WO2012161588A1

WO2012161588A1 - Method and device for filling a submerged sample bottle

Info

Publication number: WO2012161588A1
Application number: PCT/NO2012/050097
Authority: WO
Inventors: Robert James COWMAN; Arve MARTINSEN; Morten EGE
Original assignee: Proserv Norge As
Priority date: 2011-05-26
Filing date: 2012-05-23
Publication date: 2012-11-29

Abstract

Method for filling a submerged sample bottle (2) where the sample bottle (2) during sampling communicates with a sample supply (24) via at least a first valve (22) or a second valve (23), where the method includes: - providing the sample bottle (2) with a piston (16) connected to a piston rod (14) that extends outside the sample bottle (2); - connecting the piston rod (14) to an active part of an actuator (4) while keeping the cylinder housing (8) of the sample bottle (2) and the actuator (4) stationary relatively each other.

Description

METHOD AND DEVICE FOR FILLING A SUBMERGED SAMPLE BOTTLE

There is provided a method for filling a submerged sample bottle. More precisely there is provided a method for filling a submerged sample bottle where the sample bottle during sampling communicates with a sample supply via at least a first valve or a second valve. The invention also includes a device for practicing the method.

The overall objective both with flow measurement and with production sampling is to provide the best possible quality data for reservoir ma nagement and well diagnostic. Fluid properties required for correct metering are best obtained at line conditions. The traditional way of obtaining this information has been to collect samples from surface test separators, while for oil producing reservoir, bottom hole sampling is the preferred method. For the purpose of reservoir management it is very important to monitor the evolution of each individual well during its production time. In a subsea field where several well streams are often commingled into one flow line, there are no traditional methods available to obtain individual well samples.

The sampling technology of production fluid is specially designed to provide the best sample possible, at true pressure conditions, to enable laboratories to perform very accurate and high quality PVT and chemical analysis.

These principles and aims can be valid for sampling of other fluids of any type.

Accurate data and detailed knowledge about the reservoir enables the operator to produce more efficiently now and in the future. For fields that have been in production for more than ten years, the need for accurate data exceeds the access to it by far. This fact represents a problem that is connected to the uncertainty of accuracy in the data currently available or simply the lack of detailed knowledge that one has to support issues with enhanced oil recovery programs.

In certain areas of the globe sampling is required from start up of each individual well by law. It can also be used in conjunction with tracer technology to monitor the performance of new wells as they come on stream, this information gives an invaluable insight into the formation structure and performance. Therefore subsea sampling is a technology which can be used through the entire well's life cycle. There are several benefits to obtaining accurate samples.

• They enhance oil recovery by securing detailed knowledge about each

individual well for content analysis.

• Accurate samples work to maintain lifetime accuracy and value of multiphase measurement systems by providing a source of verification and calibration.

• Allocation and fiscal data points are provided through component analysis of hydrocarbons to determine the quality from each well .

• Gain a lifetime of flow assurance by use of chemical and salinity analysis.

• Optimized subsea processing and the reduction of environmental hazards

through sampling the efficiency of separation and waste water purity.

• Detailed analysis of formation shape and performance when used in

conjunction with tracer technology.

Each of the above mentioned benefits are only possible when the true representation of the flow is captured for lab analysis.

The purpose of the invention is to overcome or reduce at least one of the

disadvantages of the prior art, or at least provide a useful alternative to prior art.

The purpose is achieved according to the invention by the features as disclosed in the description below and in the following patent claims.

There is provided a method for filling a submerged sample bottle where the sample bottle during sampling communicates with a sample supply via at least a first valve or a second valve, where the method includes:

- providing the sample bottle with a piston connected to a piston rod that extends outside the sample bottle;

- connecting the piston rod to an active part of an actuator while keeping the cylinder housing of the sample bottle and the actuator stationary relatively each other.

The method may include, subsequently of opening the first valve, adjusting the speed of the actuator to give a desired sampling flow rate into the sample bottle.

