OVERVIEW

Dilution refers to the process of adding a liquid phase to a drilling fluid to decrease the drilled-solids concentration. Dilution is used in several ways. If no solids-control equipment is used or if the equipment is used ineffectively, dilution may be the principal method of keeping drilled solids to a reasonably low level. This is an expensive solution to the problem. For example, to decrease drilled solids by 50% requires that 50% of the system be discarded and replaced with clean drilling fluid. Usually dilution is used after processing by solids-removal equipment to dilute drilled solids remaining in the drilling fluid. Dilution may be added as a clean drilling fluid or as the liquid phase of a drilling fluid with the other necessary drilling fluid ingredients, usually through a chemical barrel and a mud hopper. In this discussion, dilution will refer specifically to the clean drilling fluid necessary to decrease drilled-solids concentration. Clean drilling fluid is the liquid phase with all necessary additives such as barite, polymers, clay, etc.

As an example of dilution, consider a well in which the drilling-fluid specifications suggest that the volume percentage of (%vol) drilled-solids concentration should be, and is, 6%vol. Assume that 10 bbl of formation solids are brought to the surface and that no solids-removal equipment is used. All 10 bbl would be retained in the drilling-fluid system. These solids would require dilution to maintain the 6% volume concentration in the new drilling fluid.

The new...