Parameter simulation and optimization in channel fracturing

•The relationship between proppant pillar spacing and the pulse time in channel fracturing is provided.•The fracture width reaches its maximum value when the horizontal spacing is equal to the vertical spacing.•The method for determining the critical pulse time is developed to guarantee fracture opening.

Channel fracturing revolutionarily changes continuous sanding into discontinuous distribution by wrapping proppant particles with a degradable fiber and then injecting these packs or pillars into the formation. Channel fracturing creates open channels between pillars and substantially increases the fracture conductivity. The pulse time of injecting proppants can influence pillar spacing, thereby changing the opening of the fracture. Under different formation conditions, determining a proper pulse time to improve the wellbore productivity is the key problem in channel fracturing.On the basis of Hertz contact theory, we assume that a proppant pillar is a standard cylindrical indenter. We also calculate the penetration depth beneath the original surface. In this manner, we obtain the residual fracture width under a certain confining stress. This residual fracture width serves as our optimization objective. Then, by combining the flow conservation equation, we find that a restriction relationship exists between the pillar spacing and pulse time. By controlling the variables, we adjust the parameters to find the maximum fracture width. The fracture width reaches its maximum when the horizontal spacing equals vertical spacing.A set of simulations are completed and analyzed. The results show that the pulse time, pillar spacing, and formation parameters such as the closure pressure, elasticity modulus and initial crack width, can significantly affect the supporting effectiveness of the proppant pillar. Critical points exist when these parameters increase or decrease to a certain level. For the convenience of field operation, a reference plate is provided. A proper pulse time can be determined on the plate under certain formation conditions, thereby providing theoretical guidance for actual channel fracturing.