This invention relates to obtaining an individual sample from individual wells. The sampler is designed to sample hydrocarbon, gas and produced water from a live subsea production system with zero emission to the environment. As stated above, fluid samples are required in order to determine fluid chemistry from individual wells and obtain the benefits listed above. The system has the potential for use in other applications, such as, but not limited to injection water, carbon dioxide before injection for carbon capture, for hydraulic control fluids of subsea systems, and chemicals injected and used within the system.

The invention thus relates to a method for filling a sample bottle from the individual well system or from the comingled system, by use of a sampler. Specifically, the procedure is to obtain a sample from a subsea sampling system at well conditions. The sampling system typically includes a sample bottle for storage and handling of samples, a sample piston incl. piston rod used as a syringe for controlling sample motion. The sample cylinder is connected to a sample supply in the form of a well/manifold at a primary end cap side of the sample cylinder. The piston and the secondary end cap are connected to an actuated system, allowing the use of external forces to control the displacement speed of the sample piston i.e. control sa mple timing.

Sample bottles for well fluid are used to a considerable extent for the storage and transportation of such samples, for example, between the well and a laboratory for analysis of the sample to take place. The invention is also covering the sample transfer from the subsea sample system to a laboratory sample cylinder by use of the actuated system whilst keeping well conditions.

Samples of this nature may, as stated above, be either a single- or a multi-phase fluid. While sampling it is important to ensure that the sample is collected in the same phase and pressure as the well pressure and temperature. It is of great importance that the actuated system ensures a steady pressure to prevent pressure drop while sampling of the well, to prevent loss of fluid phases and to prevent hydrates which could lead to difficulties in further handling of the sample.

While sampling from an above hydrostatic well it is also important to avoid an unwanted pressure drop to ensure that one do not lose light end of the produced fluids and reduces the risk of hydrate formation . The pressure drop is controlled by monitoring the back pressure and controlling the sample motion by use of actuators.

While sampling the well pressure may be less than that of the surrounding

environment, sub hydrostatic, the invention allows the sample cylinder piston to act as a syringe there by drawing a sample into the bottle. The motion of the piston can be controlled so that light ends of the sample are not lost and reduces the risk of hydrate formation.

The method may include subsequently of opening the first valve and second valve, keeping the actuator stationary while flushing through the sample bottle.

While sampling using a flow through technique the cylinder will normally be filled with an inhibitor fluid or sampling oil to ensure there are no pressure drops induced upon opening the sampling system to the system to be sampled, it is beneficial to have a reduced volume of the system which has to be flushed. By using a piston bottle the swept volume of the cylinder can be reduced therefore reducing the required inhibitor fluid to be flushed. Once clear of inhibitor fluid the system can use the above principles. Flushing of the cylinder is time consuming exercise therefore costly subsea, also inhibitor fluids are often dangerous to handle therefore reduced volumes increase safety in operations.

Developments in petroleum production have led to a number of subsea wells connecting to subsea installations to subsea manifold on the seabed, which may in turn be connected with other near-horizontal wells.

Representative samples of a single well must thus be extracted at the current well wellhead. There exists designed equipment and procedures for remotely connecting sample bottles to the wellhead. However, it has been shown that the procedure for controlled filling according to prior art is difficult and not very reliable, feasible or safe under certain conditions when the sample bottle is submerged.

The method may be practised by use of a sampler including a submerged sample bottle where the sample bottle is provided with a piston connected to a piston rod that extends outside the sample bottle and where the piston rod is connected to an active part of an actuator while the cylinder housing of the sample bottle and the actuator are stationary relatively each other.

An adjustable sample volume may be present inside the cylinder housing between the primary end cap and the piston.

While sampling with a submerged sampler. The sampler includes a sample bottle for storage and handling of sample, sample piston incl. piston rod used as a syringe for controlling sample motion. The sample cylinder is connected to the well/manifold from the primary end cap side of the sample cylinder. The piston and the secondary end cap is connected to an actuated system, allowing to use external forces to control the displacement speed of the sample piston i.e. control sample timing.

