Abstract:
A method of reducing leakage from a pipeline includes the steps of: pumping fluid through a pipeline using at least one pump, the at least one pump comprising a reversible, positive displacement fluid pump; detecting a leak in the pipeline downstream of the pump; reversing the at least one pump to draw fluid out of a downstream section of the pipeline; and redirecting the fluid being drawn from the pipeline into a storage container.

Description:
TECHNICAL FIELD 
     This relates to a method of pumping fluid through a pipeline, such as a subsea or surface pipeline to reduce leakage from the pipeline in the event of a pipeline leak. 
     BACKGROUND 
     When transporting crude oil or other hazardous fluids through a pipeline, there is a risk of leaks from the pipeline or at a pipeline station. This can result in environmental damage, whether the leak occurs in a subsea or surface pipeline. 
     U.S. Pat. No. 3,702,744 (Brown et al.) describes a pump connected to a pipeline in an environmentally sensitive area. The pump is activated in the event of a leak to pump fluids out of the pipeline and into a container. U.S. Pat. No. 3,741,233 (Smith, Jr.) describes another system in which fluid flowing along a pipeline is redirected into a container in the event of a leak. 
     SUMMARY 
     There is provided a method of reducing leakage from a pipeline, comprising: pumping fluid through a pipeline using at least one pump, the at least one pump comprising a reversible, positive displacement fluid pump; detecting a leak in the pipeline downstream of the pump; reversing the at least one pump to draw fluid out of a downstream section of the pipeline; and redirecting the fluid being drawn from the pipeline into a storage container. 
     According to an aspect, the at least one pump may comprise two or more pumps connected in parallel to the other pumps. The two or more pumps may be separately isolatable from the pipeline. 
     According to an aspect, the method may further comprise the step of providing a bypass line in parallel with the at least one pump. 
     According to an aspect, detecting a leak may comprise receiving a signal indicative of a leak from a leak detector. 
     According to an aspect, the pipeline may be undersea, and drawing fluid out of the downstream section further comprises creating a vacuum in the downstream section that draws water into the pipeline through the leak. 
     According to an aspect, redirecting the fluid into the storage container may comprise closing a valve on the pipeline and opening a valve to the storage container. 
     According to an aspect, the method may further comprise the step of programming a controller to receive a signal indicative of a leak from a leak detector to, upon receiving a signal indicating a leak from the leak detector, reverse the at least one pump to pump fluid from a downstream portion of the pipeline and to redirect the fluid into the storage container. 
     According to an aspect, the at least one pump may be a progressive cavity pump. 
     According to an aspect, there is provided an apparatus for reducing leakage from a pipeline. The apparatus comprises at least one pump connected to pump fluid through a pipeline. The at least one pump comprises a reversible, positive displacement pump. The at least one pump pumps fluid in a downstream direction in an operating mode and pumping fluid in an upstream direction in a reverse mode. A storage container is connected to the pipeline by a first valve upstream of the at least one pump. A second valve is connected to the pipeline and positioned upstream of the storage container. A leak detector is connected to the pipeline to detect a leak in the pipeline downstream of the at least one pump. A controller is connected to receive signals from the leak detector and to send control signals to the at least one pump and the first and second valves. The controller is programmed with instructions to, upon receiving a signal indicating a leak from the leak detector, open the first valve, close the second valve and activate the reverse mode of the at least one pump to pump fluid from a downstream portion of the pipeline into the storage container. 
     According to an aspect, the at least one pump may be one of a progressive cavity pump, a twin screw liquid pump, or a multiphase pump. 
     According to an aspect, the at least one pump may comprises two or more pumps connected in parallel to the other pumps. There may be pump valves that separately isolate each pump from the pipeline. 
     According to an aspect, there may be a bypass line in parallel with the at least one pump. 
     Other aspects will be apparent from the description and drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       These and other features will become more apparent from the following description in which reference is made to the appended drawings, the drawings are for the purpose of illustration only and are not intended to be in any way limiting, wherein: 
         FIG. 1  is a schematic view of a pumping station 
         FIG. 2  is a schematic view of the pumping station connected to a pipeline. 
         FIG. 3  is a schematic view of an alternative pumping station. 
     
    
    
     DETAILED DESCRIPTION 
     The method described herein applies generally to pipelines, such as subsea or surface pipelines, where the surface pipelines may be above ground or buried. While the type of pipeline considered here is one in which the flow of fluid is generally controlled from control rooms, the steps described herein may be applied to other known types of pipelines that use a pump to transport the fluid. 
