LoRaWAN Range in Offshore Plug and Abandonment Use Cases

Abstract

This paper explores the viability of LoRaWAN (Long Range Wide Area Network) technology for critical communication needs in offshore Plug and Abandonment (P&A) operations. Given the increasing demand for efficient and environmentally sound decommissioning of aging offshore oil and gas assets, the study investigates LoRaWAN's potential as a cost-effective and low-power alternative to traditional communication methods. The research focuses specifically on evaluating LoRaWAN's communication range and performance in challenging marine environments, including its susceptibility to various obstructions, to determine it’s suitability for continuous monitoring in this demanding sector.

Abstract 2

1. Introduction 4

2. LoRaWAN Fundamentals 5

3. Test Set-Up architecture 7

4. Deployment Planning and Signal Measurement: 8

5. Tests 10

6. Test Results 17

Conclusion: Test Results vs Real World Results 18

1. Introduction

The global push for decarbonization and the increasing number of aging offshore oil and gas assets necessitate efficient and environmentally sound plug and abandonment (P&A) operations. P&A involves permanently sealing wells to prevent hydrocarbon leakage and decommissioning associated infrastructure. These operations are complex, costly, and require continuous monitoring to ensure safety and regulatory compliance. Traditional communication methods, such as satellite or dedicated fiber optic cables, can be expensive and logistically challenging for temporary or intermittent monitoring needs.

LoRaWAN (Long Range Wide Area Network) is a low-power, wide-area networking (LPWAN) protocol designed for wireless communication over long distances with minimal power consumption. Its characteristics make it an attractive candidate for various industrial IoT applications, including those in challenging environments. This paper investigates it’s potential for offshore P&A use cases, specifically focusing on the critical aspect of communication range. Understanding the range limitations and optimization strategies for LoRaWAN in a marine environment is crucial for its successful implementation in this demanding sector.

2. LoRaWAN Fundamentals

LoRaWAN is built upon LoRa (Long Range) physical layer modulation, a proprietary spread spectrum modulation technique derived from chirp spread spectrum (CSS) technology. Key features relevant to offshore P&A include:

• Long Range: LoRa signals can travel several kilometers in rural areas and several hundred meters in urban environments. In line-of-sight conditions, ranges can extend significantly further.
• Low Power Consumption: LoRa devices are designed to operate for years on small batteries, making them suitable for remote, inaccessible deployments.
• High Link Budget: LoRa's modulation provides a high link budget, meaning it can tolerate significant signal attenuation and still maintain connectivity. This is particularly important in environments with signal absorption and scattering.
• Scalability: A single LoRaWAN gateway can support thousands of end devices, enabling efficient network deployment.
• Open Standard: LoRaWAN is an open global standard maintained by the LoRa Alliance, fostering interoperability and a growing ecosystem.

The LoRaWAN architecture typically consists of end devices, gateways, a network server, and an application server. End devices transmit data to gateways, which then forward it to the network server. The network server handles routing, security, and deduplication before sending the data to the application server for processing and analysis.

3. Test set-up architecture

The system architecture involves a LoRaWAN pressure sensor transmitting to a LoRaWAN Gateway, connecting to a Rest API and a COMPANY Dashboard. The data flow begins with a pressure sensor transmitting data to the LoRaWAN Gateway. This gateway, specifically the Model MF-460-SERIAL-ATEX, is designed for use with IDP Satellite Terminals and LoRa EU868 Networks, featuring solar and battery backup and ATEX Zone 2 ratings for hazardous environments. The data then travels via an omnidirectional satellite terminal, leveraging the Viasat IsatData Pro service and Teleport, to a managed service that feeds into the MinFarm Rest API and ultimately the customer dashboard.

The LoRaWAN pressure sensors themselves are ATEX zone 1 certified, long-range, battery-powered, and designed for harsh environments. They have a measurement range of 400bar (5800psi) with 0.15% FS accuracy, stainless steel process material, and an aluminum-coated housing. They operate on the LoRaWAN EU868 frequency plan and comply with ATEX/IECEX/UKCA HAZLOC Gas/Dust safety standards.

4. Deployment Planning and Signal Measurement:

To assess the effectiveness of the LoRaWAN range, two key metrics are used:

• RSSI (Received Signal Strength Indicator): This measures the power of a received radio signal in dBm. A higher (less negative) RSSI indicates a stronger signal. For example, -30 dBm is strong, while -120 dBm is weak.