The actuator may be in the form of a hydraulic ram. Other types of actuators can be used, although reliability while using other actuators might decrease.

The sample bottle and two actuators may be positioned in a frame where the piston rod of the sample bottle and the active parts of the actuators are connected to a bracket connection assembly.

To facilitate assembly and disassembly of the sample cylinders, and actuators may be connected to the frame by use of cylinder stack assemblies. This gives a solid self- supported frame. The frame may include lifting lugs for internal lifting, enabling easy handling of the sample frame assembly.

The bracket connection assembly may be connected to at least one guide follower that is moveable on a sliding rod of the frame.

The sample bottle and the actuator may be connected to the sliding rod by at least one cylinder stack assembly.

The frame may, in addition to two sliding rods, include a front end bracket and a rear end bracket.

The front end bracket and the rear end bracket may include stack pins for stacking samplers above each other. The sampler is most advantageously designed to be included in a main assembly of several other sample frame assemblies. The sampler is typically provided with the necessary fluid connections and valves for controlling hydraulic cylinders and connecting stab to the well template or manifold. The sampler is arranged to be lowered to the seabed to land on top of the manifold.

After the connection stub has been connected to the manifold, by use of an ROV or similar. The sample is captured by opening an ROV operating first and second valves allowing for a connection between the sample cylinder and the well. Then the sample system is ready for use. The actual sample is actuated by operating the Hydraulic ROV valves in the operator panel. The sample time used to prevent a pressure drop occurring while sampling is controlled by the ROV. The pressure drop between the well and the sample bottle is kept at an acceptable relatively low level at the rate of flow in fluid connection remains relatively low. Below, an example of a preferred method and device is explained under reference to the enclosed drawings, where:

Fig. 1 shows in perspective and partly sectioned a sampler according to the

invention; and

Fig. 2 shows a principal diagram of the fluid paths of the sampler in fig. 1.

On the drawings the reference number 1 denotes a sampler including a sample bottle 2 and two actuators 4 that are positioned in a frame 6.

The sample bottle 2 has a cylinder housing 8 with a sealable attached primary end cap 10 and a sealable attached secondary end cap 12. A piston rod 14 is extending from a piston 16 inside the cylinder housing 8 through the secondary end cap 12.

An adjustable sample volume 18 is thus present inside the cylinder housing 8 between the primary end cap 10 and the piston 16. The secondary end cap 12 has drain filters 20 for draining the opposite end of the sample bottle 2.

The sample volume 18 is communicating with a first valve 22 only in the case of a drawn sample and second valve 23 in the case of a flow through sample that are connectable to a sample supply 24 shown on fig. 2, typically in the form of a subsea wellhead. The valves 22, 23 are connected to the sample supply 24 via individual sample tubular 25. For a flow through sample a flow restriction 27 is positioned in the sample supply 24 between connection points for the sample tubular 25.

The frame 6 includes in this preferred embodiment two para llel sliding rods 26 that are fixed to a front end bracket 28 at their front end party and to a rear end bracket 30 at their opposite end party.

A bracket connection assembly 32 extends between sliding guide followers 34 that are axially movable along the sliding rods 26.

The sample bottle 2 and the actuators 4, here in the form of hydraulic rams, spans between the front end bracket 28 and the bracket connection assembly 32 where the piston rod 14 of the sample bottle 2 as well as piston rods 36 of the actuators 4 are fixed by use of a spindle 38.

The sample bottle 2 that is positioned between the two actuators 4, and the actuators 4 are also fixed to the sliding rods 26 by two cylinder stack assemblies 40. The actuators 4 are connected to a hydraulic primary port, not shown, by a primary pipe 42 and to a hydraulic secondary port, not shown, by a secondary pipe 44, see fig. 2.

The frame 6 is provided with stack pins 46 and stack apertures 48 for stacking samplers 1 above each other.

When collecting a sample from a subsea sample supply 24, a Remote Operated Vehicle (ROV) not shown, is utilized. The general operation of an ROV is well known to a person skilled in the art and is not explained here.

