Why We design Annular Clearance Bow Spring Centralizer
ZHENGZHOU, OCT 28,2016-The bow spring centralizer device is used for centralizing the casing in the borehole,usually the bow centralizer is installed between two API stop collars which ensure to casing.This kinds of casing centralizer is composed of flexible bow spring and slip-on end collars or hinged end collars.Generally speaking the O.D of centralizer is smaller than I.D of hole,as we know,the bow spring centralizer is flexible feature,when the centralizer is running in the borehole,it is firstly compressed to fit within a small annular space and which can later expand to center casing within the bore hole.
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The important function of bow spring centralizer is to center casing inside a drilled hole and then form annular channel of cementing in the casing hole annulus. Bow springs extend radially outwardly from the center bore of the centralizer to provide desirable casing stand-off from the wall of the bore hole. Wide-deployment centralizers are centralizers designed to provide substantial stand-off from a nearby object such as the wall of a bore hole. At the same time getting a minimum annular clearance must be low annular clearance of bow spring centralizer rib and also can not prevent flow of drilling mud through the annulus between the smaller and larger casing.
There are other two reasons for designing low annular clearance centralizer,one is to reduce the risk of centralizer rib demage.Because any wellbore is completely vertical. As casing is lowered into a well, the high strength steel resiliently twists, turns and flexes as it passes through restrictions and bends in the non-linear and non-uniform bore hole.The other reason is to securing the centralizer in place on the exterior of casing that is to be lowered into the well.