Patent Publication Number: US-2019186227-A1

Title: Oilfield apparatus and methods of use

Description:
CROSS REFERENCE TO RELATED APPLICATION(S) 
     This application is a continuation of U.S. patent application Ser. No. 15/452,525, filed Mar. 7, 2017, which is a continuation of U.S. patent application Ser. No. 14/396,660, filed Oct. 23, 2014, which is a U.S. National Stage Entry of International Patent Application No. PCT/GB2013/051059, filed Apr. 26, 2013, which claims the benefit of U.S. Provisional Patent Application No. 61/639,020, filed Apr. 26, 2012, the disclosures of which are hereby incorporated entirely herein by reference. 
    
    
     BACKGROUND 
     Technical Field 
     The present invention relates to oilfield apparatus and methods of use, and in particular to a sampling apparatus (such as a sampling chamber, a sampling test circuit, sampling tools), and methods of use for fluid intervention and sampling in oil and gas production or injection systems. The invention has particular application to subsea oil and gas operations, and aspects of the invention relate specifically to methods and apparatus for combined fluid injection and sampling applications. 
     State of the Art 
     In the field of oil and gas exploration and production, it is common to install an assembly of valves, spools and fittings on a wellhead for the control of fluid flow into or out of the well. Such flow systems typically include a Christmas tree, which is a type of fluid manifold used in the oil and gas industry in surface well and subsea well configurations. A Christmas tree has a wide range of functions, including chemical injection, well intervention, pressure relief and well monitoring. Christmas trees are also used to control the injection of water or other fluids into a wellbore to control production from the reservoir. 
     There are a number of reasons why it is desirable to access a flow system in an oil and gas production system (generally referred to as an “intervention”). In the context of this specification, the term “fluid intervention” is used to encapsulate any method which accesses a flow line, manifold or tubing in an oil and gas production, injection or transportation system. This includes (but is not limited to) accessing a flow system for fluid sampling, fluid diversion, fluid recovery, fluid injection, fluid circulation, fluid measurement and/or fluid metering. This can be distinguished from full well intervention operations, which generally provide full (or near full) access to the wellbore. Full well intervention processes and applications are often technically complex, time-consuming and have a different cost profile to fluid intervention operations. It will be apparent from the following description that the present invention has application to full well intervention operations. However, it is an advantage of the invention that full well intervention may be avoided, and therefore preferred embodiments of the invention provide methods and apparatus for fluid intervention which do not require full well intervention processes. 
     International patent application numbers WO00/70185, WO2005/047646 and WO2005/083228 describe a number of configurations for accessing a hydrocarbon well via a choke body on a Christmas tree. Although a choke body provides a convenient access point in some applications, the methods of WO00/70185, WO2005/047646, and WO2005/083228 do have a number of disadvantages. Firstly, a Christmas tree is a complex and carefully-designed piece of equipment. The choke performs an important function in production or injection processes, and its location on the Christmas tree is selected to be optimal for its intended operation. Where the choke is removed from the choke body, as proposed in the prior art, the choke must be repositioned elsewhere in the flow system to maintain its functionality. This compromises the original design of the Christmas tree, as it requires the choke to be located in a sub-optimal position. 
     Secondly, a choke body on a Christmas tree is typically not designed to support dynamic and/or static loads imparted by intervention equipment and processes. Typical loads on a choke body in normal use would be of the order of 0.5 to 1 tonnes, and the Christmas tree is engineered with this in mind. In comparison, a typical flow metering system as contemplated in the prior art may have a weight of the order of 2 to 3 tonnes, and the dynamic loads may be more than three times that value. Mounting a metering system (or other fluid intervention equipment) on the choke body therefore exposes that part of the Christmas tree to loads in excess of those that it is designed to withstand, creating a risk of damage to the structure. This problem may be exacerbated in deepwater applications, where even greater loads may be experienced due to thicker and/or stiffer components used in the subsea infrastructure. 
     In addition to the load restrictions identified above, positioning the flow intervention equipment on the choke body may limit the access available to large items of process equipment and/or access of divers or remotely operated vehicles (ROVs) to the process equipment or other parts of the tree. 
     Furthermore, modifying the Christmas tree so that the chokes are in non-standard positions is generally undesirable. It is preferable for divers and/or ROV operators to be completely familiar with the configuration of components on the Christmas tree, and deviations in the location of critical components are preferably avoided. 
     Another drawback of the prior art proposals is that not all Christmas trees have chokes integrated with the system; approaches which rely on Christmas tree choke body access to the flow system are not applicable to these types of tree. 
     It is amongst the objects of the invention to provide a method and apparatus for accessing a flow system in an oil and gas production system, which addresses one or more drawbacks or disadvantages of the prior art. In particular, it is amongst the objects of the invention to provide a method and apparatus for fluid intervention in an oil and gas production system, which addresses one or more drawbacks of the prior art. An object of the invention is to provide a flexible method and apparatus suitable for use with and/or retrofitting to industry standard or proprietary oil and gas production manifolds, including Christmas trees. 
     It is an aim of at least one aspect or embodiment of the invention to provide an apparatus which may be configured for use in both a subsea fluid injection operation and a production fluid sampling operation and a method of use. 
     An aim of at least one aspect of the invention is to provide an improved sampling apparatus for oil and gas operations and methods of use. Other aims and objects of the invention include providing an improved sampling chamber, a sampling test circuit, sampling tools, and/or methods for fluid intervention which are improved with respect to sampling apparatus and method of the prior art. A further aim of at least one aspect of the invention is to provide a sampling apparatus and method of use which facilitates the use of novel flow system access methods and fluid intervention operations. 
     Further objects and aims of the invention will become apparent from the following description. 
     SUMMARY 
     According to a first aspect of the invention there is provided a sampling apparatus for a hydrocarbon production system, the sampling apparatus comprising:
         a sampling chamber;   a fluid inlet and a fluid outlet to the sampling chamber, the fluid inlet and fluid outlet configured to be in communication with a production fluid flowing in a production flow bore; and   a sampling port in fluid communication with the sampling chamber;   wherein the sampling apparatus comprises a formation configured to be exposed to a production fluid flowing in the production bore and create a pressure differential between the fluid inlet and fluid outlet which drives production fluid from the production bore into the sampling chamber via the fluid inlet.       

