WO2016110462A1

WO2016110462A1 - An apparatus for measuring surface interaction with a sample under pressure

Info

Publication number: WO2016110462A1
Application number: PCT/EP2016/050020
Authority: WO
Inventors: Peter Hans Ove SVENSSON; Per Fredrik PETTERSSON
Original assignee: Biolin Scientific Ab
Priority date: 2015-01-06
Filing date: 2016-01-04
Publication date: 2016-07-14

Abstract

An apparatus for measuring surface interaction with a sample under pressure, the apparatus comprising a vessel and a sensor arranged in the vessel. To enable measurements at high pressure without affecting the measurements or destroying the sensor, the vessel holds a fluid at a pressure p, and the sensor is provided with opposite first and second surfaces, where the first surface interacts with the sample and both the first and second surfaces are exposed at least to the pressure p.

Description

AN APPARATUS FOR MEASURING SURFACE INTERACTION WITH A SAMPLE UNDER PRESSURE

INTRODUCTION

The present invention relates to an apparatus for measuring surface interaction with a sample under pressure.

In some applications, surface interaction measurement under high pressure condition is desired. As an example, there could be a need to mimic

environmental conditions in for example oil reservoirs and in the pipelines upstream of the reservoirs, in chemical reactors, in turbines, and/or in nuclear power plants etc.

The measuring of surface interaction, or dimensional measuring, may relate e.g. to detection of properties of a chemical composition, properties of an electron structure or a crystalline structure, or an optical property. The surface

interaction may also relate to surfaces adsorption or desorption, e.g. adsorption or desorption of molecules on a surface, e.g . adsorbed layers, over-layers on single crystals, and surface films. The mass in question can be in liquid or gas phase. Mass detection can be based e.g . on mechanical, acoustical or optical principles.

In atmospheric pressure, the listed principles are normally uncomplicated, and numerous standard tools exist already.

A problem may arise when measurements are carried out under high pressure conditions, and particularly when using liquid phase samples having electrical conductivity.

QCM, or more specifically QCM-D (Quartz Crystal Microbalance with Dissipation), taken as an example, is used to measure surface interactions in gas or liquid phase. The vast majority of all QCM-D measurements are done in liquid phase using liquids with certain conductivity. Measurements are in general done at atmospheric pressure. In QCM-D, a quartz crystal interacts with the fluid sample. An electrode carries an electrical signal which drives oscillation of the crystal.

Typically, the sensor is mounted in a holder forming a sealed measurement cell. The holder forms an inlet connected to a sample bottle via a hose. The outlet is connected to a pump which aspires the liquid from the cell to a waste bottle.

In this setup, only the first surface of the sensor crystal is in contact with the liquid. The second side of the sensor crystal is exposed to atmosphere.

A problem is that a pressure difference over the crystal creates stress in the crystal . The crystal is typically brittle and may crack under large pressure differences and the differential pressure may create a response in the crystal and therefore disturb the signal intended for the measurement and caused by the sample.

There is a need for a technical solution enabling measurements such as QCM measurements in high pressure. There is a further need for a solution enabling use of conductive liquids under continuous liquid flow conditions.

There are solutions available supporting QCM measurements in gas phase where the measurement cell is encapsulated into a High pressure vessel . In this case both sides of the sensor are exposed to the same pressure, i.e. there is no pressure difference between the two sides. This setup can in principle be used also in liquid phase as well, where the sensor is immersed in liquid . However, this will be restricted to be used only in non-conductive liquids. If not, the liquid could short-circuit the electrodes which drive the sensor crystal and potentially form a parallel impedance disturbing the sensor signal .

SUMMARY OF THE INVENTION It is an object of embodiments of the invention to provide an apparatus which can perform measurements in high pressure conditions with electrically conductive samples, particularly with liquid samples. According to this and other objectives, the present invention provides an apparatus for measuring surface interaction with a sample under pressure.

The apparatus according to the invention comprises a vessel forming an internal space containing a sensor, a non-conductive media, and the sample. The sensor has opposite first and second surfaces where the first surface is in contact with the sample and thereby contributes in measuring the surface interaction therewith. The second surface is in contact with the non-conductive media and forms wiring spots where electrodes are connected to the sensor. The wiring spots are thus protected from the sample by the non-conductive media . The internal space holds a pressure, p, acting on the first surface through the sample and acting on the second surfaces through the non-conductive media.

