GB2264172A - Sampling bottle - Google Patents

Abstract

Bottle comprises: a body (1) having an upper chamber (2) and lower chamber (3) and an internal (22) bore extending from said second chamber, via a valve port (23), to the outside of the bottle body; a bottle cap with integral external first and second valve ports (7, 11) with internal bores extending from the valve ports to the chambers of the bottle body; a tube (14) connecting the first inlet valve port to the second lower chamber; a piston (16) slidable within said first upper chamber; and controlling means for opening and closing a second internal bore within the bottle cap. Utility is in collecting e.g. oil or gas samples from wells. Samples can be collected from a continuous flow. An embodiment with a single bore body is further disclosed. <IMAGE>

Description

LIQUID / GAS FLOW SAMPLING This invention relates to a novel sampling device and sampling method for collecting a representative sample of a liquid or gas for accurate physical and chemical analysis. This is particularly, though not exclusively, applicable to the collection of oil and / or gas samples from an oil production well.

Fluids extracted from an underground oil reservoir may contain a number of chemical components such as water, hydrocarbon liquids and dissolved gases. Accurate analysis of a representative sample provides invaluable information regarding the physical and chemical properties of hydrocarbon present in the underground reservoir and this is essential to the monitoring of the extracted fluid as well as to the overall efficient and effective management of the producing well.

However, collection of a representative sample can be a difficult task as the quantity of a sample may only represent a infinitesimal proportion of the whole. Extracted fluids are under very high pressures and often contain dissolved gases which may be released at a critical pressure known as the "bubble point". The release of dissolved gases during collection of the sample can be detrimental as it nearly always results in a slight modification of the liquid composition and an unrepresentative sample. It is therefore imperative to use a sampling method and apparatus that enables representative samples to be collected for accurate physical and chemical assessment.

A number of sampling techniques are known; the most preferable and recommended technique is the Mercury Displacement Method.

This involves careful and controlled displacement of mercury from a high pressure stainless steel sample bottle.

However, this technique has a number of distinct disadvantages.

In particular there is the hazardous nature of mercury, a volatile and highly poisonous metal, that demands the most strict control and handling. Filling sample bottles is hazardous and time consuming, and all mercury containing receptacles open to the air must be partially filled with water to prevent the mercury evaporating and contaminating the immediate working vicinity. Mercury spillages are dangerous and difficult to clean up. Sample bottles capable of withstanding high pressures are generally very heavy because of the wall thicknesses required; a sample bottle full of mercury is particularly heavy and difficult to handle and manoeuvre. In addition to these aspects, the displaced mercury must be carefully recovered and contained at the sampling site.

Furthermore, to obtain a valid sample at least three sample bottles should be filled to ensure full control of representativity and a sufficient quantity of sample for a normal study. Therefore the collection process must be repeated at least three times, a time consuming and repetitive task.

This known method of sampling is discontinuous, in that only a specified quantity of mercury may be displaced and if the optimum sampling conditions are not attained, the collection must be repeated with a fresh sample bottle.

According to a first aspect of the present invention there is provided a sample bottle which comprises: a bottle body having a first upper chamber adjacent to a second lower chamber and an internal bore extending from said second chamber, via a valve port, to the outside of the bottle body; a bottle cap with integral external first and second valve ports with internal bores independently extending from the valve ports to the chambers of the bottle body; a tube connecting the first inlet valve port to the second lower chamber; a piston adapted to be slidable within said first upper chamber; and, controlling means for opening or closing the second internal bore within the bottle cap.

The present invention provides a sampling device and sampling method which eliminates the use of mercury altogether and allows collection from a continuous flow of fluids. This removes the inconvenient and hazardous working conditions involved with the use of mercury and allows more than one sample bottle to be filled in the same operation thereby substantially reducing the time involved in performing the collection.

The present invention provides a sample bottle for the controlled collection of a representative sample of fluids to enable further physical or chemical analysis. The invention is particularly applicable to the collection of high pressure oil / gas samples from an oil producing installation. However, it must be understood that the invention is also applicable to the sampling or collection of fluid samples in general and not specifically to high pressure oil products.

