Simulation and study of location and size of one-way channel buffers for large marine crude oil terminals

Abstract

The critical bottleneck affecting a terminal's oil throughput capacity is shifting from the limited number of berths to the channel connecting the berths to the anchorage area. This is especially true for the terminals with a oneway channel where large oil tankers can navigate through the channel only at high tides. Buffers can be installed at those terminals to significantly improve the one-way channel's capacity. This paper examines the buffer's location and size choices for a crude oil terminal with a one-way channel. A discrete-event simulator in-house was developed using Python to explicitly and model the buffer's location and size choices. The simulator accounts for a sufficient level of realism, including the tidal time windows for large tankers and the daytime operation constraints. Taking the Rizhao Shihua Oil Terminal of the Rizhao Port as the case study, this paper used the simulator to analyze the effects of various buffer locations and sizes on the port capacity and service level under two priority rules. They are the conventional "first come, first served (FCFS)" rule and a value priority (VP) rule that prioritizes the tankers with higher holding values. The results show that the VP rule can improve the terminal's capacity by up to 2.35% compared to the FCFS rule. The capacity increases as the buffer moves from the anchorage side to the dockyard side of the channel. The resulting improvement is up to 7.56%. Moreover, a one-way channel accompanied with a dockyard-side buffer holding one tanker only can attain 91.54% of the capacity of a two-way channel, manifesting the great potential of buffers. 影响我国原油接卸港区通过能力的瓶颈正从泊位数量不足向航道通过能力制约转移，尤以大型油轮需要乘潮进港的单线航道为甚。本文以尚未被深入讨论过的原油接卸港区长距离单线航道建设港湾式避让区的选址和规模为研究对象，在对避让区尺度表征的基础上，采用离散事件系统仿真方法，选择Python 编程语言构建仿真平台；以日照实华原油接卸港区(Rizhao Shihua Oil Terminal, RSOT)为案例，精细化设计相关作业模块，特别是潮汐和白天作业等混合时间窗口约束，通过求解港区服务台的服务时间和条件，分析避让区的选址、规模以及海事规则对于航道通过能力及服务水平等的影响，以明晰航道避让区的作用机制及机理。结果表明：“价值优先”的海事调度规则相较于传统的“先到先得”规则在一定程度上能提升港区的通过能力，最大通过能力提升可达2.35%；港湾式避让区的规模和选址与港区的最大通过能力分别呈正相关和部分相关；受限于原油港区特殊的安全规则，案例中，港湾式避让区选址越靠近港池侧，港区通过能力的提升越显著，与锚地侧相比，最大通过能力提升可达7.56%，且规模为仅能容纳1 艘油轮时，最大通过能力即可达到拓宽为双向航道时的91.54%，表现出良好的经济性。