Patent Application
20100059221
This invention relates to subsea apparatus for fluid sampling and/or analysis. In particular, the invention relates to a subsea apparatus for fluid sampling and/or analysis used in the oil and gas industry.
Understanding the properties of fluids in wells in the oil and gas industry is critical for the assessment of oil or gas reservoirs. For example, the fluid properties may be used for the proper management of oil and gas reservoirs including for instance production management and flow assurance. Fluid sampling and/or analysis may be performed during various phases of the exploration, development and production phases of a reservoir. Conventional tools are able to take a fluid sample from the well and bring it to surface where it is processed and analysed. For example, often times the phase behavior of the fluid may be studied using an analysis known in the industry as PVT analysis which measures, inter alia, the bubble point of the fluid as well as its wax, and asphaltene content. Also, compositional analysis of the fluid sample may be performed as well as analysis of its H2S, CO2, Hg, and heavy metal content. Also, well known are tools and methods for measuring the density and viscosity of the fluid its, water content, etc.
More and more of these measurements are arranged to be performed downhole. This is because, generally, obtaining a correct estimation of fluid phase behavior requires that a sample with a pressure and temperature as close as possible to the conditions present at the wellhead be taken so that wax and asphaltenes do not precipitate out of the fluid. Fluid properties at the surface may differ from those present at the wellhead. Sampling of the fluid at the surface is therefore not a suitable option for the correct estimation of the fluid phase behavior in subsea oil or gas wells. However, the conditions prevalent in a subsea environment make access to a subsea fluid sample rather difficult.
In a subsea oil or gas well installation, fluid flows from different well heads are often mixed through a series of manifolds. This poses an additional complication in the sampling and analysis of subsea wells. Sampling and analysis of the fluid flowing from each individual well would be preferred as it would provide a valuable understanding of the production capabilities and peculiarities of each well which in turn could be used for proper field management. Also, the properties of the fluid produced by subsea wells may change significantly over a short period of time. Thus, if the analysis of the samples that have been taken is done at a later time at a surface, the value of the data will be diminished.
Various apparatus, methods and systems for sampling and analyzing well fluids have been identified previously. U.S. Pat. No. 6,435,279 discloses a method and apparatus for sampling fluids from an undersea wellbore utilizing a self-propelled underwater vehicle, and a collection and storage device. The '279 patent describes a method for sampling a fluid produced from a subsea well, the method comprising a remotely operated vehicle (ROV) having a collecting device for collecting a sample of fluid and a storage facility for the collected sample of fluid wherein said collecting device and storage facility are connected to the ROV. The collecting device is used to collect a sample from a subsea location, storing the sample in the ROV and then transferring it to a surface location.
International patent applications WO 2008/087156, and WO 2006/096659 disclose various systems and methods for subsea sampling. The WO 2008/087156 patent application describes a subsea sampling and data collection device that is coupled to a flowline at a flowline installation. The WO 2008/087156 sampling and data collection device includes a sample collection system having a probe insertable into a flowline to collect a fluid sample. The WO 2008/087156 application is assigned to the same assignee as the present invention and it is hereby incorporated by reference for all purposes allowable under the law to the extent that its disclosure does not contradict with the present invention.
An article entitled “Improved production sampling using the Framo multiphase flow meter” by Framo Engineering AS in October 1999 discusses a multiphase flow meter used in fluid sampling, including subsea with the aid of remotely operated vehicles (ROV).
From the description above it is evident that for effective production and flow assurance management in subsea oil and gas reservoirs, there is a real need to obtain a good understanding of produced fluid on a well by well basis and to measure the variation of fluid properties from each of these wells with time. The present invention provides an improved apparatus and associated method that facilitate the sampling and the characterization of the fluids at a subsea environment, and as close as possible to each well head. The present invention and method also enable analysis of sampled fluid to occur on a real time basis and thus obtain accurate real time analysis data for well performance and management.
A first aspect of this invention provides subsea apparatus for sampling and analysing fluid from a subsea fluid flowline proximate a subsea well, comprising:
The fluid analysis data can be real time data, and this real time data is communicated to at least one electronic device which incorporates at least one software model used to provide information regarding the production of said subsea well. The software model may also used to provide predictions regarding the production of the well.
In one form of the invention the fluid analysis data is used to control at least one piece of subsea equipment. The fluid processing apparatus separates the sample of fluid into at least a liquid and a gaseous phase, or mixes the sample of fluid with at least one other different fluid, or enriches the sample of fluid.
