Abstract:
A temporary hydrocarbon well production system receives flow from a hydrocarbon well through a production line connected to the well. The production line flows into a sand separator, which has a fluid outlet connected to a choke manifold and a solids outlet connected to a sand dump line. A transportable and vertical closed separator receives flow through two separate lines from the choke manifold and from the sand dump line, which respectively flow into independent diffusing structures in the closed separator. Gas, vapors, volatile organic compounds, etc. are captured within the closed vessel and are discharged through a vapor discharge line attached to a vapor recovery unit for either further processing or incineration through a flare. A liquid dump line discharges liquids from the closed separator to at least one closed tank.

Description:
BACKGROUND OF THE INVENTION 
     This application relates to separators utilized for separating fluids produced from hydrocarbon wells, specifically to separators utilized for separating fluids produced from a hydrocarbon well during the flowback of drilling and stimulation fluids which are produced during the initial testing of a producing zone or following completion, re-completion, workover, or stimulation. Because this type of production frequently occurs with a drilling rig or work-over rig still on the well location, the well location is typically crowded with the rig and associated components, tanks, pumps, logging units, cementing units, pump trucks, drill string components, casing components, support vehicles, and other equipment utilized in the drilling or work-over operation. Because of the large array of equipment which is typically moved in and out of the location, there may be little space available at the well location. This problem is further exacerbated on offshore platforms, drilling islands, piers, and other remote well locations where available space for equipment can be extremely limited. 
     The availability of space at the well location can be further complicated when the well is stimulated by hydraulic fracturing and/or acidizing. Hydraulic fracturing typically requires large volumes of liquids and sands or other solids utilized as “proppant” to maintain the hydraulically induced fractures in an “open” configuration. Acidizing typically requires large volumes of stimulation fluids, displacement fluid, and the associated pumping equipment. The liquids and solids required for these and other work-over procedures are typically delivered to the well location in tanker trucks, bulk transport trucks, pods, railcars, workboat, and other modes of transport. These pieces of equipment are typically large and can consume a significant amount of the available footprint at the location. 
     The fluids produced from a well which has been placed on production following drilling, work-over, and/or stimulation, such as by hydraulic fracturing, may contain a number of components which are difficult to manage on a crowded well location, such as a high concentration of solids, high gas production rates, and returned stimulation fluids, such as spent acid or frac fluids. Producing these initial fluids, solids, and spent stimulation fluids into a temporary production and gauging system is generally favored over production into the permanent production system, which may not even be an option given the well location. 
     Moreover, temporary production systems dedicated to a single well facilitates the acquisition of data regarding the volume and make-up of the initial fluid and solid components produced from the well which may assist in evaluating the well and producing reservoir. 
     In the current typical practice, after the produced fluids and solids are directed through a solids separator and two phase gas-liquid separator, the produced fluids and solids are produced into open top tanks. These tanks allow the release of any entrained volatile organic compounds into the atmosphere. The escape of these VOCs into the atmosphere is undesirable because of the escape of the pollutants. However, no practical and satisfactory solution for temporarily producing the solids and fluids from newly completed and stimulated wells has been developed. A necessary component for a temporary production system which solves this problem would be a portable separator which: (a) occupies a relatively limited amount of space of the well location; (b) efficiently separates oil, gas, and solids; (c) captures fugitive VOCs; (d) is relatively easy to transport to and from the location; and (e) is relatively easy to clean following the receipt of significant volumes of solids. 
     SUMMARY OF THE DISCLOSURE 
     The presently disclosed temporary hydrocarbon well production system and associated fluid separator provides a solution to the problem identified above. The disclosed system facilitates the temporary production of hydrocarbons following the drilling, completion, work-over and/or stimulation of a hydrocarbon well (including stimulation wells, such as wells for the injection of water, steam, CO 2 , or wells utilized for other enhanced oil recovery methods). An embodiment of the temporary hydrocarbon well production system comprises a production line connected to a hydrocarbon well. The production line flows into a sand separator, which has a fluid outlet connected to a choke manifold and a solids outlet connected to a sand dump line. A closed separator receives flow through two separate lines from the choke manifold and from the sand dump line, which respectively flow into independent diffusing structures in the closed separator. These diffusing structures are capable of receiving high velocity solids-laden fluid. Any gas, vapors, volatile organic compounds, etc. which are entrained within either of the separate flow lines are captured within the closed vessel and discharged through a vapor discharge line attached to a vapor recovery unit for either further processing or incineration through a flare. A liquid dump line discharges liquids from the closed separator to at least one closed tank. 
