SUBSEA SAMPLING SYSTEM AND METHOD

Abstract

A system and method are provided for collecting fluid samples from a fluid flowline located subsea. The system includes a multiphase sampling apparatus attachable to the flowline, and a vehicle sampling apparatus that is connectable to the multiphase sampling apparatus to allow the transfer of the collected fluid sample thereto. The vehicle sampling apparatus is preferably a subsea remotely operated vehicle (ROV) locatable proximate the fluid flowline and having a fluid sample collector and a fluid pump for transferring the collected fluid sample from the multiphase sampling apparatus to the fluid sample collector. The vehicle sampling apparatus includes a fluid analysis sensor capable of extracting information about the collected fluid sample at a subsea location. Optionally, the vehicle sampling apparatus can transport the collected fluid sample to a location remote from the fluid flowline for analysis.

Description

CROSS REFERENCE TO RELATED APPLICATIONS

The present disclosure is based on and claims the benefit of priority from U.S. Provisional Patent Application Ser. No. 61/160,446 of Brown et al, entitled “SUBSEA SAMPLING SYSTEM AND METHOD,” filed on Mar. 16, 2009; U.S. Provisional Patent Application Ser. No. 61/166,998 of Brown et al, entitled “SUBSEA SAMPLING SYSTEM AND METHOD,” filed on Apr. 6, 2009; U.S. Provisional Patent Application Ser. No. 61/232,487 of Brown et al., entitled “ISOTHERMAL SUBSEA SAMPLING SYSTEM AND METHOD,” filed on Aug. 10, 2009; and U.S. Provisional Patent Application Ser. No. 61/285,323 of Theron et al, entitled “SUBSEA SAMPLING SYSTEM AND METHOD,” filed on Dec. 10, 2009; the entire contents of the disclosures of which are hereby incorporated by reference.

TECHNICAL FIELD

The present disclosure relates generally to sampling fluids in the oil and gas industry. More particularly, the present disclosure relates to an apparatus, system and method for sampling fluids subsea.

DISCUSSION OF THE BACKGROUND

In the oil and gas industry, fluid samples are collected for analysis in many well applications. For example, in a subsea environment tubing is used to convey well fluid to a desired location. Measurements and samples of the fluid moving through the tubing can provide useful information for improved operation of the well.

Fluid samples, for example, may be collected for reservoir characterization or to deduce reservoir fluid properties. The analysis generally is done at a land-based or field-deployed pressure/volume/temperature (PVT) laboratory. The information derived is used for periodic reservoir characterization over the life of a well to facilitate the evaluation of reserves, and for production planning and optimization.

Fluid samples are also collected to enable deposition studies, for example, samples may be collected to carry out asphaltene deposition studies. In subsea applications, problematic deposition of such materials can occur as a result of the temperature and pressure gradients between a subsea wellhead and the surface.

In many of these same well applications, PVT data and hydrogen sulphide (H₂S) level data are used to facilitate optimization of a well fluid production. The PVT data, for example, can be used to correct volumetric correlations applied to flow meters, pipelines and other downstream assets. However, the detection of the various well parameters and the taking of samples for further analysis can be difficult and/or inefficient, particularly in certain environments, such as subsea environments.

Subsea sampling can be applied to single-phase or multiphase fluids. When the fluid is multiphase, the phases can be collected separately and analyzed independently. This information can be used to reduce the uncertainty of the results obtained by using multiphase flow meters.

Various apparatus, methods and systems for sampling and analyzing well fluids have been identified previously, including those used subsea. 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.

International Patent Application PCT/EP2008/050445, published as WO 2008/087156, discloses a system and method for analysis of fluid samples. An article entitled “Improved Production Sampling Using the Framo Multiphase Flow Meter,” by Framo Engineering AS (October 1999) discusses a multiphase flow meter used in fluid sampling, including subsea with the aid of remotely operated vehicles (ROV).

Other technologies such as Schlumberger's MDT sampling and analysis technologies have also been used for subsea sampling and analysis of fluids in the oil and gas industry. A further well-known system used by Schlumberger for sampling fluids in the oil and gas industry is the PhaseSampler system and method.

SUMMARY OF THE INVENTION

In view of the foregoing disadvantages, problems, and insufficiencies inherent in the known types of methods, systems and apparatus present in the prior art, exemplary implementations of the present disclosure are directed to novel methods and systems for sampling fluids subsea.

According to an aspect of the present disclosure, a system for collecting fluid samples from a fluid flowline is provided, the system including a multiphase sampling apparatus and a vehicle sampling apparatus. The multiphase sampling apparatus is attachable to the flowline so as to collect a multiphase fluid sample from the flowline. The vehicle sampling apparatus is locatable proximate the fluid flowline, and is connectable to the multiphase sampling apparatus to allow transfer of the collected fluid sample thereto. The vehicle sampling apparatus includes a fluid sample collector, and a fluid pump that transfers the fluid sample from the multiphase sampling apparatus to the fluid sample collector.

The vehicle sampling apparatus may further include at least one fluid analysis sensor capable of analyzing the collected fluid sample. Optionally, the vehicle sampling apparatus is capable of transporting the collected fluid sample to a location remote from the fluid flowline for analysis.

The multiphase sampling apparatus may include a sampling probe that is insertable into the fluid flow of the flowline and able to collect a fluid sample, and the vehicle sampling apparatus may include a fluid connector which allows the fluid sample collected by the multiphase sampling apparatus to be transferred to the vehicle sampling apparatus.

The system is preferably locatable subsea. In such an exemplary embodiment of the present disclosure, the vehicle sampling apparatus is preferably a subsea remotely operated vehicle (ROV) having the aforementioned fluid analysis sensor capable of analyzing the collected fluid sample. In such an embodiment, the fluid analysis of the collected sample may be performed either subsea or at surface. The fluid analysis sensor may include sensors for measuring the nuclear attenuation of a gamma ray source one phase at a time at line conditions.

