JPH0324517B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to the separation and/or purification of natural resources that are fluid hydrocarbons, and in particular to such separation and purification conducted offshore, such as in oil or natural gas well drilling platforms. / or related to purification.

Crude oil produced from oil wells often consists of a mixture of organic fluids and aqueous media and may be contaminated with inorganic solids. The composition of crude oil can vary widely. Typically, organic fluids are extracted from approximately 99% (wt) of the crude oil at the start of production.
It can account for up to about 10% (wt) of the crude oil at the end of a well's economically viable life. Organic fluids are mixtures of hydrocarbons, of which a small fraction (e.g. C ₁ ,
C ₂ and C ₃ hydrocarbons) can be gaseous under normal atmospheric conditions, and their major portion is liquids, for example the C ₇ and above hydrocarbon fraction is 80% (wt. ) and more.
The aqueous medium is typically water or brine
These are suspensions, dispersions, and
It can be present in the form of an emulsion or a mixture. The inorganic solids (if present) are typically gravel.

In conventional practice, crude oil (typically at a pressure of several million Pascals at the well head) is introduced into a series of separator banks, each of which is exposed to an appropriate pressure for one minute to several tens of minutes. It is held for a period of time to separate the various components of the crude oil. These separators can hold hundreds of tons of crude oil, so the platform must be sufficiently designed to support the weight of such crude oil in addition to the weight of other parts of the platform. It is necessary to design it with sufficient strength. Moreover, such separators occupy a disproportionately large portion of the limited space available on oil production platforms and other offshore facilities. Accordingly, there is a movement to modify the refining/separation processes performed on crude oil to provide platforms that are cheaper to construct, construct, and install.

Natural gas at wellheads is often contaminated with organic and/or aqueous liquids;
Therefore, it is often desirable to remove such contaminants before pumping them from the wellhead. Removal of liquid pollutants is often carried out in mist removal towers. Such towers occupy a large proportion of the limited space available in offshore gas well installations.

Here, we have invented a method by which fluid fossil fuel can be purified using a centrifugal separator.

The present invention involves charging a fluid fossil fuel containing a plurality of phases with different densities into a rotor having a permeable element mounted on a rotatable shaft coaxial with the rotational axis of the rotor, and discharging the fluid fossil fuel in the rotor. Subjecting the fuel to centrifugal force causes the denser phase of the fluid fossil fuel to move generally outwardly with respect to the axis of rotation of the rotor, while the less dense phase moves inwardly with respect to the axis of rotation of the rotor. at least one of the fluid fossil fuels comprising a plurality of phases of different densities, characterized in that the method comprises the steps of: causing at least one hydrocarbon phase to be discharged from the rotor; The invention relates to a method for separating two components.

"Fluid" herein means gas or liquid, or a mixture thereof.

It is often convenient to pass the fluid fossil fuel through a number of suitable rotors in series (e.g. mounted along a common axis), with each rotor undergoing its own separate separation/purification step. It is.

In a preferred embodiment of the invention, the crude oil from the wellhead is charged at suitable pressure to the first stage rotor(s) where a major portion of the C ₁ and C ₂ fractions are desorbed and removed as a gas phase. .
The liquid phase is then charged to a second stage rotor at suitable pressure where the aqueous medium is separated from the liquid hydrocarbon phase.

The operating pressure of the process of the invention is such that, after removal of gaseous hydrocarbons and aqueous medium, there is no need to repressurize the liquid hydrocarbon fraction prior to pumping it out of the facility. This results in significant savings in energy requirements compared to conventional offshore purification/separation methods.