Since the pressure, p, acts on both sides of the sensor deflection of the sensor due to a pressure difference is prevented. Accordingly, the apparatus can be used for measuring surface interaction under high pressure conditions. Such measurements may be carried out by increasing the pressure p, and depending on the selection of the pressure p, the pressure of the sample itself may have minor or no influence on the surface.

Since the wiring spots are separated from the sample by the non conductive media, the impact of the sample on the electrical conductivity can be prevented, and high pressure conditions can be mimicked with samples of any kind without causing short circuiting or otherwise influencing the measurement due to electrical conductivity and/or pressure.

The sample could particularly be a liquid sample, e.g . an electrically conductive or non-conductive sample. It could, however, also be in gas phase, again conductive or non-conductive. It could be a dispersion of solid particles, emulsions with mixed liquids, liquid/membrane mixes such as lipid vesicles, or particles carried by a gas stream, or other mixed - phase systems. The apparatus could e.g . be applied for simulating chemical reactors, pipelines and containers, oil and gas reservoirs, drill-holes, pipelines, containers and processes or for material studies under high pressures.

The vessel particularly forms a complete encapsulation of the holder such that the entire outer surface or at least the majority of the outer surface of the sensor therefore becomes exposed to the pressure inside the vessel .

The vessel holds a non-conductive media, e.g . a non conductive gas or liquid. Due to the pressure, p, in the internal space, the non-conductive media is held at a pressure p. This pressure may be selected based on the need to mimic certain pressure conditions during the surface interaction measurement. Since the pressure acts on both surfaces, the sensor is not deflected by the pressure.

In use, the apparatus may be selected e.g . for measuring surface interaction with a hydrocarbon or similar organic compound under a pressure corresponding to a typical pressure in an oil reservoir. In this case, the pressure in the vessel is raised to that typical pressure, and the hydrocarbon sample is added to the apparatus for interaction with the first surface of the sensor. Since both surfaces of the sensor are subjected to the high pressure, with the only pressure difference possibly being caused by the presence of the sample on the first surface, deformation of the sensor or pressure induced distortion of the sensor signal is essentially eliminated.

The non-conductive media could generally be any kind of non-conducting media in gas or liquid phase. The non-conductive properties of the media prevent short-circuiting of electrical circuits of the holder and sensor.

Herein we refer to non-conductive meaning having such a poor conductivity that we can consider the fluid being an insulator preventing short-circuiting of electrical components separated by the media, e.g. between electrodes attached to the sensor. Different kinds of media, including natural gas and other hydrocarbon mixes, carbon dioxide, compressed air, nitrogen, inert noble gasses, and gaseous (synthesis) reagents could be used. The sensor could particularly be a piezoelectric sensor, e.g. a piezoelectric acoustic sensor in which waves are utilised for sensing a physical phenomenon such as adsorption or desorption of molecules on a surface. In this kind of sensor, an electrical signal is converted to vibration to create a mechanical wave which is influenced by the adsorption or other physical phenomenon.

The sensor could, as an example, be a quartz crystal microbalance unit (QCM) or a QCM-D unit.

The apparatus may be used in flow mode with a flow of the sample or in stagnant mode, i.e. the sample is provided until the first surface is covered with sample and subsequently, the flow is stopped .

The sample and the non-conductive media may meet in an interface which equalizes the pressures of the sample and the non-conductive media. By meet is considered that the sample and the non-conductive media interact such that the pressure equalises or essentially equalises. The pressure of the non-conductive media will preferably be in the range of 95-105 pet. of the pressure of the sample. As an example, the pressure of the sample may be 100 bar, and the pressure of the non-conductive media between 95 and 105 bar.

The interface may particularly be configured to prevent mixing of the sample and the non-conductive media . This can be done in different ways, e.g . by use of gravity and different density of the sample and non-conductive media, or by gravity combined with other properties of the sample and the non-conductive media, .e.g. properties making the non-conductive media immiscible in the sample, vice versa .

If the sample and the non-conductive media are in direct contact with each other, the above mentioned property differences between the sample and the non-conductive media may prevent the mixing . Accordingly, the apparatus according to the invention may include a non-conductive media and a sample, where the properties prevent mixing, particularly different density and/or polarity. In one embodiment, the interface comprises a separation element which prevents direct contact between the sample and the non-conductive media. In this case, the above mentioned different properties of the sample and the non-conductive media are not needed. However, the separation element may be combined with different properties.

The separation element could be a membrane, a floating piston, a mercury bridge, a filter, a semipermeable membrane, or an ion trap.

In one embodiment, the interface is a structure forming a no flow condition at a distance from the first and second surfaces. An example of such a structure is a long thin tube connecting a space for the non-conductive media from another space for the sample, i.e. the internal space is separated in two compartments by the long thin tube.

