JPH052594B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a method for storing high pour point crude oil on the seabed in which high pour point crude oil is stored in an oil storage tank on the seabed by an oil-water displacement method.

[Problem that the invention seeks to solve]

Although this invention is intended for high pour point crude oil, conventional oil storage methods using oil-water replacement methods for low pour point crude oil can be roughly divided into two types. That is, there are two methods: a method in which a partition wall is provided at the oil-water interface, and a method in which a partition wall is not provided.

Methods of installing partition walls can be further divided into cases where oil is stored in the upper layer and cases where oil is stored in the lower layer.
In the former case, it is difficult to dispose of the sludge that accumulates on the partition walls, and in the latter case, the partition walls must have a high degree of sealing performance, which is basically an unreasonable storage format.

On the other hand, methods that do not provide partition walls require measures to avoid mixing of oil and water, as well as methods for introducing and removing oil and seawater.

Furthermore, when high pour point crude oil is stored by an oil-water displacement method, the crude oil that comes into direct contact with seawater flowing into the tank will solidify, making it impossible to operate the tank. Furthermore, heating the entire seawater that flows into the tank in large quantities during crude oil shipping to a temperature above the pour point requires an enormous amount of heat, making it economically unviable.

This invention was made based on the above circumstances,
This is an attempt to realize a rational oil storage method by allowing oil and seawater to be replaced naturally without the need for special partition walls.

[Means for solving problems]

This submarine high pour point crude oil storage method is a method of storing seawater in the lower layer of a concrete oil storage tank installed on the seabed and high pour point crude oil in the upper layer to perform oil and water replacement. The interior is partitioned into multiple sections by vertical bulkheads with through-holes, and heating pipes or hot water nozzles are installed in multiple stages above and below to generate high-temperature heating that responds to fluctuations in the crude oil/seawater interface. The upper crude oil layer is heated and kept at a temperature above the pour point.
The area near the crude oil/seawater interface is partially heated to form a temperature buffer layer of heated seawater below the interface that separates the crude oil and seawater, allowing crude oil to enter and exit from the tank surface and seawater to enter and exit from the tank bottom. , the vertically flowing fluid flow is rectified by a partition wall, and the boundary surface is raised and lowered without disturbing the temperature gradient of the buffer layer.

〔Example〕

The present invention will be described below based on drawings showing embodiments.

This invention stores high pour point crude oil B (hereinafter referred to as crude oil B) in the upper layer of a concrete oil storage tank A (hereinafter referred to as tank A) installed on the seabed 1 using an oil-water displacement method.
At the same time, the area near the crude oil/seawater interface C (hereinafter referred to as interface C) is partially heated to create a temperature buffer layer E (hereinafter referred to as buffer) of seawater D below the interface C. layer E), and this buffer layer E
This separates crude oil B and seawater D.

The heating method is shown in FIG. 4 below. In FIG. 4, heating pipes 3 are arranged in multiple stages above and below the side wall 2 of the tank A to selectively heat the crude oil B or the vicinity of the boundary surface C. Further, the heating pipe 3 can also heat the entire inside of the tank A. Note that the heating pipe 3 is installed inside the side wall 2, and the heating pipe 3 is installed inside the side wall 2 in multiple stages up and down.

In this system, hot water nozzles 4 are arranged vertically in multiple stages in a tank A, and hot water a is discharged from the hot water nozzles 4 directly below the boundary surface C into the buffer layer E to heat the crude oil B from the boundary surface C.

In this method, a pipe 5 is installed vertically in the center of the tank A, and hot water a or steam b is sent into the pipe 5 to heat both the crude oil B and seawater D layers.

In this method, a heating pipe 6 is installed near the bottom of the tank A, and the entire inside of the tank A, including the seawater D, is heated.

By selecting and heating the above heating means, the fluid state of the crude oil B is maintained, and a buffer layer E having a temperature gradient between the crude oil B and the seawater D is formed below the interface C. This buffer layer E always partitions crude oil B and seawater D, and changes up and down depending on the amount of crude oil B stored.

