Criticality Testing of Shale Shaker (3)

As a result of differences in the design of shale shakers and front hoods/enclosures, it was difficult to test all shakers within the exact same parameters. It was determined that each shaker had to be tested as dictated by the differences in design of each unit (Fig. 10).

 front hood/other enclosure of shale shaker.
Fig. 10—Ventilation flow rate; vendors-recommended value (blue) and test-optimized value (red) with and without front hood/other enclosure of shale shaker.

Related readings:

HVAC and WE.

All solids-control solutions were tested at the manufacturers’ recommended HVAC extract air-flow rates. With the smoke test and VOC readings, the HVAC extract air flows were thereafter adjusted to obtain the best possible WE atmosphere in the room.

Because of the installation of a filter in the test center’s HVAC system, the highest achieved ventilation flow rate after the installation of the filter was 7400 m3/h, and not 120 00 m3/h, which was the initial HVAC capacity. As a consequence, it was not possible to determine the test-optimized value for one of the shakers tested later in the test period. Test-optimized value is the ventilation flow rate that gave the best achieved WE results for the shale shakers.

Solids control unit

The vendors specification for HVAC requirement (blue columns) for the tested units, the test-optimized value (red columns), and the corresponding ventilation flow rates for shakers tested with and without front hoods or other enclosures are displayed in Fig. 10.

One shale shaker had an open design, and a provisional front hood was built by the supplier during the test. However, it was not possible to determine the test-optimized value resulting from high evaporation level and limitations in the HVAC system, and the test-optimized value is set to be equal to the vendors recommendation because this was the highest achieved ventilation flow rate for this unit; thus, it was not possible to obtain a satisfactory WE at this ventilation flow rate. The ventilation requirement for this unit is higher than the vendors-recommended ventilation flow rate.

One shale shaker had a front hood as extra equipment and was tested with and without a front hood; even with a front hood mounted on the shaker, measurements displayed that the unit required a higher ventilation flow rate than recommended by the vendor.

One shale shaker was tested in a prototype enclosure with the front hatches open and closed. It was not possible to test this unit without the enclosure because the shakers’ connection to the HVAC system was part of the enclosure. It turned out that this vendor recommended a higher ventilation flow rate than test results revealed that this unit actually needed.

One solids-control unit that is enclosed and derived from vacuum technology obtained an excellent WE atmosphere at a low ventilation flow rate, and the vendor-recommended ventilation flow rate is sufficient.

Only one shaker was tested without a front hood/enclosure and with a supplier-recommended ventilation flow rate that proved to be insufficient. Test-optimized ventilation flow rate for this shaker was almost double the supplier-recommended value.

A surprising discovery during the HVAC tests is that several of the shaker vendors did not know the ventilation requirement for their shaker; one vendor believed that the shaker needed a high ventilation flow rate when measurements showed that it needed a low rate. Other suppliers realized that they had underestimated the required ventilation flow rate for their shakers.

The comparisons of ventilation flow rates for the shakers revealed that there was insufficient accordance in vendor-recommended values and test-optimized values (Fig. 10).

Comparisons of HVAC measurements indicate that the installation of a front hood/enclosure on the shakers had a better effect on the level of OV/OM/VOC than increased ventilation flow rate, and that the effect of the front hood/enclosure seemed to be improved when sufficient ventilation flow rate was applied simultaneously.

WE.

The objective of the WE test was to verify if the supplier- recommended HVAC flow rate was sufficient to achieve an acceptable chemical exposure in close proximity to the shaker. The levels of VOC, OV, and OM were measured to quantify the chemical exposure.

OV and OM were sampled with a pump. Two parallel samples were taken at the sampling points, which were in front of and on the right side of the shaker. VOC was sampled with the directreading instrument MiniRAE 3000, and sampling points were in front of and on the right and left sides of the shaker. Representative, selected test results from the WE test are displayed in Figs. 11 and 12 (measurements in front of shaker and measurements on the right side of shaker, respectively).

In Fig. 11, the OM levels from the shaker with the highest level are truncated. The actual values for low- and high-ventilation flow rates, given as exposure indices [exposure level (E)/ AC)], would have been 337 and 297, respectively.

In Figs. 11 and 12, the average OV, OM, and VOC levels from each of the shakers have been compared. The results are presented as exposure indices (e.g., measured E/AC) for measurements obtained at the front and the right side of the shakers, respectively.

