Abstract:
A mobile high horsepower rating natural gas compression package is presented. The apparatus includes a trailer having a flexible pre-cambered frame configure to absorb shock during transport and dissipate vibration during operation, and an inflexible sub-skid attached to the flexible frame. A high horsepower rating engine driven compressor is attached to the sub-skid while ancillary compression package components are attached to the flexible frame. An arrangement of break flanges is employed to permit relative motion between the compressor and the ancillary compression package components during transport and operation. The advantages are derived from a more reliable unitary mobile natural gas compression package attained through: lower transport costs and reduced transport delay, improved site access windows, lower site preparation, setup, teardown, and site reclamation costs, and reduced site preparation, setup, and teardown time delays. Overall production losses and operating costs are reduced through improved reliability and operating performance.

Description:
FIELD OF THE INVENTION 
       [0001]    The invention relates to mobile natural gas compression packages, and in particular to a wear and tear resistant mobile gas compressor. 
       BACKGROUND OF THE INVENTION 
       [0002]    Natural gas compressors are employed in oil and gas production to provide a pressure boost for conveying natural gas along a natural gas aggregation, transport, and distribution network. Natural gas compressors are typically used on-site close to a producing well, and can also be employed at any point in the network between producing wells and the final point of consumption/sale. It is typical for natural gas compressors to be associated with network nodes. Producing wells and aggregation network nodes are often located in geographically remote areas. 
         [0003]    Natural gas compressors range in horsepower rating. Mobile or semi-permanent compressors generally vary between one hundred horsepower to over one thousand horsepower. The horsepower rating generally varies with the physical size of the compressor. Scalability issues plague mobile compressors. Mobile compressors having a horsepower rating above five hundred horsepower suffer from disproportionately high maintenance and are found to be unreliable given potential production losses. To date, mobile compressor applications have been limited to short term use as a substitute during semi-permanent compressor maintenance. 
         [0004]    In providing high horsepower rating natural gas compression services, generally accepted principles in the art point to the use of semi-permanent installations. In some applications, semi-permanent installations are generally not cost effective for short term or restricted access use, as a lot of specialized equipment and highly skilled personnel has to be brought to, and from, a geographically remote site. Some natural gas production projects are not undertaken or suffer from reduced profitability due to higher site preparation, transportation, installation, teardown and site reclamation costs associated with semi-permanent installations. 
         [0005]    There is a need in to mitigate the above-mentioned issues in order to improve operating performance and thereby minimize costs. 
       SUMMARY OF THE INVENTION 
       [0006]    In accordance with an aspect of the invention there is provided a mobile unitary high horsepower rated natural gas compression package including: a trailer having a pre-cambered frame configured to flex during transport and in response to vibration during operation, and an inflexible sub-skid attached to the flexible frame; an engine driven compressor fixedly attached to the inflexible sub-skid; a plurality of ancillary compression package components attached to the flexible frame; and an arrangement of break flanges configured to permit flexure between the compressor and at least one of the ancillary compression package components. 
         [0007]    In accordance with another aspect of the invention there is provided a horizontal gas scrubber affixed to the sub-skid. 
         [0008]    In accordance with a further aspect of the invention there is provided a cooler and an adjustable cooler support. 
         [0009]    In accordance with a further aspect of the invention there is provided an expansion building. 
         [0010]    In accordance with a further aspect of the invention there is provided a pullout arrangement providing extra working area about the compression package during operation, while adhering to transport standards. 
         [0011]    In accordance with a further aspect of the invention there is provided a disk style muffler providing sound deadening in use while adhering to transport standards. 
         [0012]    In accordance with yet another aspect of the invention there is provided a removable disk style muffler aligned with the at least one removable roof panel of the building. 
         [0013]    The advantages are derived from a more reliable compression package, which reduces downtime and operating costs. 
