CASING STAND-OFF BAND FOR USE DURING THE RUNNING AND CEMENTING OF CASING IN WELLBORES

The stand-off band of this invention is particularly useful when mounted on casing which must be run into deviated well bores to assure that the casing does not stick prior to reaching the desired setting depth and permits the casing to be reciprocated up and down, or rotated, during the cementing operation, in order to obtain more effective cementation of the casing. "Sticking" of the casing, a well known and recognized problem to persons familiar with the art of well drilling and completion, is caused in the majority of cases, by allowing the casing (or pipe) to contact the permeable walls of the wellbore, across which exists a differential pressure due to the hydrostatic pressure of the fluid in the annulus being greater than the native pressure in the porous formations which have been penetrated while drilling. The stand-off band of this invention is useful on a string of casing having a plurality of joints of pipe, with at least some of the joints having an externally enlarged portion attached thereto, such as couplings. The stand-off band includes a rigid metal band mounted about one of the joints as a point intermediate the couplings. The band has an internal diameter larger than the outside diameter of the joint of pipe casing about which the band is mounted and smaller than the outside diameter of the couplings. In addition, the band has an outside diameter smaller than the wellbore in which the casing is being placed, with the band being further characterized by having a major portion of the exterior surface thereof in the form of a smooth cylinder. The band of this invention more effectively prevents the casing joints (on which it is installed) from contacting the walls of the wellbore than prior art devices because of its unlimited resistance to collapse from large lateral forces (caused by crookedness of the drilled hole, intended deviation from vertical of the drilled hole, or a combination of the two), coupled with a superior bearing surface which will not dig into unconsolidated formations, as will prior art devices. The resulting effect of a series of these bands is to prevent the casing from sticking prematurely and permits the casing to be either reciprocated or rotated during the casing cementing operation, to assure more effective displacement of the mud fluid with cement.