The portion of the rotor that is charged with fluid fossil fuel in the method of the invention is often determined by the density and amount of the component to be removed. for example,
When water is to be removed from crude oil, the crude oil is charged to the rotor in an intermediate zone between the rotor's outer periphery and its rotating shaft, the water is rejected from the rotor near the rotor's outer periphery, and the organic phase is removed from the rotor. is ejected from the rotor near the rotation axis. Liquid hydrocarbon/gaseous hydrocarbon mixtures in which gaseous hydrocarbons are the predominant component, such as mixtures where gaseous hydrocarbons account for approximately 80% by weight and 99% by volume (such mixtures are often When it is desired to separate the mixture (which is in the state of Emitted from nearby. A liquid hydrocarbon/gaseous hydrocarbon mixture in which liquid hydrocarbon is the main component, for example, a mixture in which liquid hydrocarbon accounts for approximately 95% by weight (the liquid:gas volume ratio is approximately 1:3) When attempting to separate the liquid phase, the mixture is charged into the rotor near the rotor's axis of rotation, and the liquid phase is discharged from near the outer periphery of the rotor.
The gas phase is then released near the rotation axis.

If inorganic solids are present in the crude oil to be separated and/or purified by the process of the invention, it is preferred to remove such solids before processing the crude oil by the process of the invention. However, although it is not a preferred embodiment to remove such inorganic solids in the method of the present invention, it is within the scope of the present invention to perform such solid removal in the method of the present invention.

The transparent element attached to the rotor in the method of the present invention is based on the Japanese Patent Publication No.
Transparent elements such as those described in JP-A-63-52921 (corresponding to EP 20055) and JP-A-54-85179 (corresponding to EP 2568) are preferred. As described in these publications, the element has a large interfacial area (sometimes referred to as internal area).
and is permeable to fluid fossil fuels, and may be integrated or composed of a plurality of independent components. In the former case, it is formed to have pores. In the latter case, permeable pores are constructed within or between the individual independent components. The independent components include impermeable particles (beads), powders, etc. of glass, plastic, metal, etc., for example.
Also exemplified are those consisting of strands, fibers, fibrils, or filaments. The metal skeleton foams shown in the examples (such as those sold under the trade name "Retimet") are preferred examples.

The interfacial area and porosity of the permeable element are:
It is selected taking into account, inter alia, the following factors: the viscosity of the liquid passing through it, the size of any solid particles that may be present, and the relative volumes of the gaseous and liquid components of the liquid fossil fuel. When a permeable element is used, it has an interfacial area of about 500 m ² /m ³ or more, preferably about 1500 m ² /m ³ or more, and/or about 85% or more, preferably about 90% or more It is preferable to have a porosity.

The method of the invention is generally applicable to separating a first liquid from a second liquid or gas that is immiscible therewith and has a different density in the separation and/or purification of fluid fossil fuels. .
However, if it is desired to reduce the size and weight of the equipment in which such separations are conventionally carried out,
The present invention is particularly valuable. This is particularly significant when such separation and/or purification is carried out offshore, in particular on oil or gas production platforms. The method according to the invention is carried out on the deck of a barge, ship (e.g. tanker) or other vessel.
In particular, it can also be carried out when an organic liquid is separated from an aqueous liquid, for example seawater, and the aqueous liquid is to be dumped into the sea.

Over the past eight years or so, offshore oil and gas production methods have improved, allowing oil and gas to be recovered from depths and locations not previously considered economically viable. Developments have been made to do so. These developments have resulted in sea-bed structures connected to one or more wells and tied to surface production equipment by flexible tubing.

Initial work in this field has been carried out by so-called "initial production systems", i.e. systems in which production is carried out on floating, semi-submersible drilling wells carrying gas/oil separation equipment, such as those adopted by the Argyll oil field. represented by The degassed crude oil is returned to the offshore structure and then loaded onto tankers.

Recent developments include “New Scientists”
(November 5, 1981), page 375, is the "Underwater Manifold Center" (UMC). The UMC is intended to be located on the seabed and carries equipment for oil extraction and diversion of oil flow from several external wells. Again, the crude oil is processed on a surface platform to which the UMC is connected with flexible tubing.

