Instability of wellbore is a common problem when drilling in complex strata,which brings great difficulties to drilling.Traditional way of casing can isolate instable wellbore reliably,however,there are some shortcomings: for example,reducing hole-diameter etc.In order to seek a simple,effective way which does not reduce the well diameter for supporting collapsed well section,hot-melt was used in dry hole and polyurethane in hole with water.The paper described the technological principle and lab tests of th...