Case History

Subsea Flexible Pipelines

Overview

There were extensive sections of flexible pipelines in an offshore oilfield that required to be replaced/reconfigured. Prior to the operation, these sections needed to be degassed, filled with either an environmental barrier or treated seawater. Once replaced/reconfigured, the lines then required to be leak tested and dewatered before being brought back into service.

Working closely with the client from the planning stage, SANCCUS came up with the solution which combines the use of Pipeline Gels and Gel Pigs to achieve the desired result efficiently.

Solution

Oilfield Overview

Structures

The pipelines are running across 3 rigs in the field and connected through Subsea Isolation Valves (SSIV). From left to right - Rig 1, Rig 2 and Rig 3. Rig 1 was expected to be decommissioned in near future.


Rig1-Rig2-Overview

Rig 1 & Rig 2

Part of the lines between Rig 1 and Rig 2 had a requirement for an environmental barrier as well as degassing.


Degassing

Step 1

Treated seawater was pumped in from the Diver Support Vessel (DSV) through SSIV to Rig 1.


Barrier

Step 2

Glycostat Gel was injected from DSV to push treated seawater further to degass and also to form a barrier.


Degassing

Step 3

Functioning SSIV valves, Gel was injected from DSV up to Tee piece.


Degassing

Step 4

DSV connected its downline to Tee and started pumping Gel towards Rig 2, degassing the lines as it's pushed by treated seawater.


Phase1 Complete

Step 5

The lines between Rig 1 and Rig 2 ready for subsequent operations.


Rig1-Rig2-Overview

Rig 2 & Rig 3

DSV moved on to the area between Rig 2 & Rig 3.


Degassing

Step 6

DSV pumped in Glycostat Gel through SSIV to Rig 2, degassing as it's propelled by treated seawater.


Degassing

Step 7

Repeat the same sequence on the line between SSIV and Rig 3.


Degassing

Step 8

The line between Rig 2 and SSIV was disconnected and new line was installed to replace this section. The line from Rig 1 was blanked off with a flange.


M-Gel

Step 9

M-Gel Pig was introduced to SSIV by a diver.


Leak Test

Step 10

Triethylene Glycol was injected from DSV for the leak test.


Dewatering

Step 11

Propelled by nitrogen gas, M-Gel Pig was driven towards Rig 2, dewatering the line.


End

Step 12

The same method was employed to replace, test and dewater the line between SSIV and Rig 3. The lines between Rig 2 and Rig 3 ready to be back online.

Result

Glycostat Gel ensured the effective degassing as well as the provision of environmental barrier for future operations. M-Gel Pig successfully negotiated through flexible lines which had corrugated internal surface without any problem.

Value

Extensive lengths of flexible pipeline were effectively replaced/reconfigured without compromising diver safety and environmental responsibility.

The versatility of SANCCUS Gel enabled the fulfilment of three purposes - degassing, environmental barrier and dewatering. By simplifying the application, it helped save both time and cost.

GET IN TOUCH

We know from years of experience that no two jobs are identical. We will work closely with you to provide the appropriate gel and/or gel pig combined with reliable technical advice and support to give you the best possible outcome. Get in touch with us for a tailored information pack.

CONTACT


SANCCUS Limited
Units 3 & 4
Colpy Way
Colpy Road Industrial Estate
Oldmeldrum AB51 0BZ
Scotland, UK

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