This paper describes key findings from Phase 1 of the Deepwater Installation of Subsea Hardware (DISH) JIP. The objective of DISH Phase 1 was to identify key gaps in the offshore industry's technology for installing subsea hardware in water depths beyond 2,000m, by comparing present-day capabilities of the installation industry with likely deepwater installation requirements of oil and gas operators over the next 10 years. Technology gaps were identified by interviewing engineering and installation contractors, oil and gas operators and specialist suppliers; by carrying out a literature review study; and by holding a Phase 1 Mid-Flight Workshop to identify and prioritise the key gaps. The results were further refined before finalising the Phase 2 work programme. A review of the capabilities of wire rope lifting systems showed that self-weight will make conventional wire rope systems inefficient for water depths in the range 2,000m to 3,500m, and impractical on most installation vessels. The industry will therefore have to turn increasingly to deepwater fibre rope deployment systems. Key challenges are to establish the industry's confidence in fibre rope deployment systems, and to provide key information about the engineering properties of man-made fibre ropes and of the loading on such systems. Lack of knowledge of fibre rope behaviour was considered to be a fundamental, show stopper', which will inhibit the adoption of fibre rope deployment systems for ultra-deep water installation. DISH Phase 1 is now completed, and Phase 2 was launched in January 2002, based on the priority technology gaps and challenges identified during Phase 1. Background The DISH JIP was instigated following a pan-industry Workshop held in November 2000. At that time hydrocarbon developments were being planned in water depths close to 2,000m, and deeper fields were already being considered. Speakers from major installation contractors and BP believed, however, that established techniques for lowering and installing heavy items on the sea floor may either prove impractical or uneconomic in water depths beyond 2,000m, such as in emerging areas of the Gulf of Mexico. Furthermore, the deepest fields so far developed have been in relatively benign ocean environments, and the installation methods used to date are not necessarily transferable to harsher environments. A number of technical advances will therefore be needed to make some deepwater developments economic and practical. These issues were discussed further in a paper presented at a SNAME Workshop in February 2001 [1], which summarised possible technology gaps in the areas of lifting and lowering technology, load control and positioning, metocean effects and weather window requirements. General Approach DISH Phase 1 aimed to identify key technology gaps by comparing present-day capabilities of the installation industry with likely deepwater installation requirements of oil and gas operators over the next 10 years. The goal of achieving a common understanding spanning operators, contractors and suppliers worldwide, across the whole industry, was considered to be particularly important.
Challenges face the geotechnical engineer in the ACG Field in the Caspian Sea, from data acquisition, through soil characterization, to foundation design and installation. This paper seeks to address some of these challenges and describes some case examples from the authors' experiences, particularly in the treatment of geohazards and their threat to foundation integrity.Limited guidance exists within industry codes and standards to address the interaction of geohazards with jackets and with subsea infrastructure. As such, quantified risk assessment becomes complex. This paper suggests some solutions to these problems, borne out of more than 20 years' operating experience in the Production Sharing Agreement (PSA) and the need to consider development in some of the more geohazardous areas.Unusual methods of geotechnical data acquisition are presented along with tools and novel analytical techniques specific to the needs of Caspian soils. Finally, the paper presents some approaches to quantify the impact of geohazards, including the influence of unusual soil conditions as they present themselves today.
As oil and gas developments move into deeper waters, potential exposure to geohazards becomes an important project risk driver. Landslide deposits and features observed on the seabed in the vicinity of potential future development indicate processes that were active in the geological past and can be expected to continue in the future. Rapid yet spatially extensive analysis of landslide risk is a key requirement of the geohazard assessment for many oil and gas developments, with an aim to provide an estimate of the annual probability of slope failure across the entire proposed development area as an input to the QRA. Well‐established methods exist for probabilistic assessment of slope stability through GIS‐based application of a limit equilibrium infinite slope geomechanical model. Shear band propagation is an effective mechanism to explain large landslides observed in the sediment record that cannot be explained through limit equilibrium alone. A novel GIS‐based probabilistic slope stability assessment using SBP approach allows for improved pixel‐based estimates of the annual probability of failure for a variety of observed landslide mechanisms, such as slab, spreading, ploughing and run‐out failures. This GIS‐based tool has been successfully employed as part of a landslide risk assessment of the ACG development, Caspian Sea, contributing to a landslide risk score for each geohazard province within the area.
Concept stage site assessments based on exploration 3D seismic data and other existing information are critical elements in the deepwater field development sequence. Such assessments help create value by defining site conditions and geohazards that may eventually constrain development, which in turn allows risks to be properly evaluated before significant development decisions are made. Several decades of deepwater development consulting experience, however, have shown that-despite their great valueconcept stage site assessments are often not undertaken because 1) decision makers do not know that the assessments should or could be performed, or 2) there is a misconception that money can be saved by skipping steps or executing steps out of sequence in order to fast-track a development. As shown by way of two examples, decisions not to perform concept stage site assessments-even in cases where the necessary data are already available and free of additional cost-can be expensive mistakes that result in project delays if surveys have to be repeated or field layouts changed. In other words, human decision makers become significant and-unlike those associated with geohazards-largely indefinable elements of risk if short-term savings accrued by doing it wrong the first time are prioritized while the potentially more significant costs of having to do it right the second time are marginalized.
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