Synthesis and Properties of a High-Temperature Grafting Polyvinyl Alcohol Fluid Loss Additive

As fluid loss additive for oil well cement,polyvinyl alcohol(PVA)is not suitable for formations above 120℃,a novel oil-well cement fluid loss additive(PVA-1),chemically cross-linked polyvinyl alcohol(PVA)was synthesized from PVA,2-acrylamido-2-methyl propane sulfonic acid(AMPS),N-vinyl-2-pyrrolidone(NVP),and cross-linking agent.The properties(water-loss control property,rheology,thickening curve,thickening time,free water,compressive strength and static gelling strength)of the cement slurry with PVA-1 were evaluated.The results show that the API fluid loss of the cement slurry with PVA-1 can be controlled under 50 mL,while its temperature tolerance is next to 150℃;the cement slurry with PVA-1 has slightly longer thickening time,no reduction in compressing strength and improved water precipitation resistance;moreover,the fluid loss additive (PVA-1)is highly compatible with dispersing agent DZS and retarder DZH,and can improve gas channeling of slurry.The study shows that PVA-1 can meet the requirements of high temperature cementation at nearly 150℃.