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Analyzing Effects
of Architecture and Two-Phase Flow Properties of
Berg, S.S., E. Øian, N. Fredman, S.L. Semshaug, T. Skar, A. Braathen, University of Bergen, Bergen, Norway
Effects of faults on fluid flow are often difficult to predict.
Ranking of uncertainties associated with fault modeling is therefore a key
issue in the development of new workflows in the petroleum industry. The aim of
this contribution is first to consider possible flow effects of faults with
different architectures and two-phase flow properties, and secondly to illustrate
a framework for analyzing uncertainties associated with flow in faults.
Three theoretical scenarios of faults in a production setting
are considered: (1) Homogenous, strongly water wet faults, where injection of
water increases the sealing capacity. (2) Heterogeneous, water-wet faults where
less deformed rock bodies act as conduits to flow. (3) Homogenous, strongly
oil wet faults acting as barriers to flow of water. The scenarios are based on
qualitative measures for initial fluid saturations, permeability, capillary
pressure, and wetting properties, and illustrate how multi-phase flow
properties add to the general complexity of faults.
A numerical and
geological framework for analyzing relative effects of fault complexity and
multi-phase flow properties on fluid flow has been developed. The framework is
based on the hierarchical structure of faults and enables analyses of
structures on different scales. The scales are defined relative to the grid
cell sizes, and are represented by different upscaling
techniques. The framework is illustrated through a simple fault zone model with
a central fault core surrounded by subsidiary faults and deformation bands.
The hierarchical framework allows for comparison of upscaling
procedures as well as sensitivity analyses of structural features on different
scales and with different flow properties. It provides a tool for delimiting
the relative effects of structural uncertainty.