The first aspect of the invention comprises a double chambered bottle body, a bottle cap adapted to be secured to the bottle body and a piston slidable within one of the chambers.

The invention has the advantage that the sample of fluid may be collected from a continuous flow of fluids without the need to displace mercury or another fluid. In comparison, known techniques are discontinuous and this is a significant disadvantage from the point of view of collecting a sufficient quantity of fluid required for a representative sample, where the collection operation may be repeated several times. Furthermore, excess or unwanted fluids are returned to the downstream side (low pressure) of the separator during the continuous flow operation. This ensures that sample fluids, which may contain flammable, corrosive or toxic components, are not released into the atmosphere or into the immediate working vicinity.

Conveniently, the first upper chamber and second lower chamber may be separated by a removable partition. This facilitates access to the lower chamber in which the collected fluid sample will be trapped and contained. This is important for periodically inspecting the sample bottle and also provides access to the lower chamber should it require cleaning.

Generally the diameter of the first upper chamber is -larger than that of the second lower chamber.

Preferably, the tube extends through the piston of the first chamber.

A sample agitator may be provided in the second lower chamber of the sample bottle.

According to a second aspect of the present invention there is provided a sample bottle which comprises: a bottle body having a single bore and a sample inlet port with an internal bore extending from the inlet port to the bottle body bore via an inlet valve; a piston adapted to be slidable within the bore; a bottle cap with integral external first and second outlet valve ports with internal bores independently extending from the valve ports to the bottle body bore via independent valves (first and second outlet valves); an agitating ring; a central rod with a internal bore extending into the bottle body bore and connecting the first outlet port of the cap to the bottle body bore.

The second aspect of this invention comprises a single bore bottle body, a bottle cap adapted to be secured to the bottle body, a central rod, piston slidable within the bore of the bottle body, and an agitating ring.

A sample agitator may be provided between the piston at top of bottle body bore.

The sample agitator may take the form of a perforated disc and can move freely up and down the length of the lower chamber. The purpose of this feature is to encourage quick stabilisation of pressure of the fluid sample contained in the lower chamber and is achieved in practice by inverting the sample bottle several times. Other known agitating means may be employed to assist the stabilisation of pressure, for example, a solid sphere.

Retaining means may be provided on the bottle cap to prevent accidental removal or loosening of the cap. This is important especially when the sample bottle is holding a sample of fluid at high pressure and accidental, partial loosening or opening of the bottle cap, for example during transportation, could be particularly dangerous. Escape of hazardous fluids, particularly flammable petroleum products, would constitute a serious safety hazard.

According to a third aspect of the invention there is provided a method of collecting a representative fluid sample from a continuous flow of fluids where one or more sample bottles are connected together for simultaneous collection of samples.

The sampled fluid flows through the bottle or bottles until collection is required. Once a sample has been collected and contained, pressure may be relieved from the upper chamber of the sample bottle, to provide a gas cap prior to transportation, without any loss of fluid from the bottle.

Preferably, the sample bottles are connected in series. In this configuration the fluid flows continuously through all of the sample bottles prior to collection. This method allows any number of bottles to be filled in one simple operation without having to disconnect and reconnect a fresh sample bottle once each bottle has been filled. A more controlled collection can be achieved and differences between collected samples as a result of poor collection procedure are eliminated.

The sample bottles may be connected in parallel for simultaneous or independent collection of fluid samples. By connecting the sample bottles in a parallel configuration a continuous flow of fluids may be sampled and a sample collected by each sample bottle independently. This configuration would be useful if a sample was to be collected at different times and a serial configuration inconvenient.

Embodiments of the present invention will now be described, by way of example only, with reference to the accompanying drawings, in which: Figure 1 is a schematic drawing of a known oil sampling arrangement, connected to an oil production installation, for collecting a sample of oil at high pressure; Figures 2a and 2b are an assembled and exploded cross sectional view respectively of a sample bottle according to the first aspect of the invention showing internal detail of the individual parts; Figure 2c is an assembled cross-section view of a sample bottle according to the second aspect of the invention.

Figure 3 is a schematic drawing of a sampling arrangement using the invention to simultaneously fill and collect more than one oil sample.