The tank A is of the gravity type, with sand ballast 7 laid on the bottom, the side wall 2 having a double wall structure, and the inside partitioned into a lattice shape by partition walls 8. The partition wall 8 is suitably provided with through holes at various places so as not to hinder the flow of the crude oil B, and this partition wall 8 allows the crude oil B to flow appropriately. It also serves as a buffer to prevent turbulence in the buffer layer E.

The double-walled side walls 2, 2 ensure safety against collisions during towing and operation, and during operation, the portion sandwiched between the side walls 2, 2 is filled with seawater D to separate the tank liquid from the external seawater. At the same time, it forms a temperature buffer layer with the tank A and functions as a water seal for tank A.

The crude oil B is received and paid into the tank A through a crude oil receiving and receiving pipe 9 provided on the surface of the tank A. The seawater D is taken in and taken out through a number of downwardly facing inlets and outlets of a seawater inlet/outlet pipe 10 which is inserted through the side walls 2, 2 and provided at the bottom of the tank A, thereby suppressing the flow of seawater from concentrating locally. Although the interface C moves up and down due to the inlet and outlet ports for crude oil B and seawater D, the vertical flow of the fluid is rectified by the partition wall, and disturbance of the temperature gradient in the buffer layer E is prevented. As a result, the buffer layer E is always interposed between the crude oil B and the seawater D while keeping a constant distance therebetween.

〔Effect of the invention〕

This invention is constructed as described above, and this storage method uses a temperature buffer layer that is naturally formed by partially heating the vicinity of the crude oil/seawater interface.
Crude oil heated above the pour point and low-temperature seawater are separated, and the interface is moved up and down so as not to disturb the temperature gradient of this buffer layer. Therefore, it is possible to prevent the trouble of high pour point crude oil coming into contact with low temperature seawater and solidifying. The thermal energy required to form the buffer layer is smaller than when heating the entire seawater, and because of the double-walled structure, there is less heat dissipation from the crude oil layer and the buffer layer, allowing for effective use of heat and reducing thermal energy costs. It will be cheaper.

Note that sludge accumulates at the bottom of the oil storage tank, so its disposal is not a problem.

[Brief explanation of the drawing]

FIGS. 1 and 2 are longitudinal sectional views of the oil storage tank, with FIG. 1 showing the tank when the crude oil is being discharged, and FIG. 2 showing the tank when the tank is full of crude oil. FIG. 3 is a cross-sectional view of the oil storage tank. FIG. 4 is a longitudinal sectional view showing a model of the heating method inside the tank. A... Concrete oil storage tank, B... High pour point crude oil, C... Crude oil/seawater interface, D... Seawater, E... Temperature buffer layer 1... Seabed, 2... Side wall, 3... Heating pipe, 4... Hot water nozzle, 5... Pipe, 6... Heating piping, 7... Sand ballast, 8... Bulkhead, 9... Crude oil receiving and receiving pipe, 10... Seawater inlet/outlet pipe.

Claims (1)

[Claims] 1 This is a submarine oil storage method in which oil and water are replaced by storing seawater in the lower layer of a concrete oil storage tank installed on the seabed and high pour point crude oil in the upper layer.The tank has a double wall structure with through holes inside. Multiple partitions are formed by open vertical bulkheads, and heating pipes or hot water nozzles are installed in multiple stages above and below, and the heating height is selected according to fluctuations in the crude oil/seawater interface. By heating the oil and keeping it at a temperature above the pour point, it partially heats the area near the crude oil/seawater interface, forms a temperature buffer layer of heated seawater below the interface that partitions the crude oil and seawater, and transfers the crude oil to the surface layer of the tank. Seawater is taken in and taken out from the bottom of the tank, and the flow of fluid flowing up and down is rectified by a partition wall, and the boundary surface is raised and lowered without disturbing the temperature gradient of the buffer layer. Point crude oil storage method.