     The separator, which is central to the disclosed system, is configured as a vertical closed vessel, which has an integral skid frame for facilitating transport by either truck, trail, or boat. The vertical configuration provides a reduced areal footprint. The closed top of the vessel allows the capture of any volatile organic compounds which are released as the fluid and solids are processed in the vessel. The separator contains internal structures for the receipt of high velocity solids-laden fluids. These fluids are received into two separate flow diffusers adjacent to the top of the vessel. 
     Embodiments of the separator are typically utilized on a temporary basis, such as for initial well clean up and testing. As a portable and temporary facility, embodiments of the disclosed apparatus may be utilized for initial flow testing of a newly drilled well or well which has been recompleted or stimulated with fracking or acid washing. The disclosed separator, apparatus, as a vertical vessel, is compact and presents a limited footprint. The separator is equipped with internal components which allow the introduction of high velocity solids laden fluids into the separator, as typical of a well placed on production following stimulation by hydraulic fracturing. The apparatus may also have exterior metering attached for immediate read-outs of produced volumes of oil, gas and water. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  schematically shows a flow diagram for an embodiment of the temporary hydrocarbon well production system of the present invention. 
         FIG. 2A  shows a first perspective view of an embodiment of the closed vertical separator of the present invention. 
         FIG. 2B  shows the view of  FIG. 2A , but with the vessel removed to show internal components, support structures, and attachments. 
         FIG. 3A  shows a second perspective view of an embodiment of the closed vertical separator of the present invention. 
         FIG. 3B  shows the view of  FIG. 3A , but with the vessel removed to show internal components, support structures, and attachments. 
         FIG. 4A  shows a first side view of an embodiment of the closed vertical separator of the present invention. 
         FIG. 4B  shows the view of  FIG. 4A , but with the vessel removed to show internal components, support structures, and attachments. 
         FIG. 5A  shows a second side view of an embodiment of the closed vertical separator of the present invention. 
         FIG. 5B  shows the view of  FIG. 5A , but with the vessel removed to show internal components, support structures, and attachments. 
         FIG. 6A  shows a top view of an embodiment of the closed vertical separator of the present invention. 
         FIG. 6B  shows the view of  FIG. 6A , but with the vessel removed to show internal components, support structures, and attachments. 
         FIG. 7A  shows a bottom view of an embodiment of the closed vertical separator of the present invention. 
         FIG. 7B  shows the view of  FIG. 7A , but with the vessel removed to show internal components, support structures, and attachments. 
         FIGS. 8A-8D  show a detailed view of an embodiment of a diffuser of the vessel of the present invention. 
         FIG. 9  shows a detailed view of an embodiment of a frame structure which may be utilized for supporting and transporting a vessel of the present invention. 
         FIG. 10  shows a view of an internal vessel cleaning manifold which may be utilized in embodiments of the present invention. 
     
    
    
     DETAILED DESCRIPTION OF THE EMBODIMENTS 
     The fluids produced by a newly drilled well, a re-drilled well, or a well which has been worked-over by perforating and/or stimulation may comprise fluids which are native to the hydrocarbon reservoir, such as oil, gas, condensates, water, and/or hydrocarbon-water emulsions. Entrained within the produced fluids may be solids such as formation sand and paraffin. However, particularly at start-up, in addition to native fluids and solids, the produced fluids may also comprise fluids and solids which were introduced into the well during the drilling and completion processes, with such fluids including drilling mud, completion fluids, spent acids solutions, and fracturing fluids, including solid propping materials introduced with those fluids such as sand, bauxite, etc. 
