This is an industry document – Halliburton from 1998 – D R I L L I N G CONTRACTOR Nov./Dec. 1998

They have known all along that gas migration occurs and why – that is the functional reason the industry fought so hard to get the exemptions in the 2005 Energy Policy Act

Predicting Potential Gas-Flow Rates to Help Determine the Best Cementing Practices

By Ron Crook and James Heathman, Halliburton Energy Services Inc

Click to Download Report as a PDF

CONCLUSION:  Flow channels created by gas migration cannot be “healed.”

QUOTE:  “Once a flow channel develops, there is no level of gel strength that can cause the channel to heal; the channel is permanent and can be removed only by remedial (squeeze) cementing.”

Download the Halliburton report as a pdf.