In September 2017, we began commercial operations of Tubridgi for Citic Pacific Mining. This is located 25km west of Onslow in very close proximity to the Chevron operated Wheatstone gas plant and BHP operated Macedon gas plant, and adjacent to the Ashburton West facilities. Tubridgi is 100% owned and operated by AGIG, and serves all the state’s major gas consumers and producers via a pipeline network that connects Tubridgi to the Dampier Bunbury Natural Gas Pipeline (DBNGP).
The facility stores gas in the depleted Tubridgi Gas Field located onshore within Production Licence L9 area. The Tubridgi Gas Field was discovered in 1981 and produced some 69Bcf (72PJ) of gas before production ceased in October 2004. All gas produced between 1981 and 2004 was treated at the Tubridgi Gas Plant (then called the Griffin export facility or GEF), which comprised equipment for mercury removal, filtration, dehydration, gas compression, slug catchers, pressure regulation, metering and utilities. AGIG acquired the L9 Production License, Tubridgi Gas Field and related Tubridgi gas processing facilities and pipelines from BHP in August 2012.
In 2016, AGIG developed the Tubridgi assets into a storage facility with the capability to store up to 52PJ of gas at injection and withdrawal rates of 50TJ/day. As part of the development project, five wells were drilled in strategically selected locations to allow optimum injection and recovery of gas. All of the wells are of similar design and constructed with a nine and 5/8-inch surface casing and 7-inch production casing. The five wells are interconnected to the Tubridgi Processing Facility via 10km of 6-inch carbon steel flow lines.
At the processing facility, AGIG installed two Ariel JGD6 two-stage reciprocating compressors to provide compression for injection and withdrawal of gas from the reservoir. All gas withdrawn from the reservoir is processed onsite by AGIG to ensure the gas returned to customers meets pipeline specifications. Processing facilities include a combination of refurbished existing facilities and new facilities constructed as part of the development project.
In late 2018, following strong demand in the Western Australian domestic gas market for gas storage, AGIG commenced on an expansion project to increase injection and withdrawal capacity of Tubridgi to 90TJ/day and 60TJ/day respectively. AGIG is also undertaking a seismic survey that uses the latest technology and data processing to produce detailed 3D mapping of the underground reservoir, located approximately 550m below the earth’s surface. The seismic results will help redefine the maximum storage volume for customers and de-risk any additional wells that may be installed in the future. Interim results from the 3D mapping has enabled us to increase storage capacity from 52PJ to 57PJ as we await the final results.
Detailed Engineering and DesignAGIG’s in-house engineering team provided all engineering and design for the Tubridgi development project and the Tubridgi expansion project.
Reservoir engineering: Development of reservoir management strategies, analysis of 2D and 3D seismic information, reservoir modelling, evaluation of the field for gas storage and ensuring the operating envelop provides protection for the wells and reservoirs.
Well engineering: Well design and planning of well integrity assurance activities during the operational phase, planning for well intervention and well workover activities, and establishing criteria to ensure the well remains within the design limits so as to enable well integrity to be maintained.
Facility engineering: AGIG Asset Management Plan (AMP) clearly defines the asset management policies, strategies, processes and plans for maintenance of all physical assets including sub-surface reservoirs, wellhead facilities, flowlines, production facility systems and the associated equipment, infrastructure, machinery, buildings, grounds and communications systems.
Heritage, environmental and land management
AGIG is working closely with the Thalanyji to ensure protection of heritage values in the area and compliance with the Aboriginal Heritage Act 1972. AGIG is progressing the new Heritage Agreement with Thalanyji aimed at providing specific benefits and protections associated with the L9 production area.
AGIG delivered the Tubridgi projects on time and on budget with zero lost time injuries. AGIG’s philosophy of operational excellence has delivered gas storage services with 100% reliability since the facility was commissioned in September 2017.
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