     Preferably the formation is configured to create a Venturi effect which reduces the pressure in the production bore in an area closer to the fluid outlet than the fluid inlet. The formation may reduce the pressure in the production bore adjacent or substantially adjacent the fluid outlet. 
     The formation may comprise a flow restriction in the production bore. The flow restriction may be arranged such that the narrowest point of the production bore (at least in a locality of the sampling apparatus) is adjacent or substantially adjacent to the fluid outlet. 
     Preferably the apparatus is configured to circulate fluid through the sampling chamber via the fluid inlet and fluid outlet. 
     An opening to the fluid inlet may at least partially be oriented to face a prevailing flow direction of production fluid in the production bore. This may assist in directing flow into the fluid inlet. An opening to the fluid outlet may at least partially be oriented perpendicular to a prevailing flow direction of production fluid in the production bore. This may assist in exposing the fluid outlet to an area of reduced local pressure, and enhance circulation of fluid through the sampling apparatus. 
     The sampling chamber may be disposed radially of the production bore, and may be located in a side bore formed to the production bore. 
     At least a part of the sampling chamber may be located above the production bore, and in one embodiment, the sampling chamber is located entirely above the production bore. In this configuration, the production fluid is drawn into the sampling chamber against the effect of gravity. 
     At least a part of the sampling chamber may be located below the production bore, and in one embodiment, the sampling chamber is located entirely below the production bore. In this configuration, the production fluid is drawn into the sampling chamber with assistance from the effect of gravity. 
     The sampling chamber may comprise one or more baffles. The sampling port may comprise a stem which extends into the sampling chamber. An opening to the stem may be located in a lower portion of the sampling chamber. Thus the opening to the stem may be configured to preferentially withdraw liquid phase fluids from the sampling chamber. 
     The formation may be disposed asymmetrically in the production flow bore (i.e. on one side of the production bore). 
     The hydrocarbon production system may be a subsea hydrocarbon production, and the production flow bore may be a subsea flow line from a subsea well operating in production mode. 
     The sampling apparatus may be configured to collect a sample of a production fluid flowing in a production flow bore via the fluid inlet when in a sampling mode; and may be configured to provide an injection flow path for an injection fluid from an injection fluid conduit to the production flow bore when operating in an injection mode. 
     According to a second aspect of the invention there is provided a hydrocarbon production system comprising:
         a production flow bore;   a sampling apparatus associated with the production flow bore, the sampling apparatus having a sampling chamber, a fluid inlet and a fluid outlet to the sampling chamber in communication with a production fluid flowing in a production flow bore; and a sampling port in fluid communication with the sampling chamber;   wherein the production flow bore comprises a formation which when exposed to a production fluid flowing in the production bore which creates a pressure differential between the fluid inlet and fluid outlet which drives production fluid from the production bore into the sampling chamber via the fluid inlet.       

     The sampling apparatus may have a first mode of operation in which a sample of a production fluid flowing in a production flow bore is collected via the fluid inlet; and may have a second mode of operation in which the sampling apparatus provides an injection flow path for an injection fluid from an injection fluid conduit to the production flow bore. 
     Embodiments of the second aspect of the invention may include one or more features of the first aspect of the invention or its embodiments, or vice versa. 
     According to a third aspect of the invention there is provided a method of collecting a sample of fluid from a hydrocarbon production system, the method comprising:
         providing a sampling apparatus associated with a production flow bore, the sampling apparatus having a sampling chamber, a fluid inlet and a fluid outlet to the sampling chamber in communication with a production fluid flowing in a production flow bore; and a sampling port in fluid communication with the sampling chamber;   exposing the flow of production fluid to a formation to create a pressure differential between the fluid inlet and fluid outlet which drives production fluid from the production bore into the sampling chamber via the fluid inlet.       

     The method may comprise, in an injection mode of operation, passing an injection fluid from an injection fluid conduit through a flow path in the sampling apparatus to the production flow bore. The method may comprise, in a sampling mode of operation, collecting a sample of a production fluid flowing in a production flow bore via the fluid inlet. 
     Embodiments of the third aspect of the invention may include one or more features of the first or second aspects of the invention or their embodiments, or vice versa. 
     According to a fourth aspect of the invention there is provided a sampling apparatus for a hydrocarbon production system, the sampling apparatus comprising:
         a sampling chamber;   a fluid inlet and a fluid outlet to the sampling chamber, the fluid inlet and fluid outlet configured to be in communication with a production fluid flowing in a production flow bore;   wherein the sampling apparatus is configured to collecting a sample of a production fluid flowing in a production flow bore via the fluid inlet when in a sampling mode; and is configured to provides an injection flow path for an injection fluid from an injection fluid conduit to the production flow bore when operating in an injection mode.       

     The flow path may pass through the sampling chamber or a part thereof. The sampling apparatus may be configured to be disposed in an injection bore of the hydrocarbon production system. Preferably the flow path is an alternate flow path to those of the sampling conduits, including the paths created fluid inlet, fluid outlet and/or the sampling port (i.e. it is not necessary for the injection fluid to pass through the fluid inlet, fluid outlet or sampling ports. 
     The sampling apparatus may comprise a formation configured to be exposed to a production fluid flowing in the production bore and create a pressure differential between the fluid inlet and fluid outlet which drives production fluid from the production bore into the sampling chamber via the fluid inlet. 
     Embodiments of the fourth aspect of the invention may include one or more features of the first to third aspects of the invention or their embodiments, or vice versa. 
     According to a fifth aspect of the invention there is provided a hydrocarbon production system comprising:
         a production flow bore;   a sampling apparatus associated with the production flow bore, the sampling apparatus having a sampling chamber for collecting a sample of a production fluid flowing in a production flow bore;   wherein the sampling apparatus has a first mode of operation in which a sample of a production fluid flowing in a production flow bore is collected via the fluid inlet;   and wherein the sampling apparatus has a second mode of operation in which the sampling apparatus provides an injection flow path for an injection fluid from an injection fluid conduit to the production flow bore.       

     The production flow bore may comprise a formation which when exposed to a production fluid flowing in the production bore which creates a pressure differential between the fluid inlet and fluid outlet which drives production fluid from the production bore into the sampling chamber via the fluid inlet. 
     The sampling apparatus may comprise ports which define an injection flow path through the sampling apparatus in an injection mode. 
     The sampling apparatus may be configured to have a first condition in sampling mode. The injection flow path may be closed in the first condition. The sampling apparatus may be configured to have a second condition in an injection mode, in which the injection flow path is open. 
     The sampling apparatus may be configured to be moved from a first condition to a second condition by injection fluid pressure. 
     The hydrocarbon production system may comprise an isolation valve operatively associated with the sampling apparatus. In the first condition, the isolation valve may be closed and may isolate the sampling chamber from injection fluid. 
     Embodiments of the fifth aspect of the invention may include one or more features of the first to fourth aspects of the invention or their embodiments, or vice versa. 
     According to a sixth aspect of the invention there is provided a method of collecting a sample of fluid from a hydrocarbon production system, the method comprising:
         providing a sampling apparatus associated with a production flow bore, the sampling apparatus having a sampling chamber, a fluid inlet and a fluid outlet to the sampling chamber in communication with a production fluid flowing in a production flow bore;   in an injection mode of operation, passing an injection fluid from an injection fluid conduit through a flow path in the sampling apparatus to the production flow bore.       