     Referring now to the figures,  FIG. 1  schematically shows a temporary hydrocarbon well production system. In this system, flow originates from hydrocarbon well  10  which may flow through a data header  12 , which is a short sub connected on the upstream side of a choke manifold to provide, optionally, an additional pressure gauge, thermowells, and sampling or injection ports. The data header  12  allows connection of pressure and temperature monitoring equipment, as well as sampling or injection equipment. Flow from wellhead  10  may continue through an emergency shutdown valve  14  through production line  16  to sand separator  18 . Sand separator (also known as a sand trap)  18  receives flow from production line  16 . Sand separator  18  has a fluid outlet  20  and a solids outlet which is attached to sand dump line  22 . The fluid outlet  20  is connected to a choke manifold  24  which is a system of valves and chokes for controlling the flow from the well  10 . Flow from choke manifold  24  is thereafter routed through choke outlet  26 . The flow through choke outlet  26 , by the appropriate valving, may be directed into test separator  28 , which will return liquids back into the fluid outlet  20  and separated gas into the gas discharge system. Both choke outlet  26  and sand dump line  22  are connected to closed separator  30 . Closed separator  30  is a largely self-contained unit which allows an operator to make the necessary connections and obtain a unit which receives a solids-laden fluid, separates the gas, liquids and solids and has a self-contained cleaning system. Closed separator  30  is packaged to be compact unit, having a relatively small footprint, and to be transportable by truck, rail, or boat. Closed separator  30  contains the vapors and volatile organic compounds contained within the received fluids and discharges these substances for further processing and incineration or sales. 
     Closed separator  30  receives flow from choked outlet  26  through a first inlet  32 . Closed separator  30  receives flow from sand dump line  22  through a second inlet  34 . Closed separator  30  comprises a first flow diffuser  36  connected to the first inlet  32  and a second flow diffuser  38  connected to the second inlet  34 . Both first flow diffuser  36  and second flow diffuser  38  are fully contained within closed separator  30 . Both diffusers  36 ,  38  reduce flow velocity, and generally direct flow downwardly in closed separator  30 . Liquid dump line  40  discharges liquids from closed separator  30  into at least one of closed tanks  42 . A vapor discharge line  44  discharges gas and vapor from the closed separator  30  into a gas gathering system which may include a vapor recovery unit  46 . Vapor recovery unit  46  may also gather free gas and vapor from closed tanks  42 . Gas and vapor collected into the gas gathering system may be processed through a flare scrubber  48  for collection of any liquids, and the free gas and vapors incinerated through flare  50  or further collected into a gas collection system for processing and sale or field use. 
     The system may also include a liquid circulation system which cleans separator  30 . Liquids from closed tanks  42  may be filtered through filter  52  and pressurized by pump  54  and circulated through closed separator  30  as described below from cleaning collected solids from the separator. 
     It is to be appreciated that the temporary hydrocarbon well production system shown schematically in  FIG. 1  and described above is a closed system in which vapors and volatile organic compounds are contained within the system and safely processed. 
     Closed separator  30  is a critical component of the temporary hydrocarbon well production system.  FIGS. 2A through 10  show various components of an embodiment of the closed separator  30 , which are describe hereafter. 
     As shown in  FIGS. 2A through 10 , closed separator  30  is configured as a vertical vessel. An appropriate pressure vessel  60  for the separator has approximately a ten foot outside diameter, and approximately a twenty foot seam-to-seam length with a cone bottom. Pressure vessel  60  is mounted within a transportable skid frame  62 , shown in detail in  FIG. 9 . Transportable skid frame  62  has central vessel supports  64  and lateral vessel supports  66 , which cradle pressure vessel  60 . Skid frame  62  is generally formed by base structural members  68  and longitudinal structural members  70 . These structural members may be fabricated from W8×21 beams. The transportable skid frame  62  has a lifting eye  72  and may be adapted for attachment to a dolly or the structural members may be equipped with lifting lugs and heavy duty casters to facilitate loading of the skid onto a flat bed truck, trailer or boat deck. Base structural members  68  are attached to cross members  74  which may be fabricated from four inch diameter scheduled  80  pipe. Longitudinal structural members  70  are attached to a common cross-member  74  with the base structural members  68  and a top cross-member  76  which may be fabricated from five inch diameter schedule  80  pipe. Longitudinal structural members  70  are also supported by brace members  78 , which may be steel square tubing such as a 3×3×¼ material. 