In one form of the invention the fluid sampling device is in communication with the well fluid. The fluid sampling device may also be in communication with a fluid processing apparatus, the fluid processing apparatus being in communication with the well fluid.
Further according to the invention, at least one data processing device may be locatable in the housing and may be in communication with the fluid analysing device. The data processing device processes data received from the fluid analysis device and communicates the data.
The conveying means may be an attachment for a detachable subsea vehicle such as, for example, a remotely operated vehicle (ROV) or an autonomous underwater vehicle (AUV).
The subsea apparatus may further comprise a plurality of housings which are connectable to each other in a modular fashion. The fluid analysis device of each housing may be in fluid communication with the fluid analysis device of another connected housing. In the same way, the fluid sampling device of each housing may be in fluid communication with the fluid sampling device of another fluid sampling device of a connected housing, and the data processing device of each housing may be in fluid communication with the data processing device of a connected housing.
A second aspect of this invention provides a method of sampling and analysing fluid from a subsea well, the method comprising:
In one form of the invention the fluid sampling device is in fluid communication with a fluid processing apparatus, the fluid processing apparatus being in fluid communication with the well fluid flowing in the subsea flowline and the sample of fluid is obtained from the well fluid in the subsea flowline via the fluid processing apparatus. The fluid sampling device may also be in communication with a fluid processing apparatus that is in communication with the well fluid.
Further according to the invention, at least one data processing device may be locatable in the housing and may be in fluid communication with the fluid analysis device, and which further comprises processing fluid analysis data received from the fluid analysis device by means of the data processing device and communicating the processed data to another apparatus or to the surface. The method may further include processing fluid data received from the fluid analysis device and communicating the data.
The method may also comprise deploying one or more housings of the apparatus by means of a detachable subsea vehicle such as, for example, a remotely operated vehicle (ROV) or an autonomous underwater vehicle (AUV), the housings being connectable to each other.
In a further form of the invention there may be a plurality of housings, and the method may further comprise connecting the plurality of housings to each other in a modular fashion, and wherein each fluid analysis device of each housing is in fluid communication with each other, and each fluid sampling device of each housing is in fluid communication with each other.
Further aspects of the invention will be apparent from the following description.
a shows a diagrammatic view of a passive sampling device of the subsea apparatus for sampling and/or analysing fluid from a well according to another embodiment of the invention;
b shows a diagrammatic view of a passive sampling device of the subsea apparatus for sampling and/or analysing fluid from a well which uses venturi according to another embodiment of the invention;
a, 7b and 7c show a series of diagrammatic views of an adjustable inlet of a sampling device according to an embodiment of the invention;
This subsea apparatus for analysing and/or sampling fluid from a well according to the invention is applicable to subsea installations or facilities in the oil and gas industry. In the drawings
The subsea processing device 12 includes a fluid sampling device 14. The fluid sampling device 14 consists of a network of pipes connected to different sampling points in the processing device 12. The fluid sampling device 14 can also include a distributor that can redirect the sampled fluid to different outlet.
Subsea apparatus 10 further includes a remote operating device (ROV) docking station 16 which allows the docking and attachment of a remote operating device (ROV) 18 to the subsea processing device 12.
As shown in
A frame or skid 22 could also be docked to the docking station with the help of an ROV 18. As illustrated in
Skid 22 is designed so that other skids 22 of a similar type can be connected to it. The design is modular so that the skids 22 can be configured and assembled in different orders, and then used for different purposes.
Skid 22 can also be deployed using an autonomous under water vehicle AUV. In this case, the skid interface 24 may include instrumentation for the positioning of the AUV during docking.
An instrumentation module 26 is located inside skid 22 and is connected to a controller/communication module 28. Instrumentation module 26 contains the fluid analyzer and it is used to perform fluid analysis and/or fluid sampling. It is connected to the fluid interface 20 and it can receive the fluid collected by the fluid sampling device 14. The type of analysis and the sampling sequence is managed by the controller/communication module 28. The controller/communication module 28 performs control either through a pre-defined sequence stored in the controller, from the surface with the use of a communication link, or in a completely automated mode with the use of the fluid analysis data obtained by the fluid analyzer in instrumentation module 26. It is used to enable decisions to be made on how to process the sample of fluid.
There are various different possible schemes for the sampling which have been described previously in the art and these can easily be implemented in conjunction with this invention.
