Small vessels can easily dock or berth in ports. However, large vessels with significant oil or gas transportation capacity are massive. Maneuvering them in ports is very challenging. As a result, the single-point mooring method is useful, as it allows vessels to stay in open water. But how do Single Point Mooring (SPM) Offshore Operations work?
Undoubtedly, mooring is one of the most convenient ways of holding ships or vessels in the ocean. However, there is a difference between a single point and a conventional mooring. In SPM, vessels are secured at a single point rather than being moored at multiple points. In this article, I will discuss everything about the single-point mooring offshore operations.
What is Single Point Mooring (SPM) Offshore Operation?
Before discussing working, let’s first learn about what SPM is!
Single-point mooring offshore operation (SPM) is a type of mooring used by large vessels. It is an arrangement through which the ship or vessel stays in the open sea. SPM is used at offshore oil and gas platforms. The vessel remains tied to a single connection point: a buoy. So, the ship can move and even rotate 360 degrees.
Generally, vessels face different weather and waves in the ocean. In SPM, the vessel tied to a buoy can move. This simple movement allows the vessel to withstand harsh winds and waves at sea. Operators use marine hoses to transfer gas or oil to offshore platforms. Without SPM, the transfer of this oil and gas from offshore platforms would be nearly impossible.
Are you wondering about the purpose of single-point mooring offshore operations? This mooring method is handy as it allows vessels to stay in the open sea easily. There are many offshore oil and gas facilities with no coastline. Without SPM, staying in a vessel at one point is not possible. SPM allows vessels to remain at a single location for both loading and unloading oil and gas from offshore platforms.
Remember, some ports are shallow. However, large vessels may not be able to maneuver or stay. In such cases, the ships remain several kilometers away where the water is deeper. So, the captain and crew can use assist boats and travel to ports. However, SPM enables safe offshore oil and gas transfer by providing a stable mooring point.
Components of Single Point Mooring (SPM) Offshore System
SPM is not just a single process; it is a complete system comprising several components. These components work together to ensure ships remain stably moored in the open sea. In the section below, I will discuss some of the most essential parts of the SPM system.
1- Mooring Buoy
A mooring buoy is a floating structure to which the vessel is tied. This buoy floats on the surface of the water. Why? That’s because it is made from a material that has excellent buoyancy. As a result, it floats and keeps the vessel in place. Mooring buoys come in various colors and sizes.
2- Mooring Lines or Chains
Mooring lines or chains hold the buoy to the anchor present at the seabed. As a result, the buoy remains stationary on the water surface. The ship is then tied to this buoy through the mooring hawser. These mooring lines are strong enough to keep the buoy stationary even in harsh weather. This makes the buoy work smoothly, keeping the ship in one area while allowing it to weathervane with the wind.
3- Anchors or Piles
The anchor is installed at the seabed in the position. This anchor is installed precisely at the spot where the buoy is supposed to be present. The buoys are then tied to the anchor via mooring lines or chains. The purpose of this anchor is to keep the buoy intact. It is a misconception that a ship is directly attached to this anchor present at sea. The vessel is moored to the buoy, not directly anchored to the seabed.
4- Subsea Pipelines & Hoses
Single Point Mooring (SPM) Offshore Operation is incomplete without subsea pipelines and hoses. The pipes are generally on the seabed. These pipelines are long and connected to offshore oil or gas facilities. They carry the oil from the facility to the SPM. The hoses connect the SPM buoy to the vessel’s manifold.
In the SPM system, oil is transferred from the hoses to the vessel’s tank. Remember, this transfer of oil is not affected by the vessel’s movement due to waves or winds. This is because of a swivel system that prevents the hose from twisting. So the oil transfer continues even as the ship rotates through 360 degrees.
How does Single Point Mooring (SPM) Offshore Operation Work?
Generally, ships drop their anchors when they want to stay. The anchor drops to the seabed and keeps the vessel in place. Right? However, the SPM differs in that it does not involve dropping an anchor in the open sea. In the section below, I will discuss how SPM works in three easy-to-understand steps.
