JPS62253594A - Cut-off of seawater in drill moon pool - Google Patents

Abstract

PURPOSE:To prevent the streaming-up of seawater into a moon pool during navigation by forming a jet film by jetting out the seawater taken-in from a blow, in a drill well moon pool of an excavation vessel, etc. used for the investgation of the sea-bottom resources. CONSTITUTION:Seawater taking-in ports 5 and 5a and formed on the both broadsides of the bow side of a moon pool 2 and connected to the introducing pipes 6 and 6a, and a plurality of thin jet pipes 7-7a branched from the introducing pipes 6 and 6a are opened to the lower part wall surface of the moon pool 2. When an excavation vessel navigates, the seawater taken-in from the taking-in ports 5 and 5a is introduced into the injection pipes 7 and 7a from the introducing pipes 6 and 6a and jetted out at a high speed towards the stern from the opened port part, and forms a jet film on the undersurface of the moon pool 2, and allows the seawater to flow rearward. Therefore, the streaming-up of the seawater into the moon pool 2 and generation of eddy current can be prevented.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a seawater shielding method for a drill well/moon pool installed in a semi-subrig, drilling ship, etc. used for exploration and excavation of seabed resources.

[Conventional technology]

When investigating and excavating seabed resources such as oil, it is possible to use structures built offshore, tow a structure (semi-subrig) to a designated location and moor it, or to sail a drilling ship to a designated location. There are cases where it is moored. Among these, semi-subrigs and drilling ships have holes called drill wells and moonpools (hereinafter referred to as moonpools) for installing risers in structures or ship hulls.

FIGS. 4 and 5 are a side view and a plan view schematically showing an example of the above-mentioned drilling ship, in which 1 is a hull, and 2 is a moon pool penetrated through the hull.

T like this! ! When cutting a ship, seawater rises up inside the moonpool during navigation, creating eddy currents on the inner wall of the moonpool, which increases resistance, increases power costs, and has a negative impact on the ship's hull. There's a problem.

In order to solve this problem, a plate made of hard rubber or the like is slidably provided below the moonpool 2, and the plate is slid to close the moonpool during navigation, or To,
Some proposals include a steel bellows that opens and closes using a hydraulic mechanism.

[Problem that the invention seeks to solve]

However, all of these systems have complicated structures and require large-sized equipment, resulting in increased costs.

[Means for solving problems]

The present invention has been made in order to solve the above problems, and in a drilling ship etc. equipped with a drill well/moon pool, water is taken in from the bow side of the drill well/moon pool. A drill well moonp that ejects water toward the stern! The present invention provides a seawater shielding method.

[Effect]

When the ship sails, the seawater that flows into the introduction pipe from the intake port,
It is ejected from the ejection pipe into the moon boules, forming a diene film and preventing seawater from rising up.

〔Example〕

FIG. 1 is a side view schematically showing the main parts of a drilling ship in which the present invention is implemented, and FIG. 2 is a plan view thereof.

According to the present invention, seawater intake ports 5, 5a are provided on both sides of the bow side of the moon pool 2 and connected to the introduction pipes 6, 6a, and further, from the introduction pipes 6, 6a, a plurality of thin ejection pipes 7 to 7c are connected. It is designed to branch out and open at the lower wall surface of the moon pool 2.

When the drilling ship configured as described above sails, the intake port 5,
The seawater flowing in from 5a flows through the inlet pipes 6 and 6a to the ejection pipe 7.
, 7n, and is ejected from the opening at high speed in the stern direction, forming a jet film on the lower surface of the moonpool 2, and flowing out to the rear. Thereby, it is possible to prevent seawater from rising into the moon boule 2 and from generating eddies. In addition, in the embodiment, the width W of the seawater intake ports 5 and 5a is 20 to 30 cm.
, the diameter D1 of the introduction pipes 6 and 6a is 20 to 40 cm, and the ejection pipe 7
, 7a was set to have a diameter D2 of 5 cm.

The principle of the present invention will be explained in more detail as follows. Now, for example, if the diameter D1 of the introduction pipe 6 is 30 cm and the diameter D2 of the ejection pipe 7 is 5 cm, the introduction pipe 6 is
, 6a, assuming that the flow velocity of the seawater flowing into each jet pipe 7 to 7 is 10 knots I·(5,14i+/s), which is the same as the total ship speed.
The flow velocity of seawater jetting into the moon pool 2 from c is derived as follows:Q, = (flat)'π・vl Q,=special)2π・v2 However, ql is the flow rate of the introduction pipe 6, q2 is the flow rate of the jet pipe. The flow rate vl of 7 is the flow rate of seawater flowing through the inlet pipe 6, v2 is the flow rate of seawater flowing through the ejection pipe 7.If four ejection pipes 7 are provided, then QI=402,',D'・V,=40"V2,° , V2=(F) "X', X VH246,
3 (m/s) (1) That is, when the ship speed is 10 knots, there are 48.3 m/s from each jet pipe 7 in the moonpool 2.
Since seawater is ejected at a flow rate of +m/s, a sufficient seawater protection effect can be obtained.

Note that the flow velocity obtained from the above equation (1) does not take into account the frictional resistance of the inlet pipe 6, the ejection pipe 7, etc., the influence of the boundary layer of the flow around the hull, etc. However, if the cross-sectional areas of the inlet pipe 6 and the ejection pipe 7 are selected so that the value calculated by the above formula (1) is at least faster than the theoretically calculated inflow velocity of seawater, the rise of seawater into the moon pool 2 can be suppressed. The scales are obvious. In practical use, if the speed of seawater jetting into the moon pool 2 obtained from equation (1) is at least twice the speed of the ship, rising of the seawater can be prevented.

In addition, although the above-mentioned Example showed the case where four ejection pipes 7 were provided, it goes without saying that the number can be increased or decreased as appropriate.

〔Effect of the invention〕

As is clear from the above description, according to the present invention, there is no need for equipment to open and close the moonpool by external force each time a trial or work is carried out, and by simply providing a seawater intake, an introduction pipe, and an ejection pipe, The effect of implementation is extremely large, as it automatically prevents seawater from rising into the Moon Ball and reduces resistance.

[Brief explanation of drawings]

Fig. 1 is a side view schematically showing the main parts of a drilling ship in which the present invention is implemented, Fig. 2 is a plan view thereof, Fig. 3 is an enlarged view of the main parts of Fig. 2, and Fig. 4 is a normal FIG. 5 is a side view schematically showing a drilling ship, FIG. 5 is a plan view thereof, and FIG. 6 is an explanatory diagram showing the state of seawater flow during a trial. 1: Hull, 2: Moon bulge, 5.5a: Seawater intake,
6, 6a: Inlet pipe, 7.7a: Ejection pipe. Representative Patent Attorney Masaru Sato Figure 1 Figure 2-3

Claims (2)

[Claims] (1) In a drilling ship or the like equipped with a drill well/moon pool, seawater is taken in from the bow of the ship and the drill well/moon pool is
A seawater shielding method for a drill well/moonpool characterized by ejecting water from the bow side of the moonpool toward the stern side. (2) The seawater shielding method for a drill well/moon pool according to claim 1, wherein the flow rate of the spouting seawater is at least twice the speed of the ship.