     The method may comprise, in a sampling mode of operation, collecting a sample of a production fluid flowing in a production flow bore via the fluid inlet. 
     The method may comprise exposing the flow of production fluid to a formation to create a pressure differential between the fluid inlet and fluid outlet which drives production fluid from the production bore into the sampling chamber via the fluid inlet. 
     Embodiments of the sixth aspect of the invention may include one or more features of the first to fifth aspects of the invention or their embodiments, or vice versa. 
     According to a seventh aspect of the invention there is provided a method of injecting an injection fluid into a hydrocarbon production system using the apparatus or systems of any previous aspect of the invention. 
     Embodiments of the seventh aspect of the invention may include one or more features of the first to sixth aspects of the invention or their embodiments, or vice versa. 
     According to an eighth aspect of the invention there is provided a connection apparatus for a subsea hydraulic circuit, the connection apparatus comprising:
         a longitudinal body configured to be removably docked with a subsea hydraulic circuit receptacle, the longitudinal body comprising a plurality of radial ports axially displaced along the body;   wherein the body comprises an axial bore accommodating a spool having at least one fluid barrier;   and wherein the spool and fluid barrier are actuable to be axially moved in the bore to control axial flow paths along the bore between the plurality of radial ports.       

     The connection apparatus is preferably a hot stab hydraulic connection interface, configured to be received in a standard hot stab receptacle. 
     The fluid barrier may be an annular fluid barrier to seal an annulus between the spool and the bore. The apparatus may comprise at least three radial ports, and the spool and fluid barrier may be actuable to be axially moved from a first position in which a flow path between a first port and a second port is open, and a second position in which a flow path between the second port and a third port is open. In the first position a flow path from the third port to the first or second ports is preferably closed. In the second position, a flow path from the first port to the second or third ports is preferably closed. 
     Embodiments of the eighth aspect of the invention may include one or more features of the first to seventh aspects of the invention or their embodiments, or vice versa. 
     According to a ninth aspect of the invention there is provided a hot stab apparatus for a remotely operated vehicle, the hot stab apparatus comprising:
         a longitudinal body configured to be removably docked with a hot stab receptacle, the longitudinal body comprising a plurality of radial ports axially displaced along the body;   wherein the body comprises an axial bore accommodating a spool having at least one fluid barrier;   and wherein the spool and fluid barrier are actuable to be axially moved in the bore to control axial flow paths along the bore between the plurality of radial ports.       

     Embodiments of the ninth aspect of the invention may include one or more features of the first to eighth aspects of the invention or their embodiments, or vice versa. 
     The invention encapsulates methods of use of the apparatus of the eighth and ninth aspects in a hydrocarbon fluid sampling operation. 
     According to a tenth aspect of the invention there is provided a method of collecting a sample of fluid from a hydrocarbon production system, comprising using the apparatus of the eighth aspect of the invention to deliver a sample of fluid from the hydrocarbon production system to a sample collection vessel. 
     Embodiments of the tenth aspect of the invention may include one or more features of the first to ninth aspects of the invention or their embodiments, or vice versa. 
     According to an eleventh aspect of the invention there is provided a method of collecting a sample of fluid from a hydrocarbon production system, the method comprising:
         providing a sample collection vessel and a sampling hot stab apparatus in fluid communication with the sample collection vessel;   locating the sampling hot stab apparatus in a receptacle of the hydrocarbon production system, the receptacle being in fluid communication with a production fluid in the hydrocarbon production system;   collecting production fluid in the sample collection vessel via the sampling hot stab apparatus;   flushing the sampling hot stab apparatus prior to removal of the sampling hot stab apparatus from the receptacle.       

     The method may comprise providing a test hot stab apparatus, and coupling the test hot stab apparatus to the sample collection chamber and/or hydrocarbon production system. 
     The method may comprise decanting a pre-charged fluid from the sample collection vessel into the hydrocarbon production system, and may comprise controlling the decanting of the pre-charged fluid from the sample collection vessel using the test hot stab apparatus. Decanting the pre-charged fluid from the sample collection vessel may comprise flushing the sampling hot stab apparatus. 
     The method may comprise controlling the collection of production fluid into the sample collection vessel using the test hot stab apparatus. 
     The method may comprise flushing the sampling hot stab apparatus using a hydraulic fluid source coupled to the test hot stab apparatus, and/or may comprise controlling the flow of fluid through the sampling hot stab apparatus using the test hot stab apparatus. 
     The sampling hot stab apparatus may be a hot stab apparatus according to an embodiment of the tenth aspect of the invention, and the method may comprise actuating movement of the spool and fluid barrier of the hot stab apparatus using the test hot stab apparatus. 
     Embodiments of the eleventh aspect of the invention may include one or more features of the first to tenth aspects of the invention or their embodiments, or vice versa. 
     According to a twelfth aspect of the invention there is provided a system for collecting a sample of fluid from a hydrocarbon production system, the system comprising:
         a subsea hydraulic circuit comprising a sample collection vessel, a connection apparatus, and a receptacle for a hydraulic interface apparatus;   wherein the connection apparatus is configured to be coupled to the production system to connect the hydraulic circuit to the production system;   wherein the hydraulic circuit is configured to enable a production fluid to be delivered to the sample collection vessel via the connection apparatus;   and wherein the hydraulic circuit is configured to enable flushing of at least the connection apparatus.       

     The hydraulic circuit may be configured to enable flushing of the connection apparatus by actuation of the hydraulic interface apparatus, and/or may be configured to enable flushing of the connection apparatus from a hydraulic fluid source coupled to the hydraulic interface apparatus. 
     The hydraulic circuit may be configured to enable flushing of the connection apparatus with a pre-charged fluid decanted from the sample collection chamber. 
     The connection apparatus may be a connection apparatus according to the tenth aspect of the invention. 
     The hydraulic interface apparatus is an ROV test hot stab. In one embodiment, the system comprises a combined fluid injection and sampling apparatus. 
     Embodiments of the twelfth aspect of the invention may include one or more features of the first to eleventh aspects of the invention or their embodiments, or vice versa. 
     According to a thirteenth aspect of the invention there is provided a remotely operated vehicle comprising the connection apparatus of the ninth aspect of the invention. 
     Embodiments of the thirteenth aspect of the invention may include one or more features of the first to twelfth aspects of the invention or their embodiments, or vice versa. 
     According to a fourteenth aspect of the invention there is provided a subsea production fluid sample collection system comprising the connection apparatus of the tenth aspect of the invention. 
     Embodiments of the fourteenth aspect of the invention may include one or more features of the first to thirteenth aspects of the invention or their embodiments, or vice versa. 
     According to a fifteenth aspect of the invention there is provided a combined fluid injection and sampling apparatus for a subsea oil and gas production flow system, the apparatus comprising:
         a body defining a conduit therethrough;   a first connector for connecting the body to the flow system;   a second connector for connecting the body to a fluid injection apparatus;   wherein, in use, the conduit provides an injection path from the intervention apparatus to the flow system;   and wherein the apparatus further comprises a sampling subsystem for collecting a fluid sample from the flow system.       

