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Sand screen

DSS dynamic self-cleaning sand control screen

Structure
 

DSS dynamic self-cleaning sand control screen, as shown in Figure 1, consists of a base pipe, supporting drainage layer, the filter medium and an outer protective pipe.
The base pipe is in line with the API standard 5CT tubing or casing.
The supporting drainage layer is composed of some stainless steel rods welded on the base pipe along the axial direction, forming a supporting skeleton and numerous drainage channels.
The filter medium is composed of hundreds of continuous stainless steel wire with a special processing technology. It is wrapped in supporting drainage layer.
Outer protective pipe is made by punching stainless steel plate.
 
 
Work principle
  
The reservoir sands will hang in the filter medium( see Figure 2), but not form plug in the screen surface when they flow out from the well with the formation fluid. So the oil and gas wells can maintain production under the condition of no pressure loss. When the sands achieve" saturated" state in the filter medium, subsequent reservoir sand will also accumulate in the screen surface, so that a differential pressure will be formed inside and outside the screen. The differential pressure pushes the filter medium peristalsis to the medial, thus destroying the formed plug. Namely: sand accumulation - forming differential pressure - filter medium peristalsis - the destruction of plug - differential pressure reducing - establishment of new plug - the formation of new differential pressure - filter medium again peristalsis - the destruction of plug. In this go round and begin again process, the blocked layer will be destructed constantly, while the filter medium can maintain" self-cleaning" in the creeping process.


Benefits
  • High Plug Resistance
    The creep deformation generated by the external pressure can destroy the blocked layer, while the filter medium can maintain "self-cleaning". In addition, the filter medium has a good “dirt-holding” capacity. So the screen is not easy to be blocked. Dynamic screen plug resistance ability is superior to conventional screen. Figure 3 shows the comparative experimental curves of the DSS screen and the metal mesh premium screen. When the metal mesh premium screen’s flow-thru is 781 litres, the blocking pressure is up to 10.32MPa. When DSS dynamic self-cleaning screen’s flow-thru is 781 litres, the blocking pressure is only 1.86MPa.The experimental curves indicates that the DSS dynamic self-cleaning screen’s plug resistance ability is much better than that of the conventional screen.
  • Good Mechanical Properties
    The tensile strength and torsional strength of the base pipe can be retained more than 85% of un-perforated pipe. The burst resistance is more than 1100psi. The collapse strength is more than 4000psi.
  • Strong Corrosion Resistance
    The support drainage layer, the filter medium and the outer protective pipe are made of stainless steel. The DSS dynamic self-cleaning screen has good corrosion resistance.
  • Erosion Resistant Ability
    Because the DSS dynamic self-cleaning screen is not easy to be blocked, the rapid flow won’t be formed in the un-plugged area. The erosion on the screen reacted by the flow will be greatly reduced.
  • Applications
    The DSS screen is designed for the Stand-Alone Screen Completion. It can be applicable for wells that the sand median grain size (d50) is over than 100μm. In the presence of heavy oil, fine sands or excessive clay, the DSS screen will perform much better than the conventional screens.