The interface may form a flushing structure configured to establish a protective flow of non-conductive media over the second surface, to thereby separate the wiring spots from the sample by the non conductive media .

The first and second surfaces may both be in fluid communication with a waste space which thereby forms part of the internal space. The waste space may be configured for collection of the sample. In one embodiment, the sample flows from a sample supply inlet across the first surface and further into the waste space. In one embodiment, the sample inlet is above, e.g. vertically above, the first surface and the first surface is again above the waste space such that the sample can flow by gravity from the inlet to the waste space.

Two separate inlets into the internal space may be provided . One inlet could be configured for introducing the sample into the internal space, i.e. it may form the above mentioned supply inlet. The other may be configured for introducing the non-conductive media supply into the internal space. A pump or other pressure supplying structure may pressurize the internal space, e.g. via one or both of the two inlets. The pressure may e.g. be for mimicking pressure conditions of a well etc.

The first surface may form an inner surface of a flow-cell in the holder. The flow- cell could thereby be configured to provide a flow of the sample across the first surface. The flow-cell could receive the sample from a container which could contain an amount of the sample inside the vessel, and to expose the first surface at least to the pressure p, the container could form the first opening between the internal space and the first surface. In that way, the pressure p in the internal space acts on the surface of the sample which is in the container and thus acts on the first surface of the sensor.

The second opening formed by the holder enables the pressure, p, in the internal space to act also on the second side of the sensor, i.e. on the first surface via a pressure applied to the surface of the sample in the container, and on the second surface via pressure propagation through the second opening. Since both sides are subjected at least to the pressure p, deformation, destruction and potential misreading from the sensor can be avoided.

The second opening could particularly be arranged on an opposite side of the sensor, or at least form a passage leading to an opposite side of the sensor. The pressure, p, in the vessel can thereby act on both sides of the sensor.

The second surface of the sensor may e.g . form wiring spots where electrodes are attached to the sensor, and the flow-cell may particularly be separated from the wiring spots. By the combination between the pressurised non-conductive gas at the pressure p filling the vessel, and a possibly conductive sample, e.g. a liquid sample, flowing in a flow-cell which is separated from the second surface where the wiring spots are located, the apparatus may utilise conductive samples at a high pressure without damaging the sensor, without complicating signal interpretation and without short-circuiting the electrodes which carries the signal which drives the vibration of the sensor. Particularly for a sensitive crystal sensor such as a QCM or QCM-D sensor, this protects against high pressures and enables operation with liquid and conductive samples.

The first opening may point in an upwards direction relative to gravity, and the sample may be guided from the container in an at least partly downwards passage into a flow-cell to enable transport of the sample by gravity. In the flow-cell, the sample may flow along the first surface of the crystal until it leaves the flow-cell through one or more drain openings forming or communication with the sample outlets in the holder.

The container could be configured to receive the sample via the first opening from an inlet into the internal space, again preferably by use of gravity. The inlet into the internal space forms a passage across a wall of the vessel and it may include a flow control structure e.g. including a valve and/or a flow pump for the sample.

The flow-cell may be configured to deliver the sample to an outlet out of the internal space, i.e. the outlet forms a passage across a wall of the vessel. To control the flow of the sample through the flow-cell, the outlet may be

configured to manipulate the flow which herein means e.g . to manipulate flow speed, to start and/or stop the flow of the sample, and/or to change the type of sample. The flow could be controlled by pressurisation means for pressurising the outlet with a counter pressure, or it could be controlled e.g. by use of a hydrostatic valve, by use of controlled flow pumps, or by other means for controlling the flow of the sample at the outlet.

It is desirable to have an essentially equal pressure on the first and second surfaces. For that reason, it is desirable to reduce the pressure contribution of the sample onto the first surface. This may be done by designing the flow-cell and container such that the gravity force from sample onto the first surface becomes low. In one embodiment, this is done by having a low dimension of the container and/or of the passage between the container and the flow-cell in the direction of gravity. In one embodiment, the container has a shape whereby a body formed by the sample inside the container has a largest dimension in the direction of gravity being less than half the largest dimension perpendicular to gravity.

E.g . to mimic conditions in an oil well etc., the apparatus may comprise a temperature control structure for changing the temperature in the internal space and/or for changing the temperature in the flow-cell and/or for changing the temperature in the container. The temperature control structure may include a resistance heating element or any other kind of heating means, e.g. integrated in the holder. The temperature control structure may be configured for raising the temperature of the sample and/or of the non-conductive gas to a

temperature above 150 °C or even above 200 °C.

