Modeling flow in naturally fractured reservoirs: effect of fracture aperture distribution on dominant sub-network for flow

J. Gong*, W. R. Rossen

*Corresponding author for this work

Research output: Contribution to journalArticleScientificpeer-review

43 Citations (Scopus)
57 Downloads (Pure)

Abstract

Fracture network connectivity and aperture (or conductivity) distribution are two crucial features controlling flow behavior of naturally fractured reservoirs. The effect of connectivity on flow properties is well documented. In this paper, however, we focus here on the influence of fracture aperture distribution. We model a two-dimensional fractured reservoir in which the matrix is impermeable and the fractures are well connected. The fractures obey a power-law length distribution, as observed in natural fracture networks. For the aperture distribution, since the information from subsurface fracture networks is limited, we test a number of cases: log-normal distributions (from narrow to broad), power-law distributions (from narrow to broad), and one case where the aperture is proportional to the fracture length. We find that even a well-connected fracture network can behave like a much sparser network when the aperture distribution is broad enough (α ≤ 2 for power-law aperture distributions and σ ≥ 0.4 for log-normal aperture distributions). Specifically, most fractures can be eliminated leaving the remaining dominant sub-network with 90% of the permeability of the original fracture network. We determine how broad the aperture distribution must be to approach this behavior and the dependence of the dominant sub-network on the parameters of the aperture distribution. We also explore whether one can identify the dominant sub-network without doing flow calculations.

Original languageEnglish
Pages (from-to)138-154
Number of pages17
JournalPetroleum Science
Volume14
Issue number1
DOIs
Publication statusPublished - 1 Feb 2017

Keywords

  • Effective permeability
  • Naturally fractured reservoir
  • Non-uniform flow
  • Percolation
  • Waterflood

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