In Putumayo basin at south of Colombia is located Loro-Acaé Block in an anticlinal structure lightly folded. Several vertical wells were drilled from 60’s, achieved more than 10 thousand feet; currently, in the new campaign, wells are planned and drilled with high deviation angles (>30°) being a challenge related to wellbore stability in shale rocks of Orteguaza and Villeta formations and wellbore geometry issues in interbedded rocks of Pepino and Rumiyaco formations. Also, gas overpressures are detected in shales and limestones of Villeta formation can overcome 15 ppg increasing the challenge to drill these wells minimizing the risks associates to well kicks, mud cuts, pack offs, stuck pipe and losses. T Sandstone, member of Villeta formation, has the lowest fracture gradient in this formation. Using MW over 14 ppg to control gas and shales stability, a lot of times there were induced fractures in T Sandstone with mud losses and disequilibrium of hydrostatic column become mud cut and gas influx, and then, well control operations. A 3D pore pressure model was developed in Loro-Acaé Block in order to stablish lateral and depth variations in Rumiyaco and Villeta formations. This model is currently being used during well planning to determine risks associated with gas influx, and therefore, establish better well trajectories and adequate mud weight to avoid issues related with gas presence. An attack angle analysis in the well trajectories planning with critical displacements is done as well with the aim of improving the stability of fissile rocks (especially shales). A geomechanics real time monitoring has been done which has allowed avoid and/or mitigate drilling risks related to rock mechanical behaviour: wellbore stability across cavings morphology, rate and size analysis, minimum horizontal stress and fracture initiation gradient as limits of ECD, calculate or change the BHA trip speed, suggested circulation points to well cleaning while tripping, suggested changes in MW according to wellbore stability observed and controlling of casing setting points to isolate formations of different behaviours. The geomechanical analysis plays a fundamental role in this challenge since it allows solving the stress-strain problem in laminated rocks to determine their stability as well as the pore pressure behaviour of the fluids: water, gas and oil. This analysis helps establish the drilling phases, the mud densities to be used and the best well orientation to reach drilling success.

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