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Abstract Firstly，according to the mechanism of rock damage of hydraulic fracturing for oil reservoir，considering the changes of matrix porosity and micro-cracks volumes after loading on rock，the tensor damage variable of rock damage is defined by using the changes of matrix porosity and microfracture volumes，and the rock damage deterioration model of hydraulic fracturing is obtained based on damage theory. Secondly，assuming the dynamic evolution of microfracture of the process of hydraulic fracturing satisfies with the Logistic fork standard model，the microfracture dynamic evolution model is established based on the damage theory and according to energy conservation principle of hydraulic fracturing，the internal relation among the volumetric strain，medium porosity and damage variable of the process of rock damage evolution is determined. Finally，the model of matrix porosity and the evolution of permeability tensor of Microfracture for hydraulic fracturing rock is established. Taking the well named 29–3，4 in Jilin oil field for example，the traditional method and the new one are implemented as modules into finite element software to simulate productivity to verify the advantage of new model. The comparison result shows that the new model is more suitable for practical situation.
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Received: 23 September 2008
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