Abstract
Thailand's oil and gas industry has been successful in finding and recovering hydrocarbon reserves in the Gulf of Thailand since last three decades and have currently installed over 200 fixed offshore structures. Some of these installations are now reaching the end of their economic productive lives and will need to be decommissioned soon. There are complex issues in terms of legislation, environment, safety, costs, technical feasibility and public acceptability. This paper describes the issues relevant to decommissioning in Thailand and proposes appropriate decommissioning solutions developed over the past few years.

The proposed decommissioning solutions are intended to support Thailand's oil and gas industry and its regulators in ensuring compliance with international decommissioning guidelines, balancing economics, safety, practicality and technical feasibility of operations with the environmental benefits and also satisfying needs of the key decommissioning stakeholders in Thailand so as to achieve conflict-free process of decommissioning.

Technical aspects of offshore removal process primarily relates to the lifting of modules and sub-sea structural cutting methods. Lifting techniques range from conventional crane barges used in installation to specialized decommissioning vessels. Basically cost, technical feasibility and safety are major drivers in selection of appropriate lifting method. Sub-sea cutting include explosives and cold cutting techniques, for which cost and environment are the major decision making factors. Environmental aspects of decommissioning can be categorized into short term and long term. Short term environmental impacts are primarily related to the decommissioning methodology whereas the long term environmental impacts are related to the chosen disposal scenario i.e., final destination of each component of an offshore facility. Key recommendations regarding environmental solutions are in the form of Best Practicable Environmental Option (BPEO) framework, which helps determining balanced disposal scenario as well as suitable decommissioning methodology.
Increased energy demands have currently resulted in rapid growth of number of offshore installations in the Gulf of Thailand. At the same time, the old disused installations need to be timely and appropriately decommissioned, which is not possible without having acceptable decommissioning solutions in hand. Such solutions need to be in compliance with applicable international decommissioning guidelines while adopting best practical environmental option hence assuring conflict-free decommissioning process. Therefore, development of such decommissioning solution are significant in assuring "RESPONSIBLE PERFORMANCE: TO DO THE BEST WE CAN" in order to help attain sustainable benefits for further development of Thailand's oil and gas industry.

Introduction
The Petroleum industry has brought enormous benefits to society. Petroleum reserves located under the seabed have resulted in the development of offshore structures (facilities) throughout the world. At the end of their economic production lives, these installations are required to be decommissioned to ensure safety of navigation and to protect the rights of other users of the sea. Offshore facilities decommissioning raises many complex issues in terms of environment, safety, technology and economics.

The industry has tried to develop and implement decommissioning strategies such that these issues are balanced. After 1995 the issue of decommissioning received global media attention with the successful disruption of plans to decommission the Brent Spar in the North Sea. This indicates the level of public interest and concern for the environment. The issue of public acceptability is therefore considered as an important factor in preparing decommissioning strategies. Currently, Thailand's oil and gas industry must face this challenge as some of the offshore installations in the Gulf of Thailand are reaching the end of their economic production lives.

Thailand oil and gas industry has been established for over 25 years and has been successful in finding and developing the natural resources that have helped the economic and social development of the Kingdom. Presently there are over two hundred fixed installations in the Gulf of Thailand and some of them are reaching the end of their economic production lives. The regulators are seriously taking up measures in order to develop guidelines that can ensure a balanced approach for decommissioning in terms of technical, environmental, legal and financial aspects of decommissioning. Thailand has previously encountered conflict situations in infrastructure projects and moreover, international disputes on decommissioning have emphasized the need of considering public opinion properly to avoid any conflict in decommissioning projects. Thailand industry regulators have a clear message to incorporate the public opinion into the decommissioning process. Therefore, efforts have been initiated for the development of decommissioning guidelines that can include the requirements of the stakeholders in order to avoid any subsequent conflicts in the oil and gas facilities decommissioning projects.

The United Kingdom Continental Shelf (UKCS) is a very mature hydrocarbon basin, and it is currently beginning to experience the full complexity associated with decommissioning. The UKCS region is also subjected to what most would acknowledge is the most developed set of regional arrangements in the shape of Convention for the Protection of the Marine Environment of the North-East Atlantic (OSPAR).

Notwithstanding the degree of regional agreement in relation to decommissioning, an emergent insight from the current study in the UKCS is that there are significant issues that remain unresolved, which can be categorized into four main categories:

Uncertainties of Regulatory Responsibilities

This finding has implications for other parts of the world that will have to face the challenges of decommissioning in the coming years, especially where they have not yet developed regional arrangements. Perhaps most challenging in this last regard will be the South China Sea given its history of contested island and maritime claims among several sovereign states within the region (Buszynski 2012).