Particularly for initial production systems using floating production equipment not configured for the particular oil field tapped, production is severely limited by the weight and space capacity of the floating platform. In this regard, the benefits of adopting the method of the invention are quite obvious.

However, the overall trend in the development of technology to take advantage of low economic or remote wells is to locate more equipment on the ocean floor. The equipment used according to the invention is potentially suitable for this purpose. In particular, the equipment according to the invention is lightweight and compact compared to conventional separation equipment. That size factor is particularly important for equipment that must be designed to be used under the external pressures that exist at depth in oil well locations that are currently being developed.

The separation equipment used in accordance with the invention may be located directly at the wellhead of an oil well or may be located at a distance from the wellhead. For example, it may be installed with other ancillary equipment such as a manifold to collect oil or gas from multiple external wells.

Although little (if any) practical experience is available in the use of permanently moving equipment built on the seabed, the special nature of rotor equipment
It is believed that it does not present any substantial problems to the skilled designer of offshore equipment. It is thus desirable to encapsulate the rotor, or the entire separation facility, in an isolated chamber or "air bubble" that is completely impermeable to seawater. With the compact equipment that can be characteristically used with the method of the invention, such isolation chamber configurations are even more practical than with conventional separation equipment.

One characteristic of subsea rotor equipment may be that it requires regular maintenance and/or repair. To facilitate such operations, it is desirable to design and construct the rotor installation as a "module," preferably as a module that is entirely separable from the rest of the seabed structure.

The separation operations of the present invention are suitably carried out at pressures near or equal to atmospheric pressure to efficiently remove gaseous components to reduce them to the level of their equilibrium concentration at such pressures. be. Following the separation operation, the separation product may be repressurized if desired. Thus, for example, gaseous product hydrocarbon streams may be recompressed and reinjected into oil-bearing formations to aid in pressure maintenance and oil production in the formation. Alternatively, the gas stream or the second gas stream may be incinerated at sea surface. Degassed crude oil can be pumped directly to the surface and loaded onto tankers, or transported by pipeline to the coastline. Equipment for repressurizing or pumping the separated product is advantageously installed in the aforementioned isolation chamber or "air bubble".

The degree to which gas-liquid separation on the seabed obviates the need for ancillary surface equipment depends on the specific circumstances of the well, such as its location and distance to existing surface equipment.
It is also influenced by general economic considerations. For example, if a well is located near an existing production platform that has seawater degassing and reinjection equipment, the need for such equipment specifically for the well may be eliminated. Alternatively, such equipment may be located in a subsea structure that combines separation equipment with degassing and reinjection equipment. Similarly, if there is already a pipeline installed nearby to transport oil to the coast, it is a simple matter to connect a new well to that pipeline, and if such a pipeline exists, If not, it would be necessary to provide seaside facilities to transport the products by tanker.

Even if the placement of separation equipment on the ocean floor does not necessitate the installation of surface equipment, it can significantly reduce the weight and space requirements of the platform, and also allow the platform to be a compact structure. , or to make space in the platform available for other (perhaps optional) facilities, such as facilities for gas or water reinjection.

By locating small rotor-type separation facilities at seabed locations, the possibility of "initial production" or oil production prior to the construction and commissioning of permanent production facilities is created. Because the equipment used in the present invention is smaller than conventional equipment, a mobile wellhead separation equipment that can be transported to an oil field, operated until the permanent equipment is put into service, and then moved to another oil field can be readily implemented. The mobile equipment can be designed to be transported by hoist;
Alternatively, a propulsion means may be provided to facilitate movement from oil field to oil field. Such propulsion means may be remotely controlled and/or controlled by an operator located in an attached cabin or by means of an inverter.
Or it can be operated manually.

The power necessary to drive the rotary separation equipment may be supplied by electrical lines from sea or land sources, where appropriate. Alternatively, the necessary power can be generated on-site. For example, one or more turbines may be provided that are powered by hydrocarbon liquid under pressure produced from a well.

The invention will now be described with reference to the accompanying drawings.