The system may further include a plurality of fluid pumps which may be used for returning the fluid sample back into the fluid flowline, pressure testing the ROV connection, tuning a flow conditioner, maintaining line conditions within the fluid sample collector, unblocking or cleaning the sampling probe, the fluid connector or flowline, and/or deploying the sampling probe. Furthermore, the ROV may include a full bore pipeline bypass for simplifying the intervention of the sampling probe.

Preferably the sampling probe may be inserted into the fluid flow of the flowline by means of an extension mechanism when a sample is to be collected. Further, the sampling probe may be retractable from the fluid flow of the flowline by means of the extension mechanism when the sampling probe is not to be used for taking a sample. The sampling probe may include at least one fluid analysis sensor.

In one aspect of the present disclosure, the multiphase sampling apparatus is permanently attached to the fluid flowline. In another aspect of the present disclosure, the multiphase sampling apparatus is locatable proximate the fluid flowline. In a further aspect of the present disclosure, the multiphase sampling apparatus is locatable on the vehicle sampling apparatus.

Further in accordance with an aspect of the present disclosure, there is provided a fluid enrichment mechanism for enriching the sample fluid. The enrichment mechanism of the collected fluid sample may further include a separation means for separating the phases of the multiphase fluid sample. The enrichment mechanism may further include means for separately storing the phases of the fluid sample which are of interest and the enrichment mechanism may be capable of returning the unwanted phases of the fluid sample to the flowline.

According to another aspect of the present disclosure, a system for collecting fluid samples from a subsea fluid flowline is provided, the system including a multiphase sampling apparatus attachable to a subsea fluid flowline so as to be in communication with the fluid flow in the flowline, the multiphase sampling apparatus including a flow conditioner and sampling connector that may selectively communicate with the fluid flow for selective collection of a suitable fluid sample; and a vehicle sampling apparatus adapted for connection to the multiphase sampling apparatus, the vehicle sampling apparatus including a fluid connector capable of transferring the fluid sample between the multiphase sampling apparatus and the vehicle sampling apparatus; a fluid sample collector adapted to contain the fluid sample for a selected period of time; a fluid pump in communication with the fluid connector, and at least one fluid analysis sensor operable from a location remote from the multiphase sampling apparatus.

The fluid analysis sensor of the vehicle sampling apparatus may include a gamma ray attenuation sensor that may measure the nuclear attenuation of a gamma ray source one phase at a time, e.g. the measurement may be done at line conditions in the vehicle sampling apparatus with gas only and then with liquid only.

The system may further include a plurality of fluid pumps for returning the fluid sample back into the fluid flowline, pressure testing the ROV connection, tuning the flow conditioner, maintaining line conditions within the fluid sample collector, unblocking or cleaning the sampling probe, the fluid connector or flowline, and/or deploying the sampling probe.

In another aspect of the present disclosure, the vehicle sampling apparatus may provide full bore pipeline bypass for intervention of the multiphase sampling apparatus.

Another aspect of the present disclosure provides a method for collecting and analyzing fluid samples from a fluid flowline, the method including the steps of: attaching a multiphase sampling apparatus to a fluid flowline; collecting a fluid sample; attaching a vehicle sampling apparatus to the multiphase sampling apparatus; and transferring the fluid sample from the multiphase sampling apparatus to a fluid sample collector of the vehicle sampling apparatus by means of a fluid pump included in the vehicle sampling apparatus.

The method may further include the step of obtaining fluid information relating to the fluid sample from at least one fluid sensor locatable on the vehicle sampling apparatus; and relaying the fluid information to a remote position.

The method may also further include the steps of inserting a sampling connection of the multiphase sampling apparatus into the fluid flowline and collecting a multiphase fluid sample, and connecting fluid conduits between the multiphase sampling apparatus and the vehicle sampling apparatus prior to transferring the collected sample to the vehicle sampling apparatus.

The step of relaying the fluid information may further include disconnecting the vehicle sampling apparatus from the multiphase sampling apparatus; and transporting the fluid sample to a position remote from the fluid flow line.

Optionally, the step of relaying the fluid information may include discarding at least a portion of the fluid sample into the fluid flowline by means of a fluid pump included in the vehicle sampling apparatus; transmitting the fluid information to a remote position via a communication channel between the vehicle sampling apparatus and the remote position, and disconnecting the vehicle sampling apparatus from the multiphase sampling apparatus.

Preferably the method is performed subsea. In this aspect, the vehicle sampling apparatus is a subsea remotely operated vehicle (ROV).

In accordance with an aspect of the present disclosure, the multiphase sampling apparatus may include a flow conditioner having a fluid connector. The sampling connector may be insertable into the fluid flowline by an extension mechanism, or connectable to the fluid connector of the flow conditioner. The extension mechanism may operate telescopically.

Further according to an aspect of the present disclosure, the method may further include analyzing the collected fluid sample utilizing a fluid analysis sensor.

Additionally, the method may include enriching the collected fluid sample. The enrichment of the collected fluid sample may include the steps of separating the phases of the multiphase fluid sample, storing the phases of the fluid sample which are of interest and returning the unwanted phases of the fluid sample to the flowline.

The method may also include the step of pressure testing the multiphase sampling apparatus utilizing the fluid pump included in the vehicle sampling apparatus.

The method may also include changing the flow regime of the flow conditioner utilizing the fluid pump of the vehicle sampling apparatus, cleaning the fluid conduits utilizing the fluid pump included in the vehicle sampling apparatus, and cleaning the sampling probe utilizing the fluid pump included in the vehicle sampling apparatus. In one aspect of the present disclosure, the method may include pumping unwanted fluid back into the flowline utilizing the fluid pump.

According to another aspect of the present disclosure there is provided a sampling probe for use with the system and method as described above.

One of the advantages provided by the current system and method for monitoring and analysis of fluids in a flowline is that it allows the use of systems and methods for sampling and analysis of fluids to be implemented in the subsea environment while keeping the sample fluid at line conditions. A further advantage is that the sample probe is removable from the flowline and may therefore be more protected from damage and clogging. Another advantage is the representivity of the sampling process, i.e. the sample phases can be selected and adequate quantities from these sample phases can be captured through an enrichment process. Another advantage is the capability of “no-sample-to-surface” concept wherein a fluid sample may be collected, analyzed on the ROV skid, and discarded back into one of the flowlines. An exemplary system and method of the present disclosure also allows for convenient cleaning and unblocking of the sample probe and sample fluid conduits.

