Patent Publication Number: US-6702011-B2

Title: Combined nitrogen treatment system and coiled tubing system in one tractor/trailer apparatus

Description:
FIELD 
     This invention relates, generally, to the treatment of oil and gas wells using nitrogen to increase the production capability of the wells, and specifically, to providing on a single tractor/trailer combination, all of the equipment accessories to pump nitrogen through a coiled tubing into the wells being treated. 
     BACKGROUND OF THE INVENTION 
     It is known in the art to provide work over operations using gaseous nitrogen to remove sand and/or water or other impediments to production. The prior art has not recognized that a single tractor trailer unit can be provided with all of the equipment and accessories for running a nitrogen service in combination with a coiled tubing unit to treat such wells. The prior art typically brings two tractor trailer assemblies to the well to be treated, one having a coiled tubing unit, and one having the nitrogen unit. Because of the duplicity of the tractor trailer units, this has caused a doubling of the transportation costs, a doubling of the personnel required to have the units arrive at the well, and a doubling of the number of personnel required to run this service. 
     It is of the primary object of this present invention to provide a combined tractor trailer unit which utilizes a single tractor and a single trailer to provide a service for treating wells with a combined tractor trailer unit through which gaseous nitrogen can be pumped. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is an elevated, schematic view of a tractor unit which can be used in accordance with the present invention; 
     FIG. 2 is an elevated, pictorial view of a trailer unit which can be used in accordance with the present invention with the tractor illustrated in FIG. 1; 
     FIG. 3 illustrates, in block diagram, the various systems which are used in accordance with the present invention to treat a well with nitrogen; 
     FIG. 4 is an elevated, diagrammatic view of an oil or gas well which is being treated with nitrogen from the coiled tubing unit in accordance with the present invention; 
     FIG. 5 is a pictorial view of three nitrogen generators which can be used as a substitute for the liquid nitrogen tank; 
     FIG. 6 is a pictorial view of a unit using membrane technology to pull gaseous nitrogen out of the atmosphere; and 
     FIG. 7 is an elevated pictorial view of a plurality of tanks used for storing compressed nitrogen gas. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED MODE OF THE INVENTION 
     Referring now to FIG. 1, a tractor  10  having either a gasoline engine or a diesel engine is illustrated and which is used to pull the trailer  20  illustrated in FIG.  2  and which also uses its engine to drive all of the components which are illustrated in FIG.  1 . and FIG. 2, on the tractor  10 , and the trailer  20 , respectively. The chassis  11  of the tractor  10  may be, for example, a Freightliner. The tractor  10  also has a hydraulic tank  12  and a tank holddown unit  13  which secures the hydraulic tank to the chassis. A hydraulic pump  14  has a coupling and a drive mechanism connected to its one end. The coupling  16  is connected into a transfer case and drive shaft mechanism  17 . A hydraulic pump  18  is one of many hydraulic pumps in the tractor assembly  10  and also includes various hydraulic pumps within the assembly  19 . It should be appreciated that all of the mechanisms illustrated with the tractor  20  in FIG. 2 are driven by hydraulic pumps located on the tractor chassis  10 . The assembly  15  is a hydraulic pump which includes a clutch pulley being driven by the engine located within the tractor  10 . The tractor bed  21  has an assembly  22  which is used to connect the tractor to the trailer as illustrated in FIG.  2 . 
     Referring now to FIG. 2 in more detail, mounted on the trailer bed  30  which is connected to the tractor bed  21  by way of the mechanism  22 , is a cryogenic nitrogen tank  32 . As is well known in this art, liquid nitrogen has a greatly reduced volume compared to the volume of gaseous nitrogen. Nitrogen, when frozen to −320° F., is a liquid and accordingly, it is much preferred to transport the liquid nitrogen to the well site to provide additional volume of nitrogen gas which is to be pumped into the well. Also mounted on the tractor bed  30  is a control cabin  34  in which the electrical and hydraulic units  36  are controlled by a human operator. The nitrogen system  38  which is described in more detail hereinafter is also located on the tractor bed as is a heat exchanger  40  which is used to heat up the pumped liquid nitrogen to a temperature which causes the liquid to become gaseous, which can then be pumped into the well. The piping system  42  enables the gaseous nitrogen to be pumped into one end of the coiled tubing to allow the gaseous nitrogen to be pumped out of the other end of the coiled tubing. 
