Publications

Particles in completion and workover fluids result in formation damage and decreased well productivity. Historically, for these fluids, operators have specified a level of cleanliness in terms of a gravimetric level or parts per million. However, industry experts have realized that this type of specification does not actually address or solve the formation damage problem.This paper presents the most recent laboratory and field data showing that a fitration level based upon particle size and number of particles rather than a weight percent is necessary to protect the formation during completion and workover operations. Laboratory data was gathered using 100-600 md cores and potassium chloride (KCl) solutions with particles in the 0-10 micron range. The study related fdtration efficiencies to flow decay and concluded that filtration of 100 percent of 2 micron particles resulted in a flow decay of only 1.0 percent.Field data and case histories from the U.S.A. and Southeast Asia have shown that absolute ffltration efficiencies at 2 micron size particles resulted in increased well productivity. The improved production occurred in oil and gas wells for offshore and onshore operations. Operational and field performance data are reported on the different types of filtration equipment that can be used to achieve these levels of cleanliness. Test procedures used to measure field performance are described.The paper concludes with a unique method that will provide operators with a procedure to specify a level of filtration. The procedure uses actual field data based upon the number of barrels of fluid lost to the formation, the number of perforations and their surface area, and the number and size of particles per barrel of fluid to calculate particle invasion. On a graph, particle invasion is inputted and a filtration level can be selected to minimize formation damage to less than 1.0 percent, rather than the more usual 50 to 95 percent.