     Referring to  FIG. 1 , there is shown an apparatus for reducing leakage from a pipeline  12 . As shown, two pumps  14  are connected to pump fluid through pipeline  12 . The number of pumps may vary and there could be one pump  14 , or more than two pumps  14 . Pumps  14  are preferably reversible, positive displacement pumps and may be, for example, progressive cavity pumps, twin screw liquid pumps, or multiphase pumps. Pumps  14  pump fluid in a downstream direction under normal operating conditions. In the event of a leak, pumps  14  may be switched to a reverse mode, where fluids are pumped out of the downstream portion  16  of pipeline  12 . 
     The number of pumps used will depend on the amount of fluid to be pumped, the desired flow rate and pressures, the amount of redundancy desired or required by the user, and the pump specifications. Pumps  14  may be in a rack arrangement, or arranged vertically, to reduce the footprint, or may be spaced out along a ground surface. In the event that there are multiple pumps, a manifold may be designed and connected at each end of pumps  14  to ensure an appropriate distribution of fluid among pumps  14 . Preferably, there is a bypass line  18  that allows fluid to bypass pumps  14  altogether, such as if pumps  14  cease operation at the same time. This allows fluid flow to continue and prevents a pressure build-up due to other sources of fluid pressure or pumps in the system. The number of bypass lines  18  may vary, but generally speaking the cross-sectional area of bypass line(s)  18  should be equal to or greater than the pipeline  12  connected to pumps  14 , or multiple pipelines if arranged in such a manner. Each pump  14  and bypass line  18  preferably have valves  20  that allows them to be isolated independently of the other pump  14  or bypass line, as shown in  FIG. 1 . 
     There is a storage container  22  connected to pipeline  12  by a valve  24  that is upstream of pumps  14 . Pipeline  12  has an additional valve  26  connected to pipeline  12  that is upstream of storage container  22 . Storage container  22  may take various forms and will vary in size depending on the amount of fluid that it is anticipated it will need to hold. As will be understood, the distribution of valves depicted in  FIGS. 1 and 2  is only an example, and may vary depending on the overall design. Another example is shown in  FIG. 3 , where container  22  is connected to pipeline  12  by more than a single valve and by more than one path. 
     Referring to  FIG. 3 , if pump  14  is a multiphase or gas pump, it may be necessary to circulate fluid, or ensure sufficient fluid circulates, to keep the relevant portions of pump  14  cooled and lubricated as is known in the art. A recirculation path  23  is provided that may be used to accomplish this. Recirculation path  23  is also connected to container  22 , which may be used to supply liquid if necessary, such that container  22  may serve more than one purpose. Recirculation path  23  may also have pressure relief valves  25  to release any excess pressure and avoid damaging to the equipment. 
     Referring to  FIG. 2 , the various components are preferably controlled by a logic controller  28  that is connected to, for example, the pumps  14  and valves  20 ,  24  and  26 . It will be understood that controller  28  may control all or only some the various components could also be controlled manually and that controller  28  may issue alarms rather than instructions to equipment. Logic controller  28  is also connected to a leak detector  30  that is designed to detect the presence of a leak in the pipeline downstream of pumps  14 . In the event of a leak  32 , which may result from various types of failures of pipeline  12 , controller  28  will send signals to close valve  26  to prevent more fluid from flowing down pipeline  12  and open valve  24  in anticipation of receiving fluid from the downstream portion  16  of pipeline  12 . Controller  28  also sends a signal to pimps  14  to switch from an operative mode to a reverse mode, such that a negative pressure is applied to the downstream portion  16  of pipeline  12 , resulting in fluids being pumped away from failure  32 . If pipeline  12  is an underwater pipeline, this may result in water being pulled into pipeline  12 , which creates a buffer and further reduces the risk of leakage from pipeline  12 . 
     The method described herein uses one or many pumps  14  installed connected to one or more pipelines  12 . As shown in  FIGS. 1 and 2 , the pipeline  12  is a split pipeline and there are two pumps  14 , however it will be understood that there could be more than one pipeline  14  and any number of pumps  14 . In such a situation, there would likely be a manifold that allowed the operator to control the flow of fluid from pumps  14  and through pipeline(s)  14 . As shown, pumps  14  are complete pumps  14  that include the motor, cable, motor lead extension, motor protector complete, etc., which are preferably installed inside the pipeline. This may be done in parallel or series depending upon the requirements. by installing pumps  14  inside pipeline  12 , the number of points for leakages to occurs is reduced. As will be described below, pump  14  is powered by a cable  37 , which is run into pipeline  12  to connect with pump  14  using a connection  36  similar to a connection used when installing pumps  14  downhole. As these connections  36  are rated for pressures that are much higher than those encountered in a pipeline, the likelihood of a risk from pumps  14  is relatively low. 
