Deepwater Gas Fields: a Review of Current Field Development Options, Enabling Technologies and Main Challenges

摘要

Large, and sometimes very large, gas discoveries in deep and ultra deep waters have occurred over the past years in different geographic areas across the world. Some of these discoveries are being developed at present using 'Subsea to Beach', floating LNG or other options that require combinations of subsea tie-backs and offshore host(s). The choice on how to develop one or more deepwater gas reservoirs depends both on technical factors, including the readiness level and the applicability ranges of some key enabling technologies, and on non-technical factors, such as geopolitics considerations, market conditions and risks. This paper presents the most frequently encountered field development options and discusses their advantages and disadvantages. Examples of real projects are also presented, making use of public domain information when available. Scientific literature has been searched to collect information on past and ongoing projects. Press releases and other sources have been investigated to double-check and ensure consistency of the gathered information. The key technologies considered 'true enablers' for this kind of project are presented and briefly discussed. More focus is given to the readiness level of these technologies and to their current applicability range. For 'subsea to beach' this range is perceived to be within 200km from the shore and up to 1,500m water depth. Recent projects are understood to push the water depth limit up to 2,500m, while it might be more difficult to extend the step-out distance from shore beyond the 200km limit. New technologies are also discussed as possible future enablers. Non-technical factors are then studied due to the fact that some of the challenges that can be encountered in developing large offshore gas reservoirs are not technical in nature. Examples of these risks are delays in the project schedule and overall cost overruns. These non-technical challenges need to be taken into account while selecting the proper development option.