I can't answer as to why they have never shared data - A guess might be that why should a private profit generating company, that may or may not be owned by interests in the United States, share any information that they have just spent thousands of dollars in labor and materials to discover ? They are in this for the money, not the Geological Hazards.

They may not want to disclose anything that they have found because it would effect how they may want to use the property and possible oil resources. Also you don't want to give away your info to the competition either.

Methods that are employed by the oil companies are 2d and 3d imaging of the crust without ever having to drill - Oil companies are interested in where oil might be trapped - folds in the earth tend to trap oil as well as faults trap it when it crosses certain material boundaries. So they are looking for just that data that would tell a seismologist where a fault might be.

Oil companies also drill and get core samples - again, they are looking for what kind of soil is down below - sand/sandstones is usually where the oil is trapped - and its formed in Oil shale. So they have all these wonderful Core samples as well.

That's pretty much it in a nutshell... I'm sure there is a lot more to this answer.

Canie