4c_3_Other

Sub Sea as opposed to Topside.
In 4c Process Offshore we discussed Process and the Scope as defined for Topsides i.e. from Well Delivery to export to shore with very little difference to the Products (Oil and Gas) chemical composition, most of this occurring Onshore once landed.
4c-3 Other (Sub Sea) has the same extent except it is segmentised in portions and only includes part of the Topsides Process. The more that can be undertaken sub sea the less of unwanted content has to be brought to the surface, in this respect it has economical benefits. There are some exceptions where some work must be done to leach the products from their Sub Sea Reservoir e.g. Mariner Project.

In this section 4c-3 Other, the emphasis is on Sub Sea where a modification to 4c - Process definition has some exceptions. The process limits Sub Sea are limited on those quoted in 4c since only certain systems can be operated (to date) at depths and conditions below sea level. If this were not the case, then in deepwater away from shore all that can be located on a Topsides might, by choice be Sub Sea. The equipment / machines to accomplish this are hybrid, must have mixed capability e g capable of mixed phase pumping and compression. These operations are restricted, to mainly boost the capability to reach a Jacket or Floater before meeting up with other flows to be pumped to shore.

The WIV shown in the Diagrams and Picture is the basic Work Horse used to service and workover Sub Sea Installations.
The WIV 1 Data Sheet indicates some of its capabilities. These include Tree Installation, Diver and ROV Intervention via Moon Pools.
WIV 2 Ops DS illustrates Well Workover using Coiled Tubing through Trees with Dry and Slick Line,

In 4c Process, 4c_1, Varg and 4c_2, Clair we use those topsides to elaborate the problems to finalise modules and standardize modules. In "Other"we discus items that are Sub Sea and the subject of Modularisation.

Workhorse for Sub Sea The work horse to service these subsea installations is a variation of an AHT (Anchor Handling ) refereed to as a WIV ( W I Vessel) Such a vessel shown in the Data Sheet is equipped with Moon Pools, Diver Support units, ROV ( R O Vessel). Wire line (Dry , Slick) Coiled tubing capability, work over lifting capability with pillar and gantry cranes (Stern Portal ) to interface with subsea items and the multitude of subsea requirements they present.

Usually whatever goes on Sub Sea the emphasis is to use a Modular approach. The reasons for this are many. Firstly whatever is located subsea needs to be get-attable to allow it to be brought to the surface. Secondly, backup or replacement needs to be easily achievable. Because of the complexity of the machines used, there needs to be some logic to there unitization. The illustration shows a typical Sub Sea Development.