Leak detection on a CO₂ pipeline

Natural gas from the Gorgon gas field in Western Australia contains around 14% naturally occurring CO₂. Prior to converting the natural gas to LNG by cooling it to -162°C / -259.6°F, the CO₂ is removed. To minimize the environmental footprint, the separated CO₂ is not vented but injected in a storage formation. A 7 km long underground pipeline transports the CO₂ from the LNG liquefaction plant to the CO₂ injection wells.

The CO₂ is transported in supercritical phase at elevated pressures. The underground pipeline has a diameter of 300 mm / 12”. Three compressor modules feed CO₂ in the pipeline that transports it to nine injection wells at three drill centers. The measurement requirement for this project was to provide a pipeline leak detection system that provides timely and accurate leak information for the three pipeline-segments between the LNG plant and drill-centers.

KROHNE provided their PipePatrol E-RTTM based leak detection system. Based on flow, pressure and temperature measurement at inlet and outlet of the pipeline, and a digital twin of the pipeline, PipePatrol calculates the flow, pressure and temperature at any given position in the pipeline, using Real Time Transient Modelling.

In case calculated flow, pressure and temperature start to deviate from actual measured value, a proprietary algorithm developed to avoid false alarms, is used to distinguish between a sensor drift and a true leak. The project involved unique conditions, such as the specific thermophysical properties of CO₂ in the supercritical phase and the flow measurements done by orifice plates with a limited rangeability. Still the minimum detectable leak rate in this project is around 1% with a detection time of less than 15 minutes.

A simulated leak test was done under 3rd party review of Lloyds. The test was carried out by offsetting the reading in the SCADA system by of one of the flowmeters with 10 kg/s, resulting in a swift leak alarm from PipePatrol.

KROHNE’s SynEnergy supervisory software has been used for interfacing with the existing SCADA systems and creation of the leak detection HMIs. Running on a virtual server inside the company network, the HMI screens are accessible from anywhere in the network.

A pipeline leak detection system based on E-RTTM supports the safe management of the CO₂ transport pipeline’s operations. In case of a leak, whether spontaneous or a small creeping leak, PipePatrol will alarm the customer accordingly.