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Finite element analysis of fluid induced fracture behaviour in oilsand

University of British Columbia

In-situ recovery of oil from Oilsand deposits at depth, rely on fluid induced fracturing of Oilsand. A method of analysis for predicting the initiation and propagation of fractures in Oilsand has been developed. The prediction of fracture initiation involves a stress analysis of the domain. Analysis of fracture propagation requires a coupled stress and flow analysis'. In the method proposed herein, the stress and flow analyses are first considered as two separate analyses that are later coupled through volume compatibility. For the fluid flow analysis, the fractures are approximated as parabolic in shape. Fracture propagation has been analyzed incrementally, the direction of propagation being perpendicular to the computed minor principal stress direction at the tip of the fracture. The results are in good agreement with both laboratory and field experience. The results indicate that the presence of a propagating fracture causes significant changes in both the magnitude and orientation of the minor principal stress, at the tip of the fracture. As a result, a path of propagation that is significantly different from the initial in-situ minor principal stress plane direction has been observed. The rate of pumping of fluid, is an important factor in predicting the propagation behaviour of fractures in Oilsand. In fracture operations carried out at shallow depths, that involve high rates of pumping, the fractures must be dominantly horizontal in orientation. This is a result of the increase in fluid carrying capacity of the horizontal fractures, observed with propagation.

Text

2010-04-22

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http://hdl.handle.net/2429/24056

Civil Engineering

University of British Columbia

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