Shaker Users Guide
All solids removal systems should have enough shale shakers to process 100% of the drilling fluid circulating rate. For expensive wells, an evaluation should be conducted to determine the drilling fluid processing system needed to minimize drilling and disposal costs. On the basis of this evaluation, the number, type, and configuration of shaker(s) can be chosen (see Selecting Shaker Screens discussed in Chapter 4). The following guidelines address the installation, operation, and maintenance of shale shakers.
In all cases, the owner's manual should be consulted for proper installation procedures. If unavailable, the general guidelines below may be helpful:
- Low places in the flow line will trap cuttings. The How-line angle should be such that solids settling does not occur. In general, establish a I -inch drop for every 10 feel of flow line.
- When using a back tank, also known as a possum belly, the flow line should enter the bottom to prevent solids from settling and accumulating. If the flow line enters the top of the back tank, it should be extended to within one pipe diameter of the flow line from the bottom.
- Rig up with sufficient space and approved walkways around the shaker(s) to permit easy maintenance.
- Branch tees, Figure 5-1, should be avoided. Solids preferentially travel in a straight path resulting in uneven solids distribution to the shale shakers.
- Ensure equal fluid and solids distribution when more than one shaker is used (Figure 5-2).
- Options shown in Figures 5-2 and 5-3 are better than the distribution system shown in Figure 5-1.
- FIGURE 5-3
- An optional top delivery (Figure 5-3) prevents cuttings from settling in the back lank.
- A cement bypass that discharges outside the active system is desirable.
- Mount and operate the shale shaker where it is level. Otherwise, both the solids and fluid limits will be reduced.
- Motors and starters should be explosion-proof. Local electrical codes must be met. Be sure the proper sized starter heaters are used.
- Provide the proper electrical voltage and frequency. Low line voltages reduces the life of the electrical system. Low frequency reduces the motion and lowers the capacity of the shale shaker.
- Check for proper motor rotation.
- Check for proper motion of the shale shaker deck.
- Check drive belts for proper tension according to manufacturer's instructions.
- Screens should be installed according to manufacturer's instructions.
- Provide a wash-down system for cleaning.
- Water-spray bars, if installed, should provide only a mist of water—not a stream of water.
- Do not bypass the shale shaker screens or operate with torn screens; these are the main causes of plugged hydrocyclones. This results in an accumulation of drilled solids in the drilling fluid. Also, do not empty the back tank into the pits (for cleaning purposes, etc.) since this is considered a form of bypassing the shale shaker.
- All drilling fluids that are not processed by solids removal equipment and are intended to be added to the active system, should be screened by the shale shakers to remove undesirable solids. Specifically, this includes drilling fluid delivered to a location from remote sources.
- For double-deck shale shakers, run a coarser mesh screen on the top deck and a finer mesh screen on the bottom The coarser screen should be at least two standard mesh sizes coarser. Watch for a torn bottom screen and replace or patch torn screens at once. During normal drilling operations, cover at least 75% to 80% of the bottom screen with drilling fluid to maximize utilization of available screen area. Properly designed flow-back pans may improve shaker performance. (Gumbo shakers mounted above as an integral part of linear shale shakers are not called doubledeck shale shakers—although the operation guidelines above still apply.)
- For single-deck shale shakers with multiple screens on the deck, run the same mesh screens throughout. If coarser screens are necessary to prevent drilling fluid loss, run the finer mesh screens closest to the back tank. All screens should have approximately the same size openings. For example, use a combination of market grade (MG) 100 mesh (140 microns) and MG 80 mesh (177 microns), instead of MG 100 mesh (140 microns) and MG 50 mesh (279 microns). Under normal drilling conditions, cover at least 75% to 80% of the screen area with drilling fluid to properly utilize the screen surface area.
- Spray bars (mist only) may be used for sticky clay to aid conveyance, which reduces whole drilling fluid loss. High-pressure washers should not be used on the screen(s) while circulating because they disperse and force solids through the screen openings. Spray bars are not recommended for weighted or oil-based drilling fluids.
- For improved screen life with nontensioned screens, ensure the components of the screen tensioning system, including any rubber supports, nuts, bolts, springs, and so forth, are installed and properly operating. Install screens according to the manufacturer's recommended installation procedure.
- Lubricate and maintain the unit according to the manufacturer's instructions. Some units are self-lubricating and, therefore, this step should be skipped.
- Check the screen tension one, three, and eight hours after installation and hourly thereafter.
- Check the tension of drive belts and make any adjustments according to the manufacturer's instructions.
- If only one deck of a multiple-deck shaker is used, make sure other tension rails are secured.
- Wash screen(s) at the beginning of a trip so as not to allow fluid to dry on the screen (s). Do not empty the back tank into the active system or the sand trap below the shaker. This results in plugged hydrocyclones downstream and/or an increase in drilled solids concentration in the drilling fluid.
- Inspect screens frequently for holes and repair or replace any that are torn.
- Check the condition of vibration isolators and screen support rubbers and replace if they show signs of deterioration or wear.
- Check the fluid bypass valve and the area around the shaker screens for leaks.
- Remove drilling fluid accumlation from vibrating bed, vibrators, and motors. Caution:
the reason for analysis, the goal is to determine how the shaker and screen combination perform in a particular application. The data can be used to optimize performance of a given machine and assist in determining the number of shale shakers needed. By far the most frequent reason for analyzing performance is to compare one brand of shale shaker with another. This requires that test conditions remain constant and representative of field performance.
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