Daily Gas Flows (Comments)

Regarding gas flows and storage, I don't know if my reply helps or my experiences are way out-of-date, but in the early 1960's I supervised the annual audit of a large natural gas utility headquartered in West Virginia and operating in Pennsylvania and New York as well. The practice then was to pump Texas gas north during the summer months and store it by injecting it in old gas wells in those areas. As outside auditors, we tested pressure readings on the storage wells to determine whether the amount of gas in storage equalled the company's records. It did not, the differences had been growing over the years and we were asked to find out why. 

Working with the Company's geologists, we found a variety of things were happening, all basically related to the fact that no one really knew all that much about where the gas was actually stored underground, the porosity of the rock, the existence of fault lines, the existence of old, uncapped wells, etc. In one instance, we found that while the rock close to the storage well was quite porous, it became less and less porous as the distance from the well increased. In this instance, the original gas injections were thought to have radiated into this "porosity lens" and would never be economically recoverable. 

In another instance, Texas gas stored in a Company well traveled twenty miles along an unknown fault, to be eventually "produced" by the operator of another gas field entirely! Ownership of the gas was not in dispute after a chemical analysis showed it was not local gas. In several other cases, old uncapped wells were suspected as the culprits, but local records were not adequate to the task of finding all such wells. And there may have been some folks who just drilled their own wells without permits. 

Fast-forward to the present, and I can't help wondering if similar problems exist in measuring the actual capacity of the salt domes and other present-day gas storages. Measuring input and outflow is not difficult, but when you're not absolutely sure of the size of the storage container or whether it might be leaking or expanding, determining how much gas is actually in storage is impossible. In our case ,we finally wrote off a significant amount of gas, and management was not happy!