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This institution reserves the right to refuse to accept a copying order if, in its judgment, fulfillment of the order would involve violation of copyright law. Geothermal Resources Council Transactions,Vol. 24, September 24-27, 2000 Field Test of LEAMS Drilling and Well-Test Separator JohnFinger,’ Allan Sattler, Gary Whitlow, Ron Jacobson’, Tom Champness*, D.B. J ~ n gW.T. , ~ Howard3, Paul Spielman4 ‘Sandia National labora~ories, *Drill Cool Systems, 3Two-PhaseEngineering & Research, 4 COperating ~ ~ Company, ~ Inc. ABSTRACT The LEAMS (Low EmissionsAtmosphericMetering Separator) is a new device that improves the separation of vapor, liquid, and entrained solids during discharge of a geothermal well. This paper describes the first field test of the prototype, which showed greatly reduced carryover compared to a conventional cyclone separator. Back~round When a geothermal well is tested or produced, the fluid is sometimes released as a two-phase mixture of vapor and liquid. Controlling this discharge requires passing it through a steam separator, so that the vapor can be vented to atmosphereand the liquid can be disposed or re-injected to the reservoir. In the conventional and widely used cyclone separator, a significant part of the liquid can be entrained or suspended in the vapor and borne away from the separator to fall on the surrounding area. This “carryover” can contain silica, salts, boron, arsenic, and, in the case of hydrogen sulfide abatement, concen~atedcaustic and chemical by-products that may be harmful to agriculture, equipment, or the environment and can be expensive to remediate. In a cyclone, or centrifugal, separator (Figure 1) fluid produced from the well enters the separator tangentially to the cylind~calsurface through the h o ~ z o n tube ~ l about halfway up the side of the tank. The fluid then forms a vortex inside the separator with the steam escaping out of the open top of the tank and the liquid collecting in the bottom of the tank, where it drains out through a line that usually leads to a weir box for measu~mentof the flow rate. The LEAMS (Low Emission Atmospheric Metering Separator, Figure 2, overleaf) is a new concept in flow treatment that uses internal baffles and diverters to reduce the amount of carryover emitted during tes~ng.’D e v e ~ o p ~ eof n ta LEAMS prototype was funded by the Geothermal Drilling Organization Figure 1. Test conf~~uration: cyclone separator on left, LEAMS on right. (GDO)as a cost-shared project between the U. S. Department of Energy (through Sandia National Laboratories) and industry (Two-Phase E n g ~ n ~Drill ~ ~Cool g , Systems, and Cos0 Operating Company). After completion of this prototype by DCS and TPE, Sandia managed a field test to evaluate its efficiency at the Cos0 geothermal field. Field test plan The general nature of the test was to produce the same amount of fluid through a standardcyclone separator and through the LEAMS and to measure the amount of carryover from each device. Canyover would be measured both directly, by using a probe that measures particle flux in the exhaust streams and by placing rain gauges around the separators during the tests, and indirectly, by measuring the amount of liquid draining into the weir box from the sep~ators.In the latter ~ e a s u ~ ~ ethen t , amount of brine flowing from the separators would show how 67 Finger, et. a/. Clean Steam outlet , Figure 3, JonasParticle Monitor mounted in LEAMS exhaust me~~; (sensing element of Probe is at left end of j ~ s f ~ ~ note anemometer above Jonas Probe). Figure 2. Schematic layout of LEAMS (from Reference 1). much liquid was removed from the exhaust streams and thus by Tmt procedure and results: Test set-up began on 1 Feb 00 subtraction,because the total liquid content of the fluid is known and continued on 2 Feb, with the first flow test on the afternoon of from the enthalpy, the amount of liquid Iost to carryover. 2 Feb. FIow through the cyclone Separator reached a maximum I n s t r u ~ e n ~ t and i ~ ndata c ~ l ~ ~ ~ tData i o ncollection : for value of 2 7 7 , ~~u n dper s hour (277 KPH) with an averagevalue this test used the following transducers supplied by Sandia: of 270 KPH?which produced abundant carryover but no flow through the weir box. In fact, after more than Go hours of flow, so * Lip pressure in the James tube (which gives totaf mass flow little liquid had collected in the bottom of the separator that it never rate into the separator), reached the level of the drain line leading to the weir box. It is * Pressure and temperature in the blooie line, likely that the vortex inside the cyclone wauld have continued to Pressure differential across the orifice plate (which gives empty the liquid, no matter how long flow lasted. total mass flow from the well, In a more qu~lita~jve evaluation, the ~~evajling south-southeast wind blew a plume of steam and liquid away from the Liquid level in the weir box ~ w h ~ cgives h flow rate for liqcyclone walking underneath this plume was very much like uid collected in the separator), being in a mode~ate to heavy rain. Because rain gauges were e FIow rate into weir box (same as above, except measured with placed at the four cardinal directions (N,E, S, W), there was a magne~cflow meter on the drain line into the weir box), not a gauge directly underneath the plume, but the north gauge Paddle meter in the overflow line into the weir box, collected 0.8 inches of water in just over two hours of flow. e Sound pressure level (LEAMS is designed to be quieter than There were also large puddles of standing water on the gravel pad around the separators. the cyclone), The conclusion was that carryover was essentially l ~ e U-tube manometer to measure internal pressure in the that is, all the liquid produced into the separator was carried LEAMS, away by the steam. Given a total flow rate of 270 KPH and an 0 Anemometer in the exhaust stream, and enthalpy of 997 ~ T U / ~ bfor m the fluid, the liquid-fraction flow * Data acquisition and display system based on L a b V I ~ ~ rate of 41 KPH at atmosphe~~c pressure can be calculated. Using water density at a temperature of 2W°F (boiling point of software. water at the wellsite elevation of 3721 feet), the brine flow rate Jonas, Inc. of Wilmington,Delaware, supplied a particle moni(which we take to be the minimum carryover, as discussed tor (Figure 3) used to measure size, number, and distribution of above) is equivalent to 85 gallons per minute (gpm), water droplets at specific points in the exhausts of the LEAMS Data from the Jonas probe indicated liquid flow out the top and the cyclone. Jts principle of operation is to measure the imof the cyclone to be 74.6 KPH, or almost twice the liquid fracpact (kinetic ener~y)of each particle on a probe and then, by tion of the fluid at atm~sphericpressure.2 A larger amount of using a separate measurement of velocity from an anemometer, liquid is to be expected because the two-phase fluid is being calculate the mass of each particle. This point mass-flow rate discharged into cooler atmos~he~e (ambient air tem~erature can then be ~ n ~ ~over ~ the t etotal d open area of each separatur ranged from 57-80*F during the tests), which will lead to conto get totd mass flow of liquid particles out ofthe separator (total densation of some part of the vapor. Transient conditions and open areas = cyclone 109.3 ft2,LEAMS - 121.O ft2). 0 - 68 ~ , Finger, et. a!. sucked inward by the venturi effect, thus drawing cool air into the LEAMS. Minor leaks in the LEAMS were observed both before and during testing; which meant that measured brine flow under-representedthe actual amount of liquid, but thc lcaks wcre fairly small, estimated at 2-5 gpm from water level drawdown. The LEAMS test was highly encouraging from the point that almost no droplets could be felt in walking under the plume, c o n ~ ~ by ed the fact that no measurable water collected in the rain gauges during total flow duration of more than two hours. The particle-size distribution data indicate very strong weighting of the emitted LEAMS particles toward smaller sizes, with peaks at 50 and 75 microns and a rapidly decreasing tail-off at increased particle size. The majority of emitted particles may evaporate mostly in the immediate vicinity of the stack. The fact that the particle probe detected a few particles in the 500micron range is inconsistent with the failure to feel any droplets or to detect any in the rain gauge. The fact that no solid material (crystallizeddebridscale) was felt or detected in the vicinity of the LEAMS during the five LEAMS tests strongly suggests that any solid particulate emitted from the LEAMS is not carryover. Despite the uncertainties described above, all of the measured test parameters were reasonably consistent with each other and the LEAMS was clearly much more effective than the cyclone at removing carryover from the exhaust vapor. Sound pressure level measure~entsshowed the LEAMS to be somewhat noisier than the cyclone. Sound pressure levels were 97 dB for the cyclone and 100dB for the LEAMS at equal distances. The LEAMS was expected to be quieter than the cyclone, because of the baffles and diverters inside the box, but it may be that vibration in the flat-panel sides of the separator accounted for the increased noise. This notion is supported by the measurement of I. 1-psi internal pressure in LEAMS and by observation of standing waves in the steam plume when it traveled down the sides of the LEAMS. The inward deflection of the segmented rubber gasket at the James-tube entry port would also expose a larger opening and provide a noise path. Although the measured difference is small, the entry-port situation is readily remedied. After completion of the LEAMS testing, the flow line was reattached to the cyclone (because Cos0 Operating Company has to leave it that way) and an additional test was run in the cyclone. The additional cyclone