New methods to evaluate impacts of osmotic pressure and surfactant on fracturing fluid loss and effect of contact angle on spontaneous imbibition data scaling in unconventional reservoirs

Abstract

Osmotic pressure (Posmotic) is an important mechanism for fracturing fluid loss in clay-rich unconventional reservoirs. Surfactant is often added to the fracturing fluid to control this loss. While laboratory-based methods can be used to evaluate the impacts of Posmotic and surfactant on fracturing fluid loss, two important challenges exist in the commonly-used methods: 1) a pair of sister core plugs have to be used; and 2) the petrophysical properties of the sister core need to be very similar for meaningful comparisons, which may be impossible in many cases. In addition, for the scaling of laboratory spontaneous imbibition data, wettability (i.e., contact angle, θ) should be incorporated into the scaling model. However, θ is a scale-dependent parameter, e.g., macro- (θmacro), micro- (θmicro) and pore- (θpore) contact angles can vary significantly. It is currently uncertain which θ should be used in the scaling model.