     Preferably the sampling chamber is in fluid communication with the flow system via the first connector. 
     The apparatus preferably comprises a third connector for connecting the apparatus to a downstream flowline such as a jumper flowline. Therefore the apparatus may be disposed between a flowline connector and a jumper flowline, and may provide a flow path from the flow system to the jumper flowline, and may also establish an access point to the flow system, via the conduit and the first connector. 
     The second connector may comprise a hose connector. The apparatus may comprise a hose connection valve, which may function to shut off and/or regulate flow from a connected hose through the apparatus. The hose connection valve may comprise a choke, which may be adjusted by an ROV (for example to regulate and/or shut off injection flow). 
     Preferably the apparatus comprises an isolation valve between the first connector and the second connector. The isolation valve preferably has a failsafe close condition, and may comprise a ball valve or a gate valve. The apparatus may comprise a plurality of isolation valves. 
     The sampling subsystem may comprise an end effector, which may be configured to divert flow to a sampling chamber of the sampling subsystem of the apparatus, for example by creating a hydrodynamic pressure. 
     An inlet to the sampling chamber may be fluidly connected to the first connector. An outlet to the sampling chamber may provide a fluid path for circulation of fluid through the chamber and/or exit to a flowline. 
     Preferably, the sampling subsystem comprises a sampling port, and may further comprise one or more sampling needle valves. The sampling subsystem may be configured for use with a sampling hot stab. 
     The sampling subsystem may be in fluid communication with the flow system via a flow path extending between the first and third connectors. Alternatively or in addition the sampling subsystem may be in fluid communication with the flow system via a flow path extending between the first and third connectors. 
     Alternatively or in addition the sampling subsystem may be in fluid communication with the flow system via at least a portion of an injection bore. 
     Embodiments of the fifteenth aspect of the invention may include one or more features of the first to fourteenth aspects of the invention or their embodiments, or vice versa. In particular, apparatus or systems of the first to ninth aspects of the invention may be configured with a sampling subsystem as described (to be used with in a sampling operation) and/or an injection flow path (for use in an injection operation), and the apparatus or systems of the first to ninth aspects of the invention may be configured for just one of sampling or injection. 
     According to a sixteenth aspect of the invention there is provided a subsea oil and gas production system comprising:
         a subsea well; a subsea Christmas tree in communication with the well; and a combined fluid injection and sampling unit;   wherein the a combined fluid injection and sampling unit comprises a first connector connected to the flow system and a second connector for connecting the body to an intervention apparatus;   wherein, in use, the conduit provides an injection path from an injection apparatus to the flow system;   and wherein the apparatus further comprises a sampling subsystem for collecting a fluid sample from the flow system.       

     The system may further comprise an injection hose, which may be connected to the combined fluid injection and sampling unit. The hose may comprise an upper hose section and a subsea hose section. The upper and subsea hose sections may be joined by a weak link connector. The weak link connector may comprise a first condition, in which the connection between the upper hose and the subsea hose is locked, and a second (operable) condition, in which the upper hose is releasable from the subsea hose. 
     Embodiments of the sixteenth aspect of the invention may include one or more features of the first to fifteenth aspects of the invention or their embodiments, or vice versa. 
     According to a seventeenth aspect of the invention there is provided a method of performing a subsea intervention operation, the method comprising:
         providing a subsea well and a subsea flow system in communication with the well;   providing a combined fluid injection and sampling apparatus on the subsea flow system, the combined fluid injection and sampling apparatus comprising a first connector for connecting the apparatus to the flow system and a second connector for connecting the apparatus to a fluid injection apparatus;   connecting an injection hose to the second connector;   accessing the subsea flow system via an injection bore between the first and second connectors.       

     Preferably the access hub is pre-installed on the subsea flow system and left in situ at a subsea location for later performance of a subsea intervention operation. The injection hose may then be connected to the pre-installed unit and the method performed. 
     Preferably the method is a method of performing a fluid intervention operation. The method may comprise fluid sampling, fluid diversion, fluid recovery, fluid injection, fluid circulation, fluid measurement and/or fluid metering. 
     The method may be a method of performing a well scale squeeze operation. 
     The method may comprise performing a well fluid sampling operation. A preferred embodiment of the invention comprises: (a) performing a fluid injection operation; and (b) performing a well fluid sampling operation. Preferably the fluid injection operation and the well fluid sampling operation are both carried out by accessing the subsea flow system via the intervention path of the access hub. 
     Embodiments of the seventeenth aspect of the invention may include one or more features of the first to sixteenth aspects of the invention or their embodiments, or vice versa. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       There will now be described, by way of example only, various embodiments of the invention with reference to the drawings, of which: 
         FIGS. 1A and 1B  show schematically a subsea system in accordance with an embodiment of the invention, used in successive stages of a well squeeze operation; 
         FIGS. 2A and 2B  show schematically the subsea system of  FIGS. 1A and 1B  used in successive stages of a production fluid sample operation; 
         FIG. 3  is a sectional view of a combined injection and sampling hub used in the systems of  FIGS. 1 and 2 , when coupled to an injection hose connection; 
         FIG. 4  is a sectional view of a sampling chamber which may be used with the combined injection and sampling system of  FIG. 3  in an embodiment of the invention, shown in an injection mode; 
         FIG. 5  is a sectional view of the sampling chamber of  FIG. 4  in a sampling mode; 
         FIG. 6  is a sectional view of a sampling chamber according to an alternative embodiment of the invention; 
         FIG. 7  is a sectional view of a sampling chamber according to an alternative embodiment of the invention; 
         FIGS. 8A and 8B  are sectional views of a sampling tool according to an embodiment of the invention, in closed and open positions respectively; 
         FIG. 9  is a schematic view of a sampling test circuit according to an embodiment of the invention. 
     
