Development of Downtime Cost Calculator for Offloading Operations Influenced by Parametric Rolling

Abstract

The stability of FPSO or offloading shuttle tanker may be affected in wave conditions which excite parametric rolling. The offloading operations are thereby ceased and eventually leads to loss in production which affects the revenue of global production, better known as downtime cost. This paper discusses downtime cost analysis of offloading operations due to parametric rolling of shuttle tanker under regular waves in Malaysian waters for three different locations. The downtime due to parametric rolling is investigated for two different water depths for which the probability of occurrence was calculated from the location specific wave scatter diagram. The results of parametric rolling of shuttle tanker along with downtime cost charts are presented. Additionally, a Graphical User Interface (GUI) was developed and its work procedure is demonstrated in this paper. The down-time cost calculator will help the oil operator companies to analyze the economic risks involved for field developments and anticipate the loss in revenue for downtime occurrences. The developed GUI was copyrighted under literary work as intellectual property.

Dynamic roll instability of liquid natural gas carrier during offloading operations and prediction of downtime cost in Malaysian waters

“…The following equations for mathematical modeling are used to estimate parametric rolling when the wave crest touches the midship. 10 The longitudinal measurement of the vessel of interest is initially divided into sections. The investigation of parametric roll begins with calculation of draft (dc) for wave crest at midship, as given by equation ( 1), followed by calculation of transverse moment of inertia (Ix) at every wave crest position, as shown in equation ( 2).…”

“…Nonetheless, there are times when particular wave conditions are responsible for sudden rolling beyond acceptable limits, or impacted by severe wave kinematics, leading to extreme response and behavior of FPSO or shuttle tanker. 9,10 The risk of loss in revenue due to downtime is a serious concern for any field operator. Any delay in offloading operations by any reason is associated with production loss; and the impact on production loss or downtime cost can be high depending on the duration of downtime days.…”

“…Nonetheless, there are times when particular wave conditions are responsible for sudden rolling beyond acceptable limits, or impacted by severe wave kinematics, leading to extreme response and behavior of FPSO or shuttle tanker. 9,10…”

“…Catastrophic and unprecedented weather causes longitudinal waves with enormous destructive energy to hit vessels, which may lead to higher hydrodynamic response, thus causing hindrance to offloading process. 10,20,21 Thereby, excursion in motion or structure response may call off the offloading process. 22 This nonfeasible period of offloading process is termed as downtime.…”

“…8 The past studies have reported capsizing and overturning of container ships under extreme influence of parametric rolling. 10,23 Occurrence of intense rolling will affect sea operations. The offloading operations may also be ceased if parametric rolling is severe.…”