The apparatus may comprise a sample supply, e.g . comprising a controllable pressure pump and configured to provide the sample to the vessel at a pressure p+Ap being higher than p. By adjusting p+Ap, the amount of the sample which enters the vessel can be controlled . To prevent increasing the pressure inside the vessel, the pressure Ap is preferably low, e.g . less than 0.5 bar or even less than 0.1 bar. The pressure p could be very high, e.g . higher than 1000 bar, or even higher than 1500 bar which is a typical pressure in oil wells.

In a second aspect, the invention provides a method of analysing an electrically conductive sample under a pressure p, by use of an apparatus according to the first aspect of the invention . The method according to the second aspect comprises the step of providing a pressure p in the vessel, injecting the sample under an increased pressure p+Ap through the inlet, passing the sample through the flow path, controlling rejection of the sample at the outlet, and analysing a signal from the sensor.

The pressure, p, may e.g . be obtained by pressurising a non-conductive media, and the sample could be a conductive fluid . Particularly, a pressure above 1000 bar e.g . in combination with heating to a temperature to above 150 °C could be carried out e.g . to mimic an oil well . The method could be used for various purposes, e.g . for simulating chemical reactors, pipelines and containers, oil and gas reservoirs, drill-holes, pipelines, containers and processes or for material studies in high pressures.

BRIEF DESCRIPTION OF THE DRAWINGS

Embodiments of the invention will now be further described with reference to the drawings, in which : Fig. 1 illustrates an apparatus according to the invention;

Figs. 2-4 illustrate different alternative embodiments of an apparatus according to the invention; and

Figs. 5-8 illustrate further embodiments. DETAILED DESCRIPTION OF EMBODIMENTS

It should be understood that the detailed description and specific examples, while indicating embodiments of the invention, are given by way of illustration only, since various changes and modifications within the spirit and scope of the invention will become apparent to those skilled in the art from this detailed description .

In Fig. 1, the apparatus 1 comprises a vessel 2 which forms an internal space 3 containing a non-conductive media at a pressure p. Inside the internal space 3, the vessel contains a holder 4 which holds a sensor, in this embodiment, the sensor is a crystal 5 but the sensor could also be non-crystalline. The sensor is configured to measure surface interaction with a sample 6.

The sensor could be a QCM or a QCM-D sensor with a crystal having a first surface 7 and a second surface 8.

The first surface is configured for the interaction with the sample. The holder forms a first opening 9 between the internal space 3 and the first surface 7 and a second opening 10 defined between the edges 11. The second opening opens a passage between the internal space 3 and the second surface 8. Due to the two openings, the pressure p in the internal space propagates to both sides of the crystal and high pressure conditions can be simulated without jeopardizing the quality of the measurements and without destroying the brittle crystal . The first surface 7 forms an inner surface of a flow-cell 12 inside the holder. The flow-cell receives the sample from a container 13, and the first opening 9 opens into the container. The container can hold an amount of the sample inside the vessel, and the sample is guided from the container to the flow-cell by the passage 14. In the illustrated embodiment, the apparatus is designed for the indicated orientation relative to gravity indicated herein by the arrow G. In this orientation, the sample can be guided from the sample container 15 by the sample supply and the sample pump 16 to the inlet 17 which forms a passage across the wall 18 of the vessel . Alternatively, the sample is received from a storage contained inside the vessel and not received through an inlet.

Inside the vessel, the sample is driven by a pressure gradient created by a pump, by gravity, by a regulator or by other means. The sample is guided through the first opening 9 into the container 13. Again, by use of gravity, the sample is transported through the passage 14 into the flow-cell 12 and further out of the flow-cell via the rejection ports 18, 19 to the outlet 20. The outlet 20 forms a passage across the wall 21 of the vessel. The outlet comprises a hydrostatic valve 22 configured to control flow speed of the sample or to stop and start the flow of the sample through the flow-cell . The apparatus further comprises a control unit (not illustrate). The control unit communicates with the valve 22 and with the pump 16 to coordinate input and output of the sample from the container and to create a balance there between. To help equalizing temperatures and pressure after introducing sample, the sample may be introduced batch wise and in each batch flow continuously at a lower flow-speed . The less need for coordination and balancing of the flow, the more robust is the apparatus.

The second surface 8 forms wiring spots for electrodes 23, 24 which are attached for driving oscillation of the crystal . The electrodes are protected against short-circuiting by the non-conductive properties of the media in the internal space. The wiring spots are separated from the flow-cell by the crystal and the sealing O-ring structure 25.