    
    
     DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS 
     Referring firstly to  FIGS. 1 to 3 , a combined injection and sampling system will be described. The system, generally depicted at  600 , is shown schematically in different stages of a subsea injection operation in a well squeeze application in  FIGS. 1A and 1B  and in a sampling mode as described below with reference to  FIGS. 2A and 2B . A hub  650 , configured as a combined sampling and injection hub used in the methods of  FIGS. 1 and 2 , is shown in more detail in  FIG. 3 . 
     The system  600  comprises a subsea flow system  610  which includes subsea manifold  611 . The subsea manifold  611  is a conventional vertical dual bore Christmas tree (with internal tree components omitted for simplicity), and the system  600  utilises a hub  650  to provide access to the flow system  610 . A flowline connector  630  of a production branch outlet conduit (not shown) is connected to the hub  650  which provides a single access point to the system. At its opposing end, the hub  650  comprises a standard flowline connector  654  for coupling to a conventional jumper  656 . In  FIG. 1A , the hub  650  is shown installed with a pressure cap  668 . Optionally a debris and/or insulation cap (not shown) may also be provided on the pressure cap  668 . 
     The system  600  also comprises an upper injection hose  670 , deployed from a surface vessel (not shown). The upper injection hose  670  is coupled to a subsea injection hose  672  via a weak link umbilical coupling  680 , which functions to protect the subsea equipment, including the subsea injection hose  672  and the equipment to which it is coupled from movement of the vessel or retrieval of the hose. The subsea injection hose  672  is terminated by a hose connection termination  674  which is configured to be coupled to the hub  650 . The hub  650  is configured as a combined sampling and injection hub, and is shown in more detail in  FIG. 3  (in a condition connected to the hose connection  674  in the mode shown in  FIG. 1B ). 
     As shown most clearly in  FIG. 3 , the hose connection termination  674  incorporates a hose connection valve  675 , which functions to shut off and regulate injection flow. The hose connection valve  675  in this example is a manual choke valve, which is adjustable via an ROV to regulate injection flow from the hose  672 , through the hose connection  674  and into the hub  650 . The hose connection  674  is connected to the hub via an ROV style clamp  677  to a hose connection coupling  688 . 
     The hub  650  comprises an injection bore  682  which extends through the hub body  684  between an opening  686  from the main production bore  640  and the hose connection coupling  688 . Disposed between the opening  688  and the hose connection coupling  688  is an isolation valve  690  which functions to isolate the flow system from injection flow. In this example, a single isolation valve is provided, although alternative embodiments may include multiple isolation valves in series. The isolation valve  690  is a ball valve, although other valve types (including but not limited to gate valves) may be used in alternative embodiments of the invention. The valve  690  is designed to have a fail-safe closed condition (in embodiments with multiple valves at least one should have a fail-safe closed condition). 
     The hub  650  is also provided with a sampling chamber  700 . The sampling chamber comprises an inlet  702  fluidly connected to the injection bore  682 , and an outlet  704  which is in fluid communication with the main production bore  640  downstream of the opening  686 . The sampling chamber  700  is provided with an end effector  706 , which may be pushed down into the flow in the production bore  640  to create a hydrodynamic pressure which diverts flow into the injection bore  682  and into the sampling chamber  700  via the inlet  702 . Fluid circulates back into the main production bore via the outlet  704 . 
     In an alternative configuration the inlet  702  may be fluidly connected directly to the production bore  640 , and the end effector  706  may cause the flow to be diverted into the chamber  700  directly from the bore  640  via the inlet. 
     The sampling chamber  700  also comprises a sampling port  708 , which extends via a stem  710  into the volume defined by the sampling chamber. Access to the sampling port  708  is controlled by one or more sampling needle valves  712 . The system is configured for use with a sampling hot stab  714  and receptacle which is operated by an ROV to transfer fluid from the sampling chamber into a production fluid sample bottle (as will be described below with reference to  FIGS. 2A and 2B ). 
     The operation of the system  600  in an application to a well squeeze operation will now be described, with reference to  FIGS. 1A and 1B . The operation is conveniently performed using two independently operated ROV spreads, although it is also possible to perform the operation with a single ROV. In the preparatory steps a first ROV (not shown) inspects the hub  650  with the pressure cap  668  in place, in the condition as shown in  FIG. 1A . Any debris or insulation caps (not shown) are detached from the hub  650  and recovered to surface by the ROV. The ROV is then used to inspect the system for damage or leaks and to check that the sealing hot stabs are in position. The ROV is also used to check that the tree and/or jumper isolation valves are closed. Pressure tests are performed on the system via the sealing hot stab (optionally a full pressure test is performed), and the cavity is vented. The pressure cap  668  is then removed to the ROV tool basket, and can be recovered to surface for inspection and servicing if required. 
     The injection hose assembly  670 / 672  is prepared by setting the weak link coupling  680  to a locked position and by adjusting any trim floats used to control its buoyancy. The hose connection valve  675  is shut off and the hose is pressure tested before setting the hose pressure to the required deployment value. A second ROV  685  is deployed below the vessel (not shown) and the hose is deployed overboard to the ROV. The ROV then flies the hose connection  674  to the hub  650 , and the connection  674  is clamped onto the hub and pressure tested above the isolation valve  690  via an ROV hot stab. The weak link  680  is set to its unlocked position to allow it to release the hose  670  from the subsea hose  672  and the hub  650  in the event of movement of the vessel from its location or retrieval of the hose. 
     The tree isolation valve is opened, and the injection hose  672  is pressurised to the desired injection pressure. The hose connection valve  675  is opened to the desired setting, and the isolation valve is opened. Finally the production wing isolation valve is opened to allow injection flow from the hose  672  to the production bore to commence and the squeeze operation to be performed. On completion, the sequence is reversed to remove the hose connection  674  and replace the pressure cap  668  and any debris/insulation caps on the hub  650 . 
     It is a feature of this aspect and embodiment of the invention that the hub  650  is a combined injection and sampling hub; i.e. the hub can be used in an injection mode (for example a well squeeze operation as described above) and in a sampling mode as described below with reference to  FIGS. 2A and 2B . 
     The sampling operation may conveniently be performed using two independently operated ROV spreads, although it is also possible to perform this operation with a single ROV. In the preparatory steps, a first ROV (not shown) inspects the hub  650  with its pressure cap  668  in place (as shown in  FIG. 2A ). Any debris or insulation cap fitted to the hub  650  is detached and recovered to surface by a sampling Launch and Recovery System (LARS)  720 . The ROV is used to inspect the system for damage or leaks, and to check that the sealing hot stabs are in position. 