     
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0014]    Referring to the drawings wherein like reference numerals indicate similar parts throughout the several views, several aspects of the present invention are illustrated by way of example, and not by way of limitation, in detail in the figures, wherein: 
           [0015]      FIG. 1  is a side elevation view of a flexible pre-cambered trailer frame for a mobile natural gas compression package in accordance with an embodiment of the invention; 
           [0016]      FIG. 2  is a back end view of the flexible trailer frame shown in  FIG. 1 ; 
           [0017]      FIG. 3  is a top plan view of a housing configured to protect mobile natural gas compression package components installed on a flexible trailer frame from the elements; 
           [0018]      FIG. 4 ; is a side elevation view of the trailer having a compression components on an inflexible sub-skid; 
           [0019]      FIG. 5  is a top plan view of an arrangement of stringers of the inflexible sub-skid shown in  FIG. 5 ; 
           [0020]      FIG. 6  is a top plan view of a combined arrangement of stringers of the flexible trailer frame and of the inflexible sub-skid; 
           [0021]      FIG. 7  is a top plan view of interconnected compression package components; 
           [0022]      FIG. 8  is a top plan view a mobile compression package housing having a pullout arrangement; and 
           [0023]      FIG. 9  is a sectional view showing an extended pullout. 
       
    
    
     DETAILED DESCRIPTION OF THE EMBODIMENTS 
       [0024]    The detailed description set forth below in connection with the appended drawings is intended as a description of various embodiments of the present invention and is not intended to represent the only embodiments contemplated by the inventor. The detailed description includes specific details for the purpose of providing a comprehensive understanding of the present invention. However, it will be apparent to those skilled in the art that the present invention may be practiced without these specific details. 
         [0025]    Field experience shows intermittent failure as the leading factor contributing to reduced reliability, which suggests that generally accepted practices in the art have failed to address the root causes. Reduced reliability is particularly detrimental when it manifests itself as unacceptable downtime, lost production and increased operating costs. 
         [0026]    Transporting large compressors over land requires adherence to road transport standards, which further increases transportation costs due to limits on trailer/skid size and weight. Having considered feedback from field experience, it was found that the large mobile compressors currently in service suffer from excessive wear and tear during operation. 
         [0027]    Mobile natural gas compressors may be employed in order to improve cost-effectiveness in reusing natural gas compression assets. Without limiting the invention, mobile compressors are assembled on a trailer having wheels. The wear and tear is aggravated by: the inherent weight-reduction manufacture methods required for mobile compressors, the typical rough terrain over which the mobile compressors have to be transported to, and the unsettled terrain on which such compressors are installed for operation at, the geographically remote site. 
         [0028]    In accordance with an embodiment of the invention, trailer implementations addressing wear and tear during transport include the use of air-ride equipment, the trailer being configured such that a mobile natural gas compression package sits on dolly legs, and the rear springs and wheels during operation thus contributing to the reduction of cost overheads by reducing site preparation costs and downtime. In accordance with the embodiment of the invention, a rig mat may be employed under the trailer to further reduce site preparation costs. 
         [0029]    In accordance with an embodiment of the invention, the trailer may include a flexible frame, which improves longevity and reliability by absorbing and dissipating vibration during operation, and jarring during transport over gravel roads and uneven terrain.  FIGS. 1 and 2 , show a flexible trailer frame  100 , the arrows  102 ,  104 , and  106  showing, in an exaggerated fashion, the front end tongue portion of the trailer frame flexing, the back end of the trailer frame flexing, and the trailer frame twisting, respectively. 
         [0030]    In accordance with an implementation of the embodiment of the invention shown in  FIG. 1 , the flexible frame includes a pre-cambered frame  100 , which is particularly suited for withstanding bending during transport while allowing vibration absorption and dissipation during sustained operation. In general, the amount of pre-camber varies with the width and length of the trailer, and with the weight of the compression package components. 
         [0031]    In accordance with another implementation of the embodiment of the invention shown in  FIG. 3 , with the pre-cambered and/or flexible frame  100  allowing for deflection, a housing  110  may configured to expand and contract as the trailer frame  100  flexes while protecting the compression package components in its interior against the elements. For example, housing expansion may be provided by a sectional building ( 110 ) having sections  112 ,  114 ,  116  and expansion joints  118  between adjacent building sections  112 / 114 ,  114 / 116 . The invention is not limited to expansion joints of the type shown, and may include overlapping flaps  120 ,  122 . Alternatively, a bellows-like sleeve (not shown) may be used between building sections  112 / 114 ,  114 / 116  to provide the necessary protection against the elements. Furthermore, a secondary frame (not shown) may be used. 