     The method may be used to reduce the footprint that is inherent in a large station, reduce the risk of a leak at the stations, and reduce the amount of leakage should there be a leak downstream from the leak. The pipeline  12  may be on surface or in a subsea environment. The apparatus is preferably based on a downhole type of positive displacement pumps, such as a twin screw liquid or multiphase pump. These pumps are preferred due to their ability to pump in reverse or forward. The same results can be achieved with centrifugal pumps, but these cannot be run in reverse in this orientation. However, using any positive displacement pumps  14  can be used to achieve the following. 
     As shown, two pumps  14  are connected in parallel by splitting the pipeline  12  at the station, generally indicated by reference numeral  10 . Pumps  14  may be driven by a VSD (Variable Speed drives— 35 ), which may be outside the pipelines  12 , and may be hundreds of feet away if connected to pumps  14  using a down hole cable  37 . The VSD can be located far away or close to the station depending on power availability and cable capability to transfer power. For example, the down hole cable presently used for down hole pumps can go to 16,000 feet or even deeper allows a user to set the VSD far away from the pumping station if required. The MLE (Motor Lead Extension) comes out around the motor, the pump to the discharge point and then connects to the cable and comes out through the well head to the VSD (variable speed drive) or controls. 
     If more than one pump  14  is used, it allows one pump  14  to remain idle while the other one or more pumps  14  carry the load, or they may each contribute to the flow through pipeline  12 . By controlling the capacity of each pump, In the alternative two together or all together could do a percentage of the 100% capacity of the flow line capacity. 
     In a preferred embodiment, the various components of pumps  14 , such as the motor, cable, pressure compensation system, gear box if applicable, Motor Lead Extension, pot head, sensors, any capillary lines for multiphase applications for lubrication complete are preferably inside the split pipelines  12  at station  10  such that only the cable would be visible outside of pipeline  14 . 
     Referring to  FIG. 3 , cable  34  may come out through a simple well head connection  36  as used in down hole pumps. There are many types of well heads in the field where the cable comes out through sealed systems and that are rated for very high pressures. This is sealed similar to a down hole pump cable coming out of a down hole installed pump. In a subsea environment, pumps  14  can be landed vertical or horizontal. On surface, pumps  14  can installed slanted or horizontal. 
     By using this design, the risk related to leaks from mechanical seals or any other leaks at station  10  is reduces, as everything is canned inside the pipe lines. Another major advantage is that, should there be a leak anywhere in the pipe line hundreds of kilometers away, pumps  14  can be made to run in reverse and the fluid collected back at another contained location for emergency on a temporary basis. This will stop the leak at a distant pipe line leak  32  within minutes. This can be set to automatic settings. The containment tank  22  is preferably designed to hold any emergency fluid being pumped back. Once there is a leak in the pipeline  12 , the fluid coming from the source of fluids (e.g. oil field or other area) is first shut down and then these station pumps are stopped and run in reverse switching the intake into discharge and discharge into intake in a very short time. Due to lack of pressure at the leak area, the leak will be stopped relatively quickly. The concept here is the capability to pump in reverse. In a subsea environment, when it pumps in reverse the pump will pull all fluids out and then it will start pulling sea water up through leak  32 . At that point one can shut down and ensure leak is completely arrested. Pressures can be compensated and maintenance can commence. Before the containment tank there is a valve  26  that will be open in normal operation. When fluid is pumped in reverse valve  26  will close to allow fluid to enter the containment tank  22 . 
     This system can be used for gas, liquid or multiphase as long as the medium can be pumped using a pump or compressor. 
     In this patent document, the word “comprising” is used in its non-limiting sense to mean that items following the word are included, but items not specifically mentioned are not excluded. A reference to an element by the indefinite article “a” does not exclude the possibility that more than one of the element is present, unless the context clearly requires that there be one and only one of the elements. 
     The following claims are to be understood to include what is specifically illustrated and described above, what is conceptually equivalent, and what can be obviously substituted. The scope of the claims should not be limited by the preferred embodiments set forth in the examples above.