Facilities Sand Management: Critical Sizes of Produced Solids
Dr. Hank Rawlins - eProcess Technologies
? Technical Authority - Facilities Sand Management · Produced Water Treatment · Compact Separation Systems
Not all solids should be treated as equal.
Prime Directive of Facilities Sand Management
The primary purpose is to ONLY treat, remove, or modify only the solids that are interfering with hydrocarbon production. Principally this is reducing/eliminating erosion or preventing settling in low velocity zones.
With this in mind, the goal should be to target removal of critical particles only and not overdesign the Facilities Sand management system.
You don’t need to remove all the solids – only the problem ones.
Example: The practical removal size limit for cyclonic technology is 10-15 microns. Removal down to 5 microns requires filtration, however filters are 5-10X the size, weight, and cost of cyclones. If particles >25 microns are interfering with hydrocarbon production, then don’t over-design by using filtration.
Effect of Particle Size on Erosion
Based on the U of Tulsa ECRC model (discussed in article B-FSM-27) there is a threshold particle size below which erosion is negligible. See Figure 7 from the McLaury et al. paper (SPE 38842).
The curves are shown for sand particle size versus penetration rate in elbows. The lower curve is for water (20 ft/s) while the upper curve is for methane (4000 psi & 250°F at 100 ft/s). The threshold particle size is fluid dependent. In water sand below 100 microns has steep drop-off in erosion, while sand in gas has a threshold around 20 microns.
These curves indicate that in their respective flow regimes, only particles above this threshold should be removed – the smaller sizes are not significant in the design. The larger particle sizes are easy to remove, thus simplifying the Facilities Sand Management system.
Effect of Sand Morphology on Erosion
Sharp angular particles create a higher erosion rate than round shape. This shouldn’t be a surprise to anyone. However, the magnitude of the difference is surprising.
Data from Cousens (1984), whose photographs are shown in the header, shows >100X the erosive rate of crushed glass compared to spherical glass beads. Clearly particle shape has a strong impact.
Work at U of Tulsa ECRC shows the same ranking, albeit at a smaller magnitude difference. The McLaury and Shirazi paper from 1999 (SPE 56812) incorporates sand sharpness factors (Fs) into the erosion model. Rounded, spherical glass beads have only 20% the erosive power of sharp cornered, angular sand.
This leads me to the question – can sharpness of sand particles be reduced in-situ? Some ideas we’ve researched include particle coating and partial chemical dissolution (increasing curvature or sharpness increases chemical potential). These topics are still in the R&D stage and will be published in the future.
The next article will discuss hazardous solids from oil and gas production.
References
- Cousens, A.K. 1984. Fitzwilliam College, "The Erosion of Ductile Metals by Solid Particle Impact", PhD Dissertation.
- McLaury, B.S. and Shirazi, S.A. 1999., Generalization of API RP 14E for Erosive Service in Multiphase Production, SPE 56812 https://doi.org/10.2118/56812-MS
- McLaury, B.S., Wang, J., Shirazi, S.A., Shadley, J.R., Rybicki, E.F. 1997. “Solid particle erosion in long radius elbows and straight pipes,” Paper 38842 presented at the SPE Annual Technical Conference and Exhibition, San Antonio, TX, 5-8 Oct. https://doi.org/10.2118/38842-MS
Post: B-FSM-031
Date: 13-Mar-18
Dr. Hank Rawlins is the Technical Director of eProcess Technologies with 26 years’ experience in the upstream oil & gas industry. Hank is responsible for development programs in Facilities Sand Management, Produced Water Treatment, and Compact Separations Systems. He blogs weekly and teaches courses in these areas. Connect with Hank on LinkedIn, Twitter, website, or at [email protected].
? Technical Authority - Facilities Sand Management · Produced Water Treatment · Compact Separation Systems
7 年Thank you José Gregorio Márquez Albornoz. Many years ago (1997) we were asked to remove sand from very heavy oil (~350 cP viscosity) to protect a twin-screw multiphase pump. This was done using a bank of multiphase desanders and in our opinion the separation would be poor. However, for the client their goal was to remove particles at 1/2 the screw gap in order to protect the pump. We met that criteria and the project was a success.
Corporate Production Engineering, Sr. Production and Flow Assurance Engineer at Pluspetrol
7 年Dr. Rawling, as always, you share information very useful and interest. From my point of view, another aspect to be considered is related to identifying which particle diameter can be handled by surface devices (pumps), such as Twin-screw multiphase pumps (MPP), this in the field under the philosophy of multiphase flow stations. This could give us the minimum size that must be handled to avoid the erosion of screw and therefore MPP efficiency reduction.
Ingeniero de procesos en Techint Ingeniería y Construcción
7 年Excelente, tenemos un proyecto de tratamiento de agua de producción y estos artículos nos han ayudado mucho! Excellent, we have a production water treatment project and these items have helped us a lot!
Consultant Engineer at Xodus Group
7 年Another excellent article Hank. I definitely agree with the concept of removing only the harmful particles. We have been asked a few times to assess erosion downstream of filters when the mean sand size is less than 5 microns ... the answer is almost certainly zero. There is a definite industry tendency to over-engineer. In our experience there is still a shortage of information on the minimum sand size that will cause erosion (although the people at Tulsa University are doing a good job of addressing this). Smaller particles are definitely less damaging and you often see a steep drop off in erosion below 100 microns . It is often assumed that acoustic sand detectors struggle to pick up sand particles smaller than about 50 microns because small sand doesn't hit the pipe walls with much force. This is based on a reasonable amount of testing. I would be a bit cautious about assuming that below 100 microns, sand causes no erosion in liquid flow (not what you said, but how I initially read it!). There is published data to show significant erosion in water with 53 micron sand (e.g. SPE 90734), admittedly at high velocities and high concentrations. Just be careful how you pick your limits ... 5 or 10 microns ... definitely, 20 or 30 ... maybe? .... 50 or 60 ... hmmm...
Lecturer at ITBA
7 年Excelent Hank!