Synthesis and Performance Evaluation of Salt- and Calcium-Resistant Loss-Reducing Agent for Solid-Free Well Completion Fluid

Solids-free completion fluids are usually weighted with soluble salts, without solid phase, which causes little damage to the reservoir, and can avoid wellbore complex accidents caused by solid phase particle settling. Therefore, it has attracted more and more attention. However, there is a lack of solid phase plugging particles the system, and the water loss is large, so it is necessary to control the filtrate loss. The conventional loss reducing agent has poor loss reducing effect in high mineralizationine. A new anti-inflammatory and anti-calcium loss reducing agent for water-based drilling and completion fluids without solid phase was synthesized by using 2-acrylam-2-methylpropanesulfonic acid, dimethylaminoethyl methacrylate, dimethyldiallyl chloride ammonium, acrylonitrile, N-vinylpyrrolidone and other raw materials. The optimal synthesis conditions are as follows: 2-acrylamido-2-mpropanesulfonic acid; dimethyldiallyl chloride ammonium: dimethylaminoethyl methacrylate: N-vinylpyrrolone: acrylonitrile is 2:1:3:2:2, the polymerization temperature is 95 ℃, and the PH value is9. Experimental results show that this loss reducing agent has good heat resistance, anti-salt and anti-calcium ability in fresh water, salt water and saturated salt water sl, and has good thixotropy and loss reducing performance. When the addition of loss reducing agent is 2.5%, it still has good loss reducing performance after high rolling at 180 ℃ in 30% NaCl salt water and 5% CaCl2 salt water based slurry, and it has little effect onixotropy; At the same time, the loss reducing agent has a good loss reducing effect in solids-free completion fluids, and its performance in heat resistance, anti-s and anti-calcium is superior to other loss reducing agents at home and abroad.