Casing scraper is ideal for the removal of dirt which may be left over the inside walls of casing, such as solid cement, hard wax, various salt crystals or deposits, perforation burrs, iron oxide residues resulted from rusting, so as to make all down hole tools pass through unblocked. Especially when a small circular clearance is available between the down hole tools and casing inside diameter, the complete scrapping becomes more necessary before further working. At present in the large petroleum well scrapping in the internal wall of casing by use of casing scraper is a necessary step.
Working principle
Before run into downhole,the max. installation size of blade shall be bigger the inside diameter,after run into downhole,the blade is pressed to press the spring down,theradial force is given by spring. When hard materials need to be scrapped,scrapping for several times must be done before scrapped to casing inside diameter. The scraper is connected on the low end of drill string,the moving of drill string up and down make an axially feeding in the scrapping operation.
It is showed in the structure that each spiral blade has two internal and external curved scrapping edges. When the blade is working for reciprocating scrapping,the internal edge and external edge are working in turn,and there is a wider transverse edge band between two scrapping edges stands a cutting and milling action to the cut surface.
The strap blades are uniform distributed on the scraper so that the returned mud can take the scraped substances away.
