Simulating offshore operations

When planning any offshore activity the possibility of adverse environmental conditions must be considered. Typically plans can be revised to incorporate engineering or temporal contingencies to provide insurance against a range of conditions, but at a price. Excessive expenditure on contingencies for very rare events may not be justifiable. In order to assess the options it is necessary to understand the implications for the offshore activities: simulation provides a basis for quantifying the impacts and thus determining the optimal investment in any contingencies.

Bowers JA (2001) Journal of the Operational Research Society  Vol.52, pp 135-142

New oil fields are being developed in deeper water where conventional production systems are impractical. One alternative is the floating production, storage and offloading system: oil is extracted and stored on a moored, floating tanker while a shuttle tanker transports the oil between the field and the refinery port. However, when the weather is too rough, mooring and offloading has to be suspended. If there is inadequate storage capacity, oil production also stops resulting in a costly interruption to the revenue flow. Simulation experiments with different design configurations can identify the economic optimum that minimises the financial impact of the weather on the operation. However, not all of the uncertainties can be captured completely in a quantitative manner and sensitivity analyses suggest that a more robust configuration is a better option than the simple optimum.

The floating production system:

Balancing the cost of contingency capacity and the cost of delays to production:

Mould GI (in press) Journal of the Operational Research Society

Emergency evacuation is a rare event in the offshore oil industry. Nonetheless, emergency procedures must be practiced routinely for the benefit of the work force and the emergency services. These practices typically take place in good weather conditions where there is little threat to those involved. However, in reality an emergency could occur in adverse weather conditions which can affect the capabilities of vessels and helicopters. This paper describes a study in which the data from various sources are synthesised in order to estimate the effectiveness of emergency evacuation and rescue systems in a stochastic environment. The study employed a discrete event simulation incorporating a model of the evacuation and rescue operations interfaced with a file of weather data. This approach provided a measure, the probability of completing the evacuation within N hours, for the comparison of alternative systems.

Weather risk in offshore projects

Bowers JA and Mould GI (1994) Journal of the Operational Research Society Vol.45, pp 409-419

Risk analysis tools have been used to help manage various projects. This paper describes a case study in which an extension to the stochastic project network model was developed for a risk analysis of an oil platform installation, quantifying the possible impact of the weather on the project's schedule. Examination of the weather data suggested the use of a Markov weather model combined with a separate residence time distribution for key states. The weather model was incorporated into the stochastic project network allowing the interactions of the various project uncertainties to be examined. While the weather introduced a significant additional risk to the project, analysis of management's options indicated that much of the risk might be avoided. In particular, the analysis quantified the benefits of scheduling the project start to take advantage of the seasonal variations and hiring heavy duty equipment to operate in more arduous conditions.