Even further, the system and method can be adjusted subsea and thus used for a very wide range of fluids encountered subsea, from lean gas to heavy oil. The ability for the system to be adjusted is enhanced by the use of selected sensors which are deployed with the system, and which allow for the selective sampling of fluids of interest.

The disclosure also provides a method and system for taking oil water and gas samples in subsea environment under a large range of flowing conditions: high to low gas volume fraction (GVF) and water liquid ratio (WLR), even when there is solid debris present. The disclosure provides a method and system for obtaining in a controlled manner, samples of a multiphase mixture from a line in a subsea environment and separating, via an enrichment process, monophasic samples of water, gas and or oil.

The system and method of the present disclosure include a subsea sampling device preferably permanently or semi-permanently attached to the flowline or wellhead for capturing a multiphase sample from the flowline or wellhead. In one embodiment, subsea sampling device is as a commercially available device called subsea sampler and offered by Framo Engineering. The system further includes a remotely operated vehicle (ROV) sampling skid assembly and a device for docking the ROV to the permanently installed sampling device and making all electrical, fluid and communication connections as necessary. The ROV sampling skid is equipped with an enrichment system for separating oil, water or gas samples from the multiphase sample, as well as a device for storing the separated samples in pressurized bottles. Upon docking of the ROV skid to the permanently installed sampling device, the sampling sequence is initiated to transfer a sample taken from the permanently installed subsea sampling device to the ROV skid sample enrichment process. Monophasic samples are then collected and stored in the pressurized bottles on the ROV skid. The ROV skid can then transfer the samples to a surface facility. The system further includes a device for ensuring that the samples that are taken are representative (e.g., in terms of composition) of the phases flowing at flowline or well head conditions (e.g., in terms of pressure and temperature). The system allows the taking of sufficient quantities of monophasic samples to enable further fluid analysis, as needed.

It should be understood that the first stage of the process, for example, connecting to the sample point of interest at the line or wellhead or some other subsea location as may be desired and getting sample fluids can be performed in several ways. In one embodiment, a commercially available sampling port system offered by FRAMO Engineering can be used.

Advantageously, the method and system of the present disclosure allow for sampling in flows where some solid debris is encountered. The method and system also allow for separation of the oil/water/gas in large enough volumes for the full range of WLR and GVF via “phase enrichment.” The enrichment process is made at the same or substantially the same temperature and pressure as the flowing production line to avoid phase composition changes. The enrichment process is continuous and the un-wanted fluids are re-injected into the line. Two possible variations of the enrichment include performing enrichment inside the sampling bottles themselves in conjunction with a phase identification probe, and performing enrichment in a sub-unit made of a gas-liquid and an oil-water mini separator. Other variations may be envisioned from those skilled in this art without departing from the present disclosure as described in this application.

The samples obtained are taken back to the surface in constant volume bottles, where further enrichment can be made, if necessary. Additionally, oil/water phase present in gas bottle can be transferred to oil or water bottles, by way of complimentary services on surface. The ROV skid assembly may connect and disconnect to ports installed at the sampling location nearby the wellhead or the flowline.

These together with other aspects, features, and advantages of the present disclosure, along with the various features of novelty, which characterize the disclosure, are pointed out with particularity in the claims annexed to and forming a part of this disclosure. The above aspects and advantages are neither exhaustive nor individually or jointly critical to the spirit or practice of the disclosure. Other aspects, features, and advantages of the present disclosure will become readily apparent to those skilled in the art from the following description of exemplary embodiments in combination with the accompanying drawings. Accordingly, the drawings and description are to be regarded as illustrative in nature, and not restrictive.

BRIEF DESCRIPTION OF THE DRAWINGS

The disclosure will be better understood and aspects other than those set forth above will become apparent when consideration is given to the following detailed description thereof. Such description of the present disclosure is illustrated by way of example, and not by way of limitation, to the annexed pictorial illustrations, graphs, drawings, and appendices, in which like reference numerals refer to similar elements, and in which:

FIG. 1 depicts a schematic overview of a sampling system attached to a flowline and attachable to an ROV according to an exemplary embodiment of the present disclosure;

FIG. 2 depicts a schematic overview of an extendable probe sampling system attachable to a flow line and attachable to an ROV according to another exemplary embodiment of the present disclosure;

FIG. 3 depicts a schematic side view of a sampling probe apparatus according to an exemplary embodiment of the present disclosure;

FIG. 4 depicts a schematic side view of a sampling probe apparatus according to a further exemplary embodiment of the present disclosure;

FIG. 5 depicts a schematic overview of a sampling system having a flow conditioner attachable to an ROV according to an exemplary embodiment of the present disclosure;

FIG. 6 depicts a schematic overview of a system and method for sampling gas subsea, according to another exemplary embodiment the present disclosure;

FIG. 7 depicts the exemplary system and method of FIG. 6 for water enrichment subsea, according to the present disclosure; and

FIG. 8 depicts the exemplary system and method of FIG. 6 for oil enrichment subsea, according to the present disclosure.

DETAILED DESCRIPTION

Specific embodiments of the present disclosure will now be described in detail with reference to the accompanying drawings. Further, in the following detailed description of embodiments of the present disclosure, numerous specific details are set forth in order to provide a more thorough understanding of the disclosure. However, it will be apparent to one of ordinary skill in the art that the embodiments disclosed herein may be practiced without these specific details. In other instances, well-known features have not been described in detail to avoid unnecessarily complicating the description.

The terminology and phraseology used herein is solely used for descriptive purposes and should not be construed as limiting in scope. Language such as “including,” “comprising,” “having,” “containing,” “consisting of,” or “involving,” and variations thereof, is intended to be broad and encompass the subject matter listed thereafter, equivalents, and additional subject matter not recited.

