Current Trends and Future Technologies for the Decommissioning of Offshore Platforms
Authors: Thornton Win , Wiseman James 
Published: October 2008

This paper will provide an overview of the decommissioning process and identify the resources required for project implementation. The results of the 1999 work season will be reviewed and analyzed to identify current trends and provide fact or fiction assessments of prevailing perceptions about decommissioning. The information utilized in preparing this paper was gathered from a variety of sources including owner, contractor, project manager and regulatory agencies. The decommissioning process includes tasks for engineering (planning, permitting, project management), preparation (well P&A, topsides preparation, pipeline decommissioning), removal (severing, platform) and disposal (reuse, reef or recycle). Removal technologies utilized included severing (explosives, abrasive water jet, mechanical cutter, diamond wire cutter and torch cutting), heavy lifting and handling. Disposal solutions implemented included reuse of the platform (equipment, deck and/or jacket), Rigs-to-Reefs and onshore scrapping/recycling. This paper will also outline the decommissioning challenges faced in the 1999 Gulf of Mexico work season and offer a list of future challenges facing our industry.

Background

The first recorded platform removal in the Gulf of Mexico Outer Continental Shelf (OCS) was in 1973. Since then, over 1,800 removals in the OCS have been recorded through the end of 1999. In recent years, removals have exceeded 100 platforms per year. This trend is expected to continue since one-fourth of the 3,800 OCS platforms have been in place for more than 25 years. In the decade of the 1990's, the number of removals has outpaced the number of new platforms installed for three different years.

In the past, the oil and gas industry has called the platform removal process "abandonment". Rather than simply walking away from the platform as the term suggests, the oil and gas operator (owner/operator and working interest parties) is legally bound to properly remove their platform and return the site back to its predevelopment condition. In lieu of "abandonment", industry has collectively shifted to utilizing the term "decommissioning" to identify the platform removal process. To date, the oil and gas industry has responsibly performed its decommissioning obligation, having removed in excess of 1,800 platforms in the Gulf of Mexico.

The types of structures that have been decommissioned in the Gulf of Mexico can be categorized as major platforms (multilegged steel template structures as detailed in Figure 1) and minor platforms (single well caissons and multi-legged well protectors and minimal platforms).

Overview of the Decommissioning Process

The decommissioning process as practiced in the Gulf of Mexico can be broken down into four major task groups. Depending on timing restrictions, the configuration of the platform and operator preferences, many of the tasks can be performed concurrently. Some tasks can even overlap. Therefore the decommissioning process for any given platform may vary, but should still consist of the following basic activities.

Engineering.

The engineering tasks include planning, permitting, engineering and project management activities.

Preparation.

The preparation tasks include all activities required to make the platform ready for removal by the derrick barge. The preparation activities include well P&A, topsides equipment preparation and pipeline decommissioning.