     Inflow to closed separator  30  is provided through first inlet  32 , which receives flow from choked outlet  26 , and second inlet  34 , which receives flow from sand dump line  22 . The first inlet  32  and the second inlet  34  flow independently to flow diffusers  36 ,  38 , which are enclosed within closed separator  30 , and typically located in the upper portion of vessel  60 . Flow diffusers  36 ,  38  may be disposed in a horizontal and parallel configuration within vessel  60 . As shown in the figures, the diffusers  36 ,  38  may span nearly the entire diameter of vessel  60 , and may range from 75 percent to 95 percent of the inside diameter of the vessel  60 .  FIGS. 8A through 8D  provide detail of diffuser  36 , with it understood that diffuser  38  may be identical to diffuser  36 . As shown in  FIG. 8A , diffusers  36  comprises a plurality of slot banks  80 , a slot bank defined as a group of slots  82  located at approximately the same axial position on a diffuser  38 . Slots  82  may have a long axis aligned along the long axis L 1  of the diffuser  36 . As indicated in  FIG. 8 c   , a single slot bank  80  may comprise 7 slots  80 , with the slots spaced at 45 degree intervals from each other. It is to be noticed that there are no slots directly facing the top of the vessel  60 . If should be further noticed that the diffusers  36 ,  38  may be used in connection with a flow shield  84 . Flow shield  84  diverts fluid flow downwardly away from the top of the vessel to reduce the potential for erosional damage which may otherwise occur from the high velocity flow of solids-laden fluid. Diffusers  36 ,  38  may terminate with solid round plug  86  and a relatively short length of pipe  88  which has a radiused end. The termination formed by round plug  86  and radiused pipe length  88  facilitates alignment of the diffusers during construction and provides support, with the termination abutting the inside wall of the vessel  60  opposite the side where flow enters the diffusers  36 ,  38 . 
     Solids exit vessel  60  through sand discharge  90 , which is located at the bottom of internal cone bottom  92  of the vessel  60 . Internal cone bottom may be fabricated from rolled ⅜ inch SA-38 plate, and form an angle of approximately 40 degrees from horizontal, and form an opening at the bottom of the cone, which may be 4 to 5 inches in diameter. The cone bottom  92  will typically have a height of about four feet. Sand discharge  90  may be connected at an opening of the cone bottom  92 . Washing sand and solids from the vessel  60  is facilitated by the use of cleaning manifold  94 , which is shown in greater detail in  FIG. 10 . Cleaning manifold  94  is disposed circumferentially around cone bottom  94 , toward the upper end of the cone bottom. Located about the cleaning manifold are a plurality of spray nozzles  96  which are positioned to spray in a generally tangential direction about the cone bottom  94 . Cleaning manifold  94  receives pressurized liquid flow from line  98 . Liquid for cleaning the vessel  60  is cleaned through filter  52  and pressurized by pump  54 , which are contained within the skid. 
     Gas, vapor, volatile organic compounds, etc., are discharged through vapor discharge line  44  which takes flow from the top of vessel  60 . Vapor discharge line  44  may be equipped with a gas meter  100 . As described above, vapor discharge line  44  is connected to vapor recovery unit  46 . 
     Liquids are discharged from vessel  60  through liquid dump line  40  into at least one of closed tanks  42 . Flow through dump line  40  is controlled by dump valve  102 . Liquid and solids samples from various levels in vessel  60  may be taken through sample cocks  104 . Manway  106  provides access to vessel internals when required for maintenance. 
     While the above is a description of various embodiments of the present invention, further modifications may be employed without departing from the spirit and scope of the present invention. Thus the scope of the invention should not be limited according to these factors, but according to the following appended claims.