“Isothermal” as used herein refers to a process that takes place with minimal temperature change. Likewise, “isobaric” as used herein refers to a process that takes place with minimal pressure change. For example, “isothermal sampling,” “isobaric sampling,” “at line conditions,” and variations thereof, as used herein refer to sampling a predominant phase of a multiphase fluid without substantially changing its composition or state.

A first embodiment of a system 10 for fluid sampling and analysis in a flowline 12 according to the present disclosure is depicted in FIG. 1. The flowline 12 to which the system 10 according to the present disclosure may be applied is preferably for use in the oil or gas industry.

The present disclosure relates preferably to a system and a method for the removal, analysis and/or conditioning of fluid, that is, liquid (e.g., oil and water) and gas, from subsea pipelines and seabed production equipment containing multiphase fluid flow across a broad range of fluid types from gas condensates to heavy oils. The present disclosure incorporates a multiphase fluid sampling and analysis apparatus and enrichment process for pressure/volume/temperature (PVT) quality samples obtained directly from the flowlines of pipelines in the oil or gas industry. The present disclosure also incorporates a flow conditioner and sampling connection for a subsea pipeline to perform flow conditioning and sampling of suitable fluid samples. The sampling connection can be modified for various methods of deployment and these embodiments of the apparatus and methods according to the present disclosure are described in more detail below. Isothermal heating and sensors are also disclosed to monitor the fluid characteristics for all the subsea sampling.

In FIG. 1, a sampling apparatus 11 having a subsea sampling probe 14 is depicted at a position on flowline 12 just after an elbow. This position is often used for mixing in a typical Vx flowline. The subsea probe 14 may be permanently positioned in the flowline 12 after being inserted into the flowline 12. The subsea probe 14 may be positioned downward facing, which is opposite to the typical port for a multiphase sampling device, which is upward facing. This is to allow for a remotely operating vehicle (ROV) to have access to the subsea probe 14 from above flowline 12. A valving system is provided that allows an ROV 16 to form a wet-stab connection onto multiple ports at stab plate connection 18 for performing sampling. The ROV sampling system 20 has a pump 22 that allows the fluids in the hydrocarbon flowline 12 to be drawn into the ROV sampling system at a desired rate. The pump 22 is a variable rate, and the flow direction of the pump can be controlled from the ROV 16.

The pump 22 may include a pump cylinder 24, piston 26 and a ball screw 28. The outlet (or exhaust) of the sampling system 20 is returned into the hydrocarbon flowline 12, at line conditions to minimize pressure drop. This results in very little difference in pressure between the inlet and the outlet of the sampling system 20. If the sample taken from the flowline 12 by probe 14 is gas rich with very little liquid, the ROV ball screw pump 22, or an additional pumping device, can be used to exhaust the unwanted gas back to the hydrocarbon flowline 12. The liquid collected may however be kept in the pump cylinder 24 with the use of a suitable water, oil and gas detector. This detector has the ability to measure the phase boundary and interface between the different media, the transition between oil and water, oil and gas, gas and water. The pump's flow direction can be changed to draw in samples and then exhaust undesirable media back into the flowline 12. It will be understood that pump 22 may operate by other means and is not limited to a ball screw type.

Once the desired volume of sample has been obtained by probe 14, the sample can then be pumped into a piston sample bottle 30 located on ROV 16 for retrieval to the surface. There may be a plurality of sample bottles 30 on ROV 16. Alternatively, however, the sample may be analyzed on the ROV 16. The sample may be subsequently transported to surface by the ROV 16, or may be exhausted back to the hydrocarbon flowline 12, as described herein. A more detailed discussion of the fluid analysis means is provided hereinafter.

The pump 22 also can be used to pump debris from the probe 14 if it becomes plugged during use. The ROV 16 can supply power to heat the probe 14 assembly to minimize temperature gradients which can lead to heavy wax formation and thus affect the representativity of the sample. This isoheating system may use heat trace type elements or circulate hot water to provide an isothermal environment for sampling and analysis. This enables the fluid sample to be kept at line conditions.

The fixed probe 14 of the embodiment depicted in FIG. 1 is connected to a manifold via hydrocarbon capable wet-connects (not shown). Also depicted in FIG. 1 are pressure and temperature sensors 32 that can be used to monitor line conditions. Heating jackets 34 are also provided around the probe 14 manifold 36. Typically, these heating jackets would also extend along the full length of the sampling flowlines 38 from a sampling point at probe 14 to the sample bottle 30, including the pump cylinder 24. For example, the fixed probe 14 may be an aerofoil shaped probe aimed towards selective enriched sampling from a multiphase fluid mixture flowing at high velocities.

There are two main valves in this embodiment of the present disclosure, namely valve 40 and valve 42. While two main valves 40, 42 are depicted, it is understood that any number of valves may be used in accordance with the present disclosure. Valves 40, 42 allow identified fluids to be drawn into the pump cylinder 24, and then if any undesirable fluids are present, the pump 22 can then push these fluids back into the hydrocarbon flowline 12.

The fluid selection process or enrichment of desired fluids is an advantageous function for sampling of multiple phase fluids. The enrichment of the collected fluid sample includes the separation of the phases of the multiphase fluid sample, the storage of the different phases of the fluid sample, which are of interest, in a sample bottle, and the return of unwanted phases of the fluid sample to the flowline 12. Once the desired fluids are captured in the pump cylinder 24, they can then be pumped through a sampling valve 44 into the sample bottle 30 for retrieval at surface, or may be analyzed by the ROV 16 and exhausted back to the hydrocarbon flowline 12.

The system 10, depicted in FIG. 1, also highlights the use of hydrocarbon capable wet connects between the flowline 38 and the sampling apparatus 11, depicted as stab plate connector 18. There are further electrical connects, namely, a hi-power electrical wet stab connect 46 for heating jackets and an electrical wet-connect 48 for phase, pressure and temperature sensors 59 and other measurements. An advantage of these additional connections being available between the sampling apparatus and the equipment onboard the ROV 16 is that they provide powerful electrical connections for the use of the equipment making up the system 10.

