Patent Publication Number: US-7901492-B2

Title: Pipe separator inlet

Description:
BACKGROUND OF THE INVENTION 
     1. Technical Field 
     The present invention concerns a pipe separator or, more specifically, the inlet to such a separator. The pipe separator comprises an extended tubular body with a diameter that is principally the same as or slightly larger than the diameter of the supply pipe of the pipe separator. 
     2. Description of the Related Art 
     Applications for patents for pipe separators of the above type were first submitted by the applicant in the present case in 1996. One of these patent applications is the applicant&#39;s own international patent application PCT/NO 03/00265, which shows such a separator. 
     Pipe separators are very effective for separation of fluids with non-mixable fluid components and also represent a simple, structurally light solution compared with conventional gravitational separators. In some situations in connection with the separation of fluids, for example an oil, gas and water flow with a high gas content, plug flow may occur, one reason being design-related conditions, which may reduce the separation in the separator. The present invention represents a solution that will completely eliminate such plug flow. 
     SUMMARY OF THE INVENTION 
     The present invention is a device in connection with a pipe separator. The pipe separator comprising an extended tubular body having a diameter that is principally the same as or slightly larger than the diameter of the inlet pipe of the pipe separator. The invention is characterized in that a separate gas manifold is arranged in connection with the inlet pipe. The manifold has a number of vertical degassing pipes connected to the inlet pipe immediately ahead of the inlet to the separator and end in an overlying, preferably slightly inclined gas collection pipe. The manifold is designed so that the gas will be diverted up through the vertical degassing pipes and collected in the gas collection pipe for return to the outlet pipe after the separator or transport onwards to a gas tank or gas processing plant. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The present invention will be described in further detail in the following using examples and with reference to the attached drawings, where: 
         FIG. 1  is a longitudinal sectional view of part of a separator with an inlet in accordance with the present invention; 
         FIG. 2  is a longitudinal sectional view of part of a separator with an alternative embodiment in accordance with the present invention; and 
         FIG. 3  shows another example of an alternative embodiment of part of a separator in accordance with the present invention. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       FIG. 1  shows, as stated above, part of a pipe separator  1  with an inlet in accordance with the present invention arranged in connection with a supply pipe  3  for a multiphase flow, for example oil, water and gas. 
     The flow pattern in a multiphase flow upstream of the pipe separator is often gas/fluid plug flow if the gas/fluid composition and the design of the supply pipe are unfavorable. In the figure, the fluid plugs  4  are shown as darker parts, while the gas takes the form of gas bubbles  5  in a light color or white. 
     The present invention involves “puncturing” the gas bubbles and removing them so that the gas phase is mainly collected in a gas collector and the fluid phase remains in the main pipe. This is achieved by means of a gas manifold  2 , arranged in connection with the inlet. The manifold  2  comprises a number of vertical degassing pipes  7 , which are connected to the supply pipe immediately ahead of the inlet to the pipe separator and which end in a slightly inclined gas collection pipe  6 . The gas is thus diverted up through the vertical degassing pipes and collected in the gas collection pipe  6 . 
     Tests have shown that this is an effective way of eliminating plug flow while also ensuring that a constant fluid flow is supplied to the pipe separator  1 . The gas that is removed can bypass the pipe separator via the gas collection pipe  6  and be added to the oil phase straight after the separator, or it can be transported onwards to a gas tank or the like. The system can be designed so that the gas removal is driven by the normal pressure drop in the system. 
       FIG. 2  shows an alternative solution in which the supply pipe  3  with the gas manifold  2  is raised to a level (in the area  9 ) above the pipe separator  1 . By raising the gas manifold above the pipe separator, as has been done here, the gas is forced along the gas path, i.e. up into the gas manifold  2 . 
     Moreover, as shown in  FIG. 3 , the diameter of the supply pipe at the inlet to the separator, under (at  8 ) the last of the degassing pipes  7  of the manifold, may have an enlarged diameter, for example equivalent to the diameter of the pipe separator. By increasing the pipe diameter in the last part of the gas manifold so that the fluid speed in the pipe is reduced, gas that is not separated can flow back to the last degassing pipe  7 . 
     The purpose of the design of the gas manifold in accordance with the present invention is to:
         1. Separate out the gas phase from a gas/oil/water well flow in a simple manner that does not subject the multiphase flow to high shearing forces. High shearing forces are normally negative for the separation.   2. Ensure the fluid flow has the correct phase in the separator, i.e. water-continuous flow for the water phase and oil-continuous flow for the oil phase. This reduces mixing in the separator inlet and reduces the formation of multiple dispersions in the mixing process in the inlet.