Abstract

The Cretaceous Tuscaloosa Marine Shale is an important unconventional gas-shale reservoir located within the Interior Salt Basin in Louisiana and Mississippi. Recently, wells producing from the Shale have achieved initial production rates of over 1,000 barrels of oil equivalent per day. This study aims to determine the role of mineralogical variation in the development of natural fractures in different facies of the Shale by integrating mineralogical, core, and wireline log data within a study area extending west to east from Rapides Parish, Louisiana to Amite County Mississippi and north to south from Wilkinson County, Mississippi to East Feleciana County Mississippi. The software program GAMLS, a probabilistic well log clustering analysis is used to correlate well logs in over 70 wells throughout the region in order to understand heterogeneities in the Tuscaloosa Marine Shale and upscale organic porosity, mineralogical, and core data to the basin scale. Preliminary results have indicated that by utilizing the GAMLS well log clustering analysis, the formation can be divided into eight electro-lithofacies units (rock types). These lithofacies were correlated to variations in fracture density, fracture porosity, and production results throughout the study area. Core samples were taken from each of these eight lithofacies and the relative amounts of quartz, calcite, and clay minerals were correlated to fracture density. The mineralogy and fracture density of the shale is highly heterogeneous throughout the study area and as a result all eight lithofacies are not present in every well. A positive correlation was made between mineralogy, fracture density, and oil production, and mapped throughout the region. Physical characteristics of natural fractures (length and mineralization) as well their frequency are found to be related to variable lithofacies of target zones within the formation. These lithofacies were mapped throughout the region in order to better understand where alterations in the formation occur.

AAPG Datapages/Search and Discovery Article #90216 ©2015 AAPG Annual Convention and Exhibition, Denver, CO., May 31 - June 3, 2015