Once the fluid sample has been transferred to ROV 16, the fluid can be characterized, and analyzed subsea in the ROV sampling and analysis skid. The analyzed fluid sample may be returned to surface, or may be exhausted back to the hydrocarbon flowline 12. The latter method may be referred to herein as the “no-sample-to-surface” concept. Such a concept can reduce the turn-around time and health, safety, and environmental risks due to live crude at surface.

The ROV sampling and analysis skid can include any suitable known equipment that makes use of varied forms of any suitable known oilfield fluid analysis technologies. Such analysis technologies are integrated subsea into a multi-phase fluid sampling and analysis tool to be used with the system and method of the present disclosure. Examples of such sampling and analysis technologies that may be employed can include wireline technologies, such as a modular dynamics formation tester, a modular dynamics formation tester-pump out, an optical fluid analyzer, low shock sampling, PVT analysis, gamma ray attenuation, or the like. One analysis scheme may be based on a direct measurement of gamma-ray attenuation across the fluid sample in the hydrocarbon flowline 12, or in the ROV 16. As an example for determining this measurement, at least one detector is placed at a fixed distance (e.g., a few centimeters) from the gamma-ray source, so that the gamma-ray path from the source to the detector is mainly through the fluid sample.

The permanently positioned sampling apparatus 11 in the flowline 12 depicted in FIG. 1 also has the functionality to be ROV replaced for maintenance. During sampling operations, an ROV is deployed and wet mates to this permanently positioned sampling apparatus 11 with probe 14 for sampling operations.

An additional embodiment of a system 10 for fluid analysis in a flowline, preferably for use in the oil and gas industry according to the present disclosure is depicted in FIG. 2. The embodiment depicted in FIG. 2 includes a permanently positioned subsea sampling apparatus 11, but in this embodiment of the present disclosure, subsea probe 14 is not permanently inserted into the flowline, but is positioned to the side of the flowline and may be insertable and extendable into flowline 12 by means of a mechanical extension mechanism or means. The result of this is that probe 14 when not in use is retracted from the flowline and is no longer in contact with the fluid in the flowline. When probe 14 is employed to take samples, it is then deployed into the flowline 12 for sampling. The deployment of the probe 14 is done by applying hydraulic pressure to a hydraulic ram or a telescopic arm. The hydraulic pressure, measurements and isothermal heating for sampling apparatus 11 are obtained from the ROV 16. The ROV 16 provides hydraulic and electrical power, as well as communication to the sampling apparatus 11 and probe 14, for deployment and sampling. An actuator hydraulic pump 50, located on the ROV 16, is connected to a probe actuator assembly 52 for the probe 14. The pump 50 includes an actuator line 54 for extension and an actuator line 56 for retraction.

The extendable effect of the probe 14 and its ability to move up and down by the actuator assembly 52 of the probe 14, as illustrated by double arrow A, enable the probe 14 to be removed from the flowline and protects the probe 14 while not in use. FIG. 2 is shown split into two halves, wherein the probe side is permanent to the subsea infrastructure, and on the other side of the stab plate connector 18, the ROV 16 and ROV sampling system are located. An advantage of this arrangement is that it reduces the risk of plugging and erosion of the subsea sampling probe 14.

The probe 14 can be fully stroked to the sampling apparatus 11 deployed position or the probe 14 can be deployed incrementally to the desired position, depending on the flow regime and fluid types, and in order to get the desired sample from the fluid flowline. In addition, when stroking the probe 14, a phase/fluid detection device (not shown) can be incorporated with the probe 14 to fine-tune the position employed for the desired fluid sample type. It will also be noted that the extendable or telescopic stab plate for probe 14 of FIG. 2 can have additional hydraulic wet-stabs for the probe 14 deployment.

System 10 utilizes metal-to-metal dynamic seals and dual barriers. Standard valve pocket geometry and subsea actuator technology also can be used with system 10, as much as practically possible.

The extendable probe 14 of FIG. 2 also includes an extra probe flush line 58 and two extra flush valves 60. One purpose of these flush valves 60 and the flush line 58 is so that after the ROV 16 connects to the stab plate connector 18, the hydraulic lines of system 10 can be pressure tested before opening the main barrier or seal to the flowline. There are many ways in which this can be done, but it is advantageous to note that the flush line 58 can be pressure tested subsea by the ROV 16 and the main barrier can be opened after a successful test. The sampling circuit of system 10 may be flushed by using the pump 22 prior or after the probe 14 deployment to make sure that sampling lines and flush lines are clear of debris and unwanted fluids. Fluid identification sensors can be used immediately, as the ROV 16 connects to the stab plate connector 18, to indicate fluid types and warn of any potential leakage.

A further embodiment of the system and method for fluid sampling and analysis according to the present disclosure includes a sampling probe 14, which is designed to be positioned at any subsea point that is ROV accessible. This sampling probe 14 extends into the flowline 12 and depending on the mechanics of the extension means may move telescopically in the flowline 12 or extend on a ram. This does not rely on the Vx flowline 12 to enable the sampling probe to be attached only at a position upstream of an elbow portion of the flowline 12 so as to focus fluids for the probe to sample. The probe 14 according to this embodiment of the present disclosure is independent of the geometry of the fluid flowline 12 and this is accomplished by the probe inlet ports, which are capable of being extended across the internal diameter of the fluid flowline 12. The probe 14 can be positioned to allow capture of the desired samples and to accomplish this accurately, an optical phase detector may be located on the probe 14. In this way, it is also possible for the probe 14 position to be moved across the bore of the subsea production flowline 12 for fluid selection prior to sampling.

Examples of sampling probe apparatus, according the present disclosure, are depicted in FIGS. 3 and 4. In FIG. 3, the subsea sampling probe 14 is shown to include a sample chamber 62, a floating piston 64, inlet ports 66, a closing mandrel 68 and seating piston 70. The flowing bore of interest is indicated by line 72 in FIG. 3.

