A completion fluid can be defined as any fluid used in the production zone before putting a new well on line. Workover fluids are used in the remedial work of wells, which have been already in production.These fluids need to be inherently clean, so as to minimize formation damage. Completion and workover fluids are used in well cleaning for removal of drill cuttings, mud filter cake, cement, etc., and sand control during perforation. A separation/filtration system remove the particles, than re-circulating the filtered completion fluid to the well.
The Problem - Causes of formation damage
• All fluids that come in contact with a productive formation should be clean and this includes the drilling fluid, perforating fluid, completion fluid, workover fluid, under reaming fluid, etc.
• Invasion of fine solid particles into the formation can cause a decrease in permeability around the well bore that directly reduces the productivity.
Completion Fluid Filtration
• Filtering of completion & workover fluids is necessary to avoid damage the formation.
• To minimize formation damage the brine should be, ideally, free of solids. From practical point of view solids removal down to 5 µm or smaller can be obtained economically
• The benefit of a consistent and reliable fluid cleanliness, leads to higher production rates and longevity of productive wells..
• For an extended cartridge life it is necessary a pretreatment upstream of filter cartridges for to remove the bulk of particles, before filtration. This can be settling tanks, shale shakers, centrifugal separators (hydrocyclone) and other available separation systems.