Casing centralization is one of the key elements to ensure the quality of a cementing job by preventing mud channeling and poor zonal isolation. Centralizers can also assist in running of the casing and prevention of differential sticking. The challenge that both operators and service companies face is to place the right amount of centralizers at the optimum positions on the casing. While operators may be conservative, service companies tend to be liberal, in selecting the number of centralizers for a given application.

Casing standoff depends on well path and hole size, casing size, centralizer properties, and many other variables, but most importantly, centralizer placement. Experience plus computer modeling enable both centralizer vendors and operators to conduct centralizer optimization prior to field execution. One approach is to specify spacing using our experience, then let software check if it yields satisfactory standoff profile. Alternatively, we can specify required standoff and let the software tell us how to space centralizers. "Specify spacing" mode gives the simple-to-install centralizer placement because of its constant spacing result. However, this method may compromise the quality of standoff or quantity of centralizers. "Specify standoff" mode ensures the minimum standoff of casing between centralizers, while yielding difficult-to-follow placement program.

To get the best elements from both approaches, we have developed an optimum placement solution, which is specifying standoff with incremental spacing requirement. For high impact operations such as deepwater and use on inline bowspring centralizers, once a casing schematic is available, the centralizer placement is re-evaluated to optimize exact placement of each centralizer.

With the help of computer modeling, centralizer placement can be evaluated and optimized. This practice will result in better cementing job and cost-effective centralizer placement for directional wells. This paper will report examples of how such optimization can be achieved.

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