Integrating Mineralogy, Process Sedimentology and Geomechanics for Development of a Mechanical Stratigraphy Model of the Bakken Formation

Abstract

Mechanical stratigraphy, as defined by Laubach et al. in 2009 is “the by-product of depositional composition and structure, and chemical and mechanical changes superimposed on rock composition, texture and interfaces after deposition.” Understanding the mechanical stratigraphy of reservoirs is crucial for optimizing hydraulic fracturing completion designs, well targeting, and well bore stability. Many mechanical stratigraphy models are built on a single parameter such as rock strength, minimum horizontal stress, or brittleness. Mechanical stratigraphy, however, is likely to be controlled by factors such as mineralogy, rock fabric and process sedimentology. By integrating these parameters, this study develops a robust mechanical stratigraphy model to define mechanically distinct stratigraphic units that can then be used as an input to hydraulic fracture simulations. A comprehensive set of core measurements and log data has been collected from a vertical and horizontal core from the prolific, oil producing Bakken formation of the Williston Basin. The horizontal core allows for the incorporation of lateral heterogeneity data into the model which is typically absent, or not considered. By integrating sedimentological observations of these cores with measures of mineralogy and geomechanical properties, we have developed a quantitative model that identifies relationships amongst these parameters. Statistical tools were used to quantitatively group packages of rock that are expected to behave mechanically similarly, based on the raw data collected. Ultimately, the methodology developed in defining the relationships established by this model can be applied or extrapolated to other plays, both conventional and unconventional, where understanding fracture geometry is important for production.

AAPG Datapages/Search and Discovery Article #90291 ©2017 AAPG Annual Convention and Exhibition, Houston, Texas, April 2-5, 2017