Abstract Gavilan 1W Well was drilled in 1970 by Texas Petroleum, in Colombia, near to border's Ecuador. Final depth 7.700 ft. – 41 API, 1% BSW, Q = 25 BFPD. Well was closed, without conventional abandonment. In 2001, We identified an illegally exploited well with a gas leak from the wellhead (THP= 1.000 psi). Ecopetrol S.A. installed a clamp and control gas leak without exit in well control, in this place there is a permanent presence of guerrilla and there isn't road to arrive the location, we did all operations by Helicopter In 2008, after Colombia Army's Operations, We found a crater near to wellhead, the well was in illegally exploited and the environment contaminated; after many operations with brines (plus sealant material), mud and cement, was possible seal leak's tubing-casing, and closed the crater