A further embodiment of the system and method for fluid sampling and analysis according to the present disclosure includes the use of a lubricator type probe deployment. In this embodiment of the present disclosure, the sampling probe 14 is completely removed from the subsea manifold in which it is housed during sampling and it is then fitted to the ROV 16. This configuration employs a lubricator type system to pressure seal and deploy the probe 14.

An additional embodiment of the present disclosure includes a sampling apparatus having a flow conditioner 502, as depicted in FIG. 5, such as the flow conditioner disclosed in co-pending U.K. Patent Application Nos. 2406386A and 2447908A, the disclosures of which are hereby incorporated by reference. The flow conditioner 502 can be used to condition flow 504 via inlet 506 for best sampling. The flow conditioner 502 may be adapted to fit any size flange, or sampling connection and flow regime, according to well specifications, and includes an outlet 520. The connections 510 with the flow conditioner 502 are operable through the ROV 16, and are often referred to as hot-stab connections.

Further advantages of utilizing the flow conditioner 502 with the presently disclosed system include the ability to separate a fluid sample into suitable liquid samples 512 from output 514 or gas samples 516 from output 518. As an example, separation means may include: cyclonic separation, inline cyclonic separation, gravity separation, mechanical separation, and/or secondary separation. The flow conditioner 502 having separation capabilities may be permanently or temporarily connected to the flowline 12. Alternatively, the flow conditioner 502 may be incorporated as part of the ROV 16 skid (not shown), thereby allowing customized flow conditioning of fluid without the need for permanent placement. Such a flow conditioner of an ROV may be adapted for connection with a flow conditioner of the multiphase sampling apparatus. The method for collecting a fluid sample using the flow conditioner 502 is similar to the method described with reference to FIG. 1.

Additional embodiments of the present disclosure may further include a full bore pipeline bypass in the ROV 16, thereby improving the intervention of flow conditioners, sampling connections and sampling probes. Full bore pipeline bypass provides the advantage of more controlled isoheating and isobaric sample collection. Furthermore, full bore pipeline bypass provides a method for obtaining a flow sample using complex probes and sensors which are impractical for permanent installation on a subsea fluid flowline system. A full bore bypass in the ROV 16 may be integrated with a flow conditioner, also included in the ROV 16.

The pressure testing and flushing of the wet stabs are an additional aspect of an exemplary embodiment of the current disclosure. Once all valves have been tested, opened and flushed, the sampling collection operation can commence. Once complete, the sample system 10 again can be flushed to clean up all the lines for storage. Again, the fluid sensors in the internal diameter of the flowline can be used to indicate when the hydrocarbons have been removed from the flowlines for safe retraction of the sampling probe. Once this has been done, the main hydrocarbon barriers can be closed, and can then be pressure tested. Once the operation is complete, the ROV 16 can disengage and return to surface with samples.

The flushing and pressure testing of sampling valves, probes and lines can be done by the ball-screw pump 26 or the actuator hydraulic pump 50. The flushing fluid can come from the sea or from the ROV 16. Typically, during flushing and sample purging of the sample lines, and which provide first hydrocarbons after the flushing, the waste fluid can be exhausted into the production pipeline. The sensors in the system also can be used to check the purge fluid content.

There is provided a variation of the system 10, wherein an extendable probe overlaps with the system using the lubricator option. With the lubricator option, the flowlines full bore is opened to support an intervention of any suitable variety, such as deployment of wireline tool or some other large device for taking samples from the flowline. Advantageously, this option allows for the capture of the sample at line pressure and temperature. With the use of two barriers valves, the system may also use BOP (blow out preventer) technology for probe deployment.

Line pressure is relatively straight forward to maintain, as the pressure is a function of flow rate, which can be easily controlled by the ball screw pump 26. However, temperature is more complicated and the temperature gradients can be quite severe. For the samples to be representative, they are typically caught at line conditions. If the temperature varies from the sampling point to the sample, the fluid can change in equilibrium during its travel from the sampling point to the sample and thus produce unrepresentative measurements. A technique presented for overcoming such a problem is to capture the sample in the sample probe. An advantage to this method is that there would be less need for heating of the system during sampling.

With limited space for the probe and the probe sample bottle design, a second probe can be used that may be 180° opposite to allow added functionality to take place. This has been depicted in FIG. 2. For example, a probe 14 from the opposite flange can be used to seal the sample into the probe sample bottle or to pump out any unwanted fluids from the probe or to transfer as heating is applied to the system and keep the samples at flowline conditions.

In FIG. 4, an inlet port 66 is depicted on the probe 14 having an enrichment cylinder 74, which may be at flowline pressure and temperature conditions. A transfer probe 76 is further depicted opposite the probe 14 and this transfer probe 76 closes the inlet port 66 of the enrichment cylinder 74, and thereby allows the fluid sample to be transferred at flowline pressure and temperature.

The pump that can be used with the system and method of the present disclosure may also provide interactive control of the sampling rate and the pressure drop. The pump may further be used to unblock the probe by pumping fluids through it or it may be used to remove debris from the probe. Even further, the pump may be used to pressure test lines prior to and after sampling.

Subsea analysis can be done in the ROV 16, while attached to the subsea production pipe or while en route to another sampling point. Fluid samples also may be retrieved back to surface for further analysis.

FIG. 6 illustrates another exemplary system and method for sampling fluids subsea. FIG. 6 is used for illustrating the sampling gas from a top port and shows the various components of the system according to one embodiment of the disclosure. Referring to FIG. 6, the method of present disclosure includes the following steps:

Step 1: A remotely operated vehicle (ROV) sampling skid assembly 601 connects remotely to a subsea, permanently installed subsea sampler 602.

Step 2: A flushing module 603 pressurizes the system and makes the pre-job pressure test.

Step 3: A volumetric piston pump 604 and a set of valves creates a flow stream between the two ports of the subsea sampler ports 605 and 606 via various internal pipes prefilled with a buffer fluid. This step allows removal the buffer fluid and allows adjustment of the piston pump regime to optimize the phase to be sampled. During this step, the phases are identified using phase detector probes (e.g., optical probes).