The fluid analyzer in instrumentation module 26 consists in a network of pipe connected to pumps, fluid properties sensors, sample chambers, fluid conditioners and injectors. This system is managed through the controller/communication module 28.
The fluid analysis data obtained by apparatus 10 is used to control various types of subsea or surface equipment. This fluid analysis data is based on real time sample measurements obtained from the fluid sample that is obtained and also possibly analyzed at wellhead conditions. This real time fluid data may be communicated to an electronic device which incorporates at least one software model and this model may be used to provide information regarding the production of the well and to provide predictions regarding the production of the well. Thus information regarding reservoir assurance, or flow assurance management may be obtained through the processing of this fluid data.
Details will now be provided of further embodiments of the invention.
The phase separator 30 which may be used is one of the typical examples of phase separators known in the art. Such a typical phase separator consists of a pressure vessel 32 with an internal pipe drilled with radial holes. The pressure vessel 32 includes a fluid inlet 34 and fluid outlet 36. The direction of fluid flow is shown by arrows A in
Phase generator 30 allows liquid can be sampled at the bottom of the vessel while gas can be sampled at the top.
The hydraulic sampling device of apparatus 10 is illustrated in
Passive sampling devices 26 do not require any pump to sample the fluid as these devices are based on passive mechanisms. Two different possible implementations of passive sampling devices are shown in
In
In practice several different types of fluid sampling devices can be used. For example, in
One possibility is to have two or more inlet pipes 40.1 and 40.2 with different heights as is illustrated in
Another possibility which is described in
c describes an adjustable fluid sampling or analyzing module 26 which uses a series of controllable valves 57 and 58 connected thereto to change the sampling point position. The valves 57 and 58 can be selectively closed. In the normal operation, all valves 58 are closed except for the valve 57 which is at the level of the sampling point. The fluid flow is illustrated in
In one embodiment of the invention there is a universal skid 22 used for fluid sampling and analysis. This skid 22 includes the fluid interface 20, power/communication module 28, skid or ROV interface 24, a local controller module and a fluid sampling or analysis module 26. The local controller module controls the working of the sampling or fluid analysis module 26.
One feature of apparatus 10 is its modularity. Apparatus 10 may be provided in different kinds of modules. Fluid, communication and skid or ROV interfaces are designed to be fully interoperable so that different kinds of modules of apparatus 10 can be interconnected and configured in many different types of configurations.
Another feature of apparatus 10 is that modules of apparatus 10 including skids 22 may be installed either on a temporary basis or on a semi-permanent basis.
Before any fluid sampling or fluid analysis operation starts, the skids 22 are fully engaged in an ROV 18 and connected to the various fluid interfaces. An individual module of apparatus 10 comprising a skid 22 and its attached equipment can be retrieved as required by an ROV 18.
The fluid sampling or analyzing device 26 which is mounted in a skid 22 in apparatus 10 is shown in more detail in
In device 26 injectors 66 can be used to inject fluids which are different from the fluid which is flowing in a particular flow line 60. The injected fluid can be used to generate an inhibitory chemical reaction with the sampled fluid or it can change the phase behavior of the fluid. Sample bottles or chambers 68 in device 26 are used to take and store samples of the fluid inside a flow line 60. Fluid property sensors 70 are also shown located on flow lines 60 in device 26.
In the drawings,
The fluorescence detector 76 can be used to, for example, detect traces of oil in water. This information can be useful for the assessment of subsea processing, for example, when water is separated from oil before being re-injected into the formation.
The fluid resistivity sensor 78 can be used to detect water resistivity, which can be very useful information which can in turn be used to detect injection water breakthrough. Injection water used for reservoir stimulation will usually have a resistivity different from that of formation water. Water resistivity changes, therefore, can be correlated with injection water breakthrough.
The fluid sampling or analysis device 26 can also include fluid conditioners. One possible fluid conditioner is a phase separator. This can be used for water or oil sampling. The main phase separator will give a liquid or gas separation. The phase separator within the fluid sampling or analysis device 26 can therefore be used to separate the oil from the water if necessary.
Another sensor which may form part of device 26 is a unit to “flash” the sample. Sample flashing consists of dropping the pressure of sample before injecting it with a specific sensor. This method is well known in the analysis of HP (high pressure) live oil samples by using gas chromatography.
