Preparation and application of melamine cross-linked poly ammonium as shale inhibitor

In this paper, a series of poly ammonium shale inhibitors were prepared from diethylamine, epichlorohydrin, and melamine (DEM) and their inhibition to shale were evaluated by bentonite linear expansion test, anti-swelling experiments, and mud ball experiments. Additionally, other properties of drilling fluid treated by poly ammonium were evaluated. Anti-swelling results showed that anti-swelling rate of DEM-8 reaches up to 97.8% when its concentration reaches to 0.8%. Mud ball experiment and drilling fluid evaluation showed DEM-8 has strong inhibitive capability to bentonite hydration swelling and controlling the particle size of bentonite in a large scale. The inhibition mechanism of DEM-8 was studied by thermogravimetric analysis and scanning electron microscope. The results demonstrate that DEM-8 can be adsorbed on clay surface through electrostatic interaction and hydrogen bonds by an anchoring effect and a hydrophobic effect.