Step 4: The valves are set to direct a gas sample to the gas sampling bottle 607, while the buffer fluid from a back piston of the sampling bottle 607 is released to an exit port. The bottle 607 filling is stopped when the pressure in the bottle 607 starts to increase.

Steps 5 and 6: Using bottles 608 and 609, these steps are similar to step 4, except that the valves are set to move the liquid sample from the predominantly liquid port 606.

A further step of water enrichment can be performed by deviating the bottle 609′ by few degrees up or down, as shown in FIG. 7, depending on whether or not water or oil is to be accumulated. This process makes use of the specific configuration of the sampling bottles 607, 608, 609, which have two connection ports on their end caps. Both ports are located on a vertical diameter, forming a low port 611 and a top port 610. The port 610 of the bottle 609′ is open to let the flow through, wherein the sample stream continues to flow within the bottle 609′ and segregates by gravity. For concentrating water, as shown in FIG. 7, the bottle 609′ is deviated upward by few degrees (e.g., about 10 deg), wherein the sample stream enters the bottle 609′ via the low port 611 and exits via the top port 610. Within the bottle 609′, the water accumulates via gravity, wherein the sampling is stopped when the phase detectors (e.g., optical probe 612, 613) start to detect water coming out from the bottle 609′. Advantageously, such a mechanism allows for capturing of water, even for very small water liquid ratio (WLR) in the line, wherein in this case the sampling time will be longer than for a larger WLR. A similar process, but with the bottle 609′ deviated downward can be used to concentrate oil from a liquid sample stream.

Step 7: The bottles are securely closed by a bulkhead manifold and the subsea sampler 602 valves closed.

Step 8: The flushing module 603 pressurizes the system and makes the post-job pressure test. The system then disconnects and the ROV skid 601 returns to the surface.

One advantage of this system is its ability to selectively sample from the two ports of the line to be able to collect and enrich the phase samples at line conditions pressure and temperature (P, T).

The enrichment process of the system described in FIGS. 6 and 7 may be somewhat limited for the case where oil enrichment is employed and the liquid sample stream contains a small amount of gas. In these conditions, gas may accumulate in the oil bottle during the enrichment process, thus inhibiting the enrichment of the oil sample. In some cases, the sample may end up full of gas.

Another embodiment of the present disclosure is shown in FIG. 8. The system and method of FIG. 8 is suitable for enriching an oil sample from a liquid sample stream even when the sample contains some gas. Referring to FIG. 8, the phase separation during the sampling steps 4, 5 and 6 is made using two small separators, one separator 614 for gas/liquid and another 615 for oil/water. The sample stream generated by the piston pump is first sent to the gas liquid separator 614, where liquid segregates from gas via gravity. The level in the separator is controlled by on/off valves and three phase detectors (e.g., optical probes, 616, 617, 618). The gas is directed to the gas bottle or diverted to an exit if the bottle is full.

The liquid stream is directed to the liquid separator 614, where the oil and water levels are also controlled by two phase detectors (e.g., optical probes, 619, 620) and on/off valves. Both phase streams are then directed to the adequate bottles until full or diverted to an exit. This embodiment offers, among other things, the following additional advantages:

It is less dependent upon the quality of the primary sample stream and thus, can work as long as the three phases are available in the sample stream. Advantageously, this provides more flexibility on the sampling ports installed on the line. Also, the sampling bottles do not require being at well temperature, like in the previous embodiment, and the compactness of the system is improved and therefore easier to operate.

An additional component of the disclosure is the inclusion of a thermal management system (e.g., passive or active), and which facilitates the sample process to take place isothermically with respect to flowing product line conditions. The heating systems (e.g., shown with “X” and “Y” in FIGS. 6-8) may be partitioned to allow separate heating zones to be controlled. Advantageously, this allows the bottle section to be thermally controlled on an independent or interlocked basis with the heating zone surrounding the sample process pump and valves. Zonal separation also allows for differing heating media to be applied, such as oil or water jacket heating systems, electric blankets, and the like.

The heating zones can be set preferably to line condition temperatures prior to and during the sample process. The temperature level to be set can be defined either by manual input, or in an automated manner, for example, by way of link to a temperature sensor (e.g., either located on the skid 601 or located within the permanently installed sample system/line conditioner). The heating systems are linked to the sampling skid 601 control system, and monitored at the surface.

Although the present disclosure has been described with reference to exemplary embodiments and implementations thereof, the present disclosure is not to be limited by or to such exemplary embodiments and/or implementations. Rather, the systems and methods of the present disclosure are susceptible to various modifications, variations and/or enhancements without departing from the spirit or scope of the present disclosure. Accordingly, the present disclosure expressly encompasses all such modifications, variations and enhancements within its scope.

Claims

1. A system for collecting fluid samples from a fluid flowline, comprising:

a multiphase sampling apparatus attachable to the fluid flowline which is able to collect a multiphase fluid sample from the fluid flowline; and

a vehicle sampling apparatus locatable proximate the fluid flowline, connectable to the multiphase sampling apparatus, and operable to transport the collected fluid sample remotely from the fluid flowline, said vehicle sampling apparatus including a fluid sample collector, and a fluid pump that transfers the collected fluid sample from the multiphase sampling apparatus to the fluid sample collector.

2. The system of claim 1, wherein the vehicle sampling apparatus further includes at least one fluid analysis sensor capable of analyzing the collected fluid sample.

3. The system of claim 2, wherein the fluid analysis sensor is capable of providing a sample analysis at a subsea location.

4. The system of claim 1, wherein the multiphase sampling apparatus further includes a sampling probe which is insertable into the fluid flow and which is able to collect a multiphase fluid sample from the fluid flowline.

5. The system of claim 4, wherein the sampling probe is insertable into the fluid flowline by an extension mechanism when a sample is to be collected.

6. The system of claim 5, wherein the sampling probe is retractable from the fluid flow of the flowline by means of the extension mechanism when the sampling probe is not to be used for taking a sample.

