Patent ID: 8668007

Claim:
A non-rotating casing centralizer adapted for use with a casing disposed in a borehole, the casing centralizer comprising: a tubular sleeve made from a molded polymeric material and having an inside surface adapted to surround a section of casing, the inside surface of the sleeve having circumferentially spaced apart axially extending grooves positioned between substantially flat bearing surface regions for contacting the outer surface of the casing, the axial grooves allowing fluid to circulate therethrough to form a non-rotating fluid bearing upon circulation of fluid under pressure between the inside surface of the sleeve and the casing, characterized in that: the tubular sleeve has a plurality of helical blades integrally formed with the polymeric tubular body and projecting from an outer surface of the sleeve, the helical blades having outer surfaces adapted for contact with the borehole, the helical blades providing a flow path for fluid passing between the blades, the flow path passing through the borehole between upper and lower ends of the tubular sleeve, the tubular sleeve comprising a continuous non-hinged wall structure for surrounding the casing, a metal cage embedded in and circumferentially encircling the tubular body of the sleeve, to reinforce the continuous wall structure of the sleeve; and in which the helical blades have a blade height (h) and an average blade width (w) such that, during rotating and sliding motion of the sleeve in the wellbore, a minimum of two blades are positioned to maintain contact with the wellbore; wherein the number (N) of blades on the tubular body is equal to: N =π( R c +t+h )/ w wherein: R c =sleeve radius t=sleeve thickness h=blade height w=average blade width wherein the number (N) is rounded to the nearest integer.