After the sampler 1 is position at its desired subsea position, the first valve 22 is connected to the sample supply 24 by a sample tubular 25, se fig. 2, while care is taken to avoid spillage to the surroundings.

Then the primary and secondary pipes 42, 44 are connected. Subsequently of opening the first valve 22 for communication between the adjustable sample volume 18 and the sample supply 24. Hydraulic fluid flow is adjusted in the pipes 42, 44 to give a desired speed of the actuators 4 that are moving the bracket connecting assembly 32 with the sliding guide followers 34 along the sliding rods 26, thus also moving the piston 16 of the sample bottle 2 at the same speed . The speed is controlled to give the best possible sample conditions as explained in the general part of the document.

When the sample bottle 2 has received the desired amount of sample fluid, the first valve 22 is closed. The sample tubular 25 and the pipes 42, 44 are disconnected and the sampler 1 brought to the surface and further on to a place of analysis of the fluid sample.

If a flow through mode of sampling is utilized, both the first valve 22 and the second valve 23 are opened. While the piston 16 is kept stationary, fluid are, due to the flow restriction 27 flowing from the sample supply 24 and into the sample volume 18 through one of the valves 22, 23. A return flow is flowing from the sample volume 18 and to the sample supply 24 through the other of the valves 22, 23.

When a sample is received the valves 22, 23 are closed and the sampler 1 retrieved as described above.

Claims

C l a i m s

1. Method for filling a submerged sample bottle (2) where the sample bottle (2) during sampling communicates with a sample supply (24) via at least a first valve (22) or a second valve (23), c h a r a c t e r i z e d i n that the method includes:

- providing the sample bottle (2) with a piston (16) connected to a piston rod (14) that extends outside the sample bottle (2);

- connecting the piston rod (14) to an active part of an actuator (4) while keeping the cylinder housing (8) of the sample bottle (2) and the actuator (4) stationary relatively each other.

2. Method according to claim 1, c h a r a c t e r i z e d i n that the method includes subsequently of opening the first valve (22), adjusting the speed of the actuator (4) to give a desired sampling flow rate into the sample bottle (2).

3. Method according to claim 1, c h a r a c t e r i z e d i n that the method includes subsequently of opening the first valve (22) and second valve (23), keeping the actuator (4) stationary while flushing through the sample bottle (2).

4. A sampler (1) including a submerged sample bottle (2),

c h a r a c t e r i z e d i n that the sample bottle (2) is provided with a piston (16) connected to a piston rod (14) that extends outside the sample bottle (2) and where the piston rod (14) is connected to an active part of an actuator (4) while the cylinder housing (8) of the sample bottle (2) and the actuator (4) are stationary relatively each other.

5. A sampler (1) according to claim 4, c h a r a c t e r i z e d i n that an adjustable sample volume (18) is present inside the cylinder housing (8) between the primary end cap (10) and the piston (16).

6. A sampler (1) according to claim 4, c h a r a c t e r i z e d i n that the actuator (4) is in the form of a hydraulic ram.

7. A sampler (1) according to claim 4, c h a r a c t e r i z e d i n that the sample bottle (2) and two actuators (4) are positioned in a frame (6) and where the piston rod (14) of the sample bottle (2) and the active parts of the actuators (4) are connected to a bracket connection assembly (32).

8. A sampler (1) according to claim 7, c h a r a c t e r i z e d i n that the bracket connection assembly (32) is connected to at least one guide follower (34) that is moveable on a sliding rod (26) of the frame (6).

9. A sampler (1) according to claim 8, c h a r a c t e r i z e d i n that the sample bottle (2) and the actuator (4) are connected to the sliding rod (26) by at least one cylinder stack assembly (40).

10. A sampler (1) according to claim 8, c h a r a c t e r i z e d i n that the frame (6) in addition to two sliding rods (26) includes a front end bracket (28) and a rear end bracket (30).

11. A sampler (1) according to claim 10, c h a r a c t e r i z e d i n that the front end bracket (28) and the rear end bracket (30) include stack pins (46).