A simple expression is derived for average fracture intersections per fracture, λ as the product of fracture density, average length and angular standard deviation for 2D and 3D cases. The calculated λ value quite accurately estimates the observed actual λ values for a variety of cases including one or two fracture sets, truncated or not-truncated fractures, and log normal or power length distribution. The validation is confined however only to 2D stochastic fracture models. The 3D equivalent formulae were not validated. The formula fails to estimate number of fracture intersections accurately when fractures are clustered. Fracture clusters could either be fault related fracture corridors or highly fractured layers. In either case, it is necessary to calculate λ for each fracture corridor or each fractured layer with different fracture density.

The relationship between λ and fracture connectivity and percolation were investigated using several stochastic fracture models. λ seems to be a reasonably good estimator of fracture connectivity, which we define as percent of fractures within the largest fracture cluster. The relationship between number of fracture intersections and percolation threshold is, however, weak because percolation threshold is dependent on the relative length of fractures with respect to the distance between two opposite ends of a fractured medium.

We tested the value of λ from borehole image data as a measure of fracture connectivity by comparing it with open hole log and production flow profile in an actual well. λ was calculated for highly fractured low porosity layers and found to be far below the values expected for fracture connectivity. Production log flow profile and open hole logs confirmed the result. There is no flow from the fractured low porosity layers, but all the flow is from a high matrix porosity / permeability layer with sparse or no fracturing. Open hole logs also show injection water encroachment only within the permeable matrix layer.

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