In comparison with the North Sea, the geographical make-up of the South China Sea is much more complicated and there are many more countries sharing maritime borders in the region, making these potential offshore decommissioning issues more likely to occur. It is thus important for a regional offshore decommissioning agreement to be in placed in the South China Sea region to act both as a guideline and a dispute resolution mechanism in an event that disputes were to occur during offshore decommissioning operations.

This paper will highlight the 4 emerging areas of concern (as mentioned above) in offshore decommissioning in the UKCS to suggests that the countries in the South China Sea region could usefully have these in mind as they move to develop regional decommissioning arrangements. Primary qualitative data obtained from the semi-structured interviews will be used in this paper to highlight the concerns on offshore decommissioning in the UKCS while secondary data and literature will be used to link the 2 regions together to demonstrate the need for a consideration of a development of a regional decommissioning agreement in the South China Sea region.

Lee Allford (Energy Institute) It is estimated that more than 120 platforms with a combined weight of more than 1 million tonnes will be decommissioned over the next 10 years in the North Sea alone. This will involve a significant number of personnel engaged offshore in potentially hazardous operations during the removal of these facilities, underlining the need for ensuring high standards of process safety within the associated decommissioning projects. The need for effective management of process safety during decommissioning was highlighted in the major structural collapse incident at the Didcot power station in the UK in 2016 that resulted in 4 fatalities. This together with the fact that the police and HSE are conducting a joint investigation to consider corporate manslaughter, gross negligence manslaughter and health and safety offences, highlights the gravity of getting it wrong. With support from the Energy Institute and cross-industry involvement from oil companies, contracting companies and the UK Safety Regulator, new guidance has been developed that will support those engaged in decommissioning offshore facilities to plan, design and execute their projects so as to manage risk from major accident hazards (Energy Institute, 2019). This paper presents the key elements of this guidance which provides a roadmap to managing process safety across the lifecycle of a decommissioning project, from initiation through execution. The guidance is set-out according to typical phases of a decommissioning project, providing useful insights into key process safety considerations, objectives, tasks and outputs.

A study was conducted in November platforms in the POCSR, the contractors who operate large heavylift 2000 for the U.S. Dept. of challenge is particularly difficult. Platforms - Limited equipment availability. of the large HLV's have relatively little emphasized in this report were in - Environmental regulations. Method Selection Selected Platforms Figure 1 shows a decommissioning The three platforms selected to cover Introduction decision tree that identifies all the the range of issues discussed in this The goal of the MMS study was to decommissioning methods included report are Hidalgo, Gail, and Harmony. In all cases, topsides These platforms encompass the wide to decommissioning deepwater with oil and gas processing equipment range of decommissioning options platforms and to quantify them in the were taken to shore and available and provide a thorough context of economics, risk, and available scrapped. The three methods for jacket review of issues related to decommissioning technology.

A recent World Bank survey of oil producing countries suggests that governments around the world have a limited capacity to plan environmental, health, safety and socioeconomic issues associated with the end of a project's life. At the same time, global projections indicate a steep increase in decommissioning of oil fields in the next two decades. Consequently, since early 2009, the World Bank has been leading an Initiative, "Towards Sustainable Decommissioning and Closure of Oil Fields [and Mines] 2: A Toolkit to Assist Government Agencies,?? to contribute to sustainable development by assisting governments in resource-rich countries in undertaking earlier and more systematic planning of the decommissioning and closure phase of upstream (onshore and offshore) oil and gas production operations.

The World Bank worked with representatives of oil and gas sector companies, regulatory agencies, industry organizations, non government organizations, as well as experts and other stakeholders to generate consensus on key issues and to lead the development of a Toolkit containing high level, simple and user-friendly guidance designed to contribute to an increased level of awareness and understanding of decommissioning and closure among government authorities' staff in resource rich countries. The Initiative is funded under the environmental pillar of the Petroleum and Governance Initiative, collaboration between the World Bank and the Government of Norway.

An initial Issues Paper and input received during a workshop in April 2009 indicated that priority issues which needed to be addressed included: the need for increased government capacity and involvement; the absence of a regulatory framework related to decommissioning and closure, cleanup standards and environmental best practice, and enforcement and monitoring; as well as the need to mainstream financial assurance, include socioeconomic considerations in planning the closure and post closure phase of operations, and stakeholder engagement throughout the Project's lifecycle. A draft Toolkit was developed incorporating guidance on these issues and shared with a small but diverse group of stakeholders in London and then with government representatives during a World Bank event in Ghana. A revised Toolkit was then prepared and can be accessed at http://go.worldbank.org/PLYX4SKSB0. This paper highlights the collaborative approach that the World Bank undertook as part of this work and describes key outputs, including the Toolkit and its contents. The approach used and guidance developed may be of interest to governments and private sector companies in context of planning and/or implementing sustainable decommissioning and closure schemes.