Abstract

Conventional gas detectors are widely used and accepted as the standard gas leak detection throughout the oil and gas industry. This detection method uses technology which requires gas to enter a fixed point gas or pass through the path of a linear detector. As it requires either direct physical contact between the detector sensor and the gas or a disruption of a reflected beam path, it can be unreliable in open areas e.g. due to wind direction, beam block or stratification of the gas. Consequently, there is an increasing use of ultrasonic detection technology to 'listen' for gas leaks. This ultrasonic detection detects releases from pressurized gas systems by sensing the airborne ultrasounds produced by the gas escaping.

Following a significant hydrocarbon gas release in a platform processing area, which the existing detection system had failed to pick up PTTEP, Thailand's major oil and gas exploration and production company, initiated evaluation of the ultrasonic leak detection technology as a method increase risk mitigation and the overall effectiveness of existing fire and gas systems. The field trial of ultrasonic leak detection was done in cooperation with Denmark based Gassonic A/S, the leading manufacturer of fixed ultrasonic gas leak detectors.

The trial result was that the ultrasonic leak detector, the Gassonic Observer, performed well emphasizing its ability to pick up ultrasonic noise in the frequency ranges it is supposed to. Through out the trial period, there were no cases of false alarms. Though no gas release incidents occurred in the vicinity of the detector during the trial period, the detector did detect ultrasonic noise from operations, such as choke valve adjustment or wireline operations. Proper detector settings could reduce such influences from operational sources, and increase release detection viability.

In conclusion, PTTEP will implement ultrasonic gas leak detection as a supplementary gas leak detection system in order to compliment and improve the existing fire and gas system in the Bongkot field.

Introduction

Following a significant number of hydrocarbon gas releases within the main Processing Platform of the Bongkot Field which the existing detection system had failed to detect, PTTEP undertook a thorough review of its fire and gas (F&G) detection system. PTTEP, Thailand's major Exploration and Production Company, performed the review based on risk-based analysis with an overall aim of looking into how to optimize the F&G system to provide increased risk mitigation, ensure early detection and thereby reduce probable incident escalation.

As an important part of this review, PTTEP wanted to test and gain confidence in technologies which could increase gas leak detection efficiency from the F&G detection system. Accordingly, PTTEP decided to evaluate, amongst other options, ultrasonic leak detection technology to possibly increase risk mitigation and the overall effectiveness of the existing F&G systems. A field trial of ultrasonic leak detection was initiated in close cooperation with Gassonic A/S, the leading manufacturer of fixed ultrasonic gas leak detectors, based in Denmark, to determine its operability and reliability in a Gulf of Thailand offshore environment

Conventional Gas Detection - Concentration Based Technologies

Conventional gas detectors are widely used and accepted as the standard gas detection method throughout the oil and gas industry. This detection philosophy uses technology which requires gas to enter a fixed point gas or the path of a linear detector. As it requires either direct physical contact between the detector sensor and the gas or a disruption of a reflected beam, it can be an unreliable method in open or freely ventilated areas due to wind direction, beam block or stratification of the gas, allowing even large releases to go undetected. As an alternative and supplement to this detection philosophy there is currently an increasing use of ultrasonic technology to 'listen' for gas leaks.

This content is only available via PDF.
You can access this article if you purchase or spend a download.