In FIG. 1, the rotor is mounted on the shaft 6,
This allows it to be rotated. The rotor may consist of a permeable element, such as a permeable element made of metal skeleton foam sold under the trademark "Retimet". The rotor 5 is arranged axially within a substantially cylindrical container 7. Container 7 is in chamber 8
and a supply pipe 9 having an orifice 10 for introducing crude oil at its lower end, a first discharge pipe 11 for liquid phase discharge, and a second discharge pipe 1 for gas phase discharge.
2. This device is Labyrinth Seal 1
3 and a mechanical seal 14.

In operation, high pressure crude oil is charged to rotor 5 via supply pipe 9 and orifice 10.
The rotor is rotated at such a speed that the crude oil experiences an acceleration greater than the acceleration due to gravity (G). The crude oil is subjected to an acceleration of, for example, 10 to 1000G, preferably 100 to 500G.

Under the influence of centrifugal force, detachment occurs within the rotor 5,
The gas and liquid phases separate, the liquid phase flowing generally radially outwardly within the rotor 5 into the chamber 8;
It is then discharged via a first discharge pipe 11 and the gas phase flows generally radially inwardly within the rotor and discharged via a second discharge pipe 12 .

In the device shown in FIG. 2, the rotor 5 is the rotating shaft 6.
The equipment is installed in The upper surface 15 of the rotor includes a group of circularly arranged holes 16 and a flange 17.
is formed. The rotor 5 is arranged coaxially within a substantially cylindrical container 7. Container 7 is in chamber 8
, a supply pipe 9, a first discharge pipe 11 for liquid phase discharge, and a second discharge pipe 1 for gas phase discharge.
2. The second discharge pipe 12 has a flanged base 18 . labyrinth seal 1
3 is provided between the flange 17 and the container 8,
A labyrinth seal 19 is provided between the top surface 15 of the rotor and the flanged base 18, and a mechanical seal 14 is provided between the shaft 6 and the container 7. The rotor 5 may be, for example, an annular element made of metal skeleton foam (eg sold under the trademark "Retiment").

In operation, a gas containing a small volume fraction of the liquid phase is supplied to the rotor 5 via the supply pipe 9 and the bore 16.
supply to The rotor is rotated such that the gas and liquid experience a centrifugal force that exceeds the acceleration of gravity (G). Gas and liquid are separated in the rotor 5,
The liquid phase flows outwardly within the rotor into the chamber 8 and from there is discharged via a first discharge pipe 11, and the gas phase flows inwardly within the rotor via a second discharge pipe 12. It is discharged.

In FIG. 3, a base 20, a cylindrical outer wall 21,
A rotor 5 consisting of a cylindrical inner wall 22 and an annular top 15 is mounted on a rotating shaft 6. Cylindrical outer wall 2
1 has a perforation 23 in its lower part, and the cylindrical inner wall 22 also has a perforation 24 in its lower part. A cover-like liquid discharge means 25 is attached to the outside of the cylindrical outer wall 21. A group of circularly arranged holes 16 and a flange 17 are formed on the top 15 of the rotor 5 . Mounted within the rotor symmetrically about the axis of rotation of the rotor is an annular permeable element 26 made of a permeable material. In this embodiment the permeable element is made from metal skeleton foam (trademark "Retiment").

The rotor 5 is arranged coaxially within a substantially cylindrical container 7. The container 7 delimits a chamber 8 and includes a supply pipe 9, a first discharge pipe 11 for discharging the first liquid phase and a second discharge pipe 18 for discharging the second liquid phase (with a flange 18 at the base). ) is provided. Labyrinth seals 13, 19 and mechanical seal 14 are arranged as in the previous example.

