MEMBRANE-SAMPLE CONTAINER

Abstract: A sample container (1) especially for oil/gas samples consists mainly of a spherical body formed of two half parts (2, 3) with a metal membrane (4) fixed between the flanges of the two half parts. The membrane has a configuration complementary to the configuration of each half part and is substantially hemispherical with a planar portion (8) perpendicular to the in-/outlet passages (9, 10). The flange (13) of the membrane forms the packing between the two halves of the container. The membrane may be equipped with a reinforcement plate (14) perpendicular to the in-/outlet passages. To ensure that the container is leakage proof at large pressure variations, the container is at the oil/gas side equipped with a resilient packing nose (16) and labyrinth packing (17). The in-/outlet passages are formed as annular gaps (21). The container has only metallic packings.

Description: Membrane - Sample container The invention relates to a container for transportation and long time storage of oil/gas samples. During oil and gas production, automatic samplers are sent down to the well for collection of samples. The samples are transferred to the transportation containers which are sent to the analysis laboratory. Samples from oil/gas separators are also transferred to the transportation containers for transportation to the laboratory. Some samples are to be stored for many years and therefore, high demands are set to the containers diffusion tightness. It is very important that the containers being clean, sterile and free of air to get representative samples. The containers usually used for this purpose today, are based on using mercury to replace the air in the containers. When oil/gas is filled into the container the mercury will be displaced and transmitted to an extra container for collection. Today when using mercury, strict safety procedures are practised. The area where the oil/gas is transferred to the transportation containers is being shut off. The operators must use special accident preventing clothes and gas masks and are submitted medical examination (urine specimen) both before and after the transferences. Mercury is poisonous and do therefore represent an environmental problem. It has therefore been of great interest having developed a container free from mercury in which the accuracy of analyzing of oil/gas would be of no less quality than before. Such a container is earlier described in Norwegian patent application No. 862367. It consists of a hollow body with in- and outlets at each side of the container. The container is built up by two half parts in which a metal membrane separa¬ tes the hollow body into two chambers. The container may have an inner lining where the membrane is firmly welded between the two halves of the lining. The in- and outlets are arran¬ ged perpendicularly to the membrane. Initially the membrane is directed towards one of the halves of the container. When filling oil into the container, the membrane will reverse to¬ wards the opposite side. Such a container must be used over a very wide range of pressures from about 0.5 - 700 bar. The containers are tested at a pressure of above 1000 bar. The use of the container as described in Norwegian patent application No. 862367, resul¬ ted in leakage problems at pressure testing. Further, it was found that the membrane material chosen is very important. When using steel membranes,, the membrane thickness had to be reduced so much that a controlled reversal of the membrane would be impossible. Even with membrane thichnesses below 5 mm, the differential pressure over the membrane was so high that it is only applicable for samples from the bottom of the well. The object of the invention is to develop a sample container which could be used for all types of oil/gas samples that are taken when testing a well or a separator. It is important to avoid use of mercury without lowering the analysis accuracy of the samples. Another object is to provide a container being tight during pressure variations. In addition, it is important that the membrane is inert to the environments, diffusion tight and that the pressure difference over the membrane is low. These and other objects of the invention are obtained with the apparatus described below, and the invention is further defined and characterized in the following claims. The sample container consists mainly of a spherical body including two container halves having a metal membrane fixed between the two container halves' flange portions. The mem¬ brane and the two container halves are complementary shaped being hemispherical with a planar portion arranged perpen- dicular to the containers in- and outlet passages. The flange of the membrane forms the packing between the two container halves. The membrane may be equipped with a reinforcement plate positioned perpendicular to the in- and outlet pas¬ sages. The container may be used for a very wide pressure range, in the order of 0.5 - 700 bar. Therefore, the revers¬ ing pressure of the membrane must not exceed 0.5 bar. Lead was found being a well suited membrane/packing material, but other pure, soft metals may also be used. To ensure a leakage proof container at large pressure variations, the container is equipped with a resilent packing nose at the oil/gas side. The container has only metal packings. The in- and outlet passages are formed as annular gaps that together with the reinforcement plate reduces the creep of the membrane