Hydrocarbon production system, method for performing clean-up and method for controlling flow

Abstract

The present invention relates to a device for transmitting fluid from a subsea producing module (8) to a subsea receiving module (9) comprising a choke valve (3) in a main flowpath (7) of the fluid. A bypass line (2) is arranged in parallel to the choke valve (3) and the bypass line (2) is connected to the main flowpath (7) by a bypass connection (1).

Description

FIELD OF THE INVENTION[0001]The present invention relates to a hydrocarbon production system comprising a subsea well, a subsea production module, a subsea receiving module and a choke valve situated in a main flow path of production fluid from the well, between the production module and the receiving module.BACKGROUND OF THE INVENTION AND PRIOR ART[0002]In a subsea installation, several wells or Xmas Trees are connected to a common manifold. The pressures in these wells are different, and to be able to transmit oil or gas to the common manifold, the pressure needs to be substantially equal. Thus, a choke valve is installed between each Xmas Tree and the manifold to adjust and control the pressure.[0003]It is a standard procedure to perform a clean-up process in a Xmas Tree as a basis for commissioning. Traditionally, the clean-up is done through the choke valve. The product of the clean-up can be fluids with different viscosity, and it can also comprise different types and dimensio...

AI Technical Summary

Benefits of technology

[0011]This prevents blockage and malfunction of the choke valve, and consequently the need for replacement of damaged chokes that could easily happen if the fluid was transmitted through the choke valve and not the bypass line. It also removes the problem of changing choke valves according to amount of fluid flow and production phase.

[0023]In a third aspect of the invention it relates to a method for controlling the flow in a hydrocarbon production system comprising a subsea production module, operatively connected to a subsea well, a subsea receiving module and a main flow path, including a subsea production choke valve fluidly connecting the production module and the receiving module, wherein during a situation with a pressure in the well higher than the pressure necessary to deliver the desired production flow rate, the choke valve is choked to limit the flow rate to a desired flow rate; and that during a situation when a flow rate is desired, which substantially corresponds to the maximum delivery rate of the well, a bypass line is opened to direct the flow outside the choke valve. This makes it possible to merely open the bypass when the pressure in the well has dropped to a certain level over time. It removes the necessity for replacing the choke valve with another valve with different properties, i.e. less restriction. It also makes it possible to open up for full pressure from the well in situations when it is not necessary to limit the flow from the well, e.g., if another well with lower pressure connected to the same manifold is shut down, and the present well can be allowed to produce at maximum without interfering with other wells.

Problems solved by technology

This complex clean-up product comprising debris provides a substantial risk of choke malfunction and blockage when transported through the choke valve.

On the other hand, no existing choke valve vendor can or will give a guarantee that the choke can tolerate this, as it is almost impossible to know what type debris will flow through the choke and what dimension the debris will have.

But still it will always be a risk for blockage of trim ports in the choke valve.

Both good controllability and maximum flow are features required by the oil operators, but they are not sufficiently present in any choke valves on the market today.

This replacement procedure is a complex procedure that involves use of e.g. an ROV (Remote Operated Vehicle) and it also requires shutting down the installation during the replacement procedure.

As mentioned above there is today no choke valves on the market that are able to handle such an amount of debris without quickly becoming degraded, unless the pressure of the fluid and the flow rate is very low.

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