Volume: 4 | Issue: 2

Upstream Offshore-Facility Weight-Growth Study



Offshore-facility weight is significantly related to the cost, schedule, and complexity of offshore-facility projects. Therefore, controlling the weight growth of offshore facilities is important to project success. This paper seeks to understand weight growth and its causes among different project phases. By use of the detailed database of oil and gas projects provided by Independent Project Analysis, we conducted a rigorous statistical analysis of offshore- facility weight growth to identify the root cause(s). This paper evaluates the weight growth for 153 global offshore projects at the end of the concept selection and authorization gates. The study results show that industry weight growth is much higher than expected.

Front-end loading (FEL) is a core work process of project teams before authorization. FEL is a process to develop sufficient strategic information to address risk and make decisions to commit resources to maximize the chance of a successful project. The FEL work process is divided typically into phases or stages, with a pause for assessment and decision making about whether to process (Fig. 1). Although the industry typically allocates 13% of dry weight for weight contingency at the end of FEL 2 and 6% of dry weight at authorization to account for unexpected weight growth, one-half of the topsides had more than 10% weight growth from authorization to completion, and more than one in three substructures had more than 10% weight growth from authorization to completion. The data also show that estimated weight-contingency range is much narrower than that of actual required contingency. This analysis shows that the weight growth of most offshore facilities is caused by poor engineering status for the facilities at authorization. The analysis also shows that setting aggressive schedule targets erodes the benefits of good engineering definition. In general, projects with good engineering and aggressive schedule targets have an additional 9% weight growth compared with projects with good engineering and nonaggressive schedule targets. The weight growth of offshore facilities was found across many different offshore-facility concepts (e.g., fixed platforms, spars, tension-leg platforms). This research provides an understanding of industry offshore-facilities weight performance and the main causes of weight growth, and offers recommendations for improving weight predictability.


With new technological developments, high energy demand, and existing-oilfield depletion, there has been steady growth in the discovery of offshore resources. As a result, more offshore facilities will be installed to increase oil and gas production. Given the importance of offshore weight to offshore-facility success, understanding weight growth is critical to the petroleum industry.

On the basis of our analysis and observations of projects in the database provided by Independent Project Analysis (IPA), one-half of topsides have more than 10% weight growth from authorization to completion, and more than one in three substructures have more than 10% weight growth from authorization to completion. Meanwhile, estimated contingency has a much narrower range compared with actual required contingency.

To help the industry understand offshore-facility weight predictability, IPA recently conducted a comprehensive study that sheds new light on facility weight performance and identifies the root causes of weight growth, providing guidelines for improving predictability.

Read or download the full SPE paper 170696-PA.