mate¬ rial. Other features of the invention will be described in more detail below and with reference to the figures 1-3, wherein Fig. 1 shows the partial sectional view of the container and the valves Fig. 2 shows the shape of the membrane Fig. 3a shows the hemispherical part of the container at the oil/gas side Fig. 3b shows the labyrinth packing at the oil/gas side Fig. 3c shows the inner plug inside the in- and outlet passages. Figure 1 shows the partial sectional view of the container 1. It consists of two hemispherical parts 2,3 with a metal membrane 4 inbetween. The two parts are screwed to a sleeve 5. Both the container halves and the membrane have planar portions 6,7,8 in order to ensure that the membrane is rever¬ sed uniformly and under control. It was found convenient to use a composition of water/glycole as counterpressure medium in the container. Thereby, the container 1 has an inlet/ outlet passages 9 for water/glycole at one side and an equal arrangement for oil/gas at the other side. These are arranged perpendicular to the membrane. It is equipped with high pressure valves 11 at each side. Further, the container has a control opening 12 in order to test the gas tightness. The container shown in the figure has a volume of 0.7 1. The design pressure is 750 bar and the containers working field reaches from about 0.5 to 700 bar. The containers are being pressure testet at 1125 bar. When such a container is being used for storage of oil/gas samples, it is demanded that the membrane is completely dif¬ fusion tight. Therefore, metal was chosen as membrane mate¬ rial. Another demand is that the differential pressure over the membrane have to be low in order to make the container applicable for a wide range of samples, ie. that the membrane material is easily reversed. Both the choice of material and the membrane design influences this. Figure 2 shows the membrane design 4 with a flange 13 and a planar part 8. The membrane has a configuration complementary to the configuration of the two inner hemisphercial parts. The planar part will cause start of the reversal of the membrane and also a uniform reversal. The membrane is uni¬ formly thick and may have a reinforcement consisting of a metal plate 14 at the water/glycole side. At such high pressures as being used here, it was found necessary to use metallic packings. The membrane will func¬ tion both as a separator between the two parts of the con¬ tainer and also ensure tightness. Surprisingly, it was found that lead has qualities making it well suited as a membrane material. By using a lead membrane about 0.7 mm thick, it may be obtained reversal pressures as low as 0.1 - 0.2 bar. This makes the container suited for a wide specter of samples. Other pure, soft metals that nor¬ malize quickly after treatment may also be used. For instance gold, silver and aluminium (ductile metals) . The membrane also will ensure packing between the container halves. Figure 3a shows the container half 3 at the oil/gas side in more detail. This one is formed with a hemispherical inner surface with a planar portion 7 perpenducular to the in- and outlet passages 10. The container half which is made of steel, has threads 15 for fastening to the sleeve 5 (fig. 1). To ensure necessary packing between the two container halves, a resilent nose 16 and a labyrinth packing 17 is arranged at the oil/gas side. This is shown in more detail in fig. 3b. The deflection of the nose is restricted by an annular bar 18 (fig. 1) laid in a annular grooves 19 underneath the nose. Between the bar and the annular groove, there is some tenth millimetres margin. The annular bar 18 restricts the nose from being compressed and it is therefore avoided that mate¬ rial of the nose reaches the yield point and looses its flexibility. Initially the lead membrane is formed to wanted shape and thereafter it is mounted into the container half 2 at the oil/gas side. The membrane is made with a diameter somewhat less than the container half because of the creeping of lead. After assemb¬ ling and pressure testing, the membrane will be positioned tightly against the inner container surface. The flange of the membrane 13 is forced towards the labyrinth packing with a pressure of about 40 tons so that it is being stucked and fills the recesses in the labyrinth 17. As the container halves with the lead membrane inbetween is screwed together, an axial pressure in the order of 90 - 100 tons between the nose 16 and the labyrinth packing 17 arises. Thereby the nose is compressed depending on the margin bet¬ ween the bar and the groove (0.15 - 0.2 mm). The nose 16 is shaped being 1 - 1.5 tenths mm higher on the outer than the inner side. When screwing together the halves of the container one will start pressing the top of the nose and squeese lead down into the concave wedge 20 so that it also is being packed with metal. With a pressure in the order of 700 bar the container will be extended about 0.06 mm. The two functions of the nose will therefore be to compensate the extension that arises with increased pressure in the container, and at the same time compensate for creeping of the material in the packing sur¬ face. If an increase in pressure above 1125 bar should arise, there will be no oil/gas leakage, but water/glycole will leak. This because the labyrinth packing together with the concave wedge between the hemispherical parts, makes a better packing than at the other side where glycole and water are pumped in. In order