The embodiment of device 26 which is illustrated in
In the drawings,
A piston unit that is used to increase the volume trapped between the seal valves and consequently to reduce sample pressure. There is a pressure sensor connected to the circulation loop to monitor pressure changes as the piston is retracted. The piston is preferably retracted when the circulation pump 96 is operating. The agitation created by the fluid moving helps to prevent a problem posed by fluid supersaturation. It is well-known in the art that estimation of bubble point requires some agitation as the pressure is changed. The circulation loop can include an ultrasonic transducer that will also generate agitation and this helps to prevent supersaturation.
A scattering detector 100 sensor is used in device 26 in order to detect bubbles or solid particles forming in a fluid flow line 60. The scattering detector 100 used is known in the art and is used to measure the attenuation of light as it passes through a cell. Formation of solid particles and gas bubbles will lead to an increase in the attenuation of light. This sensor is used to detect the fluid bubble point which indicates at which pressure gas starts to form in the flow line. Such sensors can be used to detect the gas condensate dew point, the fluid bubble point, gas bubble formation or the presence of solid particles.
A density and viscosity sensor 84 may also be included in device 26. It is used to measure the evolution of the parameters of density and viscosity against pressure.
An optical spectrometer (the lamp 72 and spectrometer 74 arrangement) may also be included in device 26 to measure fluid optical absorption at various wavelengths. The optical spectrometer, for example, can be used to estimate fluid composition by NIR spectroscopy. It is of particular interest for hydrocarbon analysis as the hydrocarbons have characteristic absorption peaks around [1600; 1800] nm. Spectral analysis in the visible range can also be used for monitoring asphaltene content of the fluid.
Device 26 may also include a camera 102 which is used to monitor the condition of the fluid in the flow lines for the presence of bubbles or solid particles. In addition, device 26 may also enclose a US transducer sensor 104.
Device 26 may be enclosed in a temperature control unit 106. The temperature control unit 106 may enable the temperature of the fluid to be changed. In this way by combining pressure and temperature changes, device 26 can provide a comprehensive phase diagram for the fluid trapped in the fluid flow lines 60 of the device.
Device 26 may be used in various downhole conditions and can be used in various applications such as, for example, the study of fluid phase diagrams (bubble point detection, wax or asphaltene onset, hydrate locus, etc), the study of fluid density and viscosity versus pressure, and the study of fluid composition.
Another important feature of the invention is the ability to sample fluid.
The sampling bottle 108 can be implemented as follows:
A cylindrical bottle 108 with a piston 110 defining two chamber spaces as it moves along the bottle's main axis. The sample chamber 112 is located on one side of piston 110 is and the water cushion chamber 114 is located on the other side of piston 110.
Bottle 108 is connected to the fluid sampling line as shown in
It will be noted that low shock sampling can also be done without the piston 110 being in the bottle as shown in
Low shock sampling is a well known technique for downhole fluid sampling. Other possible variations of fluid sampling have also been described in the prior art.
The fluid sampling can be controlled either from surface or it can be controlled through a predetermined sequence of actions to be taken on a periodic base.
The combination of the fact that the fluid sampling or analysis device 26 can be installed on a semi-permanent basis, the configuration of the sampling skid 22 and the possibility that sample can be obtained on a periodic basis, means that it is possible to sample the fluid without mobilizing an ROV 18 with its support vessel. Device 26 can therefore perform time-lapsed sampling during the time it is installed on a subsea apparatus 10. With the proposed configuration, the sampling can be performed though period of time from a few months to a few years. Sample bottles 108 can be retrieved at the surface by using an ROV 18 to pick up the skid 22 on which the sample bottles 108 are located.
A sampling bottle 108 may also include a temperature control unit 122. Temperature control allows the sample temperature to be kept the same as when it was in the fluid flow of the well. It would avoid phase transition due to temperature changes. In practice, the sample will tend to cool when it is sent to the bottle 108. The temperature control system can consist of a simple electrical heating system wrapped around the bottle.
Another important feature of the invention is the ability of sampling bottles 108 to be retrieved to the surface before the skid 22 is changed. The bottle 108 may include means for energy storage, a positioning system and a propulsion mechanism. An embodiment of the apparatus 10 according to the invention which illustrates such a configuration of a sample bottle 108 is shown in
The bottle 108 end fittings use male/female hot stabs 107 that can be released through a command sent from the skid controller. The bottle 108 is fixed to the skid chassis through a mechanical interface that can also be released by a command sent by the skid controller. The bottle 108 also includes a localization system that can communicate with the surface. When the bottle 108 needs to be released a command is sent from the surface and this triggers the inflation of the balloon 124, as well as the release of the end fitting and mechanical interface. In addition this also activates a localization beacon 126. The bottle 108 is then buoyed to the surface. Once back at surface, the bottle 108 can be located and retrieved by a surface support vessel 128.
