| It has been reported that the Macondo tragedy was caused by a faulty cementing operation. This, in turn, has forced operators to pay special attention to this aspect of well completion. One of the contributing factors to the faulty cementing operation of Macondo is said to be an insufficient number of casing centralizers. This is important because the success of any casing cementing operation is largely dependent on the centralization of the casing in the wellbore.;Centralizers are placed on the casing strings at predetermined distances in an effort to retain the casing in the center of the wellbore, thereby maximizing the coverage of cement around the casing. Placement, as well as the number, of centralizers is dependent on the standoff of the casing in the wellbore. Standoff is defined as the minimum distance between the outer diameter of the casing and the wellbore.;For casings under tension, API has recommended formulas to calculate casing standoff in 3D wellbores, which takes into account the inclination and azimuth angles. In addition, literature is available that considers casing under compression due to the fluid forces acting on the casing string and shows a considerable difference in standoff when considering compression as compared to tension alone. Currently all available literature considers the wellbore as rigid only. This paper considers the formation type, ranging from unconsolidated sand to shale, and calculates its effect on standoff. The results show that the formation type may significantly affect the outcome of standoff, and therefore should be considered when calculating standoff. |