In operation, a liquid fraction of crude oil is fed to permeable element 26 via feed pipe 9 and bore 16 . The aqueous and organic liquid phases separate within the pores of the permeable element under the influence of the centrifugal force generated by the rotation of the rotor. The aqueous phase moves outward within the pores of the permeable element and perforates 2
3 and the cover 25 into the chamber 8 and is then discharged via the discharge pipe 11. On the other hand, the organic phase flows inwardly through the pores of the permeable element and is discharged via the perforations 24 and the discharge pipe 12.

In Figure 4, crude oil from the wellhead is fed to one or both gas separators. The separation process according to the invention takes place in the gas separator. This gas separator may typically be of the type of apparatus of FIG. The crude oil from which gaseous components have been removed is discharged from the rotor and supplied to the next process, and the separated gaseous components are separately removed and sent to, for example, a fuel gas reservoir or an incineration chimney. Although a single stage gas separation is shown in Figure 4, it is preferable to separate the gases by two or more gas separation steps in series (e.g., a series of rotors operated at progressively lower pressures). There are many things.

Following gas separation, the crude oil is fed to a liquid separator where another separation step according to the invention is performed. The liquid separator is typically of the type of device shown in FIG. The aqueous layer from the liquid separator can be dumped into the sea, for example, or used for reinjection into an oil well. The organic liquid from the liquid separator can be fed to a suitable storage tank or directly to a ship or pipeline.

Having two independent parallel separation process lines gives great operational flexibility and allows for example if one line is shut down for maintenance, the other line can continue operating. .

[Brief explanation of the drawing]

The drawings depict apparatus for implementing various aspects of the invention. FIG. 1 is a schematic cross-sectional view of a rotor arrangement that can be used to separate small amounts of gas from a liquid in the method of the invention. FIG. 2 is a schematic cross-sectional view of a rotor arrangement that can be used to separate small amounts of liquid from a gas phase in the method of the invention. FIG. 3 is a schematic cross-sectional view of a rotor arrangement that can be used to separate two liquid phases in the method of the invention.
FIG. 4 is a flow sheet showing a series of steps for oil production in which the method of the present invention can be adopted. Rotor: 5, Rotation shaft; 6, Supply pipe; 9, First discharge pipe (low density); 11, Second discharge pipe (high density); 12.

Claims (1)

[Claims] 1. A fluid fossil fuel containing a plurality of phases with different densities is charged into a rotor having a permeable element attached to a rotatable shaft coaxial with the rotational shaft of the rotor, and subjecting the fluid fossil fuel to centrifugal force to cause the denser phase of the fluid fossil fuel to move generally outwardly with respect to the axis of rotation of the rotor, while the less dense phase moves inwardly with respect to the axis of rotation of the rotor. separating at least one component of a fluid fossil fuel comprising a plurality of phases of different densities, characterized in that the method comprises the steps of: causing the rotor to release at least one hydrocarbon phase; and removing at least one hydrocarbon phase discharged from the rotor. how to. 2. The method according to claim 1, wherein the fluid fossil fuel is crude oil. 3. Crude oil containing a gas phase is charged to said rotor near its axis, the gas phase is removed from the rotor near its axis, and the liquid hydrocarbon phase is removed from a location near the radially outer periphery of the rotor. The method described in Scope No. 2. 4. Crude oil containing an aqueous liquid is charged to the rotor at an intermediate zone between its periphery and its axis, the aqueous liquid is withdrawn from a location near the radially outer periphery of the rotor, and the liquid hydrocarbon phase is transferred to the rotor near its axis. A method according to claim 2 or 3, taken out from . 5. The method of the claims, wherein the fluid is natural gas. 6. Natural gas containing a liquid phase is charged to the rotor in a zone intermediate between its outer periphery and its axis, the liquid component is removed from a position near the radially outer periphery of the rotor, and the gaseous hydrocarbon phase is transferred near its axis. 6. The method according to claim 5, wherein the method is removed from the rotor. 7. The method of claim 6, wherein the permeable element has an interfacial area of 500 m ² /m ³ or more and a voidage of 85% or more. 8. The method according to any one of claims 1 to 7, which is carried out on the seabed.