The resistive heater 26 provides temperature control in the internal space. It is configured to raise the temperature to more than 150 °C. In one embodiment, the heater is attached to the holder 2 and in some embodiments, the heater is not resistive but rather based on other principles of heating. EXAMPLES

The stability of heavy crude-oil components and the risk of precipitation and adsorption to surfaces are very important aspects both in recovery of oil from oil-wells and for pipeline transport. But also, flocculation can be desired for example to extract the crude oil from extraction or transport solutions, or to purify process water. Since crude oil in itself and the solutions of it are complex systems, it is hard to design experiments and ensure relevant results in normal lab conditions, and therefore experiments would benefit from using as close-to real-world conditions as possible. This requires simulating conditions in an oil well or pipeline, including high temperatures and pressures.

EXAMPLE 1

Fig. 2 illustrates an example of pressure vessel setup with pressure access to both sensor sides 27, 28 and where the sensor is mounted in a horizontal mounting position relative to the direction of gravity. Gravity is indicated by the arrow G. The pressure vessel comprises a pressure port 29. This enables attachment of the vessel to a source of pressurised non-conductive media . The pressure port is in the bottom of the vessel. The non-conductive media is provided at a pressure p. The liquid port 30 forms an inlet across a wall of the vessel in the top of the vessel and thereby provides sample access. Not shown in Fig. 2 are electrical connections for sensor, temperature sensors or temperature control actuators.

In Fig. 2, a piezoelectric sensor with low and linear temperature sensitivity (for instance GaP04) is used. The sensor is coated on the first side with relevant pipeline materials such as steel or iron oxide. The sensor is mounted horizontally in a holder 31 with electrode access from the lower, second, side, and the first side facing upwards and sealed with a ring-shaped gasket but otherwise open for direct access of both pressure and liquid. A liquid handling pipette connected to a high pressure syringe is placed in such a way that liquid can be pipetted directly to the sensor surface. It is placed close enough to the surface to be used also to aspirate liquid from the sensor surface.

In this setup, the system and sensor is first stabilized at desired temperature and pressure, typically but not limited to 150-400°C temperature and 200-400 Bar pressure. Next the sample is introduced and the measurement started . Next either temperature or pressure, or both are changed in a controlled

predetermined way to study in which regions the heavy crude oil components start interacting with the surface, and how surfactants and solvent composition can affect that interaction starting point. After each experiment, the sample can be removed from the sensor surface, where after the sensor can be reconditioned through washing, still under pressure and temperature control .

EXAMPLE 2

Fig. 3 illustrates a pressure vessel setup with the sensor 32 placed in a vertical flow-cell configuration. The orientation could have been different, e.g.

horizontal.

The second side of the sensor is open to the vessel pressure, and the first side is exposed to the vessel pressure plus the hydrostatic pressure of the liquid in the sample container plus flow system, here typically 20- 30 mm corresponding to approximately 0.2-0.3 kP pressure with water. The pressure vessel is shown with a top port for high-pressure syringe driven injection of liquid sample and two bottom ports: a flow-cell outlet to a waste vessel, and a port for vessel pressurization through media injection. The waste vessel is pressurized via a differential regulator to a pressure 0-20 kPa lower than the vessel pressure. Flow-cell outlet is controlled through a needle valve and is switched on/off through a 2/2 valve. Not shown in the figure are : pressure vessel ports for electrical signals, electrical wiring, temperature sensors or temperature actuators, and sensors to control sample container volume. The sensor is a quartz crystal QCM sensor with an active sensor surface consisting of a material relevant for conditions inside an oil-well, such as different minerals with or without petroleum content. The sensor is used in a vertical flow-cell to avoid problems with different liquid densities floating on each other. The flow-cell has a distance from the sensor surface of 0.1-1.0mm in this example, facilitating good mass transport to the surface through convection and diffusion. The distance could be different.

A typical experiment performed in this setup could comprise:

1) Pressurize and temper the system to desired conditions and let the sensor signal stabilize. Typically 100-400°C and 400-1500 Bar, but not excluding other temperature/pressure conditions.

2) Flow a conditioning sample that could consist of buffer such as saline solution or (diluted) petroleum to saturate the surface. A preconditioning measurement can take place to verify this experiment phase. 3) Measurement starts with the process of flowing a neutral sample liquid buffer such as brine/seawater corresponding to pressurizing the oil well under constant flow.