The results given in Figs. 11 and 12 have to be interpreted with caution. However, they show considerable and consistent differences in OV, OM, and VOC levels between the five shale shakers.

stainless steel shaker screen

None of the shale shakers fulfilled the design criteria (1/6×AC). However, there was one shale shaker that came very close to having emissions in the low category (1/6 to 1/2×AC) for both OV and OM. Another shale shaker had OV measurements in the high category (1/5×AC). These two shale shakers were designed with a technical barrier of Priority 1 (efficient enclosure of emission sources). The first of these shakers represents new technology that is derived from vacuum methods, and the second shale shaker uses conventional technology equipped with an enclosure.

On the basis of the results from the five shakers tested, one enclosed solids-control unit was highly recommended because of its ability to control the emissions of OV and OM at the pollutant source, resulting in low measured concentration in the vicinity of the shaker. The second-best shale shaker was also equipped with an enclosure providing an enclosed handling of the emissions, although the test results show higher OV and OM concentrations in the atmosphere than expected.

detail of shaker

The other three shale shakers need to develop further toward a closed system in which the emissions can be better controlled. It was not possible to fulfill the design criteria, nor the AC, with an open shaker. Even with a hood, the tested shakers did not have acceptable emission levels, especially for OV. A recommendation is to dedevelop the open and semiclosed shakers toward better/full enclosure to handle and control the OV and theOM emissions at their source.

Comparisons of the WE measurements revealed that more open shaker designs caused higher levels of OV/OM/VOC in the atmosphere. All conventional shakers in the test were encouraged to develop toward a more closed design.

A positive effect of the test was that the suppliers now see WE performance as an area of competition. These WE tests have stimulated innovation to improve the WE. All participants with the potential to improve their performance on HVAC and WE have designed and produced front hood or other means of enclosure and have performed smoke tests of their shakers with front hoods/enclosures on their own sites.

Noise and Vibration.

SWL has been measured to obtain the noise emission from one shaker. The area noise level in a shale shaker room has then been calculated from the measured SWL. See the results of the shakers SWL at 90 and 100% of maximal drillingfluid- flow rate, and shakers running dry without drilling fluid (Fig. 13).

Comparison of measured SWL for the different units.
Fig. 13—Comparison of measured SWL for the different units.

The small size of the test cell caused challenges related to measurement accuracy, but after noise absorbents were mounted on the test-cell walls, noise-measurement conditions were improved.

The SWL results given in Fig. 13 were the basis for the calculation of predicted SPL for comparison with the area noise levels of a shale shaker room. Only one of the tested shale shakers has the potential to meet the required area noise limit of 85 dBA in a shaker area.

Three of the tested shale shakers have the potential to meet an area noise level of 90 dBA, and one of the shakers operates at more than this highest allowable limit. Noise at these high levels has a large impact on operational restrictions for individuals to fulfill their personal-exposure requirements.

Vibration-measurement results are reported according to standards NORSOK S-005 and S-002. Vibration measurements were also performed on the mud container below the shaker and were compared with Category 3, and the measurement made on the shaker skid (the highest-level measurement) was compared with Category 4. See Fig. 14 for a comparison of the vibration measurements.

vibration motor for shale shaker
Vibration Motor

All measurements are within acceptable limits. The shaker representing new technology has the lowest vibration levels on the skid. However, on the reference point, the difference between the units was small, suggesting a good effect of the vibration isolators used on all units.

Comment on Results.

To facilitate access to the shakers’ performances in the various aspects of the shaker test, a ranking was performed by the discipline specialists on their respective areas. Because of an anonymity agreement with the shaker vendors, this ranking is not included in this publication.

Conclusions

Drilling-Fluid-Processing Rate.

There is a significant difference in the drilling-fluid-processing capacities; that for oil-based drilling fluid spans from 3950 to 1150 LPM, and corresponding results for water-based drilling fluid are 3320 and 900 LPM.

The filtration efficiency of the shakers was examined by PSD analysis, first with the Malvern that was inconclusive and then by FBRM that produced useful data. The advantage demonstrated by the FBRM analysis indicates that this instrument should be used more in future PSD analysis, and this experience may be useful for both drilling operations and further-research projects.

