Researches On Synthesis, Properties And Mechanism Of High Temperature Resistent And Sodium/Calcium Tolerant Filtrate Reducer For Water-based Drilling Fluid

High temperature resistent and sodium/calcium tolerant fluid loss additive is the most important agent for deep well and superdeep well drilling fluid, and it is always the focus of the study. Based on the knowledge of drilling fluid chemistry and polymer chemistry, a new kind of high temperature resistent and calcium/salt tolerant filtrate reducer for drilling fluid which has independent intellectual property rights is developed.This paper also brings forward some new theoretical research and exploration about high temperature resistent and sodium/calcium tolerant fluid loss additive.Firstly, this article, from the requirement on fluid loss additive performance of high temperature resistent and sodium/calcium tolerant drilling fluid, designs agent’s chemical molecular structure in the light of filtration reducing mechanism under the circumstance of high temperature and sodium/calcium existing. Then, four kinds of monomer(AM, AMPS, SSS, NVP) is choosen to synthesize water-soluble polymer fluid loss additive AM/AMPS/SSS/NVP through oxidation reduction reaction. The best synthetic condition is optimized by analyzing the effect of synthetic conditions such as hydrogen ion concentration, initiator type and concentration, total concentration of monomer, ratio of different monomer, temperature of reaction and reaction time. The result of experiments shows the best synthetic condition can optimize properties of fluid loss additive and lays a solid foundation for its industrial production and field application.Properties of AM/AMPS/SSS/NVP which is synthesized under the best synthetic condition are characterized, such as:molecular structure, chemical composition, viscosity-average molecular weight, molecular weight distribution and thermal stability. Characterization shows that molecular structure and chemical composition of the polymer is match with the design, viscosity-average molecular weight and molecular weight distribution of polymer is appropriate, and the polymer has excellent thermal stability.Performance evaluation of AM/AMPS/SSS/NVP obtains two results. Firstly, the polymers can perform excellent filtration control properties under high temperature (180℃) and high salt concetration (sodium chloride up to100OOOmg/L and calcium chloride up to5OOOmg/L).Secondly, the polymers has a unconspicuous influence on the rheology of drilling fluid and it can keep the rheology of drilling fluid stable under high pressure and high temperature.Self-assembly structure of AM/AMPS/SSS/NVP, and adsorption between polymer and montmorillonite particles is investigated by modern instrumental analysis. Polymer’s influence on microscopic appearance of mud cake, Zeta-potential and Particle size distribution of drilling fluid is also investigated to analyze the filtration control mechanism of the polymer. The study shows the polymer has high temperature resistent and sodium/calcium tolerant properties and can adsorb montmorillonite particles effectively under high temperature and high salt concentration. Because of the adsorption and encapsulation of AM/AMPS/SSS/NVP, mud cake quality and dispersion of montmorillonite particles is improved. Self-assembly structure of the polymer can also decrease the permeability of mud cake to perform the properties of reducing filtrate loss under high temperature and high salt concentration circumstance.AM/AMPS/SSS/NVP passes the laboratory evaluation and field test of oilfield. And it is applicated in the field(well Zhonggu105H and well Zhonggu1C) successfully. It is shown by result of field application that the polymer has a unconspicuous influence on the rheology of drilling fluid and good performance on filtrate control and compatibility.