Historically, the major cause of poor cement bonding in the Powder River Basin has been the high permeability and low pressure of some zones. Drastically reducing the fluid loss of the cement slurry gave little improvement in bonding and increasing fluid loss material levels led to undesirably long thickening times and poor strength development. Physical shrinkage of cement was still suspected even when thixotropic and conventional expanding cement slurries were used, since cement continued to lose fluid to the formation after it was in place. Other accepted practices for bonding improvement, such as mud conditioning, rotation of the pipe, centralization, preflushing, and pumping in turbulent flow were also used. Even with these techniques, logging showed that bonding was less than adequate.

These problems with cement bonding have led to the use of a new additive. With this new additive, we have seen improvement in the bonding of cement to the formation faces and to the pipe. This additive (1) can be dry-blended with cement, (2) its reactivity in cement slurries is controllable over a wide range of temperatures without the use of special additives, and (3) is also compatible with most retarders and fluid loss additives.

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