Aiming at casing wear problems during drilling and production of ultra-deep wells in oilfields,full-size casing wear test machine was used to carry out casing wear test of TP140V high-steel casing under four kinds of drilling fluids,such as oil base,high-performance water base,saturated salt water and organic salt,and to study the wear mechanism and the change law of wear parame-ters.The results show that the wear depth is 0.076～0.090 cm,the wear rate is 6.42%～7.55%,the wear coefficient is(1.32～1.71)×10-6 cm3/(N·m),and the wear parameters are similar when the four drilling fluids with the same density are added with high weight powder;When adding high-weight powder and iron ore powder,the wear depth of organic salt is 0.188 cm,the wear rate is 15.76%,the wear coefficient is 4.9×10-6 cm3/(N·m),and the friction coefficient is 0.339,and four parameters increase sharply,and the wear depth and wear rate of organic salt are two times that of adding high-weight powder alone.Reducing iron ore powder has obvious wear reduction effect on organic salt drilling fluid,and effectively alleviates the wear rate.Scanning electron microscopy shows that the cas-ing wear surface of organic salt drilling fluid is smoother and flatter than that of saturated saline,and the casing wear mechanism of organic salt drilling fluid and saturated saline drilling fluid is abrasive wear.After addition of high weight powder,three-body abra-sive wear appears in saturated brine,so the content of high weight powder should be reduced when drilling fluid is weighted in engi-neering.
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