4) An extraction solution containing the same buffer with additions of a mix of solvent(s) and/or surfactant(s). The measurement would continue and record mass loss from the sensor surface due to petroleum extraction.

5) The buffer again, to represent a transport phase transporting the extracted petroleum .

6) Possible repetitions with same or other extraction mixes. EXAMPLE 3 This sample is the same as example 2 in terms of purpose and experiment sequence, but with another flow control solution. Fig. 4 illustrates a waste container 39 located inside the pressure vessel . The flow-cell outlet is connected to a waste tube bent upwards and then downwards with the rejection port 18 at a level above the flow-cell level and below the top level of the sample container 13. Only two through holes (except electrical and thermal connectors) are for vessel pressurization (bottom left, no 29) and to introduce sample (middle top, no 30).

The difference is that by having the waste container inside the pressure vessel, the pressure control and fluid piping can be simplified . The flow will be driven by a pressure difference generated by the liquid column height or by a hydrostatic pressure between the liquid level in the internal sample container and the waste tube outlet. When the system is in equilibrium, the sensor is kept exposed to liquid but without a flow. Accordingly, both liquid levels will equalize, and the sensor is kept under liquid but at zero flow.

When liquid is pumped into the sample container by the external syringe, the liquid level in the container will rise, thus creating a pressure difference over the flow path. The level will keep rising until the flow created by that pressure difference is equal to the inlet flow, and thus after a brief transition time, the flow speed will be determined by the inlet flow speed. With a flow-cell of height 240 prn above the sensor, and 0.8 mm inner diameter tubing, the flow-cell will completely dominate the flow resistance, and with water at room temperature it will allow flow of several hundred μΙ/min, calculated on a 5 mm height difference between sample container top and waste tube outlet.

In Fig. 5 illustrates an embodiment 33 of the apparatus for measuring surface interaction with a sample under pressure. The apparatus disclosed in Fig . 5 comprises essentially the same components and works essentially in the same way as the apparatus in Fig. 1. Accordingly, reference is made to the embodiment of Fig . 1 for details not shown in Fig. 5.

The apparatus in Fig . 5 comprises a vessel corresponding essentially to the vessel 2 in Fig . 1. The vessel forms an internal space 3 containing a sensor which could be similar to the crystal 5 in Fig. 1. The sensor has opposite first and second surfaces 7, 8 (c.f. Fig. 1), where the first surface is in contact with the sample and the second surface forms wiring spots where electrodes are connected to the sensor.

The wiring spots are protected from the sample by the non-conductive media. In this embodiment, the space in the vessel is separated into a first

compartment and a second compartment with the sensor between the

compartments. The first surface forms a surface of the first compartment and the second surface forms a surface in the second compartment, and the connectors 43 extend out of the second compartment through a pressure tight penetration of the wall of the vessel . In Fig . 5, the two electrodes 23, 24 shown in Fig . 1 are shown simplified as one single connector 43. The connector 43, however, has the same function as the electrodes 23 and 24 in Fig 1.

The sample is supplied from the sample supply 16 and the non-conductive media is supplied from the media supply, e.g. by use of the optional pump 36. The pump supplies the media at a predetermined, and optionally controllable, pressure. Both pumps supply a constant flow, and the pressure is adjusted by the by the pressure regulator 42.

The sample supply forms a first pressure piston 37 and a second pressure piston 38 capable of supplying the sample at a predetermined, and optionally controllable, pressure. Sample could for instance be introduced by sample floating piston cylinders 37, where any number of cylinders can be used fulfilling experiment requirements, here illustrated by two cylinders containing different samples.

In use, the sample flows along the first surface of the sensor 34 and the non- conductive media flows along the second surface of the sensor 34. Both the sample and the media continue into the waste container 39. The function of the waste container 39 is similar to the function of the internal space 3 in Fig 1 - the only difference is that it is formed by a separate vessel.

The waste container is connected to, or forms part of the vessel 33. In the illustrated embodiment, the waste container is connected by first and second conduits 40, 41. These conduits provide pressure tight connection between the waste container and the space in the vessel. The waste container itself is also pressure tight. The waste container forms an interface which equalizes the pressures of the sample and the non-conductive media. The waste container interface forms a no flow condition at a distance from the first and second surfaces, i.e. the liquids are prevented from flowing backwards in the system and the sample is therefore unable to reach the second surface of the sensor.

The common pressure, p, of the non-conductive media and of the sample is adjustable by the pressure regulator 42. This regulator is also illustrated in Fig 1.

