Abstract
Centrifuges and shakers are the first defense when managing a drilling fluid against wellbore cuttings and solids contamination. The buildup of drill solids in a fluid can have a detrimental effect on its performance and properties. Much of the solids-control equipment in the field was designed with conventional API-grade weighted fluids in mind, but the increasing use of drilling fluids in the field weighted with micron sized particles has presented a challenge in the use of existing solids-control technologies to achieve effective solids removal.
With a decanting centrifuge, the particle size and density of API-grade barite is such that the centrifugal force tends to remove much of it from the fluid together with the undesired solids. Similarly, the wire mesh size for shaker screens is selected to be effective in removing the cuttings, but consequently, the coarser fraction of the weight material is removed. A significant reduction in weight material particle size has the potential to demonstrate a different behavior. This paper will present data obtained from both the field and from specifically designed yard tests conducted on micronized weighted drilling fluids.
The data discusses solids removal efficiency using different centrifuge designs as well as shaker screen performance, and demonstrates how these can be optimized for the preferential removal of undesirable contaminants and minimize removal of the desired weight material. The operating parameters of the centrifuge have been defined to provide the optimum solids removal efficiency.
Solids analysis, particle size and density results that provide definitive centrifuge parameters for processing fluid weighted with micron-sized material; the results are compared with those parameters obtained from a conventional API-barite weighted fluid showing that lower torque, higher throughputs and lower wear and tear on equipment can be achieved with micronized weighted fluids.
