Explosives, mining services and chemicals supplier Orica has secured an additional 100 petajoules (PJ) of gas from Strike Energy.
Orica said the additional gas would be supplied over 10 years from 2020.
The company said the deal "has been negotiated at competitive prices from Orica's position as a foundation customer" and comes nine months after two companies signed an agreement for up to 150 PJ of natural gas.
"With the signing of today's agreement Orica now has access to up to 250PJ of gas through to the end of 2036," Orica said.
The agreement between Orica and Strike will be used to develop a large gas resource in the Cooper Basin in South Australia.