Sieve apparatus and method for use of same

#The present invention regards a sieve apparatus. More particularly, it regards an apparatus and a method for sieving or screening a material such as, but not limited to, a drilling fluid containing drilling mud and drilling particles or drill cuttings.

#Separating solids from fluid flows by passing a fluid through a filtration or screening device having perforations of a size that retains the solids on the screen surface instead of passing them through, is a well known technology. Some fluid flows contain other substances that cause solids to agglomerate or adhere to each other or to a screen surface, which results in the formation of bridges across the screen openings and clogging of the screen. These problems often occur during well drilling, where a drilling fluid or “mud” is circulated into the well.

#During drilling, drilling fluids are continuously circulated between the well bore and the surface in order to remove drilling particles, also called drill cuttings, from the drill bit. The drill cuttings are carried to the surface by the drilling mud, where it is separated from the drilling mud. The drilling mud is then recirculated into the well, to the drilling operation. Drilling mud is expensive, among other things, and it is therefore desirable to re-use as much of this as possible. The drilling mud is kept as clean and free of contaminants such as drill cuttings and foreign matter, as possible. Drilling mud is typically cleaned by a succession of several types of equipment, including vibratory screening devices generally termed “shale shakers”.

#In the following there is described a non-limiting example of a preferred embodiment illustrated in the accompanying drawings, in which equivalent or similar parts are indicated by the same reference number, and in which:

#FIG. 1 is a cross-sectional view through the vertical plane of a sieve apparatus in accordance with the present invention;

#FIG. 2 is a top view of the apparatus in accordance with the present invention;

#In the figures, reference number 1 denotes a sieve apparatus arranged to separate e.g. drilling particles from drilling mud, and which includes two sets of screening devices 2, each of which is constituted by a stationary inlet screen cloth 3 and an endless screen cloth 5. The two screening devices 2 are arranged one above the other. Each screen cloth 5 is mounted between a first drum 7 and a second drum 9. Underneath a section of each screen cloth 3, 5 there are ultrasound sources 11 arranged in containers 13 and 15, respectively.

#A person skilled in the art will appreciate that the apparatus 1 of the embodiments is illustrated by schematic drawings only, and that the apparatus in an operating situation must be connected to a control system and a power supply that are known per se. Although the apparatus 1 is shown as having two screening devices 2, it is understood that that apparatus may equally well comprise one screening device or three or more screening devices. Likewise, it is understood that one or more of the endless screen cloth(s) 5 can be replaced with fixed screen elements, across which the material to be screened is conveyed by mechanical means (not shown) or by gravity.

#FIGS. 1 and 3 show a side view and a partially sectioned view, respectively, of an apparatus 1 in a configuration in which the stationary inlet screen cloth 3 is arranged to receive material containing drilling mud and drilling particles, and separate at least some of the drilling mud from the drilling particles. This is achieved by the ultrasound sources 11, which are disposed in the container 13 (see FIG. 5), generating acoustic pulses that are transmitted to the inlet screen cloth 3 and the material. Tests have shown that in this configuration, the acoustic pulses are highly effective in separating drilling mud from solids, and that an equivalent conventional shale shaker would have to generate gravitational forces in the order of 20 G, which is approximately four times greater than that which is feasible through use of conventional shale shakers. Thus, the acoustic pulses acting on the screen cloth 3 are highly effective when it comes to breaking the bonds between both drilling mud and drilling particles, and drilling mud and the screen cloth 3. The drilling mud that is liberated from the material on the screen cloth 3 and flows through this, is collected by a collecting tray 17 arranged on the underside of the inlet screen cloth 3, and which directs the separated drilling mud through outlet 30 on to further treatment (not shown) outside of the sieve apparatus 1. The drilling material is carried onwards across the endless screen cloth 5, now with a reduced content of drilling mud due to passing the inlet screen cloth 3. In a section near the first drum 7 ultrasonic sources 11 are provided in a container 15A section near the first drum 7 is provided with ultrasound generators 11 in a container 15. The ultrasound sources generate acoustic pulses that act on the screen cloth 5 and the drilling material, causing substantial parts of the drilling mud still bound to the drilling material received on the screen cloth 5 to be liberated from the particles of the drilling material, and to flow through the screen cloth 5 and be collected on a collecting tray 17′, to be brought out of the sieve apparatus 1 for further treatment. The drilling material conveyed on the screen cloth from the first drum 7 to the second drum 9 falls off the screen cloth 5 at the second drum 9, and is carried out of the sieve apparatus 1 via a discharge tray 19, through outlet 32 and further to collection for transport for on-shore disposal.