Robert Barree, Marathon Oil Co., discussed technology advancements that are challenging traditional fracture models at a recent meeting of the Oklahoma City Section. Fracture design philosophy is based on fracture containments, modeling of screenout mechanisms, fluid rheology, and final fracture conductivity. The traditional fracture geometry and containment model assumes that a rock is a linearly elastic, homogeneous system. However, rocks fail in different ways, depending on containing stresses. The model should be modified to consider the effects of sheer slipping and decoupling.
New findings challenge the traditional proppant transport model.
Screenout experiments demonstrate that proppant particles bridge in a slot when the gap equals the largest particle diameter. It is now believed that bridges have less impact in screenouts than had previously been assumed. More and different causes of screenout were also evaluated. It was discovered that proppant settled in dehydrated nodules to leak off in high-permeability areas. As pumping continues, these nodes continue to grow until the entire fracture is packed, except for a narrow channel.