Reduced adsorption of polyacrylamide‐based fracturing fluid on shale rock using urea

Abstract Hydraulic fracturing is generally necessary to achieve economically viable production rates during exploitation of shale reservoirs. Polyacrylamide‐based fracturing fluid is commonly used in shale fracturing. Polyacrylamide ( PAM ) becomes adsorbed in the shale micro‐fractures, decreasing the permeability of the reservoir. For improving the production of shale after being stimulated, the adsorption behavior and adsorption mechanism between the PAM and shale are studied. An ultraviolet spectrophotometer is used to obtain the amount of adsorption. To observe the adsorption morphology, a scanning electron microscope is employed. The action force between the PAM and shale rock is analyzed through Fourier transform infrared spectroscopy, zeta potential instrument, and X‐ray photoelectron spectroscopy. The results indicate that hydrogen bonding is the key force between the PAM and shale. A kind of shale micro‐fractures model is designed to determine the recovery of permeability. Urea breaks the hydrogen bonding and keeps the molecular of HPG stretch which can decrease the amount of adsorption on the shale surface and effectively recover the permeability of shale micro‐fractures up to 72.46% after being damaged. In conclusion, it is believed that the competitive adsorption is a new approach for remediation of the permeability damage by PAM‐based fracturing fluid and has great potential in oil field application.