On-Site Completion/Workover Fluid Analysis Using a Portable Laser Particle Size Counter

Abstract

ABSTRACT The frequent use of clear brines as completion/workover fluids has increased the need for improved methods of solids removal during these operations. Studies in recent years, relating formation damage with particle size distribution in completion/workover fluids, magnify the need to make the brines as solids-free as possible (1–8). This fact has led the industry to re-examine the filtration process on completions. Presently, there are no methods commonly used to determine the particle size distribution in fluids at the rig site. On-site measurements of solids generally involve centrifuging a sample of fluid to determine the percent by volume of solids or monitoring solids content by turbimetric methods. The volume percent of solids is important; however, knowledge of the particle size distribution and population density is important in order to minimize formation damage. Tests can be run in the laboratory on several types of instruments to determine particle size distribution, but these represent "after the fact" data. In other industries, a small laser particle counter is being used to determine size distribution and actual particles per cubic centimeter in clear fluids. The instrument is interfaced with a PC computer or hand-held calculator to compute the size distribution and the population density of the particles. The instrument is portable, precise, and practical for use in the oilfield. It gives field personnel an opportunity to check the solids distribution of the fluid going into the well and the efficiency of the filtration equipment on-site. The data obtained using the laser particle counter together with the reservoir data is a good means of detecting potential formation damage associated with the solids found in the completion/workover fluids. Results of lab tests, yard tests, and field data have shown applicability of the laser particle counter to analyze clear brines on-site. Scanning electron microscopy was used to determine the type of material passing through the filters. Comparison of the field and lab tests has given a better understanding of the limitations of the currently available filtration equipment.