test was performed to get another data point for the particle monitor, because its ex~apola~on from a point measurement to an area measurement depends on uniform flow over the outlet area. This appeared to be reasonably accurate for the LEAMS, but was not true at all for the cyclone. Because of the swirling effect of the fluid’s tangential entry, most of the particles leaving the cyclone came out near the periphery, so that the original reading taken there would overstate the total amount of carryover. This was verified by readings taken approximately 213 of a radius in from the edge; values there were much less than those near the edge and were, ~ t s the LEAMS. Bein fact, less than the ~ e ~ s u r e m eabove cause the flow varies so greatly across the exhaust area of the cyclone, extrapolation of the Jonas probe’s point readings to the entire area is problematic. If enough point readings could be taken to thoroughly map the velocity distribution across the limited instrumentation, however, make the magnitude of this increased quantity uncertain. Limited particle-size distribution data for the cyclone show peaks at one and two hundred microns, with nuiiierous particles from 500 microns to 3000 microns (Reference 2). Marble size droplets were observed under the exhaust plume of the cyclone. During the cyclone test, control valves from the well were t ~ o ~ l back e d in an attempt to reach a flow rate low enough that no liquid was being carried from the separator. Although Jonas probe data indicated a reduction in carryover at the lower flow rate, wellhead pressures became high enough that the valves could not be closed any further. Data were also incomplete because the James tube flow measurement requires a minimum flow rate to read properly, and at this rate a signitkant amount of liquid was still coming from the cyclone. [It should be mentioned that cyclones are generally designed to be “as large as practical” and the size l i ~ t a t i o nis a matter of the largest dimension that can be transported on highways by trucks. The maximum diameter of a cyclone is usually limited to 12 feet, so if the steam flow to be measured is larger than can be handled by this size, the only alternative is to use more than one cyclone in parallel.] At this point, testing on the cyclone was suspended and test instrumentation was moved to the LEAMS. First flow test on the LEAMS was on 3 Feb and testing continued on 4 February. The LEAMS was operated for five flow intervals with the Jonas particle probe at different locations in the exhaust stream. At each of the probe locations, liquid mass flow rate was substantially reduced from the cyclone measurements. Average exhaust measurements showed liquid mass flow of 37.3 KPH (compared to 74.6 KPH for the cyclone), but particle size was much smaller than in the cyclone, which allowed the droplets to evaporate before falling to the ground. Total liquid output from the LEAMS was, however, greater than the cyclone. In addition to the liquid in the exhaust, the brine output from the LEAMS ~ o u g the h weir box was greater than 50 KPH for each of the five flow intervals. There are two major possibilities for this result: the LEAMS created more condensation within its box than the cyclone did in its chamber or the particle-monitor measurements were in substantial error. Possible reasons for particle-monitorerror are discussed below, but the measurements are generally assumed to be correct. Since the liquid fraction of the steam was approximately41 KPH, and there was no liquid output through the weir box, the liquid output of the cyclone exhaust must have comprised entrained liquid and condensed vapor, in roughly equal amounts. This means that all minerals or impurities in the liquid escaped from the cyclone and were deposited in the area. The LEAMS, however, is specifically designed to separate larger particles of entrained liquid, so it is reasonable to believe that most of the liquid in its exhaust stream is condensed vapor, which would contain no impurities. This still indicates that somewhat more liquid was condensed in the LEAMS than in the cyclone, which could have at least three causes: the larger surface area of the LEAMS, higher pressure inside the LEAMS (see discussion of noise below), and the larger opening where the James tube enters the LEAMS. This entry port had a segmented (split) rubber gasket around the James tube, but the gasket was clearly being 69 Finger, et. a/. cyclone opening, then a weighting factor for point readings at any position could be derived, but time and test budget did not permit that many data points. More resolution of rain-gauge measurements also resulted from placement of 11 gauges around the northeast and northwest quadrants of the cyclone during its second test. Prevailing wind was once again from the southeast, so gauges in the northeast quadrant collected no measurable water, but in the northwest six gauges had amounts ranging from 0.2 to 1.8 inches after