The use of solids free brines as completion/work-over fluids has given rise to the need for methods of fine solids removal. Filtration of clear brines has become a major concern to operators. This paper will address the problem of removal of fine suspended particles in the .5-50 micron range.

The body of the paper deals with the removal of fine solids by flow through porous media. The mechanics of removal discussed include sieving, bridging, adsorption, and settling within the porous matrix. Parameters such as flow density or velocity and pressure drop will be defined. Each of the removal mechanisms will be discussed in terms of how the operational parameters affect filtration efficiency. A discussion of surface and depth filtration will be included. Also, performance parameters such as effluent quality, dirt capacity, and clear pressure drop will be discussed. Design of the porous media will be covered along with a discussion of how filters are rated. Current filtration techniques used in the oilfield will be reviewed and classified. The classification will include the type of removal mechanism whereby the specific filter operates, the effect of operating conditions on efficiency, and what kind of performance can be expected.

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