Figure 1 is included to provide a comparison between a known method of collecting a sample of oil and the sample collecting bottle and method according to the present invention.

The known method, in this instance, the Mercury Displacement Method, involves connecting a high pressure stainless steel sample bottle 45, filled with mercury, to a sampling point 41 of a separator tank 49, via a valve and high pressure hose assembly 42. A small quantity of water or oil is placed in a graduated container 46 into which the mercury will be displaced. This ensures that the working environment and the operator will not be contaminated with mercury vapour. The top valve 44 of the sample bottle is opened and, once pressure stabilisation has been achieved, the bottom valve 47 is opened. Tap 48 is carefully opened and a measured quantity of mercury is allowed to be displaced from the sample bottle 45. The tap 48 is then closed followed by valve 44 and then valve 42.Tap 8 is reopened and an additional small quantity of mercury displaced to provide a gas cap (by a reduction in pressure within the bottle) necessary for transportation of the filled sample bottle. All valves are closed, the bottle is disconnected and is ready for dispatch to a laboratory for analysis.

The sampling bottle of the present invention will be described and shown in connection with collecting high pressure oil samples from an oil production installation. However, it must be understood that the invention is also applicable to the sampling or collection of fluid samples in general and not specifically to high pressure oil products.

Figures 2a and 2b show a sample bottle according to the present invention in which a main sample bottle body 1, generally cylindrical in shape, has a first upper chamber 2 adjacent to a second lower chamber 3.

The upper and lower chambers are separated by a partition 19.

Said partition is removable, has a central recess 20 on the first chamber face, and one or more sample ports 21 and central hole 24 extending therethrough. The lower end of tube 14 locates with and is held by the central recess 20 in the partition 19.

A piston 16 is adapted to be slidable within the first upper chamber 2. The tube 14 extends through a hole 17, orientated along the cylindrical axis of the piston; with a seal being formed between the two by an 'o' ring type pressure seal 25a.

A similar seal is used to create a pressure tight seal between the piston and the walls of the cylindrical upper chamber 2.

Therefore, fluids present in chamber 3 are prevented from leaking past or flowing into the region of chamber 2 above the piston 16.

A groove 30 in the upper region of the sides of the piston 16 holds a teflon ring which assists the smooth sliding movement of the piston within the upper chamber 2.

A sample bottle cap 6 is adapted to be secured and sealed to the bottle body by threaded portions 13 on the cap and corresponding threaded portions 4 on the internal surface of the bottle body.

However, other known configurations of sealing means are known and may be utilised to achieve a pressure tight seal.

Said sample bottle cap 6 comprises integral first and second valve ports 7 and 11, and a central recess 10 on its internal surface 27 designed to accept, and seal with, the upper end of the tube 14, thereby allowing passage of sample fluids from the first inlet port 7 to flow direct to the second chamber, via internal bore 9 and central tube section 10.

An internal bore or passage 26 extends from the second valve port 11 to the first upper chamber of the bottle, via a piston valve, fitted to the valve port 12. The piston valve may be used to open or close the internal passage 26 at 28 along the passage.

The sample bottle cap is provided with cap retaining means 8 to prevent movement of the cap whilst the sample of high pressure fluids are collected, sampled, transported or stored. Said retaining means may take the form of a pin or bolt acting to prevent rotation of the cap 6. However, other known retaining mechanisms may also be effectively employed to prevent movement or to lock the bottle cap in position. A pressure relief port 32 allows the release of residual pressure in the sample bottle as the bottle cap is removed. This is essentially a safety feature and eliminates hazards involved with the release of pressure when the bottle cap is removed.

'0' rings 29 are provided in the sample bottle cap to ensure a pressure tight seal with the bottle body. Though pressure seals of this type have been used throughout, similar or alternative known pressure sealing means may be usefully employed to the same effect.

A sample agitator 31 is located in the lower chamber 3 where the sample fluid is contained. The sample agitator may take the form of a perforated disc or a ball which may freely move up and down the lower chamber and is used to encourage the stabilisation of pressure in the chamber. This is achieved by inverting the sample bottle several times and allowing the agitator to move up and down the lower chamber.