     The sampling LARS  720  subsequently used to deploy a sampling carousel  730  from the vessel (not shown) to depth and a second ROV  685  flies the sampling carousel  730  to the hub location. The pressure cap  668  is configured as a mount for the sampling carousel  730 . The sampling carousel is located on the pressure cap locator, and the ROV  685  indexes the carousel to access the first sampling bottle  732 . The hot stab (not shown) of the sampling bottle is connected to the fluid sampling port  708  to allow the sampling chamber  700  to be evacuated to the sampling bottle  732 . The procedure can be repeated for multiple bottles as desired or until the bottles are used. 
     On completion, the sample bottle carousel  730  is detached from the pressure cap  668  and the LARS  720  winch is used to recover the sample bottle carousel and the samples to surface. The debris/insulation cap is replaced on the pressure cap  668 , and the hub is left in the condition shown in  FIG. 2A . 
     The embodiment described with reference to  FIG. 3  has a particular configuration of combined injection and sampling unit, but other configurations are within the scope of the invention, including those with differing flow control valve and isolation valve configurations. Furthermore, while the sampling chamber  700  of the unit  650  is suitable for many applications, it is desirable to provide a more compact unit which is particularly easy to deploy and install on a subsea flow system.  FIGS. 4 and 5  are a sectional view of an improved sampling apparatus according to a preferred embodiment of the invention, in which a sampling chamber is configured for flow-through of injection fluids when an injection mode. 
     The sampling apparatus, generally shown at  100  in a combined injection and sampling unit  101 , comprises a cylindrical body  102  which is located in an enlarged bore portion  104  of the injection bore  106 . The cylindrical body  102  defines a volume which is a continuation of the injection bore, such that injection fluid flows downwards through the apparatus (and through the isolation valve  690 ) and into the enlarged bore portion. The cylindrical body supports a sleeve  108 , which is slidable (i.e. moves axially) within the cylindrical body and enlarged bore portions. A spring  110  located between the cylindrical body and the sleeve urges the sleeve towards an upward position (shown in  FIG. 5 ). An annular shoulder  112  at the top end of the sleeve and an annular shoulder  114  at a lower end of the cylindrical body provide respectively upper and lower bearing surfaces for the spring  110 . A secondary shoulder  116  is provided on an outer surface of the sleeve  108  part way along its length. 
     The lower end of the sleeve  108  is closed (other than a sampling inlet  118  and a sampling outlet  120  which will be described in more detail below) by a profiled end cap  122 . The sleeve is provided with radial ports  124 , circumferentially arranged around the sleeve and located towards a lower end of the sleeve. When the sleeve is in its upper condition, as shown in  FIG. 5 , the radial ports  124  are retracted into the cylindrical body  102 . An elastomeric seal ring  126  provides an annular seal between the sleeve and the cylinder when the sleeve is in an upper retracted position, as shown in  FIG. 5 . 
     The sampling apparatus  100  also comprises a sampling port  128 , which extends via a stem  130  into a sampling chamber  132 . Access to the sampling port  128  is controlled by one or more sampling needle valves  134 . The sampling apparatus is configured for use with a sampling hot stab and a receptacle which is operated by an ROV to transfer fluid from the sampling chamber into a production fluid sample bottle as will be described below. 
     The embodiment described with reference to  FIGS. 4 and 5  provides a highly compact construction, with the sampling chamber  132  located coaxially with an injection bore  106 . This reduces the overall size and weight of the apparatus, rendering it particularly suitable for subsea deployment operations. 
     This embodiment offers the additional advantage that it can be operated in an injection mode. During injection of fluids via the injection bore  106 , fluid passes into the enlarged bore portion  104  and into the interior of the sleeve  108 . Pressure increases on the interior of the sleeve until the force on the sleeve overcomes the biasing force due to the spring  110 . The spring is compressed and the sleeve moves downwards until the secondary shoulder  116  of the sleeve engages with the lower shoulder  114  on the cylindrical body, as shown in  FIG. 4 . In this position, the radial ports  124  are open to the main production bore  105 , and the injection fluid flows out of the injection bore and into the production bore to the reservoir. The spring force is selected such that the sleeve is only opened in the presence of a sufficient injection pressure in the injection bore. When injection stops, the spring force retracts the sleeve into the cylinder, to the position shown in  FIG. 5 . 
     In a sampling mode there is no injection flow, and the isolation valve  690  is closed. The sleeve is in its upper position in the cylindrical body, as shown in  FIG. 5 . The profiled end cap  122  of the sleeve  108  is partially inserted into the main production bore  105 , and is configured to create a Venturi effect which reduces pressure in the main product bore adjacent the sampling outlet  120 . A pressure differential between the sampling outlet  120  and sampling inlet  118  causes fluid in the main production bore to be driven into the sampling chamber via the sampling inlet. Fluid circulates back into the main production bore via the sampling outlet  120 . The Venturi effect can be moderated by changing the profile of the end cap  122  and/or the depth at which the end cap is set into the flow. It will be appreciated that flow of fluid into the chamber may also (or alternatively) be facilitated by externally creating a small pressure drop between the inlet and the outlet, for example by locating a flow restriction device such as a valve or Venturi profile in the main flow bore between the sampling inlet and sampling outlet positions. 
     The circulation of fluid through the chamber  132  ensures that the selected fluids are a representative sample of the recent flow composition (rather than a “stale” fluid sample). This is facilitated by designing the chamber with appropriate positioning of internal baffles and tube runs. In addition, the positioning of internal baffles and tube runs is such that liquids are preferentially retained in the sampling chamber (rather than gas phase fluids). For example, the internal opening of the sampling outlet tube is located in an upper part of the internal volume of the sampling chamber so that it tends to draw out any gas in the chamber via the sampling outlet. 
     When collection of a sample is required, an ROV operates the sampling needle valve  134  to allow pressure in the sampling chamber to drive the fluid from the sampling chamber, through the sampling port, to a collection vessel via a series of valves and flow lines. 
     Although the embodiment described with reference to  FIGS. 4 and 5  is configured for use in the combined injection and sampling application, its compact size and relative simplicity also renders it suitable for dedicated sampling of systems and processes (i.e. those which do not need to allow for the passage of injection fluids).  FIG. 6  is a sectional view of a dedicated sampling apparatus, generally shown at  200 , comprises a cylindrical body  202  which is located in a side bore  206  formed to a main production bore  205  in the subsea flow system, and is similar to the sampling apparatus  700  of  FIG. 3 . A lower end of the cylindrical body  202  is closed (other than a sampling inlet  218  and a sampling outlet  220  which will be described in more detail below) by a profiled end cap  222 , which is similar in form and function to the profiled end cap  122  of the sampling apparatus  122  of  FIGS. 4 and 5 . The cylindrical body  202  is in a fixed orientation in the side bore  206 . A sampling port  228  extends via a stem  230  into a sampling chamber  232  defined by the cylindrical body, and access to the sampling port is controlled by one or more sampling needle valves  234 . As before, the sampling apparatus  200  is configured for use with a sampling hot stab and a receptacle which is operated by an ROV to transfer fluid from the sampling chamber into a production fluid sample bottle. 
