In addition to scale particles, produced water often contains other suspended solids. These include formation sand and clays, stimulation (fracturing) proppant, or miscellaneous corrosion products. The amount of suspended solids is generally small unless the well is producing from an unconsolidated formation, in which case large volumes of sand can be produced. Produced sand is often oil wet and its disposal is a problem. Sand removal is discussed in a later subsection entitled "Equipment Description."

Small amounts of solids in produced water may or may not create problems in water treating depending on the particle size and its relative attraction to the dispersed oil. If the physical characteristics and electronic charge of such solids result in an attraction to the dispersed oil droplets, the solid particles can attach to the dispersed oil droplets to stabilize emulsions, thereby preventing coalescence and separation of the oil phase. The combined specific gravity of the resulting oil/solid droplet can be approximately equal to that of the produced water, and gravity separation becomes difficult if not impossible.

The concentration of suspended solids can be monitored with 0.45-micron Millipore filter test, and residue can be analyzed for mineral content in an attempt to identify the source of the solid.

When solids are present, the following practices should be applied:

• Chemical treatment must be used to "break" the electronic attraction between the solid particle and the oil droplet.

• Equipment design must incorporate solids removal ports, jets, and/or plates.

• Oil measurement techniques not...