The drilling history in this area shows many hole instability problems. It was identified overpressure zones, gas influx zones, huge volume of cavings, lost circulation, cut of mud and many stuck pipe incidents. Wellbore instability was responsible for many costly sidetracks, excessive reaming time and in half of the cases well lost. This article will describe the application of the mechanical earth model concept to reduce risks and cost while drilling in Loro field, Putumayo basin in Colombia. Examples are shown comparing the model with actual results and how the model was updated during drilling. The initial earth model represents the best current description of the state of stress, rock strength and geologic structure as a function of depth in the structure of the field. Using the developed MEM, it was forecasted the wellbore stability for the well plan. This forecast predicts regions where the wellbore is expected to be stabile or unstable, where zones might increase the risk of stuck pipe or heavy reaming as well as places where lost circulation should be anticipated. The forecast is used: to evaluate the proposed casing points and to recommend mud weights required drilling a stable well. In cases where the model predicts wellbore instability cannot be controlled by mud weight, specific drilling fluids and drilling practices are recommended to reduce the risk of stuck pipe. It was drilled the planned well without any important instability problem and with record time for the field, a reduction of 58% in drilling days (from 120 to 50 days). The application of the MEM assured the viability of drilling wells in the area. The use of Geomechanics concepts in the planning phase and while drilling in this area helped in reduce the drilling cost and accelerated the learning curve.


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