Ultrafine cements are particulate, cementitious grouting materials that were initially developed as a replacement for unacceptably toxic chemical grouts for Civil Engineering applications. Several basic types are available: ultrafine slag cement (M1), ultrafine Portland cement (M3) and ultrafine portland/slag (M5). The chemical compositions and physical properties of these materials are shown in Table 1 and 2 and in Figure 1. Their extremely fine grain size enable them to permeate medium sands and fine fractures in rock. These and other properties have led to ultrafine M5 cement slurries being adopted for use in oilwell cementing applications, especially for gas and water control. The results of a series of experiments on ultrafine M5 cement slurry have indicated that it remains in a fluid state at high temperatures for at least as long as slurries formulated with Class G portland cement, demonstrating its applicability for use in hot, deep wells.

Applications for M5 involve squeeze cementing the Wasson South Unit 7514 casing leak at 3222 feet. 30 sacks of M5 were successfully used to seal the casing leak as the ultrafine cement was drilled out and the casing tested to 1000 psi with no bleed-off. In another application, M5 ultrafine cement was used to squeeze repair a casing leak. The previously repaired leak had broken down and was taking lift gas and giving up sour water. M5 was used to seal the leak and restored top allowable, water-free oil production from the well.

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