     An injector unit  44 , also described in more detail hereinafter, is situated on the tractor bed floor. A hydraulically driven crane  46  is also situated on the tractor bed floor for situating the coiled tubing injector  44  immediately above the well being treated. A hose reel  48  and a coiled tubing reel  50  are also situated on the tractor floor. A goose neck  52  is also situated on the tractor floor adjacent the coiled tubing injector system  44  for feeding the coiled tubing from the reel into the injector. A stripper  54  is located on the lower end of the coiled tubing injector system  44  for enabling the coiled tubing to be placed into the well being treated. A BOP unit  56  is also located on the tractor floor to be used in shutting in the well to be treated, if needed. 
     Referring now to FIG. 3, there is illustrated in block diagram some of the components which are illustrated in FIGS. 1 and 2. The liquid nitrogen tank  32  has its output connected into the input of a hydraulic pump  64  whose output is connected into the input of the heat exchanger  40  illustrated in FIG.  2 . The tractor engine  70 , which may be either gasoline powered or diesel powered has a hot water line  72  connected to its radiator and which provides hot water to the heat exchanger  40 . A return line  74  from the heat exchanger returns the water from the heat exchanger back into the radiator of the tractor engine  70 . The pump  64  is designed to pump the liquid nitrogen having a temperature near −320° F. into the input of the heat exchanger  40 . Such pumps are commonly available in the industry for pumping liquid nitrogen. As the liquid nitrogen is pumped through the heat exchanger  40 , the heat exchanger will cause the liquid nitrogen to rise above a gasification point which is near 0° F. so that the output from the heat exchanger is gaseous nitrogen. A gas line  76  can then return a portion of the gaseous nitrogen through the valve  78  back into the return line  80  which enables some of the gaseous nitrogen to be returned into the top of the nitrogen tank  32 , if and when desired. The output of the heat exchanger  40  is also coupled into one end of the coiled tubing illustrated in the box  82  through as many valves as are necessary for turning the nitrogen on or off to the coiled tubing  82 . One such control valve is illustrated as valve  84 . The valve  84  would preferably be a three-way valve which can either cut the gaseous nitrogen off so that it would not flow either into the coiled tubing or the valve  78  or would flow into only one or the other of the coiled tubing  82  and the valve  78 . 
     A hydraulic pump  90  is connected into a hydraulic motor  92  which is used to drive the chains of the injector  44  which can either move the coiled tubing into the well being treated or pull the coiled tubing out of the well being treated, as desired, depending on the direction of the chain rotation. 
     Another hydraulic pump  96  drives a motor  98  to drive the crane  46  illustrated in FIG.  2 . 
     Another hydraulic pump  100  drives a motor  102  which in turn drives any one or more miscellaneous items requiring a hydraulic activation as desired. 
     It should be appreciated that the tractor engine  70  drives each of the hydraulic pumps  64 ,  90 ,  96  and  100  as shown by the line  106 . Coming off of the tractor engine  70 , the hydraulic pump  64 ,  90 ,  96  and  100  are preferably driven by one or more belts which can be used with clutch pulleys as desired. A compressor unit  108  which is also driven by the tractor engine  70  is run off of the drive line  106  to assist in keeping the liquid nitrogen down to its desired temperature. 
     It should be appreciated that while the tractor engine  70  is obviously and desirably located on the tractor, and the coiled tubing, the injector, and the crane, as well as the liquid nitrogen tank  32  are preferably located on the tractor, most of the other items identified in FIG.  3  can be found on either the tractor and/or the trailer as desired. The important feature of this invention is to recognize that all of the items shown in FIG. 3 are located on a combined tractor/trailer configuration which does not require the use of either another tractor or another trailer. 
     Referring now to FIG. 4, there is a simplified schematic illustrating the process contemplated by this invention for treating a producing oil or gas well which has, for whatever the reason, either quit producing or has started producing with a reduced volume of oil or gas. The tractor trailer illustrated in FIGS. 1 and 2 is delivered to the site of the well  110  which typically is cased with steel casing  112  and which has a string of production tubing  114  running down to the pay zone  116  in the surrounding formation and which has a pair of packers  118  and  120  which straddle the pay zone. With such wells, the casing  112  has a plurality of perforations  122  which enable the oil or the gas to leave the pay zone and come into the interior of the well. The production tubing  114  has a screen or other holes in it  124  which allow the oil or gas to leave the pay zone  116 , come through the perforations  122  and enter the production tubing  114  which then allows the oil or gas to travel to the earth&#39;s surface. 
