Grafted starch filtration loss reduction agent used for drilling fluid and preparation method thereof

The invention discloses a grafted starch filtration loss reduction agent used for drilling fluid and a preparation method thereof. The grafted starch filtration loss reduction agent used for drilling fluid is composed of starch, acrylic acid, acrylamide and sodium p-styrenesulfonate in a mass ratio of (30-50):(10-25):(20-40):(5-15):(2-5). The prepared grafted starch filtration loss reduction agent used for drilling fluid has the advantages that molecular weight is greatly increased, so that the thermal stability and anti-pollution capacity of the grafted starch filtration loss reduction agent are greatly improved; and meanwhile, the grafted starch filtration loss reduction agent used for drilling fluid can enable the rheological property of the drilling fluid to be greatly improved. 本发明公开种钻井液用接枝淀粉降滤失剂及其制备方法，由淀粉、丙烯酸、丙烯酰胺和对苯乙烯磺酸钠以质量比m(淀粉)：m(丙烯酸)：m(丙烯酰胺)：m(对苯乙烯磺酸钠)：m(引发剂)＝(30～50)：(10～25)：(20～40)：(5～15)：(2～5)组成。本发明制备的钻井液用接枝淀粉降滤失剂分子量大幅增加，使得其热稳定性与抗污染能力得到较大的提高，而且所述钻井液用接枝淀粉降滤失剂可以使钻井液的流变性得到大大的提高。