Marcus Jones, route director for Network Rail’s Great Western route said: “We know this incident has caused frustration for customers and we’re grateful for their patience while the necessary safety measures were in place.
“We’d also like to thank SGN and our train operator colleagues for their close collaboration throughout the response.
“While we expect a near-normal service from Thursday, there may still be some short-notice changes as we work to fully restore the timetable, so please check your journey before you travel.”
SGN said the leak in Didcot’s Ladygrove area happened after a third party damaged the gas network.
A spokesperson for SGN said: “We have successfully completed repairs to stop the gas escape, allowing for the exclusion zone affecting the railway line to be lifted.
“We are sorry for the inconvenience during our essential emergency work.”