     Operation of the sampling apparatus  200  is as described with reference to the previous embodiment when in its sampling mode: the profiled end cap  222  of the apparatus  200  is partially inserted into the main production bore  205 , and creates a Venturi effect which reduces pressure in the main flow bore adjacent the sampling outlet  220 . Fluid circulates back into the sampling chamber via the inlet  218  and back into the main production bore via the sampling outlet  220 . The Venturi effect can be moderated by changing the profile of the end cap  222  and/or the depth at which the end cap is set into the flow, and may be facilitated by externally creating a small pressure drop between the inlet and the outlet. An internal baffle  236  and tubes are positioned to obtain representative samples and preferentially retain liquids in the sampling chamber (rather than gas phase fluids). 
     A sampling apparatus  250  according to an alternative embodiment of the invention is shown in sectional view in  FIG. 7 . The Figure is a longitudinal section through a sampling side bore  256 , perpendicular to an axial direction of a main production flow bore. The sampling apparatus  250  of this embodiment is gravity assisted and facilitates the collection of liquids into the chamber. The side bore  256  extends across and below the axis A of the main production bore. A sampling block  258  is accommodated in the side bore and defines a sampling chamber volume  282  located below the main production bore. The block  258  also defines flow conduits in the apparatus. The sampling block  258  comprises an aperture  260  which is aligned with substantially coaxially with the main production bore. However, the aperture  260  is profiled to create a reduced diameter section in the production bore. In this example, the reduced diameter section is substantially oval, with two side protrusions  262   a ,  262   b  which impinge into the flow path which corresponds to the main production bore. The sampling block  258  is also provided with a sampling inlet  268  and a sampling outlet  270 . The sampling inlet  268  comprises an opening  272  formed in one side protrusion of the block, substantially facing the direction of fluid flow in the main bore. This opening connects to a fluid conduit  274  which is formed in the axial direction of the side bore and the block, to direct flow to a lower end of the block where it is in communication with the sampling chamber  282 . The outlet  270  is provided in the sampling block between the aperture and the sampling chamber and provides a recirculation path for the production fluid. The apparatus also comprises a sampling port  278  which extends from the lower part of the sampling chamber to a sampling bottle via a system of valves and flow conduits  284 . 
     In use, fluid flow through the main bore impinges on the side protrusions  262   a ,  262   b  created by the aperture profile of the sampling block. A proportion of the fluid flow enters the opening to the sampling inlet  268 , and is redirected down the fluid conduit  274  of the inlet to enter the sampling chamber  282 . The fluid is circulated out of the outlet  270  and back into the aperture  256  to join the main production bore. Flow through the sampling chamber via the inlet and outlet is assisted by a Venturi effect created by the restricted flow portion which creates a pressure drop between the inlet and the outlet. In addition, flow into the inlet is assisted by gravity. This embodiment has particular benefits in collecting liquid phase fluids which tend to pass along the walls of the production bore, as opposed to gas phase fluids which preferentially travel along the centre of the bore. 
     It will be appreciated that in other configurations, the aperture may have a different shape (e.g. may be circular or asymmetrical) and may comprise multiple openings to one or more sampling inlets. 
     The sampling apparatus configurations of  FIGS. 4 to 7  are compact in size, low in weight, and have few (or no) moving parts. They provide flow through sampling chambers which facilitate the collection of representative samples of production fluids. The small size and weight lends the design to subsea deployment and installation, and moreover provide a wide range of installation options. In particular, the sampling apparatus of aspects and embodiments of the invention are suitable for installation in locations very close to the flowline, so that the chamber is maintained at the temperature of the flowing production fluid, and the sampling apparatus may be located close to a manifold such as a Christmas tree. The invention is particularly suitable for use and/or incorporation with hubs and/or hub assemblies which facilitate convenient intervention operations by facilitating access to the flow system in a wide range of locations. These include locations at or on the tree, including on a tree or mandrel cap, adjacent the choke body, or immediately adjacent the tree between a flowline connector or a jumper. Alternatively the apparatus of the invention may be used in locations disposed further away from the tree. These include (but are not limited to) downstream of a jumper flowline or a section of a jumper flowline; a subsea collection manifold system; a subsea Pipe Line End Manifold (PLEM); a subsea Pipe Line End Termination (PLET); and/or a subsea Flow Line End Termination (FLET). 
     Embodiments of the invention use remotely operated vehicle (ROV) hot stab systems for hydraulic control and fluid sampling. ROV hot stab tools are known in the art, but are generally limited to basic fluid line coupling applications. Conventional ROV hot stabs have at best limited sealing capabilities which often result in discharge of fluids to the surrounding environment. In hydraulic control applications, this may not be a significant problem; hydraulic fluids are of known composition and the discharge to a subsea environment may not be a significant environmental issue. Nevertheless, loss or discharge of some hydraulic fluids may generally be undesirable, particularly in low- or zero-discharge production regimes. More significantly, in sampling applications the discharge of production fluid samples leads to potential for environmental contamination. In sampling applications it is also desirable to have the ability to completely flush an ROV hot stab to avoid contamination between different production fluid samples. Preferred embodiments of the invention therefore use improved hot stab designs will be described with reference to  FIGS. 8A and 8B  (and which also form an alternative aspect of the invention). 
       FIG. 8A  is a sectional view of a hot stab and receptacle combination, generally shown at  300 . The hot stab receptacle  302  is a standard receptacle, as is found a range of subsea equipment including existing isolation valve testing and control blocks and sampling valve blocks. The hot stab  304  comprises a hot stab body  306  configured with appropriate shape and dimensions to be received in the standard hot stab receptacle  304 . 
     The hot stab  304  differs from a conventional hot stab in that it comprises an internal bore  308  which is axially aligned and extends through the hot stab body  306  from a control end  310  to a leading end  312  of the body. First, second and third radial ports  314   a ,  314   b ,  314   c  to the internal bore are located in axially separated positions along the hot stab body  306 , with associated needle valves  315 . The hot stab  304  is also provided with an internal valve, comprising a directional control spool  316  which can be moved between different positions in the hot stab body  306  to control various flow combinations. Flow barriers  318   a ,  318   b  are located in axially separated positions on the spool  316  to control the axial flow paths through the hot stab. 