Due to the common pressure p for the sample and the non-conductive media, both sides of the sensor are supported by a pressure, and high pressure conditions can be simulated without deflecting or destroying the sensor. Fig. 6 illustrates an embodiment of the apparatus 44. The apparatus comprises a vessel 45 corresponding essentially to the vessel 2 in Fig. 1. The sensor herein could be similar to the crystal 5 in Fig. 1. The apparatus further comprises a sample supply pump 16 which is a constant flow pump similar to the pumps of the previously disclosed embodiments. The supply containers 48 have the same function as the piston cylinders 37 in Fig. 5.

The apparatus further comprises a waste container 49, a manually operable valve 50 for feeding the non-conductive media into the space in the vessel, a sub-system 51filled with non-conductive medium, and a pressure regulating pump 52, again being a constant flow pump similar to the pumps 16, 35, 47 described previously.

Additionally, the apparatus comprises an interface component 53 in the form of a long narrow tube with no flow conditions. The no flow condition is induced by valve 50 being closed. Since there is no flow, mixing can only occur through diffusion, and timescale for diffusion mixing to occur is dependent on tubing length. Accordingly, the non-conductive media and the sample can equalize the pressures via the interface without mixing .

Figs. 7-8 illustrate two embodiments of apparatuses where the interface comprises a separation element which prevents direct contact between the sample and the non-conductive media.

In Fig. 7, the separation element of the apparatus 54 is a diaphragm or membrane 55 arranged in the container 49 to thereby separate a first chamber 56 from a second chamber 57 in the container 49. The flexibility of the membrane 55 enables pressure exchange between the sample in the chamber 56 and the non-conductive media in the chamber 57. Generally, the separation element could be a membrane, a floating piston, a mercury bridge, a filter, a semipermeable membrane, or an ion trap etc.

In Fig. 8, the separation element of the apparatus 58 is a floating piston 59 arranged in the waste container 49 to thereby separate a first chamber 60 from a second chamber 61 in the waste container. The movability of the piston 59 enables pressure exchange between the sample in the chamber 60 and the non- conductive media in the chamber 61.

NUMBERED ALTERNATIVE EMBODIMENTS

1. An apparatus (1) for measuring surface interaction with a sample under pressure, the apparatus comprising a vessel (1) forming an internal space (3) containing a non-conductive gas at a pressure p and a holder (4, 31) with a sensor (5, 32), the sensor having opposite first and second surfaces (7, 8, 27, 28), the first surface being configured for the interaction with the sample, wherein the holder forms a first opening (9) between the internal space and the first surface and a second opening between the internal space and the second surface to thereby expose both the first and second surfaces at least to the pressure p.

2. An apparatus according to embodiment 1, where the sensor is a piezoelectric sensor. 3. An apparatus according to embodiment 2, where the sensor is a piezoelectric microbalance sensor.

4. An apparatus according to any of the preceding embodiments, where the first surface forms an inner surface of a flow-cell in the holder, the flow-cell being configured to receive the sample from a container which forms the first opening between the internal space and the first surface.

5. An apparatus according to any of the preceding embodiments, where the second surface forms wiring spots where electrodes are connected to the sensor.

6. An apparatus according to embodiments 5 and 6, where the wiring spots are separated from the flow-cell .

7. An apparatus according to any of embodiments 4-6, where the container is configured to receive the sample via the first opening from an inlet forming a passage across a wall of the vessel into the internal space.

8. An apparatus according to embodiment 7, where the first opening points in an upwards direction relative to gravity, and the holder forms a sample guiding path extending least partly downwards relative to gravity into the flow-cell to enable transport of the sample from the inlet to the flow-cell by gravity.

9. An apparatus according to any of embodiments 4-8, where the flow-cell is configured to deliver the sample to an outlet out of the internal space. 10. An apparatus according to embodiment 9, where the outlet is configured to manipulate the flow of the sample.

11. An apparatus according to any of embodiments 4-10, where the flow-cell has a shape whereby the pressure created by the sample in the container on the first surface is reduced to a minimum . 12. An apparatus according to any of the preceding embodiments, comprising a temperature control structure for changing the temperature in the internal space.

13. An apparatus according to any of the preceding embodiments, where the non-conductive gas is an inactive gas.

14. An apparatus according to any of the preceding embodiments, where the non-conductive gas is selected from the group consisting of: natural gas, hydrocarbon mixes, carbon dioxide, compressed air, nitrogen, inert noble gasses, and gaseous reagents. 15. An apparatus according to any of the preceding embodiments, comprising a sample supply configured to provide the sample to the vessel at a pressure p+Ap being higher than p.