         [0032]    As previously stated herein above, the relative movement allowed by a flexible trailer frame is particularly well suited for bending during transport and vibration absorption and dissipation. However, such relative movement would lead to catastrophic failure of some compression package components including, but not limited to, the engine and compressor. In accordance with the embodiment of the invention shown in  FIGS. 1 , and  4 , the trailer may include an inflexible sub-skid  130  for supporting at least the engine  132  and compressor  134 , the flexible frame  100  flexing about the inflexible sub-skid  130 . The sub-skid  130  ensures that sub-skid mounted components form a single cohesive unit and do not move relative to one another during transport and operation. The sub-skid  130  may include an arrangement of reinforcing stringers  136 , an example of which is shown in  FIG. 5 . Rigid connections between sub-skid mounted components reduce wear, reduce maintenance downtime, and therefore increase reliability of such a mobile compression package. 
         [0033]    In accordance with an implementation of the invention shown in  FIG. 6 , the sub-skid  130  may be rigidly attached to the flexible frame  100 . Additional stringers  138  may be used in the construction of the trailer frame  100  under the sub-skid  130  in order for the trailer frame  100  to have increased rigidity under the sub-skid  130 . Improved rigidity may be attained by employing a stringer ( 136 / 138 ) spacing between 0.5 ft and 2.5 ft, while good rigidity may be attained by employing a stringer ( 136 / 138 ) spacing between 1 ft and 2 ft. Various attachment means between the trailer frame  100  and sub-skid  130  may be employed such as, but not limited to, welding. Rigid attachment may be provided by welding stringers  136  of the sub-skid  130  to the stringers  138  to between 80% and 100% of the possible outside welding area, and by partially welding stringers  136  and  138  at least to 25% of the possible inside welding area. Field experience shows a substantial improvement in reliability may be gained when the inside welding has between 40% and 60% coverage. 
         [0034]    In accordance with the embodiment of the invention, increased allowance may be made for ancillary compression package components not affixed to the sub-skid  130  to tolerate as much relative movement as practical during transport. A multitude of break flanges  140  may be employed, as shown in  FIG. 7 , between compression package components affixed to the sub-skid  130  and ancillary compression package components affixed to the rest of the flexible frame  100 . Break flanges  140  may further be employed between ancillary compression package components affixed to the flexible frame  100  only. The break flanges  140  may be disconnected or loosened to allow the compression package to flex during transport. The break flanges  140  are tightened on site before operation. 
         [0035]    A unitary mobile natural gas compression package further includes cooler components. For example,  FIG. 8  shows a cooler  142  which may be employed to cool at least the engine  132 , and cooler  144  which may be employed to cool the natural gas. Both coolers  142  and  144  represent examples of compression package components affixed to the flexible frame  100 . 
         [0036]    For example, the natural gas cooler  144  is driven hydraulically and therefore connectivity to sub-skid  130  mounted components may include the use of break flanges  140  as mentioned above. The engine cooler  142  may be affixed to the trailer tongue, which is particularly flexible.  FIG. 1  shows the trailer tongue being relatively more flexible  102  than the back wheeled portion of the trailer ( 104 ). The engine cooler  142  may be belt driven  146  directly by the engine  132  while the engine coolant is circulated through piping which may include sections of braided hose  148 . Engine cooler drive belts ( 146 ) may be removed or loosened during transport. The uneven terrain on which the mobile natural gas compression package may be installed may induce misalignment between the engine cooler  142  and the engine  132 . 
         [0037]    In accordance with another implementation of the embodiment of the invention, misalignment between the engine cooler  142  on the flexible frame  100  and the engine  132  on the inflexible sub-skid  130  may be achieved by hinging  150  engine cooler  142  on the side closest to the engine  132 , and by employing an adjustable cooler support. The adjustable cooler support may include a jacking bolt arrangement provided to adjust the position of cooler  132  so as to align drive belt pulleys ( 146 ) and reduce stress on the braided hose  148 . The adjustable cooler support may further be employed to properly tension the drive belts  142  in order to ensure proper cooling. Poor tension may also lead to premature drive belt wear or slip. Proper engine cooling reduces downtime and therefore increases reliability of the overall unitary mobile natural gas compression package. 
