Oil and gas well integrity is obtained by placing a steel casing in the well and a cement sheath in the resulting casing/formation annulus. To provide zonal isolation, a large portfolio of cementing technology is available to meet various well conditions. Some of these technologies involve dry-blending operations and cement-blend handling of specific-tuned-blends mixing together particles of different characteristics in terms of density, shape, size, and chemistry including mineral and/or organic components. These blends are usually transported pneumatically and loaded to the rig then transferred to the rig silos. During the different transfers, the blend may be prone to segregation, thereby losing its homogeneity, which makes it difficult to use or even unusable.

Flowability is an important blend property for the blend-handling process. Segregation can be viewed as a mechanism leading to a nonrandom degree of uniformity of the different blend components at the scale at which end-use properties are required. Overall, the differences between particles in chemical nature, density, size, and shape will influence the flowability and, above all, the tendency to segregate. Dealing with blends is, therefore complex since they contain small, medium, and coarse particles in various proportions depending on the targeted slurry density and set material properties.

To counter this challenge, an innovative methodology and equipment to characterize the blend flowability and robustness to segregation were developed and implemented.

The laboratory results were validated with those obtained in the large-scale results using a pneumatic conveying flow-loop.

The implementation of the new methodology during the design phase of the cement job was used as a preventive measure to validate the design and quality control of the blend before the blend is prepared and sent to the rig. This helped in designing robust homogeneous blends and reducing the likelihood of blend transfer problems, thus ensuring the placement of the right quality cement slurry and assuring downhole well integrity.

The new methodology described in this paper was applied to tune several field blends known or identified to have problems and to develop of new generation of cementing technologies.

The outcome of this multidisciplinary approach of blend characterization helps the oil and gas industry to anticipate blend-handling issues and to continuously improve quality and field handling of engineered complex blends with high confidence and consistency.

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