When drilling in lost-circulation-prone locations using conventional cements and circulation methods, significant challenges can be encountered during primary cementing operations. Using conventional circulation cementing methods might not be the best choice in circumstances where a wellbore has formations with low fracture gradients unable to withstand the pressure commonly associated with conventional circulation cementing operations. The formation could possibly breakdown under the pressure applied by the cement, causing the cement to be lost into the formation. Cement lost into the formation is undesirable because of the associated damage and expense. To overcome these challenges, the use of an unconventional cementing method during primary cementing operations is proposed. This method reduces the equivalent circulation densities (ECDs), minimizes excess cement volumes, and eliminates displacement, thereby increasing the chances of a successful cement job with minimum environmental impact. Reverse circulation can significantly reduce bottomhole pressures and allow placement of cement with no apparent losses in many cases. This unconventional cementing method is discussed and a case history is presented.
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