         [0038]    In accordance with a further implementation of the embodiment of the invention, a gas scrubber component  160  may also be affixed to the inflexible sub-skid  130  as shown in  FIGS. 4 and 7 . Field experience shows improved reliability by mounting the scrubber  160  horizontally and as low as possible on the sub-skid  130 , as reduced vibration is experienced when the center of gravity is lowered. 
         [0039]    In accordance with the embodiment of the invention, the housing  110  of the mobile unitary high horsepower compression package may include a pullout arrangement  170  as shown in  FIGS. 8 and 9 . The pullout arrangement  170  addresses adherence to trailer size restrictions specified in the relevant transport standards, while providing adequate access to the compression package components during use and maintenance, without compromising protection against the elements at all times. The provision of adequate access to compression package components under varying environmental conditions improves reliability via improved maintenance access resulting in reduced production losses. 
         [0040]    In accordance with an implementation of the embodiment of the invention, the pullout arrangement  170  may include a pullout platform  172 , sectional floor panels  174 , and sectional sidewall panels  176 . During transport, the pullout platform  172  is stowed substantially flush with or within the trailer having a transport standards compliant size. During use, the pullout platform  172  improves ease of use of the mobile compression package, and improves maintenance access to parts and components the operational parameters of which have to be confirmed regularly. The verification of operational parameters further improves reliability through reduced downtime. 
         [0041]    The pullout platform  172  itself may have a frame  178 . The trailer frame  100  may include apertures  180  sized to receive the portions of the pullout frame  172  during transport, and optionally to provide anchoring for the pullout frame  172 . The pullout frame  172  may include modular components such as, but not limited to, insulated wall sections and/or floor sections, removable insulation members, translucent/transparent panels  186  allowing ambient light to enter the housing  110 , and pullout platform locking elements  188 , all of which may be removed and stored separately from the pull-out platform  172  during transport. 
         [0042]    In accordance with another implementation of the embodiment of the invention, a disk style muffler  190  may be employed for sound deadening ( FIGS. 4 and 7 ). Disk style mufflers run cooler when compared to other muffler styles of the same capacity. Also disk style mufflers emanate less radiant noise during operation. Because of reduced heat output, disk style mufflers can be insulated which further reduces the radiant noise output. For this reason, the insulated disk style muffler may be installed inside the housing  110  to further reduce radiant noise during operation and overall transportation height. 
         [0043]    In accordance with a further implementation of the embodiment of the invention, the housing  110  may include removable roof panels  196  (shown in  FIG. 3 ) providing access to compression package components for maintenance, and quick replacement, which improves turnaround times. The removable roof panels  196  may be used in combination with the disk style muffler  190  installed (above compressor  134 ) within the housing  110  as shown in  FIGS. 3 and 4 , wherein the disk style muffler  190  registers with at least one roof panel  196  and is removable through the roof of the housing  110  improving ease of access and maintenance. 
         [0044]    Although various aspects of the present invention have been described herein including for example a pre-cambered flexible frame, an inflexible sub-skid, break flanges, an expandable building, a pullout platform, a disk style muffler, an adjustable cooler support, and horizontal gas scrubber, it is to be understood that each of these features may be used independently or in various combinations, as desired, in a unitary mobile high horsepower rating natural gas compression package. 
         [0045]    The previous description of the disclosed embodiments is provided to enable any person skilled in the art to make or use the present invention. Various modifications to those embodiments will be readily apparent to those skilled in the art, and the generic principles defined herein may be applied to other embodiments without departing from the spirit or scope of the invention. Thus, the present invention is not intended to be limited to the embodiments shown herein, but is to be accorded the full scope consistent with the claims, wherein reference to an element in the singular, such as by use of the article “a” or “an” is not intended to mean -“one and only one” unless specifically so stated, but rather “one or more”. All structural and functional equivalents to the elements of the various embodiments described throughout the disclosure that are known or later come to be known to those of ordinary skill in the art are intended to be encompassed by the elements of the claims. Moreover, nothing disclosed herein is intended to be dedicated to the public regardless of whether such disclosure is explicitly recited in the claims. No claim element is to be construed under the provisions of 35 USC 112, sixth paragraph, unless the element is expressly recited using the phrase “means for” or “step for”. 
         [0046]    The embodiments presented herein are exemplary only, and persons skilled in the art would appreciate that variations to the embodiments may be made without departing from the spirit of the invention. The scope of the invention is solely defined by the appended claims.