A novel low molecular quaternary polymer as shale hydration inhibitor

Abstract

Polymer inhibitors for deep shale gas drilling have poor temperature resistance and can influence the rheological attributes of the drilling muds. To overcome this issue, a high temperature resistant and low molecular weight quaternary polymer DVAA was prepared by hydrothermal radical polymerization. The characterizations of the DVAA were evaluated by IR, NMR, TG, and GPC, and the inhibition, rheology, and filtration parameters were examined. The shale inhibition mechanism was evaluated by the SEM, zeta potential, contact angle, and XRD. Initial decomposition temperature of DVAA is 354.83 °C and Mp is 4583. The performance test outcomes suggest that using DVAA could lead to a linear expansion reduction rate of MMT at 73.4%, whereas the rolling recovery rate of cuttings was 86.25%. The API filtration of 4% MMT after hot-rolling is 13.6 ml. The mechanism of DVAA showed that DVAA and MMT form ionic bonds and hydrogen bond through electrostatic attraction and can still maintain a good structure under elevated temperature conditions. DVAA can effectively weaken the surface hydration by entering the crystal layer to replace the inter-layer cations, where it forms a polymer-film on the bentonite surface. In summary, the research and development of the DVAA can provide an effective guarantee for the stability of the wellbore during the development of deep shale gas reservoirs.