CHEYENNE, Wyo. (AP) — A new Wyoming State Geological Survey study says certain hydraulic fracturing and directional drilling techniques are the secrets to tapping a previously unprofitable oil deposit.

For decades, geologists thought the Codell Sandstone of southeast Wyoming didn't have enough oil to make drilling worthwhile.

A survey report released Monday says six companies have produced oil from 119 wells targeting the Codell Sandstone over the past five years. The report looked at what the most productive wells have in common.

One is directional drilling — specifically wells drilled in a north-south orientation rather than east-west. Geologists speculate wells directionally drilled north or south intersect with more oil-bearing fissures.

Researchers also say the best wells also have had the most fracking, or use of pressurized water mixed with sand to break open deposits.