Macroscopic and Microscopic Lithologic Controls on Mechanical Properties of Mudstones

Abstract

The performance of unconventional mudstone reservoirs is in large part a function of the mechanical properties of the mudstone. Mechanical properties (yield and failure strength, nonlinear elasticity, anisotropy, etc.) are controlled by a variety of geologic variables, including detrital and authigenic mineralogy including cements, organic content, and the spatial distribution of these characteristics (i.e., heterogeneity). We are investigating impact of these lithologic controls across a wide range of scales for a common lithofacies of Cretaceous Mancos Shale. We map lithologic characteristics at different scales using a variety of techniques. Mudstone core samples are first subdivided into principal macroscopic lithofacies. Samples of the macroscopic lithofacies were further characterized petrographically, and microscopic facies identified using laser confocal microscopy to map the abundance, size, and spatial distribution of porosity, kerogen, and mineralogy. Mudstone mechanical properties were measured at a range of scales, including seismic wave velocity (Vp, Vs) and creep data for cm-sized samples, and nanoindentation measurements of focused ion-beam milled pillars. Our goal is to allow more accurate prediction of reservoir performance by developing a multi-scale understanding of mudstone response to reservoir stimulation efforts.

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