7. The system of claim 4, wherein the sampling probe includes at least one fluid analysis sensor.

8. The system of claim 1, wherein the vehicle sampling apparatus further includes a fluid connector which allows the transfer of the fluid sample collected by the multiphase sampling apparatus to the vehicle sampling apparatus.

9. The system of claim 1, which is locatable subsea.

10. The system of claim 1, wherein the vehicle sampling apparatus is a subsea remotely operated vehicle.

11. The system of claim 1, further comprising a fluid enrichment mechanism that enriches a selected phase of the sample fluid.

12. The system of claim 11, wherein the fluid enrichment mechanism for the collected fluid sample further includes a separator that separates the phases of the multiphase fluid sample.

13. The system of claim 12, wherein the fluid enrichment mechanism stores the phases of the fluid sample which are of interest and returns unwanted phases of the fluid sample to the flowline.

14. The system of claim 1, wherein the multiphase sampling apparatus is permanently attached to the fluid flowline.

15. The system of claim 1, wherein the multiphase sampling apparatus is locatable proximate the fluid flowline.

16. The system of claim 1, wherein the multiphase sampling apparatus is locatable on the vehicle sampling apparatus.

17. The system of claim 1, wherein the fluid pump of the vehicle sampling apparatus functions further to clean the fluid flowline.

18. The system of claim 4, wherein the fluid pump further functions to clean the sampling probe.

19. The system of claim 1, wherein the vehicle sampling apparatus further includes a flow conditioner.

20. A system for collecting fluid samples from a fluid flowline, comprising:

a multiphase sampling apparatus attachable to a subsea fluid flowline so as to be in communication with a multiphase fluid flow in the flowline, and including a flow conditioner and sampling connection that selectively communicates with the fluid flow for selective collection of a fluid sample; and

a vehicle sampling apparatus connectable to the multiphase sampling apparatus and including a fluid connector capable of transferring the fluid sample between the multiphase sampling apparatus and the vehicle sampling apparatus; a fluid sample collector adapted to contain the fluid sample for a selected period of time; a fluid pump in communication with the fluid connector; and at least one fluid analysis sensor operable from a location remote from the multiphase sampling apparatus.

21. A method of collecting and analyzing fluid samples from a fluid flowline, comprising the steps of:

attaching a multiphase sampling apparatus to a fluid flowline;

attaching a vehicle sampling apparatus to the multiphase sampling apparatus, and

transferring the fluid sample from the multiphase sampling apparatus to a fluid sample collector of the vehicle sampling apparatus by means of a fluid pump included in the vehicle sampling apparatus.

22. The method of claim 21, further including the steps of:

obtaining fluid information relating to the fluid sample from at least one fluid sensor locatable on the vehicle sampling apparatus; and

relaying the fluid information to a remote position.

23. The method of claim 21, further including the steps of:

collecting the multiphase fluid sample by inserting a sampling probe of the multiphase sampling apparatus into the fluid flowline; and

connecting fluid conduits between the multiphase sampling apparatus and the vehicle sampling apparatus prior to transferring the collected fluid sample from the multiphase sampling apparatus to the sample collector of the vehicle sampling apparatus.

24. The method of claim 22, wherein the step of relaying the fluid information further comprises:

disconnecting the vehicle sampling apparatus from the multiphase sampling apparatus; and

transporting the fluid sample to a position remote from the fluid flow line.

25. The method of claim 22, wherein the step of relaying the fluid information further comprises:

discarding at least a portion of the fluid sample into the fluid flowline by means of the fluid pump included in the vehicle sampling apparatus;

transmitting the fluid information to a remote position via a communication channel between the vehicle sampling apparatus and the remote position; and

disconnecting the vehicle sampling apparatus from the multiphase sampling apparatus.

26. The method of claim 21, which is performed subsea.

27. The method of claim 26, wherein the vehicle is a subsea remotely operated vehicle.

28. The method of claim 23, wherein the sampling probe is insertable into the fluid flowline by an extension mechanism.

29. The method of claim 21, which further comprises analyzing the collected fluid sample by means of a fluid analyzer.

30. The method of claim 21, which further comprises enriching a phase of the collected fluid sample.

31. The method of claim 30, wherein the enrichment of the collected fluid sample may further include separating the phases of the fluid sample, storing the phases of the fluid sample which are of interest and returning the unwanted phases of the fluid sample to the flowline.

32. The method of claim 21, further comprising the step of pressure testing the multiphase sampling apparatus and the vehicle sampling apparatus.

33. The method of claim 21, which further includes the step of pumping unwanted fluid back into the flowline by means of the fluid pump.

34. The method of claim 23, which further includes the step of cleaning the fluid conduits in the system by means of the fluid pump.

35. The method of claim 23, which includes the step of cleaning the sampling probe by means of the fluid pump.

36. A system for collecting fluid samples from a subsea structure, the system comprising:

a subsea sampler device permanently or semi-permanently attached to the subsea structure and equipped with a device for capturing a multiphase sample from the subsea structure; and

a remotely operated vehicle (ROV) sampling skid assembly including an enrichment system for separating water, gas and/or oil into substantially monophasic samples from the multiphase sample, and a device for storing the separated samples on the ROV skid.

37. The system of claim 36, wherein the subsea structure includes one of a fluid flowline, and a wellhead.

38. The system of claim 36, wherein the ROV skid transfers the samples to a surface facility.

39. The system of claim 36, further comprising a device for ensuring that the samples that are taken are representative in terms of composition and conditions, including pressure and temperature, of the phases flowing at the subsea structure.

40. A method for collecting fluid samples from a subsea structure, the method comprising:

permanently or semi-permanently attaching a subsea sampler device to a subsea structure;

capturing a multiphase sample from the subsea structure with the subsea sampler device;

separating water, gas and/or oil into substantially monophasic samples from the multiphase sample by an enrichment system of a remotely operated vehicle (ROV) sampling skid assembly; and

storing the separated samples on the ROV skid.

41. The method of claim 40, wherein the subsea structure includes one of a fluid flowline, and a wellhead.

42. The method of claim 40, further comprising the ROV skid transferring the samples to a surface facility.