In operation, valves controlling the exit or entry of fluids to or from valve ports 7 and 23 are opened. The piston valve connected to the valve port 12 is closed, effectively sealing internal bore or passage 26. Fluids may enter the sample bottle via valve port 23 and flow, via internal bore 22 into the lower second chamber 3 and exit the bottle through tube 14 and bore 9.

Therefore a continuous flow of fluid moves through the sample bottle.

As or when it is desired to take the sample, the valve controlling the exit of fluids from valve port 7 is closed; fluid is retained in the second lower chamber 3. The valve controlling entry of fluids into valve port 23 is then closed and the sample may then be disconnected from the oil sampling point (once it has been turned off).

For transportation of the bottle it is necessary to have a gas cap - this is easily achieved by releasing pressure from the first upper chamber 2 by a piston valve connected to valve port 12. Pressure may be released from this chamber through the internal bore 26 and valve port 11. Due to the imbalance of pressure that this procedure creates on either side of the piston, a flow of sample fluid from the lower chamber 3 to the upper chamber 2, via sample ports 21 may occur as the piston rises Furthermore, piston 16, 'o' ring seals 25, 25a and the presence of a metal to metal seal at 33 prevent direct contact between the sample fluid and the main pressure bearing 'o' rings 29 of the sample bottle.Therefore, there is less risk of the sample fluid, which under some circumstances may contain corrosive constituents, contaminating these seals and consequently the sample bottle should have a longer serviceable or working life.

In particular it is known that both free or dissolved gases present in the collected sample may be absorbed into the 'o' ring seals and cause deterioration of those seals.

Referring to Figure 2a, a sample bottle according to the second aspect of the invention is designated generally by the reference numeral 201. The upper and lower chambers 202 and 203 respectively are defined by the length of internal bore 205 of central rod 204 which connects central rod outlet port 219 to the second outlet valve port 217 via passage 208 and second outlet valve 221. The lower end of the central rod 204 locates with central recess 206 in the bottle cap 212, with a seal being formed between two 0'-ring type seals 207 and its internal surface 218. The top end of the central rod 204 locates in bore of the sample inlet passage 208.

A piston 209 is adapted to be slidable within the bottle body bore. The central rod 205 extends through a hole 210 orientated along a cylindrical axis of the piston 209, with a seal being formed between two o'-ring type seals 211 and central rod 205.

A similar seal is used to create a pressure tight seal between the piston and walls of the cylindrical with two o'-ring type seals 211. The central rod 204 also extends through a hole 229 orientated along the cylindrical axis of the agitator ring 230.

A sample bottle cap 212 is adapted to be secured to the bottle body by threaded portions 213 on the bottle cap 212 and corresponding threaded portions 214 on internal surface of the bottle body 201. Two 0'-ring type seals 215 create a pressure tight seal between cap and wall of the cylindrical. However, other known configuration of sealing means are known and may be utilised to achieve a pressure tight seal.

The sample bottle cap 212 comprises integral first and second outlet valve ports 216 and 217 and a central recess 206, on its internal surface 218 designed to accept, and seal with, a lower end of the central rod 204. This allows the passage of fluid from the central rod outlet port 219, central rod bore 205 and passage 220 via second outlet valve 221, to second outlet valve portion 217. The second outlet valve 221 may be used to open or close passage 220 at the sealing face 222 of the second outlet valve 221.

A passage 223, extends from first outlet valve port 216 to the second lower camber 203, via first outlet valve 224. The first valve 224 may be used to open or close passage 223 at the sealing face 225 of the first outlet valve 224.

The bottle body 201 comprises inlet valve port 227, internal passage 208 and internal threads 214 for securing bottle cap 212.

The inlet valve 227 may be used to open or close passage 208 at the sealing face 228 of the inlet valve 227.

The sample bottle cap 212 is provided with a cap retaining means 231 to prevent movement of the cap whilst the sample of high pressure fluids are collected, sampled, transported or stored.

Retaining means in the form of a pin or bolt maybe used to prevent rotation of the cap 212. However, other known retaining mechanisms may also be effectively employed to prevent movement or to lock the bottle in position.