A measurement of how well a receiver can ‘hear’ a signal from a sender

- RSSI minimum = -120 dBm (1e-15 W)
- If RSSI = -30 dBm (1 uW): signal is strong
- If RSSI = -120 dBm (1e-15 W): signal is weak
- See the link budget (https://lora.readthedocs.io/en/latest/#id17):

• SNR (Signal-to-Noise Ratio): This is the ratio between the received signal power and the noise floor power level. LoRa technology is notable for its ability to operate below the noise level, with typical SNR values ranging from -20 dB to +10 dB.

Normally the noise floor is the physical limit of sensitivity, however LoRa works below the noise level

- Typical LoRa SNR values are between: -20 dB and +10 dB
- The minimum SNR values for different spreading factors (https://www.thethingsnetwork.org/docs/lorawan/rssi-and-snr/):

5. Tests

Two primary test scenarios were used to evaluate LoRaWAN range:

Test A: 9.2 km, Clear Line of Sight (LOS) and Obstacles (Offshore)

This test simulated an offshore environment across open water. The gateway was positioned at 1.5m height on a tripod with an elevation of 11.5m, while the sensor was at 1.5m height at sea level.

• Test A.1: 9.2 km, Clear LOS: This setup aimed to establish baseline performance with an unobstructed path between the gateway and sensor. While the document doesn't explicitly state the measured RSSI/SNR values for this sub-test, the implication is that it represents the optimal range for the given distance.
  
• Test A.2: 9.2 km, No uplinks behind steel plate: This sub-test introduced a significant obstacle (steel plate) between the sensor and gateway, resulting in no successful uplinks. This highlights the substantial impact of metallic obstructions on LoRaWAN signal propagation.
  
• Test A.3: 9.2 km, No uplinks behind metal cabin: Similar to the steel plate test, placing a metal cabin between the devices also prevented any successful uplinks, further emphasizing the challenge of signal penetration through metallic structures.
  

Test B: Inside Lab, Various Obstacles

This series of tests was conducted in a controlled lab environment, with distances ranging from 10m to 27m. Both the gateway and sensor were placed at 1.5m height on tripods.

• Test B.1: 10 m, Clear LOS: This served as an indoor baseline for a short distance with no obstructions.
  
• Test B.2: 10 m, Steel plate in front of sensor: This test examined the impact of a steel plate directly in front of the sensor.
  
• Test B.3: 22 m, Steel plate in front of gateway: This test assessed the effect of a steel plate positioned in front of the gateway at a longer distance.
  
• Test B.4: 22 m, Steel plate in front of gateway and sensor: This combined scenario evaluated the cumulative impact of steel plates at both ends.
  
• Test B.5: 22 m, Clear LOS: This provided another clear LOS baseline at a longer indoor distance.
  
• Test B.6: 27 m, Steel plate in front of gateway and sensor, gateway moved to adjacent room: This test introduced a greater distance and physical separation (adjacent room), along with metallic obstructions at both ends.
  
• Test B.7: 27 m, Steel plate in front of gateway and sensor, gateway moved to adjacent room, sensor inside stainless steel enclosure with open side: This further investigated the effect of a partial metallic enclosure around the sensor in a challenging indoor setup.
  
• Test B.8: 27 m, Steel plate in front of gateway and sensor, gateway moved to adjacent room, sensor inside closed stainless steel enclosure: This represented the most challenging indoor scenario, with a fully enclosed sensor within a metallic structure, at a distance and with an intervening room.
  

6. Test Results

The test results, particularly from Test A, demonstrate that LoRaWAN can achieve a range of 9.2 km over open water with clear line of sight. The lab tests (Test B) provide a more granular data on signal attenuation in various obstructed indoor environments, which can be extrapolated to understand signal behavior in complex offshore structures. 

Conclusion: Test Results vs Real World Results

At sea MinFarm has successfully deployed the above equipment with ranges achieved of over 5 km between the LoRaWAN Gateway and LoRaWAN sensor. This distance has been over water but also between rigs where metal has been a physical barrier without any significant impact on data transmission reliability. These real world results are inline with this paper's analysis by MinFarm engineers. 

Note: The findings of this paper were presented at a Tech Meetup presentation by MinFarm Tech and Global Beam Telecom (GBT) on January 30, 2025, in Abu Dhabi, UAE, focusing on offshore LoRaWAN® range testing.