No abstract

Drilling in tectonic active areas always faces NPT related to wellbore instability problems, which are very difficult to predict without a clear understanding of the local and regional stresses magnitude and orientation and their impact on any wellbore trajectory. Ecopetrol S.A. has experienced those problems in the Apiay-Suria areas in the Llanos Orientales basin over the last 20 years. In order to optimize the drilling process by eliminating the NPT related to wellbore instability, a 3D geomechanical model was built integrating the geological structural model with all relevant well information such as wireline logging data and drilling reports. Data from more than 40 wells was used to build several 1D individual geomechanical models. To avoid missing local tectonic effects on the stress field, offset wells close to and away from the main faults crossing the fields were selected. To constrain the orientation and magnitude of the in situ stresses, image data was extensively analyzed to pick wellbore failure (breakouts and induced fractures) while drilling. Wireline logging was used as insightful information to calculate overburden, rock strength and to understand the pore pressure generation mechanism. The 3D model was built using formation tops, faults geometry, reservoir pressure and hydraulic fracturing data. By applying geostatistical techniques on the individual wells’ 1D models, a 3D volume of stresses and rock properties was obtained. The comparison of the 3D results with real data measured in a recent well drilled at the edge of the 3D cube showed amazing one-to-one similarity in all the formations from the reservoir to surface. The new drilling campaign has started using the 3D model for wellbore stability analysis and the results are showing that the associated geomechanical risks to drill the wells in the area have been properly addressed, and a much better drilling experience has been obtained, taking out the guesswork from the process.