Abstract

A study was conducted in November 2000 for the United States Department of Interior, Minerals Management Service (MMS) to identify and review state-of-the-art technologies for removing large offshore platforms located in deep water. Platforms emphasized on in this report were located in the Pacific Outer Continental Shelf Region (POCSR); comparisons were made to similar Gulf of Mexico platforms.

For this study, deepwater platforms were defined as those with jacket weights exceeding 10,000 short tons located in water depths exceeding 400 feet.

Three POCSR platforms (Hidalgo, Gail and Harmony) were selected to encompass the range of decommissioning conditions and to provide a thorough review of issues related to removing deepwater offshore structures. The water depths considered range from 430 feet to 1,198 feet.

Specific areas of technology reviewed included lifting, transportation, disposal, and explosive and non-explosive severing techniques. The three removal methods evaluated (using the best technology currently available) were Complete Removal, Partial Removal (reefing in place) and Remote Reefing (reefing off site).

Decommissioning cost estimates were prepared for the selected platforms and removal methods, including an evaluation of cost sensitivity (risk) issues and the cost of alternative technologies. Also assessed were environmental and human safety risks for current and evolving decommissioning technology. Specific recommendations were provided for industry and federal/state support for future developments.

Introduction

The overall goal of the MMS study was to determine and examine the issues relevant to decommissioning deepwater platforms and to quantify them in the context of economics, risk, and available technology. The following specific goals were achieved in this study:

  1. Develop decommissioning plans for selected POCSR deepwater platforms using the best technology currently available.

  2. Prepare decommissioning cost estimates for selected platforms and cases, including an evaluation of cost sensitivity (risk) issues and the cost of alternative technologies (i.e., explosive versus non-explosive severing methods).

  3. Assess environmental and human safety risks for current and evolving decommissioning technology.

  4. Provide a review of the state-of-the-art in decommissioning technology for: lifting, transportation, and disposal; explosive and non-explosive severing techniques.

  5. Prepare specific recommendations for industry and federal/state support for future developments.

Scope of Work.

The scope of work for the study consisted of selecting platforms to be evaluated; selecting and evaluating removal technology; developing decommissioning plans and cost estimates; analyzing safety and environmental issues; and reviewing and describing other removal technologies, their current development status, and prospects.

Project Issues

Offshore platform decommissioning is a challenge under any circumstances in terms of planning and executing the work in an environmentally sensitive, safe, and economical way. Regarding large deepwater platforms in the POCSR, this is particularly true. Among the issues that must be faced are:

Lack of Local Infrastructure.

There are currently no derrick barges of significant capacity or other types of major marine construction equipment based on the West Coast, and none are likely to be in the foreseeable future. Additionally, there are currently no onshore facilities in California (or Mexico) capable of accepting jackets or topsides of these sizes, even in small pieces.

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