Effect of proppant distribution pattern on fracture conductivity and permeability in channel fracturing

Channel fracturing generally refers to a kind of novel hydraulic fracturing treatment that relies on the intermittent pumping of proppant-laden and proppant-free fluid to generate highly conductive channels within the formation. The fracture conductivity within the proppant pillar can increase up to several folds. However, how to effectively evaluate the fracture conductivity in channel fracturing is a tough problem. Unlike conventional fracturing, there are two distinct conductive media within the fracture: proppant pack and free channel. This paper analyzes the special proppant distribution pattern of channel fracturing, and the expression of fracture permeability is derived. On the basis of Hertz contact theory and geometry of proppant embedment, the expression of fracture opening is obtained. Then the effects of proppant distribution density and proppant pillar radius on fracture conductivity are analyzed. In the subsequent chapter, the correlation between proppant pillar permeability and free channel permeability is provided. The results show that the fracture conductivity increases at first and then decreases rapidly with the increase in proppant distribution density. The conductivity factor reaches its maximum value when vertical pillar spacing is equal to horizontal spacing. The more regular the shape of the proppant pillar is, the greater the fracture permeability is. The research in this paper provides a simple method to evaluate the key parameters controlling the fracture conductivity and permeability in channel fracturing.