In
The mechanical and hydraulic fluid interfaces are based on standardized stab plates 134 including electrical and hydraulic connections, as well as hydraulic valves 136 and 138. The valves 138 are closed when a skid 22 is engaged on top of it. In all other circumstances the valves 136 and 138 are open. The mechanical interfaces of the stab plates 134 and valves 136 and 138 are the same on top of the phase separator as they are on the skids 22. In this way the skids 22 can be stacked in any configuration on top of the separator 30.
The valves 136 and 138 are configured to connect the fluid sampling lines 46 with the extraction line 130. As the skids 22 are connected one on top of another, the valves 138 from the lower skids are closed while the upper valves 136 are opened. The valves 138 of the lower skid 22 are closed when the upper skid connects to it. This takes place after hydraulic connection is completed. The configuration of the valves 136 and 138 allows the liquid to circulate from the separator 30 to the upper skid 22.
Fluid sampling and analysis devices 26 are located between the sampling pipes 44 and the extraction pipes 130. There may be a pump 132 associated with these devices 26 in order to circulate the fluid from the sampling line 44 to the extraction line 130. This configuration as shown in
Another important feature of the invention is the use of subsea fluid analysis measurement by apparatus 10 to be used to control subsea equipment. The information from the apparatus 10 can be used, for example to control subsea equipment in a fully automated mode, or to control subsea equipment from the surface using the information obtained from apparatus 10. Different controllers/communication modules 28 are connected in a network configuration with, for example, an Ethernet architecture, which allows communication and control between the different skids 22. The information can either be sent to the surface or processed at seabed level for the direct management of the control of other subsea modules.
In a fully automated mode, the information obtained from the sensors is directly processed at the seabed and a decision is made at subsea apparatus 10. The information can be used to optimize choke opening for example. Another possible example is the optimization of chemical or water injection and the optimization of phase separator operating conditions. The information can also be sent to the surface for human based interpretation and decision making.
Another important feature of the subsea apparatus 10 and method according to the invention is the ability to combine the measurements obtained from the fluid sensors of devices 26 in apparatus 10 with the measurements obtained from other sensors on the seabed.
One possibility is to combine fluid analysis results with multiphase flow meter measurement for flow assurance prediction. The measurement results can be fed to simulation software such as OLGA® to predict possible flow assurance problems along the subsea installation. For example, in a case where OLGA® is handling 1D dynamic simulation of fluid phase behavior along the subsea piping installation. It allows simulation from the wellhead to the surface. Critical inputs for this type of software are phase diagrams as well as the respective flow of each phase (water, oil and gas) of the fluid. A phase diagram of each phase can be obtained from a PVT sensor as illustrated in
Another possibility is the use of composition measurement. A gas chromatograph could be installed on the fluid sampling or analysis device 26 to be used for analysis so as to provide the detailed composition. Combined with equation of state this could provide a phase diagram for each phase.
The apparatus 10 and method according to this invention in combination with multiphase flow meter data may be used to obtain real-time flow assurance prediction by feeding fluid properties directly into the software models that are used for this purpose. This would allow the control of subsea equipment to optimize production condition.
Flow assurance problems are likely to happen during installation shut-down, therefore, providing updated information on fluid behavior just before the shut-down would be able to help provide better management of the installation.
Another possible application of the apparatus and method according to the invention is its use for the optimization of chemical injection. Many chemicals are injected at different points in a subsea installation to manage a flow assurance problem. By sampling the fluid at the injector output after the inhibitor is mixed with the production fluid, it is possible to assess the efficiency of the chemical treatment and optimize the quantity of chemical to be injected. For example, the measurements of a phase behavior analyzer can be used to assess the efficiency of the treatment. By comparing the phase behavior in real time, with the operation safety envelop, it is possible to optimize the volume or the type of chemical injected.
The measurement from the fluid sampling or analysis device 26 can also be used for a more accurate estimation of the flow rate from each of the different phases from a multiphase flowmeter. An important input parameter of a multiphase flow meter used in the oil and gas industry is the density of each phase. The fluid analysis device of
In the subsea configuration of equipment illustrated in
| Number | Date | Country | Kind |
|---|---|---|---|
| 0810189.1 | Jun 2008 | GB | national |
