Plasticity and Flow: A Continuum Description of Reservoir Response from Microseismicity

Abstract

Abstract

Hydraulic fracturing is process that perturbs the reservoir around the injection ports, creates a network of damage, and injects proppant into these fractures to promote permeability and drainage from the reservoir. Microseismicity has been successfully monitored from such programs on an industrial scale for over a decade, and has been challenged to answer these questions on how far and where proppant extends into the formation and what is the region of significant damage to provide estimates on how much hydrocarbon can be accessed after stimulation. However, the approach of considering microseismicity as point measures in space and time is not necessarily well-suited for describing the aggregate effects of the stimulation on the reservoir. Seismicity is a response to perturbations in the stress field and the relationships between different events reveal how these stresses are changing, necessitating a more statistical approach to link the observed microseismic emissions to the response of the reservoir to injection and the identification of variations in reservoir rock properties resulting from the injection program.

Our investigation showcases how macroscopic properties of the fracture system can be extracted through analysing the spatiotemporal growth of events and their properties within selected rock volumes. This is achieved by considering that disturbances in the rock and reservoir trigger inelastic deformation as stress and fluid transfer through the rockmass and that it can be encapsulated by a deformation index, here referred to as the Plasticity Index, representing the ease at which the reservoir deforms. Furthermore, the spatio-temporal variations in these stress transfer processes suggest that the deformation can be considered as flow (of the stress field). In other words, the characteristics of flow are mirrored in the seismicity and that large fluctuations in stress in the reservoir comprise turbulence in this flow. In this study we consider how turbulence in flow can compromise the uniformity of production along treatment wells and how the complexity of flow also relates to production levels along treatment wells.

AAPG Datapages/Search and Discovery Article #90260 © 2016 AAPG/SEG International Conference & Exhibition, Cancun, Mexico, September 6-9, 2016