The adherence of drilling fluid on cuttings was measured as OOC. This is of economic and environmental importance, because less drilling fluid lost as adherence on cuttings implies a reduced loss of drilling fluid and less drilling waste. All shakers showed good results relative to adherence-of-drilling-fluid-on-cuttings  OOC corresponding measurements from 1990s operations, which demonstrates the improvement of solids-control equipment and better procedures for shaker operation since that time.

The challenge of representative drilling-fluid and cuttings samples should be taken into account when reading the results, and a larger number of drilling-fluid and cuttings samples should be collected and analyzed to achieve more-reliable filtration results.

The screen-wear registration displayed variation in the durability of the screens because some screens were more prone to develop holes. The screen data collected are too detailed to incorporate in this publication, but further testing would benefit from allocating resources on consecutive registration of screen wear because shaker screen data are complex.

The leakage rates from the shakers were satisfactory for all participants, but experience performed during the test brings out the importance of checking this aspect before a solids-control unit is set in operation.

The maintenance and operation checks revealed that the overall result for the participating shakers is that the user friendliness is prioritized in the design. Some shakers have minor issues related to the change of screens and cleaning.

The introduction of the front hood on the shakers seems to significantly improve the WE atmosphere in the test room. This test of shakers in an enclosed environment indicates that the WE challenges in shaker rooms are very difficult to resolve with an HVAC solution only. The real exposures of personnel working in shaker modules will depend on such details as working operations, time spent in the module, and personnel protections.

The new method used for the first time on the shaker test, in which an active sampling of OV and OM is performed in parallel with direct-reading instruments for VOC to monitor the variations in concentrations of organic vapor and the chemical WE as a consequence of changes in ventilation flow rate and front hood or enclosure, represents technology development. This method was used for the first time in the shaker test, and the possibility to obtain real-time data of the VOC level was used as a navigational tool during the test, because results from OV and OM samples
were available only after some time. The VOC levels were used to determine the required HVAC flow rate during the tests.

The recommendation from the HVAC-test results is that the conventional shakers should be equipped with a front hood, and the extract ventilation from the shaker should maintain an underpressure inside the shaker and preferably a 1.5-m/s air velocity through any openings. The front-hood design should be further developed to improve the effect of capturing the OV and OM.

The control of hazardous emissions in the WE shall be achieved by technical measures/barriers (in order of priority):

  • Efficient enclosure of emission sources.
  • Efficient extraction/exhaust-ventilation systems to remove pollutants near the source.
  • General ventilation/dilution of contaminants.

Noise tests revealed that only one of the tested shakers had the potential to meet the required area noise-level limit of 85 dBA, three shakers had the potential to meet the highest allowable area noise-level limit of 90 dBA, and one shaker exceeded this highest allowable limit. All measurements of vibration were within acceptable limits.

The shale shaker test triggered competition among the equipment suppliers and stimulated technology development and product improvement. This was especially the case for the solutions related to HVAC and WE. The publication of the anonymous test results will make benchmarking possible for the participants.

Tests of the various aspects of shaker performance called for the development of new test methodology. Covering different disciplines, the test initiated by the rig modification project was a result of a multidisciplinary cooperation. The internal specialists were representing the discipline areas of drilling and well facilities, WE technology, operation and maintenance including HVAC and drilling fluids. Other internal contributors were representing the contracts department, the legal department and the department for intellectual-properties rights. The external participants are from the test center, drilling-fluid supplier, five shaker vendors and their distributors in Norway, external laboratory, and consultant companies for measurement of HVAC, occupational hygiene, and noise/vibration.

During the phases of this project, lessons have been learned that have given increased competence on test methodology. With many specialists working together on the same test, new ideas have been conceived, and some of them have resulted in product improvements of the solids-control equipment. Some shaker vendors have discovered that there was potential for improvement on their shakers, and the test experience and results have become a basis for product improvement.

Because all shakers were tested with test conditions as equal as practically possible and the only variable factor was the shakers, the test has produced a unique database of comparable results. The test results are valid for the test conditions, and performance may be better on other tests, but the unique aspect was that these results were truly comparable results and revealed the differences in shaker performance.

The variation in performance among the shakers supports the legitimacy of the test, and it demonstrates the need for a standardized-test methodology for shakers. The test methodology is considered the main outcome of the shaker test, and this publication may be a step toward a standardized methodology applied on this and similar equipment. In the future, a standardized test methodology for shakers would facilitate the selection of the most suitable equipment for the shaker customers.

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