Leli thuluzi lilungele ukukhishwa kokungcola okungase kushiywe phezu kwezindonga zangaphakathi ze-casing, njengosimende oqinile, i-wax eqinile, amakristalu ahlukahlukene kasawoti noma amadiphozithi, ama-perforation burrs, izinsalela ze-iron oxide ezibangelwa ukugqwala, ukuze kwenziwe wonke amathuluzi omgodi ophansi. dlula ungavinjiwe. Ikakhulukazi lapho imvume encane eyindilinga itholakala phakathi kwamathuluzi embobo ephansi kanye nobukhulu bangaphakathi, ukuchithwa okuphelele kuba kudingekile kakhulu ngaphambi kokuqhubeka nokusebenza. Njengamanje emthonjeni omkhulu we-petroleum ukukhuhla odongeni lwangaphakathi lwe-casing ngokusebenzisa i-casing scraper kuyisinyathelo esidingekayo.