Preparation and Performance Evaluation of an Amine-based Silanol Shale Inhibitor

An amine-based silanol shale inhibitor Si-HPEI has been developed to deal with the problem of poor high-temperature stability of shale encapsulators encountered in high temperature deep well drilling. To improve the adsorptive capacity at elevated temperatures of a polymer, siloxane groups were introduced into the backbone of a hyperbranched polyethyleneimine (HPEI) molecule to produce an amine-based silanol shale inhibitor. Laboratory evaluation of Si-HPEI showed that Si-HPEI can tolerate clay contamination of up to 35.0%. Hot rolling test with a drilling fluid treated with 0.5% Si-HPEI gave a shale cuttings percent recovery of 70.33%. Si-HPEI functions at 160℃, making it a better high temperature shale inhibitor than conventional shale inhibitors. The working mechanisms of Si-HPEI were analyzed through laboratory experiments such as the measurement of the basal spacing of clays, the high temperature adsorption capacity, the encapsulation capacity, hydrophobicity and micromorphology. It was found in laboratory study that hydrolysis of Si-HPEI produces silanol groups which react through polycondensation with the silanol groups on the surfaces of clays, in this way the Si-HPEI is chemically adsorbed firmly on the surfaces of clay particles. This adsorption is so strong that it is not easy for the Si-HPEI molecules to detach from the clay particles and hence strengthens the forces between the clay particles, effectively encapsulates the clay particles and changes the hydrophobicity of the surfaces of the clays, thereby preventing water molecules from invading between clay platelets which causes hydration and dispersion of clays.