Using Image Logs to Identify Facies in Heterogeneous Turbidite and Basinal Organic Mudstone Systems From the Wolfcamp Formation, Delaware Basin, West Texas, USA

Abstract

Integration of core facies, image log facies (ILF) and wireline logs from heterogeneous turbidite and basinal organic mudstone systems, increases the confidence levels for the database for building regional scale depositional models. Image logs provide a key link to characterize facies and processes in comparison to wireline logs, and can also be used to bridge the correlation between core facies and wireline logs for up-scaling. Systematic use of ILF as part of the correlation increases the data set for facies interpretation, as there is greater availability of image logs compared to core. This presentation details a method that uses borehole image logs to extend core-based facies and process analysis to intervals that lack core, in above mentioned sedimentary systems. The method is successfully used in a workflow that distinguishes carbonate, quartz, mud-rich turbidites and debris flows deposited with organic-rich silicic mudstones in an unconventional play of the Delaware basin. When using this method, electrode data from each pad of the micro-resistivity imaging tool (in water-based mud) is mathematically shifted to generate synthetic micro-resistivity logs that follow the trend of the shallow resistivity logs. The high resolution electrical data that best represents the sedimentary facies either derived from a single pad, or the averages from multiple pads of the imaging tool is selected. Next, the high resolution electrical data and detailed sedimentary textures visible from the image logs are used to identify the ILF and in turn calibrated with core facies. Caution is taken while using electrical data for facies identification as those can be severely affected by pore fluid properties. In the current effort triple-combo logs are considered for identifying broad lithological variation and ILF for more detailed characterization. The results show that of the 10 detailed core facies from cored intervals of mud-dominated turbidite sequences from lower and middle part of Wolfcamp Formation, 6 can be identified from the image logs. Within the sand-dominated turbidite sequence from upper most part of Wolfcamp Formation, 3 different ILF are identified out of 4 core facies. 4 different types of sedimentary processes are also identified from the image logs. Finally the ILF are successfully extended to identify the sedimentary facies and processes of Wolfcamp Formation over those imaged intervals that lack core in a specific well and also in the nearby wells.

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