only 25 minutes of flow. Conclusions All qualitative (perceptionof carryover from walking under steam plume) and quantitative (rain gauges, exhaust particle, brine flow) measurementsconfirmed that the LEAMS was more effective than the cyclone at removing carryover. There is some uncertainty in the test data, primarily in interpretation of the particle flow measurements. Calculation of the particle size and, thus, mass flow rate is clearly dependent on knowledge of the particle velocity. In the test data, the particle velocity was taken to be the same as the vapor velocity measured by the anemometer. Because there is no correction for slip between the droplets and the vapor, the particle size could be understated, and this effect would be greater with larger particles than with smaller. This means that exhaust liquid flow from the cyclone, where particles were larger, could be understated relative to the LEAMS or, in other words, that the LEAMS could be an even greater improvement in carryover reduction than indicated by the data. A summary of lessons learned is the following: LEAMS Design Features The LEAMS system is designed to be environmentally friendly while drilling ahead with air/mist/foam drilling fluid or while testing a well. It is based on the premise that no existing separator can perform all these functions - large flows into existing, inadequate separators may result in very significant amounts of carryover, leading to incidents such as spraying a hillside or farmer’s field with brine. The LEAMS, designed for a very high separating efficiency in a packaged, modular design, will save time and money while drilling and testing. Some of the LEAMS design features were exercised during this test, others were not. The LEAMS is designed to be: LEAMS worked very well at reducing carryover. LEAMS seems to have more steam condensation within the separator than a cyclone, causing the higher liquid output. Even though this might be simply remedied or mitigated, it is not clear whether, from the operator’s standpoint, it is important. 1. Multipurpose - adequate for most drilling blowdown and flow test situations without rigging down and converting from the “drilling” cyclone to the “testing” cyclone. If the LEAMS is to be used in extremely large wells, additional separator modules can be bolted on. The well tested has relatively high enthalpy, with a steam fraction approximately 85%. It is unclear how the LEAMS efficacy will extrapolateto wells with higher or lower steam fractions. 2. Stable - the combination of fluid impact and wind makes some cyclones unstable; it is not unknown for one to blow off the location. The energy of the well effluent slug is dissipated by the LEAMS design, low center of gravity, and added weight from the mud pit section. 3. Portable - the LEAMS modules (designed to fit in a standard 7.5’ by 39’ shipping container) were assembled without difficulty at the test site. 4. High capacity -the LEAMS worked over a range of outputs, with good results on a relatively large well (270 KPH)down to a throttled flow rate that was less than half that figure. remove particlesto 5 . Efficient at separation- the below 50 microns in size. In this test it is likely that condensed was emitted from the stack for both separators.There was no physicalObservation Of Or large drop1etsfrom the LEAMS. The particle size distribution measurement from the LEAMS is probably not related to its separation efficiency and is in fact in some contradictionwith observations. 6. Quieter - its baffles and diverters should reduce noise, but the LEAMS was X“M3what nosier than the cyclone- The inward sucking of the segmented gasket mentioned above might have increased the LEAMS noise. The particle-probe method of measuring liquid content of a mixed stream is critically dependent on knowing the velocity distribution and whether particles are uniformly scattered across the exhaust area of the device being tested. Steam pressure inside the LEAMS indicates caution when feeding a larger or more energetic well into this separator. Acknowledgements Sandia is a multiprogram laboratory operated by Sandia Corporation,a Lockheed Martin company,for the United States Department of E~~~~~under contract DE-AC04-94AL85000. Personnel from Cos0 Operating Company, Drill Cool Systems, and Two-Phase Engineering were extremely cooperative and helpful duringperformance of this test. References I . Jung, D. B., Howard, W. T.; June 2000; “LEAMS Low Emissions Atmospheric Metering Separator for Drilling and Well Testing”; Proceedings of World Geothermal Congress 2000; Beppu, Japan. 2. Jonas, 0. and Machemer, L.; February 2000; “Cyclone and LEAMS Separation Efficiency and Moisture Carryover Test at the Cos0 Geothermal Power Site”; report for Sandia National Laboratories from Jonas Inc., I I I3 Faun Road, -Wilmington DE 19803. 7. “Power plant friendly” - the LEAMS is designed to minimize or even eliminate any carryover.No carryover was seen. The steam should be clean. 70