     In the position shown in  FIG. 8A , the directional control spool is located in a closed position, with the spool disposed away from the leading end  312  of the hot stab (to the left as drawn). In this condition, fluid is free to flow from port  314   a  to port  314   b , via the internal bore and between the flow barriers  318  of the directional control spool. 
       FIG. 8B  shows the hot stab  304  in an open position, in which the directional control spool  316  has been moved further into the hot stab body (to the right as drawn) towards the leading end  312 . The movement of the directional control spool moves the flow barrier  318   a  in the control spool from one side of the port  314   b  to the opposing side of the opening  314   b . The flow barrier  318   a  in this position prevents flow between port  314   a  and port  314   b , but opens a flow path between port  314   b  and port  314   c.    
     In this embodiment, the hot stab is energised by a hydraulic signal from line  320 , although in alternative embodiments an electrical actuation signal can be provided. Also in this embodiment (and as shown in  FIG. 8A ) the hot stab is provided with a closing spring  322  which biases the position of the directional control spool  316  to the closed position (to the left as shown). 
     The addition of an axial bore  308  and directional control spool  316  to a hot stab converts the hot stab and receptacle combination into a directional control valve (with two positions in the example described above). A hot stab derived directional control valve as described has many practical applications, including but not limited to taking fluid samples from subsea oil and gas flow systems and infrastructure. Application to a fluid sampling system will now be described by way of example only with reference to  FIG. 9 . 
       FIG. 9  is a schematic view of a sampling circuit, generally shown at  400 , which utilises an ROV test hot stab  402  and an ROV sampling hot stab  304  to deliver a sampling fluid to a sample collection vessel  404 . The sample collection vessel  404  is pre-charged with an inert fluid such as nitrogen. The sampling hot stab  304  is a valved hot stab as described with reference to  FIGS. 8A and 8B , and is associated with the sample collection vessel  404 , initially docked into a test valve receptacle of the sample collection vessel. 
     In the preparatory steps, a sampling LARS (not shown) is used to deploy the sample collection vessel  404 , which forms a part of a sampling carousel, to depth. An ROV flies the sample collection vessel  404  to the location of the sampling apparatus (not shown), which may for example be the apparatus of any of  FIGS. 3 to 7 . The sampling carousel is located on a pressure cap locator, and the ROV indexes the carousel to access the first sample collection vessel  404 . 
     A sealing hot stab (not shown) is removed from receptacle  302  and parked in a spare receptacle on the carousel. The sampling hot stab  304  is removed from the test valve receptacle  406  of the sample collection vessel  404  and placed in the receptacle  302 , as shown in  FIG. 9 . In the position shown, the directional valve formed by the hot stab  304  and receptacle  302  is closed, and provides a flow path between ports  314   a  and  314   b . Port  314   b  is connected via a needle valve  315   b  to the sampling port of the sampling apparatus and port  314   a  is connected via a needle valve  315   a  to a pressure test flow line in an upper part of the sampling apparatus. 
     The ROV test hot stab  402  is located into the vacated sample collection vessel receptacle  406 , and the ROV test hot stab  406  is pressurised to energise the internal spool valve  316  of the sampling hot stab  304  and simultaneously force down the sample collection vessel decanting piston  408 . The sample hot stab  304  is opened to create a flow path from the port  314   c  (connected to the sample collection vessel) and the opening  314   b  (connected to the sampling port of the sampling chamber), and the fluid pre-charged in the sample collection vessel  404  is flushed through the sampling port, into the sampling chamber, and into the production bore, simultaneously cleaning all of the interconnection hoses and the sampling hot stab  304 . 
     The test hot stab pressure is held for a period to allow sample chamber to stabilise, and then is slowly reduced to a value just below the flowing well pressure. This action allows the contents of the sample chamber to be pumped, by well pressure, under control into the sample collection vessel  404 . The ROV monitors the sample collection vessel  404  until a piston indicator rod is seen rising through the sample collection vessel cap, and the test hot stab pressure is reduced to ambient pressure. 
     The sampling cavities, including the flow lines to the receptacle  302  and the sampling hot stab  304  itself can then be flushed by relocating the ROV test hot stab  402  in a test needle valve block (not shown) in communication with the sampling hot stab port  314   a . With the sampling hot stab  304  closed, and the needle valve  315   b  initially closed, needle valve  315   a  is opened to expose the port  314   a  to hydraulic pressure from ROV test hot stab  402 . The needle valve  315   b  is briefly opened and closed to flush fluid through the sampling cavities of the sampling hot stab  304 . After pressure testing the needle valves  315 , the sampling hot stab  304  is removed and located in the receptacle  406  of the sample collection vessel. The procedure can be repeated for multiple bottles as desired or until the bottles are used. 
     A significant advantage of the use of an internal valve hot stab as described is that in a sampling application, fluid conduit lines can be easily flushed, and potential environmental contamination associated with the leaking of production fluid samples to the subsea environment can be mitigated or eliminated. It will be appreciated that a range of other applications are facilitated by this aspect of the invention. By altering the control spool sealed positions, a number of different combinations of flow path may be incorporated into the design. 
     The invention in one of its aspects provides a connection apparatus for a subsea hydraulic circuit and method of use in a sampling application. The apparatus comprises a longitudinal body configured to be removably docked with a subsea hydraulic circuit receptacle. The body comprises a plurality of radial ports axially displaced along the body, and an axial bore accommodating a spool having at least one fluid barrie. The spool and fluid barrier are actuable to be axially moved in the bore to control axial flow paths along the bore between the plurality of radial ports. The apparatus may be configured as a sampling hot stab in an application to sampling a production fluid from a subsea hydrocarbon production system. 
     Aspects of the invention facilitate injection and sampling through a combined unit which provides an injection access point and a sampling access point. However, the invention in its various aspects also has application to a range of intervention operations, including fluid introduction for well scale squeeze operations, well kill, hydrate remediation, and/or hydrate/debris blockage removal; fluid removal for well fluid sampling and/or well fluid redirection; and/or the addition of instrumentation for monitoring pressure, temperature, flow rate, fluid composition, erosion and/or corrosion. 
     The apparatus and systems of embodiments described herein provide effective fluid sampling in a compact unit which is convenient, reliable, safe, and relatively low cost to deploy. The sampling apparatus of aspects and embodiments of the invention provide flexible operating options, including compatibility with control systems for injection and/or sampling operations. 
     Various modifications may be made within the scope of the invention as herein intended, and embodiments of the invention may include combinations of features other than those expressly described herein.