16. An apparatus according to embodiment 15, where \p is less than 0.5 bar.

17. An apparatus according to any of the preceding embodiments, where the pressure p is higher than 1000 bar.

18. A method of analysing an electrically conductive sample under a pressure p, by use of an apparatus according to any of embodiments 1-17, the method comprising providing a pressure p in the vessel, injecting the sample under an increased pressure ρ+Δρ through the inlet, passing the sample through the flow path, controlling rejection of the sample at the outlet, and analysing a signal from the sensor.

19. A method according to embodiment 18, where the pressure p is obtained by pressurising a non-conductive gas.

20. A method according to embodiment 18 or 19, where the sample is a conductive fluid . 21. A method according to embodiment 18-20, applied for simulating chemical reactors, pipelines and containers, oil and gas reservoirs, drill-holes, pipelines, containers and processes or for material studies in high pressures.

Claims

1. An apparatus (1) for measuring surface interaction with a sample under pressure, the apparatus comprising a vessel (1) forming an internal space (3) containing a sensor (5, 32), a non-conductive media, and the sample, the sensor having opposite first and second surfaces (7, 8, 27, 28), the first surface being in contact with the sample and the second surface forming wiring spots where electrodes are connected to the sensor, wherein the wiring spots are protected from the sample by the non-conductive media and wherein the internal space (3) holds a pressure, p, acting on the first surface through the sample and acting on the second surfaces through the non-conductive media .

2. An apparatus according to claim 1, where the sample and the non-conductive media meet in an interface which equalizes the pressures of the sample and the non-conductive media.

3. An apparatus according to claim 2, where the interface prevents mixing of the sample and the non-conductive media by use of gravity combined with

properties of the sample and the non-conductive media.

4. An apparatus according to claim 2 or 3, where the interface comprises a separation element which prevents contact between the sample and the non- conductive media.

5. An apparatus according to claim 4, where the separation element is a membrane, a floating piston, a mercury bridge, a filter, a semipermeable membrane, or an ion trap.

6. An apparatus according to any of claims 2-5, where the interface forms a no flow condition at a distance from the first and second surfaces.

7. An apparatus according to any of claims 2-6, where the interface forms a flushing structure configured to establish a protective flow of non-conductive media over the second surface, to thereby separate the wiring spots from the sample by the non conductive media .

8. An apparatus according to any of the preceding claims, where the first and second surfaces are both in fluid communication with a waste space which thereby forms part of the internal space, the waste space being configured for collection of the sample.

9. An apparatus according to any of the preceding claims, comprising two separate inlets into the internal space, one of the inlets being for introducing the sample into the internal space, the other being for introducing the non- conductive media supply into the internal space.

10. An apparatus according to any of the preceding claims, where the sensor is in a holder (4, 31) which forms a first opening (9) between the internal space and the first surface and a second opening between the internal space and the second surface to thereby expose both the first and second surfaces at least to the pressure p.

11. An apparatus according to claim 10, where the first surface forms an inner surface of a flow-cell in the holder.

12. An apparatus according to claim 11, where the flow-cell is configured to receive the sample from a container which forms the first opening between the internal space and the first surface.

13. An apparatus according to any of claims 12, where the container is configured to receive the sample via the first opening from an inlet forming a passage across a wall of the vessel into the internal space.

14. An apparatus according to any of claims 11-13, where the first opening points in an upwards direction relative to gravity, and the holder forms a sample guiding path extending least partly downwards relative to gravity into the flow- cell to enable transport of the sample from the inlet to the flow-cell by gravity.

15. An apparatus according to any of claims 11-14, where the flow-cell is configured to deliver the sample to an outlet out of the internal space.

16. An apparatus according to any of the preceding claims, where the sensor is a piezoelectric sensor.

17. An apparatus according to claim 16, where the sensor is a piezoelectric microbalance sensor.

18. An apparatus according to any of the preceding claims, comprising a temperature control structure for changing the temperature in the internal space.

19. An apparatus according to any of the preceding claims, where the non- conductive media is an inactive gas.

20. A method of analysing an electrically conductive sample under a pressure p, by use of an apparatus according to any of claims 1- 19, the method comprising providing a pressure p in the vessel, injecting the sample under an increased pressure p+Ap into the internal space, passing the sample through the flow path, controlling rejection of the sample from the flow cell, and analysing a signal from the sensor, while the wiring spots are separated from the sample by the non conductive media .

21. A method according to claim 20, where the pressure p is obtained by pressurising the non-conductive media .