Oil and gas shale hydraulic fracturing designs for new wells drilled typically call for water volumes as high as 50,000 m3 (314,000 bbls). The cleanup of these massive water volumes during flowback must be efficient and minimize fluid invasion into the matrix. Once the saturation of the invaded water zone is reduced to the lowest possible level during flowback (cleanup operations), hydrocarbons can flow freely into the wellbore. However, the flowback behavior in unconventional reservoirs is quite different than in conventional reservoirs where soakback and slowback techniques are implemented. It is not uncommon for these wells to be shut in or for weeks or even months following the hydraulic fracturing treatment. Chemical and surfactant flowback enhancers such as microemulsions and nano-surfactants are additives typically used in hydraulic fracturing to assist in flowback design and improve load fluid recovery as they minimize fracture face damage due to water blockage.
In this paper, we describe the successful field application of a multi-functionalized surfactant (MFS) that significantly outperformed common surfactant chemistry when applied to mixed-wettability shale core samples in laboratory Amott cell tests. The results from the laboratory testing were reflected in field trials: the relative permeability to hydrocarbon was increased and production was enhanced.