Step 1: Ship Approach & Positioning
First, the vessel approaches the SPM location. Remember, these locations are in deeper water so that vessels can maneuver easily. Additionally, they’re located near the offshore oil or gas facilities or platforms. As I mentioned earlier, the primary purpose of SPM is to load and unload oil and gas from offshore facilities.
The vessel arrives at the SPM location with a tugboat. This step is not left to the ship’s captain’s skill. That’s because even a slight misalignment can cause the vessel to fail to moor to the buoys. Therefore, small tugs assist the vessel in approaching and positioning at the right spot. Remember, if the vessel fails to follow its assigned track, it can even damage pipes or other SPM structures.
Step 2: Mooring & Hose Connection
After positioning the ship, the next step is to connect the vessel to the mooring buoy. As mentioned earlier, the buoy is present on the surface of the water. It is attached to the anchor present on the seabed. The vessel is then tied to the buoy using a mooring hawser. This robust mooring line ensures a strong connection between the buoy and the vessel.
Once the ship is tied, the next step is to connect the buoy and the ship using hoses. Remember, the hoses transfer oil or gas from the buoy to the vessel’s storage system. The buoys collect oil from the pipelines at the subsea level. Before connecting hoses, they are checked to ensure they do not leak so they transfer the oil or gas securely.
Step 3: Cargo Transfer & Disconnection
Once the hose is connected, the oil transfer begins. Remember, pipelines first supply the oil or gas to the buoy. The buoy has a swivel system that ensures smooth ship movement. The hose then draws oil from the buoy and delivers it to the vessel’s storage system. This transfer of oil or gas is monitored carefully.
The modern vessel comes with an advanced monitoring system. This system detects the pressure and ensures there are no leaks during this transfer. The emergency team remains alert during these operations. In case of any issue, the team can quickly take action and prevent any unexpected accident. Once the transfer is complete, the hose is disconnected.
After that, the mooring hawser is disconnected from the buoy. As a result, the vessel is released and moves away. The buoy remains in place and continues to serve for the loading and unloading of oil and gas. This process is the same for both offshore oil and gas facilities and for transfers from other tanks or ships. The ship will be tied to buoys, and oil will be transferred through them.
Advantages of Single Point Mooring Offshore Operation
Single Point Mooring (SPM) Offshore Operation is a widely used method. Almost all offshore oil and gas facilities use this procedure to safely transport their contents. Here are some key benefits of this offshore operation:
- This system allows the transport of oil and gas without the need to build massive ports or docking facilities. Without this, transportation from offshore platforms would have been challenging and expensive.
- SPM can easily handle large vessels. The buoy attached to the anchor is very strong. So it is capable of holding large ships during oil or gas transportation. This system can even handle VLCCs (Very Large Crude Carriers) and supertankers.
- One of the significant advantages of SPM is safety. The vessel attached to a buoy can move in 360 degrees. This means it can easily withstand harsh weather, winds, and waves, and will remain in a specific area. Additionally, oil or gas can be transferred even when a ship is moving due to winds or waves.
- The Single Point Mooring (SPM) Offshore Operation is very simple. The SPM location consists of a buoy attached to an anchor on the seabed. The vessel approaches the buoy, connects via the mooring hawser, transfers cargo, and then departs. Due to its simple components, this system requires little to no ongoing maintenance.
- The SPM allows the transfer of goods at very affordable pricing. This system is not limited only to offshore oil and gas facilities. You can even use it to transfer oil from one large tanker to another. You won’t need traditional port infrastructure or offshore terminals for this transportation.
Schlussfolgerung
In conclusion, SPM provides the simplest and most practical way to load and unload cargo on offshore platforms. Many offshore oil and gas facilities use this system to ensure smooth transportation. It involves several integral components in these operations. These include the mooring buoy, mooring lines, anchors, subsea pipelines, and hoses. The vessel approaches the SPM location, connects to the buoy, and oil transfer starts. This system offers the quickest way to transport without costing much. In this article, I’ve explained how SPM works in three easy-to-understand steps.