Description of the Export Loading System

This section will commence with a description of the loading system in Kuwait Oil Company (KOC), which will be the subject of this study.

The parameters used during the design stage will be applied or re-evaluated to provide a good estimation of the variables to be used in the numerical modelling. Also, the irrelevant boundary conditions of the field system will be presented. Recently, Kuwait Oil Company (KOC) has upgraded its export facilities by completing a mega project that has enhanced the export capability to handle a 3MMBLS daily production rate. This project included the Crude Export Facilities at

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North Tank Farm, South Tank Farm, and North Pier Pumping & Metering station (NPP&MS) project. Hyundai Heavy Industries Co. LTD (HHI) constructed this project between 2006 and 2009. A part of the Kuwait Oil Export facilities will form the real field system in the current work.

Figure 5-1: Export Facilities Overview.

It consists of floating roof tanks, pipelines of different lengths and diameters, and interior manifolds which contain conjunction headers with different valves. This gives the system flexibility in operation, to convert the flow to the correct destination, at the right flow rate, depending on the final export destination or which pipeline is being used. In Figure 5-1 the tank farms, pipelines, the North Pier Port and Metering Skid (NPPMS), and the Catenary Anchor Leg Mooring (CALM) buoy are presented in yellow circles with number, 620, 651,612 and 619, respectively. The study part of this research starts from the pump at NPP&MS, the submarine crude line, and the CALM Buoy. As illustrated in the figure, the export facilities consist of three identical CALM Buoys, the only difference in the submarine pipe length. The location of the Kuwait Oil Export facilities is shown in Figure 5-1.

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The system to be studied is explained in Figure 5-2. Also, the manifolds are shown in Figure 5-2 in the dashed squares numbered 3 and 5. In addition, in these manifolds, the pipes rise up to connect the headers pipes and then continue downward to go underground again. It should be noted that most of the pipelines are underground or on the sea bed.

Depending on the desired flow rate, the vessel at the Catenary Anchor Leg Mooring (CALM) Buoy (9) is fed either by gravity or by pumping loading. The number of tanks used to supply the crude is dependent on different factors: operational reasons, the required flow rate and the minimum suction pressure.

The elevation between the sea level and the tank bottom approximately is 111m (varies between one tank and another).

It is clear that there are many components of the systems to consider in the numerical modelling. The valves, headers which require changing in topology of the line and the cross-sectional pipes, affect the flow and cause many pressure drops in the system. Also the valves’ operational performance (complete isolation or partial flow) are a source of uncertainty and hence difficult to model. By neglecting all of the foregoing, it can be assumed that the system components operate perfectly; however, the system still has many temperature and pressure relief valves for safety purposes. Hence, to avoid the uncertainties and the malfunctions of the components, and also to simplify the modelling, the part of the system that will be considered is downstream of the pump where there is discharge and the metering skid stream pressure transmitters up to the CALM buoy.

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Figure 5-2: Schematic of the loading system components from Tank to CALM Buoy. The information in Figure 5-2 is explained in details in the following table.

No. Description Dimensions

Note Diameter

(in) Length (Km)

1 Tank # #

2 Pipe line 36-48 1.3-0.6 Variation in dimensions

depend on the pipeline used for loading.

3 Manifold 40, 42 &

48 0.3

4 Pipe line 40/38, 48 8 Some pipelines have

changing cross-sectional area. 5 Manifold 6 Pipeline 48 0.5 7 Metering & Pump station 60 0.3 8 Submarine

Pipeline 56 15,18 & 22 CALM Buoy no. 23, 24 & 20

9 CALM Buoy

Table 5-1: Components shown in Figure 5-2 with further details.

!12 2 2 2 2 9 Sea Level 1 2 3 4 5 6 7 8 Sea Bed

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The section of the distribution system to be studied is shown in Figure 5-3.

Figure 5-3: Schematic submarine line elevation of the downstream of the pump up to the CALM buoy.

The advantages of limiting the study section can be summarised as follows:

1- It avoids any malfunction of the components like a valve not closing fully, which would affect the numerical modelling. It is better in terms of leak detection to avoid these system components [43].

2- There are three almost similar submarine lines with different lengths, of 15, 18 and 22 km which gives the opportunity to check the validity of the numerical technique if applied.

Finally, the details of the CALM buoy components are shown in Figure 5-4. At the last point of the submarine pipeline, it divides into two hoses each containing a valve which is known as the Pipe Line End Manifold (PLEM) valve. These valves close within 5 seconds in case of an emergency such as a leak from the ship or a hose, or if the pressure becomes greater than 9 𝑏𝑎𝑟𝑔 in the PLEM [121]. This is one of the major causes of the water hammer phenomena in the system. In reality and for safety reasons, the functionality of the signal is checked routinely without operating the valves. However, the staff have been instructed to collect data on any occasions

Length 15 Km

Diameter 56’’ (1.4224 m) Submarine Pipeline (8)

PLEM valve

CALM BUOY 9 Pressure

Transmitter (7)

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of surge behaviour during emergency shutdowns. This rarely happens during loading for any doubtful circumferences.

The KOC has four CALM Buoys and as mentioned earlier, three of them are almost identical in components and specifications, except for the pipelines’ length. These length variations are shown in item no. 8 in Table 5-1. The pipelines start from the same shore location, and different vessels can be anchored simultaneously. Referring to Figure 5-4, at the end of the submarine pipeline there are two PLEM valves linked to different hoses connected to a swivel joint. From the swivel joint two floating hoses are connected to the vessel with the CALM buoy to export oil. The swivel joint preserves the flexibility of movements of the loading; this is vital when the vessel is moving due to winds or sea currents.

Figure 5-4: CALM Buoy Components