The deployment of Mobile Offshore Units (MOUs) involve many site specific considerations not directly considered in their design process. In order to account for all such site related factors a Site Specific Assessment (SSA) is performed for the MOU in its final operating configuration. The SSA serves as an input to the Location Approval document which confirms the rig suitability for the site and gives the necessary operational recommendations from the MWS concerning the entire rig move, verifying that risks are reduced to an acceptable level in accordance with best industry practice.
Jack-up deployments will have specific values of variable load, metocean conditions, soil conditions and air gap which vary from site to site. There are also transient loads that are intrinsic to site conditions such as: a) soil bearing capacity and sliding, b) punch-through or sudden penetration risks, c) leg loads when pulling out of deep penetrations, d) wave in deck loads when preloading at a draft, e) RPD due to scour, inclined seabed, buried channels, interaction with footprints from previous rigs, f) interaction with platform piles, g) pipelines, h) bottom hazards and obstructions, etc. The SSA considers the jack-up in its elevated condition and is conducted against storms with metocean parameters for given return periods and to calculation methods and safety factors prescribed in SNAME T&T 5-5A or ISO 19905-1. Seismic loads are also considered where necessary. Such standards also discuss the site surveys needed to mitigate any geohazards.
The deployment of moored units consider similar site specific factors with an emphasis on floating stability, air gap and the condition, installation and performance of mooring lines, connectors, anchors and on-rig equipment. The SSA is based on the calculation methods, safety factors and operational recommendations given in industry standards such as API RP 2SK, API RP 95F and POSMOOR.
We have experienced rig movers and engineers on staff as well as an extensive library of computer models in SACS and USFOS (for jack-ups) and GMOOR (for moored units) to provide a fast, accurate and cost effective SSA to our clients.