Prior to operation the bottle is prepared by filling the bottle with liquid or gas at pressure below piston 209 via first outlet valve port 215, first outlet valve 224 and passage 223 with second outlet valve 221 closed and inlet valve 227 open. The liquid or gas is trapped below piston 209 on closing first outlet valve 224 and inlet valve 227 when piston 209 is at the top of chamber 202 (top of bottle body bore).

In operation, inlet valve 227 controlling the entry of sample is opened. The second outlet valve 221 is opened allowing the liquid or gas below piston 209 to be displaced by the incoming sample, via central rod outlet portion 219, central rod bore 205, passage 220, second outlet valve 221 and second outlet valve port 217. Piston 209 moves down chamber 203 as the liquid or gas below is displaced by the incoming sample above. Once 'o'-rings 11a of piston 209 have passed over central rod outlet port 219 sample flow replaces that of the displaced liquid or gas, also trapping a given volume of liquid or gas below piston 209 in chamber 208. Therefore a continuous flow of sample through the sample bottle is achieved.

As or when it is desired to take the sample, second outlet valve 221 is closed; sample is retained above the piston 209, inlet valve 227 is then closed and the sample bottle may be disconnected from the oil sampling point (once it has been turned off).

For transportation of the bottle it is necessary to have a gas cap. This is easily achieved by releasing liquid from chamber 203 hence reducing pressure within the sample bottle. Liquid in chamber 203 is released by opening first outlet valve 224 allowing the liquid to exit via passage 223, first outlet valve 224 and first outlet valve port 216. Due to the pressure drop this creates within the sample bottle, the monophasic sample which is above piston 209 in chamber 202 reverts to a diphasic sample (a sample with liquid and gas phases), hence creating a gas cap for transportation.

If gas is used to fill the sample bottle below piston 209 prior to sampling there is no need to create a gas cap as one already exists.

To recombine the sample, ie obtain a monophasic sample, the pressure within the sample bottle is increased by injecting fluid below piston 209 via first outlet valve port 216, first outlet valve 224 and passage 223. Ensuring that all other valves are closed. The recombination process is aided by the agitation ring 230 moving within the sample when the sample bottle is repeatedly inverted.

Figure 3 shows how more than one sample bottle according to the invention may be filled simultaneously in a single operation.

Sample bottles 55, 56 and 57 are connected in series to the oil sampling point 52 with suitable connection means (high pressure valves and hoses). The fluid to be sampled is allowed to flow continuously through all of the sample bottles entering the first bottle 55 via bottom valve 51 and exiting via top valve 54 of the last bottle 57. This arrangement ensures that any free gas phase constituents flow downstream and do not accumulate in any of the sample bottles which would result in an unrepresentative sample.

During continuous flow conditions, excess or unwanted fluids are routed to the downstream line (low pressure) of the separator.

This ensures that the continuous flow is contained and that fluids are not released into the atmosphere. This is especially important if the fluid to be sampled is hazardous, for example, containing flammable, corrosive, volatile or toxic components.

When collection of the sample is required, bottom and top valves 53 and 54, controlling the exit and entry of fluids to each individual sample bottle are closed beginning with the last bottle (the one downstream of the others). This isolates a fluid sample in each sample bottle. A gas cap is provided by release of pressure from each bottle, as described previously.

Once residual pressure in the connecting hoses has been released, the sample bottles may be disconnected and dispatched to a laboratory for analysis.

Bubble Point Determination: The sample bottles and sampling method according to the invention may be used to determine the "bubble point" of a sample of oil on site. The "bubble point" is the pressure at which dissolved gases are released from the sample fluid. Small measured quantities of water, present in the upper chamber 2, are withdrawn via the piston valve connected to the valve port 12.

The stabilised pressure is noted after each measured quantity of water is removed. Pressure stabilisation is achieved by inverting the sample bottle several times causing the sample agitator 31 to move up and down the lower chamber 3. The bubble point may be ascertained from the analysis of these measurements, and shown in more detail in the specific example below.