     There are various things which can cause the well in question to quit producing at a rate which it has been experiencing before. There can be sand which enters through the perforations and the holes in the production tubing which plug it up substantially and reduce the amount of oil or gas being produced. Another problem which exists in addition to the sanding problem is the existence of water which may be sitting on top of the oil or gas being produced. Since many of the pay zones contain water, and because of the weight of the water sitting on top of the oil or gas being produced, the oil or gas simply will not proceed up to the surface. To overcome either one of these problems, it is desirable to pump gaseous nitrogen down through the production tubing  114  to push the sand and/or the water out of the production tubing string  114  and back up through the annulus between the steel casing and the production tubing. This can be accomplished either by not using the production packer  118  or by having bypass valves which pass through the production packer  118  and allow the sand and/or the water to be produced up the annulus through the earth&#39;s surface and once again, place the production of the pay zone back to what it was before the problem occurred. In an alternative mode, the packer  118  can remain in the cased borehole as illustrated, unbypassed, and the gaseous nitrogen when bubbled out of the end of the coiled tubing beneath the perforations, will drive sand and/or the water back to the earth&#39;s surface through the production tubing itself. 
     To accomplish all of this, it is desirable that the gaseous nitrogen be introduced from the earth&#39;s surface by passing the gaseous nitrogen through the coiled tubing from the coiled tubing reel located on the bed of the tractor. To get the coiled tubing  130  into the interior of the production tubing string  114 , the coiled tubing injector  44  is moved by the crane unit  46  to be immediately above the Christmas Tree  130  which is, of course, the well-known oilfield apparatus which is placed at the top of the producing well  110 . The coiled tubing  130  is run through a well-known stripper into the interior of the Christmas Tree  130  and enters the interior of the production tubing string  114  without causing any leaks of any substance within the well to be vented into the atmosphere. The gaseous nitrogen is then caused to exit the lower end of the coiled tubing  130 , usually as the coiled tubing is being pushed into the production tubing, or can be turned on after the coiled tubing is in place in the well, if desired. The gaseous nitrogen then causes any water and/or sand which is plugging up the system to be routed through the annulus between the production tubing and the casing to cause the sand and/or the water to be removed from the system, which allows the well to again become productive. While the injector system  44  is shown in block diagram, such injector systems are well-known in the art as described and illustrated in U.S. Pat. No. 5,566,764, the disclosure of Which is incorporated herein by reference. Such systems normally involve the use of one or two rotating chains which can be caused to rotate in one direction to grab a hold of the coiled tubing and inject it into the tubing within the well, or by reversing the direction of the motor, the tubing can be pulled out of the well. As illustrated in FIG. 3, the hydraulic pump  90  drives the motor  92  which causes the one or more chains to rotate within the injector  44 , for example, as illustrated with respect to the aforementioned U.S. Pat. No. 5,566,764. 
     It should be appreciated that although the present invention contemplates using the liquid nitrogen tank  32  illustrated on the trailer  20  to generate gaseous nitrogen, the invention also contemplates that instead of using the tank  32  illustrated in FIG. 2 as a source of liquid nitrogen, there are additional sources which can be utilized. For example, nitrogen generators can be used, shown in FIG. 5, which extract nitrogen from the atmosphere which can eliminate the costs of transporting and filling nitrogen tanks. Some of such nitrogen generators utilize a membrane, shown in FIG. 6, which allows nitrogen-rich air from the earth&#39;s atmosphere to be continuously fed into bundle housing. The air reaches the center of the bundle of membrane fibers which at that point, consists mostly of gaseous nitrogen. The nitrogen collects in the mandrel at the center of the bundle. As the air passes through the bundle of membrane fibers, the oxygen and other fast gases pass through the wall of the membrane fibers as they go through the fibers to be collected at the end. Oxygen and the other fast gases are continuously collected and are moved from the bundle, thus leaving the nitrogen available to be used for injection into the well being treated. By stacking a plurality of such nitrogen generators, available volumes are provided which have an increased flow capability. 
     In an alternative mode, albeit not as preferred as either the liquid nitrogen or the nitrogen generator modes, the gaseous nitrogen source can be one or more tanks of compressed nitrogen gas such as the tanks  200 ,  202 ,  204  and  206  illustrated in FIG.  7 .