# Multi-Hop Routing Protocols for Oil Pipeline Leak Detection Systems
## 1 Introduction  
Pipelines are cost-effective; clean in transporting water, oil, or gas; and provide greater supply rates and capacity. There are different pipelines in terms of topology, design, fluid type, and operational condition. The pipe may carry water, gas, or oil. Some pipelines are underground, and others are aboveground [1]. Considering the length of the pipelines and the state of the terrain, many problems can occur, such as pipeline leakage and corrosion [2]. A leak in oil and gas pipelines causes extreme environmental pollution and economic losses. Hence, the need for pipeline monitoring and leak detection systems is immense.  
A Wireless Sensor Network (WSN) is suitable for monitoring the pipeline to provide leakage detection and has many advantages. Wireless sensors can cover the area where there are no wired connections, and sensors are low in cost and easy to deploy and maintain, which increases network reliability and security [2]. There are many challenges in using WSNs in oil and gas pipelines, such as minimizing energy consumption, avoiding congestion in large-scale networks, and dealing with the constraints imposed by the linear topologies [2]. Sensors consume energy during their long duty cycle. A massive number of sensors leads to huge energy consumption that affects network lifetime and reliability. Thenetwork congestion leads to delay, packet loss, and high load. When the number of packets increases the network throughput decreases. In a linear topology, the sensors are deployed in a linear formation. Such linear topologies impose challenges, such as long-distance, high-energy consumption, long delay, and low reliability [2]. Multi-hop communication is used in linear topologies, so the packets are sent from the source node to the destination node through other nodes that act as relay nodes [2].  
This study includes problem specifications from the public information available on oil pipelines deployed in Saudi Arabia. This will give a sense of the unique nature of leak detection, such as the pipeline measurements and the kind of area it may pass through.  
Crude oil and gas pipelines are above ground and run across Saudi Arabia from the east coast to the west coast [3]. It is a twin pipeline; one part runs from the city of Abqaid to the city of Yanbu, and the other from the city of Al Juhail to the city of Yanbu. The length of the pipe reaches up to 1200 km, and its diameter reaches up to 56 inches. It is deployed along an area that has desert characteristics [3].  
A leak in an oil or gas pipeline leads to different temperature values along the pipe and changes the pressure. There are several methods to detect the leak, which are classified as external and internal techniques [3]. External techniques detect a leak from outside the pipe, such as periodic walk-through and vapor detection. Internal techniques can detect the leak from inside the pipe by measuring flow, pressure, and temperature. Internal techniques are useful in the long-range system and have lower costs [3]. Different sensors can detect the leak, such as pressure sensors, temperature sensors, flow sensors, negative pressure wave sensors, and acoustic sensors [4].