The "bubble point " of the sample may be determined during the sampling process. The hoses which connect bottle 56 to 57 and connect bottle 57 to a downstream inlet are configured to enable bottle 57 to be inverted while remaining in line. To perform the "bubble point" analysis valves 53 and 54 of bottle 57 are closed and the procedure previously described is followed. If the "bubble point" indicates that the sample is invalid, sampling may continue by opening valves 53 and 54 of bottle 57. This process may be repeated several times until the sample is validated. This procedure is of particular value when sampling wellhead fluids.

EXAMPLE A sample bottle contains, in the lower chamber 3, a 640 ml sample of single phase oil at 6000 psig and 200 ml or water in the upper chamber 2. 1 ml quantities of water are withdrawn from the upper chamber via the piston valve connected to the valve port 12. The sample bottle is inverted several times after each withdrawal to stabilise the pressure of the sample and then the stabilised pressure recorded. One set of possible results are shown below

PRESSURE VOL. OF WATER [psig] REMOVED [mli 6000 0 5360 1 4720 2 11 4060 3 3440 4 3200 5 3180 6 3165 8 3150 10 A plot of water volume against pressure yields the graph shown in Figure 4. The release of dissolved gas causes a discontinuity at a pressure Pb in the plot and this is the bubble point pressure (3230 psig).

Claims (18)

1. A sample bottle comprising: a bottle body having a first upper chamber adjacent to a second lower chamber and an internal bore extending from said second chamber, via a valve support, to the outside of the bottle body; a bottle cap with integral external first and second valve ports with internal bores, independently extending from the valve ports to the chambers of the bottle body; a tube connecting the first inlet valve port to the second lower chamber; a piston adapted to be slidable within said first upper chamber; and controlling means for opening and closing a second internal bore within the bottle cap.

2. A sample bottle according to claim 1 wherein the first upper chamber and second lower chamber are separated by a removable partition.

3. A sample bottle according to claim 1 or claim 2 wherein the diameter of the first upper chamber is larger than that of the second lower chamber.

4. A sample bottle according to any one of the preceding claims wherein the tube extends through the piston of the first chamber.

5. A sample bottle according to any one of the preceding claims further comprising a sample agitator provided in the second lower chamber sample bottle.

6. A sample bottle according to claim 5 wherein the sample agitator is in the form of a perforated disc, which disc is moveable freely up and down the length of the lower chamber.

7. A sample bottle according to any one of the preceding claims further comprising retaining means on the bottle cap.

8. A sample bottle comprising: a bottle body having a single bore and a sample inlet port with an internal bore extending from the inlet valve-port to the bottle body bore via an inlet valve; a piston adapted to be slidable within the bottle body bore; a bottle cap with integral external first and second outlet valve ports with internal bores independently extending from the valve ports to the bottle body bore, via independent valves; an agitating ring; a central rod with an internal bore extending into the bottle body bore and connecting the first outlet port of the cap to the bottle body bore.

9. A sample bottle according to claim 8 wherein the central rod extends through the piston and agitating ring substantially along the full length of the bottle body bore, is locatable within the bottle cap, and is retainable at the top end of the bottle body bore.

10. A sample bottle according to claim 8 or claim 9 further comprising a sample agitator positioned between the piston at the top of the bottle body bore.

11. A sample bottle according to claim 10 wherein the sample agitator comprises a perforated disc freely moveable between the piston and the top of the bottle body bore.

12. A sample bottle according to any one of claims 8 to 11 further comprising retaining means provided on the bottle cap.

13. A method of collecting a representative fluid sample from a continuous flow of fluid where one or more sample bottles are connected together for simultaneous collection of samples.

14. A method according to claim 13 wherein the sample bodies are connected in series.

15. A method according to claim 13 wherein the sample bodies are connected in parallel.

16. A sample bottle substantially as hereinbefore described with reference to Figures 2a, 2b, 2c, 3 and 4 of the accompanying drawings.

17. A sample bottle substantially as hereinbefore described with reference to Figures 2c, 3 and 4 of the accompanying drawings.

18. A method substantially as hereinbefore described with reference to the two Figures 2a, 2b, 2c, 3 and 4 of the accompanying drawings