to avoid problems with membrane puncture at high pressures, the container's in- and outlet passages 6,7 are formed as an annular gap 21 (fig. 1) connected to the inte¬ rior of the container. This is achieved by mounting a plug 22 as shown in fig. 3c into the container's openings 6,7. Fluid is then lead into the plug through openings 23 and further out through the the openings 24 and into the annular gap (0.1 - 0.15 mm) formed by the plugs outer side and the openings 6,7 in the container. In this way the pressure is spread. The in- and outlet passages in the shape of annular gaps will together with the membrane's reinforcement plate prevent creeping of the membrane material. Metallic displacement bodies 25 are also arranged in the gas/oil's in- and outlet passages in order to lower the container's "dead volume". When mounting the container one of the container halves 2 (without labyrinth packing) is being screwed into the sleeve 5 after the valve 11 is mounted. With the valve in a vertical position the hollow body is filled with glycole/water. The other body 3 with the labyrinth packing 17 is being placed in an hydraulic press after the valve is mounted. Here the membrane is pressed against the labyrinth packing such that it is getting stuck and fills the recesses in the labyrinth. Then the body is screwed into the sleeve towards the other one, till an axcial pressure of 90-100 tons is obtained as packing pressure. Because of creeping of the membrane 4 the screw operation is repeted at least 24 hours later. The container is then turned so that the glycole/water side is turned up. Helium (1 bar pressure) is filled into the oil/gas side of the container. The membrane is reversed and the filling of helium is stopped when glycol/water leakeε out of the valve. The valves are closed. After 24 hours, possible gas leakages from the container is tested. After this test, the container is connected to a high pressure pump and glycole/water is pumped in until a pressure of 1125 bar. The membrane is then reversed back and helium is forced out. The container holds this pressure for 0.5 hours and the manometer is checked in order to register possible leakages. Thereafter, the pressure is reduced to 5 bar. At this pressure the container is deliv¬ ered to the users. The container receives oil/gas samples at a pressure range of 0.5 to 700 bar. When being used the container is fixed to the sampling area and the valve towards the oil/gas is opened. The pressure from water/glycol will resist the pressure from the oil/gas. Not until the valve towards the water is opened, the membrane vil begin reversing because water/glycole is being forced out and oil/gas flows in. The membrane is re¬ placed after one time use and the container is testet as described above. These containers are useful both for sampling and trans¬ ference of samples and use of mercury is avoided. Because a low reversal pressure for the the membrane is achieved, the sample containers may be used for all sorts of oil samples taken for well testing or separator testing. These samples (samples from the bottom of the well, well head samples and separator samples) may be stored in the containers for a long period of time. While the resilent nose compensate for pres¬ sure variations, the containers will be free of leakage.

Claims: Patent claims 1. Sample container (1) especially for oil/gas samples consisting of a body with spherical interior surface formed of two half parts (2,3) which are arranged for being joined together along the pheriphery thereof, with a metal membrane (4) inbetween, which can be reversed between the two half partes of the body, and where in-/outlet passages (9,10) are arranged perpen¬ dicular to the membrane and where both membrane and each half part of the body have planar portions (8,9,10) perpendicular to the respective passage, c h a r a c t e r i z e d i n t h a t a resilent packing nose (16) is arranged at one of the half parts (3) of the container. 2. Container according to claim 1, c h a r a c t e r i z e d i n t h a t an annular bar (18) is arranged in an annular groove (19) below the nose (16) to restrict the deflection of the nose. 3. Container according to claim 1 , c h a r a c t e r i z e d i n t h a t the outer part of the nose (16) is higher than the inner part. 4. Container according to claim 1, c h a r a c t e r i z e d i n t h a t the packing nose (16) is equipped with a labyrinth packing (17) and where the flange of the membrane (4) is arranged to completely fill the recesses in the labyrinth packing and thereby being completely stuck and stop the creeping of the membrane material. 5. Container according to claim 1 and 4, c h a r a c t e r i z e d i n t h a t the membrane (4) is made of a soft metal. 6. Container according to claim 1, C h a r a c t e r i z e d i n t h a t the membrane is equipped with a circular reinforcement plate (14) of metal. 7. Container according to claim 1, c h a r a c t e r i z e d i n t h a t the in-/outlet passages (9,10) are formed as annular gaps (21) connected to the interior of the container. 8. Container according to claim 1, c h a r a c t e r i z e d i n t h a t replacement bodies (25) are arranged in the in-/outlet passages for gas/oil. 9. Container according to claim 1, c h a r a c t e r i z e d i n t h a t it has only metallic packings.

Inventors: BOEE EINAR, BOEE, EINAR
Applicants: NORSK HYDRO AS, NORSK HYDRO A.S
Application year: 1989
Main classification: E21B49
IPC codes: E21B49, F17C1, G01N1