Surfactants are typically added into fracturing fluids to assist flowback and/or enhance oil and gas production from liquids-rich shale formations. Two primary benefits that can be overlooked are the potential capability of surfactants to initiate microcracks near primary fractures and spontaneous imbibition farther into the formation rocks. With the additional initiation of microcracks and access to hydrocarbon reserves, initial production can be enhanced and production declines, over time, can also be mitigated.
In this study, new mechanisms for surfactants to initiate microcracks and accelerate crack growth are proposed in which the speed of microcrack propagation could be controlled by the rate at which surfactant is advected to the crack tip by means of induced Marangoi flows (Vella et al. 2006). The accelerated crack growth is related to a decrease of the crack surface energy enabled in the presence of surfactant.
On the other hand, a new mechanism has been previously proposed for increasing the contact area between fracturing fluids and the matrix. The working hypothesis is that a surfactant, when properly tailored to treatment fluids, can spontaneously spread in the matrix and access additional hydrocarbon reserves.
The data indicate that fracturing designs could be further optimized by using a surfactant to activate more cracks. The shut-in time immediately after fracturing also could be crucial for enhanced well productivity. An extended shut-in time could result in the additional initiation of microcracks, farther penetration of fracturing fluids into the matrix, and greater oil recovery in liquids-rich shale plays.