Colombia has shelved two environmental licensing requests made by oil companies ConocoPhillips and Canacol Energy Ltd. for fracking projects in northern Cesar province, two sources with knowledge of the matter said March 20.

Colombia does not yet allow hydraulic fracturing, known as fracking, but the government says use of the technique could nearly triple Colombia’s oil and gas reserves.

An expert commission convened by the government to study non-conventional exploration methods has recommended strict monitoring of three pilot projects to determine whether the techniques should be widely used.

The companies did not meet minimum conditions for the Piranga project, a source from the licensing authority said, while the Plata project raised possible water protection concerns.

U.S.-based ConocoPhillips and Canada’s Canacol can request to re-open the licensing process for the projects in the future, the source said, adding the decision is not a definitive no.

ConocoPhillips had an 80% stake in the projects and Canacol the remaining 20%.

ConocoPhillips said it was reviewing the decision. A source at Canacol said the company was doing the same.

Several other companies, including state-run Ecopetrol , have applied for fracking licenses.

Onshore